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180 Commits

Author SHA1 Message Date
8d5996566e Update licensing and switch back to GPLv3 😅 2025-08-22 11:41:33 -04:00
b2c5a6bf46 macro defines this as BootTarget_cstr_cstr...fix this 2025-01-12 22:24:42 -05:00
531f4fa25f Merge branch 'fat32_sys_rewrite' of github.com:Nivirx/stevia into fat32_sys_rewrite 2025-01-12 20:00:51 -05:00
aa181bbae4 minor edit 2024-12-20 10:22:55 -05:00
ddd3f35a8b inlined ClusterToLBA into ReadFATCluster
fixed a bug where fat32_state wasn't being updated...
2024-12-20 10:10:12 -05:00
ce73226eee update macos build script 2024-12-19 21:31:12 -05:00
d6e8a2a923 minor cleanup and add dev enviroment files to gitignore 2024-12-20 02:07:46 +00:00
9918f2367e Merge upstream changes from branch 'trunk' into fat32_sys_rewrite 2024-12-19 20:09:48 -05:00
56b86fe12e more bug catching after changing the location of data
also cleanup comment from previous bug
2024-12-19 18:59:34 -05:00
37eb87239c moved varibles passed from vbr to .data section
this is to work around having to save them without .bss ready
2024-12-19 15:18:28 -05:00
63a1a1beea might have fixed some of the boot_drive issues with ext_read 2024-12-19 13:13:46 -05:00
3bdef99939 typo 2024-10-19 11:17:09 -04:00
4535b89eaf clarify clobbers 2024-10-19 11:17:04 -04:00
ee9fd9b684 corrected a few instances of accessing boot_drive incorrectly after the location change 2024-10-19 11:08:19 -04:00
6ff9a2307f clear Next cluster data in bss on every NextCluster call 2024-10-19 10:54:58 -04:00
d98786072c use movzx instead of goofy mov word and and mask the upper bits 2024-10-18 07:58:40 -04:00
b7e2a8e886 use bx rel addressing for fat32_state in SearchFATDIR 2024-10-18 07:58:09 -04:00
94c2a1626d correct some field sizes 2024-10-18 07:57:42 -04:00
48f0de8f7b clean up 2024-10-18 07:30:23 -04:00
b606e28958 clean up of comments 2024-10-18 07:30:14 -04:00
45aeb9b3d0 ClusterToLBA to fastcall
cleanup of NextCluster
2024-10-17 20:36:05 -04:00
046821ff7a add fastcall-ish macro for light functions
only does a stack frame setup with no locals space
2024-10-17 20:35:12 -04:00
520f877b05 make space in bss directly for boot_drive and partition offsets 2024-10-17 20:33:44 -04:00
508bf1aa55 update a few missed fields and correct ALIGN on FSInfoPrinter
disable bad cluster jmp for now
2024-10-17 14:34:23 -04:00
ccf846909a update field name 2024-10-17 14:33:42 -04:00
4708c78d54 correction 2024-10-17 14:33:32 -04:00
6942c4dbb4 bit smaller of an instruction 2024-10-17 14:33:22 -04:00
9d4479bd86 clear dh and al 2024-10-17 14:17:15 -04:00
496a389ba4 remove newline and fix stack at end 2024-10-17 14:16:14 -04:00
2b3ab1dc3a changed informational strings 2024-10-17 14:15:49 -04:00
85a8f0da1c rewrite InitFATDriver to use si/di/bx relative addresses 2024-10-17 10:34:32 -04:00
b5cc1c9ec1 move fsinfo just for my easy reading 2024-10-17 10:33:52 -04:00
e12ea89fda changing names of values to match spec more
also added prototype for FS info printer that will print some basic santity check type info.
2024-10-17 07:50:37 -04:00
e33f010f73 added carry and divz checks across the fat32 code
also use the pointers we have in bss to our saved data
2024-10-16 11:58:57 -04:00
c9f4b18d2b some debuging text for fat32 stuff 2024-10-15 20:37:49 -04:00
e680620148 remove some redundant reloads of si
use xchg to swap si/di instead of the stack
uninline ClusterToLBA call
2024-10-15 20:01:24 -04:00
fb54c65caf remove jmp short init at the start of stage2
also correct total size output as combined .data + .text
2024-10-15 18:33:57 -04:00
7f6436297e align to 16 byte bounds and add git info to build 2024-10-15 18:28:06 -04:00
5159ef8a7c correct size of operand in PrintDWORD
added some magic debug points for stuff that isn't working as well.
2024-10-15 13:32:36 -04:00
56e8081118 magic debug before touching anything in error printer 2024-10-15 13:31:51 -04:00
50b08f6b72 turn off magic debug in mbr/vbr stages 2024-10-15 13:31:32 -04:00
a97e3bea9b removed bpb_offset_bx dep
reworked init: process
512 byte stack...should be more than enough for the vbr
2024-10-15 12:57:54 -04:00
aa8c7b67ab moved stack to end of bss & reduced size for now.
removed redzone label
reordered sp/bp setup and bss zeroing in init:
fixed kmemcpy call stack usage
2024-10-15 12:56:12 -04:00
b4621a7fb8 reduced stack size in mbr stage
removed some unused data in bss
reordered how/when in init we set sp/bp and zero bss
we now push the top of the stack pointer/bp at the top of the stack, which makes the stack frame more 'normal'
also use movsb instead of movsw
2024-10-15 12:53:22 -04:00
5f9567d44e include disk signature and reserved bytes in part table struct 2024-10-15 12:51:34 -04:00
2020408e8d ha ha ha, again! 2024-10-15 12:51:02 -04:00
405a5ff20e I guess wx work again on Debian Trixie? 2024-10-15 12:50:51 -04:00
4660882edb change entry points (again) 2024-10-14 17:58:43 -04:00
f683b8fd17 16 KiB stage2 2024-10-14 17:58:30 -04:00
56c18d8457 correct drive_num argument on read_disk_raw 2024-10-14 13:18:41 -04:00
cfda93048b replace text documentation with markdown 2024-10-14 10:44:44 -04:00
c49de28a15 use bochs magic breakpoints in the error printer
makes it easier to get a good state to do some investigating before reseting.
2024-10-13 20:53:13 -04:00
4a013b4a59 enable magic in the normal bochsrc.txt 2024-10-13 20:51:34 -04:00
cd833184da use bx addressing in read_disk_raw 2024-10-13 20:51:16 -04:00
7617b11199 Merge pull request #3 from Nivirx/bss-setup
convert MBR, VBR, & Stage2 to use a BSS section.
2024-10-13 18:05:19 -04:00
86564b2356 added partition_table and fat32_bpb params to stage2
also the partition table and fat32_bpb and passed/copied from the mbr/vbr now
2024-10-13 17:54:06 -04:00
5ba7801926 bss for vbr stage 2024-10-13 17:52:28 -04:00
35e9aec059 fixed bss init in mbr 2024-10-13 17:52:09 -04:00
736aad85e5 pass location of partition_table structure to vbr 2024-10-13 16:41:39 -04:00
f51d8b4142 initial work on a macro to call read_disk_raw 2024-10-13 16:37:52 -04:00
3693eca940 add reserved space for jmp short init at the start, technically this is part of the bpb anyways 2024-10-13 16:37:29 -04:00
a383f7cfb4 remove defs for memory locations (moving to bss) 2024-10-13 16:36:55 -04:00
c1a9d449df bss convertion for mbr stage 2024-10-13 16:36:11 -04:00
ce6240249a turns out huge unreal mode isn't supported in bochs
huge unreal mode is 4GiB code in 16bit mode + 4GiB data
we will just use the regular big flat model instead (64KiB code/4GiB data)
2024-10-13 14:50:49 -04:00
963dec5281 unreal gdt tweaks & fixes 2024-10-13 13:22:01 -04:00
3d1877d7fe remove map files as well 2024-10-12 22:16:17 -04:00
eb97aac673 relocate code sections to end up with stage2 starting at 0x500 2024-10-12 22:14:47 -04:00
c60bad1066 reduced stage2 to 24KiB 2024-10-12 22:13:12 -04:00
050f90517a follow standard proceedure and reallocate the mbr to 0x600 2024-10-12 21:21:43 -04:00
555cf1271b partially roll back changing the segment to 0x07E0 2024-10-12 20:25:04 -04:00
8fea1f0a06 big step...and also its completely broken right now
we are going to use 0x07E0 as our base segment so we have a bit
more memory to work with until we are fully in 32bit protected mode.

this commit is broken but is just one step towards a working release.
2024-10-12 15:41:39 -04:00
b49b2bae68 correct typo 2024-10-12 15:39:16 -04:00
5abbfa4d15 definition corrections in part table stuff 2024-10-12 15:39:04 -04:00
83aa7d1147 use early_mem.inc 2024-10-12 15:38:47 -04:00
ac6ad77249 renamed mem.inc and removed unused items 2024-10-12 15:38:24 -04:00
bc89850c00 first version of kmemcpy5/kmemset4 2024-10-12 14:48:26 -04:00
12fc8a1e37 use NASM defined size value from structure macro 2024-10-12 12:58:32 -04:00
baa146bef5 BIOSMemoryMap is a location in bss now, use lea 2024-10-12 12:58:16 -04:00
d1217182d4 minor cleanup related to memory refactor 2024-10-12 12:57:56 -04:00
5a74cd86ad moved stuff that is only referenced in Stage2 to stage2 bss 2024-10-12 12:55:29 -04:00
69c068f6be stage2 is now a multisection binary file
also preparing to move memory globals to bss section.
2024-10-12 11:29:20 -04:00
63421661a7 output symbol maps to ease debuging 2024-10-12 11:28:25 -04:00
9cde0333e6 remove PRINT_FUNC macro...this isn't it chief 2024-10-12 11:27:55 -04:00
6ff96deabc ignore nasm symbol map files 2024-10-12 11:27:20 -04:00
96de8cd9c7 move far jump setup in EnterUnrealMode to right after we save CS 2024-10-11 21:51:07 -04:00
daa6337285 added debug config for bochs 2024-10-11 21:49:15 -04:00
d73a4eea6c move macro definition super early
fix a few mistakes in macro defs
2024-10-11 19:31:31 -04:00
5703bad704 added macros to define cstr and str
aligned all the entry points for proceedures to 4 bytes
added a PrintString wraper macro
2024-10-11 19:05:15 -04:00
a3f0684c85 added bochs debug wrappers 2024-10-11 19:03:27 -04:00
a8da6eef72 split e820 bios call documentation to its own file under docs/ 2024-10-11 17:20:53 -04:00
d9e46f5571 correct src size in op 2024-10-11 16:52:57 -04:00
0250d9351d inlined ClusterToLBA
removed caller save kludge for now
init first_root_dir_sector from ebpb data
2024-10-11 15:55:24 -04:00
e8fb22c826 somewhat of a cludge, but added a macro to save all caller saved regs 2024-10-11 14:25:01 -04:00
df3b8dfc0c fix passing stage2 wrong data for boot drive 2024-10-11 13:09:17 -04:00
3a819a685a use kmemset to 0 out fat32_state in InitFATDriver 2024-10-11 13:00:45 -04:00
5ccd2fb12f reduce proceedure local storage to 16 bytes 2024-10-11 12:59:36 -04:00
ccb82f29fc rename file to BOOT.BIN
K.I.S.S.
2024-10-11 12:16:01 -04:00
f665d7fcaa more comments to seperate setups 2024-10-11 12:08:09 -04:00
94034eb7bf force 1-1 logical to physical sectors
copy our VBR code to backup VBR
2024-10-11 12:04:44 -04:00
ab21f9c838 more error handling in detecting disk image creation
will need ported to macOS sometime
2024-10-11 11:44:04 -04:00
2f391a0fc2 more error handling for dd writes 2024-10-11 11:31:38 -04:00
d88b1bcb70 use gs for vesa framebuffer (was fs) 2024-10-08 20:23:16 -04:00
13ff42a7d1 unreal gdt now has 2 selectors 1 code, 1 data
ss, and e/f/g segments are loaded to the same flat 4gb segment
moved gdt notes to documentation
2024-10-08 20:22:21 -04:00
61f27cabd7 Update README.md 2024-10-08 09:08:47 -04:00
6643e3c990 ensure 2 byte jmp rel8 thunk to init
surpress reloc abs warnings
corrected include paths/filenames
2024-10-08 08:55:17 -04:00
09d33086a0 converted error handler to a 16bit far jump
optimized the early error printer a bit to save some bytes
removed DEBUG_HCF macro
2024-10-08 08:53:30 -04:00
8e05e071e8 renamed files to show code vs defs
files that actually include code should be in .nasm files
defines/macros/non-code should be in .inc files
2024-10-07 20:41:15 -04:00
ca195e6048 force the first jump to init in all stages to be the rel8 version 2024-10-07 20:39:39 -04:00
db45a5cf8b jmp imm32 vs jmp rel8 (5 bytes vs 2 bytes) 2024-10-06 21:46:32 -04:00
aac964c378 cutting out everything from miniboot
this file has always just been a place holder to get some code to load from the disk
I wanted to cut out all the extra stuff in it just to simplify things down.
2024-10-06 18:52:20 -04:00
3c40190f23 surpress some of the relocation warnings for mbr, vbr & stage2 2024-10-06 18:50:32 -04:00
39e977ea2c make the Linux bochs run more inline with the Windows one 2024-10-06 15:37:19 -04:00
7e0cd2a931 Merge pull request #2 from Nivirx/FAT_Refactor
Full refactor for modularization
2024-10-05 20:19:51 -04:00
4c4c3b0e27 fixed read_disk_raw in ReadFATCluster
boot_drive and partition_offset are global pointers now
removed an extra error from mbr disk read
and some general formating and cleanup 😅
2024-10-05 20:14:00 -04:00
f5f5a330cd tons more work on modularizing the code 2024-10-05 18:55:00 -04:00
446dd451be more modularization and updating date in MIT licence header 2024-10-05 13:35:39 -04:00
64f2453d61 typo fix 2024-10-05 12:16:31 -04:00
867232890e Move fat32 and BIOS functions to their own files 2024-10-05 12:04:40 -04:00
bcb9fc2176 removed extra part probe and added sleep before removing disk
also back to putting the test 32bit mode code on the root of the volume
2024-10-05 10:14:02 -04:00
a0df1cb100 remove the dword stack macros and just use the 32bit override 2024-10-05 10:13:18 -04:00
6b2b1d2fc9 change test kernel stage name
also pointed up a bug in memory.inc
2024-10-04 22:17:35 -04:00
aae0d6b5b3 increased disk size and moved bpb/ebpb a bit 2024-10-04 14:26:10 -04:00
db1d0295c5 some bpb/ebpb tweaks 2024-10-04 11:48:25 -04:00
c1c6b25e6e remove old kmem functions 2024-10-04 09:57:32 -04:00
ecd858f030 vbr cdecl overhaul
refactored read_disk_raw to read_stage2_raw
switched to new kmem functions
2024-10-04 09:56:41 -04:00
e45f1cb27d move cdecl macros to nearly the top so early functions can use them 2024-10-04 09:55:45 -04:00
a6a774484f cdecl16 overhaul for mbr code
switch to cdecl kmem* functions
refactored read_disk_raw to read_vbr_raw
fixed a small issue where the mbr wasn't checking its signature
2024-10-04 09:55:19 -04:00
438b784f2d kmemset and kmemcpy cdecl16 versions 2024-10-04 09:53:01 -04:00
abd8cba080 seperate error code for reading disk in mbr vs vbr vs stage2 2024-10-04 09:52:24 -04:00
d0635f4f3a add macros to prevent __CDECL16 stuff from being defined multiple times 2024-10-04 09:51:44 -04:00
4e7a9e00d7 added isoz stage to make a compressed disk image
also included a work around for a WSL bug in create-disk.sh
2024-10-04 07:57:56 -04:00
e3f0d34336 change FAT partition type to 0Ch from 0Bh (W95 FAT32 LBA was CHS/LBA) 2024-10-03 21:00:49 -04:00
60ad0d71e0 add bpb and ebpb reserve area back to vbr.nasm 2024-10-03 21:00:02 -04:00
d16323bac1 remove this and add it back to vbr.nasm 2024-10-03 20:59:25 -04:00
339216f6a2 add forked functions and remove from memory.inc for kmem* 2024-10-03 19:53:11 -04:00
f8585889f1 forking kmemset functions for stage2 usage 2024-10-03 19:52:24 -04:00
51d77eda6f forking kmemset functions to be updated later for mbr/vbr 2024-10-03 19:52:00 -04:00
91c37df3d0 update some of the dword stack macros 2024-10-03 19:33:07 -04:00
e03322b129 rough pass on fixing the stack across the board 2024-10-03 19:02:47 -04:00
7fbb9b13e2 swap order of entering Unreal mode and getting an E820
also InitFATDriver should be ok to add to the start process again.
2024-10-03 18:15:18 -04:00
3f72d5ad31 move E820 function desc to memory.inc 2024-10-03 18:14:04 -04:00
09366afbdf cdecl16 update for EnterUnrealMode 2024-10-03 17:59:29 -04:00
269e90a122 refactored and validated MemoryMap funciton 2024-10-03 17:41:48 -04:00
768260540f some general cleanup & moving the halt to the next point in main() 2024-10-03 16:43:10 -04:00
d2194ab835 cdecl16 work and cleanup in MemoryMap 2024-10-03 16:34:27 -04:00
94ed76be82 src/stage2/stage2.nasm:573: warning: label alone on a line without a colon might be in error [-w+label-orphan] 2024-10-03 15:28:44 -04:00
9080533175 cdecl16 for EnableA20 ver.1 2024-10-03 15:10:22 -04:00
a3af2a5825 replace prologs and epilogs in cdecl functions so far 2024-10-03 14:51:43 -04:00
0c36f9f1fd added entry & exit macros 2024-10-03 14:46:47 -04:00
3804f1c4be bunch of changes mostly to do with cdecl16 conformity
moved top of stack marker to init
SetTextMode and Cursor done before hello msg
corrected CC/Stack usage to conform with cdecl16 for PrintString
corrected CC/Stack usage to conform with cdecl16 for PrintChar
corrected stack usage to conform with cdecl16 for SetTextMode
corrected stack usage to conform with cdecl16 for disable_cursor
2024-10-03 13:49:44 -04:00
a6835df63e fixing how the stack works stage1 😳 2024-10-02 12:37:21 -04:00
18bb9a5691 remove comment about CC, see docs/ 2024-10-02 11:59:34 -04:00
cbd7244e87 load our base headers in the same order as the mbr 2024-10-02 10:26:36 -04:00
f3de54fa9d moved reservation for bpb to a include 2024-10-02 10:25:59 -04:00
e057dbdbe3 added some clarification on cdecl16 2024-10-02 10:13:45 -04:00
b654e900ed removed ata1 from windows bochsrc 2024-10-02 10:13:00 -04:00
d813b03de9 added bxrc config to launch on windows hosts 2024-09-21 14:09:52 -04:00
8a3b12774f small optimization to error printer
saves us 5 bytes of code (15 overall)
2024-09-21 13:45:15 -04:00
60a10e41e0 added debuging 'errors'
also there is special handling for them in error.inc
2024-09-21 13:28:52 -04:00
20c18ac4ec partially revert change, sti is still in init 2024-09-21 12:32:49 -04:00
e859f5da13 added -P option to losetup
this fixes an issue that appeared on WSL2 recently(ish)
2024-09-21 12:04:05 -04:00
2a1b0f3b09 ignore vscode personal configs 2024-09-21 11:46:36 -04:00
ee65b6acc5 remove reallocation in mbr init
also reenable interupts in the init block
2024-09-21 11:45:22 -04:00
dafac41102 Update README.md
updated description to more accurately reflect project status
2024-07-27 09:21:41 -04:00
9cb9a6664f changed extention from .s to .nasm 2023-08-23 10:10:30 -04:00
bd47648ad0 enable logging and bump to 128MB of memory 2023-08-23 10:10:13 -04:00
7b3ed7e1de updated gitignore 2023-08-23 10:09:49 -04:00
333b176793 clarify that WSL is supported 2023-08-23 07:35:30 -04:00
4b0e0abd9b added description for create-disk script 2023-08-22 16:45:22 -04:00
bd1492593b Update README.md 2023-08-22 16:34:39 -04:00
0868cf41cc update readme with more information 2023-08-22 16:22:13 -04:00
d7bd565279 MIT license applied to all project files 2023-08-22 16:03:46 -04:00
bb6d943047 use wx interface for config, gui, and debug 2023-08-22 15:56:15 -04:00
df8c959bb4 remove packaged binaries 2023-08-22 15:55:45 -04:00
91ec2ad898 small changes to License
🏳️‍⚧️
2023-08-22 14:24:35 -04:00
ad192db2a6 Update README.md 2023-08-22 10:43:54 -04:00
1a1b7a279d Delete COPYING
Removing GPL-3.0 license.
2023-08-22 10:43:01 -04:00
e78074e190 Create README.md 2023-08-22 10:36:35 -04:00
Elaina Claus
4a37274e58 Merge pull request #1 from Xinnx/add-license-1
Create LICENSE.md
2023-02-28 22:24:40 -05:00
Elaina Claus
967a13de7e Create LICENSE.md 2023-02-28 22:24:32 -05:00
43 changed files with 2944 additions and 2748 deletions

5
.gitignore vendored
View File

@@ -1,5 +1,10 @@
out/*
build/*
*.img
*.img.gz
*.elf
bx_enh_dbg.ini
stevia-log
.vscode/
*.map
compose-dev.yaml

2
COPYING Executable file → Normal file
View File

@@ -1,4 +1,4 @@
GNU GENERAL PUBLIC LICENSE
GNU GENERAL PUBLIC LICENSE
Version 3, 29 June 2007
Copyright (C) 2007 Free Software Foundation, Inc. <https://fsf.org/>

14
LICENSE.md Normal file
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@@ -0,0 +1,14 @@
Copyright (C) 2025 Elaina Claus
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>.

View File

@@ -1,31 +1,54 @@
iso := 'disk.img'
# Copyright (C) 2025 Elaina Claus
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <https://www.gnu.org/licenses/>.
include := './include'
mbr_source_files := $(wildcard src/mbr/*.s)
vbr_source_files := $(wildcard src/vbr/*.s)
stage2_source_files := $(wildcard src/stage2/*.s)
boottest_source_files := $(wildcard src/miniboot32/*.s)
mbr_source_files := $(wildcard src/mbr/*.nasm)
vbr_source_files := $(wildcard src/vbr/*.nasm)
stage2_source_files := $(wildcard src/stage2/*.nasm)
boottest_source_files := $(wildcard src/miniboot32/*.nasm)
mbr_binary_files := $(patsubst src/mbr/%.s, build/%.bin, $(mbr_source_files))
vbr_binary_files := $(patsubst src/vbr/%.s, build/%.bin, $(vbr_source_files))
stage2_binary_files := $(patsubst src/stage2/%.s, build/%.bin, $(stage2_source_files))
boottest_binary_files := $(patsubst src/miniboot32/%.s, build/%.bin, $(boottest_source_files))
mbr_binary_files := $(patsubst src/mbr/%.nasm, build/%.bin, $(mbr_source_files))
vbr_binary_files := $(patsubst src/vbr/%.nasm, build/%.bin, $(vbr_source_files))
stage2_binary_files := $(patsubst src/stage2/%.nasm, build/%.bin, $(stage2_source_files))
boottest_binary_files := $(patsubst src/miniboot32/%.nasm, build/%.bin, $(boottest_source_files))
build_dir := 'build'
qemu_args := -L ./bin/ -bios bios.bin -cpu pentium3 -m 64 -S -s -monitor stdio -nic none
.PHONY: all mbr vbr stage2 boottest clean run run_bochs iso
# Get current Git version (tag) and hash
GIT_VERSION := $(shell git describe --tags)
GIT_HASH := $(shell git rev-parse HEAD)
GIT_NASM_DEFINES := -D __GIT_VER__='"$(GIT_VERSION)"' -D __GIT_HASH__='"$(GIT_HASH)"'
all: $(iso) $(mbr_binary_files) $(vbr_binary_files) $(stage2_binary_files)
iso := '/tmp/disk.img'
isoz := 'disk.img.gz'
qemu_args := -L ./bin/ -bios bios.bin -cpu pentium3 -m 128 -S -s -monitor stdio -nic none
.PHONY: all mbr vbr stage2 boottest clean run run_bochs iso isoz
all: $(iso) $(isoz) $(mbr_binary_files) $(vbr_binary_files) $(stage2_binary_files)
mbr: $(mbr_binary_files)
vbr: $(vbr_binary_files)
stage2: $(stage2_binary_files)
boottest: $(boottest_binary_files)
clean:
@rm -rvf *.map
@rm -rvf $(build_dir)/*
@rm -rvf $(iso)
@rm -rvf $(isoz)
run: $(iso)
@sudo qemu-system-i386 $(qemu_args) -hda $(iso)
@@ -34,25 +57,30 @@ run_bochs: $(iso)
@bochs -q
iso: $(iso)
@file disk.img
@file $(iso)
build/%.bin: src/mbr/%.s
@mkdir -p $(shell dirname $@)
@nasm -i$(include) -Wall -f bin $< -o $@
isoz: $(isoz)
@file $(isoz)
build/%.bin: src/vbr/%.s
build/%.bin: src/mbr/%.nasm
@mkdir -p $(shell dirname $@)
@nasm -i$(include) -Wall -f bin $< -o $@
@nasm -i$(include) -Wall -f bin $(GIT_NASM_DEFINES) $< -o $@
build/%.bin: src/stage2/%.s
build/%.bin: src/vbr/%.nasm
@mkdir -p $(shell dirname $@)
@nasm -i$(include) -Wall -f bin $< -o $@
@nasm -i$(include) -Wall -f bin $(GIT_NASM_DEFINES) $< -o $@
build/%.bin: src/miniboot32/%.s
build/%.bin: src/stage2/%.nasm
@mkdir -p $(shell dirname $@)
@nasm -i$(include) -Wall -f bin $< -o $@
@nasm -i$(include) -Wall -f bin $(GIT_NASM_DEFINES) $< -o $@
build/%.bin: src/miniboot32/%.nasm
@mkdir -p $(shell dirname $@)
@nasm -i$(include) -Wall -f bin $(GIT_NASM_DEFINES) $< -o $@
$(iso): $(mbr_binary_files) $(vbr_binary_files) $(stage2_binary_files) $(boottest_binary_files)
@echo root access needed to create disk image...
@sudo scripts/create-disk.sh
$(isoz): $(iso)
@gzip -9kc $(iso) > $(isoz)

70
README.md Normal file
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@@ -0,0 +1,70 @@
# Stevia Bootloader
Stevia is a lightweight, hobby bootloader written in Assembly and C, designed for educational purposes. It targets x86 (Pentium III era) and aims to be simple, approachable, and understandable, focusing on minimalism and core functionality.
## Features
### Currently Implemented
- **Stage 1 Bootloader**: Loads from the Master Boot Record (MBR) and prepares the system for Stage 2.
- **Stage 2 Bootloader**: Loads the kernel into memory and passes control.
- **Basic Filesystem Support**: Initial filesystem recognition (details depend on implemented filesystem support).
- **Memory Map Parsing**: Detects available memory regions via BIOS interrupts.
- **GDT Initialization**: Sets up the Global Descriptor Table for protected mode.
### In Progress
- **Interrupt Descriptor Table (IDT) Setup**: Setting up basic interrupt handling.
- **Basic Keyboard Input**: Initial support for capturing keystrokes.
### Planned Features
- **Task Scheduling**: Basic round-robin task switching.
- **Filesystem Expansion**: Support for additional filesystems.
- **More Robust Driver Support**: Additional hardware drivers, such as for storage devices.
## Installation
### Prerequisites
To build and run Stevia, you will need the following tools installed on your system:
- **Assembler**: NASM for assembling bootloader components.
- **C Compiler**: GCC (cross-compiler recommended).
- **Emulator**: Bochs or QEMU for testing.
- **GNU Make**: For building the project.
- **Utilities**:
- **dd**: For creating raw disk images.
- **losetup** (Linux only): For associating loop devices with disk images.
- **sfdisk**: For creating DOS disk partitions.
- **mkfs.fat**: For formatting partitions as FAT32.
- **hdiutil** (macOS only): For attaching disk images.
- **newfs\_msdos** (macOS only): For formatting FAT32 partitions.
### Building and Running
1. **Clone the repository**:
```sh
git clone https://github.com/Nivirx/stevia.git
cd stevia
```
2. **Build the bootloader and create a bootable disk image**:
```sh
sudo make
```
3. **Run using Bochs**:
```sh
bochs -f bochsrc.txt
```
## Project Goals
Stevia is intended to be a learning tool for those interested in low-level programming, focusing on understanding the basics of how a computer starts up and manages early system resources. Contributions and forks are welcome, especially from those interested in expanding the functionality.
## Contributing
We welcome contributions! Feel free to open issues for bugs or feature requests, and submit pull requests for any improvements. Please ensure that your code follows the existing style and includes appropriate comments.
## License
This project is licensed under the MIT License. See the [LICENSE](LICENSE) file for more details.

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52
bochsrc.bxrc Normal file
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@@ -0,0 +1,52 @@
# configuration file generated by Bochs
plugin_ctrl: voodoo=false, unmapped=true, biosdev=true, speaker=true, extfpuirq=true, parallel=true, serial=true, busmouse=false, e1000=false, es1370=false, gameport=true, iodebug=true, ne2k=false, sb16=false, usb_uhci=false, usb_ohci=false, usb_ehci=false, usb_xhci=false
config_interface: win32config
display_library: win32
memory: guest=64, host=64, block_size=128
romimage: file="C:\Program Files\Bochs-2.8\BIOS-bochs-legacy", address=0x00000000, options=none, flash_data=none
vgaromimage: file="C:\Program Files\Bochs-2.8\VGABIOS-lgpl-latest"
boot: disk
floppy_bootsig_check: disabled=1
floppya: type=1_44
# no floppyb
ata0: enabled=true, ioaddr1=0x1f0, ioaddr2=0x3f0, irq=14
ata0-master: type=disk, path=".\disk.img", mode=flat, cylinders=0, heads=16, spt=63, sect_size=512, model="Stevia Disk", biosdetect=auto, translation=auto
ata0-slave: type=none
ata1: enabled=false
ata2: enabled=false
ata3: enabled=false
optromimage1: file=none
optromimage2: file=none
optromimage3: file=none
optromimage4: file=none
optramimage1: file=none
optramimage2: file=none
optramimage3: file=none
optramimage4: file=none
pci: enabled=1, chipset=i440fx, slot1=none, slot2=none, slot3=none, slot4=none, slot5=none
vga: extension=vbe, update_freq=10, realtime=1, ddc=builtin
cpu: count=1, ips=1000000, model=p3_katmai, reset_on_triple_fault=1, cpuid_limit_winnt=0, ignore_bad_msrs=1, mwait_is_nop=0
print_timestamps: enabled=0
debugger_log: -
magic_break: enabled=1
port_e9_hack: enabled=true, all_rings=false
iodebug: all_rings=0
private_colormap: enabled=0
clock: sync=none, time0=local, rtc_sync=0
# no cmosimage
log: -
logprefix: %t%e%d
debug: action=ignore
info: action=report
error: action=report
panic: action=ask
keyboard: type=mf, serial_delay=150, paste_delay=100000, user_shortcut=none
mouse: type=none, enabled=false, toggle=ctrl+mbutton
sound: waveoutdrv=dummy, waveout=none, waveindrv=dummy, wavein=none, midioutdrv=dummy, midiout=none
speaker: enabled=true, mode=sound, volume=15
parport1: enabled=false
parport2: enabled=false
com1: enabled=false
com2: enabled=false
com3: enabled=false
com4: enabled=false

53
bochsrc.dbg.txt Executable file
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@@ -0,0 +1,53 @@
# configuration file generated by Bochs
plugin_ctrl: voodoo=false, unmapped=true, biosdev=true, speaker=true, extfpuirq=true, parallel=true, serial=true, busmouse=false, e1000=false, es1370=false, gameport=true, ne2k=false, sb16=false, usb_uhci=false, usb_ohci=false, usb_ehci=false, usb_xhci=false
config_interface: textconfig
display_library: sdl2, options=gui_debug
memory: guest=64, host=64, block_size=128
romimage: file="/usr/share/bochs/BIOS-bochs-legacy", address=0x00000000, options=none, flash_data=none
vgaromimage: file="/usr/share/bochs/VGABIOS-lgpl-latest"
boot: disk
floppy_bootsig_check: disabled=0
floppya: type=1_44
# no floppyb
ata0: enabled=true, ioaddr1=0x1f0, ioaddr2=0x3f0, irq=14
ata0-master: type=disk, path="./disk.img", mode=flat, cylinders=0, heads=0, spt=0, sect_size=512, model="Stevia Disk", biosdetect=auto, translation=auto
ata0-slave: type=none
ata1: enabled=false
ata1-master: type=none
ata1-slave: type=none
ata2: enabled=false
ata3: enabled=false
optromimage1: file=none
optromimage2: file=none
optromimage3: file=none
optromimage4: file=none
optramimage1: file=none
optramimage2: file=none
optramimage3: file=none
optramimage4: file=none
pci: enabled=1, chipset=i440fx, slot1=none, slot2=none, slot3=none, slot4=none, slot5=none
vga: extension=vbe, update_freq=10, realtime=1, ddc=builtin
cpu: count=1, ips=1000000, model=p3_katmai, reset_on_triple_fault=0, cpuid_limit_winnt=0, ignore_bad_msrs=1, mwait_is_nop=0
print_timestamps: enabled=0
private_colormap: enabled=0
clock: sync=none, time0=local, rtc_sync=0
# no cmosimage
log: stevia-log
#logcontrol: disk=1, rombios=1, pci=0, cpu=0, keyboard=0, io=0
logprefix: %t%e%d
debug: action=ignore
info: action=report
error: action=report
panic: action=ask
keyboard: type=mf, serial_delay=150, paste_delay=100000, user_shortcut=none
mouse: type=none, enabled=false, toggle=ctrl+mbutton
sound: waveoutdrv=dummy, waveout=none, waveindrv=dummy, wavein=none, midioutdrv=dummy, midiout=none
speaker: enabled=true, mode=sound, volume=15
parport1: enabled=true, file=none
parport2: enabled=false
com1: enabled=true, mode=null
com2: enabled=false
com3: enabled=false
com4: enabled=false
magic_break: enabled=1
port_e9_hack: enabled=1, all_rings=false

View File

@@ -1,25 +1,35 @@
# configuration file generated by Bochs
plugin_ctrl: unmapped=true, biosdev=true, speaker=true, extfpuirq=true, parallel=true, serial=true, gameport=true, iodebug=true
plugin_ctrl: voodoo=false, unmapped=true, biosdev=true, speaker=true, extfpuirq=true, parallel=true, serial=true, busmouse=false, e1000=false, es1370=false, gameport=true, ne2k=false, sb16=false, usb_uhci=false, usb_ohci=false, usb_ehci=false, usb_xhci=false
config_interface: textconfig
display_library: x
memory: host=32, guest=32
display_library: wx
memory: guest=64, host=64, block_size=128
romimage: file="/usr/share/bochs/BIOS-bochs-legacy", address=0x00000000, options=none, flash_data=none
vgaromimage: file="/usr/share/bochs/VGABIOS-lgpl-latest"
boot: disk
floppy_bootsig_check: disabled=0
# no floppya
floppya: type=1_44
# no floppyb
ata0: enabled=true, ioaddr1=0x1f0, ioaddr2=0x3f0, irq=14
ata0-master: type=disk, path="disk.img", mode=flat, cylinders=0, heads=0, spt=0, sect_size=512, model="Generic 1234", biosdetect=auto, translation=auto
ata0-master: type=disk, path="./disk.img", mode=flat, cylinders=0, heads=0, spt=0, sect_size=512, model="Stevia Disk", biosdetect=auto, translation=lba
ata0-slave: type=none
ata1: enabled=false
ata1-master: type=none
ata1-slave: type=none
ata2: enabled=false
ata3: enabled=false
pci: enabled=1, chipset=i440fx
vga: extension=vbe, update_freq=5, realtime=1
cpu: count=1:1:1, ips=1000000, quantum=16, model=p3_katmai, reset_on_triple_fault=1, cpuid_limit_winnt=0, ignore_bad_msrs=1, mwait_is_nop=0
optromimage1: file=none
optromimage2: file=none
optromimage3: file=none
optromimage4: file=none
optramimage1: file=none
optramimage2: file=none
optramimage3: file=none
optramimage4: file=none
pci: enabled=1, chipset=i440fx, slot1=none, slot2=none, slot3=none, slot4=none, slot5=none
vga: extension=vbe, update_freq=10, realtime=1, ddc=builtin
cpu: count=1, ips=1000000, model=p3_katmai, reset_on_triple_fault=1, cpuid_limit_winnt=0, ignore_bad_msrs=1, mwait_is_nop=0
print_timestamps: enabled=0
debugger_log: -
magic_break: enabled=0
port_e9_hack: enabled=0
port_e9_hack: enabled=false, all_rings=false
private_colormap: enabled=0
clock: sync=none, time0=local, rtc_sync=0
# no cmosimage
@@ -29,12 +39,15 @@ debug: action=ignore
info: action=report
error: action=report
panic: action=ask
keyboard: type=mf, serial_delay=250, paste_delay=100000, user_shortcut=none
mouse: type=ps2, enabled=false, toggle=ctrl+mbutton
speaker: enabled=true, mode=system
keyboard: type=mf, serial_delay=150, paste_delay=100000, user_shortcut=none
mouse: type=none, enabled=false, toggle=ctrl+mbutton
sound: waveoutdrv=dummy, waveout=none, waveindrv=dummy, wavein=none, midioutdrv=dummy, midiout=none
speaker: enabled=true, mode=sound, volume=15
parport1: enabled=true, file=none
parport2: enabled=false
com1: enabled=true, mode=null
com2: enabled=false
com3: enabled=false
com4: enabled=false
magic_break: enabled=1
port_e9_hack: enabled=1, all_rings=false

230
docs/Stevia Notes.md Normal file
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@@ -0,0 +1,230 @@
# **Bootloader Documentation**
## **1. Calling Conventions**
### __cdecl16near Calling Convention
- **Purpose**: For calling near (within the same segment) functions in 16-bit code.
- **Stack Management**: Caller cleans up the stack after the function call.
- **Parameter Passing**: Parameters are pushed onto the stack from right to left.
- **Return Address**: A near return address (16-bit) is pushed onto the stack.
- **Return Value**: Placed in the AX register.
Example:
```assembly
; Caller
push param2
push param1
call near_func
add sp, 4 ; Clean up the stack (2 parameters * 2 bytes each)
; Callee (near_func)
near_func:
push bp
mov bp, sp
; Function body
mov sp, bp
pop bp
ret
```
### __cdecl16far Calling Convention
- **Purpose**: For calling far (across different segments) functions in 16-bit code.
- **Stack Management**: Caller cleans up the stack after the function call.
- **Parameter Passing**: Parameters are pushed onto the stack from right to left.
- **Return Address**: A far return address (32-bit, consisting of a segment and an offset) is pushed onto the stack.
- **Return Value**: Placed in the AX register.
Example:
```assembly
; Caller
push param2
push param1
call far_func
add sp, 4 ; Clean up the stack (2 parameters * 2 bytes each)
; Callee (far_func)
far_func:
push bp
mov bp, sp
; Function body
mov sp, bp
pop bp
retf ; Far return
```
### **Key Differences**
- **Return Address**: `__cdecl16near` uses a 16-bit return address; `__cdecl16far` uses a 32-bit return address (segment:offset).
- **Function Scope**: `__cdecl16near` is for functions within the same segment; `__cdecl16far` is for functions that may be in different segments.
- **Return Instruction**: `__cdecl16near` uses `ret`; `__cdecl16far` uses `retf` (far return).
### **Register Usage**
#### Caller-Saved (Volatile) Registers
- **AX**: Accumulator, often used for return values.
- **CX**: Counter register.
- **DX**: Data register, used for I/O operations.
- **SI/DI**: String operation indexes.
#### Callee-Saved (Non-Volatile) Registers
- **BP**: Base pointer, used for stack frame management.
- **SP**: Stack pointer.
- **BX**: Base register.
Example:
```assembly
; Caller
push param2
push param1
call near_func
add sp, 4 ; Clean up the stack (2 parameters * 2 bytes each)
; Callee (near_func)
near_func:
push bp
mov bp, sp
; Save callee-saved registers if used
push bx
push si
push di
; Function body
; Use AX, CX, DX freely
; Restore callee-saved registers
pop di
pop si
pop bx
mov sp, bp
pop bp
ret
```
## **2. E820 Memory Map Usage**
### **Address Range Descriptor Structure**
| Offset | Name | Description |
|--------|---------------|---------------------------------------|
| 0 | BaseAddrLow | Low 32 bits of base address |
| 4 | BaseAddrHigh | High 32 bits of base address |
| 8 | LengthLow | Low 32 bits of length in bytes |
| 12 | LengthHigh | High 32 bits of length in bytes |
| 16 | Type | Address type of this range |
### **E820 Function Call**
#### Input
- **EAX**: Function code `E820h`.
- **EBX**: Continuation value for physical memory retrieval (0 for the first call).
- **ES:DI**: Buffer pointer to an Address Range Descriptor structure.
- **ECX**: Buffer size (minimum size 20 bytes).
- **EDX**: Signature ('SMAP').
#### Output
- **CF**: Carry flag (indicates success/failure).
- **EAX**: Signature ('SMAP').
- **ECX**: Buffer size (number of bytes returned).
- **EBX**: Continuation value for subsequent E820 calls.
### **Address Type Values**
| Value | Pneumonic | Description |
|-------|----------------------|-----------------------------------------------------------|
| 1 | AddressRangeMemory | Available RAM usable by the operating system. |
| 2 | AddressRangeReserved | Reserved by the system, unusable by the operating system. |
## **3. Example Calculations**
### **Partition Offset**
- Partition 1 offset = LBA 0x800 = 0x100000
- `bsSectorSize = 512`
### **First FAT Sector**
- `first_fat_sector = bsResSector = 32 => (32*512) = 0x4000`
- `first_fat_sector = 0x100000 + 0x4000 = 0x104000`
### **Total FAT Sectors**
- `total_fat_sectors = fat_sectors * number_of_FATs = 2001 * 2 = 4002`
- `total_fat_size = total_fat_sectors * bsSectorSize = 0x1F4400`
### **First Data Sector**
- `first_data_sector = FatStartSector + FatAreaSize = 0x104000 + 0x1F4400 = 0x2F8400`
### **FAT Table Look Up**
```c
if the cluster we got from the table entry was cluster 354
fat_sector = 354 / 128 = 2
fat_entry = 354 mod 128 = 98
so we load the 3rd (indexed from 0) fat table sector and read the 98th entry
```
Example:
```c
fat_table_offset = (first_fat_sector + 2) * 512
fat_table = *(fat_table_offset)
disk_read(fat_table[98])
```
## **4. Global Descriptor Table (GDT)**
### **Segment Attributes**
- **Pr**: Present bit (must be 1 for valid selectors).
- **Privl**: Privilege level (0 = kernel, 3 = user).
- **S**: Descriptor type (set for code/data segments, cleared for system segments).
- **Ex**: Executable bit (set if segment contains code).
- **DC**: Direction/Conforming bit (for data or code segments).
- **RW**: Readable/Writable (depends on segment type).
### **Granularity (Gr)**
- **Gr**: Granularity bit (0 = byte granularity, 1 = 4 KiB blocks).
- **Sz**: Size bit (0 = 16-bit mode, 1 = 32-bit mode).
### **GDT Entry Construction**
Each GDT entry is 8 bytes:
- First DWORD: Limit (0:15), Base (0:15)
- Second DWORD: Base (16:31), Attributes (8:12)
## **5. Memory Layout Example**
### **Low Memory (First MiB)**
| Start | End | Size | Type | Description |
|-------------|-------------|-----------------|-----------------------|----------------------------------|
| 0x00000000 | 0x000003FF | 1 KiB | RAM (partially unusable) | Real Mode IVT (Interrupt Vector Table) |
| 0x00000400 | 0x000004FF | 256 bytes | RAM (partially unusable) | BDA (BIOS data area) |
| 0x00000500 | 0x00007BFF | almost 30 KiB | RAM - free for use | Conventional memory |
| 0x00007C00 | 0x00007DFF | 512 bytes | RAM (partially unusable) | OS BootSector |
| 0x00007E00 | 0x0007FFFF | 480.5 KiB | RAM - free for use | Conventional memory |
| 0x00080000 | 0x0009FFFF | 128 KiB | RAM (partially unusable) | EBDA (Extended BIOS Data Area) |
| 0x000A0000 | 0x000FFFFF | 384 KiB | various (unusable) | Video memory, ROM Area |
### **Extended Memory (Above 1 MiB)**
| Start | End | Size | Description |
|-------------|-------------|-----------------|------------------------|
| 0x00100000 | 0x00EFFFFF | 14 MiB | RAM - free for use |
| 0x00F00000 | 0x00FFFFFF | 1 MiB | Possible memory-mapped hardware (ISA) |
| 0x01000000 | ? | ? | More extended memory |
| 0xC0000000 | 0xFFFFFFFF | 1 GiB | Memory mapped PCI devices, BIOS, etc. |
| 0x0000000100000000 | ? | ? | RAM - usable in PAE/64-bit mode |

View File

@@ -1,35 +0,0 @@
Partition 1 offset = LBA 0x800
= 0x100000
bsSectorSize = 512
first_fat_sector = bsResSector
= 32 => (32*512) = 0x4000
= 0x100000 + 0x4000
= 0x104000
total_fat_sectors = fat_sectors * number_of_FATs
= 2001 * 2
= 4002
total_fat_size = total_fat_sectors * bsSectorSize
= 0x1F4400
first_data_sector = FatStartSector + FatAreaSize
= 0x104000 + 0x1F4400
= 0x2F8400
FAT table look up
if the cluster we got from the table entry was cluster 354
fat_sector = 354 / 128
= 2
fat_entry = 354 mod 128
= 98
so we load the 3rd (indexed from 0) fat table sector and read the 98th entry
for the cluster chain.
// bad fake code below
fat_table_offset = (first_fat_sector + 2) * 512
fat_table = *(fat_table_offset)
disk_read(fat_table[98])

19
include/BIOS/BIOS_SYS.inc Normal file
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@@ -0,0 +1,19 @@
; Copyright (C) 2025 Elaina Claus
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
%include 'BIOS/func/a20enable.nasm'
%include 'BIOS/func/E820_memory_map.nasm'
%include 'BIOS/func/ext_read.nasm'
%include 'BIOS/func/video.nasm'

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@@ -0,0 +1,83 @@
; Copyright (C) 2025 Elaina Claus
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
%ifndef __INC_E820MEMORY_MAP
; Address Range Descriptor Structure
;
; Offset in Bytes Name Description
; 0 BaseAddrLow u32 - Low 32 Bits of Base Address
; 4 BaseAddrHigh u32 - High 32 Bits of Base Address
; 8 LengthLow u32 - Low 32 Bits of Length in Bytes
; 12 LengthHigh u32 - High 32 Bits of Length in Bytes
; 16 Type u32 - Address type of this range.
; 20 ExtType u32 - ACPI 3.0 extended type
struc AddressRangeDescStruct_t
.BaseAddrLow resd 1
.BaseAddrHigh resd 1
.LengthLow resd 1
.LengthHigh resd 1
.Type resd 1
.ExtType resd 1
endstruc
ALIGN 4, db 0x90
GetMemoryMap:
__CDECL16_ENTRY
push es ; save segment register
.func:
mov dword [SteviaInfo + SteviaInfoStruct_t.MemoryMapEntries], 0
mov eax, 0xE820 ; select 0xE820 function
xor ebx, ebx ; Continuation value, 0 for the first call
lea dx, [BIOSMemoryMap]
shr dx, 4
mov es, dx
xor di, di ; (BIOSMemoryMap >> 4):0 makes di an index into BIOSMemoryMap
mov ecx, AddressRangeDescStruct_t_size
mov edx, 0x534D4150 ; 'SMAP' magic
.loop_L1:
int 0x15
jc GetMemoryMap.error
cmp eax, 0x534D4150
jne GetMemoryMap.no_smap_returned
.no_error:
inc dword [SteviaInfo + SteviaInfoStruct_t.MemoryMapEntries]
cmp ecx, 20 ; TODO: maybe this could be handled better than just panicing
jb GetMemoryMap.nonstandard_e820 ; non-standard entry found
cmp ebx, 0
je GetMemoryMap.endp ; 0 in ebx means we have reached the end of memory ranges
add di, AddressRangeDescStruct_t_size ; increment di to next descriptor
mov edx, eax ; 'SMAP' to edx
mov eax, 0xE820 ; select E820 function
jmp GetMemoryMap.loop_L1
.error:
ERROR STAGE2_MM_E820_MISC_ERR
.nonstandard_e820:
ERROR STAGE2_MM_E820_NONSTANDARD
.no_smap_returned:
ERROR STAGE2_MM_E820_NO_SMAP
.endp:
pop es
__CDECL16_EXIT
ret
%endif
%define __INC_E820MEMORY_MAP

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@@ -0,0 +1,139 @@
; Copyright (C) 2025 Elaina Claus
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
%ifndef __INC_A20ENABLE
;
;INT 0x15 Function 2400 - Disable A20
;Returns:
;
; CF = clear if success
; AH = 0
; CF = set on error
; AH = status (01=keyboard controller is in secure mode, 0x86=function not supported)
;
;INT 0x15 Function 2401 - Enable A20
;Returns:
;
; CF = clear if success
; AH = 0
; CF = set on error
; AH = status (01=keyboard controller is in secure mode, 0x86=function not supported)
;
;INT 0x15 Function 2402 - A20 Status
; Returns:
;
; CF = clear if success
; AH = status (01: keyboard controller is in secure mode; 0x86: function not supported)
; AL = current state (00: disabled, 01: enabled)
; CX = set to 0xffff is keyboard controller is no ready in 0xc000 read attempts
; CF = set on error
;
;INT 0x15 Function 2403 - Query A20 support
;Returns:
;
;CF = clear if success
;AH = status (01: keyboard controller is in secure mode; 0x86: function not supported)
;BX = status.
;
;BX contains a bit pattern:
;
; Bit 0 - supported on keyboard controller
; Bit 1 - if supported on bit 1 of I/O port 0x92
; Bits 2:14 - Reserved
; Bit 15 - 1 if additional data is available.
;
; I/O Port 0x92 infomation:
;
; Bit 0 - Setting to 1 causes a fast reset
; Bit 1 - 0: disable A20; 1: enable A20
; Bit 2 - Manufacturer defined
; Bit 3 - power on password bytes (CMOS bytes 0x38-0x3f or 0x36-0x3f). 0: accessible, 1: inaccessible
; Bits 4-5 - Manufacturer defined
; Bits 6-7 - 00: HDD activity LED off; any other value is "on"
ALIGN 4, db 0x90
EnableA20:
__CDECL16_ENTRY
push ds
push es
.a20_check:
cli
xor ax, ax
mov es, ax
not ax ; ax = 0xFFFF
mov ds, ax
mov di, 0x0500 ; scratch location 1
mov si, 0x0510 ; scratch location 2
mov al, byte [es:di]
push ax ; save whatever is at 0x0000:0500, physical location 0x0500
mov al, byte [ds:si]
push ax ; save whatever is at 0xFFFF:0510 [clarification: 0x100500 physical location (0x100500 - 1MB = 0x0500)]
mov byte [es:di], 0x00 ; zero non-wraped location and write 0xFF to it after (ab)using wrapping
mov byte [ds:si], 0xFF ; if the non-wrapped location is 0xFF, then we wraped and A20 is disabled
cmp byte [es:di], 0xFF
pop ax
mov byte [ds:si], al ; restore original contents of scratch location 2
pop ax
mov byte [es:di], al ; restore original contents of scratch location 1
mov ax, 0 ; return 0 if es:di == ds:si (memory wraps)
je EnableA20.end_check
mov ax, 1 ; return 1 if es:di != ds:si (A20 is enabled)
.end_check:
sti
cmp ax, 1
je EnableA20.endp ; A20 is already enabled
mov ax, 0x2403
int 0x15
jc EnableA20.do_fallback_a20 ; carry = error...not supported?
cmp ah, 0
ja EnableA20.do_fallback_a20 ; non-zero return = error as well
mov al, bl
and al, 0000_0010b
cmp al, 0000_0010b
je EnableA20.do_fast_a20 ; if fast a20 is supported use it
jmp EnableA20.do_bios_a20 ; else fall back to enabling via BIOS
.do_fallback_a20:
ERROR STAGE2_A20_FAILED
.do_bios_a20:
mov ax, 0x2401
int 0x15
jmp EnableA20.a20_check
.do_fast_a20:
in al, 0x92 ; read from FAST A20 port
or al, 2 ; bit 0 is a fast reset, bit 1 is fast A20
and al, 0xFE ; make sure bit 0 is 0
out 0x92, al ; enable A20
jmp EnableA20.a20_check
.endp:
pop es
pop ds
__CDECL16_EXIT
ret
%endif
%define __INC_A20ENABLE

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@@ -0,0 +1,129 @@
; Copyright (C) 2025 Elaina Claus
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
%ifndef __INC_EXT_READ
;Offset Size Description
; 0 1 size of packet (16 bytes)
; 1 1 always 0
; 2 2 number of sectors to transfer (max 127 on some BIOSes)
; 4 4 transfer buffer (0xFFFF:0xFFFF)
; 8 4 lower 32-bits of starting 48-bit LBA
; 12 4 upper 32-bits of starting 48-bit LBA
; needs to be aligned to a uint32_t
struc LBAPkt_t
.size resb 1
.res0 resb 1
.xfer_size resw 1
.offset resw 1
.segment resw 1
.lower_lba resd 1
.upper_lba resd 1
endstruc
; call_read_disk_raw <word segment> <word offset> <dword lba> <word count> <word drive_num>
%macro call_read_disk_raw 5
movzx ax, %5
push ax ; drive_num
movzx ax, %4
push ax ; count
movzx dword eax, %3
push dword eax ; lba
movzx ax, %2
push ax ; offset
movzx ax, %1
push ax ; segment = 0
; uint8_t read_stage2_raw(uint16_t buf_segment, uint16_t buf_offset,
; uint32_t lba,
; uint16_t count, uint16_t drive_num)
call read_disk_raw
add sp, 0xC
%endmacro
; Wrapper for AH=0x42 INT13h (Extended Read)
;
; BIOS call details
; AH = 42h
; DL = drive number
; DS:SI -> disk address packet
;
; Return:
; CF clear if successful
; AH = 00h
; CF set on error
; AH = error code
; disk address packet's block count field set to number of blocks
; successfully transferred
;
;
; uint8_t read_stage2_raw(uint16_t buf_segment, uint16_t buf_offset,
; uint32_t lba,
; uint16_t count, uint8_t drive_num)
ALIGN 4, db 0x90
read_disk_raw:
__CDECL16_ENTRY
.func:
mov ax, LBAPkt_t_size
push ax ; len
xor ax, ax
push ax ; val = 0
mov ax, lba_packet
push ax ; dest = lba_packet address
call kmemset
add sp, 0x06
mov bx, lba_packet
mov byte [bx + LBAPkt_t.size], LBAPkt_t_size
mov ax, [bp + 12]
mov word [bx + LBAPkt_t.xfer_size], ax
mov eax, dword [bp + 8]
mov dword [bx + LBAPkt_t.lower_lba], eax
; upper_lba is zero from kmemset
; TODO: possiblly support >32bit LBA addresses in the future, this limits us to 4GiB
mov ax, [bp + 6]
mov word [bx + LBAPkt_t.offset], ax
mov ax, [bp + 4]
mov word [bx + LBAPkt_t.segment], ax
xor ax, ax
xor dx, dx
mov si, bx ; ds:si LBAPkt_t
mov ah, 0x42 ; call #
mov dl, byte [bp + 14] ; drive #
int 0x13
jnc .endf
%ifdef __STEVIA_MBR
ERROR MBR_ERROR_DISK_READ_ERR
%elifdef __STEVIA_VBR
ERROR VBR_ERROR_DISK_READ_ERR
%else
ERROR STAGE2_MBR_DISK_READ_ERROR
%endif
.endf:
__CDECL16_EXIT
ret
%endif
%define __INC_EXT_READ

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@@ -0,0 +1,55 @@
; Copyright (C) 2025 Elaina Claus
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
%ifndef __INC_VIDEO
; Sets output to 80x25 16 color text mode via BIOS call
; also clears screen
; void SetTextMode(void)
ALIGN 4, db 0x90
SetTextMode:
.prolog:
__CDECL16_ENTRY
pushf
.func:
xor ah, ah ; Set Video mode BIOS function
mov al, 0x02 ; 16 color 80x25 Text mode
int 0x10 ; Call video interrupt
mov ah, 0x05 ; Select active display page BIOS function
xor al, al ; page 0
int 0x10 ; call video interrupt
.endp:
popf
__CDECL16_EXIT
ret
; disables blinking text mode cursor
ALIGN 4, db 0x90
disable_cursor:
__CDECL16_ENTRY
.func:
mov dx, 0x3D4
mov al, 0xA ; low cursor shape register
out dx, al
inc dx
mov al, 0x20 ; bits 6-7 unused, bit 5 disables the cursor, bits 0-4 control the cursor shape
out dx, al
.endp:
__CDECL16_EXIT
ret
%endif
%define __INC_VIDEO

67
include/cdecl16.inc Normal file
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@@ -0,0 +1,67 @@
; Copyright (C) 2025 Elaina Claus
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
%ifnmacro __CDECL16_ENTRY
%macro __CDECL16_ENTRY 0
push bp
mov bp, sp
sub sp, 0x10
push si
push di
push bx
%endmacro
%endif
%ifnmacro __CDECL16_EXIT
%macro __CDECL16_EXIT 0
pop bx
pop di
pop si
mov sp, bp
pop bp
%endmacro
%endif
%ifnmacro __CDECL16_CALLER_SAVE
%macro __CDECL16_CALLER_SAVE 0
push ax
push cx
push dx
%endmacro
%endif
%ifnmacro __CDECL16_CALLER_RESTORE
%macro __CDECL16_CALLER_RESTORE 0
pop dx
pop cx
pop ax
%endmacro
%endif
%ifnmacro __FASTCALL16_ENTRY
%macro __FASTCALL16_ENTRY 0
push bp
mov bp, sp
%endmacro
%endif
%ifnmacro __FASTCALL16_EXIT
%macro __FASTCALL16_EXIT 0
mov sp, bp
pop bp
%endmacro
%endif

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@@ -1,20 +1,24 @@
; Copyright (C) 2020 Bradley Claus
; Copyright (C) 2025 Elaina Claus
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
%ifndef __INC_STEVIA_CONFIG
%define SECTOR_SIZE 512
%define STAGE2_SECTOR_COUNT 0x40
; 32 KiB
%define STAGE2_SECTOR_COUNT 0x20
; 16 KiB
%define MAX_STAGE2_BYTES (SECTOR_SIZE * STAGE2_SECTOR_COUNT)
%endif
%define __INC_STEVIA_CONFIG

28
include/early_mem.inc Executable file
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@@ -0,0 +1,28 @@
; Copyright (C) 2025 Elaina Claus
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
%ifndef __INC_EARLY_MEM
;PhysicalAddress = Segment * 16 + Offset
%define SEG_TO_LINEAR(s,o) ((s << 4) + o)
; Offset = physical / (Segment * 16)
%define LINEAR_TO_OFFSET(p,s) ((p / (s << 4)))
; Seg = (physical - offset) / 16
%define LINEAR_TO_SEGMENT(p,o) ((p - o) >> 4)
%endif
%define __INC_EARLY_MEM

View File

@@ -1,21 +1,23 @@
; Copyright (C) 2020 Bradley Claus
; Copyright (C) 2025 Elaina Claus
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
%ifndef __INC_ENTRY
; 8KiB from 0x2500 -> 0x500
%define STACK_START 0x2500
%define MBR_ENTRY 0x7A00
%define VBR_ENTRY 0x7C00
%define STAGE2_ENTRY 0x7E00
%define MBR_ENTRY 0x8C00
%define VBR_ENTRY 0x7C00
%define STAGE2_ENTRY 0x0500
%endif
%define __INC_ENTRY

View File

@@ -1,18 +1,19 @@
; Copyright (C) 2020 Bradley Claus
; Copyright (C) 2025 Elaina Claus
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
%ifndef __INC_ERROR_CODES
; Errors
; 12 Errors, 5 in use
@@ -27,7 +28,7 @@
%define MBR_ERROR_RESERVED_i 'i'
%define MBR_ERROR_RESERVED_j 'j'
%define MBR_ERROR_RESERVED_k 'k'
%define MBR_ERROR_RESERVED_l 'l'
%define MBR_ERROR_INT13h_EREAD_ERR 'l'
; 12 Error
%define VBR_ERROR_WRONG_FAT_SIZE 'm'
@@ -43,7 +44,7 @@
%define VBR_ERROR_RESERVED_w 'w'
%define VBR_ERROR_RESERVED_x 'x'
; 26 errors, 8 in use
; 22 errors, 8 in use
%define STAGE2_A20_FAILED 'A'
%define STAGE2_SIGNATURE_MISSING 'B'
%define STAGE2_MM_E820_NO_SUPPORT 'C'
@@ -54,10 +55,10 @@
%define STAGE2_FAT32_INIT_ERROR 'H'
%define STAGE2_FAT32_NO_FILE 'I'
%define STAGE2_FAT32_END_OF_CHAIN 'J'
%define STAGE2_ERROR_RESERVED_K 'K'
%define STAGE2_ERROR_RESERVED_L 'L'
%define STAGE2_ERROR_RESERVED_M 'M'
%define STAGE2_ERROR_RESERVED_N 'N'
%define STAGE2_FAT32_NCLUS_CFDIVZ 'K'
%define STAGE2_FAT32_CLS2LBA_CF 'L'
%define STAGE2_FAT32_INIT_CF 'M'
%define STAGE2_ERROR_INFOPRINTER 'N'
%define STAGE2_ERROR_RESERVED_O 'O'
%define STAGE2_ERROR_RESERVED_P 'P'
%define STAGE2_ERROR_RESERVED_Q 'Q'
@@ -66,30 +67,12 @@
%define STAGE2_ERROR_RESERVED_T 'T'
%define STAGE2_ERROR_RESERVED_U 'U'
%define STAGE2_ERROR_RESERVED_V 'V'
%define STAGE2_ERROR_RESERVED_W 'W'
%define STAGE2_ERROR_RESERVED_X 'X'
%define STAGE2_ERROR_RESERVED_Y 'Y'
%define STAGE2_ERROR_RESERVED_Z 'Z'
; for development only, specific errors should be above.
%define STEVIA_DEBUG_OK 'W'
%define STEVIA_DEBUG_ERR 'X'
%define STEVIA_DEBUG_UNIMPLEMENTED 'Y'
%define STEVIA_DEBUG_HALT 'Z'
%macro ERROR 1
mov al, %1
jmp error
%endmacro
; pass error as ascii character in al, errors a-zA-Z or 0-9
error:
; color 0x4F is white on red
; fs = 0xb800 => fs:0x0000 = 0xb8000
mov dx, 0xB800
mov fs, dx
; the characters are two bytes in the order of 0xb8000: byte c, byte attribute
; since x86 is le, we store the attribute in the MSB of dx
mov dh, 0x4F
mov dl, al
mov word [fs:0x0000], dx
.stop:
hlt
jmp short error.stop
%endif
%define __INC_ERROR_CODES

327
include/fat32/FAT32_SYS.inc Normal file
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@@ -0,0 +1,327 @@
; Copyright (C) 2025 Elaina Claus
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
%ifndef __INC_FAT32_SYS
%include "partition_table.inc"
%include "fat32/bpb_offset_bx.inc"
%include "fat32/fat32_structures.inc"
; Clobbers: eax, edx
; returns: none
ALIGN 4, db 0x90
InitFATDriver:
__CDECL16_ENTRY
.func:
mov ax, FAT32_State_t_size
push ax ; length of fat32_state structure
xor ax, ax
push ax ; init fat32_state with zero
mov ax, fat32_state
push ax ; address of structure
call kmemset
sub sp, 0x6
.calc_active_part:
mov ax, word [partition_offset]
mov di, fat32_state
mov dx, partition_table
add dx, ax ; dx points to the partition that was booted from
mov bx, dx ; set bx, should point at our partition
mov eax, dword [bx + PartEntry_t.lba_start]
mov dword [di + FAT32_State_t.curr_drive_lba_32], eax
mov si, fat32_bpb
mov bx, fat32_ebpb
.calc_first_fat:
movzx eax, word [si + FAT32_bpb_t.reserved_sectors_word] ; first fat from start of partition
add eax, dword [di + FAT32_State_t.curr_drive_lba_32] ; calculate offset from start of drive
jc InitFATDriver.error
mov dword [di + FAT32_State_t.first_fat_sector_32], eax
.calc_total_fat:
mov edx, dword [bx + FAT32_ebpb_t.FATSz_dword]
movzx eax, byte [si + FAT32_bpb_t.fat_count_byte]
mul edx ; result in EDX:EAX, CF set on > 32bit return value
jc InitFATDriver.error ; as a catch for unhandled overflow, just error if value is greater than 32bits
mov dword [di + FAT32_State_t.fat_size_32], eax
.calc_first_data:
mov edx, dword [di + FAT32_State_t.first_fat_sector_32]
add eax, edx
jc InitFATDriver.error
mov dword [di + FAT32_State_t.first_data_sector_32], eax
.set_first_dir:
mov eax, dword [bx + FAT32_ebpb_t.root_clus_dword]
mov dword [di + FAT32_State_t.curr_dir_cluster_32], eax
.endp:
__CDECL16_EXIT
ret
.error:
ERROR STAGE2_FAT32_INIT_CF
ALIGN 4, db 0x90
FSInfoPrinter:
__CDECL16_ENTRY
.func:
;info we want to print to validate we are loading stuff from the disk correctly
; boot_drive # (i.e 0x80)
; active/bootable partition info (lba_start, lba_length, part_type)
; BPB Info: BS_OEMName = ident_8, BPB_BytsPerSec = bytes_per_sector_16, BPB_SecPerClus = sectors_per_cluster_8
; eBPB info: FATSz_dword, volid, vol label
;
; print entire FAT32 state
;
.endp:
__CDECL16_EXIT
ret
.error:
ERROR STAGE2_ERROR_INFOPRINTER
; this involves using the low memory buffer for the bios call and moving the file sector by sector to high memory
;
; SFN is a 8.3 file name, all uppercase, and padded with spaces
; do not add a null byte to the end of the string
; eg. kernel.bin == "KERNEL BIN"
;
; returns first cluster of file if found
; halts/errors if file is not found
; uint32_t SearchFATDIR(uint8_t* SFN);
ALIGN 4, db 0x90
SearchFATDIR:
__CDECL16_ENTRY
.file_lookup:
print_string SearchFATDIR_info
mov bx, fat32_state
.load_first_dir:
mov eax, dword [bx + FAT32_State_t.curr_dir_cluster_32]
push dword eax ; cluster
mov ax, dir_buffer
push ax ; offset
xor ax, ax
push ax ; segment
call ReadFATCluster ; uint8_t ReadFATCluster(uint16_t seg, uint16_t offset, uint32_t cluster)
add sp, 0x8
mov si, dir_buffer
jmp SearchFATDIR.empty_dir_entry
.load_next_dir:
; if eax >= 0x0FFFFFF8 then there are no more clusters (end of chain)
; if eax == 0x0FFFFFF7 then this is a cluster that is marked as bad
mov eax, dword [bx + FAT32_State_t.curr_dir_cluster_32]
push dword eax
call NextCluster ; uint32_t NextCluster(uint32_t active_cluster);
add sp, 0x4
cmp eax, 0x0fff_fff7
;je SearchFATDIR.bad_cluster ; TODO: Implement Bad cluster checks
jb SearchFATDIR.load_next_dir_next_OK
ERROR STAGE2_FAT32_END_OF_CHAIN
.load_next_dir_next_OK:
; load 512 bytes of directory entries from data sector
mov eax, [bx + FAT32_State_t.curr_dir_cluster_32]
push dword eax ; cluster
mov ax, dir_buffer
push ax ; offset
xor ax, ax
push ax ; segment
call ReadFATCluster ; uint8_t ReadFATCluster(uint16_t seg, uint16_t offset, uint32_t cluster)
sub sp, 0x8
.empty_dir_entry:
; check for 0x0 in first byte, if true then there are no more files
; if true we did not find the file, we should error here
cmp byte [si], 0
jne SearchFATDIR.unused_dir_entry
ERROR STAGE2_FAT32_NO_FILE
.unused_dir_entry:
; check for 0xe5 and 0x05 in first byte, if true then this entry is unused, but it is not the last entry.
cmp byte [si], 0xe5
je SearchFATDIR.next_entry
cmp byte [si], 0x05
je SearchFATDIR.next_entry
jmp SearchFATDIR.parse_dir
.next_entry:
; increment offset by 32 bytes to read the next entry in this set of dir entries
; if we are at the end of the buffer, then load the next buffer
add si, 0x20 ; 32 bytes
mov ax, dir_buffer
add ax, 0x1FF ; 512 - 1 bytes
cmp si, ax
jae SearchFATDIR.load_next_dir
jmp SearchFATDIR.empty_dir_entry
; TODO: move this to a seperate string search function
.parse_dir:
print_string MaybeFound_Boot_info
.lfn_check:
; check for ATTR_READ_ONLY | ATTR_HIDDEN | ATTR_SYSTEM | ATTR_VOLUME_ID (0x0F) in offset 11
; TODO: going to skip LFN for now, since all valid volumes will have SFN's
cmp byte [si+11], 0x0F
je SearchFATDIR.next_entry
.sfn_file_name_check:
push si
push di
mov cx, 0xA ; max of 11 filename length of 11 characters
; si points to the start of the current directory entry
mov di, BootTarget ; current memory location (8.3 name is at offset 0)
repe cmpsb ; compare the strings
pop di
pop si
jne SearchFATDIR.next_entry
.sfn_entry_found:
mov ax, [si + FAT32_SFN_t.cluster_16_high]
shl eax, 16
mov ax, [si + FAT32_SFN_t.cluster_16_low]
; eax == first cluster of file
.endp:
__CDECL16_EXIT
ret
; BUG: this function needs review
; uint32_t NextCluster(uint32_t active_cluster);
; if eax >= 0x0FFFFFF8 then there are no more clusters (end of chain)
; if eax == 0x0FFFFFF7 then this is a cluster that is marked as bad
ALIGN 4, db 0x90
NextCluster:
__CDECL16_ENTRY
.func:
print_string NextFATCluster_info
mov ax, FAT32_NextClusterData_t_size
push ax ; length
xor ax, ax
push ax ; init with zero
mov ax, fat32_nc_data
push ax ; address of structure
call kmemset
sub sp, 0x6
mov edx, dword [bp + 4]
mov si, fat32_nc_data ; instead of push/pop and moving the data back
mov di, fat32_bpb ; load si & di then use xchg
mov bx, fat32_state
.calc_offset:
; fat_offset = active_cluster * 4
mov eax, 4
mul edx
jc NextCluster.error_cfdivz
mov dword [si + FAT32_NextClusterData_t.fat_offset], eax ; move lower 32 bits to fat offset
.calc_fat_sector:
; fat_sector = first_fat_sector + (fat_offset / sector_size)
; entry_offset = fat_offset % sector_size
xor edx, edx
movzx ecx, word [di + FAT32_bpb_t.bytes_per_sector_word]
cmp eax, 0
je NextCluster.error_cfdivz
div ecx ; eDX:eAX / eCX = fat_sector - first_fat_sector in eAX
; eDX = remainder (fat_offset mod sector_size)
mov dword [si + FAT32_NextClusterData_t.entry_offset], edx
mov ecx, dword [bx + FAT32_State_t.first_fat_sector_32]
add eax, ecx ; fat_sector + first_fat_sector
mov dword [si + FAT32_NextClusterData_t.fat_sector], eax
.load_fat_table:
xor ax, ax
mov al, byte [boot_drive]
push ax
mov ax, 0x1
push ax
; load correct fat
mov eax, dword [si + FAT32_NextClusterData_t.fat_sector]
push dword eax
mov ax, fat_buffer
push ax
xor ax, ax
push ax
call read_disk_raw
add sp, 0xC
; uint8_t read_stage2_raw(uint16_t buf_segment, uint16_t buf_offset,
; uint32_t lba,
; uint16_t count, uint16_t drive_num)
.read_cluster:
; next_cluster = fat_buffer[entry_offset]
mov ebx, dword [si + FAT32_NextClusterData_t.entry_offset]
mov si, fat_buffer
mov eax, dword [bx+si+0]
.endp:
__CDECL16_EXIT
ret
.error_cfdivz:
ERROR STAGE2_FAT32_NCLUS_CFDIVZ
; uint8_t ReadFATCluster(uint16_t seg, uint16_t offset, uint32_t cluster)
ALIGN 4, db 0x90
ReadFATCluster:
__CDECL16_ENTRY
.func:
print_string ReadFATCluster_info
mov bx, fat32_bpb
mov si, fat32_ebpb
xor ax, ax
mov al, byte [boot_drive]
push ax
mov ax, 0x1 ; count = 1
push ax
mov eax, dword [bp + 8] ; cluster
sub eax, 2
movzx edx, byte [bx + FAT32_bpb_t.sectors_per_cluster_byte]
mul edx ; result in eax, error on carry
jc ReadFATCluster.error
add eax, dword [si + FAT32_State_t.first_data_sector_32]
jc ReadFATCluster.error
; eax contains the LBA now
push dword eax ; lba = ClusterToLBA(..)
mov ax, word [bp + 6] ; offset
push ax
mov ax, word [bp + 4]
push ax
; uint8_t read_disk_raw(uint16_t buf_segment, uint16_t buf_offset,
; uint32_t lba,
; uint16_t count, uint16_t drive_num)
call read_disk_raw
add sp, 0xC
.endp:
__CDECL16_EXIT
ret
.error:
ERROR STAGE2_FAT32_CLS2LBA_CF
%endif
%define __INC_FAT32_SYS

View File

@@ -1,18 +1,19 @@
; Copyright (C) 2020 Bradley Claus
; Copyright (C) 2025 Elaina Claus
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
%ifndef __INC_BPD_OFFSET_BX
; BPB Information
; Off. Hex Off. Size Description
@@ -84,3 +85,6 @@
%define bsVolumeLabel bx+0x47
%define bsSystemIdent bx+0x52
;-- End EBPB
%endif
%define __INC_BPD_OFFSET_BX

View File

@@ -1,18 +1,19 @@
; Copyright (C) 2020 Bradley Claus
; Copyright (C) 2025 Elaina Claus
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
%ifndef __INC_FAT32_STRUCT
; ## FAT32 Info ##
; total_sectors = bsSectorsHuge
@@ -57,19 +58,20 @@
; resulting in a value which does not fit in the Number of Sectors entry at 0x13.
struc FAT32_bpb_t
.ident_8 resb 8
.bytes_per_sector_16 resb 2
.sectors_per_cluster_8 resb 1
.reserved_sectors_16 resb 2
.fat_count_8 resb 1
.dir_entry_count_16 resb 2
.sector_count_16 resb 2
.media_desc_8 resb 1
.sectors_per_fat_16 resb 2
.sectors_per_track_16 resb 2
.head_count_16 resb 2
.hidden_sectors_32 resb 4
.sector_count_32 resb 4
.reserved_jmpboot resb 3
.ident resb 8
.bytes_per_sector_word resb 2
.sectors_per_cluster_byte resb 1
.reserved_sectors_word resb 2
.fat_count_byte resb 1
.unused1_ZERO_word resb 2 ; Root entry count field, 0 on fat32
.unused2_ZERO_word resb 2 ; total sectors size 16, 0 on fat32
.media_desc_byte resb 1
.unused3_ZERO_word resb 2 ; FAT size 16, 0 on fat32
.sectors_per_track_word resb 2
.head_count_word resb 2
.hidden_sectors_dword resb 4
.total_sectors_dword resb 4
endstruc
; EBPB Information (FAT32)
@@ -89,19 +91,19 @@ endstruc
; 8 System identifier string. Always "FAT32 ". The spec says never to trust the contents of this string for any use.
struc FAT32_ebpb_t
.sectors_per_fat_32 resb 4
.fat32_flags_16 resb 2
.fat32_version_16 resb 2
.root_dir_cluster_32 resb 4
.fsinfo_sector_16 resb 2
.backup_boot_sector_16 resb 2
.reserved1 resb 12
.drive_number_8 resb 1
.nt_flags_8 resb 1
.signature_8 resb 1
.volume_serial_32 resb 4
.volume_label resb 11
.system_ident resb 8
.FATSz_dword resb 4
.extflags_word resb 2
.FSVersion_word resb 2
.root_clus_dword resb 4
.FSInfo_word resb 2
.BkBootSec_word resb 2
.reserved1 resb 12
.drive_number_byte resb 1
.nt_flags_byte resb 1
.signature_byte resb 1
.volume_id_dword resb 4
.volume_label_bytea resb 11
.system_ident_bytea resb 8
endstruc
; ## Standard 8.3 structure ###
@@ -127,19 +129,43 @@ endstruc
; 26 2 Low 16 bits of entry's first cluster
; 28 4 File size in bytes
; FSInfo
; 0 0x0 4 Lead signature (must be 0x41615252 to indicate a valid FSInfo structure)
; 4 0x4 480 Reserved, these bytes should never be used
; 484 0x1E4 4 Another signature (must be 0x61417272)
; 488 0x1E8 4 Contains the last known free cluster count on the volume. If the value is 0xFFFFFFFF, then the free count is unknown and must be computed.
; However, this value might be incorrect and should at least be range checked (<= volume cluster count)
;
; 492 0x1EC 4 Indicates the cluster number at which the filesystem driver should start looking for available clusters.
; If the value is 0xFFFFFFFF, then there is no hint and the driver should start searching at 2.
; Typically this value is set to the last allocated cluster number. As the previous field, this value should be range checked.
;
; 496 0x1F0 12 Reserved
; 508 0x1FC 4 Trail signature (0xAA550000)
struc FAT32_FSInfo_t
.head_sig_dword resd 1 ; 0x41615252
.reserved1 resb 480 ; fill zero
.body_sig_dword resd 1 ; 0x61417272
.free_count_dword resd 1
.next_free_dword resd 1
.reserved2 resb 12 ; fill zero
.tail_sig_dword resd 1 ; 0xAA550000
endstruc
struc FAT32_SFN_t
.label resb 11
.attributes_8 resb 1
.nt_res_8 resb 1
.csec_8 resb 1
.ctime_16 resb 2
.cdate_16 resb 2
.adate_16 resb 2
.cluster_16_high resb 2
.mtime_16 resb 2
.mdate_16 resb 2
.cluster_16_low resb 2
.size_32 resb 4
.label_83 resb 11
.attributes_byte resb 1
.nt_res_byte resb 1
.csec_byte resb 1
.ctime_word resb 2
.cdate_word resb 2
.adate_word resb 2
.cluster_16_high resb 2
.mtime_word resb 2
.mdate_word resb 2
.cluster_16_low resb 2
.size_dword resb 4
endstruc
; ## Long file name (LFN) structure format ##
@@ -159,51 +185,24 @@ endstruc
; Max of 20 in sequence == 0x14
struc FAT32_LFN_t
.order resb 1
.lfn_first5 resb 10
.attributes_8 resb 1
.zero1 resb 1
.checksum resb 1
.lfn_next6 resb 12
.zero2 resb 2
.lfn_last2 resb 4
.order resb 1
.lfn_first5 resb 10
.attributes_8 resb 1
.zero1 resb 1
.checksum resb 1
.lfn_next6 resb 12
.zero2 resb 2
.lfn_last2 resb 4
endstruc
; FSInfo
; 0 0x0 4 Lead signature (must be 0x41615252 to indicate a valid FSInfo structure)
; 4 0x4 480 Reserved, these bytes should never be used
; 484 0x1E4 4 Another signature (must be 0x61417272)
; 488 0x1E8 4 Contains the last known free cluster count on the volume. If the value is 0xFFFFFFFF, then the free count is unknown and must be computed.
; However, this value might be incorrect and should at least be range checked (<= volume cluster count)
;
; 492 0x1EC 4 Indicates the cluster number at which the filesystem driver should start looking for available clusters.
; If the value is 0xFFFFFFFF, then there is no hint and the driver should start searching at 2.
; Typically this value is set to the last allocated cluster number. As the previous field, this value should be range checked.
;
; 496 0x1F0 12 Reserved
; 508 0x1FC 4 Trail signature (0xAA550000)
struc FAT32_FSInfo_t
.head_signature_32 resd 1
.reserved1 resb 480
.body_signature_32 resd 1
.free_cluster_count_32 resd 1
.first_avail_cluster_32 resd 1
.reserved2 resd 3
.tail_signature_32 resd 1
endstruc
; 32 bytes
struc FAT32_State_t
.first_root_dir_sector_32 resd 1
.first_data_sector_32 resd 1
.first_fat_sector_32 resd 1
.fat_size_32 resd 1
.active_cluster_32 resd 1
.active_FAT_cluster_32 resd 1
.active_dir_cluster_32 resd 1
.active_drive_lba_32 resd 1
.curr_FAT_cluster_32 resd 1
.curr_dir_cluster_32 resd 1
.curr_drive_lba_32 resd 1
endstruc
; 16 bytes
@@ -225,4 +224,5 @@ endstruc
; LFN == RO | HIDDEN | SYSTEM | VOLID == 0x0F
%define FAT32_ATTR_LFN 0x0F
%endif
%define __INC_FAT32_STRUCT

View File

@@ -1,208 +0,0 @@
; Copyright (C) 2020 Bradley Claus
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
; ## Generic Low mem map (from osdev wiki) ##
; start end size type description
; Low Memory (the first MiB)
; 0x00000000 0x000003FF 1 KiB RAM - partially unusable Real Mode IVT (Interrupt Vector Table)
; 0x00000400 0x000004FF 256 bytes RAM - partially unusable BDA (BIOS data area)
; 0x00000500 0x00007BFF almost 30 KiB RAM - free for use Conventional memory
; 0x00007C00 0x00007DFF 512 bytes RAM - partially unusable OS BootSector
; 0x00007E00 0x0007FFFF 480.5 KiB RAM - free for use Conventional memory
; 0x00080000 0x0009FFFF 128 KiB RAM - partially unusable EBDA (Extended BIOS Data Area)
; 0x000A0000 0x000FFFFF 384 KiB various (unusable) Video memory, ROM Area
; ## A rough overview of high mem ##
; Idealy this needs to be probed with the E820 functions
; # Start # End # size # description
;
; 0x00100000 0x00EFFFFF 0x00E00000 (14 MiB) RAM -- free for use (if it exists) Extended memory
; 0x00F00000 0x00FFFFFF 0x00100000 (1 MiB) Possible memory mapped hardware ISA Memory Hole 15-16MB
; 0x01000000 ???????? ??? (whatever exists) RAM -- free for use More Extended memory
; 0xC0000000 (sometimes) 0xFFFFFFFF 0x40000000 (1 GiB) Memory mapped PCI devices, PnP NVRAM?, IO APIC/s, local APIC/s, BIOS, ...
; 0x0000000100000000 ??? ??? (whatever exists) RAM -- free for use (PAE/64bit)/More Extended memory
; ???????????????? ??? ??? Potentially usable for memory mapped PCI devices in modern hardware (but typically not, due to backward compatibility)
; 0x2700 -> 0x28FF
%define disk_buffer 0x2700
; 0x2900 -> 0x2AFF
%define fat_buffer 0x2900
; 0x2B00 -> 0x2CFF
%define dir_buffer 0x2B00
; copy of partition table, 72 bytes
%define partition_table 0x3000
%define partition_table_SIZE 72
; copy of FAT32 BPB, 33 bytes (+1 to the next value to align to uint16_t)
;0x3048
%define fat32_bpb 0x3050
%define fat32_bpb_SIZE 33
; copy of FAT32 EBPB, 54 bytes
;0x306A
%define fat32_ebpb 0x3070
%define fat32_ebpb_SIZE 54
; FAT32 FSInfo, 512 bytes
;0x30A2
%define fat32_fsinfo 0x30B0
%define fat32_fsinfo_SIZE 512
; some stored state for the fat32 driver
;0x32A2
%define fat32_state 0x32B0
%define fat32_state_SIZE 32
; next free space is 0x32D0
%define fat32_nc_data 0x32D0
%define fat32_nc_data_size 16
; lba_packet for raw_disk_read
%define lba_packet 0x4000
%define BIOSMemoryMap 0x4200
%define SteviaInfo 0x4400
; High memory addresses for loading kernel (for use with unreal mode and 32bit override)
; file load buffer at 16MB
%define HMEM_load_buffer 0x1000000
;PhysicalAddress = Segment * 16 + Offset
%define SEG_TO_LINEAR(s,o) ((s << 4) + o)
; Offset = physical / (Segment * 16)
%define LINEAR_TO_OFFSET(p,s) ((p / (s << 4)))
; Seg = (physical - offset) / 16
%define LINEAR_TO_SEGMENT(p,o) ((p - o) >> 4)
; create normalized linear addres from seg:off (16:4)
; Segement = linear >> 4 (top 16 bits)
; offset = linear & 0x0F (low 4 bits)
; 20 bytes, passed to loaded kernel
struc SteviaInfoStruct_t
.MemoryMapPtr resd 1
.MemoryMapEntries resd 1
.BPBDataPtr resd 1
.EBPBDataPtr resd 1
endstruc
; Address Range Descriptor Structure
;
; Offset in Bytes Name Description
; 0 BaseAddrLow u32 - Low 32 Bits of Base Address
; 4 BaseAddrHigh u32 - High 32 Bits of Base Address
; 8 LengthLow u32 - Low 32 Bits of Length in Bytes
; 12 LengthHigh u32 - High 32 Bits of Length in Bytes
; 16 Type u32 - Address type of this range.
; 20 ExtType u32 - ACPI 3.0 extended type
struc AddressRangeDescStruct_t
.BaseAddrLow resd 1
.BaseAddrHigh resd 1
.LengthLow resd 1
.LengthHigh resd 1
.Type resd 1
.ExtType resd 1
endstruc
; moves argument into eax then pushes lower 16bits then upper 16 bits of of argument to stack
; eax is clobbered
%macro PUSH_DWORD 1
mov eax, %1
push ax
shr eax, 16
push ax
%endmacro
; same as PUSH_DWORD except no arguments, pushes EAX directly
%macro PUSH_DWORD_EAX 0
push ax
shr eax, 16
push ax
%endmacro
; pops upper 16bits then lower 16bits into eax
; eax is clobbered
%macro POP_DWORD_EAX 0
xor eax, eax
pop ax
shl eax, 16
pop ax
%endmacro
; moves data on stack referenced by bp to eax
; stack must be organized as follows (tl;dr push lower 16bits first ie. PUSH_DWORD macro)
; MOV_DWORD_EAX 2
; STACK TOP (0x0)
; upper_uint16 [bp-4]
; lower_uint16 [bp-2]
; --- [bp] ---
; ...
; STACK BOTTOM
;
; first argument == starting offset from bp for lower 16bits
%macro MOV_DWORD_EAX 1
mov ax, [bp-(%1+2)]
shl eax, 16
mov ax, [bp-%1]
; eax contains dword from stack
%endmacro
%macro DEBUG_HCF 0
DEBUG_LOOP:
hlt
jmp short DEBUG_LOOP
%endmacro
; uint8_t* kmemset(void* dest, uint8_t val, size_t len);
kmemset:
push di ; function uses di, so save it.
mov cx, [bp - 2] ; size_t len
mov al, [bp - 4] ; uint8_t val
mov di, [bp - 6] ; void * ptr
cld
rep stosb
.endf:
mov ax, [bp - 6] ; return pointer to dest
pop di ; restore di
ret
; uint8_t* kmemset(uint8_t* dest, uint8_t* src, size_t len);
; not overlap safe
kmemcpy:
push di
push si ; di, si are callee save
mov cx, [bp - 2] ; length
mov si, [bp - 4] ; source
mov di, [bp - 6] ; dest
cld ; ensure we are incrementing
rep movsb
.endf:
mov ax, [bp - 6] ; return pointer to dest
pop si
pop di
ret

View File

@@ -1,18 +1,19 @@
; Copyright (C) 2020 Bradley Claus
; Copyright (C) 2025 Elaina Claus
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
%ifndef __INC_PART_TABLE
; Partition table entry format
; Off. Size. Description
@@ -28,32 +29,18 @@ struc PartEntry_t
.chs_start resb 3
.part_type resb 1
.chs_end resb 3
.lba_start resb 4
.lba_length resb 4
.lba_start resd 1
.lba_length resd 1
endstruc
struc PartTable_t
.partition1 resb 16
.partition2 resb 16
.partition3 resb 16
.partition4 resb 16
.signature resb 4
.reserved resb 2
.partition1 resb PartEntry_t_size
.partition2 resb PartEntry_t_size
.partition3 resb PartEntry_t_size
.partition4 resb PartEntry_t_size
endstruc
;Offset Size Description
; 0 1 size of packet (16 bytes)
; 1 1 always 0
; 2 2 number of sectors to transfer (max 127 on some BIOSes)
; 4 4 transfer buffer (0xFFFF:0xFFFF)
; 8 4 lower 32-bits of starting 48-bit LBA
; 12 4 upper 32-bits of starting 48-bit LBA
; needs to be aligned to a uint32_t
struc LBAPkt_t
.size resb 1
.res0 resb 1
.xfer_size resw 1
.offset resw 1
.segment resw 1
.lower_lba resd 1
.upper_lba resd 1
endstruc
%endif
%define __INC_PART_TABLE

View File

@@ -0,0 +1,51 @@
; Copyright (C) 2025 Elaina Claus
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
%ifndef __INC_BOCHS_DEBUG_MAGIC
; for things like the error printer, opperate differently when we are targeting a dev (bochs) build
%define __STEVIA_DEV_DEBUG
; port_e9_hack: enabled=1 needs to be set in bochsrc.txt/bxrc
;
%ifnmacro __BOCHS_PRINTC
%macro __BOCHS_PRINTC 1
mov al, %1
out 0xe9, byte al
%endmacro
%endif
;
; port_e9_hack: enabled=1 needs to be set in bochsrc.txt/bxrc
;
%ifnmacro __BOCHS_BREAK
%macro __BOCHS_BREAK 0
push ax
mov ax, 0x8A00
out 0x8A00, word ax
pop ax
%endmacro
%endif
;
; magic_break: enabled=1 needs to be set in bochsrc.txt/bxrc
;
%ifnmacro __BOCHS_MAGIC_DEBUG
%macro __BOCHS_MAGIC_DEBUG 0
xchg bx, bx
%endmacro
%endif
%define __INC_BOCHS_DEBUG_MAGIC
%endif

View File

@@ -0,0 +1,45 @@
; Copyright (C) 2025 Elaina Claus
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
%ifndef __INC_ERROR_FUNC
%macro ERROR 1
%ifdef __STEVIA_DEV_DEBUG
__BOCHS_MAGIC_DEBUG
%endif
mov al, %1 ; al = 1 byte error code mapped to ascii values
jmp error
%endmacro
; pass error as ascii character in al, errors a-zA-Z or 0-9
ALIGN 4, db 0x90
error:
cmp al, STEVIA_DEBUG_OK
jge short .debug ; the 'letter >= W' (W, X, Y, Z) are used as special debug codes
mov ah, 0x4F ; color 0x4F is white text/red background
jmp short .print
.debug:
mov ah, 0x5F ; debug case is white text/purple background
.print:
mov dx, 0xB800
mov gs, dx
mov word [gs:0x0000], ax ; 0xB8000 = video memory
.halt:
cli
hlt
jmp short .halt
%endif
%define __INC_ERROR_FUNC

View File

@@ -0,0 +1,53 @@
; Copyright (C) 2025 Elaina Claus
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
%ifndef __INC_KMEM_FUNC
%include 'cdecl16.inc'
; void* kmemset_byte(void* dst, uint8_t val, uint16_t len);
ALIGN 4, db 0x90
kmemset:
__CDECL16_ENTRY
.func:
mov cx, [bp + 8] ; uint16_t len
mov al, byte [bp + 6] ; uint8_t val
mov di, [bp + 4] ; void * dst
cld
rep stosb
mov ax, di ; return pointer to dest + len (last elem of dest)
.endp:
__CDECL16_EXIT
ret
; uint8_t* kmemset(uint16_t* dest, uint16_t* src, uint16_t len);
; not overlap safe
ALIGN 4, db 0x90
kmemcpy:
__CDECL16_ENTRY
.func:
mov cx, [bp + 8] ; len
mov si, [bp + 6] ; src
mov di, [bp + 4] ; dest
cld ; ensure we are incrementing
rep movsb
mov ax, di ; return pointer to dest
.endf:
__CDECL16_EXIT
ret
%endif
%define __INC_KMEM_FUNC

View File

@@ -0,0 +1,48 @@
; Copyright (C) 2025 Elaina Claus
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
%ifndef __INC_KMEMCPY5_FUNC
%include 'cdecl16.inc'
; uint8_t* kmemset(word dest_segment, word dest, word src_segment, word src, byte len);
; not overlap safe, only for
ALIGN 4, db 0x90
kmemcpy5:
__CDECL16_ENTRY
push ds
push es
.setup_segments:
mov ax, [bp + 4]
mov ds, ax ; destination segment
mov ax, [ bp + 8]
mov es, ax ; source segment
.func:
mov cx, [bp + 12] ; len
mov si, [bp + 10] ; src
mov di, [bp + 6] ; dest
cld ; ensure we are incrementing
rep movsb ; move ds:si -> es:di
mov ax, di ; return pointer to dest
.restore_segments:
pop es
pop ds
.endf:
__CDECL16_EXIT
ret
%define __INC_KMEMCPY5_FUNC
%endif

View File

@@ -0,0 +1,42 @@
; Copyright (C) 2025 Elaina Claus
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
%ifndef __INC_KMEMSET4_FUNC
%include 'cdecl16.inc'
; word kmemset_byte(word segment, word dst, byte val, word len);
ALIGN 4, db 0x90
kmemset4:
__CDECL16_ENTRY
.setup_segment:
push es
mov ax, [bp + 4]
mov es, ax
.func:
mov cx, [bp + 10] ; size_t len
mov al, [bp + 8] ; uint8_t val
mov di, [bp + 6] ; word dst
cld
rep stosb ; move al -> es:di
mov ax, di ; return pointer to dest
.restore_segments:
pop es
.endf:
__CDECL16_EXIT
ret
%endif
%define __INC_KMEMSET4_FUNC

View File

@@ -1,40 +1,55 @@
#!/usr/bin/env bash
# Copyright (C) 2020 Bradley Claus
# Copyright (C) 2025 Elaina Claus
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <https://www.gnu.org/licenses/>.
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <https://www.gnu.org/licenses/>.
if ! [ $(id -u) = 0 ]; then
echo "Script must be run as root!"
echo "Script must be run as root!" >&2
exit 1
fi
# paths to bootcode
mbr_file=build/mbr.bin
vbr_file=build/vbr.bin
stage2_file=build/stage2.bin
boottest_file=build/BOOT_386.bin
boottest_file=build/BOOTi686.bin
# Disk creation options
mount_point=/tmp/stevia_disk
disk_tmp_file=/tmp/disk.img
disk_file_final=./disk.img.gz
if ! [ -e disk.img ]; then
# create raw disk image with 128MiB of space
dd if=/dev/zero of=disk.img bs=512 count=262144
# $disk_sector_size * $disk_size = total bytes, default is 256MiB
disk_size=(524288 * 2)
disk_sector_size=512
if ! [ -e $disk_tmp_file ]; then
# create raw disk image
if ! dd if=/dev/zero of=$disk_tmp_file bs=$disk_sector_size count=$disk_size; then
echo "Failed creating blank disk image." >&2
exit 1
fi
sync
else
echo "Removing old disk image..."
rm -rfv disk.img
dd if=/dev/zero of=disk.img bs=512 count=262144
rm -rfv $disk_tmp_file
if ! dd if=/dev/zero of=$disk_tmp_file bs=$disk_sector_size count=$disk_size; then
echo "Failed creating blank disk image." >&2
exit 1
fi
sync
fi
@@ -42,33 +57,68 @@ if [[ "$OSTYPE" == "linux-gnu"* ]]; then
if [ -e $mbr_file ] && [ -e $vbr_file ]; then
# get next loop device and mount it
ld=$(losetup -f)
losetup -b 512 $ld disk.img
losetup -P -b 512 $ld $disk_tmp_file
# create a DOS disk, with 1 FAT32 partition that is bootable, part1 starts at sector 2048
sfdisk $ld < scripts/loop_setup.sfdisk
# partprobe the image
partprobe $ld
# get first partition
# get first partition, this is sloppy might need to review this...
firstpart=$(lsblk -ilp -o NAME $ld | tr '\n' ' ' | awk '{print $3}')
mkfs.vfat -v -F32 $firstpart
mkfs.fat -v -F32 -s 1 -n 'STEVIAFS' $firstpart
#
# MBR setup
#
# copy MBR while preserving partition table
dd if=$mbr_file of=$ld bs=1 count=440
if ! dd if=$mbr_file of=$ld bs=1 count=440; then
echo "Failed to write MBR to disk. (part 1)" >&2
exit 1
fi
# copy MBR 0xAA55
dd if=$mbr_file of=$ld bs=1 seek=510 skip=510 count=2
if ! dd if=$mbr_file of=$ld bs=1 seek=510 skip=510 count=2; then
echo "Failed to write MBR to disk. (part 2)" >&2
exit 1
fi
#
# VBR Setup & backup VBR
#
# copy VBR to partition 1 while preserving partition information
# copy jmp short entry; nop
dd if=$vbr_file of=$firstpart bs=1 count=3
if ! dd if=$vbr_file of=$firstpart bs=1 count=3; then
echo "Failed to write VBR to disk. (part 1)" >&2
exit 1
fi
# copy bootcode
dd if=$vbr_file of=$firstpart bs=1 seek=90 skip=90 count=420
if ! dd if=$vbr_file of=$firstpart bs=1 seek=90 skip=90 count=420; then
echo "Failed to write VBR to disk. (part 2)" >&2
exit 1
fi
# copy 0xAA55
dd if=$vbr_file of=$firstpart bs=1 seek=510 skip=510 count=2
if ! dd if=$vbr_file of=$firstpart bs=1 seek=510 skip=510 count=2; then
echo "Failed to write VBR to disk. (part 3)" >&2
exit 1
fi
# write backup VBR
if ! dd if=$firstpart of=$firstpart bs=$disk_sector_size count=1 seek=6; then
echo "Failed to copy VBR (sector 1) to backup VBR." >&2
exit 1
fi
#
# Stage2 Setup
#
#stage2 to sectors 1-64
dd if=$stage2_file of=$ld bs=512 seek=1
if ! dd if=$stage2_file of=$ld bs=$disk_sector_size seek=1; then
echo "Failed to write Stage2 to disk." >&2
exit 1
fi
# copy boot32 boot test file to disk image
if ! [ -e $mount_point ]; then
@@ -76,32 +126,46 @@ if [[ "$OSTYPE" == "linux-gnu"* ]]; then
fi
mount $firstpart $mount_point
if [ -e $boottest_file ]; then
cp -v $boottest_file $mount_point
else
echo "unable to find boot32.bin!"
exit 3
# ensure mountpoint is actually a mountpoint
if ! mountpoint -q $mount_point; then
echo "Failed to mount partition at $mount_point." >&2
exit 1
fi
# copy kernel to filesystem
if [ -e $boottest_file ]; then
cp -v $boottest_file $mount_point/BOOT.BIN
else
echo "Failed to write $boottest_file to disk image" >&2
exit 1
fi
#
# Final Cleanup
#
# detach loop device
umount $mount_point
sync
sleep 1
losetup -d $ld
# chown to the real user to prevent issues with reading/writing the file later
SUDOUSER=$(logname)
chown --from=root:root ${SUDOUSER}:$(id $SUDOUSER -g) disk.img
# BUG: ${logname}:$(id $(logname -g)) doesn't work right on WSL because of runlevel hacks in WSL
# BUG: https://github.com/microsoft/WSL/issues/1761
# as a work around I'll just reference LICENSE.md...WHICH SHOULD ALWAYS BE THERE 👀
chown --from=root:root --reference=LICENSE.md $disk_tmp_file
else
echo "unable to find MBR/VBR binaries!"
exit 2
echo "unable to find MBR/VBR binaries!" >&2
exit 1
fi
# requires util-linux from homebrew
elif [[ "$OSTYPE" == "darwin"* ]]; then
sfdisk_path="/usr/local/opt/util-linux/sbin/sfdisk"
if [ -e $mbr_file ] && [ -e $vbr_file ]; then
# use hdiutil to attach our empty disk image
ld_path_raw=$(hdiutil attach -readwrite -imagekey diskimage-class=CRawDiskImage -nomount -blocksize 512 -noverify disk.img)
ld_path_raw=$(hdiutil attach -readwrite -imagekey diskimage-class=CRawDiskImage -nomount -blocksize 512 -noverify /tmp/disk.img)
ld=$(echo $ld_path_raw | sed s:/dev/::)
ld_path="/dev/$ld"
@@ -124,7 +188,7 @@ elif [[ "$OSTYPE" == "darwin"* ]]; then
unset ld
unset ld_path_raw
ld_path_raw=$(hdiutil attach -readwrite -imagekey diskimage-class=CRawDiskImage -nomount -blocksize 512 -noverify disk.img)
ld_path_raw=$(hdiutil attach -readwrite -imagekey diskimage-class=CRawDiskImage -nomount -blocksize 512 -noverify /tmp/disk.img)
ld=$(echo $ld_path_raw | grep "FDisk_partition_scheme" | awk '{print $1}' | sed s:/dev/::)
ld_path="/dev/$ld"
@@ -154,7 +218,7 @@ elif [[ "$OSTYPE" == "darwin"* ]]; then
dd if=$vbr_file of=/dev/$firstpart bs=1 seek=510 skip=510 count=2 conv=sync
#stage2 to sectors 1-64
dd if=$stage2_file of=$ld_path bs=512 seek=1 conv=sync
dd if=$stage2_file of=$ld_path bs=$disk_sector_size seek=1 conv=sync
#sync pending dd stuff
sync
@@ -184,13 +248,13 @@ elif [[ "$OSTYPE" == "darwin"* ]]; then
# chown to the real user to prevent issues with reading/writing the file later
SUDOUSER=$(logname)
chown ${SUDOUSER}:staff disk.img
gzip -9kc $disk_tmp_file > $disk_file_final
else
echo "unable to find MBR/VBR binaries!"
exit 2
fi
else
# Unknown.
echo "Unknown OS type! Supported build hosts systems are GNU/Linux and macOS."
echo "Unknown OS type! Supported build hosts systems are GNU/Linux (WSL) and macOS."
exit 1
fi

View File

@@ -1,4 +1,5 @@
label: dos
unit: sectors
sector-size: 512
start= 2048, type=b, bootable
start= 2048, type=c, bootable

200
src/mbr/mbr.nasm Executable file
View File

@@ -0,0 +1,200 @@
; Copyright (C) 2025 Elaina Claus
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
[BITS 16]
[ORG 0x8C00]
[CPU KATMAI]
[WARNING -reloc-abs-byte]
[WARNING -reloc-abs-word] ; Yes, we use absolute addresses. surpress these warnings.
[map all mbr.map]
%define __STEVIA_MBR
jmp short (init - $$)
nop
; ###############
; Headers/Includes/Definitions
; ###############
%include "util/bochs_magic.inc"
%include "cdecl16.inc"
%include "entry.inc"
%include "config.inc"
%include "error_codes.inc"
%include "partition_table.inc"
%include "fat32/fat32_structures.inc"
%undef __STEVIA_DEV_DEBUG
ALIGN 4
init:
cli ; We do not want to be interrupted
xor ax, ax
mov ds, ax ; Set segment registers to 0x0000
mov es, ax
mov fs, ax
mov gs, ax
mov ss, ax ; Set Stack Segment to 0
mov sp, end_bss ; Setup stack
mov bp, sp ; base ptr = stack ptr
; Zero BSS section
mov cx, (end_bss - begin_bss) ; count = bss length
mov ax, begin_bss
mov di, ax ; es:di is dest
xor ax, ax
cld
rep stosb ; zero bss section
sub sp, 0x20 ; local varible space
push bp ; setup top of stack frame
xor cx, cx
mov ch, 0x02 ; 0x0200 in cx
mov si, 0x7C00 ; Current MBR Address (loaded here by BIOS)
mov di, MBR_ENTRY ; New MBR Address (our new relocation address)
rep movsb ; copy 512 bytes from 0x0000:7c00 to 0x0000:MBR_ENTRY (7A00 as of writing)
sti
jmp 0:main
; ###############
; Extra/Shared Functions
; ###############
%include "util/kmem_func.nasm"
%include "util/error_func.nasm"
;
; bp - 2 : uint8_t boot_drive
; bp - 4 : uint16_t part_offset
ALIGN 4, db 0x90
main:
mov byte [bp - 2], dl ; BIOS passes drive number in DL
.check_disk:
cmp byte [bp - 2], 0x80
jae main.check_extentions
ERROR MBR_ERROR_DISK_T_ERR
.check_extentions:
xor ax, ax
mov ah, 0x41
mov bx, 0x55AA
mov dl, 0x80
int 0x13
jnc main.find_active
ERROR MBR_ERROR_NO_INT32E ; no extended function support
.find_active:
mov bx, PartEntry1 ; base = first partition
mov cx, 4 ; there are only 4 entries
.find_active_L0:
mov al, byte [bx + PartEntry_t.attributes]
test al, 0x80 ; 0x80 == 1000_0000b
jnz main.active_found
add bx, 0x10 ; add 16 bytes to offset
loop main.find_active_L0
ERROR MBR_ERROR_NO_NO_BOOT_PART
.active_found:
mov ax, bx
sub ax, DiskSig ; leaves us with the offset relative from start of table
; this gives us an offset from the begining of the partition table
mov word [bp - 4], ax ; update part_offset
.read_data:
movzx ax, byte [bp - 2]
push ax ; drive_num
mov ax, 0x1
push ax ; count
mov dword eax, dword [bx + PartEntry_t.lba_start]
push dword eax ; lba
mov ax, VBR_ENTRY
push ax ; offset = 0x7c00
xor ax, ax
push ax ; segment = 0
; uint8_t read_stage2_raw(uint16_t buf_segment, uint16_t buf_offset,
; uint32_t lba,
; uint16_t count, uint16_t drive_num)
call read_disk_raw
add sp, 0xC
.goto_vbr:
cmp word [VBR_ENTRY + 0x1FE], 0xAA55
je main.sig_ok
ERROR MBR_ERROR_NO_VBR_SIG ; no signature present
.sig_ok:
mov ax, PartTable_t_size
push ax
mov ax, DiskSig ; start of partition table
push ax
mov ax, partition_table
push ax
call kmemcpy ; copy partition table to bss
add sp, 0x6
mov si, word [bp - 4]
mov dl, byte [bp - 2]
mov bx, partition_table
jmp word 0x0000:VBR_ENTRY
; ###############
;
; BIOS Functions
;
; ###############
%include 'BIOS/func/ext_read.nasm'
%assign bytes_remaining (440 - ($ - $$))
%warning MBR has bytes_remaining bytes remaining for code (MAX: 440 bytes)
times ((512 - 72) - ($ - $$)) nop ; Fill the rest of sector with nop
DiskSig:
times 4 db 0x00
Reserved:
dw 0x0000
PartEntry1:
times 16 db 0x00
PartEntry2:
times 16 db 0x00
PartEntry3:
times 16 db 0x00
PartEntry4:
times 16 db 0x00
BootSig:
dw 0xAA55 ; Add boot signature at the end of bootloader
section .bss follows=.text
begin_bss:
align 16, resb 1
partition_table resb PartTable_t_size
align 16, resb 1
lba_packet resb LBAPkt_t_size
align 512, resb 1
stack_bottom resb 512 ; 512 byte stack early on
stack_top:
mbr_redzone resb 32
end_bss:

View File

@@ -1,239 +0,0 @@
; Copyright (C) 2020 Bradley Claus
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
[BITS 16]
[ORG 0x7A00]
[CPU KATMAI]
jmp short init
nop
%include "entry.inc"
init:
cli ; We do not want to be interrupted
xor ax, ax ; 0 AX
mov ds, ax ; Set segment registers to 0
mov es, ax ; *
mov ss, ax ; Set Stack Segment to 0
mov sp, STACK_START
mov ch, 0x01 ; 256 WORDs in MBR (512 bytes), 0x0100 in cx
mov si, 0x7C00 ; Current MBR Address (loaded here by BIOS)
mov di, MBR_ENTRY ; New MBR Address (our new relocation address)
rep movsw ; copy 512 bytes from 0x0000:7c00 to 0x0000:0600
jmp 0:main
nop
%include "config.inc"
%include "memory.inc"
%include "partition_table.inc"
%include "errors.inc"
main:
sti
mov [boot_drive], dl ; BIOS passes drive number in DL
.check_disk:
cmp dl, 0x80
jae main.find_active
ERROR MBR_ERROR_DISK_T_ERR
.check_extentions:
xor ax, ax
mov bx, 0x55AA
mov dl, byte [boot_drive]
int 0x13
jnc main.find_active
ERROR MBR_ERROR_NO_INT32E ; no extended function support
.find_active:
mov bx, PartEntry1 ; base = first partition
mov cx, 4 ; there are only 4 entries
.find_active_L0:
mov al, byte [bx + PartEntry_t.attributes]
test al, 0x80 ; 0x80 == 1000_0000b
jnz main.active_found
add bx, 0x10 ; add 16 bytes to offset
loop main.find_active_L0
ERROR MBR_ERROR_NO_NO_BOOT_PART
.active_found:
mov ax, bx
sub ax, DiskSig ; leaves us with the offset relative from start of table
; this gives us an offset from the begining of the partition table
mov word [part_offset], ax ; update part_offset
.read_data:
push bp
mov bp, sp
;uint8_t read_disk_raw(size_t count, uint16_t buf_segment, uint16_t buf_offset,
; uint16_t lower_lower_lba, uint16_t upper_lower_lba)
mov eax, dword [bx + PartEntry_t.lba_start]
ror eax, 16
push ax
ror eax, 16
push ax
mov ax, VBR_ENTRY
push ax
xor ax, ax
push ax ; segment = 0
mov ax, 1
push ax
call read_disk_raw
leave
jnc main.goto_vbr
ERROR MBR_ERROR_DISK_READ_ERR ; error in LBA read
.goto_vbr:
cmp word [VBR_ENTRY + 0x1FE], 0xAA55
je main.sig_ok
ERROR MBR_ERROR_NO_VBR_SIG ; no signature present
.sig_ok:
push bp
mov bp, sp
mov ax, partition_table_SIZE ; 72 bytes of data
push ax
mov ax, DiskSig ; start of partition table
push ax
mov ax, partition_table ; defined in memory.inc
push ax
call kmemcpy ; copy partition table to memory
leave
xor ah, ah ; Set Video mode BIOS function
mov al, 0x02 ; 16 color 80x25 Text mode
int 0x10 ; Call video interrupt
mov ah, 0x05 ; Select active display page BIOS function
xor al, al ; page 0
int 0x10 ; call video interrupt
mov si, word [part_offset]
mov dl, byte [boot_drive]
jmp 0:0x7C00
; Wrapper for AH=0x42 INT13h (Extended Read)
;
; BIOS call details
; AH = 42h
; DL = drive number
; DS:SI -> disk address packet
;
; Return:
; CF clear if successful
; AH = 00h
; CF set on error
; AH = error code
; disk address packet's block count field set to number of blocks
; successfully transferred
;
;
; uint8_t read_disk_raw(uint16_t buf_segment, uint16_t buf_offset, uint16_t lower_lower_lba, uint16_t upper_lower_lba)
; bp-0 = call frame
; bp-2 = upper_lower_lba
; bp-4 = lower_lower_lba
; bp-6 = offset
; bp-8 = segment
; bp-10 = count
; bp-12 = ret ptr
read_disk_raw:
push si
; uint8_t* kmemset(void* dest, uint8_t val, size_t len);
push bp
mov bp, sp
mov ax, 0x10
push ax ; len = 16 bytes
xor ax, ax
push ax ; val = 0
mov ax, lba_packet
push ax ; dest = lba_packet address
call kmemset
leave
mov byte [lba_packet + LBAPkt_t.size], 0x10
mov word [lba_packet + LBAPkt_t.xfer_size], STAGE2_SECTOR_COUNT
mov ax, [bp-2]
shl eax, 16
mov ax, [bp-4]
mov dword [lba_packet + LBAPkt_t.lower_lba], eax
mov ax, [bp-6]
mov word [lba_packet + LBAPkt_t.offset], ax
mov ax, [bp-8]
mov word [lba_packet + LBAPkt_t.segment], ax
mov si, lba_packet
mov ah, 0x42
mov dl, byte [boot_drive]
int 0x13
jnc read_disk_raw.endf
mov al, 'B'
jmp error
.endf:
pop si
ret
; #############
;
; Locals
;
; #############
boot_drive:
db 0x00
mbr_reserved1:
db 0x00
; OFFSET from BEGINING of partition table, ie. DiskSig (-6 from PartEntry1)
part_offset:
dw 0x0000
%assign bytes_remaining (440 - ($ - $$))
%warning MBR has bytes_remaining bytes remaining for code (MAX: 440 bytes)
times ((512 - 72) - ($ - $$)) nop ; Fill the rest of sector with nop
DiskSig:
times 4 db 0x00
Reserved1:
db 0x00
Reserved2:
db 0x00
PartEntry1:
times 16 db 0x00
PartEntry2:
times 16 db 0x00
PartEntry3:
times 16 db 0x00
PartEntry4:
times 16 db 0x00
BootSig:
dw 0xAA55 ; Add boot signature at the end of bootloader

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@@ -1,554 +0,0 @@
; Copyright (C) 2020 Bradley Claus
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
[BITS 32]
[ORG 0x100000]
[CPU KATMAI]
jmp short start32
nop
; Unless noted otherwise, functions will be the standard x86 cdecl used in GCC
; In cdecl, subroutine arguments are passed on the stack.
; Integer values and memory addresses are returned in the EAX register,
; floating point values in the ST0 x87 register.
; Registers EAX, ECX, and EDX are caller-saved,
; and the rest are callee-saved.
; The x87 floating point registers ST0 to ST7 must be empty (popped or freed)
; when calling a new function, and ST1 to ST7 must be empty on exiting a function.
; ST0 must also be empty when not used for returning a value.
;
; EXAMPLE: to call uint8_t* kmemset(uint8_t* dest, uint8_t val, uint8_t size);
; => kmemset(*((char*) 0xb8000), 'F', (80*25))
;
; push ebp ; save old call frame pointer
; mov ebp, esp ; new call frame pointer
; push 0x000007D0 ; push args RTL, EBP - 4
; push 'F' ; * EBP - 8
; push 0x000b8000 ; * EBP - 12
; call kmemset ; call function, this also places a return pointer on stack
; add esp, 12 ; remove call arguments from stack frame
; mov esp, ebp ; restore stack frame pointer (callee saves EBP)
; pop ebp ; restore call frame pointer
;
;
; 33 bytes BPB + 26 Byte EBPB
struc BPBStruct
.OemName resb 8
.BytesPerSect resw 1
.SecsPerClust resb 1
.ResSectors resw 1
.FATs resb 1
.RootDirEnts resw 1
.Sectors resw 1
.Media resb 1
.SectPerFAT resw 1
.SectPerTrack resw 1
.Heads resw 1
.Hidden resd 1
.SectorHuge resd 1
; begin EBPB
.DriveNumber resb 1
.NTReserved resb 1
.Signature resb 1
.VolumeID resd 1
.VolumeLabel resb 11
.SysIdent resb 8
endstruc
; 12 bytes
struc FSInfoStruct
.first_root_dir_sector resw 1
.last_root_dir_sector resw 1
.root_dir_len resw 1
.first_data_sector resw 1
.active_cluster resw 1
.active_FAT_cluster resw 1
endstruc
; 20 bytes
struc KInfoStruct
.load_address resd 1
.file_len resd 1
.file_name resb 8
.file_ext resb 3
.reserved1 resb 1
endstruc
; Address Range Descriptor Structure
;
; Offset in Bytes Name Description
; 0 BaseAddrLow u32 - Low 32 Bits of Base Address
; 4 BaseAddrHigh u32 - High 32 Bits of Base Address
; 8 LengthLow u32 - Low 32 Bits of Length in Bytes
; 12 LengthHigh u32 - High 32 Bits of Length in Bytes
; 16 Type u32 - Address type of this range.
; 20 ExtType u32 - ACPI 3.0 extended type
struc AddressRangeDescStruct
.BaseAddrLow resd 1
.BaseAddrHigh resd 1
.LengthLow resd 1
.LengthHigh resd 1
.Type resd 1
.ExtType resd 1
endstruc
; 20 bytes, passed to loaded kernel
struc CBootInfoStruct
.MemoryMapPtr resd 1
.MemoryMapEntries resd 1
.BPBDataPtr resd 1
.FSInfoPtr resd 1
.KInfoPtr resd 1
endstruc
;;;
; Errors
; 0 = unused
; 1 = No CPUID support on this platform (VM or some very old hardware?)
; 2 = magic signature not found at end of file
; 3 = Unexpected/unhandled artithmetic overflow/carry
;;;
%define MAX_BYTES (1024 * 8)
%define VGA_BUF 0xb8000
;black BG/Green FG
%define TTY_COLOR 0x0200
;black BG/Red FG
%define TTY_ERR_CLR 0x0400
;subtract 1 for max array values
%define VGA_MAX_Y 25
%define VGA_MAX_X 80
; VGA memory is row-major => offset = (row * MAX_Colums) + colum
; macro array is counted from 0,0 = 1,1 => 79,24 is the last usable space in a page
%define VGA_OFFSET(x,y) (((y*VGA_MAX_X) + x)*2)
start32:
mov ax, 0x10
mov ds, ax
mov es, ax
mov fs, ax
mov gs, ax
mov ss, ax ; load data registers with 2nd GDT selector
mov esp, stack_top
mov ebp, esp
; debugger hack because gdb doesn't like to switch register sizes
; issue a set $eax = 1 to continue
%ifdef DEBUG_HACK
mov eax, 0
.gdb_hack:
test eax, eax
jz start32.gdb_hack
%endif
mov eax, dword [BOOT_SIG]
cmp eax, 0xA0B0C0D0
jz start32.signature_present
mov al, "2"
call error
.signature_present:
call check_cpuid
push ebp
mov ebp, esp
lea eax, [welcome_cstr]
push eax
call vga_puts
leave
push ebp
mov ebp, esp
lea eax, [version_cstr]
push eax
call vga_puts
leave
push ebp
mov ebp, esp
lea eax, [datetime_cstr]
push eax
call vga_puts
leave
mov eax, VGA_BUF
add eax, VGA_OFFSET(78, 24)
mov dword [eax], 0x2f4b2f4f
hlt
; Early error printer. Prints 'ERR: X' where X is an error code in al
error:
mov eax, VGA_BUF
add eax, VGA_OFFSET(73, 24)
mov dword [eax], 0x4f524f45
add eax, 0x2
mov dword [eax], 0x4f3a4f52
add eax, 0x2
mov dword [eax], 0x4f204f20
add eax, 0x2
mov byte [eax], al
hlt
check_cpuid:
; flip cpuid id bit (bit 21) to check for cpuid support
; copy flags to eax via stack
pushfd
pop eax
mov ecx, eax ; copy to ecx for compare
xor eax, 1 << 21 ; xor eax with the 21st bit set
push eax ; push new flags and pop to flags register
popfd
pushfd
pop eax
cmp eax, ecx ; can we change the bit?
je .no_cpuid
ret
.no_cpuid:
mov al, "1"
call error
; int vga_puts(char* str)
;
; INPUT:
; str: C-Sytle string
;
; OUTPUT:
; EAX = characters printed
;
vga_puts:
; prolog, EBP = SFP (Stack frame pointer), [EBP-4] = char* str
push edi
push esi
push ebx
.get_str_len:
mov edi, [ebp - 4]
xor ecx, ecx ; ECX = 0
not ecx ; ECX = -1 == 0xFFFFFFFF
xor eax, eax ; search for al = 0x0
cld
repne scasb ; deincrement ecx while searching for al
not ecx ; the inverse of a neg number = abs(x) - 1
dec ecx ; ECX contains the length of the string - nul byte at end
mov edi, VGA_BUF ; load dest index with VGA buffer + calculated offset
mov esi, [ebp -4] ; load source index with src string
; ECX = string length
; ESI = source string to print
; EDI = destination in the VGA buffer
.print_char:
cmp ecx, 0x0
jle vga_puts.endf
cmp byte [vga_buf_pos_x], 80
je vga_puts.end_of_line
cmp byte [vga_buf_pos_y], 25
je vga_puts.scroll_up
cmp byte [esi], 0x20
jl vga_puts.special_character_switch
push ebp
mov ebp, esp
xor eax, eax
mov al, [vga_buf_pos_y]
push eax ; vga_pos_y
xor eax, eax
mov al, [vga_buf_pos_x]
push eax ; vga_pos_x
; uint16_t vga_calc_offset(uint8_t vga_pos_x, uint8_t vga_pos_y)
call vga_calc_offset
leave
xor bx, bx
mov bl, byte [esi]
or bx, TTY_COLOR ; create VGA character
mov [edi+eax], bx
inc esi
inc byte [vga_buf_pos_x]
dec ecx
jmp vga_puts.print_char ; loop until ECX == 0
.end_of_line:
; advance to next row
inc byte [vga_buf_pos_y]
mov byte [vga_buf_pos_x], 0
jmp vga_puts.print_char
.scroll_up:
; after 25 rows, move to next page (either swap pages [memcpy] or erase page 0)
mov byte [vga_buf_pos_x], 0
mov byte [vga_buf_pos_y], 0
push ebp
mov ebp, esp
mov eax, 0x7D0
push eax ; 1 VGA page = 0x7D0 elements
xor eax, eax
push eax ; we want to blank the page with 0x0000
mov eax, VGA_BUF
push eax ; load vga buffer base (0xb8000)
; uint16_t* kmemset_word(void* dest, uint16_t val, size_t len);
call kmemset_byte
leave
jmp vga_puts.print_char
.special_character_switch:
cmp byte[esi], 0xA
je vga_puts.handle_LF
cmp byte[esi], 0xD
je vga_puts.handle_CR
; Default case
.special_character_endp:
dec ecx
inc esi
jmp vga_puts.print_char
.handle_LF:
; advance to next row
inc byte [vga_buf_pos_y]
jmp vga_puts.special_character_endp
.handle_CR:
mov byte [vga_buf_pos_x], 0
jmp vga_puts.special_character_endp
.endf:
pop ebx
pop esi
pop edi
ret
; short vga_get_xy(void)
;
; INPUT:
;
; OUTPUT:
; EAX = xy_pos
; > x = xy_pos && 0xFF00
; y = xy_pos && 0x00FF
; 2 MSB of EAX are 0.
;
vga_get_xy:
.endf:
ret
; void vga_set_xy(short xy_pos)
; xy_pos is a byte packed word (16bit value), MSB is x, LSB is y
; => x = xy_pos && 0xFF00
; y = xy_pos && 0x00FF
;
; INPUT:
; xy_pos
;
; OUTPUT:
; NONE
;
vga_set_xy:
.endf:
ret
; uint16_t vga_calc_offset(uint8_t vga_pos_x, uint8_t vga_pos_y)
; VGA_OFFSET(x,y) == (((y*VGA_MAX_X) + x)*2)
vga_calc_offset:
xor eax, eax
xor edx, edx
mov edx, [ebp-4]
mov ax, VGA_MAX_X
mul dx ; DX:AX contains (y*VGA_MAX_X)
jc vga_calc_offset.artithmetic_error
mov edx, [ebp-8]
add ax, dx
jc vga_calc_offset.artithmetic_error
mov dx, 0x02
mul dx ; DX:AX contains (y*VGA_MAX_X) + x) * 2
jnc vga_calc_offset.endf
.artithmetic_error:
mov al, '3'
call error
.endf:
; (e)AX contains the offset
ret
; uint32_t* kmemset(void* dest, uint32_t val, size_t len);
kmemset_dword:
push edi ; function uses edi, so save it.
; [ebp] = previous call frame
mov ecx, [ebp - 4] ; size_t len
mov eax, [ebp - 8] ; uint32_t val
mov edi, [ebp - 12] ; void * ptr
; [ebp - 16] = return adress
; [ebp - 20] = saved EDI
rep stosd
.endf:
mov eax, [ebp - 12] ; return pointer to dest
pop edi ; restore edi
ret
; uint16_t* kmemset(void* dest, uint16_t val, size_t len);
kmemset_word:
push edi ; function uses edi, so save it.
; [ebp] = previous call frame
mov ecx, [ebp - 4] ; size_t len
mov ax, [ebp - 8] ; uint16_t val
mov edi, [ebp - 12] ; void * ptr
; [ebp - 16] = return adress
; [ebp - 20] = saved EDI
rep stosw
.endf:
mov eax, [ebp - 12] ; return pointer to dest
pop edi ; restore edi
ret
; uint8_t* kmemset(void* dest, uint8_t val, size_t len);
kmemset_byte:
push edi ; function uses edi, so save it.
; [ebp] = previous call frame
mov ecx, [ebp - 4] ; size_t len
mov al, [ebp - 8] ; uint8_t val
mov edi, [ebp - 12] ; void * ptr
; [ebp - 16] = return adress
; [ebp - 20] = saved EDI
rep stosb
.endf:
mov eax, [ebp - 12] ; return pointer to dest
pop edi ; restore edi
ret
; uint32_t* kmemset(uint32_t* dest, uint32_t* src, size_t len);
kmemcpy_dword:
push edi
push esi ; edi, esi are callee save
mov edi, [ebp-12] ; dest
mov esi, [ebp-8] ; source
mov ecx, [ebp-4] ; length
cld ; ensure we are incrementing
rep movsd
.endf:
mov eax, [ebp-12] ; return pointer to dest
pop esi
pop edi
ret
; uint16_t* kmemset(uint16_t* dest, uint16_t* src, size_t len);
kmemcpy_word:
push edi
push esi ; edi, esi are callee save
mov edi, [ebp-12] ; dest
mov esi, [ebp-8] ; source
mov ecx, [ebp-4] ; length
cld ; ensure we are incrementing
rep movsw
.endf:
mov eax, [ebp-12] ; return pointer to dest
pop esi
pop edi
ret
; uint8_t* kmemset(uint8_t* dest, uint8_t* src, size_t len);
; not overlap safe
kmemcpy_byte:
push edi
push esi ; edi, esi are callee save
mov edi, [ebp-12] ; dest
mov esi, [ebp-8] ; source
mov ecx, [ebp-4] ; length
cld ; ensure we are incrementing
rep movsb
.endf:
mov eax, [ebp-12] ; return pointer to dest
pop esi
pop edi
ret
; Static Values
vga_buf_pos_x:
db 0x00
vga_buf_pos_y:
db 0x00
; Strings
%define StrCRLF_NUL 0Dh, 0Ah, 00h
welcome_cstr:
db 'CBoot Stage3', StrCRLF_NUL
version_cstr:
db 'CBoot v0.0.3 ', 'NASM - ', __NASM_VER__, StrCRLF_NUL
datetime_cstr:
db 'Assembled - ', __DATE__, ' ', __TIME__, StrCRLF_NUL
ALIGN 16, db 0
stack_bottom:
times (512 * 8) db 0x00 ; 4KiB stack
stack_top:
%assign bytes_remaining ((MAX_BYTES - 4) - ($ - $$))
%warning boot32 has bytes_remaining bytes remaining for code (MAX: MMAX_BYTES)
times ((MAX_BYTES - 4) - ($ - $$)) db 0xFE
BOOT_SIG: dd 0xA0B0C0D0

94
src/miniboot32/BOOTi686.nasm Executable file
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@@ -0,0 +1,94 @@
; Copyright (C) 2025 Elaina Claus
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
[BITS 32]
[ORG 0x100000]
[CPU KATMAI]
jmp short (init32 - $$) ; PI jump
nop
;;;
; Errors
; 0 = unused
; E = General Error
; S = magic signature not found at end of file
; O = OK
;;;
%define MAX_BYTES (1024 * 8)
%define VGA_BUF 0xb8000
; VGA memory is row-major => offset = (row * MAX_Colums) + colum
; macro array is counted from 0,0 = 1,1 => 79,24 is the last usable space in a page
%define VGA_OFFSET(x,y) (((y*VGA_MAX_X) + x)*2)
;subtract 1 for max array values
%define VGA_MAX_Y 25
%define VGA_MAX_X 80
ALIGN 16, db 0
init32:
mov ax, 0x10 ; 0x10 selector segment
mov ds, ax
mov es, ax
mov fs, ax
mov gs, ax
mov ss, ax ; load data registers with 2nd GDT selector
mov esp, stack_top
mov ebp, esp
mov eax, dword [BOOT_SIG]
cmp eax, 0xA0B0C0D0
jz .signature_present
mov dl, "S"
jmp .result
.signature_present:
mov dl, "O"
.result:
mov eax, VGA_BUF
add eax, VGA_OFFSET(73, 24)
mov dword [eax], 0x1f451f52
add eax, 0x4
mov dword [eax], 0x1f3e1f53
add eax, 0x4
; RES> in white-on-blue
mov ecx, 0x1f201f20
and cl, dl ; 0x1f201f(dl)
ror ecx, 16 ; 0x1f(dl)1f20 = ' (dl)'
mov dword [eax], ecx ; should be a space and contents of dl
.endp:
hlt
jmp .endp - $$
; Strings
ALIGN 16, db 0
%define StrCRLF_NUL 0Dh, 0Ah, 00h
version_cstr:
db 'CBoot v0.0.3 ', 'NASM - ', __NASM_VER__, StrCRLF_NUL
datetime_cstr:
db 'Assembled - ', __DATE__, ' ', __TIME__, StrCRLF_NUL
ALIGN 16, db 0
stack_bottom:
times (512 * 8) db 0x00 ; 4KiB stack
stack_top:
%assign bytes_remaining ((MAX_BYTES - 4) - ($ - $$))
%warning boot32 has bytes_remaining bytes remaining for code (MAX: MMAX_BYTES)
times ((MAX_BYTES - 4) - ($ - $$)) db 0xFE
BOOT_SIG: dd 0xA0B0C0D0

553
src/stage2/stage2.nasm Executable file
View File

@@ -0,0 +1,553 @@
; Copyright (C) 2025 Elaina Claus
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
[BITS 16]
[ORG 0x0500] ; IF YOU CHANGE ORG CHANGE THE SIGN OFFSET AT THE END
[CPU KATMAI]
[map all stage2.map]
[WARNING -reloc-abs-byte]
[WARNING -reloc-abs-word]
[WARNING -reloc-abs-dword] ; Yes, we use absolute addresses. surpress these warnings.
%define __STEVIA_STAGE2
%define __STAGE2_SEGMENT 0x0000
; ###############
; Headers/Includes/Definitions
; ###############
%include "util/bochs_magic.inc"
%include "cdecl16.inc"
%include "entry.inc"
%include "config.inc"
%include "early_mem.inc"
%include "error_codes.inc"
%macro print_string 1
mov ax, %1
push ax
call PrintString
add sp, 0x2
%endmacro
section .text
begin_text:
; dl = byte boot_drive
; ax = word part_offset (active partition offset)
; si = ptr PartTable_t partition_table
; di = ptr FAT32_bpb_t fat32_bpb
ALIGN 4, db 0x90
init:
cli ; We do not want to be interrupted
; these 4 are stored in the .data section and are effectivly const types
mov [vbr_part_table_ptr], si ; pointer to partition_table
mov [vbr_fat32_bpb_ptr], di ; pointer to fat32_bpb
mov [boot_drive], dl ; copy boot_drive to globals
mov [partition_offset], ax ; copy partition_offset to globals
mov ax, __STAGE2_SEGMENT ; set all our segments to the configured segment, except es
mov ds, ax ; *
mov fs, ax ; *
mov gs, ax ; *
mov ss, ax
; Zero BSS section
mov cx, (end_bss - begin_bss) ; count = bss length
mov ax, begin_bss
shr ax, 4
mov es, ax ; es = begining of bss section, remember to restore ES later
xor ax, ax ; val = 0
mov di, ax ; dst = 0 (start of segment)
cld
rep stosb
mov ax, __STAGE2_SEGMENT
mov es, ax
; done zeroing bss section
mov sp, stack_top
mov bp, sp
sub sp, 0x10
push bp ; setup a somewhat normal stack frame, minus a ret ptr
sti
jmp word __STAGE2_SEGMENT:main
; ###############
; Functions
; ###############
%include "util/kmem_func.nasm"
%include "util/kmemcpy5_func.nasm"
%include "util/kmemset4_func.nasm"
%include "util/error_func.nasm"
; ###############
; FAT32 Driver
; ###############
%include 'fat32/FAT32_SYS.inc'
; ###############
; BIOS functions
; ###############
%include 'BIOS/BIOS_SYS.inc'
; structures
struc SteviaInfoStruct_t
.MemoryMapPtr resd 1
.MemoryMapEntries resd 1
endstruc
struc EarlyBootStruct_t
.partition_table resb PartTable_t_size
.fat32_bpb resb FAT32_bpb_t_size
.fat32_ebpb resb FAT32_ebpb_t_size
endstruc
ALIGN 4, db 0x90
main:
__BOCHS_MAGIC_DEBUG
.check_sig:
mov eax, dword [STAGE2_SIG]
cmp eax, 0xDEADBEEF
je main.stage2_main
ERROR STAGE2_SIGNATURE_MISSING
.stage2_main:
mov ax, PartTable_t_size
push ax ; len = PartTable_t_size
mov ax, word [vbr_part_table_ptr] ; src = ptr to vbr partition_table
push ax
mov ax, partition_table ; dst
push ax
call kmemcpy ; copy partition table data to .data section in stage2
add sp, 0x6
mov ax, (FAT32_bpb_t_size + FAT32_ebpb_t_size) ; len
push ax
mov ax, word [vbr_fat32_bpb_ptr] ; src
push ax
mov ax, fat32_bpb ; dst
push ax
call kmemcpy ; copy bpb & ebpb to memory
add sp, 0x6
call SetTextMode
call disable_cursor
print_string HelloPrompt_info
; enable A20 gate
call EnableA20
print_string A20_Enabled_OK_info
; get system memory map
call GetMemoryMap
print_string MemoryMap_OK_info
; enter unreal mode
call EnterUnrealMode
print_string UnrealMode_OK_info
; FAT Driver setup
call InitFATDriver
print_string InitFATSYS_OK_info
;
; Find first cluster of bootable file
call SearchFATDIR
push dword eax ; save first cluster of bootable file
print_string FileFound_OK_info
pop dword eax
push dword eax ; print Cluster of boot file
call PrintDWORD ; void PrintDWORD(uint32_t dword)
add sp, 0x4
; TODO: using first cluster information, start loading the kernel to memory
; TODO: going to need an elf parser, some unreal mode file buffer functions to move the data
hcf:
ERROR STEVIA_DEBUG_OK
; ##############################
;
; SYSTEM CONFIGURATION FUNCTIONS
;
; ##############################
; Prints a C-Style string (null terminated) using BIOS vga teletype call
; void PrintString(char* buf)
ALIGN 4, db 0x90
PrintString:
__CDECL16_ENTRY
mov di, [bp + 4] ; first arg is char[]
.str_len:
xor cx, cx ; ECX = 0
not cx ; ECX = -1 == 0xFFFF
xor ax, ax ; search for al = 0x0
cld
repne scasb ; deincrement cx while searching for al
not cx ; the inverse of a neg number = abs(x) - 1
dec cx ; CX contains the length of the string - nul byte at end
.print:
mov si, [bp + 4] ; source string
.print_L0:
movzx ax, byte [si]
push ax
call PrintCharacter
add sp, 0x2
inc si
dec cx
jcxz PrintString.endp
jmp PrintString.print_L0 ; Fetch next character from string
.endp:
__CDECL16_EXIT
ret ; Return from procedure
; Prints a single character
; void PrintCharacter(char c);
ALIGN 4, db 0x90
PrintCharacter:
__CDECL16_ENTRY
.func:
movzx ax, byte [bp + 4] ; AL = character c
mov ah, 0x0E ; INT 0x10, AH=0x0E call
mov bx, 0x0007 ; BH = page no. BL =Text attribute 0x07 is lightgrey font on black background
int 0x10 ; call video interrupt
.endp:
__CDECL16_EXIT
ret
; TODO: fix the prolog, epilog and stack usage to confirm with cdecl16
; prints the hex representation of of val
; void PrintDWORD(uint32_t val);
ALIGN 4, db 0x90
PrintDWORD:
__CDECL16_ENTRY
.func:
mov si, IntToHex_table
mov ebx, 16 ; base-16
mov eax, dword [bp + 4] ;val
xor edx, edx
xor cx, cx
.next_digit:
div ebx ; dividend in edx:eax -> quotient in eax, remainder in edx
push dx ; save remainder
inc cx
xor dx, dx
test eax, eax
jnz PrintDWORD.next_digit
.zero_pad:
cmp cx, 0x0008
je PrintDWORD.print_stack
xor ax, ax
push ax
inc cx
jmp PrintDWORD.zero_pad
.print_stack:
pop bx
dec cx
push cx
movzx ax, byte [bx+si+0] ; bx = index into Hex lookup table
push ax
call PrintCharacter
add sp, 0x2
pop cx
jcxz PrintDWORD.endp
jmp PrintDWORD.print_stack
.endp:
__CDECL16_EXIT
ret
; ##############################
;
; SYSTEM CONFIGURATION FUNCTIONS
;
; ##############################
ALIGN 4, db 0x90
EnterUnrealMode:
__CDECL16_ENTRY
.func:
cli ; no interrupts
push ds ; save real mode data/stack selectors
push es
push fs
push gs
push ss
push cs ; save real mode code selector
xor ax, ax ;
pop ax ; save cs to ax to setup far jump
mov word [__UNREAL_SEGMENT], ax
lgdt [((__STAGE2_SEGMENT << 4) + unreal_gdt_info)] ; load unreal gdt
mov eax, cr0
or al,1 ; set pmode bit
mov cr0, eax ; switch to pmode
jmp short $+2
;jmp far 0x0008:EnterUnrealMode.load_cs
db 0xEA ; jmp far imm16:imm16
dw EnterUnrealMode.load_cs ; error_far_ptr
dw 0x0008 ; error_far_seg
.load_cs:
mov bx, 0x10 ; select descriptor 2
mov ds, bx ; 10h = 0001_0000b
mov ss, bx
mov es, bx
mov fs, bx
mov gs, bx ; other data/stack to index 2 (off 0x10)
and al,0xFE ; toggle bit 1 of cr0
mov cr0, eax ; back to realmode
jmp short $+2
;jmp far 0x0008:EnterUnrealMode.unload_cs
db 0xEA ; jmp far imm16:imm16
dw EnterUnrealMode.unload_cs ; error_far_ptr
__UNREAL_SEGMENT:
dw 0x0000 ; error_far_seg
EnterUnrealMode.unload_cs:
pop ss
pop gs
pop fs
pop es
pop ds ; get back old segments
sti
.endp:
__CDECL16_EXIT
ret
end_text:
section .data follows=.text
align 512
begin_data:
; #############
;
; Strings
;
; #############
%define CRLF 0Dh, 0Ah
%macro define_cstr 2
ALIGN 16
%1_cstr:
db %2, 00h
%endmacro
%macro define_info 2
ALIGN 16
%1_info:
db %2, CRLF, 00h
%endmacro
define_info HelloPrompt, "Hello from Stevia Stage2!"
define_info A20_Enabled_OK, "A20 Enabled OK"
define_info MemoryMap_OK, "Memory map OK"
define_info UnrealMode_OK, "Unreal mode OK"
define_info FileFound_OK, "Found SFN entry for bootable binary, first cluster -> "
define_info InitFATSYS_OK, "FAT32 Driver Init..."
define_info SearchFATDIR, "Searching FAT DIR for bootable file..."
define_info NextFATCluster, "Attempting to find next FAT cluster..."
define_info ReadFATCluster, "Attempting to load next FAT"
define_info MaybeFound_Boot, "Maybe found a file...checking..."
define_cstr BootTarget, "BOOT BIN"
ALIGN 16, db 0
BootTarget:
db 'BOOT BIN'
;
; pre-bss init globals (generally const...but there are exceptions)
;
align 8, db 0x00
boot_drive:
db 0x00
align 8, db 0x00
partition_offset:
dw 0x0000
align 8, db 0x00
vbr_fat32_bpb_ptr:
dw 0x0000
align 8, db 0x00
vbr_part_table_ptr:
dw 0x0000
ALIGN 16
IntToHex_table:
db '0123456789ABCDEF'
; see docs/gdt.txt for a quick refresher on GDT
ALIGN 16, db 0
unreal_gdt_info:
unreal_gdt_size: dw (unreal_gdt_end - unreal_gdt_start) - 1
unreal_gdt_ptr: dd ((__STAGE2_SEGMENT << 4) + unreal_gdt_start)
unreal_gdt_start:
; entry 0 (null descriptor)
dq 0 ; first entry is null
; entry 1 (16bit code 64KiB limit)
dd 0x0000FFFF ; Base Address(15:0) 31:16, Segment Limit(15:0) 15:0
db 0x00 ; Base Address 23:16
db 1001_1010b ; Access Byte: Present, ring0, S = 1, executable (1), non-conforming, readable, Accessed
db 0000_0000b ; Flags: GR = 4KiB, attr = <DB/L/Avl>, Granularity = 4KiB & 16:19 of limit
db 0x00 ; Base Address 31:24
; entry 2 (16bit data segment with 4 GiB flat mapping)
dd 0x0000FFFF ; Base Address(15:0) 31:16, Segment Limit(15:0) 15:0
db 0x00 ; Base Address(23:16)
db 1001_0010b ; Access Byte: Present, ring0, S = 1, data (0), non-confirming, writable, present
db 1000_1111b ; Flags: GR = 4KiB, attr = <16-bit/?/?>, Granularity = 4KiB & 16:19 of limit
db 0x00 ; Base Address(31:24)
unreal_gdt_end:
ALIGN 16, db 0
gdt32_info:
gdt32_size: dw (gdt32_end - gdt32_start) - 1
gdt32_ptr: dd ((__STAGE2_SEGMENT << 4) + gdt32_start)
gdt32_start:
dq 0
.gdt32_code:
dw 0xFFFF ; code segment (RX)
dw 0x0000
db 0x00
db 1001_1000b ; Access: readable, executable
db 1100_1111b ; 4KB granularity, 32-bit
db 0x00
.gdt32_data: ; data segment (RW)
dw 0xFFFF
dw 0x0000
db 0x00
db 1001_0010b ; Access: readable, writable
db 1100_1111b ; 4KB granularity, 32-bit
db 0x00
.gdt32_stack: ; Stack segment (RW)
dw 0xFFFF
dw 0x0000
db 0x00
db 1001_0010b ; Access: readable, writable
db 1100_1111b ; 4KB granularity, 32-bit
db 0x00
.gdt32_ro_data: ; Read-only data segment (RO)
dw 0xFFFF
dw 0x0000
db 0x00
db 1001_0000b ; Access: readable, not writable
db 1100_1111b ; 4KB granularity, 32-bit
db 0x00
gdt32_end:
ALIGN 8,db 0x00
BUILD_NASM_VER:
db "Stevia Stage2 built with NASM - ", __NASM_VER__, 00h
ALIGN 8,db 0x00
BUILD_DATETIME:
db 'Assembled - ', __DATE__, ' ', __TIME__, 00h
ALIGN 8,db 0x00
BUILD_GIT_VER:
db __GIT_VER__, 00h
ALIGN 8,db 0x00
BUILD_GIT_HASH:
db __GIT_HASH__, 00h
end_data:
%assign bytes_remaining ((MAX_STAGE2_BYTES - 4) - (($ - $$) + (end_text - begin_text)))
%warning STAGE2 has bytes_remaining bytes remaining for code/data (MAX: MAX_STAGE2_BYTES)
; section start location needs to be a 'critical expression'
; i.e resolvable at build time, we are setting 0x7E00 as the offset since
section .sign start=((MAX_STAGE2_BYTES - 512) + 0x0500)
times ((512 - 4) - ($ -$$) ) db 0x90 ; nop
STAGE2_SIG: dd 0xDEADBEEF ; Signature to mark the end of the stage2
section .bss follows=.sign
begin_bss:
; structures
align 8, resb 1
partition_table resb PartTable_t_size
align 8, resb 1
fat32_bpb resb FAT32_bpb_t_size
fat32_ebpb resb FAT32_ebpb_t_size
align 8, resb 1
fat32_nc_data resb 16
align 8, resb 1
lba_packet resb LBAPkt_t_size
align 8, resb 1
fat32_state:
resb FAT32_State_t_size
align 8, resb 1
SteviaInfo:
resd 4
;
; post-bss init globals
;
;
; large continuous allocations
;
align 16, resb 1
disk_buffer:
resb 512
fat_buffer:
resb 512
dir_buffer:
resb 512
fat_fsinfo:
resb 512
align 16, resb 1
%define BIOSMemoryMap_SIZE 2048
BIOSMemoryMap:
resb 2048
align 512, resb 1
stack_bottom:
resb 1024
stack_top:
end_bss:

File diff suppressed because it is too large Load Diff

190
src/vbr/vbr.nasm Executable file
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@@ -0,0 +1,190 @@
; Copyright (C) 2025 Elaina Claus
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
[BITS 16]
[ORG 0x7C00]
[CPU KATMAI]
[WARNING -reloc-abs-byte]
[WARNING -reloc-abs-word]
[map all vbr.map] ; Yes, we use absolute addresses. surpress these warnings.
%define __STEVIA_VBR
section .text
__ENTRY:
jmp short (init - $$)
nop
; fill BPB area with 0x00 since we skip writing this part to disk
; but we need it for the 'jmp short entry; nop' above
times 33 db 0x00
phy_ebpb_start:
; fill eBPB area with 0x00 since we skip writing this part to disk
times 54 db 0x00
; ###############
;
; Headers/Includes/Definitions
;
; ###############
%include "util/bochs_magic.inc"
%include "cdecl16.inc"
%include "entry.inc"
%include "config.inc"
%include "early_mem.inc"
%include "error_codes.inc"
%include "partition_table.inc"
%include "fat32/fat32_structures.inc"
%undef __STEVIA_DEV_DEBUG
; dl = boot_drive
; si = part_offset
; bx = partition_table location from mbr
ALIGN 4
init:
cli ; We do not want to be interrupted
xor ax, ax
mov ds, ax ; Set segment registers to 0x0000
mov es, ax
mov fs, ax
mov gs, ax
mov ss, ax ; Set Stack Segment to 0
mov sp, end_bss ; Setup stack
mov bp, sp ; base ptr = stack ptr
; zero bss section
mov cx, (end_bss - begin_bss) ; count = bss length
mov ax, begin_bss
mov di, ax ; es:di is dest
xor ax, ax
cld
rep stosb
sub sp, 0x20 ; local varible space
push bp
sti ; all done with inital setup and relocation, reenable interupts
jmp 0:main ; fix up cs:ip just in case and jump to relocated code
; ###############
; Extra/Shared Functions
; ###############
%include "util/kmem_func.nasm"
%include "util/error_func.nasm"
; ###############
; End Section
; ###############
;
; byte boot_drive @ bp - 2
; word part_offset @ bp - 4
; ptr partition_table
ALIGN 4, db 0x90
main:
mov byte [bp - 2], dl ; boot_drive
mov word [bp - 4], si ; part_offset
mov word [bp - 6], bx ; partition_table
.load_fs_data:
mov ax, PartTable_t_size ; count=
push ax
mov ax, [bp - 6] ; src= ptr partition_table
push ax
mov ax, partition_table ; dst=
push ax
call kmemcpy ; copy partition table data
add sp, 0x6
mov ax, (FAT32_bpb_t_size + FAT32_ebpb_t_size) ; size in byte, should be 90 bytes
push ax
mov ax, __ENTRY
push ax
mov ax, fat32_bpb ;
push ax
call kmemcpy ; copy bpb & ebpb to memory
add sp, 0x6
.check_FAT_size: ; we only support a very specific setup of FAT32
mov bx, fat32_bpb
test word [bx + FAT32_bpb_t.unused2_ZERO_word], 0 ; TotSectors16 will not be set if FAT32
jz main.load_stage2
ERROR VBR_ERROR_WRONG_FAT_SIZE
.load_stage2:
; read sectors 1-(MAX_STAGE2_BYTES / 512) to stage2 entry point
movzx ax, byte [bp - 2]
push ax ; drive_num
mov ax, STAGE2_SECTOR_COUNT
push ax ; count
mov dword eax, 0x1
push dword eax ; lba
mov ax, STAGE2_ENTRY
push ax ; offset
xor ax, ax
push ax ; segment = 0
; uint8_t read_stage2_raw(uint16_t buf_segment, uint16_t buf_offset,
; uint32_t lba,
; uint16_t count, uint16_t drive_num)
call read_disk_raw
add sp, 0xC
.enter_stage2:
mov dl, byte [bp - 2] ; byte boot_drive
mov ax, word [bp - 4] ; word part_offset
mov si, partition_table ; ptr partition_table
mov di, fat32_bpb ; ptr fat32_bpb
jmp word 0x0000:STAGE2_ENTRY
; ###############
; Required BIOS function(s)
; ###############
%include 'BIOS/func/ext_read.nasm'
%assign bytes_remaining (420 - ($ - $$))
%warning VBR has bytes_remaining bytes remaining for code (MAX: 420 bytes)
times (510 - ($ - $$)) nop ; Fill the rest of sector with nop
BootSig:
dw 0xAA55 ; Add boot signature at the end of bootloader
section .bss follows=.text
begin_bss:
align 16, resb 1
partition_table resb PartTable_t_size
align 16, resb 1
fat32_bpb resb FAT32_bpb_t_size
fat32_ebpb resb FAT32_ebpb_t_size
align 16, resb 1
fat32_nc_data resb 16
align 16, resb 1
lba_packet resb LBAPkt_t_size
align 512, resb 1
stack_bottom resb 512 ; 512b stack early on
stack_top:
vbr_redzone resb 32
end_bss:

View File

@@ -1,219 +0,0 @@
; Copyright (C) 2020 Bradley Claus
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
[BITS 16]
[ORG 0x7C00]
[CPU KATMAI]
jmp short init
nop
bpb_start:
; fill BPB area with 0x00 since we skip writing this part to disk
; but we need it for the 'jmp short entry; nop' above
times 33 db 0x00
ebpb_start:
; fill BPB area with 0x00 since we skip writing this part to disk
; but we need it for the 'jmp short entry; nop' above
times 54 db 0x00
%include "entry.inc"
init:
cli ; We do not want to be interrupted
xor ax, ax ; 0 AX
mov ds, ax ; Set segment registers to 0
mov es, ax ; *
mov ss, ax ; Set Stack Segment to 0
mov sp, STACK_START ; Setup stack
mov bp, sp ; base ptr = stack ptr
mov bx, VBR_ENTRY ; move BP to the new start of the initial boot sector
jmp 0:main ; fix up cs:ip just in case and jump to relocated code
%include "config.inc"
%include "errors.inc"
%include "memory.inc"
%include "partition_table.inc"
%include "fat32/bpb.inc"
main:
sti ; all done with inital setup and relocation, reenable interupts
mov [bsDriveNumber], dl ; BIOS passes drive number in DL
mov [partition_offset], si ; save passed partition entry offset
.check_FAT_size:
cmp dword [bsSectorHuge], 0 ; SectorsHuge will not be set if FAT12/16
ja main.load_stage2
ERROR VBR_ERROR_WRONG_FAT_SIZE
; read sectors 1-63 to stage2 entry point
.load_stage2:
push bp
mov bp, sp
;uint8_t read_disk_raw(size_t count, uint16_t buf_segment, uint16_t buf_offset,
; uint16_t lower_lower_lba, uint16_t upper_lower_lba)
xor ax, ax
push ax ; upper_lower_lba = 0
mov ax , 1
push ax ; lower_lower_lba = 1
xor ax, ax
push ax ; offset = 0
; 07E0:0
mov ax, STAGE2_ENTRY
shr ax, 4
push ax ; segment = 7E0
mov ax, STAGE2_SECTOR_COUNT
push ax
call read_disk_raw
leave
.check_sig:
mov ax, 0x7E0
mov fs, ax
cmp dword [fs:0x7FFC], 0xDEADBEEF
je main.sig_ok
ERROR VBR_ERROR_NO_SIGNATURE ; no signature present in stage2
.sig_ok:
push bp
mov bp, sp
mov ax, fat32_bpb_SIZE ; size in byte
push ax
mov ax, bpb_start ; start of bpb
push ax
mov ax, fat32_bpb ; defined in memory.inc, destination
push ax
call kmemcpy ; copy bpb to memory
leave
push bp
mov bp, sp
mov ax, fat32_ebpb_SIZE ; 72 bytes of data
push ax
mov ax, ebpb_start ; start of ebpb
push ax
mov ax, fat32_ebpb ; defined in memory.inc, destination
push ax
call kmemcpy ; copy ebpb to memory
leave
mov si, [partition_offset]
mov dl, [bsDriveNumber]
jmp 0:0x7E00
stop:
hlt
jmp short stop
; Wrapper for AH=0x42 INT13h (Extended Read)
;
; BIOS call details
; AH = 42h
; DL = drive number
; DS:SI -> disk address packet
;
; Return:
; CF clear if successful
; AH = 00h
; CF set on error
; AH = error code
; disk address packet's block count field set to number of blocks
; successfully transferred
;
;
; uint8_t read_disk_raw(uint16_t buf_segment, uint16_t buf_offset, uint16_t lower_lower_lba, uint16_t upper_lower_lba)
; bp-0 = call frame
; bp-2 = upper_lower_lba
; bp-4 = lower_lower_lba
; bp-6 = offset
; bp-8 = segment
; bp-10 = count
; bp-12 = ret ptr
read_disk_raw:
push si
; uint8_t* kmemset(void* dest, uint8_t val, size_t len);
push bp
mov bp, sp
mov ax, 0x10
push ax ; len = 16 bytes
xor ax, ax
push ax ; val = 0
mov ax, lba_packet
push ax ; dest = lba_packet address
call kmemset
leave
mov byte [lba_packet + LBAPkt_t.size], 0x10
mov word [lba_packet + LBAPkt_t.xfer_size], STAGE2_SECTOR_COUNT
mov ax, [bp-2]
shl eax, 16
mov ax, [bp-4]
mov dword [lba_packet + LBAPkt_t.lower_lba], eax
mov ax, [bp-6]
mov word [lba_packet + LBAPkt_t.offset], ax
mov ax, [bp-8]
mov word [lba_packet + LBAPkt_t.segment], ax
mov si, lba_packet
mov ah, 0x42
mov dl, byte [bsDriveNumber]
int 0x13
jnc read_disk_raw.endf
ERROR VBR_ERROR_DISK_READ_ERR
.endf:
pop si
ret
; Data
; #############
;
; Locals
;
; #############
; offset from the begining of sector 0 to the active partition.
partition_offset:
dw 0x0000
%assign bytes_remaining (420 - ($ - $$))
%warning VBR has bytes_remaining bytes remaining for code (MAX: 420 bytes)
times (510 - ($ - $$)) nop ; Fill the rest of sector with nop
BootSig:
dw 0xAA55 ; Add boot signature at the end of bootloader