150 Commits

Author SHA1 Message Date
578e9934d8 more bug catching after changing the location of data
also cleanup comment from previous bug
2024-12-19 18:59:34 -05:00
2a6792ae01 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
2c5e5ccbee might have fixed some of the boot_drive issues with ext_read 2024-12-19 13:13:46 -05:00
a830191547 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
38bcd93ced some debuging text for fat32 stuff 2024-10-15 20:37:49 -04:00
f1842d0cbc 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
e085cbbab7 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
915ac4c8ae align to 16 byte bounds and add git info to build 2024-10-15 18:28:06 -04:00
e65220fece 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
6731e03e38 magic debug before touching anything in error printer 2024-10-15 13:31:51 -04:00
47a47051b2 turn off magic debug in mbr/vbr stages 2024-10-15 13:31:32 -04:00
8e2ca06406 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
2b9d0d9946 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
1ce3f67263 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
f81f358987 include disk signature and reserved bytes in part table struct 2024-10-15 12:51:34 -04:00
41db11cc64 ha ha ha, again! 2024-10-15 12:51:02 -04:00
fd7754bc60 I guess wx work again on Debian Trixie? 2024-10-15 12:50:51 -04:00
0f04e682df change entry points (again) 2024-10-14 17:58:43 -04:00
36fcb5faf0 16 KiB stage2 2024-10-14 17:58:30 -04:00
a5296bb438 correct drive_num argument on read_disk_raw 2024-10-14 13:18:41 -04:00
933cccb88e replace text documentation with markdown 2024-10-14 10:44:44 -04:00
ad2d37c63b 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
f32745a7e3 enable magic in the normal bochsrc.txt 2024-10-13 20:51:34 -04:00
8537d6cd5e use bx addressing in read_disk_raw 2024-10-13 20:51:16 -04:00
e57c2cc67d 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
e4b9c5d77f 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
e3a646675f bss for vbr stage 2024-10-13 17:52:28 -04:00
9d33469e32 fixed bss init in mbr 2024-10-13 17:52:09 -04:00
dd1a74bff0 pass location of partition_table structure to vbr 2024-10-13 16:41:39 -04:00
29db27925f initial work on a macro to call read_disk_raw 2024-10-13 16:37:52 -04:00
7f06d47f32 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
4faffbf7fe remove defs for memory locations (moving to bss) 2024-10-13 16:36:55 -04:00
832141efb4 bss convertion for mbr stage 2024-10-13 16:36:11 -04:00
c919144496 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
a62f3de26f unreal gdt tweaks & fixes 2024-10-13 13:22:01 -04:00
0983ec3fd5 remove map files as well 2024-10-12 22:16:17 -04:00
bd40d6d324 relocate code sections to end up with stage2 starting at 0x500 2024-10-12 22:14:47 -04:00
3d3bcc6ea5 reduced stage2 to 24KiB 2024-10-12 22:13:12 -04:00
d1f8ec4a9e follow standard proceedure and reallocate the mbr to 0x600 2024-10-12 21:21:43 -04:00
2fa03c31d7 partially roll back changing the segment to 0x07E0 2024-10-12 20:25:04 -04:00
f535840572 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
54b7a81648 correct typo 2024-10-12 15:39:16 -04:00
1d84f52690 definition corrections in part table stuff 2024-10-12 15:39:04 -04:00
276fe70572 use early_mem.inc 2024-10-12 15:38:47 -04:00
73b42c66fd renamed mem.inc and removed unused items 2024-10-12 15:38:24 -04:00
9656a9465b first version of kmemcpy5/kmemset4 2024-10-12 14:48:26 -04:00
bd80f48b1b use NASM defined size value from structure macro 2024-10-12 12:58:32 -04:00
3fbfcbef53 BIOSMemoryMap is a location in bss now, use lea 2024-10-12 12:58:16 -04:00
31c45051e6 minor cleanup related to memory refactor 2024-10-12 12:57:56 -04:00
a523e17d27 moved stuff that is only referenced in Stage2 to stage2 bss 2024-10-12 12:55:29 -04:00
65e5a83eb4 stage2 is now a multisection binary file
also preparing to move memory globals to bss section.
2024-10-12 11:29:20 -04:00
cd048933ec output symbol maps to ease debuging 2024-10-12 11:28:25 -04:00
e648fd0de6 remove PRINT_FUNC macro...this isn't it chief 2024-10-12 11:27:55 -04:00
2581e50c8b ignore nasm symbol map files 2024-10-12 11:27:20 -04:00
60aaf5cdd9 move far jump setup in EnterUnrealMode to right after we save CS 2024-10-11 21:51:07 -04:00
59678149e0 added debug config for bochs 2024-10-11 21:49:15 -04:00
075e51c8bc move macro definition super early
fix a few mistakes in macro defs
2024-10-11 19:31:31 -04:00
48cd0f742d 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
e5fb1b41eb added bochs debug wrappers 2024-10-11 19:03:27 -04:00
208729ed01 split e820 bios call documentation to its own file under docs/ 2024-10-11 17:20:53 -04:00
086cf9d8ea correct src size in op 2024-10-11 16:52:57 -04:00
095822fa27 inlined ClusterToLBA
removed caller save kludge for now
init first_root_dir_sector from ebpb data
2024-10-11 15:55:24 -04:00
71f13fd6b5 somewhat of a cludge, but added a macro to save all caller saved regs 2024-10-11 14:25:01 -04:00
802d47fbf7 fix passing stage2 wrong data for boot drive 2024-10-11 13:09:17 -04:00
4af0637c7f use kmemset to 0 out fat32_state in InitFATDriver 2024-10-11 13:00:45 -04:00
07197b0d5b reduce proceedure local storage to 16 bytes 2024-10-11 12:59:36 -04:00
056551fdd1 rename file to BOOT.BIN
K.I.S.S.
2024-10-11 12:16:01 -04:00
0aae0616fd more comments to seperate setups 2024-10-11 12:08:09 -04:00
aff631f3db force 1-1 logical to physical sectors
copy our VBR code to backup VBR
2024-10-11 12:04:44 -04:00
a3a768adf4 more error handling in detecting disk image creation
will need ported to macOS sometime
2024-10-11 11:44:04 -04:00
d684d4f11f more error handling for dd writes 2024-10-11 11:31:38 -04:00
75c046f9cd use gs for vesa framebuffer (was fs) 2024-10-08 20:23:16 -04:00
00daf92df5 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
5ab7e70455 Update README.md 2024-10-08 09:08:47 -04:00
6ae68d1a19 ensure 2 byte jmp rel8 thunk to init
surpress reloc abs warnings
corrected include paths/filenames
2024-10-08 08:55:17 -04:00
586f3f0106 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
8301fc20a8 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
4218a08658 force the first jump to init in all stages to be the rel8 version 2024-10-07 20:39:39 -04:00
2bbdaddb68 jmp imm32 vs jmp rel8 (5 bytes vs 2 bytes) 2024-10-06 21:46:32 -04:00
213ea11209 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
e41b597056 surpress some of the relocation warnings for mbr, vbr & stage2 2024-10-06 18:50:32 -04:00
f33ecbcea2 make the Linux bochs run more inline with the Windows one 2024-10-06 15:37:19 -04:00
03a09ed54b Merge pull request #2 from Nivirx/FAT_Refactor
Full refactor for modularization
2024-10-05 20:19:51 -04:00
145e9fbaa9 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
8f95c8f267 tons more work on modularizing the code 2024-10-05 18:55:00 -04:00
5440a1ae61 more modularization and updating date in MIT licence header 2024-10-05 13:35:39 -04:00
d6af15a7a6 typo fix 2024-10-05 12:16:31 -04:00
a4fa48949c Move fat32 and BIOS functions to their own files 2024-10-05 12:04:40 -04:00
0a1123c5b5 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
e162e268c4 remove the dword stack macros and just use the 32bit override 2024-10-05 10:13:18 -04:00
62f036b645 change test kernel stage name
also pointed up a bug in memory.inc
2024-10-04 22:17:35 -04:00
fdbfd811d5 increased disk size and moved bpb/ebpb a bit 2024-10-04 14:26:10 -04:00
d93236d298 some bpb/ebpb tweaks 2024-10-04 11:48:25 -04:00
86fd76e909 remove old kmem functions 2024-10-04 09:57:32 -04:00
3f029e6b4c vbr cdecl overhaul
refactored read_disk_raw to read_stage2_raw
switched to new kmem functions
2024-10-04 09:56:41 -04:00
30c4f1b82c move cdecl macros to nearly the top so early functions can use them 2024-10-04 09:55:45 -04:00
597132df9f 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
63e6f1fac8 kmemset and kmemcpy cdecl16 versions 2024-10-04 09:53:01 -04:00
4ee766304b seperate error code for reading disk in mbr vs vbr vs stage2 2024-10-04 09:52:24 -04:00
d5aa70daf3 add macros to prevent __CDECL16 stuff from being defined multiple times 2024-10-04 09:51:44 -04:00
ec1f40c305 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
36e3bd968a change FAT partition type to 0Ch from 0Bh (W95 FAT32 LBA was CHS/LBA) 2024-10-03 21:00:49 -04:00
36b8869140 add bpb and ebpb reserve area back to vbr.nasm 2024-10-03 21:00:02 -04:00
41b9bf5134 remove this and add it back to vbr.nasm 2024-10-03 20:59:25 -04:00
b96f587921 add forked functions and remove from memory.inc for kmem* 2024-10-03 19:53:11 -04:00
89ebe30ad8 forking kmemset functions for stage2 usage 2024-10-03 19:52:24 -04:00
e98cc41403 forking kmemset functions to be updated later for mbr/vbr 2024-10-03 19:52:00 -04:00
27c41c8b0a update some of the dword stack macros 2024-10-03 19:33:07 -04:00
015def8d52 rough pass on fixing the stack across the board 2024-10-03 19:02:47 -04:00
8157dd301c 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
4d05d2ae4c move E820 function desc to memory.inc 2024-10-03 18:14:04 -04:00
de5b0ddc5d cdecl16 update for EnterUnrealMode 2024-10-03 17:59:29 -04:00
2cfe86efac refactored and validated MemoryMap funciton 2024-10-03 17:41:48 -04:00
c8ca94d7ba some general cleanup & moving the halt to the next point in main() 2024-10-03 16:43:10 -04:00
ac6110aa40 cdecl16 work and cleanup in MemoryMap 2024-10-03 16:34:27 -04:00
46717935a1 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
f691000a31 cdecl16 for EnableA20 ver.1 2024-10-03 15:10:22 -04:00
c524d8801d replace prologs and epilogs in cdecl functions so far 2024-10-03 14:51:43 -04:00
0084747765 added entry & exit macros 2024-10-03 14:46:47 -04:00
929962eaca 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
054f4320ba fixing how the stack works stage1 😳 2024-10-02 12:37:21 -04:00
2f6bd2e2d8 remove comment about CC, see docs/ 2024-10-02 11:59:34 -04:00
7c446ef3b2 load our base headers in the same order as the mbr 2024-10-02 10:26:36 -04:00
2bbfa0931b moved reservation for bpb to a include 2024-10-02 10:25:59 -04:00
8e595e8eba added some clarification on cdecl16 2024-10-02 10:13:45 -04:00
5e4e40f7de removed ata1 from windows bochsrc 2024-10-02 10:13:00 -04:00
6db97e3258 added bxrc config to launch on windows hosts 2024-09-21 14:09:52 -04:00
d42ee1df60 small optimization to error printer
saves us 5 bytes of code (15 overall)
2024-09-21 13:45:15 -04:00
96a8103e11 added debuging 'errors'
also there is special handling for them in error.inc
2024-09-21 13:28:52 -04:00
a5702bd92e partially revert change, sti is still in init 2024-09-21 12:32:49 -04:00
bdc1fc5bf0 added -P option to losetup
this fixes an issue that appeared on WSL2 recently(ish)
2024-09-21 12:04:05 -04:00
1c27b665b0 ignore vscode personal configs 2024-09-21 11:46:36 -04:00
abc79adeb7 remove reallocation in mbr init
also reenable interupts in the init block
2024-09-21 11:45:22 -04:00
7fd4a89d96 Update README.md
updated description to more accurately reflect project status
2024-07-27 09:21:41 -04:00
355ceb49a7 changed extention from .s to .nasm 2023-08-23 10:10:30 -04:00
b590edd3ff enable logging and bump to 128MB of memory 2023-08-23 10:10:13 -04:00
30b71d2e6e updated gitignore 2023-08-23 10:09:49 -04:00
b2857ff9fd clarify that WSL is supported 2023-08-23 07:35:30 -04:00
4e9e58c430 added description for create-disk script 2023-08-22 16:45:22 -04:00
5916b46a9e Update README.md 2023-08-22 16:34:39 -04:00
d162d5dc4c update readme with more information 2023-08-22 16:22:13 -04:00
d4dc46d770 MIT license applied to all project files 2023-08-22 16:03:46 -04:00
ad828ac1f4 use wx interface for config, gui, and debug 2023-08-22 15:56:15 -04:00
5fdde61dd3 remove packaged binaries 2023-08-22 15:55:45 -04:00
90ced63cba small changes to License
🏳️‍⚧️
2023-08-22 14:24:35 -04:00
2c55ed5c04 Update README.md 2023-08-22 10:43:54 -04:00
94a2fb08ca Delete COPYING
Removing GPL-3.0 license.
2023-08-22 10:43:01 -04:00
b9850f7ab9 Create README.md 2023-08-22 10:36:35 -04:00
Elaina Claus
f181f21e41 Merge pull request #1 from Xinnx/add-license-1
Create LICENSE.md
2023-02-28 22:24:40 -05:00
Elaina Claus
309a5fb95c Create LICENSE.md 2023-02-28 22:24:32 -05:00
38 changed files with 2793 additions and 2672 deletions

4
.gitignore vendored
View File

@@ -1,5 +1,9 @@
out/*
build/*
*.img
*.img.gz
*.elf
bx_enh_dbg.ini
stevia-log
.vscode/
*.map

View File

@@ -1,31 +1,39 @@
iso := 'disk.img'
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 +42,30 @@ 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)

125
README.md
View File

@@ -1,85 +1,70 @@
# stevia
# Stevia Bootloader
This is a hobby project that aims to create a simple and lightweight operating system kernel. It is written in Assembly and C, and uses the GNU toolchain and Bochs emulator. The project features (or is hoping to feature):
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.
- A boot loader that loads the kernel from a floppy disk image
- A kernel that implements basic functions, such as printing messages, handling interrupts, and managing memory
- A shell that allows user input and execution of commands
- A simple text editor that can create and edit files
- A calculator that can perform arithmetic operations
- (big maybe) micropython or some other language, cross compiling, etc...
## Features
## Why?
### Currently Implemented
I enjoy bare metal programing and I have an old Dell system with a Pentium 3, I did this mostly to learn how to write a legacy style bootloader (I am also kinda working on a UEFI bootloader/utility as well!)
- **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
To build and run this project, you need to have the following tools installed:
### Prerequisites
- A host system running Linux, macOS (should work 🤷‍♀️), or Windows 11 with WSL2/WSLg
- GNU Binutils
- GNU GCC
- GNU Make
- NASM
- Bochs (for testing, project might run on other virtuization/emulation platforms, I target the Pentium 3 Era with this project)
To build and run Stevia, you will need the following tools installed on your system:
To build the project, run `make` in the root directory. This will generate a floppy disk image named `stevia.img` that contains the boot loader and the kernel.
- **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.
To run the project, run `bochs -f bochsrc.txt` in the root directory. This will launch the Bochs emulator and load the floppy disk image. You should see the boot loader message, followed by the kernel message, and then the shell prompt.
### Building and Running
To exit the emulator, press `Ctrl+C` in the terminal where you launched Bochs.
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
```
To run the project on real hardware I use a SD card to IDE interface for my test system which is a ~700Mhz P3 with 256 MB of ram. You will need to write the 'stevia.img' to the disk with 'dd'. On real hardware you may encounter issues that are not accounted for since most of the development happens on bochs, please report any issues you encounter.
## 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.md](^2^) file for details.
### mbr/mbr.s
This file contains the code for a Master Boot Record (MBR) that attempts to find an active partition to load. The CPU is assumed to be in 16-bit real mode at this point and the bios has loaded the 1st sector of the disk (512 bytes) to 0x0000:0x7C00. First the mbr code relocates from 0x7C00 to 0x0600 and then jumps to the entry point. the loader attempts to load the first active partition it can find and loads the vbr to 0x7c00 (512 bytes) and then jumps to 0x0000:0x7C00. It is written in Assembly and uses BIOS interrupts to read sectors from disk.[^note]
### vbr/vbr.s
This file contains the code for a Volume Boot Record (VBR) that loads the stage2 loader code from the booted disk. It reads disk sectors 1-63 into memory to STAGE2_ENTRY(defaults to 0x7E00 in config.inc) this currently allows for stevia to load up to 32KiB of code to perform bootloader duties. It is written in Assembly and uses BIOS interrupts to read sectors from disk.[^note]
### stage2/stage2.s
This file contains the code for a second-stage boot loader that loads additional modules from disk, performs some system sanity checks, and provides a simple boot interface for options/configuration. It is written in Assembly and uses BIOS interrupts to read sectors from disk.[^note]
### miniboot32/BOOT_386.s
This file contains the code for a 32-bit binary that can be loaded and ran with stevia as a mini demo. It is written in Assembly.[^note]
### scripts/create-disk.sh
This script creates a disk image file for stevia. The disk image file can be used to boot stevia on an emulator or a real machine.
#### Requirements
- Bash shell
- Root privileges
- dd utility
- sfdisk utility (for Linux) or hdiutil & util-linux utility (for macOS, util-linux is needed for sfdisk because hdiutil only creates hybrid disks on newer versions afaik)
- newfs_msdos utility (for macOS)
- mkfs.vfat utility (for Linux)
#### Usage
Run the script as root (or just allow the make script to do its business):
```bash
sudo ./create_disk_image.sh
```
The script will create a disk image file named `disk.img` in the current directory. The disk image file will have the following characteristics:
- Size: 128 MiB
- Partition table: DOS
- Partition 1: FAT32, bootable, starts at sector 2048, contains the boot32 boot test file (`BOOT_386.bin`)
- Boot code: MBR (`mbr.bin`), VBR (`vbr.bin`), stage2 (sectors 1-63) (`stage2.bin`)
The script will also copy the necessary files from the `build` directory to the disk image file. If the files are not found, the script will exit with an error.
[^note]: **Note:** Please note that the assembly code is strictly targeting the Pentium 3 Katmai uArch, but it might run elsewhere. Your mileage may vary.
This project is licensed under the MIT License. See the [LICENSE](LICENSE) file for more details.

52
bochsrc.bxrc Normal file
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# 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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# 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
config_interface: wx
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: wx
memory: host=64, guest=64
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=0
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
parport1: enabled=false
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
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# **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 |

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@@ -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])

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include/BIOS/BIOS_SYS.inc Normal file
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; Copyright (c) 2024 Elaina Claus
;
; Permission is hereby granted, free of charge, to any person obtaining a copy
; of this software and associated documentation files (the "Software"), to deal
; in the Software without restriction, including without limitation the rights
; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
; copies of the Software, and to permit persons to whom the Software is
; furnished to do so, subject to the following conditions:
;
; The above copyright notice and this permission notice shall be included in all
; copies or substantial portions of the Software.
;
; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
; SOFTWARE.
%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 +1,88 @@
; Copyright (c) 2024 Elaina Claus
;
; Permission is hereby granted, free of charge, to any person obtaining a copy
; of this software and associated documentation files (the "Software"), to deal
; in the Software without restriction, including without limitation the rights
; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
; copies of the Software, and to permit persons to whom the Software is
; furnished to do so, subject to the following conditions:
;
; The above copyright notice and this permission notice shall be included in all
; copies or substantial portions of the Software.
;
; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
; SOFTWARE.
%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 +1,144 @@
; Copyright (c) 2024 Elaina Claus
;
; Permission is hereby granted, free of charge, to any person obtaining a copy
; of this software and associated documentation files (the "Software"), to deal
; in the Software without restriction, including without limitation the rights
; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
; copies of the Software, and to permit persons to whom the Software is
; furnished to do so, subject to the following conditions:
;
; The above copyright notice and this permission notice shall be included in all
; copies or substantial portions of the Software.
;
; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
; SOFTWARE.
%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) 2024 Elaina Claus
;
; Permission is hereby granted, free of charge, to any person obtaining a copy
; of this software and associated documentation files (the "Software"), to deal
; in the Software without restriction, including without limitation the rights
; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
; copies of the Software, and to permit persons to whom the Software is
; furnished to do so, subject to the following conditions:
;
; The above copyright notice and this permission notice shall be included in all
; copies or substantial portions of the Software.
;
; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
; SOFTWARE.
%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, [bp + 8]
mov dword [bx + LBAPkt_t.lower_lba], eax
mov ax, [bp + 6]
mov word [bx + LBAPkt_t.offset], ax
movzx ax, byte [bp + 4]
mov word [bx + LBAPkt_t.segment], ax
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 +1,60 @@
; Copyright (c) 2024 Elaina Claus
;
; Permission is hereby granted, free of charge, to any person obtaining a copy
; of this software and associated documentation files (the "Software"), to deal
; in the Software without restriction, including without limitation the rights
; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
; copies of the Software, and to permit persons to whom the Software is
; furnished to do so, subject to the following conditions:
;
; The above copyright notice and this permission notice shall be included in all
; copies or substantial portions of the Software.
;
; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
; SOFTWARE.
%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

57
include/cdecl16.inc Normal file
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@@ -0,0 +1,57 @@
; Copyright (c) 2024 Elaina Claus
;
; Permission is hereby granted, free of charge, to any person obtaining a copy
; of this software and associated documentation files (the "Software"), to deal
; in the Software without restriction, including without limitation the rights
; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
; copies of the Software, and to permit persons to whom the Software is
; furnished to do so, subject to the following conditions:
;
; The above copyright notice and this permission notice shall be included in all
; copies or substantial portions of the Software.
;
; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
; SOFTWARE.
%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

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@@ -1,4 +1,4 @@
; Copyright (c) 2023 Elaina Claus
; Copyright (c) 2024 Elaina Claus
;
; Permission is hereby granted, free of charge, to any person obtaining a copy
; of this software and associated documentation files (the "Software"), to deal
@@ -18,8 +18,12 @@
; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
; SOFTWARE.
%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

33
include/early_mem.inc Executable file
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@@ -0,0 +1,33 @@
; Copyright (c) 2024 Elaina Claus
;
; Permission is hereby granted, free of charge, to any person obtaining a copy
; of this software and associated documentation files (the "Software"), to deal
; in the Software without restriction, including without limitation the rights
; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
; copies of the Software, and to permit persons to whom the Software is
; furnished to do so, subject to the following conditions:
;
; The above copyright notice and this permission notice shall be included in all
; copies or substantial portions of the Software.
;
; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
; SOFTWARE.
%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

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@@ -1,4 +1,4 @@
; Copyright (c) 2023 Elaina Claus
; Copyright (c) 2024 Elaina Claus
;
; Permission is hereby granted, free of charge, to any person obtaining a copy
; of this software and associated documentation files (the "Software"), to deal
@@ -18,9 +18,11 @@
; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
; SOFTWARE.
%ifndef __INC_ENTRY
; 8KiB from 0x2500 -> 0x500
%define STACK_START 0x2500
%define MBR_ENTRY 0x7A00
%define MBR_ENTRY 0x8C00
%define VBR_ENTRY 0x7C00
%define STAGE2_ENTRY 0x7E00
%define STAGE2_ENTRY 0x0500
%endif
%define __INC_ENTRY

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@@ -1,4 +1,4 @@
; Copyright (c) 2023 Elaina Claus
; Copyright (c) 2024 Elaina Claus
;
; Permission is hereby granted, free of charge, to any person obtaining a copy
; of this software and associated documentation files (the "Software"), to deal
@@ -18,6 +18,7 @@
; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
; SOFTWARE.
%ifndef __INC_ERROR_CODES
; Errors
; 12 Errors, 5 in use
@@ -32,7 +33,7 @@
%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'
@@ -48,7 +49,7 @@
%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'
@@ -59,9 +60,9 @@
%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_FAT32_NCLUS_CFDIVZ 'K'
%define STAGE2_FAT32_CLS2LBA_CF 'L'
%define STAGE2_FAT32_INIT_CF 'M'
%define STAGE2_ERROR_RESERVED_N 'N'
%define STAGE2_ERROR_RESERVED_O 'O'
%define STAGE2_ERROR_RESERVED_P 'P'
@@ -71,30 +72,12 @@
%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

323
include/fat32/FAT32_SYS.inc Normal file
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@@ -0,0 +1,323 @@
; Copyright (c) 2024 Elaina Claus
;
; Permission is hereby granted, free of charge, to any person obtaining a copy
; of this software and associated documentation files (the "Software"), to deal
; in the Software without restriction, including without limitation the rights
; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
; copies of the Software, and to permit persons to whom the Software is
; furnished to do so, subject to the following conditions:
;
; The above copyright notice and this permission notice shall be included in all
; copies or substantial portions of the Software.
;
; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
; SOFTWARE.
%ifndef __INC_FAT32_SYS
%include "partition_table.inc"
%include "fat32/bpb_offset_bx.inc"
%include "fat32/fat32_structures.inc"
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 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 [fat32_state + FAT32_State_t.active_drive_lba_32], eax
.calc_first_fat:
movzx eax, word [fat32_bpb + FAT32_bpb_t.reserved_sectors_16] ; first fat from start of partition
add eax, dword [fat32_state + FAT32_State_t.active_drive_lba_32] ; calculate offset from start of drive
mov dword [fat32_state + FAT32_State_t.first_fat_sector_32], eax
.calc_total_fat:
mov ebx, dword [fat32_ebpb + FAT32_ebpb_t.sectors_per_fat_32]
movzx eax, byte [fat32_bpb + FAT32_bpb_t.fat_count_8]
mul ebx ; 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 [fat32_state + FAT32_State_t.fat_size_32], eax
.calc_first_data:
mov edx, dword [fat32_state + FAT32_State_t.first_fat_sector_32]
add eax, edx
mov dword [fat32_state + FAT32_State_t.first_data_sector_32], eax
.get_first_root_dir:
mov eax, [fat32_ebpb + FAT32_ebpb_t.root_dir_cluster_32]
mov dword [fat32_state + FAT32_State_t.first_root_dir_sector_32], eax ; this only works when 1 cluster = 1 sector
mov dword [fat32_state + FAT32_State_t.active_dir_cluster_32], eax
.endp:
__CDECL16_EXIT
ret
.error:
ERROR STAGE2_FAT32_INIT_CF
; 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_cstr
.load_first_dir:
mov eax, dword [fat32_state + FAT32_State_t.active_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 [fat32_state + FAT32_State_t.active_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, [fat32_state + FAT32_State_t.active_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
.parse_dir:
print_string MaybeFound_Boot_INFO_cstr
.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_str ; 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_cstr
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
.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
mov edx, 0xffff_0000
and edx, eax
shr edx, 16
xchg si, di ; switch to fat32_bpb in si
mov cx, word [si + FAT32_bpb_t.bytes_per_sector_16]
xchg si, di
cmp edx, 0
je NextCluster.error_cfdivz
div cx ; DX:AX / cx = fat_sector - first_fat_sector in AX
; DX = remainder (fat_offset mod sector_size)
mov ecx, 0x0000_ffff
and edx, ecx
mov dword [si + FAT32_NextClusterData_t.entry_offset], edx
xchg si, di ; switch to fat32_bpb in si
mov ecx, dword [si + FAT32_State_t.first_fat_sector_32]
xchg si, di
mov edx, 0x0000ffff
and eax, edx
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
; uint32_t ClusterToLBA(uint32_t cluster)
ALIGN 4, db 0x90
ClusterToLBA:
__CDECL16_ENTRY
.func:
mov dword eax, [bp + 4]
sub eax, 2
movzx edx, byte [fat32_bpb + FAT32_bpb_t.sectors_per_cluster_8]
mul edx
jc ClusterToLBA.error
add eax, dword [fat32_state + FAT32_State_t.first_data_sector_32]
; eax contains the LBA now
.endp:
__CDECL16_EXIT
ret
.error:
ERROR STAGE2_FAT32_CLS2LBA_CF
; bp - 2 - byte boot_drive
; uint8_t ReadFATCluster(uint16_t seg, uint16_t offset, uint32_t cluster)
ALIGN 4, db 0x90
ReadFATCluster:
__CDECL16_ENTRY
.func:
print_string ReadFATCluster_INFO_cstr
xor ax, ax
mov al, byte [boot_drive]
push ax
mov ax, 0x1 ; count = 1
push ax
mov eax, dword [bp + 8]
push dword eax
call ClusterToLBA
add sp, 0x4
; eax contains the LBA now
push dword eax ; lba = ClusterToLBA(..)
mov ax, fat_buffer ; offset = fat_buffer (in mem.inc)
push ax
xor ax, ax ; segment = 0x0000, our buffer is in the first 64 KiB
push ax
; 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
.endp:
__CDECL16_EXIT
ret
%endif
%define __INC_FAT32_SYS

View File

@@ -1,4 +1,4 @@
; Copyright (c) 2023 Elaina Claus
; Copyright (c) 2024 Elaina Claus
;
; Permission is hereby granted, free of charge, to any person obtaining a copy
; of this software and associated documentation files (the "Software"), to deal
@@ -18,6 +18,7 @@
; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
; SOFTWARE.
%ifndef __INC_BPD_OFFSET_BX
; BPB Information
; Off. Hex Off. Size Description
@@ -89,3 +90,6 @@
%define bsVolumeLabel bx+0x47
%define bsSystemIdent bx+0x52
;-- End EBPB
%endif
%define __INC_BPD_OFFSET_BX

View File

@@ -18,6 +18,7 @@
; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
; SOFTWARE.
%ifndef __INC_FAT32_STRUCT
; ## FAT32 Info ##
; total_sectors = bsSectorsHuge
@@ -62,6 +63,7 @@
; resulting in a value which does not fit in the Number of Sectors entry at 0x13.
struc FAT32_bpb_t
.reserved_init resb 3
.ident_8 resb 8
.bytes_per_sector_16 resb 2
.sectors_per_cluster_8 resb 1
@@ -230,4 +232,5 @@ endstruc
; LFN == RO | HIDDEN | SYSTEM | VOLID == 0x0F
%define FAT32_ATTR_LFN 0x0F
%endif
%define __INC_FAT32_STRUCT

View File

@@ -1,213 +0,0 @@
; Copyright (c) 2023 Elaina Claus
;
; Permission is hereby granted, free of charge, to any person obtaining a copy
; of this software and associated documentation files (the "Software"), to deal
; in the Software without restriction, including without limitation the rights
; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
; copies of the Software, and to permit persons to whom the Software is
; furnished to do so, subject to the following conditions:
;
; The above copyright notice and this permission notice shall be included in all
; copies or substantial portions of the Software.
;
; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
; SOFTWARE.
; ## 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

@@ -1,4 +1,4 @@
; Copyright (c) 2023 Elaina Claus
; Copyright (c) 2024 Elaina Claus
;
; Permission is hereby granted, free of charge, to any person obtaining a copy
; of this software and associated documentation files (the "Software"), to deal
@@ -18,6 +18,8 @@
; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
; SOFTWARE.
%ifndef __INC_PART_TABLE
; Partition table entry format
; Off. Size. Description
;0x00 1 Drive attributes (bit 7 set = active or bootable)
@@ -32,32 +34,18 @@ 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 +1,56 @@
; Copyright (c) 2024 Elaina Claus
;
; Permission is hereby granted, free of charge, to any person obtaining a copy
; of this software and associated documentation files (the "Software"), to deal
; in the Software without restriction, including without limitation the rights
; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
; copies of the Software, and to permit persons to whom the Software is
; furnished to do so, subject to the following conditions:
;
; The above copyright notice and this permission notice shall be included in all
; copies or substantial portions of the Software.
;
; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
; SOFTWARE.
%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 +1,50 @@
; Copyright (c) 2024 Elaina Claus
;
; Permission is hereby granted, free of charge, to any person obtaining a copy
; of this software and associated documentation files (the "Software"), to deal
; in the Software without restriction, including without limitation the rights
; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
; copies of the Software, and to permit persons to whom the Software is
; furnished to do so, subject to the following conditions:
;
; The above copyright notice and this permission notice shall be included in all
; copies or substantial portions of the Software.
;
; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
; SOFTWARE.
%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 +1,58 @@
; Copyright (c) 2024 Elaina Claus
;
; Permission is hereby granted, free of charge, to any person obtaining a copy
; of this software and associated documentation files (the "Software"), to deal
; in the Software without restriction, including without limitation the rights
; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
; copies of the Software, and to permit persons to whom the Software is
; furnished to do so, subject to the following conditions:
;
; The above copyright notice and this permission notice shall be included in all
; copies or substantial portions of the Software.
;
; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
; SOFTWARE.
%ifndef __INC_KMEM_FUNC
%include 'cdecl16.inc'
; uint8_t* kmemset_byte(void* dst, uint8_t val, uint16_t len);
ALIGN 4, db 0x90
kmemset:
__CDECL16_ENTRY
.func:
mov cx, [bp + 8] ; size_t len
mov al, [bp + 6] ; uint8_t val
mov di, [bp + 4] ; void * dst
cld
rep stosb
mov ax, di ; return pointer to dest
.endp:
__CDECL16_EXIT
ret
; uint8_t* kmemset(uint8_t* dest, uint8_t* src, uint8_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 +1,53 @@
; Copyright (c) 2024 Elaina Claus
;
; Permission is hereby granted, free of charge, to any person obtaining a copy
; of this software and associated documentation files (the "Software"), to deal
; in the Software without restriction, including without limitation the rights
; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
; copies of the Software, and to permit persons to whom the Software is
; furnished to do so, subject to the following conditions:
;
; The above copyright notice and this permission notice shall be included in all
; copies or substantial portions of the Software.
;
; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
; SOFTWARE.
%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 +1,47 @@
; Copyright (c) 2024 Elaina Claus
;
; Permission is hereby granted, free of charge, to any person obtaining a copy
; of this software and associated documentation files (the "Software"), to deal
; in the Software without restriction, including without limitation the rights
; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
; copies of the Software, and to permit persons to whom the Software is
; furnished to do so, subject to the following conditions:
;
; The above copyright notice and this permission notice shall be included in all
; copies or substantial portions of the Software.
;
; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
; SOFTWARE.
%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

@@ -21,25 +21,40 @@
# SOFTWARE.
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
@@ -47,33 +62,68 @@ 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 $mount_point ]; then
@@ -81,25 +131,39 @@ if [[ "$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
@@ -159,7 +223,7 @@ 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
@@ -189,7 +253,7 @@ 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

View File

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

205
src/mbr/mbr.nasm Executable file
View File

@@ -0,0 +1,205 @@
; Copyright (c) 2023 Elaina Claus
;
; Permission is hereby granted, free of charge, to any person obtaining a copy
; of this software and associated documentation files (the "Software"), to deal
; in the Software without restriction, including without limitation the rights
; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
; copies of the Software, and to permit persons to whom the Software is
; furnished to do so, subject to the following conditions:
;
; The above copyright notice and this permission notice shall be included in all
; copies or substantial portions of the Software.
;
; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
; SOFTWARE.
[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

@@ -1,244 +0,0 @@
; Copyright (c) 2023 Elaina Claus
;
; Permission is hereby granted, free of charge, to any person obtaining a copy
; of this software and associated documentation files (the "Software"), to deal
; in the Software without restriction, including without limitation the rights
; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
; copies of the Software, and to permit persons to whom the Software is
; furnished to do so, subject to the following conditions:
;
; The above copyright notice and this permission notice shall be included in all
; copies or substantial portions of the Software.
;
; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
; SOFTWARE.
[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

View File

@@ -1,559 +0,0 @@
; Copyright (c) 2023 Elaina Claus
;
; Permission is hereby granted, free of charge, to any person obtaining a copy
; of this software and associated documentation files (the "Software"), to deal
; in the Software without restriction, including without limitation the rights
; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
; copies of the Software, and to permit persons to whom the Software is
; furnished to do so, subject to the following conditions:
;
; The above copyright notice and this permission notice shall be included in all
; copies or substantial portions of the Software.
;
; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
; SOFTWARE.
[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

99
src/miniboot32/BOOTi686.nasm Executable file
View File

@@ -0,0 +1,99 @@
; Copyright (c) 2023 Elaina Claus
;
; Permission is hereby granted, free of charge, to any person obtaining a copy
; of this software and associated documentation files (the "Software"), to deal
; in the Software without restriction, including without limitation the rights
; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
; copies of the Software, and to permit persons to whom the Software is
; furnished to do so, subject to the following conditions:
;
; The above copyright notice and this permission notice shall be included in all
; copies or substantial portions of the Software.
;
; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
; SOFTWARE.
[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

564
src/stage2/stage2.nasm Executable file
View File

@@ -0,0 +1,564 @@
; Copyright (c) 2023 Elaina Claus
;
; Permission is hereby granted, free of charge, to any person obtaining a copy
; of this software and associated documentation files (the "Software"), to deal
; in the Software without restriction, including without limitation the rights
; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
; copies of the Software, and to permit persons to whom the Software is
; furnished to do so, subject to the following conditions:
;
; The above copyright notice and this permission notice shall be included in all
; copies or substantial portions of the Software.
;
; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
; SOFTWARE.
[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_cstr
; enable A20 gate
call EnableA20
print_string A20_Enabled_OK_cstr
; get system memory map
call GetMemoryMap
print_string MemoryMap_OK_cstr
; enter unreal mode
call EnterUnrealMode
print_string UnrealMode_OK_cstr
; FAT Driver setup
call InitFATDriver
print_string InitFATSYS_OK_cstr
;
; Find first cluster of bootable file
call SearchFATDIR
push dword eax ; save first cluster of bootable file
print_string FileFound_OK_cstr
pop dword eax
push dword eax ; print Cluster of boot file
call PrintDWORD ; void PrintDWORD(uint32_t dword)
print_string NewLine_cstr
; 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:
mov ax, [bp + 4] ; c
mov dx, 0x00ff
and ax, dx
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:
lea 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
;
; #############
%macro define_str 2
ALIGN 16
%1_str:
db %2
%define str_len %strlen(%2) ; string
%1_str_len:
dd str_len
%endmacro
; TODO: technically this is a cstr but it splices a return and newline on the end
; TODO: this probably should be seperated out and the printing functionality should
; TODO: place that newline and return
%macro define_cstr 2
%define CRLF_NUL 0Dh, 0Ah, 00h
ALIGN 16
%1_cstr:
db %2, CRLF_NUL
%endmacro
define_cstr HelloPrompt, "Hello from Stevia Stage2!"
define_cstr A20_Enabled_OK, "A20 Enabled OK"
define_cstr MemoryMap_OK, "Memory map OK"
define_cstr UnrealMode_OK, "Unreal mode OK"
define_cstr FileFound_OK, "Found SFN entry for bootable binary, first cluster -> "
define_cstr InitFATSYS_OK, "FAT32 Driver Init..."
define_cstr SearchFATDIR_INFO, "Searching FAT DIR for bootable file..."
define_cstr NextFATCluster_INFO, "Attempting to find next FAT cluster..."
define_cstr ReadFATCluster_INFO, "Attempting to load next FAT"
define_cstr MaybeFound_Boot_INFO, "Maybe found a file...checking..."
define_cstr NewLine, ""
define_str BootTarget, "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:

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195
src/vbr/vbr.nasm Executable file
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; Copyright (c) 2023 Elaina Claus
;
; Permission is hereby granted, free of charge, to any person obtaining a copy
; of this software and associated documentation files (the "Software"), to deal
; in the Software without restriction, including without limitation the rights
; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
; copies of the Software, and to permit persons to whom the Software is
; furnished to do so, subject to the following conditions:
;
; The above copyright notice and this permission notice shall be included in all
; copies or substantial portions of the Software.
;
; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
; SOFTWARE.
[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
cmp dword [bx + FAT32_bpb_t.sector_count_32], 0 ; SectorsHuge will not be set if FAT12/16
ja 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:

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@@ -1,225 +0,0 @@
; Copyright (c) 2023 Elaina Claus
;
; Permission is hereby granted, free of charge, to any person obtaining a copy
; of this software and associated documentation files (the "Software"), to deal
; in the Software without restriction, including without limitation the rights
; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
; copies of the Software, and to permit persons to whom the Software is
; furnished to do so, subject to the following conditions:
;
; The above copyright notice and this permission notice shall be included in all
; copies or substantial portions of the Software.
;
; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
; SOFTWARE.
[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