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GNU GENERAL PUBLIC LICENSE
Version 3, 29 June 2007
Copyright (C) 2007 Free Software Foundation, Inc. <https://fsf.org/>
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The hypothetical commands `show w' and `show c' should show the appropriate
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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_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))
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
all: $(iso) $(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 $(build_dir)/*
@rm -rvf $(iso)
run: $(iso)
@sudo qemu-system-i386 $(qemu_args) -hda $(iso)
run_bochs: $(iso)
@bochs -q
iso: $(iso)
@file disk.img
build/%.bin: src/mbr/%.s
@mkdir -p $(shell dirname $@)
@nasm -i$(include) -Wall -f bin $< -o $@
build/%.bin: src/vbr/%.s
@mkdir -p $(shell dirname $@)
@nasm -i$(include) -Wall -f bin $< -o $@
build/%.bin: src/stage2/%.s
@mkdir -p $(shell dirname $@)
@nasm -i$(include) -Wall -f bin $< -o $@
build/%.bin: src/miniboot32/%.s
@mkdir -p $(shell dirname $@)
@nasm -i$(include) -Wall -f bin $< -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

0
bin/.keepdir Executable file
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BIN
bin/bios.bin Executable file

Binary file not shown.

BIN
bin/vgabios.bin Executable file

Binary file not shown.

40
bochsrc.txt Executable file
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# 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: textconfig
display_library: x
memory: host=32, guest=32
boot: disk
floppy_bootsig_check: disabled=0
# no floppya
# 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-slave: type=none
ata1: enabled=false
ata2: enabled=false
ata3: enabled=false
pci: enabled=1, chipset=i440fx
vga: extension=vbe, update_freq=5, realtime=1
cpu: count=1:1:1, ips=1000000, quantum=16, model=p3_katmai, reset_on_triple_fault=1, cpuid_limit_winnt=0, ignore_bad_msrs=1, mwait_is_nop=0
print_timestamps: enabled=0
debugger_log: -
magic_break: enabled=0
port_e9_hack: enabled=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=250, paste_delay=100000, user_shortcut=none
mouse: type=ps2, enabled=false, toggle=ctrl+mbutton
speaker: enabled=true, mode=system
parport1: enabled=true, file=none
parport2: enabled=false
com1: enabled=true, mode=null
com2: enabled=false
com3: enabled=false
com4: enabled=false

10
debug/8086_gdb/.gdbinit Executable file
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@@ -0,0 +1,10 @@
set tdesc filename target.xml
set arch i8086
set disassembly-flavor intel
target remote localhost:1234
display/i $cs*16+$pc
b *0x7c00
set $cs = 0xf000
set $pc = 0xfff0
c

112
debug/8086_gdb/target.xml Executable file
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@@ -0,0 +1,112 @@
<?xml version="1.0"?>
<!-- Copyright (C) 2010-2017 Free Software Foundation, Inc.
Copying and distribution of this file, with or without modification,
are permitted in any medium without royalty provided the copyright
notice and this notice are preserved. -->
<target/>
<!DOCTYPE target SYSTEM "gdb-target.dtd">
<architecture>i8086</architecture>
<feature name="org.gnu.gdb.i386.core">
<flags id="i386_eflags" size="4">
<field name="CF" start="0" end="0"/>
<field name="" start="1" end="1"/>
<field name="PF" start="2" end="2"/>
<field name="AF" start="4" end="4"/>
<field name="ZF" start="6" end="6"/>
<field name="SF" start="7" end="7"/>
<field name="TF" start="8" end="8"/>
<field name="IF" start="9" end="9"/>
<field name="DF" start="10" end="10"/>
<field name="OF" start="11" end="11"/>
<field name="NT" start="14" end="14"/>
<field name="RF" start="16" end="16"/>
<field name="VM" start="17" end="17"/>
<field name="AC" start="18" end="18"/>
<field name="VIF" start="19" end="19"/>
<field name="VIP" start="20" end="20"/>
<field name="ID" start="21" end="21"/>
</flags>
<reg name="eax" bitsize="32" type="int32"/>
<reg name="ecx" bitsize="32" type="int32"/>
<reg name="edx" bitsize="32" type="int32"/>
<reg name="ebx" bitsize="32" type="int32"/>
<reg name="esp" bitsize="32" type="data_ptr"/>
<reg name="ebp" bitsize="32" type="data_ptr"/>
<reg name="esi" bitsize="32" type="int32"/>
<reg name="edi" bitsize="32" type="int32"/>
<reg name="eip" bitsize="32" type="code_ptr"/>
<reg name="eflags" bitsize="32" type="i386_eflags"/>
<reg name="cs" bitsize="32" type="int32"/>
<reg name="ss" bitsize="32" type="int32"/>
<reg name="ds" bitsize="32" type="int32"/>
<reg name="es" bitsize="32" type="int32"/>
<reg name="fs" bitsize="32" type="int32"/>
<reg name="gs" bitsize="32" type="int32"/>
<reg name="st0" bitsize="80" type="i387_ext"/>
<reg name="st1" bitsize="80" type="i387_ext"/>
<reg name="st2" bitsize="80" type="i387_ext"/>
<reg name="st3" bitsize="80" type="i387_ext"/>
<reg name="st4" bitsize="80" type="i387_ext"/>
<reg name="st5" bitsize="80" type="i387_ext"/>
<reg name="st6" bitsize="80" type="i387_ext"/>
<reg name="st7" bitsize="80" type="i387_ext"/>
<reg name="fctrl" bitsize="32" type="int" group="float"/>
<reg name="fstat" bitsize="32" type="int" group="float"/>
<reg name="ftag" bitsize="32" type="int" group="float"/>
<reg name="fiseg" bitsize="32" type="int" group="float"/>
<reg name="fioff" bitsize="32" type="int" group="float"/>
<reg name="foseg" bitsize="32" type="int" group="float"/>
<reg name="fooff" bitsize="32" type="int" group="float"/>
<reg name="fop" bitsize="32" type="int" group="float"/>
</feature>
<feature name="org.gnu.gdb.i386.32bit.sse">
<vector id="v4f" type="ieee_single" count="4"/>
<vector id="v2d" type="ieee_double" count="2"/>
<vector id="v16i8" type="int8" count="16"/>
<vector id="v8i16" type="int16" count="8"/>
<vector id="v4i32" type="int32" count="4"/>
<vector id="v2i64" type="int64" count="2"/>
<union id="vec128">
<field name="v4_float" type="v4f"/>
<field name="v2_double" type="v2d"/>
<field name="v16_int8" type="v16i8"/>
<field name="v8_int16" type="v8i16"/>
<field name="v4_int32" type="v4i32"/>
<field name="v2_int64" type="v2i64"/>
<field name="uint128" type="uint128"/>
</union>
<flags id="i386_mxcsr" size="4">
<field name="IE" start="0" end="0"/>
<field name="DE" start="1" end="1"/>
<field name="ZE" start="2" end="2"/>
<field name="OE" start="3" end="3"/>
<field name="UE" start="4" end="4"/>
<field name="PE" start="5" end="5"/>
<field name="DAZ" start="6" end="6"/>
<field name="IM" start="7" end="7"/>
<field name="DM" start="8" end="8"/>
<field name="ZM" start="9" end="9"/>
<field name="OM" start="10" end="10"/>
<field name="UM" start="11" end="11"/>
<field name="PM" start="12" end="12"/>
<field name="FZ" start="15" end="15"/>
</flags>
<reg name="xmm0" bitsize="128" type="vec128" regnum="32"/>
<reg name="xmm1" bitsize="128" type="vec128"/>
<reg name="xmm2" bitsize="128" type="vec128"/>
<reg name="xmm3" bitsize="128" type="vec128"/>
<reg name="xmm4" bitsize="128" type="vec128"/>
<reg name="xmm5" bitsize="128" type="vec128"/>
<reg name="xmm6" bitsize="128" type="vec128"/>
<reg name="xmm7" bitsize="128" type="vec128"/>
<reg name="mxcsr" bitsize="32" type="i386_mxcsr" group="vector"/>
</feature>
</target>

9
debug/x86_ddd/.gdbinit Executable file
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@@ -0,0 +1,9 @@
target remote localhost:1234
set architecture i386
set disassembly-flavor intel
display/x $eip
display/x $esp
display/x $ebp
graph display `x /16xw ($ebp - (16*4))`

8
debug/x86_gdb/.gdbinit Executable file
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@@ -0,0 +1,8 @@
target remote localhost:1234
set architecture i386
set disassembly-flavor intel
layout asm
display/x $eip
display/x $esp
display/x $ebp

35
docs/examples.txt Executable file
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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])

127
docs/seabios_config Executable file
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#
# Automatically generated file; DO NOT EDIT.
# SeaBIOS Configuration
#
#
# General Features
#
# CONFIG_COREBOOT is not set
CONFIG_QEMU=y
# CONFIG_CSM is not set
CONFIG_QEMU_HARDWARE=y
# CONFIG_XEN is not set
CONFIG_THREADS=y
CONFIG_RELOCATE_INIT=y
CONFIG_BOOTMENU=y
CONFIG_BOOTSPLASH=y
CONFIG_BOOTORDER=y
# CONFIG_ENTRY_EXTRASTACK is not set
CONFIG_MALLOC_UPPERMEMORY=y
CONFIG_ROM_SIZE=0
#
# Hardware support
#
CONFIG_ATA=y
# CONFIG_ATA_DMA is not set
# CONFIG_ATA_PIO32 is not set
CONFIG_AHCI=y
CONFIG_SDCARD=y
# CONFIG_VIRTIO_BLK is not set
# CONFIG_VIRTIO_SCSI is not set
# CONFIG_PVSCSI is not set
# CONFIG_ESP_SCSI is not set
# CONFIG_LSI_SCSI is not set
# CONFIG_MEGASAS is not set
# CONFIG_MPT_SCSI is not set
CONFIG_FLOPPY=y
CONFIG_FLASH_FLOPPY=y
# CONFIG_NVME is not set
CONFIG_PS2PORT=y
CONFIG_USB=y
CONFIG_USB_UHCI=y
CONFIG_USB_OHCI=y
CONFIG_USB_EHCI=y
CONFIG_USB_XHCI=y
CONFIG_USB_MSC=y
CONFIG_USB_UAS=y
CONFIG_USB_HUB=y
CONFIG_USB_KEYBOARD=y
CONFIG_USB_MOUSE=y
CONFIG_SERIAL=y
CONFIG_SERCON=y
CONFIG_LPT=y
CONFIG_RTC_TIMER=y
CONFIG_HARDWARE_IRQ=y
CONFIG_USE_SMM=y
CONFIG_CALL32_SMM=y
CONFIG_MTRR_INIT=y
CONFIG_PMTIMER=y
CONFIG_TSC_TIMER=y
#
# BIOS interfaces
#
CONFIG_DRIVES=y
CONFIG_CDROM_BOOT=y
CONFIG_CDROM_EMU=y
CONFIG_PCIBIOS=y
CONFIG_APMBIOS=y
CONFIG_PNPBIOS=y
CONFIG_OPTIONROMS=y
CONFIG_PMM=y
CONFIG_BOOT=y
CONFIG_KEYBOARD=y
CONFIG_KBD_CALL_INT15_4F=y
CONFIG_MOUSE=y
CONFIG_S3_RESUME=y
CONFIG_VGAHOOKS=y
CONFIG_DISABLE_A20=y
# CONFIG_WRITABLE_UPPERMEMORY is not set
# CONFIG_TCGBIOS is not set
#
# BIOS Tables
#
CONFIG_PIRTABLE=y
CONFIG_MPTABLE=y
CONFIG_SMBIOS=y
CONFIG_ACPI=y
CONFIG_ACPI_DSDT=y
CONFIG_FW_ROMFILE_LOAD=y
#
# VGA ROM
#
# CONFIG_NO_VGABIOS is not set
# CONFIG_VGA_STANDARD_VGA is not set
# CONFIG_VGA_CIRRUS is not set
# CONFIG_VGA_ATI is not set
CONFIG_VGA_BOCHS=y
# CONFIG_VGA_GEODEGX2 is not set
# CONFIG_VGA_GEODELX is not set
# CONFIG_DISPLAY_BOCHS is not set
# CONFIG_VGA_RAMFB is not set
CONFIG_VGA_BOCHS_STDVGA=y
# CONFIG_VGA_BOCHS_VMWARE is not set
# CONFIG_VGA_BOCHS_QXL is not set
# CONFIG_VGA_BOCHS_VIRTIO is not set
CONFIG_BUILD_VGABIOS=y
CONFIG_VGA_STDVGA_PORTS=y
CONFIG_VGA_FIXUP_ASM=y
# CONFIG_VGA_ALLOCATE_EXTRA_STACK is not set
CONFIG_VGA_EXTRA_STACK_SIZE=512
CONFIG_VGA_VBE=y
CONFIG_VGA_PCI=y
# CONFIG_OVERRIDE_PCI_ID is not set
CONFIG_VGA_VID=0x1234
CONFIG_VGA_DID=0x1111
#
# Debugging
#
CONFIG_DEBUG_LEVEL=1
# CONFIG_DEBUG_SERIAL is not set
# CONFIG_DEBUG_SERIAL_MMIO is not set
CONFIG_DEBUG_IO=y

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

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

95
include/errors.inc Executable file
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; Copyright (C) 2020 Bradley Claus
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
; Errors
; 12 Errors, 5 in use
%define MBR_ERROR_DISK_T_ERR 'a'
%define MBR_ERROR_NO_INT32E 'b'
%define MBR_ERROR_NO_NO_BOOT_PART 'c'
%define MBR_ERROR_DISK_READ_ERR 'd'
%define MBR_ERROR_NO_VBR_SIG 'e'
%define MBR_ERROR_RESERVED_f 'f'
%define MBR_ERROR_RESERVED_g 'g'
%define MBR_ERROR_RESERVED_h 'h'
%define MBR_ERROR_RESERVED_i 'i'
%define MBR_ERROR_RESERVED_j 'j'
%define MBR_ERROR_RESERVED_k 'k'
%define MBR_ERROR_RESERVED_l 'l'
; 12 Error
%define VBR_ERROR_WRONG_FAT_SIZE 'm'
%define VBR_ERROR_NO_SIGNATURE 'n'
%define VBR_ERROR_DISK_READ_ERR 'o'
%define VBR_ERROR_RESERVED_p 'p'
%define VBR_ERROR_RESERVED_q 'q'
%define VBR_ERROR_RESERVED_r 'r'
%define VBR_ERROR_RESERVED_s 's'
%define VBR_ERROR_RESERVED_t 't'
%define VBR_ERROR_RESERVED_u 'u'
%define VBR_ERROR_RESERVED_v 'v'
%define VBR_ERROR_RESERVED_w 'w'
%define VBR_ERROR_RESERVED_x 'x'
; 26 errors, 8 in use
%define STAGE2_A20_FAILED 'A'
%define STAGE2_SIGNATURE_MISSING 'B'
%define STAGE2_MM_E820_NO_SUPPORT 'C'
%define STAGE2_MM_E820_MISC_ERR 'D'
%define STAGE2_MM_E820_NONSTANDARD 'E'
%define STAGE2_MM_E820_NO_SMAP 'F'
%define STAGE2_MBR_DISK_READ_ERROR 'G'
%define STAGE2_FAT32_INIT_ERROR 'H'
%define STAGE2_FAT32_NO_FILE 'I'
%define STAGE2_FAT32_END_OF_CHAIN 'J'
%define STAGE2_ERROR_RESERVED_K 'K'
%define STAGE2_ERROR_RESERVED_L 'L'
%define STAGE2_ERROR_RESERVED_M 'M'
%define STAGE2_ERROR_RESERVED_N 'N'
%define STAGE2_ERROR_RESERVED_O 'O'
%define STAGE2_ERROR_RESERVED_P 'P'
%define STAGE2_ERROR_RESERVED_Q 'Q'
%define STAGE2_ERROR_RESERVED_R 'R'
%define STAGE2_ERROR_RESERVED_S 'S'
%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'
%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

86
include/fat32/bpb.inc Executable file
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@@ -0,0 +1,86 @@
; Copyright (C) 2020 Bradley Claus
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
; BPB Information
; Off. Hex Off. Size Description
; 0 0x00 3 The first three bytes EB 3C 90 disassemble to JMP SHORT 3C NOP. (The 3C value may be different.)
; 3 0x03 8 OEM identifier.
; 11 0x0B 2 The number of Bytes per sector (remember, all numbers are in the little-endian format).
; 13 0x0D 1 Number of sectors per cluster.
; 14 0x0E 2 Number of reserved sectors. The boot record sectors are included in this value.
; 16 0x10 1 Number of File Allocation Tables (FAT's) on the storage media. Often this value is 2.
; 17 0x11 2 Number of directory entries (must be set so that the root directory occupies entire sectors).
; 19 0x13 2 The total sectors in the logical volume.
; If this value is 0, it means there are more than 65535 sectors in the volume,
; and the actual count is stored in the Large Sector Count entry at 0x20.
;
; 21 0x15 1 This Byte indicates the media descriptor type.
; 22 0x16 2 Number of sectors per FAT. FAT12/FAT16 only.
; 24 0x18 2 Number of sectors per track.
; 26 0x1A 2 Number of heads or sides on the storage media.
; 28 0x1C 4 Number of hidden sectors. (i.e. the LBA of the beginning of the partition.)
; 32 0x20 4 Large sector count. This field is set if there are more than 65535 sectors in the volume,
; resulting in a value which does not fit in the Number of Sectors entry at 0x13.
;-- BPB (BIOS Parameter Block)
%define bsOemName bx+0x03
%define bsBytesPerSect bx+0x0B
%define bsSecsPerClust bx+0x0D
%define bsResSectors bx+0x0E
%define bsFATs bx+0x10
%define bsRootDirEnts bx+0x11
%define bsSectors bx+0x13
%define bsMedia bx+0x15
%define bsSectPerFAT1216 bx+0x16
%define bsSectPerTrack bx+0x18
%define bsHeads bx+0x1A
%define bsHidden bx+0x1C
%define bsSectorHuge bx+0x20
;-- End BPB
; EBPB Information (FAT32)
; Off. Hex Off. Size Description
; 36 0x024 4 Sectors per FAT. The size of the FAT in sectors.
; 40 0x028 2 Flags.
; 42 0x02A 2 FAT version number. The high byte is the major version and the low byte is the minor version. FAT drivers should respect this field.
; 44 0x02C 4 The cluster number of the root directory. Often this field is set to 2.
; 48 0x030 2 The sector number of the FSInfo structure.
; 50 0x032 2 The sector number of the backup boot sector.
; 52 0x034 12 Reserved. When the volume is formated these bytes should be zero.
; 64 0x040 1 Drive number. The values here are identical to the values returned by the BIOS interrupt 0x13. 0x00 for a floppy disk and 0x80 for hard disks.
; 65 0x041 1 Flags in Windows NT. Reserved otherwise.
; 66 0x042 1 Signature (must be 0x28 or 0x29).
; 67 0x043 4 Volume ID 'Serial' number. Used for tracking volumes between computers. You can ignore this if you want.
; 71 0x047 11 Volume label string. This field is padded with spaces.
; 82 0x052 8 System identifier string. Always "FAT32 ". The spec says never to trust the contents of this string for any use.
; 90 0x05A 420 Boot code.
; 510 0x1FE 2 Bootable partition signature 0xAA55.
;-- EBPB (Extended BIOS Parameter Block)
%define bsSectorsPerFAT bx+0x24
%define bsFlags bx+0x28
%define bsFATVersion bx+0x2A
%define bsRootDirCluster bx+0x2C
%define bsFSInfoCluster bx+0x30
%define bsBackupBootSector bx+0x32
%define bsReserved1 bx+0x34
%define bsDriveNumber bx+0x40
%define bsNTFlags bx+0x41
%define bsFATSignature bx+0x42
%define bsVolumeSerial bx+0x43
%define bsVolumeLabel bx+0x47
%define bsSystemIdent bx+0x52
;-- End EBPB

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; Copyright (C) 2020 Bradley Claus
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
; ## FAT32 Info ##
; total_sectors = bsSectorsHuge
; fat_size = bsSectorsPerFat
;
; first_data_sector = bsResSectors + (bsFATs * bsSectPerFAT);
; total_data_sectors = bsSectorsHuge - (bsResSectors + (bsFATs * bsSectPerFAT));
; total_clusters = total_data_sectors / bsSectsPerClust
; first_fat_sector = bsResSectors
;
; ## FAT32 Table information ##
;
; fat_offset = active_cluster * 4
; fat_sector = first_fat_sector + (fat_offset / sector_size)
; entry_offset = fat_offset % sector_size
;
; table_value = fat_table[entry_offset] & 0x0FFF_FFFF
;
; ## FAT32 Directory Entries ##
; root_dir_cluster = bsRootDirCluster
; root_dir_sectors = ? (this is varible on FAT32 since the root dir is a cluster chain)
; first_sector_of_cluster = ((cluster - 2) * bsSectPerClust) + first_data_sector;
; BPB Information
; Size Description
; 8 OEM identifier.
; 2 The number of Bytes per sector (remember, all numbers are in the little-endian format).
; 1 Number of sectors per cluster.
; 2 Number of reserved sectors. The boot record sectors are included in this value.
; 1 Number of File Allocation Tables (FAT's) on the storage media. Often this value is 2.
; 2 Number of directory entries (must be set so that the root directory occupies entire sectors).
; 2 The total sectors in the logical volume.
; If this value is 0, it means there are more than 65535 sectors in the volume,
; and the actual count is stored in the Large Sector Count entry at 0x20.
;
; 1 This Byte indicates the media descriptor type.
; 2 Number of sectors per FAT. FAT12/FAT16 only.
; 2 Number of sectors per track.
; 2 Number of heads or sides on the storage media.
; 4 Number of hidden sectors. (i.e. the LBA of the beginning of the partition.)
; 4 Large sector count. This field is set if there are more than 65535 sectors in the volume,
; resulting in a value which does not fit in the Number of Sectors entry at 0x13.
struc FAT32_bpb_t
.ident_8 resb 8
.bytes_per_sector_16 resb 2
.sectors_per_cluster_8 resb 1
.reserved_sectors_16 resb 2
.fat_count_8 resb 1
.dir_entry_count_16 resb 2
.sector_count_16 resb 2
.media_desc_8 resb 1
.sectors_per_fat_16 resb 2
.sectors_per_track_16 resb 2
.head_count_16 resb 2
.hidden_sectors_32 resb 4
.sector_count_32 resb 4
endstruc
; EBPB Information (FAT32)
; Size Description
; 4 Sectors per FAT. The size of the FAT in sectors.
; 2 Flags.
; 2 FAT version number. The high byte is the major version and the low byte is the minor version. FAT drivers should respect this field.
; 4 The cluster number of the root directory. Often this field is set to 2.
; 2 The sector number of the FSInfo structure.
; 2 The sector number of the backup boot sector.
; 12 Reserved. When the volume is formated these bytes should be zero.
; 1 Drive number. The values here are identical to the values returned by the BIOS interrupt 0x13. 0x00 for a floppy disk and 0x80 for hard disks.
; 1 Flags in Windows NT. Reserved otherwise.
; 1 Signature (must be 0x28 or 0x29).
; 4 Volume ID 'Serial' number. Used for tracking volumes between computers. You can ignore this if you want.
; 11 Volume label string. This field is padded with spaces.
; 8 System identifier string. Always "FAT32 ". The spec says never to trust the contents of this string for any use.
struc FAT32_ebpb_t
.sectors_per_fat_32 resb 4
.fat32_flags_16 resb 2
.fat32_version_16 resb 2
.root_dir_cluster_32 resb 4
.fsinfo_sector_16 resb 2
.backup_boot_sector_16 resb 2
.reserved1 resb 12
.drive_number_8 resb 1
.nt_flags_8 resb 1
.signature_8 resb 1
.volume_serial_32 resb 4
.volume_label resb 11
.system_ident resb 8
endstruc
; ## Standard 8.3 structure ###
; Offset Length (Bytes) Description
; 0 11 8.3 file name. The first 8 characters are the name and the last 3 are the extension.
; 11 1 File Atrributes
; READ_ONLY=0x01
; HIDDEN=0x02
; SYSTEM=0x04
; VOLUME_ID=0x08
; DIRECTORY=0x10
; ARCHIVE=0x20
; LFN=READ_ONLY|HIDDEN|SYSTEM|VOLUME_ID == 0x0F
;
; 12 1 NT Reserved
; 13 1 Creation time in tenths of a second.
; 14 2 File creation time, Hour 5 bits, Minutes 6 bits, Seconds 5 Bits, multiply seconds by 2
; 16 2 File creation date, Year 7 bits, month 4 bits, day 5 bits
; 18 2 Last Accessed date. same format at creation date
; 20 2 High 16 bits of entry's first cluster
; 22 2 Last modification time. same format at creation time
; 24 2 Last modification date. same format as creation date
; 26 2 Low 16 bits of entry's first cluster
; 28 4 File size in bytes
struc FAT32_SFN_t
.label resb 11
.attributes_8 resb 1
.nt_res_8 resb 1
.csec_8 resb 1
.ctime_16 resb 2
.cdate_16 resb 2
.adate_16 resb 2
.cluster_16_high resb 2
.mtime_16 resb 2
.mdate_16 resb 2
.cluster_16_low resb 2
.size_32 resb 4
endstruc
; ## Long file name (LFN) structure format ##
;
; 0 1 The order of this entry in the sequence of long file name entries. This value helps you to know where in the file's name the characters from this entry should be placed.
; 1 10 The first 5, 2-byte characters of this entry.
; 11 1 Attribute. Always equals 0x0F. (the long file name attribute)
; 12 1 Long entry type. Zero for name entries.
; 13 1 Checksum generated of the short file name when the file was created. The short filename can change without changing the long filename in cases where the partition is mounted on a system which does not support long filenames.
; 14 12 The next 6, 2-byte characters of this entry.
; 26 2 Always zero.
; 28 4 The final 2, 2-byte characters of this entry.
;
; LFN entries are always placed immediately before their respective 8.3 entry
;
; LAST_LFN_ENTRY == 0x40
; Max of 20 in sequence == 0x14
struc FAT32_LFN_t
.order resb 1
.lfn_first5 resb 10
.attributes_8 resb 1
.zero1 resb 1
.checksum resb 1
.lfn_next6 resb 12
.zero2 resb 2
.lfn_last2 resb 4
endstruc
; FSInfo
; 0 0x0 4 Lead signature (must be 0x41615252 to indicate a valid FSInfo structure)
; 4 0x4 480 Reserved, these bytes should never be used
; 484 0x1E4 4 Another signature (must be 0x61417272)
; 488 0x1E8 4 Contains the last known free cluster count on the volume. If the value is 0xFFFFFFFF, then the free count is unknown and must be computed.
; However, this value might be incorrect and should at least be range checked (<= volume cluster count)
;
; 492 0x1EC 4 Indicates the cluster number at which the filesystem driver should start looking for available clusters.
; If the value is 0xFFFFFFFF, then there is no hint and the driver should start searching at 2.
; Typically this value is set to the last allocated cluster number. As the previous field, this value should be range checked.
;
; 496 0x1F0 12 Reserved
; 508 0x1FC 4 Trail signature (0xAA550000)
struc FAT32_FSInfo_t
.head_signature_32 resd 1
.reserved1 resb 480
.body_signature_32 resd 1
.free_cluster_count_32 resd 1
.first_avail_cluster_32 resd 1
.reserved2 resd 3
.tail_signature_32 resd 1
endstruc
; 32 bytes
struc FAT32_State_t
.first_root_dir_sector_32 resd 1
.first_data_sector_32 resd 1
.first_fat_sector_32 resd 1
.fat_size_32 resd 1
.active_cluster_32 resd 1
.active_FAT_cluster_32 resd 1
.active_dir_cluster_32 resd 1
.active_drive_lba_32 resd 1
endstruc
; 16 bytes
struc FAT32_NextClusterData_t
.fat_offset resd 1
.fat_sector resd 1
.entry_offset resd 1
.reserved_1 resd 1
endstruc
; FAT32 Attributes
%define FAT32_ATTR_RO 0x01
%define FAT32_ATTR_HIDDEN 0x02
%define FAT32_ATTR_SYSTEM 0x04
%define FAT32_ATTR_VOLID 0x08
%define FAT32_ATTR_DIR 0x10
%define FAT32_ATTR_ARC 0x20
; LFN == RO | HIDDEN | SYSTEM | VOLID == 0x0F
%define FAT32_ATTR_LFN 0x0F

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

59
include/partition_table.inc Executable file
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; Copyright (C) 2020 Bradley Claus
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
; Partition table entry format
; Off. Size. Description
;0x00 1 Drive attributes (bit 7 set = active or bootable)
;0x01 3 CHS Address of partition start
;0x04 1 Partition type
;0x05 3 CHS address of last partition sector
;0x08 4 LBA of partition start
;0x0C 4 Number of sectors in partition
struc PartEntry_t
.attributes resb 1
.chs_start resb 3
.part_type resb 1
.chs_end resb 3
.lba_start resb 4
.lba_length resb 4
endstruc
struc PartTable_t
.partition1 resb 16
.partition2 resb 16
.partition3 resb 16
.partition4 resb 16
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

196
scripts/create-disk.sh Executable file
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#!/usr/bin/env bash
# Copyright (C) 2020 Bradley Claus
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <https://www.gnu.org/licenses/>.
if ! [ $(id -u) = 0 ]; then
echo "Script must be run as root!"
exit 1
fi
mbr_file=build/mbr.bin
vbr_file=build/vbr.bin
stage2_file=build/stage2.bin
boottest_file=build/BOOT_386.bin
mount_point=/tmp/stevia_disk
if ! [ -e disk.img ]; then
# create raw disk image with 128MiB of space
dd if=/dev/zero of=disk.img bs=512 count=262144
sync
else
echo "Removing old disk image..."
rm -rfv disk.img
dd if=/dev/zero of=disk.img bs=512 count=262144
sync
fi
if [[ "$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
# 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 $ld
# get first partition
firstpart=$(lsblk -ilp -o NAME $ld | tr '\n' ' ' | awk '{print $3}')
mkfs.vfat -v -F32 $firstpart
# copy MBR while preserving partition table
dd if=$mbr_file of=$ld bs=1 count=440
# copy MBR 0xAA55
dd if=$mbr_file of=$ld bs=1 seek=510 skip=510 count=2
# copy VBR to partition 1 while preserving partition information
# copy jmp short entry; nop
dd if=$vbr_file of=$firstpart bs=1 count=3
# copy bootcode
dd if=$vbr_file of=$firstpart bs=1 seek=90 skip=90 count=420
# copy 0xAA55
dd if=$vbr_file of=$firstpart bs=1 seek=510 skip=510 count=2
#stage2 to sectors 1-64
dd if=$stage2_file of=$ld bs=512 seek=1
# copy boot32 boot test file to disk image
if ! [ -e $mount_point ]; then
mkdir $mount_point
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
fi
# detach loop device
umount $mount_point
sync
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 $SUDOUSER -g) disk.img
else
echo "unable to find MBR/VBR binaries!"
exit 2
fi
# requires util-linux from homebrew
elif [[ "$OSTYPE" == "darwin"* ]]; then
sfdisk_path="/usr/local/opt/util-linux/sbin/sfdisk"
if [ -e $mbr_file ] && [ -e $vbr_file ]; then
# use hdiutil to attach our empty disk image
ld_path_raw=$(hdiutil attach -readwrite -imagekey diskimage-class=CRawDiskImage -nomount -blocksize 512 -noverify disk.img)
ld=$(echo $ld_path_raw | sed s:/dev/::)
ld_path="/dev/$ld"
# create a DOS disk, with 1 FAT32 partition
if ! [ -e $sfdisk_path ]; then
echo "sfdisk utility was not found...We cannot use diskutil to make disks due to the fact that it only makes Hybrid MBR's & GPT disks...blame Apple"
exit 4
else
$sfdisk_path $ld_path < scripts/loop_setup.sfdisk
fi
# give stuff a chance to settle, macOS has problems here
sync
sleep .5
# reattch the raw image file since macOS doesn't have a partprobe...
# this is the only way I know to get macOS to reprobe the disk
hdiutil eject $ld
unset ld_path
unset ld
unset ld_path_raw
ld_path_raw=$(hdiutil attach -readwrite -imagekey diskimage-class=CRawDiskImage -nomount -blocksize 512 -noverify disk.img)
ld=$(echo $ld_path_raw | grep "FDisk_partition_scheme" | awk '{print $1}' | sed s:/dev/::)
ld_path="/dev/$ld"
if ! [ -b /dev/$ld ]; then
echo "Unable to remount disk! exitting before I do some damage!"
exit 5
fi
# get first partition and format as FAT32
firstpart=$(diskutil list $ld | grep 1: | awk '{print $6}')
firstpart_direct="r$firstpart"
newfs_msdos -F 32 /dev/$firstpart_direct
sync
# copy MBR while preserving partition table
dd if=$mbr_file of=$ld_path bs=1 count=440 conv=sync
# copy MBR 0xAA55
dd if=$mbr_file of=$ld_path bs=1 seek=510 skip=510 count=2 conv=sync
# copy VBR to partition 1 while preserving partition information
# copy jmp short entry; nop
dd if=$vbr_file of=/dev/$firstpart bs=1 count=3 conv=sync
# copy bootcode
dd if=$vbr_file of=/dev/$firstpart bs=1 seek=90 skip=90 count=420 conv=sync
# copy 0xAA55
dd if=$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
#sync pending dd stuff
sync
# copy boot32 boot test file to disk image
if ! [ -e $mount_point ]; then
mkdir $mount_point
else
echo "$mount_point exists! clearing contents..."
rm -rfv $mount_point
mkdir $mount_point
fi
mount -t msdos /dev/$firstpart $mount_point
if [ -e $boottest_file ]; then
cp -v $boottest_file $mount_point
else
echo "unable to find boot32.bin!"
exit 3
fi
# detach loop device
sync
umount /dev/$firstpart
hdiutil eject $ld
# chown to the real user to prevent issues with reading/writing the file later
SUDOUSER=$(logname)
chown ${SUDOUSER}:staff disk.img
else
echo "unable to find MBR/VBR binaries!"
exit 2
fi
else
# Unknown.
echo "Unknown OS type! Supported build hosts systems are GNU/Linux and macOS."
exit 1
fi

4
scripts/loop_setup.sfdisk Executable file
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label: dos
unit: sectors
start= 2048, type=b, bootable

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

554
src/miniboot32/BOOT_386.s Executable file
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; Copyright (C) 2020 Bradley Claus
;
; This program is free software: you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation, either version 3 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program. If not, see <https://www.gnu.org/licenses/>.
[BITS 32]
[ORG 0x100000]
[CPU KATMAI]
jmp short start32
nop
; Unless noted otherwise, functions will be the standard x86 cdecl used in GCC
; In cdecl, subroutine arguments are passed on the stack.
; Integer values and memory addresses are returned in the EAX register,
; floating point values in the ST0 x87 register.
; Registers EAX, ECX, and EDX are caller-saved,
; and the rest are callee-saved.
; The x87 floating point registers ST0 to ST7 must be empty (popped or freed)
; when calling a new function, and ST1 to ST7 must be empty on exiting a function.
; ST0 must also be empty when not used for returning a value.
;
; EXAMPLE: to call uint8_t* kmemset(uint8_t* dest, uint8_t val, uint8_t size);
; => kmemset(*((char*) 0xb8000), 'F', (80*25))
;
; push ebp ; save old call frame pointer
; mov ebp, esp ; new call frame pointer
; push 0x000007D0 ; push args RTL, EBP - 4
; push 'F' ; * EBP - 8
; push 0x000b8000 ; * EBP - 12
; call kmemset ; call function, this also places a return pointer on stack
; add esp, 12 ; remove call arguments from stack frame
; mov esp, ebp ; restore stack frame pointer (callee saves EBP)
; pop ebp ; restore call frame pointer
;
;
; 33 bytes BPB + 26 Byte EBPB
struc BPBStruct
.OemName resb 8
.BytesPerSect resw 1
.SecsPerClust resb 1
.ResSectors resw 1
.FATs resb 1
.RootDirEnts resw 1
.Sectors resw 1
.Media resb 1
.SectPerFAT resw 1
.SectPerTrack resw 1
.Heads resw 1
.Hidden resd 1
.SectorHuge resd 1
; begin EBPB
.DriveNumber resb 1
.NTReserved resb 1
.Signature resb 1
.VolumeID resd 1
.VolumeLabel resb 11
.SysIdent resb 8
endstruc
; 12 bytes
struc FSInfoStruct
.first_root_dir_sector resw 1
.last_root_dir_sector resw 1
.root_dir_len resw 1
.first_data_sector resw 1
.active_cluster resw 1
.active_FAT_cluster resw 1
endstruc
; 20 bytes
struc KInfoStruct
.load_address resd 1
.file_len resd 1
.file_name resb 8
.file_ext resb 3
.reserved1 resb 1
endstruc
; Address Range Descriptor Structure
;
; Offset in Bytes Name Description
; 0 BaseAddrLow u32 - Low 32 Bits of Base Address
; 4 BaseAddrHigh u32 - High 32 Bits of Base Address
; 8 LengthLow u32 - Low 32 Bits of Length in Bytes
; 12 LengthHigh u32 - High 32 Bits of Length in Bytes
; 16 Type u32 - Address type of this range.
; 20 ExtType u32 - ACPI 3.0 extended type
struc AddressRangeDescStruct
.BaseAddrLow resd 1
.BaseAddrHigh resd 1
.LengthLow resd 1
.LengthHigh resd 1
.Type resd 1
.ExtType resd 1
endstruc
; 20 bytes, passed to loaded kernel
struc CBootInfoStruct
.MemoryMapPtr resd 1
.MemoryMapEntries resd 1
.BPBDataPtr resd 1
.FSInfoPtr resd 1
.KInfoPtr resd 1
endstruc
;;;
; Errors
; 0 = unused
; 1 = No CPUID support on this platform (VM or some very old hardware?)
; 2 = magic signature not found at end of file
; 3 = Unexpected/unhandled artithmetic overflow/carry
;;;
%define MAX_BYTES (1024 * 8)
%define VGA_BUF 0xb8000
;black BG/Green FG
%define TTY_COLOR 0x0200
;black BG/Red FG
%define TTY_ERR_CLR 0x0400
;subtract 1 for max array values
%define VGA_MAX_Y 25
%define VGA_MAX_X 80
; VGA memory is row-major => offset = (row * MAX_Colums) + colum
; macro array is counted from 0,0 = 1,1 => 79,24 is the last usable space in a page
%define VGA_OFFSET(x,y) (((y*VGA_MAX_X) + x)*2)
start32:
mov ax, 0x10
mov ds, ax
mov es, ax
mov fs, ax
mov gs, ax
mov ss, ax ; load data registers with 2nd GDT selector
mov esp, stack_top
mov ebp, esp
; debugger hack because gdb doesn't like to switch register sizes
; issue a set $eax = 1 to continue
%ifdef DEBUG_HACK
mov eax, 0
.gdb_hack:
test eax, eax
jz start32.gdb_hack
%endif
mov eax, dword [BOOT_SIG]
cmp eax, 0xA0B0C0D0
jz start32.signature_present
mov al, "2"
call error
.signature_present:
call check_cpuid
push ebp
mov ebp, esp
lea eax, [welcome_cstr]
push eax
call vga_puts
leave
push ebp
mov ebp, esp
lea eax, [version_cstr]
push eax
call vga_puts
leave
push ebp
mov ebp, esp
lea eax, [datetime_cstr]
push eax
call vga_puts
leave
mov eax, VGA_BUF
add eax, VGA_OFFSET(78, 24)
mov dword [eax], 0x2f4b2f4f
hlt
; Early error printer. Prints 'ERR: X' where X is an error code in al
error:
mov eax, VGA_BUF
add eax, VGA_OFFSET(73, 24)
mov dword [eax], 0x4f524f45
add eax, 0x2
mov dword [eax], 0x4f3a4f52
add eax, 0x2
mov dword [eax], 0x4f204f20
add eax, 0x2
mov byte [eax], al
hlt
check_cpuid:
; flip cpuid id bit (bit 21) to check for cpuid support
; copy flags to eax via stack
pushfd
pop eax
mov ecx, eax ; copy to ecx for compare
xor eax, 1 << 21 ; xor eax with the 21st bit set
push eax ; push new flags and pop to flags register
popfd
pushfd
pop eax
cmp eax, ecx ; can we change the bit?
je .no_cpuid
ret
.no_cpuid:
mov al, "1"
call error
; int vga_puts(char* str)
;
; INPUT:
; str: C-Sytle string
;
; OUTPUT:
; EAX = characters printed
;
vga_puts:
; prolog, EBP = SFP (Stack frame pointer), [EBP-4] = char* str
push edi
push esi
push ebx
.get_str_len:
mov edi, [ebp - 4]
xor ecx, ecx ; ECX = 0
not ecx ; ECX = -1 == 0xFFFFFFFF
xor eax, eax ; search for al = 0x0
cld
repne scasb ; deincrement ecx while searching for al
not ecx ; the inverse of a neg number = abs(x) - 1
dec ecx ; ECX contains the length of the string - nul byte at end
mov edi, VGA_BUF ; load dest index with VGA buffer + calculated offset
mov esi, [ebp -4] ; load source index with src string
; ECX = string length
; ESI = source string to print
; EDI = destination in the VGA buffer
.print_char:
cmp ecx, 0x0
jle vga_puts.endf
cmp byte [vga_buf_pos_x], 80
je vga_puts.end_of_line
cmp byte [vga_buf_pos_y], 25
je vga_puts.scroll_up
cmp byte [esi], 0x20
jl vga_puts.special_character_switch
push ebp
mov ebp, esp
xor eax, eax
mov al, [vga_buf_pos_y]
push eax ; vga_pos_y
xor eax, eax
mov al, [vga_buf_pos_x]
push eax ; vga_pos_x
; uint16_t vga_calc_offset(uint8_t vga_pos_x, uint8_t vga_pos_y)
call vga_calc_offset
leave
xor bx, bx
mov bl, byte [esi]
or bx, TTY_COLOR ; create VGA character
mov [edi+eax], bx
inc esi
inc byte [vga_buf_pos_x]
dec ecx
jmp vga_puts.print_char ; loop until ECX == 0
.end_of_line:
; advance to next row
inc byte [vga_buf_pos_y]
mov byte [vga_buf_pos_x], 0
jmp vga_puts.print_char
.scroll_up:
; after 25 rows, move to next page (either swap pages [memcpy] or erase page 0)
mov byte [vga_buf_pos_x], 0
mov byte [vga_buf_pos_y], 0
push ebp
mov ebp, esp
mov eax, 0x7D0
push eax ; 1 VGA page = 0x7D0 elements
xor eax, eax
push eax ; we want to blank the page with 0x0000
mov eax, VGA_BUF
push eax ; load vga buffer base (0xb8000)
; uint16_t* kmemset_word(void* dest, uint16_t val, size_t len);
call kmemset_byte
leave
jmp vga_puts.print_char
.special_character_switch:
cmp byte[esi], 0xA
je vga_puts.handle_LF
cmp byte[esi], 0xD
je vga_puts.handle_CR
; Default case
.special_character_endp:
dec ecx
inc esi
jmp vga_puts.print_char
.handle_LF:
; advance to next row
inc byte [vga_buf_pos_y]
jmp vga_puts.special_character_endp
.handle_CR:
mov byte [vga_buf_pos_x], 0
jmp vga_puts.special_character_endp
.endf:
pop ebx
pop esi
pop edi
ret
; short vga_get_xy(void)
;
; INPUT:
;
; OUTPUT:
; EAX = xy_pos
; > x = xy_pos && 0xFF00
; y = xy_pos && 0x00FF
; 2 MSB of EAX are 0.
;
vga_get_xy:
.endf:
ret
; void vga_set_xy(short xy_pos)
; xy_pos is a byte packed word (16bit value), MSB is x, LSB is y
; => x = xy_pos && 0xFF00
; y = xy_pos && 0x00FF
;
; INPUT:
; xy_pos
;
; OUTPUT:
; NONE
;
vga_set_xy:
.endf:
ret
; uint16_t vga_calc_offset(uint8_t vga_pos_x, uint8_t vga_pos_y)
; VGA_OFFSET(x,y) == (((y*VGA_MAX_X) + x)*2)
vga_calc_offset:
xor eax, eax
xor edx, edx
mov edx, [ebp-4]
mov ax, VGA_MAX_X
mul dx ; DX:AX contains (y*VGA_MAX_X)
jc vga_calc_offset.artithmetic_error
mov edx, [ebp-8]
add ax, dx
jc vga_calc_offset.artithmetic_error
mov dx, 0x02
mul dx ; DX:AX contains (y*VGA_MAX_X) + x) * 2
jnc vga_calc_offset.endf
.artithmetic_error:
mov al, '3'
call error
.endf:
; (e)AX contains the offset
ret
; uint32_t* kmemset(void* dest, uint32_t val, size_t len);
kmemset_dword:
push edi ; function uses edi, so save it.
; [ebp] = previous call frame
mov ecx, [ebp - 4] ; size_t len
mov eax, [ebp - 8] ; uint32_t val
mov edi, [ebp - 12] ; void * ptr
; [ebp - 16] = return adress
; [ebp - 20] = saved EDI
rep stosd
.endf:
mov eax, [ebp - 12] ; return pointer to dest
pop edi ; restore edi
ret
; uint16_t* kmemset(void* dest, uint16_t val, size_t len);
kmemset_word:
push edi ; function uses edi, so save it.
; [ebp] = previous call frame
mov ecx, [ebp - 4] ; size_t len
mov ax, [ebp - 8] ; uint16_t val
mov edi, [ebp - 12] ; void * ptr
; [ebp - 16] = return adress
; [ebp - 20] = saved EDI
rep stosw
.endf:
mov eax, [ebp - 12] ; return pointer to dest
pop edi ; restore edi
ret
; uint8_t* kmemset(void* dest, uint8_t val, size_t len);
kmemset_byte:
push edi ; function uses edi, so save it.
; [ebp] = previous call frame
mov ecx, [ebp - 4] ; size_t len
mov al, [ebp - 8] ; uint8_t val
mov edi, [ebp - 12] ; void * ptr
; [ebp - 16] = return adress
; [ebp - 20] = saved EDI
rep stosb
.endf:
mov eax, [ebp - 12] ; return pointer to dest
pop edi ; restore edi
ret
; uint32_t* kmemset(uint32_t* dest, uint32_t* src, size_t len);
kmemcpy_dword:
push edi
push esi ; edi, esi are callee save
mov edi, [ebp-12] ; dest
mov esi, [ebp-8] ; source
mov ecx, [ebp-4] ; length
cld ; ensure we are incrementing
rep movsd
.endf:
mov eax, [ebp-12] ; return pointer to dest
pop esi
pop edi
ret
; uint16_t* kmemset(uint16_t* dest, uint16_t* src, size_t len);
kmemcpy_word:
push edi
push esi ; edi, esi are callee save
mov edi, [ebp-12] ; dest
mov esi, [ebp-8] ; source
mov ecx, [ebp-4] ; length
cld ; ensure we are incrementing
rep movsw
.endf:
mov eax, [ebp-12] ; return pointer to dest
pop esi
pop edi
ret
; uint8_t* kmemset(uint8_t* dest, uint8_t* src, size_t len);
; not overlap safe
kmemcpy_byte:
push edi
push esi ; edi, esi are callee save
mov edi, [ebp-12] ; dest
mov esi, [ebp-8] ; source
mov ecx, [ebp-4] ; length
cld ; ensure we are incrementing
rep movsb
.endf:
mov eax, [ebp-12] ; return pointer to dest
pop esi
pop edi
ret
; Static Values
vga_buf_pos_x:
db 0x00
vga_buf_pos_y:
db 0x00
; Strings
%define StrCRLF_NUL 0Dh, 0Ah, 00h
welcome_cstr:
db 'CBoot Stage3', StrCRLF_NUL
version_cstr:
db 'CBoot v0.0.3 ', 'NASM - ', __NASM_VER__, StrCRLF_NUL
datetime_cstr:
db 'Assembled - ', __DATE__, ' ', __TIME__, StrCRLF_NUL
ALIGN 16, db 0
stack_bottom:
times (512 * 8) db 0x00 ; 4KiB stack
stack_top:
%assign bytes_remaining ((MAX_BYTES - 4) - ($ - $$))
%warning boot32 has bytes_remaining bytes remaining for code (MAX: MMAX_BYTES)
times ((MAX_BYTES - 4) - ($ - $$)) db 0xFE
BOOT_SIG: dd 0xA0B0C0D0

1182
src/stage2/stage2.s Executable file

File diff suppressed because it is too large Load Diff

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