Bootloader: Start work on bootloader

I wrote a fast first stage bootloader and a installer to put it into
a disk image.
This commit is contained in:
Bananymous 2023-11-09 22:42:47 +02:00
parent 430a006acf
commit c47f6a78bc
15 changed files with 984 additions and 0 deletions

3
bootloader/.gitignore vendored Normal file
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test.img
build/
installer/build/

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# FIXME: don't assume 512 byte sectors
.set SECTOR_SIZE, 512
.set GPT_HEADER_ADDR, free_memory_start
.set GPT_ENTRY_ADDR, free_memory_start + SECTOR_SIZE
.code16
#########################################
#
# STAGE 1 BOOTLOADER
#
# its sole purpose is to load stage2 from
# bios boot partition
#
#########################################
.section .stage1
stage1_start:
jmp main
# al: character to print
putc:
mov $0x0E, %ah
int $0x10
ret
# ds:si: null terminated string to print
puts:
push %si
push %ax
1:
lodsb
test %al, %al
jz 2f
call putc
jmp 1b
2:
mov $'\r', %al
call putc
mov $'\n', %al
call putc
pop %ax
pop %si
ret
# si: ptr1
# di: ptr2
# cx: count
# return: 1 if equal, 0 otherwise
memcmp:
pushw %si
pushw %di
cld
repe cmpsb
setzb %al
popw %di
popw %si
ret
# read sectors from disk
#
# bx:eax: lba start
# cx: lba count (has to less than 0x80)
# dl: drive number
# ds:di: physical address
#
# returns only on success
read_from_disk:
push %ax
push %si
# prepare disk read packet
mov $disk_address_packet, %si
movb $0x10, 0x00(%si) # packet size
movb $0x00, 0x01(%si) # always 0
movw %cx, 0x02(%si) # lba count
movw %di, 0x04(%si) # offset
movw %ds, 0x06(%si) # segment
movl %eax, 0x08(%si) # 32 bit lower lba
movw %bx, 0x0C(%si) # 16 bit upper lba
movw $0, 0x0E(%si) # zero
# issue read command
clc
mov $0x42, %ah
int $0x13
jc .read_failed
pop %si
pop %ax
ret
main:
# setup segments
movw $0, %ax
movw %ax, %ds
movw %ax, %es
# setup stack
movw %ax, %ss
movw $0x7C00, %sp
# save boot disk number
movb %dl, (boot_disk_number)
# confirm that int 13h extensions are available
clc
movb $0x41, %ah
movw $0x55AA, %bx
movb (boot_disk_number), %dl
int $0x13
jc .no_int13h_ext
# read gpt header
movl $1, %eax
movw $0, %bx
movw $1, %cx
movb (boot_disk_number), %dl
movw $GPT_HEADER_ADDR, %di
call read_from_disk
# confirm header (starts with 'EFI PART')
cmpl $0x20494645, (GPT_HEADER_ADDR + 0)
jne .not_gpt_partition
cmpl $0x54524150, (GPT_HEADER_ADDR + 4)
jne .not_gpt_partition
# eax := entry_count
movl (GPT_HEADER_ADDR + 80), %eax
test %eax, %eax
jz .no_bios_boot_partition
# edx:eax := eax * entry_size
mull (GPT_HEADER_ADDR + 84)
test %edx, %edx
jnz .too_gpt_big_entries
# sector count := (arr_size + SECTOR_SIZE - 1) / SECTOR_SIZE
pushl %eax
addl $(SECTOR_SIZE - 1), %eax
movl $SECTOR_SIZE, %ecx
divl %ecx
movl %eax, %ecx
popl %eax
# start lba
movl (GPT_HEADER_ADDR + 72), %eax
movw (GPT_HEADER_ADDR + 76), %bx
movb (boot_disk_number), %dl
movw $GPT_ENTRY_ADDR, %di
call read_from_disk
# NOTE: 'only' 0xFFFF partitions supported
movw (GPT_HEADER_ADDR + 80), %cx
.loop_entries:
push %cx
movw $16, %cx
movw $bios_boot_guid, %si
call memcmp
pop %cx
testb %al, %al
jnz .bios_boot_found
# add entry size to entry pointer
addw (GPT_HEADER_ADDR + 84), %di
loop .loop_entries
jmp .no_bios_boot_partition
.bios_boot_found:
# first lba
movl 32(%di), %eax
movw $0, %bx
# count := last lba - first lba + 1
movl 40(%di), %ecx
subl %eax, %ecx
addl $1, %ecx
# calculate stage2 sector count
movw $((stage2_end - stage2_start + SECTOR_SIZE - 1) / SECTOR_SIZE), %cx
movb (boot_disk_number), %dl
movw $stage2_start, %di
call read_from_disk
jmp stage2_start
print_and_halt:
call puts
halt:
hlt
jmp halt
.no_int13h_ext:
mov $no_int13_ext_msg, %si
jmp print_and_halt
.read_failed:
mov $read_failed_msg, %si
jmp print_and_halt
.not_gpt_partition:
mov $not_gpt_partition_msg, %si
jmp print_and_halt
.no_bios_boot_partition:
mov $no_bios_boot_partition_msg, %si
jmp print_and_halt
.too_gpt_big_entries:
mov $too_gpt_big_entries_msg, %si
jmp print_and_halt
# 21686148-6449-6E6F-744E-656564454649
bios_boot_guid:
.long 0x21686148 # little endian
.word 0x6449 # little endian
.word 0x6E6F # little endian
.word 0x4E74 # big endian
.quad 0x494645646565 # big endian
no_int13_ext_msg:
.asciz "no INT 13h ext"
read_failed_msg:
.asciz "read error"
not_gpt_partition_msg:
.asciz "not gpt"
no_bios_boot_partition_msg:
.asciz "no bios boot partition"
too_gpt_big_entries_msg:
.asciz "too big GPT array"
boot_disk_number:
.skip 1
disk_address_packet:
.skip 16
#########################################
#
# STAGE 2 BOOTLOADER
#
#########################################
.section .stage2
stage2_start:
# clear screen and enter 80x25 text mode
movb $0x03, %al
movb $0x00, %ah
int $0x10
# print hello message
movw $hello_msg, %si
call puts
1:
jmp 1b
hello_msg:
.asciz "This is banan-os bootloader"
stage2_end:

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SECTIONS
{
. = 0x7C00;
.stage1 : { *(.stage1*) }
. = ALIGN(512);
.stage2 : { *(.stage2) }
. = ALIGN(512);
free_memory_start = .;
}

45
bootloader/build-and-run.sh Executable file
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#!/bin/sh
set -e
CURRENT_DIR=$(dirname $(realpath $0))
INSTALLER_DIR=$CURRENT_DIR/installer
INSTALLER_BUILD_DIR=$INSTALLER_DIR/build
BUILD_DIR=$CURRENT_DIR/build
DISK_IMAGE_PATH=$CURRENT_DIR/test.img
if ! [ -d $INSTALLER_BUILD_DIR ]; then
mkdir -p $INSTALLER_BUILD_DIR
cd $INSTALLER_BUILD_DIR
cmake ..
fi
cd $INSTALLER_BUILD_DIR
make
cd $CURRENT_DIR
echo creating clean disk image
truncate --size 0 $DISK_IMAGE_PATH
truncate --size 50M $DISK_IMAGE_PATH
echo -ne 'g\nn\n\n\n+1M\nt 1\n4\nw\n' | fdisk $DISK_IMAGE_PATH > /dev/null
mkdir -p $BUILD_DIR
echo compiling bootloader
x86_64-banan_os-as arch/x86_64/boot.S -o $BUILD_DIR/bootloader.o
echo linking bootloader
x86_64-banan_os-ld -nostdlib -T arch/x86_64/linker.ld $BUILD_DIR/bootloader.o -o $BUILD_DIR/bootloader
echo installing bootloader
$INSTALLER_BUILD_DIR/x86_64-banan_os-bootloader-installer $BUILD_DIR/bootloader $DISK_IMAGE_PATH
if [ "$1" == "debug" ] ; then
QEMU_FLAGS="-s -S"
fi
echo running qemu
qemu-system-x86_64 $QEMU_FLAGS --drive format=raw,file=test.img

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cmake_minimum_required(VERSION 3.26)
project(x86_64-banan_os-bootloader-installer CXX)
set(SOURCES
crc32.cpp
ELF.cpp
GPT.cpp
GUID.cpp
main.cpp
)
add_executable(x86_64-banan_os-bootloader-installer ${SOURCES})
target_compile_options(x86_64-banan_os-bootloader-installer PUBLIC -O2 -std=c++20)

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#include "ELF.h"
#include <cassert>
#include <cerrno>
#include <cstring>
#include <fcntl.h>
#include <iostream>
#include <sys/mman.h>
#include <unistd.h>
ELFFile::ELFFile(std::string_view path)
: m_path(path)
{
m_fd = open(m_path.c_str(), O_RDONLY);
if (m_fd == -1)
{
std::cerr << "Could not open '" << m_path << "': " << std::strerror(errno) << std::endl;
return;
}
if (fstat(m_fd, &m_stat) == -1)
{
std::cerr << "Could not stat '" << m_path << "': " << std::strerror(errno) << std::endl;
return;
}
void* mmap_addr = mmap(nullptr, m_stat.st_size, PROT_READ, MAP_PRIVATE, m_fd, 0);
if (mmap_addr == MAP_FAILED)
{
std::cerr << "Could not mmap '" << m_path << "': " << std::strerror(errno) << std::endl;
return;
}
m_mmap = reinterpret_cast<uint8_t*>(mmap_addr);
if (!validate_elf_header())
return;
m_success = true;
}
ELFFile::~ELFFile()
{
if (m_mmap)
munmap(m_mmap, m_stat.st_size);
m_mmap = nullptr;
if (m_fd != -1)
close(m_fd);
m_fd = -1;
}
const Elf64_Ehdr& ELFFile::elf_header() const
{
return *reinterpret_cast<Elf64_Ehdr*>(m_mmap);
}
bool ELFFile::validate_elf_header() const
{
if (m_stat.st_size < sizeof(Elf64_Ehdr))
{
std::cerr << m_path << " is too small to be a ELF executable" << std::endl;
return false;
}
const auto& elf_header = this->elf_header();
if (
elf_header.e_ident[EI_MAG0] != ELFMAG0 ||
elf_header.e_ident[EI_MAG1] != ELFMAG1 ||
elf_header.e_ident[EI_MAG2] != ELFMAG2 ||
elf_header.e_ident[EI_MAG3] != ELFMAG3
)
{
std::cerr << m_path << " doesn't have an ELF magic number" << std::endl;
return false;
}
if (elf_header.e_ident[EI_CLASS] != ELFCLASS64)
{
std::cerr << m_path << " is not 64 bit ELF" << std::endl;
return false;
}
if (elf_header.e_ident[EI_DATA] != ELFDATA2LSB)
{
std::cerr << m_path << " is not in little endian format" << std::endl;
return false;
}
if (elf_header.e_ident[EI_VERSION] != EV_CURRENT)
{
std::cerr << m_path << " has unsupported version" << std::endl;
return false;
}
if (elf_header.e_type != ET_EXEC)
{
std::cerr << m_path << " is not an executable ELF file" << std::endl;
return false;
}
if (elf_header.e_machine != EM_X86_64)
{
std::cerr << m_path << " is not an x86_64 ELF file" << std::endl;
return false;
}
return true;
}
const Elf64_Shdr& ELFFile::section_header(std::size_t index) const
{
const auto& elf_header = this->elf_header();
assert(index < elf_header.e_shnum);
const uint8_t* section_array_start = m_mmap + elf_header.e_shoff;
return *reinterpret_cast<const Elf64_Shdr*>(section_array_start + index * elf_header.e_shentsize);
}
std::string_view ELFFile::section_name(const Elf64_Shdr& section_header) const
{
const auto& elf_header = this->elf_header();
assert(elf_header.e_shstrndx != SHN_UNDEF);
const auto& section_string_table = this->section_header(elf_header.e_shstrndx);
const char* string_table_start = reinterpret_cast<const char*>(m_mmap + section_string_table.sh_offset);
return string_table_start + section_header.sh_name;
}
std::optional<std::span<const uint8_t>> ELFFile::find_section(std::string_view name) const
{
const auto& elf_header = this->elf_header();
for (std::size_t i = 0; i < elf_header.e_shnum; i++)
{
const auto& section_header = this->section_header(i);
auto section_name = this->section_name(section_header);
if (section_name != name)
continue;
return std::span<const uint8_t>(m_mmap + section_header.sh_offset, section_header.sh_size);
}
return {};
}

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#pragma once
#include <cstdint>
#include <optional>
#include <span>
#include <string_view>
#include <string>
#include <sys/stat.h>
#include <elf.h>
class ELFFile
{
public:
ELFFile(std::string_view path);
~ELFFile();
const Elf64_Ehdr& elf_header() const;
std::optional<std::span<const uint8_t>> find_section(std::string_view name) const;
bool success() const { return m_success; }
std::string_view path() const { return m_path; }
private:
const Elf64_Shdr& section_header(std::size_t index) const;
std::string_view section_name(const Elf64_Shdr&) const;
bool validate_elf_header() const;
private:
const std::string m_path;
bool m_success { false };
int m_fd { -1 };
struct stat m_stat { };
uint8_t* m_mmap { nullptr };
};

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#include "crc32.h"
#include "GPT.h"
#include <cassert>
#include <cerrno>
#include <cstring>
#include <fcntl.h>
#include <iostream>
#include <sys/mman.h>
#include <unistd.h>
// FIXME: don't assume 512 byte sectors
#define SECTOR_SIZE 512
GPTFile::GPTFile(std::string_view path)
: m_path(path)
{
m_fd = open(m_path.c_str(), O_RDWR);
if (m_fd == -1)
{
std::cerr << "Could not open '" << m_path << "': " << std::strerror(errno) << std::endl;
return;
}
if (fstat(m_fd, &m_stat) == -1)
{
std::cerr << "Could not stat '" << m_path << "': " << std::strerror(errno) << std::endl;
return;
}
void* mmap_addr = mmap(nullptr, m_stat.st_size, PROT_READ | PROT_WRITE, MAP_SHARED, m_fd, 0);
if (mmap_addr == MAP_FAILED)
{
std::cerr << "Could not mmap '" << m_path << "': " << std::strerror(errno) << std::endl;
return;
}
m_mmap = reinterpret_cast<uint8_t*>(mmap_addr);
if (!validate_gpt_header())
return;
m_success = true;
}
GPTFile::~GPTFile()
{
if (m_mmap)
munmap(m_mmap, m_stat.st_size);
m_mmap = nullptr;
if (m_fd != -1)
close(m_fd);
m_fd = -1;
}
MBR& GPTFile::mbr()
{
return *reinterpret_cast<MBR*>(m_mmap);
}
const GPTHeader& GPTFile::gpt_header() const
{
return *reinterpret_cast<GPTHeader*>(m_mmap + SECTOR_SIZE);
}
bool GPTFile::install_bootcode(std::span<const uint8_t> boot_code)
{
auto& mbr = this->mbr();
if (boot_code.size() > sizeof(mbr.boot_code))
{
std::cerr << m_path << ": can't fit " << boot_code.size() << " bytes of boot code in mbr (max is " << sizeof(mbr.boot_code) << ")" << std::endl;
return false;
}
// copy boot code
memcpy(mbr.boot_code, boot_code.data(), boot_code.size());
// setup mbr
mbr.unique_mbr_disk_signature = 0xdeadbeef;
mbr.unknown = 0;
mbr.signature = 0xAA55;
// setup mbr partition records
mbr.partition_records[0].boot_indicator = 0x00;
mbr.partition_records[0].starting_chs[0] = 0x00;
mbr.partition_records[0].starting_chs[1] = 0x02;
mbr.partition_records[0].starting_chs[2] = 0x00;
mbr.partition_records[0].os_type = 0xEE;
mbr.partition_records[0].ending_chs[0] = 0xFF;
mbr.partition_records[0].ending_chs[1] = 0xFF;
mbr.partition_records[0].ending_chs[2] = 0xFF;
mbr.partition_records[0].starting_lba = 1;
mbr.partition_records[0].size_in_lba = 0xFFFFFFFF;
memset(&mbr.partition_records[1], 0x00, sizeof(MBRPartitionRecord));
memset(&mbr.partition_records[2], 0x00, sizeof(MBRPartitionRecord));
memset(&mbr.partition_records[3], 0x00, sizeof(MBRPartitionRecord));
return true;
}
bool GPTFile::write_partition(std::span<const uint8_t> data, GUID type_guid)
{
auto partition = find_partition(type_guid);
if (!partition.has_value())
{
std::cerr << m_path << ": could not find partition with type " << type_guid << std::endl;
return false;
}
const std::size_t partition_size = (partition->ending_lba - partition->starting_lba + 1) * SECTOR_SIZE;
if (data.size() > partition_size)
{
std::cerr << m_path << ": can't fit " << data.size() << " bytes of data to partition of size " << partition_size << std::endl;
return false;
}
memcpy(m_mmap + partition->starting_lba * SECTOR_SIZE, data.data(), data.size());
return true;
}
std::optional<GPTPartitionEntry> GPTFile::find_partition(const GUID& type_guid) const
{
const auto& gpt_header = this->gpt_header();
const uint8_t* partition_entry_array_start = m_mmap + gpt_header.partition_entry_lba * SECTOR_SIZE;
for (std::size_t i = 0; i < gpt_header.number_of_partition_entries; i++)
{
const auto& partition_entry = *reinterpret_cast<const GPTPartitionEntry*>(partition_entry_array_start + i * gpt_header.size_of_partition_entry);
if (partition_entry.type_guid != type_guid)
continue;
return partition_entry;
}
return {};
}
bool GPTFile::validate_gpt_header() const
{
if (SECTOR_SIZE + m_stat.st_size < sizeof(GPTHeader))
{
std::cerr << m_path << " is too small to have GPT header" << std::endl;
return false;
}
auto gpt_header = this->gpt_header();
if (std::memcmp(gpt_header.signature, "EFI PART", 8) != 0)
{
std::cerr << m_path << " doesn't contain GPT partition header signature" << std::endl;
return false;
}
const uint32_t header_crc32 = gpt_header.header_crc32;
gpt_header.header_crc32 = 0;
if (header_crc32 != crc32_checksum(reinterpret_cast<uint8_t*>(&gpt_header), gpt_header.header_size))
{
std::cerr << m_path << " has non-matching header crc32" << std::endl;
return false;
}
const std::size_t partition_array_size = gpt_header.number_of_partition_entries * gpt_header.size_of_partition_entry;
if (gpt_header.partition_entry_array_crc32 != crc32_checksum(m_mmap + gpt_header.partition_entry_lba * SECTOR_SIZE, partition_array_size))
{
std::cerr << m_path << " has non-matching partition entry crc32" << std::endl;
return false;
}
return true;
}

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#pragma once
#include "GUID.h"
#include <cstdint>
#include <optional>
#include <span>
#include <string_view>
#include <string>
#include <sys/stat.h>
struct MBRPartitionRecord
{
uint8_t boot_indicator;
uint8_t starting_chs[3];
uint8_t os_type;
uint8_t ending_chs[3];
uint32_t starting_lba;
uint32_t size_in_lba;
} __attribute__((packed));
struct MBR
{
uint8_t boot_code[440];
uint32_t unique_mbr_disk_signature;
uint16_t unknown;
MBRPartitionRecord partition_records[4];
uint16_t signature;
} __attribute__((packed));
static_assert(sizeof(MBR) == 512);
struct GPTPartitionEntry
{
GUID type_guid;
GUID partition_guid;
uint64_t starting_lba;
uint64_t ending_lba;
uint64_t attributes;
uint16_t name[36];
};
static_assert(sizeof(GPTPartitionEntry) == 128);
struct GPTHeader
{
char signature[8];
uint32_t revision;
uint32_t header_size;
uint32_t header_crc32;
uint32_t reserved;
uint64_t my_lba;
uint64_t alternate_lba;
uint64_t first_usable_lba;
uint64_t last_usable_lba;
GUID disk_guid;
uint64_t partition_entry_lba;
uint32_t number_of_partition_entries;
uint32_t size_of_partition_entry;
uint32_t partition_entry_array_crc32;
} __attribute__((packed));
static_assert(sizeof(GPTHeader) == 92);
class GPTFile
{
public:
GPTFile(std::string_view path);
~GPTFile();
bool install_bootcode(std::span<const uint8_t>);
bool write_partition(std::span<const uint8_t>, GUID type_guid);
const GPTHeader& gpt_header() const;
bool success() const { return m_success; }
std::string_view path() const { return m_path; }
private:
MBR& mbr();
bool validate_gpt_header() const;
std::optional<GPTPartitionEntry> find_partition(const GUID& type_guid) const;
private:
const std::string m_path;
bool m_success { false };
int m_fd { -1 };
struct stat m_stat { };
uint8_t* m_mmap { nullptr };
};

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#include "GUID.h"
#include <iomanip>
#include <cstring>
bool GUID::operator==(const GUID& other) const
{
return std::memcmp(this, &other, sizeof(GUID)) == 0;
}
std::ostream& operator<<(std::ostream& out, const GUID& guid)
{
auto flags = out.flags();
out << std::hex << std::setfill('0');
out << std::setw(8) << guid.component1 << '-';
out << std::setw(4) << guid.component2 << '-';
out << std::setw(4) << guid.component3 << '-';
out << std::setw(2);
for (int i = 0; i < 2; i++) out << +guid.component45[i];
out << '-';
for (int i = 2; i < 6; i++) out << +guid.component45[i];
out.flags(flags);
return out;
}

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#pragma once
#include <cstdint>
#include <ostream>
struct GUID
{
uint32_t component1;
uint16_t component2;
uint16_t component3;
// last 2 components are combined so no packed needed
uint8_t component45[8];
bool operator==(const GUID& other) const;
};
std::ostream& operator<<(std::ostream& out, const GUID& guid);
// unused 00000000-0000-0000-0000-000000000000
static constexpr GUID unused_guid = {
0x00000000,
0x0000,
0x0000,
{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }
};
// bios boot 21686148-6449-6E6F-744E-656564454649
static constexpr GUID bios_boot_guid = {
0x21686148,
0x6449,
0x6E6F,
{ 0x74, 0x4E, 0x65, 0x65, 0x64, 0x45, 0x46, 0x49 }
};

3
bootloader/installer/build.sh Executable file
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#!/bin/sh
g++ -O2 -std=c++20 main.cpp crc32.cpp ELF.cpp GPT.cpp GUID.cpp -o install-bootloader

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#include "crc32.h"
static constexpr uint32_t crc32_table[256] =
{
0x00000000, 0x77073096, 0xEE0E612C, 0x990951BA,
0x076DC419, 0x706AF48F, 0xE963A535, 0x9E6495A3,
0x0EDB8832, 0x79DCB8A4, 0xE0D5E91E, 0x97D2D988,
0x09B64C2B, 0x7EB17CBD, 0xE7B82D07, 0x90BF1D91,
0x1DB71064, 0x6AB020F2, 0xF3B97148, 0x84BE41DE,
0x1ADAD47D, 0x6DDDE4EB, 0xF4D4B551, 0x83D385C7,
0x136C9856, 0x646BA8C0, 0xFD62F97A, 0x8A65C9EC,
0x14015C4F, 0x63066CD9, 0xFA0F3D63, 0x8D080DF5,
0x3B6E20C8, 0x4C69105E, 0xD56041E4, 0xA2677172,
0x3C03E4D1, 0x4B04D447, 0xD20D85FD, 0xA50AB56B,
0x35B5A8FA, 0x42B2986C, 0xDBBBC9D6, 0xACBCF940,
0x32D86CE3, 0x45DF5C75, 0xDCD60DCF, 0xABD13D59,
0x26D930AC, 0x51DE003A, 0xC8D75180, 0xBFD06116,
0x21B4F4B5, 0x56B3C423, 0xCFBA9599, 0xB8BDA50F,
0x2802B89E, 0x5F058808, 0xC60CD9B2, 0xB10BE924,
0x2F6F7C87, 0x58684C11, 0xC1611DAB, 0xB6662D3D,
0x76DC4190, 0x01DB7106, 0x98D220BC, 0xEFD5102A,
0x71B18589, 0x06B6B51F, 0x9FBFE4A5, 0xE8B8D433,
0x7807C9A2, 0x0F00F934, 0x9609A88E, 0xE10E9818,
0x7F6A0DBB, 0x086D3D2D, 0x91646C97, 0xE6635C01,
0x6B6B51F4, 0x1C6C6162, 0x856530D8, 0xF262004E,
0x6C0695ED, 0x1B01A57B, 0x8208F4C1, 0xF50FC457,
0x65B0D9C6, 0x12B7E950, 0x8BBEB8EA, 0xFCB9887C,
0x62DD1DDF, 0x15DA2D49, 0x8CD37CF3, 0xFBD44C65,
0x4DB26158, 0x3AB551CE, 0xA3BC0074, 0xD4BB30E2,
0x4ADFA541, 0x3DD895D7, 0xA4D1C46D, 0xD3D6F4FB,
0x4369E96A, 0x346ED9FC, 0xAD678846, 0xDA60B8D0,
0x44042D73, 0x33031DE5, 0xAA0A4C5F, 0xDD0D7CC9,
0x5005713C, 0x270241AA, 0xBE0B1010, 0xC90C2086,
0x5768B525, 0x206F85B3, 0xB966D409, 0xCE61E49F,
0x5EDEF90E, 0x29D9C998, 0xB0D09822, 0xC7D7A8B4,
0x59B33D17, 0x2EB40D81, 0xB7BD5C3B, 0xC0BA6CAD,
0xEDB88320, 0x9ABFB3B6, 0x03B6E20C, 0x74B1D29A,
0xEAD54739, 0x9DD277AF, 0x04DB2615, 0x73DC1683,
0xE3630B12, 0x94643B84, 0x0D6D6A3E, 0x7A6A5AA8,
0xE40ECF0B, 0x9309FF9D, 0x0A00AE27, 0x7D079EB1,
0xF00F9344, 0x8708A3D2, 0x1E01F268, 0x6906C2FE,
0xF762575D, 0x806567CB, 0x196C3671, 0x6E6B06E7,
0xFED41B76, 0x89D32BE0, 0x10DA7A5A, 0x67DD4ACC,
0xF9B9DF6F, 0x8EBEEFF9, 0x17B7BE43, 0x60B08ED5,
0xD6D6A3E8, 0xA1D1937E, 0x38D8C2C4, 0x4FDFF252,
0xD1BB67F1, 0xA6BC5767, 0x3FB506DD, 0x48B2364B,
0xD80D2BDA, 0xAF0A1B4C, 0x36034AF6, 0x41047A60,
0xDF60EFC3, 0xA867DF55, 0x316E8EEF, 0x4669BE79,
0xCB61B38C, 0xBC66831A, 0x256FD2A0, 0x5268E236,
0xCC0C7795, 0xBB0B4703, 0x220216B9, 0x5505262F,
0xC5BA3BBE, 0xB2BD0B28, 0x2BB45A92, 0x5CB36A04,
0xC2D7FFA7, 0xB5D0CF31, 0x2CD99E8B, 0x5BDEAE1D,
0x9B64C2B0, 0xEC63F226, 0x756AA39C, 0x026D930A,
0x9C0906A9, 0xEB0E363F, 0x72076785, 0x05005713,
0x95BF4A82, 0xE2B87A14, 0x7BB12BAE, 0x0CB61B38,
0x92D28E9B, 0xE5D5BE0D, 0x7CDCEFB7, 0x0BDBDF21,
0x86D3D2D4, 0xF1D4E242, 0x68DDB3F8, 0x1FDA836E,
0x81BE16CD, 0xF6B9265B, 0x6FB077E1, 0x18B74777,
0x88085AE6, 0xFF0F6A70, 0x66063BCA, 0x11010B5C,
0x8F659EFF, 0xF862AE69, 0x616BFFD3, 0x166CCF45,
0xA00AE278, 0xD70DD2EE, 0x4E048354, 0x3903B3C2,
0xA7672661, 0xD06016F7, 0x4969474D, 0x3E6E77DB,
0xAED16A4A, 0xD9D65ADC, 0x40DF0B66, 0x37D83BF0,
0xA9BCAE53, 0xDEBB9EC5, 0x47B2CF7F, 0x30B5FFE9,
0xBDBDF21C, 0xCABAC28A, 0x53B39330, 0x24B4A3A6,
0xBAD03605, 0xCDD70693, 0x54DE5729, 0x23D967BF,
0xB3667A2E, 0xC4614AB8, 0x5D681B02, 0x2A6F2B94,
0xB40BBE37, 0xC30C8EA1, 0x5A05DF1B, 0x2D02EF8D,
};
uint32_t crc32_checksum(const uint8_t* data, std::size_t count)
{
uint32_t crc32 = 0xFFFFFFFF;
for (size_t i = 0; i < count; i++)
{
uint8_t index = (crc32 ^ data[i]) & 0xFF;
crc32 = (crc32 >> 8) ^ crc32_table[index];
}
return crc32 ^ 0xFFFFFFFF;
}

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#pragma once
#include <cstddef>
#include <cstdint>
uint32_t crc32_checksum(const uint8_t* data, std::size_t count);

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#include "ELF.h"
#include "GPT.h"
#include <iostream>
int main(int argc, char** argv)
{
using namespace std::string_view_literals;
if (argc != 3)
{
std::fprintf(stderr, "usage: %s BOOTLOADER DISK_IMAGE}\n", argv[0]);
return 1;
}
ELFFile bootloader(argv[1]);
if (!bootloader.success())
return 1;
auto stage1 = bootloader.find_section(".stage1"sv);
auto stage2 = bootloader.find_section(".stage2"sv);
if (!stage1.has_value() || !stage2.has_value())
{
std::cerr << bootloader.path() << " doesn't contain .stage1 and .stage2 sections" << std::endl;
return 1;
}
GPTFile disk_image(argv[2]);
if (!disk_image.success())
return 1;
if (!disk_image.install_bootcode(*stage1))
return 1;
std::cout << "wrote stage1 bootloader" << std::endl;
if (!disk_image.write_partition(*stage2, bios_boot_guid))
return 1;
std::cout << "wrote stage2 bootloader" << std::endl;
return 0;
}