252 lines
6.5 KiB
ArmAsm
252 lines
6.5 KiB
ArmAsm
// SPDX-License-Identifier: GPL-2.0
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//
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// header.S supports booting directly from a UEFI BIOS or via an intermediate
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// bootloader that supports the Linux boot protocol. When booted directly from
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// the BIOS, it provides the MS-DOS & PE/COFF headers. When using an intermediate
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// bootloader, it provides the first few bytes of the Linux boot header (at the
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// end of the boot sector), with the remainder of the header being provided by
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// setup.S.
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//
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// Copyright (C) 2020-2023 Martin Whitaker.
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//
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// Derived from Linux 5.6 arch/x86/boot/header.S:
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//
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// Copyright (C) 1991, 1992 Linus Torvalds
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//
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// Based on bootsect.S and setup.S
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// modified by more people than can be counted
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//
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// Rewritten as a common file by H. Peter Anvin (Apr 2007)
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#define __ASSEMBLY__
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#include "boot.h"
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#include "peimage.h"
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# The EFI loader loads the header at ImageBase, so we have to locate the main program
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# after that. This means we can't load the main program at HIGH_LOAD_ADDR. Pick a load
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# address well away from HIGH_LOAD_ADDR, to avoid overlap when relocating the code.
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#define IMAGE_BASE 0x200000
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.section ".header", "ax", @progbits
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.code16
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.globl boot
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boot:
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# "MZ", the MS-DOS header signature.
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.byte 0x4d
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.byte 0x5a
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# In case we are booted by a legacy BIOS, print an error message.
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# Fortunately the MS-DOS header translates to harmless instructions.
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ljmp $BOOT_SEG, $(error - boot)
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error:
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movw %cs, %ax
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movw %ax, %ds
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movw %ax, %es
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movw %ax, %ss
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xorw %sp, %sp
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sti
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cld
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movw $error_msg, %si
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0: lodsb
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andb %al, %al
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jz wait
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movb $0xe, %ah
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movw $7, %bx
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int $0x10
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jmp 0b
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wait:
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# Allow the user to press a key, then reboot.
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xorw %ax, %ax
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int $0x16
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int $0x19
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# int 0x19 should never return. In case it does, invoke the BIOS.
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# reset code.
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ljmp $0xf000,$0xfff0
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# The PE header pointer.
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.org 0x3c
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.long pe_header
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error_msg:
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.ascii "This is a UEFI bootable image\r\n"
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.ascii "\n"
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.asciz "Press any key to reboot\r\n"
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pe_header:
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.ascii "PE"
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.word 0
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coff_header:
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#ifdef __x86_64__
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.word IMAGE_FILE_MACHINE_X64 # Machine (x86-64)
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#else
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.word IMAGE_FILE_MACHINE_I386 # Machine (i386)
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#endif
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.word 3 # NumberOfSections
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.long 0 # TimeDateStamp
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.long 0 # PointerToSymbolTable
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.long 0 # NumberOfSymbols
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.word section_table - optional_header # SizeOfOptionalHeader
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#ifdef __x86_64__
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.word IMAGE_FILE_DEBUG_STRIPPED \
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| IMAGE_FILE_LOCAL_SYMS_STRIPPED \
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| IMAGE_FILE_LINE_NUMS_STRIPPED \
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| IMAGE_FILE_EXECUTABLE_IMAGE # Characteristics
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#else
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.word IMAGE_FILE_32BIT_MACHINE \
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| IMAGE_FILE_DEBUG_STRIPPED \
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| IMAGE_FILE_LOCAL_SYMS_STRIPPED \
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| IMAGE_FILE_LINE_NUMS_STRIPPED \
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| IMAGE_FILE_EXECUTABLE_IMAGE # Characteristics.
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#endif
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optional_header:
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#ifdef __x86_64__
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.word IMAGE_NT_OPTIONAL_HDR64_MAGIC # PE32+ format
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#else
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.word IMAGE_NT_OPTIONAL_HDR32_MAGIC # PE32 format
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#endif
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.byte 0x02 # MajorLinkerVersion
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.byte 0x14 # MinorLinkerVersion
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.long _virt_text_size # SizeOfCode
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.long _virt_sbat_size # SizeOfInitializedData
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.long 0 # SizeOfUninitializedData
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.long _virt_text_start + 0x1e0 # AddressOfEntryPoint
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.long _virt_text_start # BaseOfCode
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#ifndef __x86_64__
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.long _virt_sbat_start # BaseOfData
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#endif
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extra_header_fields:
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#ifdef __x86_64__
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.quad IMAGE_BASE # ImageBase
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#else
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.long IMAGE_BASE # ImageBase
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#endif
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.long 4096 # SectionAlignment
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.long 512 # FileAlignment
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.word 0 # MajorOperatingSystemVersion
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.word 0 # MinorOperatingSystemVersion
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.word 0 # MajorImageVersion
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.word 0 # MinorImageVersion
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.word 0 # MajorSubsystemVersion
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.word 0 # MinorSubsystemVersion
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.long 0 # Win32VersionValue
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.long _virt_img_size # SizeOfImage
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.long _file_head_size # SizeOfHeaders
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.long 0 # CheckSum
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.word 10 # Subsystem (EFI application)
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.word 0 # DllCharacteristics
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#ifdef __x86_64__
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.quad 0 # SizeOfStackReserve
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.quad 0 # SizeOfStackCommit
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.quad 0 # SizeOfHeapReserve
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.quad 0 # SizeOfHeapCommit
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#else
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.long 0 # SizeOfStackReserve
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.long 0 # SizeOfStackCommit
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.long 0 # SizeOfHeapReserve
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.long 0 # SizeOfHeapCommit
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#endif
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.long 0 # LoaderFlags
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.long IMAGE_DIRECTORY_ENTRY_DEBUG # NumberOfRvaAndSizes
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.long 0 # DataDirectory.Export.VirtualAddress
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.long 0 # DataDirectory.Export.Size
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.long 0 # DataDirectory.Import.VirtualAddress
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.long 0 # DataDirectory.Import.Size
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.long 0 # DataDirectory.Resource.VirtualAddress
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.long 0 # DataDirectory.Resource.Size
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.long 0 # DataDirectory.Exception.VirtualAddress
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.long 0 # DataDirectory.Exception.Size
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.long 0 # DataDirectory.Certs.VirtualAddress
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.long 0 # DataDirectory.Certs.Size
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.long _virt_reloc_start # DataDirectory.BaseReloc.VirtualAddress
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.long _real_reloc_size # DataDirectory.BaseReloc.Size
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# Section table
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section_table:
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.ascii ".text"
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.byte 0
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.byte 0
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.byte 0
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.long _virt_text_size # VirtualSize
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.long _virt_text_start # VirtualAddress
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.long _file_text_size # SizeOfRawData
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.long _file_text_start # PointerToRawData
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.long 0 # PointerToRelocations
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.long 0 # PointerToLineNumbers
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.word 0 # NumberOfRelocations
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.word 0 # NumberOfLineNumbers
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.long IMAGE_SCN_MEM_READ \
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| IMAGE_SCN_MEM_EXECUTE \
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| IMAGE_SCN_CNT_CODE # Characteristics (section flags)
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.ascii ".reloc"
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.byte 0
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.byte 0
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.long _virt_reloc_size # VirtualSize
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.long _virt_reloc_start # VirtualAddress
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.long _file_reloc_size # SizeOfRawData
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.long _file_reloc_start # PointerToRawData
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.long 0 # PointerToRelocations
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.long 0 # PointerToLineNumbers
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.word 0 # NumberOfRelocations
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.word 0 # NumberOfLineNumbers
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.long IMAGE_SCN_MEM_READ \
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| IMAGE_SCN_CNT_INITIALIZED_DATA # Characteristics (section flags)
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.ascii ".sbat"
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.byte 0
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.byte 0
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.byte 0
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.long _virt_sbat_size # VirtualSize
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.long _virt_sbat_start # VirtualAddress
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.long _file_sbat_size # SizeOfRawData
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.long _file_sbat_start # PointerToRawData
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.long 0 # PointerToRelocations
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.long 0 # PointerToLineNumbers
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.word 0 # NumberOfRelocations
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.word 0 # NumberOfLineNumbers
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.long IMAGE_SCN_MEM_READ \
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| IMAGE_SCN_CNT_INITIALIZED_DATA # Characteristics (section flags)
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# Emulate the Linux boot header, to allow loading by intermediate boot loaders.
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.org 497
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setup_sects:
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.byte SETUP_SECS
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root_flags:
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.word 0
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sys_size:
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.long _sys_size
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ram_size:
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.word 0
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vid_mode:
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.word 0
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root_dev:
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.word 0
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boot_flag:
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.word 0xAA55
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.org 512
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.section ".reloc"
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.long 0 // Page RVA
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.long 10 // Block Size (2*4+2)
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.word (IMAGE_REL_BASED_ABSOLUTE << 12) + 0 // reloc 0 -> 0
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.section ".sbat", "a", @progbits
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.incbin "../boot/sbat.csv"
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