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e4bae4d0b5
To prevent unintended modifications to the kernel text (malicious or otherwise) while running the EFI stub, describe the kernel image as two separate sections: a .text section with read-execute permissions, covering .text, .rodata, .piggytext and the GOT sections (which the stub does not care about anyway), and a .data section with read-write permissions, covering .data and .bss. This relies on the firmware to actually take the section permission flags into account, but this is something that is currently being implemented in EDK2, which means we will likely start seeing it in the wild between one and two years from now. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Matt Fleming <matt@codeblueprint.co.uk> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Russell King <linux@armlinux.org.uk> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-efi@vger.kernel.org Link: http://lkml.kernel.org/r/20170818194947.19347-12-ard.biesheuvel@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
133 lines
4.1 KiB
ArmAsm
133 lines
4.1 KiB
ArmAsm
/*
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* Copyright (C) 2013-2017 Linaro Ltd
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* Authors: Roy Franz <roy.franz@linaro.org>
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* Ard Biesheuvel <ard.biesheuvel@linaro.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/pe.h>
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#include <linux/sizes.h>
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.macro __nop
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#ifdef CONFIG_EFI_STUB
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@ This is almost but not quite a NOP, since it does clobber the
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@ condition flags. But it is the best we can do for EFI, since
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@ PE/COFF expects the magic string "MZ" at offset 0, while the
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@ ARM/Linux boot protocol expects an executable instruction
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@ there.
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.inst MZ_MAGIC | (0x1310 << 16) @ tstne r0, #0x4d000
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#else
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AR_CLASS( mov r0, r0 )
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M_CLASS( nop.w )
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#endif
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.endm
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.macro __EFI_HEADER
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#ifdef CONFIG_EFI_STUB
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.set start_offset, __efi_start - start
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.org start + 0x3c
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@
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@ The PE header can be anywhere in the file, but for
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@ simplicity we keep it together with the MSDOS header
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@ The offset to the PE/COFF header needs to be at offset
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@ 0x3C in the MSDOS header.
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@ The only 2 fields of the MSDOS header that are used are this
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@ PE/COFF offset, and the "MZ" bytes at offset 0x0.
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@
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.long pe_header - start @ Offset to the PE header.
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pe_header:
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.long PE_MAGIC
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coff_header:
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.short IMAGE_FILE_MACHINE_THUMB @ Machine
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.short section_count @ 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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.short section_table - optional_header @ SizeOfOptionalHeader
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.short IMAGE_FILE_32BIT_MACHINE | \
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IMAGE_FILE_DEBUG_STRIPPED | \
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IMAGE_FILE_EXECUTABLE_IMAGE | \
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IMAGE_FILE_LINE_NUMS_STRIPPED @ Characteristics
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#define __pecoff_code_size (__pecoff_data_start - __efi_start)
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optional_header:
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.short PE_OPT_MAGIC_PE32 @ PE32 format
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.byte 0x02 @ MajorLinkerVersion
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.byte 0x14 @ MinorLinkerVersion
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.long __pecoff_code_size @ SizeOfCode
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.long __pecoff_data_size @ SizeOfInitializedData
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.long 0 @ SizeOfUninitializedData
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.long efi_stub_entry - start @ AddressOfEntryPoint
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.long start_offset @ BaseOfCode
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.long __pecoff_data_start - start @ BaseOfData
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extra_header_fields:
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.long 0 @ ImageBase
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.long SZ_4K @ SectionAlignment
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.long SZ_512 @ FileAlignment
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.short 0 @ MajorOsVersion
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.short 0 @ MinorOsVersion
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.short 0 @ MajorImageVersion
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.short 0 @ MinorImageVersion
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.short 0 @ MajorSubsystemVersion
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.short 0 @ MinorSubsystemVersion
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.long 0 @ Win32VersionValue
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.long __pecoff_end - start @ SizeOfImage
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.long start_offset @ SizeOfHeaders
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.long 0 @ CheckSum
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.short IMAGE_SUBSYSTEM_EFI_APPLICATION @ Subsystem
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.short 0 @ DllCharacteristics
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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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.long 0 @ LoaderFlags
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.long (section_table - .) / 8 @ NumberOfRvaAndSizes
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.quad 0 @ ExportTable
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.quad 0 @ ImportTable
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.quad 0 @ ResourceTable
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.quad 0 @ ExceptionTable
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.quad 0 @ CertificationTable
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.quad 0 @ BaseRelocationTable
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section_table:
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.ascii ".text\0\0\0"
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.long __pecoff_code_size @ VirtualSize
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.long __efi_start @ VirtualAddress
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.long __pecoff_code_size @ SizeOfRawData
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.long __efi_start @ PointerToRawData
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.long 0 @ PointerToRelocations
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.long 0 @ PointerToLineNumbers
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.short 0 @ NumberOfRelocations
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.short 0 @ NumberOfLineNumbers
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.long IMAGE_SCN_CNT_CODE | \
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IMAGE_SCN_MEM_READ | \
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IMAGE_SCN_MEM_EXECUTE @ Characteristics
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.ascii ".data\0\0\0"
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.long __pecoff_data_size @ VirtualSize
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.long __pecoff_data_start - start @ VirtualAddress
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.long __pecoff_data_rawsize @ SizeOfRawData
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.long __pecoff_data_start - start @ PointerToRawData
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.long 0 @ PointerToRelocations
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.long 0 @ PointerToLineNumbers
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.short 0 @ NumberOfRelocations
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.short 0 @ NumberOfLineNumbers
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.long IMAGE_SCN_CNT_INITIALIZED_DATA | \
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IMAGE_SCN_MEM_READ | \
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IMAGE_SCN_MEM_WRITE @ Characteristics
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.set section_count, (. - section_table) / 40
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.align 12
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__efi_start:
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#endif
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.endm
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