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Message-ID: <20170206170334.GD4190@leverpostej>
Date: Mon, 6 Feb 2017 17:03:35 +0000
From: Mark Rutland <mark.rutland@....com>
To: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc: linux-arm-kernel@...ts.infradead.org, will.deacon@....com,
catalin.marinas@....com, labbott@...oraproject.org,
kernel-hardening@...ts.openwall.com, leif.lindholm@...aro.org,
pjones@...hat.com
Subject: Re: [PATCH 3/7] arm64: efi: move EFI header and related data to a
separate .S file
On Mon, Feb 06, 2017 at 04:24:31PM +0000, Ard Biesheuvel wrote:
> In preparation of yet another round of modifications to the PE/COFF
> header, macroize it and move the definition into a separate source
> file.
I'm really not keen on portioning out bits of the arm64 header like
this.
The __jmp macro obscures the first few byes of the header, and we lose
the obvious relationship between the overlapping portions of the arm64
and PE/COFF headrs.
I think those portions which have a fixed offset from _head (which is at
least the overlapping PE/COFF and arm64 header bits) should stay in
head.S.
Can we factor out only the portions with a dynamic offset from the start
of the image? i.e. only pe_header and beyond?
Thanks,
Mark.
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> ---
> arch/arm64/kernel/efi-header.S | 182 ++++++++++++++++++++
> arch/arm64/kernel/head.S | 171 +-----------------
> 2 files changed, 186 insertions(+), 167 deletions(-)
>
> diff --git a/arch/arm64/kernel/efi-header.S b/arch/arm64/kernel/efi-header.S
> new file mode 100644
> index 000000000000..8c8cd0a8192b
> --- /dev/null
> +++ b/arch/arm64/kernel/efi-header.S
> @@ -0,0 +1,182 @@
> +/*
> + * Copyright (C) 2013 - 2017 Linaro, Ltd.
> + * Copyright (C) 2013, 2014 Red Hat, Inc.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> + .macro __jmp, target
> +#ifdef CONFIG_EFI
> + /*
> + * This add instruction has no meaningful effect except that
> + * its opcode forms the magic "MZ" signature required by UEFI.
> + */
> + add x13, x18, #0x16
> + b \target
> +#else
> + b \target // branch to kernel start, magic
> + .long 0 // reserved
> +#endif
> + .endm
> +
> + .macro __EFI_HEADER
> +#ifdef CONFIG_EFI
> + .long pe_header - _head // Offset to the PE header.
> +#else
> + .word 0 // reserved
> +#endif
> +
> +#ifdef CONFIG_EFI
> + .align 3
> +pe_header:
> + .ascii "PE"
> + .short 0
> +coff_header:
> + .short 0xaa64 // AArch64
> + .short 2 // nr_sections
> + .long 0 // TimeDateStamp
> + .long 0 // PointerToSymbolTable
> + .long 1 // NumberOfSymbols
> + .short section_table - optional_header // SizeOfOptionalHeader
> + .short 0x206 // Characteristics.
> + // IMAGE_FILE_DEBUG_STRIPPED |
> + // IMAGE_FILE_EXECUTABLE_IMAGE |
> + // IMAGE_FILE_LINE_NUMS_STRIPPED
> +optional_header:
> + .short 0x20b // PE32+ format
> + .byte 0x02 // MajorLinkerVersion
> + .byte 0x14 // MinorLinkerVersion
> + .long _end - efi_header_end // SizeOfCode
> + .long 0 // SizeOfInitializedData
> + .long 0 // SizeOfUninitializedData
> + .long __efistub_entry - _head // AddressOfEntryPoint
> + .long efi_header_end - _head // BaseOfCode
> +
> +extra_header_fields:
> + .quad 0 // ImageBase
> + .long 0x1000 // SectionAlignment
> + .long PECOFF_FILE_ALIGNMENT // FileAlignment
> + .short 0 // MajorOperatingSystemVersion
> + .short 0 // MinorOperatingSystemVersion
> + .short 0 // MajorImageVersion
> + .short 0 // MinorImageVersion
> + .short 0 // MajorSubsystemVersion
> + .short 0 // MinorSubsystemVersion
> + .long 0 // Win32VersionValue
> +
> + .long _end - _head // SizeOfImage
> +
> + // Everything before the kernel image is considered part of the header
> + .long efi_header_end - _head // SizeOfHeaders
> + .long 0 // CheckSum
> + .short 0xa // Subsystem (EFI application)
> + .short 0 // DllCharacteristics
> + .quad 0 // SizeOfStackReserve
> + .quad 0 // SizeOfStackCommit
> + .quad 0 // SizeOfHeapReserve
> + .quad 0 // SizeOfHeapCommit
> + .long 0 // LoaderFlags
> + .long (section_table - .) / 8 // NumberOfRvaAndSizes
> +
> + .quad 0 // ExportTable
> + .quad 0 // ImportTable
> + .quad 0 // ResourceTable
> + .quad 0 // ExceptionTable
> + .quad 0 // CertificationTable
> + .quad 0 // BaseRelocationTable
> +
> +#ifdef CONFIG_DEBUG_EFI
> + .long efi_debug_table - _head // DebugTable
> + .long efi_debug_table_size
> +#endif
> +
> + // Section table
> +section_table:
> +
> + /*
> + * The EFI application loader requires a relocation section
> + * because EFI applications must be relocatable. This is a
> + * dummy section as far as we are concerned.
> + */
> + .ascii ".reloc"
> + .byte 0
> + .byte 0 // end of 0 padding of section name
> + .long 0
> + .long 0
> + .long 0 // SizeOfRawData
> + .long 0 // PointerToRawData
> + .long 0 // PointerToRelocations
> + .long 0 // PointerToLineNumbers
> + .short 0 // NumberOfRelocations
> + .short 0 // NumberOfLineNumbers
> + .long 0x42100040 // Characteristics (section flags)
> +
> +
> + .ascii ".text"
> + .byte 0
> + .byte 0
> + .byte 0 // end of 0 padding of section name
> + .long _end - efi_header_end // VirtualSize
> + .long efi_header_end - _head // VirtualAddress
> + .long _edata - efi_header_end // SizeOfRawData
> + .long efi_header_end - _head // PointerToRawData
> +
> + .long 0 // PointerToRelocations
> + .long 0 // PointerToLineNumbers
> + .short 0 // NumberOfRelocations
> + .short 0 // NumberOfLineNumbers
> + .long 0xe0500020 // Characteristics
> +
> +#ifdef CONFIG_DEBUG_EFI
> + /*
> + * The debug table is referenced via its Relative Virtual Address (RVA),
> + * which is only defined for those parts of the image that are covered
> + * by a section declaration. Since this header is not covered by any
> + * section, the debug table must be emitted elsewhere. So stick it in
> + * the .init.rodata section instead.
> + *
> + * Note that the EFI debug entry itself may legally have a zero RVA,
> + * which means we can simply put it right after the section headers.
> + */
> + __INITRODATA
> +
> + .align 2
> +efi_debug_table:
> + // EFI_IMAGE_DEBUG_DIRECTORY_ENTRY
> + .long 0 // Characteristics
> + .long 0 // TimeDateStamp
> + .short 0 // MajorVersion
> + .short 0 // MinorVersion
> + .long 2 // Type == EFI_IMAGE_DEBUG_TYPE_CODEVIEW
> + .long efi_debug_entry_size // SizeOfData
> + .long 0 // RVA
> + .long efi_debug_entry - _head // FileOffset
> +
> + .set efi_debug_table_size, . - efi_debug_table
> + .previous
> +
> +efi_debug_entry:
> + // EFI_IMAGE_DEBUG_CODEVIEW_NB10_ENTRY
> + .ascii "NB10" // Signature
> + .long 0 // Unknown
> + .long 0 // Unknown2
> + .long 0 // Unknown3
> +
> + .asciz VMLINUX_PATH
> +
> + .set efi_debug_entry_size, . - efi_debug_entry
> +#endif
> +
> + /*
> + * EFI will load .text onwards at the 4k section alignment
> + * described in the PE/COFF header. To ensure that instruction
> + * sequences using an adrp and a :lo12: immediate will function
> + * correctly at this alignment, we must ensure that .text is
> + * placed at a 4k boundary in the Image to begin with.
> + */
> + .align 12
> +efi_header_end:
> +#endif
> + .endm
> diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
> index c6cc82ec190b..aca9b184035a 100644
> --- a/arch/arm64/kernel/head.S
> +++ b/arch/arm64/kernel/head.S
> @@ -42,6 +42,8 @@
> #include <asm/thread_info.h>
> #include <asm/virt.h>
>
> +#include "efi-header.S"
> +
> #define __PHYS_OFFSET (KERNEL_START - TEXT_OFFSET)
>
> #if (TEXT_OFFSET & 0xfff) != 0
> @@ -72,17 +74,7 @@ _head:
> /*
> * DO NOT MODIFY. Image header expected by Linux boot-loaders.
> */
> -#ifdef CONFIG_EFI
> - /*
> - * This add instruction has no meaningful effect except that
> - * its opcode forms the magic "MZ" signature required by UEFI.
> - */
> - add x13, x18, #0x16
> - b stext
> -#else
> - b stext // branch to kernel start, magic
> - .long 0 // reserved
> -#endif
> + __jmp stext // Executable code
> le64sym _kernel_offset_le // Image load offset from start of RAM, little-endian
> le64sym _kernel_size_le // Effective size of kernel image, little-endian
> le64sym _kernel_flags_le // Informative flags, little-endian
> @@ -93,163 +85,8 @@ _head:
> .byte 0x52
> .byte 0x4d
> .byte 0x64
> -#ifdef CONFIG_EFI
> - .long pe_header - _head // Offset to the PE header.
> -#else
> - .word 0 // reserved
> -#endif
> -
> -#ifdef CONFIG_EFI
> - .align 3
> -pe_header:
> - .ascii "PE"
> - .short 0
> -coff_header:
> - .short 0xaa64 // AArch64
> - .short 2 // nr_sections
> - .long 0 // TimeDateStamp
> - .long 0 // PointerToSymbolTable
> - .long 1 // NumberOfSymbols
> - .short section_table - optional_header // SizeOfOptionalHeader
> - .short 0x206 // Characteristics.
> - // IMAGE_FILE_DEBUG_STRIPPED |
> - // IMAGE_FILE_EXECUTABLE_IMAGE |
> - // IMAGE_FILE_LINE_NUMS_STRIPPED
> -optional_header:
> - .short 0x20b // PE32+ format
> - .byte 0x02 // MajorLinkerVersion
> - .byte 0x14 // MinorLinkerVersion
> - .long _end - efi_header_end // SizeOfCode
> - .long 0 // SizeOfInitializedData
> - .long 0 // SizeOfUninitializedData
> - .long __efistub_entry - _head // AddressOfEntryPoint
> - .long efi_header_end - _head // BaseOfCode
> -
> -extra_header_fields:
> - .quad 0 // ImageBase
> - .long 0x1000 // SectionAlignment
> - .long PECOFF_FILE_ALIGNMENT // FileAlignment
> - .short 0 // MajorOperatingSystemVersion
> - .short 0 // MinorOperatingSystemVersion
> - .short 0 // MajorImageVersion
> - .short 0 // MinorImageVersion
> - .short 0 // MajorSubsystemVersion
> - .short 0 // MinorSubsystemVersion
> - .long 0 // Win32VersionValue
> -
> - .long _end - _head // SizeOfImage
> -
> - // Everything before the kernel image is considered part of the header
> - .long efi_header_end - _head // SizeOfHeaders
> - .long 0 // CheckSum
> - .short 0xa // Subsystem (EFI application)
> - .short 0 // DllCharacteristics
> - .quad 0 // SizeOfStackReserve
> - .quad 0 // SizeOfStackCommit
> - .quad 0 // SizeOfHeapReserve
> - .quad 0 // SizeOfHeapCommit
> - .long 0 // LoaderFlags
> - .long (section_table - .) / 8 // NumberOfRvaAndSizes
> -
> - .quad 0 // ExportTable
> - .quad 0 // ImportTable
> - .quad 0 // ResourceTable
> - .quad 0 // ExceptionTable
> - .quad 0 // CertificationTable
> - .quad 0 // BaseRelocationTable
> -
> -#ifdef CONFIG_DEBUG_EFI
> - .long efi_debug_table - _head // DebugTable
> - .long efi_debug_table_size
> -#endif
> -
> - // Section table
> -section_table:
>
> - /*
> - * The EFI application loader requires a relocation section
> - * because EFI applications must be relocatable. This is a
> - * dummy section as far as we are concerned.
> - */
> - .ascii ".reloc"
> - .byte 0
> - .byte 0 // end of 0 padding of section name
> - .long 0
> - .long 0
> - .long 0 // SizeOfRawData
> - .long 0 // PointerToRawData
> - .long 0 // PointerToRelocations
> - .long 0 // PointerToLineNumbers
> - .short 0 // NumberOfRelocations
> - .short 0 // NumberOfLineNumbers
> - .long 0x42100040 // Characteristics (section flags)
> -
> -
> - .ascii ".text"
> - .byte 0
> - .byte 0
> - .byte 0 // end of 0 padding of section name
> - .long _end - efi_header_end // VirtualSize
> - .long efi_header_end - _head // VirtualAddress
> - .long _edata - efi_header_end // SizeOfRawData
> - .long efi_header_end - _head // PointerToRawData
> -
> - .long 0 // PointerToRelocations (0 for executables)
> - .long 0 // PointerToLineNumbers (0 for executables)
> - .short 0 // NumberOfRelocations (0 for executables)
> - .short 0 // NumberOfLineNumbers (0 for executables)
> - .long 0xe0500020 // Characteristics (section flags)
> -
> -#ifdef CONFIG_DEBUG_EFI
> - /*
> - * The debug table is referenced via its Relative Virtual Address (RVA),
> - * which is only defined for those parts of the image that are covered
> - * by a section declaration. Since this header is not covered by any
> - * section, the debug table must be emitted elsewhere. So stick it in
> - * the .init.rodata section instead.
> - *
> - * Note that the EFI debug entry itself may legally have a zero RVA,
> - * which means we can simply put it right after the section headers.
> - */
> - __INITRODATA
> -
> - .align 2
> -efi_debug_table:
> - // EFI_IMAGE_DEBUG_DIRECTORY_ENTRY
> - .long 0 // Characteristics
> - .long 0 // TimeDateStamp
> - .short 0 // MajorVersion
> - .short 0 // MinorVersion
> - .long 2 // Type == EFI_IMAGE_DEBUG_TYPE_CODEVIEW
> - .long efi_debug_entry_size // SizeOfData
> - .long 0 // RVA
> - .long efi_debug_entry - _head // FileOffset
> -
> - .set efi_debug_table_size, . - efi_debug_table
> - .previous
> -
> -efi_debug_entry:
> - // EFI_IMAGE_DEBUG_CODEVIEW_NB10_ENTRY
> - .ascii "NB10" // Signature
> - .long 0 // Unknown
> - .long 0 // Unknown2
> - .long 0 // Unknown3
> -
> - .asciz VMLINUX_PATH
> -
> - .set efi_debug_entry_size, . - efi_debug_entry
> -#endif
> -
> - /*
> - * EFI will load .text onwards at the 4k section alignment
> - * described in the PE/COFF header. To ensure that instruction
> - * sequences using an adrp and a :lo12: immediate will function
> - * correctly at this alignment, we must ensure that .text is
> - * placed at a 4k boundary in the Image to begin with.
> - */
> - .align 12
> -efi_header_end:
> -#endif
> + __EFI_HEADER
>
> __INIT
>
> --
> 2.7.4
>
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