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Message-ID: <20170206171312.GG4190@leverpostej>
Date: Mon, 6 Feb 2017 17:13:12 +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 6/7] arm64: efi: replace open coded constants with
symbolic ones
On Mon, Feb 06, 2017 at 04:24:34PM +0000, Ard Biesheuvel wrote:
> Replace open coded constants with symbolic ones throughout the
> Image and the EFI headers. Note that in two cases, this removes
> a value that the PE/COFF spec does not allow:
> - NumberOfSymbols in the PE header should be 0
> - PE/COFF executable sections (as opposed to sections in object files)
> should not use the section alignment flags
I take it that EDK2 doesn't care about either of these, but perhaps we
should fix those in a preparatory patch, at the start of the series, to
separate fixes from rework.
That also makes it easier to binary-diff an Image after this patch, to
ensure that the mnemonicisation is correct. ;)
Otherwise, this generally looks fine.
Thanks,
Mark.
>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> ---
> arch/arm64/kernel/efi-header.S | 37 ++++++++++----------
> arch/arm64/kernel/head.S | 5 +--
> 2 files changed, 20 insertions(+), 22 deletions(-)
>
> diff --git a/arch/arm64/kernel/efi-header.S b/arch/arm64/kernel/efi-header.S
> index 35b11654ecc5..c87c23336c86 100644
> --- a/arch/arm64/kernel/efi-header.S
> +++ b/arch/arm64/kernel/efi-header.S
> @@ -7,6 +7,8 @@
> * published by the Free Software Foundation.
> */
>
> +#include <linux/pe.h>
> +
> .macro __jmp, target
> #ifdef CONFIG_EFI
> /*
> @@ -33,21 +35,20 @@
> .long pe_header - _head // Offset to the PE header.
>
> pe_header:
> - .ascii "PE"
> - .short 0
> + .long PE_MAGIC
> coff_header:
> - .short 0xaa64 // AArch64
> - .short 1 // nr_sections
> + .short IMAGE_FILE_MACHINE_ARM64 // Machine
> + .short 1 // NumberOfSections
> .long 0 // TimeDateStamp
> .long 0 // PointerToSymbolTable
> - .long 1 // NumberOfSymbols
> + .long 0 // NumberOfSymbols
> .short section_table - optional_header // SizeOfOptionalHeader
> - .short 0x206 // Characteristics.
> - // IMAGE_FILE_DEBUG_STRIPPED |
> - // IMAGE_FILE_EXECUTABLE_IMAGE |
> - // IMAGE_FILE_LINE_NUMS_STRIPPED
> + .short IMAGE_FILE_DEBUG_STRIPPED | \
> + IMAGE_FILE_EXECUTABLE_IMAGE | \
> + IMAGE_FILE_LINE_NUMS_STRIPPED // Characteristics
> +
> optional_header:
> - .short 0x20b // PE32+ format
> + .short PE_OPT_MAGIC_PE32PLUS // PE32+ format
> .byte 0x02 // MajorLinkerVersion
> .byte 0x14 // MinorLinkerVersion
> .long _end - efi_header_end // SizeOfCode
> @@ -58,7 +59,7 @@ optional_header:
>
> extra_header_fields:
> .quad 0 // ImageBase
> - .long 0x1000 // SectionAlignment
> + .long SZ_4K // SectionAlignment
> .long PECOFF_FILE_ALIGNMENT // FileAlignment
> .short 0 // MajorOperatingSystemVersion
> .short 0 // MinorOperatingSystemVersion
> @@ -73,7 +74,7 @@ extra_header_fields:
> // 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 IMAGE_SUBSYSTEM_EFI_APPLICATION // Subsystem
> .short 0 // DllCharacteristics
> .quad 0 // SizeOfStackReserve
> .quad 0 // SizeOfStackCommit
> @@ -96,10 +97,7 @@ extra_header_fields:
>
> // Section table
> section_table:
> - .ascii ".text"
> - .byte 0
> - .byte 0
> - .byte 0 // end of 0 padding of section name
> + .ascii ".text\0\0\0"
> .long _end - efi_header_end // VirtualSize
> .long efi_header_end - _head // VirtualAddress
> .long _edata - efi_header_end // SizeOfRawData
> @@ -109,7 +107,10 @@ section_table:
> .long 0 // PointerToLineNumbers
> .short 0 // NumberOfRelocations
> .short 0 // NumberOfLineNumbers
> - .long 0xe0500020 // Characteristics
> + .long IMAGE_SCN_CNT_CODE | \
> + IMAGE_SCN_MEM_EXECUTE | \
> + IMAGE_SCN_MEM_READ | \
> + IMAGE_SCN_MEM_WRITE // Characteristics
>
> #ifdef CONFIG_DEBUG_EFI
> /*
> @@ -131,7 +132,7 @@ efi_debug_table:
> .long 0 // TimeDateStamp
> .short 0 // MajorVersion
> .short 0 // MinorVersion
> - .long 2 // Type == EFI_IMAGE_DEBUG_TYPE_CODEVIEW
> + .long IMAGE_DEBUG_TYPE_CODEVIEW // Type
> .long efi_debug_entry_size // SizeOfData
> .long 0 // RVA
> .long efi_debug_entry - _head // FileOffset
> diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
> index aca9b184035a..055735ba3600 100644
> --- a/arch/arm64/kernel/head.S
> +++ b/arch/arm64/kernel/head.S
> @@ -81,10 +81,7 @@ _head:
> .quad 0 // reserved
> .quad 0 // reserved
> .quad 0 // reserved
> - .byte 0x41 // Magic number, "ARM\x64"
> - .byte 0x52
> - .byte 0x4d
> - .byte 0x64
> + .ascii "ARM\x64" // Magic number
>
> __EFI_HEADER
>
> --
> 2.7.4
>
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