Date: Wed, 8 Feb 2017 11:55:39 +0000 From: Ard Biesheuvel <ard.biesheuvel@...aro.org> To: linux-efi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, mark.rutland@....com, leif.lindholm@...aro.org Cc: catalin.marinas@....com, linux@...linux.org.uk, kernel-hardening@...ts.openwall.com, labbott@...oraproject.org, Ard Biesheuvel <ard.biesheuvel@...aro.org> Subject: [PATCH v2 06/14] arm64: efi: remove pointless dummy .reloc section The kernel's EFI PE/COFF header contains a dummy .reloc section, and an explanatory comment that claims that this is required for the EFI application loader to accept the Image as a relocatable image (i.e., one that can be loaded at any offset and fixed up in place) This was inherited from the x86 implementation, which has elaborate host tooling to mangle the PE/COFF header post-link time, and which populates the .reloc section with a single dummy base relocation. On ARM, no such tooling exists, and the .reloc section remains empty, and is never even exposed via the BaseRelocationTable directory entry, which is where the PE/COFF loader looks for it. The PE/COFF spec is unclear about relocatable images that do not require any fixups, but the EDK2 implementation, which is the de facto reference for PE/COFF in the UEFI space, clearly does not care, and explicitly mentions (in a comment) that relocatable images with no base relocations are perfectly fine, as long as they don't have the RELOCS_STRIPPED attribute set (which is not the case for our PE/COFF image) So simply remove the .reloc section altogether. Acked-by: Mark Rutland <mark.rutland@....com> Acked-by: Peter Jones <pjones@...hat.com> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org> --- arch/arm64/kernel/efi-header.S | 22 +------------------- 1 file changed, 1 insertion(+), 21 deletions(-) diff --git a/arch/arm64/kernel/efi-header.S b/arch/arm64/kernel/efi-header.S index 515624bbfcd0..8786d58af2df 100644 --- a/arch/arm64/kernel/efi-header.S +++ b/arch/arm64/kernel/efi-header.S @@ -12,7 +12,7 @@ .short 0 coff_header: .short 0xaa64 // AArch64 - .short 2 // nr_sections + .short 1 // nr_sections .long 0 // TimeDateStamp .long 0 // PointerToSymbolTable .long 0 // NumberOfSymbols @@ -71,26 +71,6 @@ extra_header_fields: // 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 0x42000040 // Characteristics (section flags) - - .ascii ".text" .byte 0 .byte 0 -- 2.7.4
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