| Message ID | 1486398275-3966-6-git-send-email-ard.biesheuvel@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, Feb 06, 2017 at 04:24:33PM +0000, Ard Biesheuvel wrote: > 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. > > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> I don't have anything against this patch, so FWIW: Acked-by: Mark Rutland <mark.rutland@arm.com> Thanks, Mark. > --- > 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 74a25c09a1b8..35b11654ecc5 100644 > --- a/arch/arm64/kernel/efi-header.S > +++ b/arch/arm64/kernel/efi-header.S > @@ -37,7 +37,7 @@ pe_header: > .short 0 > coff_header: > .short 0xaa64 // AArch64 > - .short 2 // nr_sections > + .short 1 // nr_sections > .long 0 // TimeDateStamp > .long 0 // PointerToSymbolTable > .long 1 // NumberOfSymbols > @@ -96,26 +96,6 @@ 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 0x42100040 // Characteristics (section flags) > - > - > .ascii ".text" > .byte 0 > .byte 0 > -- > 2.7.4 >
On Mon, Feb 06, 2017 at 04:24:33PM +0000, Ard Biesheuvel wrote: > 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. > > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Looks completely reasonable to me. Acked-by: Peter Jones <pjones@redhat.com> > --- > 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 74a25c09a1b8..35b11654ecc5 100644 > --- a/arch/arm64/kernel/efi-header.S > +++ b/arch/arm64/kernel/efi-header.S > @@ -37,7 +37,7 @@ pe_header: > .short 0 > coff_header: > .short 0xaa64 // AArch64 > - .short 2 // nr_sections > + .short 1 // nr_sections > .long 0 // TimeDateStamp > .long 0 // PointerToSymbolTable > .long 1 // NumberOfSymbols > @@ -96,26 +96,6 @@ 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 0x42100040 // Characteristics (section flags) > - > - > .ascii ".text" > .byte 0 > .byte 0 > -- > 2.7.4 >
diff --git a/arch/arm64/kernel/efi-header.S b/arch/arm64/kernel/efi-header.S index 74a25c09a1b8..35b11654ecc5 100644 --- a/arch/arm64/kernel/efi-header.S +++ b/arch/arm64/kernel/efi-header.S @@ -37,7 +37,7 @@ pe_header: .short 0 coff_header: .short 0xaa64 // AArch64 - .short 2 // nr_sections + .short 1 // nr_sections .long 0 // TimeDateStamp .long 0 // PointerToSymbolTable .long 1 // NumberOfSymbols @@ -96,26 +96,6 @@ 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 0x42100040 // Characteristics (section flags) - - .ascii ".text" .byte 0 .byte 0
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. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> --- arch/arm64/kernel/efi-header.S | 22 +------------------- 1 file changed, 1 insertion(+), 21 deletions(-)