From: Ard Biesheuvel <ardb@xxxxxxxxxx> The .compat section is a dummy PE section that contains the address of the 32-bit entrypoint of the 64-bit kernel image if it is bootable from 32-bit firmware (i.e., CONFIG_EFI_MIXED=y) This section is only 8 bytes in size and is only referenced from the loader, and so it is placed at the end of the memory view of the image, to avoid the need for padding it to 4k, which is required for sections appearing in the middle of the image. Unfortunately, this violates the PE/COFF spec, and even if most EFI loaders will work correctly (including the Tianocore reference implementation), PE loaders do exist that reject such images, on the basis that both the file and memory views of the file contents should be described by the section headers in a manner that is monotonic and does not leave any gaps. So reorganize the sections to avoid this issue. This results in a slight padding overhead (< 4k) but this can be avoided by disabling CONFIG_EFI_MIXED (which is only needed in rare cases these days) Reported-by: Mike Beaton <mjsbeaton@xxxxxxxxx> Link: https://lkml.kernel.org/r/CAHzAAWQ6srV6LVNdmfbJhOwhBw5ZzxxZZ07aHt9oKkfYAdvuQQ%40mail.gmail.com Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx> --- arch/x86/boot/header.S | 13 +++++-------- arch/x86/boot/setup.ld | 6 +++--- 2 files changed, 8 insertions(+), 11 deletions(-) diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S index b2771710ed98..8c093a2b18eb 100644 --- a/arch/x86/boot/header.S +++ b/arch/x86/boot/header.S @@ -106,8 +106,7 @@ extra_header_fields: .word 0 # MinorSubsystemVersion .long 0 # Win32VersionValue - .long setup_size + ZO__end + pecompat_vsize - # SizeOfImage + .long setup_size + ZO__end # SizeOfImage .long salign # SizeOfHeaders .long 0 # CheckSum @@ -143,7 +142,7 @@ section_table: .ascii ".setup" .byte 0 .byte 0 - .long setup_size - salign # VirtualSize + .long pecompat_fstart - salign # VirtualSize .long salign # VirtualAddress .long pecompat_fstart - salign # SizeOfRawData .long salign # PointerToRawData @@ -156,8 +155,8 @@ section_table: #ifdef CONFIG_EFI_MIXED .asciz ".compat" - .long 8 # VirtualSize - .long setup_size + ZO__end # VirtualAddress + .long pecompat_fsize # VirtualSize + .long pecompat_fstart # VirtualAddress .long pecompat_fsize # SizeOfRawData .long pecompat_fstart # PointerToRawData @@ -172,8 +171,7 @@ section_table: * modes this image supports. */ .pushsection ".pecompat", "a", @progbits - .balign falign - .set pecompat_vsize, salign + .balign salign .globl pecompat_fstart pecompat_fstart: .byte 0x1 # Version @@ -182,7 +180,6 @@ pecompat_fstart: .long setup_size + ZO_efi32_pe_entry # Entrypoint .popsection #else - .set pecompat_vsize, 0 .set pecompat_fstart, setup_size #endif .ascii ".text" diff --git a/arch/x86/boot/setup.ld b/arch/x86/boot/setup.ld index 83bb7efad8ae..3a2d1360abb0 100644 --- a/arch/x86/boot/setup.ld +++ b/arch/x86/boot/setup.ld @@ -24,6 +24,9 @@ SECTIONS .text : { *(.text .text.*) } .text32 : { *(.text32) } + .pecompat : { *(.pecompat) } + PROVIDE(pecompat_fsize = setup_size - pecompat_fstart); + . = ALIGN(16); .rodata : { *(.rodata*) } @@ -36,9 +39,6 @@ SECTIONS . = ALIGN(16); .data : { *(.data*) } - .pecompat : { *(.pecompat) } - PROVIDE(pecompat_fsize = setup_size - pecompat_fstart); - .signature : { setup_sig = .; LONG(0x5a5aaa55) -- 2.43.0.594.gd9cf4e227d-goog
