Position independent AArch64 code needs to be linked and loaded at the same relative offset from a 4 KB boundary, or adrp/add and adrp/ldr pairs will not work correctly. (This is how PC relative symbol references with a 4 GB reach are emitted) We need to declare this in the PE/COFF header, otherwise the PE/COFF loader may load the Image and invoke the stub at an offset which violates this rule. Reviewed-by: Roy Franz <roy.franz@xxxxxxxxxx> Acked-by: Mark Rutland <mark.rutland@xxxxxxx> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> --- v2: added comment explaining '.align 12' in head.S --- arch/arm64/kernel/head.S | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index 8c06c9d269d2..8ae84d8c2a8c 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -161,7 +161,7 @@ optional_header: extra_header_fields: .quad 0 // ImageBase - .long 0x20 // SectionAlignment + .long 0x1000 // SectionAlignment .long 0x8 // FileAlignment .short 0 // MajorOperatingSystemVersion .short 0 // MinorOperatingSystemVersion @@ -228,7 +228,15 @@ section_table: .short 0 // NumberOfRelocations (0 for executables) .short 0 // NumberOfLineNumbers (0 for executables) .long 0xe0500020 // Characteristics (section flags) - .align 5 + + /* + * EFI will load stext 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 stext is + * placed at a 4k boundary in the Image to begin with. + */ + .align 12 #endif ENTRY(stext) -- 1.8.3.2 -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
