Hi Ard, On Fri, Oct 10, 2014 at 10:25:24AM +0100, Ard Biesheuvel wrote: > 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. Has this been observed happening, or was this just found by inspection? > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> > --- > arch/arm64/kernel/head.S | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S > index 0a6e4f924df8..5e83e5b8a9de 100644 > --- a/arch/arm64/kernel/head.S > +++ b/arch/arm64/kernel/head.S > @@ -159,7 +159,7 @@ optional_header: > > extra_header_fields: > .quad 0 // ImageBase > - .long 0x20 // SectionAlignment > + .long 0x1000 // SectionAlignment > .long 0x8 // FileAlignment > .short 0 // MajorOperatingSystemVersion > .short 0 // MinorOperatingSystemVersion > @@ -226,7 +226,7 @@ section_table: > .short 0 // NumberOfRelocations (0 for executables) > .short 0 // NumberOfLineNumbers (0 for executables) > .long 0xe0500020 // Characteristics (section flags) > - .align 5 > + .align 12 Can we get a comment explaining why stext needs the additional alignment? Something like: /* * 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 Otherwise this looks sane to me. Thanks, Mark. -- 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
