On Wed, Oct 22, 2014 at 03:21:45PM +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. > > Reviewed-by: Roy Franz <[email protected]> > Signed-off-by: Ard Biesheuvel <[email protected]>
Acked-by: Mark Rutland <[email protected]> Mark. > --- > 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 [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
