Hi Ard, On Tue, Jul 15, 2014 at 10:10:02AM +0100, Ard Biesheuvel wrote: > After the EFI stub has done its business, it jumps into the kernel by > branching > to offset #0 of the loaded Image, which is where it expects to find the header > containing a 'branch to stext' instruction. > However, the header is not covered by any PE/COFF section, so the header may > not actually be loaded at the expected offset. So instead, jump to 'stext' > directly, which is at the base of the PE/COFF .text section.
It would be nice to point out in the commit message that the other changes in the patch are just cleanup to use stext_offset rather than open-coding it. > Signed-off-by: Ard Biesheuvel <[email protected]> > --- > arch/arm64/kernel/efi-entry.S | 2 +- > arch/arm64/kernel/head.S | 10 ++++++---- > 2 files changed, 7 insertions(+), 5 deletions(-) > > diff --git a/arch/arm64/kernel/efi-entry.S b/arch/arm64/kernel/efi-entry.S > index 619b1dd7bcde..6ef541731d9e 100644 > --- a/arch/arm64/kernel/efi-entry.S > +++ b/arch/arm64/kernel/efi-entry.S > @@ -61,7 +61,7 @@ ENTRY(efi_stub_entry) > */ > mov x20, x0 // DTB address > ldr x0, [sp, #16] // relocated _text address > - mov x21, x0 > + add x21, x0, #:lo12:stext_offset I think we can drop the :lo12: here, which will allow us to have a warning if stext_offset is unexpectedly large (I believe this will currently silently mask bits were that to happen?). Other than that, this looks like a sensible thing to do given that we cannot rely on the header being present. Cheers, Mark. > > /* > * Flush dcache covering current runtime addresses > diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S > index a2c1195abb7f..78ddae28b090 100644 > --- a/arch/arm64/kernel/head.S > +++ b/arch/arm64/kernel/head.S > @@ -137,6 +137,8 @@ efi_head: > #endif > > #ifdef CONFIG_EFI > + .globl stext_offset > + .set stext_offset, stext - efi_head > .align 3 > pe_header: > .ascii "PE" > @@ -160,7 +162,7 @@ optional_header: > .long 0 // SizeOfInitializedData > .long 0 // SizeOfUninitializedData > .long efi_stub_entry - efi_head // AddressOfEntryPoint > - .long stext - efi_head // BaseOfCode > + .long stext_offset // BaseOfCode > > extra_header_fields: > .quad 0 // ImageBase > @@ -177,7 +179,7 @@ extra_header_fields: > .long _edata - efi_head // SizeOfImage > > // Everything before the kernel image is considered part of the header > - .long stext - efi_head // SizeOfHeaders > + .long stext_offset // SizeOfHeaders > .long 0 // CheckSum > .short 0xa // Subsystem (EFI application) > .short 0 // DllCharacteristics > @@ -222,9 +224,9 @@ section_table: > .byte 0 > .byte 0 // end of 0 padding of section name > .long _edata - stext // VirtualSize > - .long stext - efi_head // VirtualAddress > + .long stext_offset // VirtualAddress > .long _edata - stext // SizeOfRawData > - .long stext - efi_head // PointerToRawData > + .long stext_offset // PointerToRawData > > .long 0 // PointerToRelocations (0 for executables) > .long 0 // PointerToLineNumbers (0 for executables) > -- > 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
