On Tue, 18 Dec 2018 at 00:20, Heinrich Schuchardt <[email protected]> wrote: > > On 12/17/18 11:42 PM, Ard Biesheuvel wrote: > > On Mon, 17 Dec 2018 at 23:33, Heinrich Schuchardt <[email protected]> > > wrote: > >> > >> On 12/17/18 7:16 PM, tip-bot for Heinrich Schuchardt wrote: > >>> Commit-ID: 793423cf07e51e3185b8680167115813589c057d > >>> Gitweb: > >>> https://git.kernel.org/tip/793423cf07e51e3185b8680167115813589c057d > >>> Author: Heinrich Schuchardt <[email protected]> > >>> AuthorDate: Mon, 17 Dec 2018 19:02:14 +0100 > >>> Committer: Ingo Molnar <[email protected]> > >>> CommitDate: Mon, 17 Dec 2018 19:12:48 +0100 > >>> > >>> efi: Align 'efi_guid_t' to 64 bits > >>> > >>> The UEFI Specification Version 2.7 Errata A defines: > >>> > >>> "EFI_GUID > >>> 128-bit buffer containing a unique identifier value. > >>> Unless otherwise specified, aligned on a 64-bit boundary." > >>> > >>> Before this patch efi_guid_t was only 8-bit aligned. > >>> > >>> Note that this could potentially trigger alignment faults during > >>> EFI runtime services calls on 32-bit ARM, given that it does not > >>> permit load/store double or load/store multiple instructions to > >>> operate on memory addresses that are not 32-bit aligned. > >>> > >>> Signed-off-by: Heinrich Schuchardt <[email protected]> > >>> Signed-off-by: Ard Biesheuvel <[email protected]> > >>> Cc: <[email protected]> # v4.9+, or earlier if possible > >>> Cc: Andy Lutomirski <[email protected]> > >>> Cc: Borislav Petkov <[email protected]> > >>> Cc: Dave Hansen <[email protected]> > >>> Cc: H. Peter Anvin <[email protected]> > >>> Cc: Linus Torvalds <[email protected]> > >>> Cc: Peter Zijlstra <[email protected]> > >>> Cc: Qian Cai <[email protected]> > >>> Cc: Rik van Riel <[email protected]> > >>> Cc: Thomas Gleixner <[email protected]> > >>> Cc: [email protected] > >>> Link: > >>> http://lkml.kernel.org/r/[email protected] > >>> Signed-off-by: Ingo Molnar <[email protected]> > >>> --- > >>> include/linux/efi.h | 2 +- > >>> 1 file changed, 1 insertion(+), 1 deletion(-) > >>> > >>> diff --git a/include/linux/efi.h b/include/linux/efi.h > >>> index 100ce4a4aff6..e6480c805932 100644 > >>> --- a/include/linux/efi.h > >>> +++ b/include/linux/efi.h > >>> @@ -48,7 +48,7 @@ typedef u16 efi_char16_t; /* UNICODE > >>> character */ > >>> typedef u64 efi_physical_addr_t; > >>> typedef void *efi_handle_t; > >>> > >>> -typedef guid_t efi_guid_t; > >>> + > >>> > >>> #define EFI_GUID(a,b,c,d0,d1,d2,d3,d4,d5,d6,d7) \ > >>> GUID_INIT(a, b, c, d0, d1, d2, d3, d4, d5, d6, d7) > >>> > >> > >> Before rushing this patch in, we should carefully review its side > >> effects, e.g. on 32bit system this changes the size of > >> efi_config_table_32_t from 20 to 24, which is part of the interface to > >> the UEFI firmware. > >> > > > > grmbl. > > > > Thanks for spotting that. > > > > The UEFI spec defines a GUID struct as { UINT32; UINT16; UINT16; > > UINT8[8]; } so its natural alignment is 32 bits not 64 bits. The > > alignment issue on ARM would be solved by using __aligned(4) rather > > than __aligned(8), while not affecting the size of the config table > > struct (and potentially others) on 32-bit architectures. > > > > Ingo, apologies for the breakage. Do you prefer a replacement patch or > > a followup patch? > > > > The UEFI spec explicitly requires EFI_GUID to be 64-bit aligned. On the > other hand neither EDK2 nor GRUB not U-Boot cared about this requirement > up to now. So the array of efi_config_table_32_t had 20 byte long > members at least on Linux, EDK2, GRUB, U-Boot, and possibly on other > UEFI implementations though the UEFI spec does not mention packing here. > > As the 4.20 kernel release is imminent, please, keep this patch out > before causing breakage. >
Ingo, Let's just drop Heinrich's patch for now, and I will come back to it for the next release. There is very little EFI on 32-bit ARM in the field, and this patch in its current form will break IA-32 as well, so a quick followup fix is probably not the best approach here.
