[PATCH] efi: use 32-bit alignment for efi_guid_t

[Masahisa Kojima]

Hi Ilias,

On Fri, 27 Jan 2023 at 23:18, Ilias Apalodimas
<ilias.apalodimas at linaro.org> wrote:
>
> Hi Kojima-san
>
> On Fri, Jan 27, 2023 at 08:51:28PM +0900, Masahisa Kojima wrote:
> > Current U-Boot implements 64-bit boundary for efi_guid_t structure.
> > It follows the UEFI specification, page 21 of the UEFI Specification v2.10
> > says about EFI_GUID:
> >   128-bit buffer containing a unique identifier value. Unless
> >   otherwise specified, aligned on a 64-bit boundary.
> >
> > On the other hand, page 163 of the UEFI specification v2.10 and
> > EDK2 reference implementation both define EFI_GUID as
> > struct { u32 a; u16; b; u16 c; u8 d[8]; }; and so the implied
> > alignment is 32-bit not 64-bit like U-Boot efi_guid_t.
> >
> > Due to this alignment difference, EDK2 application "CapsuleApp.efi -P"
> > does not work as expected.
> > This calls EFI_FIRMWARE_MANAGEMENT_PROTOCOL.GetImageInfo()
> > and dump the EFI_FIRMWARE_IMAGE_DESCRIPTOR structure,
> > offsetof(EFI_FIRMWARE_IMAGE_DESCRIPTOR, ImageTypeId) is different,
> > 8 in U-Boot and 4 in EDK2(CapsuleApp.efi).
> > Here is the wrong EFI_GUID dump.
> >   wrong dump : ImageTypeId - 00000000-7D83-058B-D550-474CA19560D8
> >   expected   : ImageTypeId - 058B7D83-50D5-4C47-A195-60D86AD341C4
> >
> > EFI_FIRMWARE_IMAGE_DESCRIPTOR structure is defined in UEFI specification:
> >   typedef struct {
> >           UINT8 ImageIndex;
> >           EFI_GUID ImageTypeId;
> >           UINT64 ImageId
> >           <snip>
> >
> >   } EFI_FIRMWARE_IMAGE_DESCRIPTOR;
> >
> > There was the relevant patch for linux kernel to use 32-bit alignment
> > for efi_guid_t [1].
> > U-Boot should get aligned to EDK2 reference implementation and
> > linux kernel.
> >
> > Due to this alignment change, efi_hii_ref structure in include/efi_api.h
> > is affected, but it is not used in the current U-Boot code.
> >
> > [1] https://lore.kernel.org/all/20190202094119.13230-5-ard.biesheuvel@linaro.org/
> >
> > Cc: Ilias Apalodimas <ilias.apalodimas at linaro.org>
> > Signed-off-by: Masahisa Kojima <masahisa.kojima at linaro.org>
> > ---
> >  include/efi.h | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/include/efi.h b/include/efi.h
> > index 42f4e58a91..914a12967f 100644
> > --- a/include/efi.h
> > +++ b/include/efi.h
> > @@ -56,7 +56,7 @@ struct efi_device_path;
> >
>
> Thanks for fixing this.
> Can you add a comment similar to the commit log here as well?
>
> /* The EFI spec defines the EFI_GUID as
>  * "128-bit buffer containing a unique identifier value. Unless otherwise specified,
>  * aligned on a 64-bit boundary".
>  * Page 163 of the UEFI specification v2.10 and
>  * EDK2 reference implementation both define EFI_GUID as
>  * struct { u32 a; u16; b; u16 c; u8 d[8]; }; which is 4-byte
>  * aligned.
>  */

Yes, comments should be added. I will send an updated version.

Thanks,
Masahisa Kojima

> >  typedef struct {
> >       u8 b[16];
> > -} efi_guid_t __attribute__((aligned(8)));
> > +} efi_guid_t __attribute__((aligned(4)));
> >
> >  #define EFI_BITS_PER_LONG    (sizeof(long) * 8)
> >
> > --
> > 2.17.1
> >
>
> Thanks
> /Ilias