[PATCH v2] efi: use 32-bit alignment for efi_guid_t

[Masahisa Kojima]

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>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt at canonical.com>
---
Changes in v2:
- add source code comment to describe why the efi_guid_t structure is
  4-byte aligned

 include/efi.h | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/include/efi.h b/include/efi.h
index 42f4e58a91..c3087d3da2 100644
--- a/include/efi.h
+++ b/include/efi.h
@@ -54,9 +54,18 @@
 
 struct efi_device_path;
 
+/*
+ * 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.
+ */
 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