On 01/07/19 15:09, Leif Lindholm wrote:
> Apologies for late reply, back from holidays today.
>
I'm going to snip a whole lot of context below, since I have no idea
what project this is about, and/or what files in that project (no diff
hunk headers in the context). Judged from the address list, is this
about u-boot perhaps? And adding type definitions to u-boot so they
conform to the UEFI spec, and (assuming this "and" is possible) match
edk2 practice?
> My understanding is this:
> - The EDK2 implementation does not conform to the specification; it
> completely packs the EFI_HII_KEYBOARD_LAYOUT, which the
> specification does not mention anything about. Since this code is
> well in the wild, and drivers tested against the current layout need
> to continuw eorking, I expect the only possible solution is to
> update the specification to say EFI_HII_KEYBOARD_LAYOUT must be
> packed.
I'm going to take a pass on this. :)
> - The default EDK2 definition of GUID (and hence EFI_GUID) gives it a
> 32-bit alignment requirement also on 64-bit architectures. In
> practice, I expect this would only affect (some of the) GUIDs that
> are members of structs used in UEFI interfaces. But that may already
> be too common an occurrence to audit and address in EDK2. Does the
> spec need to change on this also?
The UEFI spec (v2.7) explicitly requires EFI_GUID to be 64-bit aligned,
unless specified otherwise. See in "Table 5. Common UEFI Data Types":
EFI_GUID -- 128-bit buffer containing a unique identifier value.
Unless otherwise specified, aligned on a 64-bit boundary.
Whether edk2 satisfies that, and if so, how (by chance / by general
build flags), I don't know. The code says,
///
/// 128 bit buffer containing a unique identifier value.
/// Unless otherwise specified, aligned on a 64 bit boundary.
///
typedef struct {
UINT32 Data1;
UINT16 Data2;
UINT16 Data3;
UINT8 Data4[8];
} GUID;
I think there may have been an expectation in "MdePkg/Include/Base.h"
that the supported compilers would automatically ensure the specified
alignment, given the structure definition.
Thanks
Laszlo
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