On Feb 21, 2014, at 10:17 AM, Laszlo Ersek <lersek@redhat.com> wrote:

On 02/21/14 16:12, Ryan Harkin wrote:

Hi Olivier,

I've just noticed that the upstream EDK2 repository for the FVP AEMv8
model is broken when built with Linaro GCC 13.12 onwards.

The error I see is:

UEFI firmware (version  built at 14:54:24 on Feb 21 2014)
add-symbol-file
/linaro/uefi/master/upstream/edk2.git/Build/ArmVExpress-FVP-AArch64/DEBUG_ARMGCC/AARCH64/ArmPlatformPkg/PrePi/PeiMPCore/DEBUG/ArmPlatformPrePiMPCore.dll
0x88000780
Decompress Failed - Not Found

ASSERT_EFI_ERROR (Status = Not Found)
ASSERT /linaro/uefi/master/upstream/edk2.git/ArmPlatformPkg/PrePi/PrePi.c(194):
!EFI_ERROR (Status)

I've tracked the bug as far as function "FfsProcessSection" [1] where
at line 373, it calls into function "ExtractGuidedSectionDecode" [2]
which then calls into "SavedData->ExtractDecodeHandlerTable [Index]".
At that point, I can't work out where it goes.

I can "fix" the problem if I re-org the variables at the top of
FfsProcessSection so that DstBuffer is at the start of the
declarations.  That is obviously not a fix.  But it will probably hint
at why the subsequent code is broken.

Cheers,
Ryan

[1] EmbeddedPkg/Library/PrePiLib/FwVol.c, line 285
[2] EmbeddedPkg/Library/PrePiExtractGuidedSectionLib/PrePiExtractGuidedSectionLib.c:166

Here's a random shot (could be completely unrelated):


EFI_STATUS
FfsProcessSection (
 IN EFI_SECTION_TYPE           SectionType,
 IN EFI_COMMON_SECTION_HEADER  *Section,
 IN UINTN                      SectionSize,
 OUT VOID                      **OutputBuffer
 )
{
 /* ... */
 UINTN                                   DstBufferSize;
 /* ... */

You're on AArch64, so UINTN means UINT64.

Note that this "auto" variable is not initialized, hence its contents are indeterminate. Fast forward to the next use:

       Status = UefiDecompressGetInfo (
                  (UINT8 *) ((EFI_COMPRESSION_SECTION *) Section + 1),
                  (UINT32) SectionLength - sizeof (EFI_COMPRESSION_SECTION),
                  (UINT32 *) &DstBufferSize,
                  &ScratchBufferSize
                  );
     } else if (Section->Type == EFI_SECTION_GUID_DEFINED) {
       Status = ExtractGuidedSectionGetInfo (
                  Section,
                  (UINT32 *) &DstBufferSize,
                  &ScratchBufferSize,
                  &SectionAttribute
                  );

Whichever of these functions is invoked, it fills in only four bytes (UINT32). Then,

     DstBuffer = (VOID *)(UINTN)AllocatePages (EFI_SIZE_TO_PAGES (DstBufferSize) + 1);

etc etc etc.

By reordering the local variables, you could be limiting the nonzero garbage in "DstBufferSize" to those four bytes that *are* ultimately overwritten.

I guess initing DstBufferSize to zero is easy enough to try... :)

Why not just make it UINT32 and remove the casts. A real fix!

Thanks,

Andrew Fish

Thanks
Laszlo

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