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... :)

Thanks Laszlo