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scudo: Obtain tag from pointer instead of loading it from memory. NFCI. 

Since we already have a tagged pointer available to us, we can just
extract the tag from it and avoid an LDG instruction.

Differential Revision: https://reviews.llvm.org/D101014
This commit is contained in:
Peter Collingbourne 2021-04-21 19:13:36 -07:00
parent 26f138eed4
commit e4fa0b307f
1 changed files with 6 additions and 5 deletions
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11
compiler-rt/lib/scudo/standalone/combined.h
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@ -518,6 +518,7 @@ public:
if (UNLIKELY(!isAligned(reinterpret_cast<uptr>(Ptr), MinAlignment)))
reportMisalignedPointer(AllocatorAction::Deallocating, Ptr);
void *TaggedPtr = Ptr;
Ptr = getHeaderTaggedPointer(Ptr);
Chunk::UnpackedHeader Header;
@ -543,7 +544,7 @@ public:
reportDeleteSizeMismatch(Ptr, DeleteSize, Size);
}
quarantineOrDeallocateChunk(Options, Ptr, &Header, Size);
quarantineOrDeallocateChunk(Options, TaggedPtr, &Header, Size);
}
void *reallocate(void *OldPtr, uptr NewSize, uptr Alignment = MinAlignment) {
@ -639,7 +640,7 @@ public:
void *NewPtr = allocate(NewSize, Chunk::Origin::Malloc, Alignment);
if (LIKELY(NewPtr)) {
memcpy(NewPtr, OldTaggedPtr, Min(NewSize, OldSize));
quarantineOrDeallocateChunk(Options, OldPtr, &OldHeader, OldSize);
quarantineOrDeallocateChunk(Options, OldTaggedPtr, &OldHeader, OldSize);
}
return NewPtr;
}
@ -1031,13 +1032,13 @@ private:
reinterpret_cast<uptr>(Ptr) - SizeOrUnusedBytes;
}
void quarantineOrDeallocateChunk(Options Options, void *Ptr,
void quarantineOrDeallocateChunk(Options Options, void *TaggedPtr,
Chunk::UnpackedHeader *Header, uptr Size) {
void *Ptr = getHeaderTaggedPointer(TaggedPtr);
Chunk::UnpackedHeader NewHeader = *Header;
if (UNLIKELY(useMemoryTagging<Params>(Options))) {
u8 PrevTag = 0;
u8 PrevTag = extractTag(reinterpret_cast<uptr>(TaggedPtr));
if (NewHeader.ClassId) {
PrevTag = extractTag(loadTag(reinterpret_cast<uptr>(Ptr)));
if (!TSDRegistry.getDisableMemInit()) {
uptr TaggedBegin, TaggedEnd;
const uptr OddEvenMask = computeOddEvenMaskForPointerMaybe(