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scudo: Store header on deallocation before retagging memory. 

From a cache perspective it's better to store the header immediately
after loading it. If we delay this operation until after we've
retagged it's more likely that our header will have been evicted from
the cache and we'll need to fetch it again in order to perform the
compare-exchange operation.

For similar reasons, store the deallocation stack before retagging
instead of afterwards.

Differential Revision: https://reviews.llvm.org/D101137
This commit is contained in:
Peter Collingbourne 2021-04-22 22:41:01 -07:00
parent 89c4dda076
commit 0a5576ecf0
1 changed files with 14 additions and 12 deletions
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26
compiler-rt/lib/scudo/standalone/combined.h
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@ -1036,8 +1036,22 @@ private:
Chunk::UnpackedHeader *Header, uptr Size) {
void *Ptr = getHeaderTaggedPointer(TaggedPtr);
Chunk::UnpackedHeader NewHeader = *Header;
// If the quarantine is disabled, the actual size of a chunk is 0 or larger
// than the maximum allowed, we return a chunk directly to the backend.
// This purposefully underflows for Size == 0.
const bool BypassQuarantine = !Quarantine.getCacheSize() ||
((Size - 1) >= QuarantineMaxChunkSize) ||
!NewHeader.ClassId;
NewHeader.State =
BypassQuarantine ? Chunk::State::Available : Chunk::State::Quarantined;
NewHeader.OriginOrWasZeroed = useMemoryTagging<Params>(Options) &&
NewHeader.ClassId &&
!TSDRegistry.getDisableMemInit();
Chunk::compareExchangeHeader(Cookie, Ptr, &NewHeader, Header);
if (UNLIKELY(useMemoryTagging<Params>(Options))) {
u8 PrevTag = extractTag(reinterpret_cast<uptr>(TaggedPtr));
storeDeallocationStackMaybe(Options, Ptr, PrevTag, Size);
if (NewHeader.ClassId) {
if (!TSDRegistry.getDisableMemInit()) {
uptr TaggedBegin, TaggedEnd;
@ -1049,19 +1063,9 @@ private:
setRandomTag(Ptr, Size, OddEvenMask | (1UL << PrevTag), &TaggedBegin,
&TaggedEnd);
}
NewHeader.OriginOrWasZeroed = !TSDRegistry.getDisableMemInit();
}
storeDeallocationStackMaybe(Options, Ptr, PrevTag, Size);
}
// If the quarantine is disabled, the actual size of a chunk is 0 or larger
// than the maximum allowed, we return a chunk directly to the backend.
// This purposefully underflows for Size == 0.
const bool BypassQuarantine = !Quarantine.getCacheSize() ||
((Size - 1) >= QuarantineMaxChunkSize) ||
!NewHeader.ClassId;
if (BypassQuarantine) {
NewHeader.State = Chunk::State::Available;
Chunk::compareExchangeHeader(Cookie, Ptr, &NewHeader, Header);
if (allocatorSupportsMemoryTagging<Params>())
Ptr = untagPointer(Ptr);
void *BlockBegin = getBlockBegin(Ptr, &NewHeader);
@ -1079,8 +1083,6 @@ private:
Secondary.deallocate(Options, BlockBegin);
}
} else {
NewHeader.State = Chunk::State::Quarantined;
Chunk::compareExchangeHeader(Cookie, Ptr, &NewHeader, Header);
bool UnlockRequired;
auto *TSD = TSDRegistry.getTSDAndLock(&UnlockRequired);
Quarantine.put(&TSD->QuarantineCache,