[PATCH] D107495: [hwasan] barrier after tagging and before tag check.

[Florian Mayer via Phabricator via llvm-commits]

fmayer created this revision.
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this makes sure that the memory accesses and the tagging are not reordered,
which happens in practice when building android.

without this change, building android with use-after-scope makes it
crashloop, with this it works.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D107495

Files:
  llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp


Index: llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
===================================================================
--- llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
+++ llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
@@ -985,6 +985,7 @@
     return false; // FIXME
 
   IRBuilder<> IRB(O.getInsn());
+  IRB.CreateFence(AtomicOrdering::Acquire, SyncScope::SingleThread);
   if (isPowerOf2_64(O.TypeSize) &&
       (O.TypeSize / 8 <= (1ULL << (kNumberOfAccessSizes - 1))) &&
       (!O.Alignment || *O.Alignment >= (1ULL << Mapping.Scale) ||
@@ -1048,6 +1049,7 @@
                                    Int8Ty, IRB.CreateBitCast(AI, Int8PtrTy),
                                    AlignedSize - 1));
     }
+    IRB.CreateFence(AtomicOrdering::Release, SyncScope::SingleThread);
   }
 }
 


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