[PATCH] D85947: [DFSan] Don't unmap during dfsan_flush().

[Matt Morehouse via Phabricator via llvm-commits]

morehouse updated this revision to Diff 285528.
morehouse added a comment.

- Add note about use in multithreaded environment.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D85947/new/

https://reviews.llvm.org/D85947

Files:
  compiler-rt/include/sanitizer/dfsan_interface.h
  compiler-rt/lib/dfsan/dfsan.cpp


Index: compiler-rt/lib/dfsan/dfsan.cpp
===================================================================
--- compiler-rt/lib/dfsan/dfsan.cpp
+++ compiler-rt/lib/dfsan/dfsan.cpp
@@ -428,7 +428,6 @@
 }
 
 extern "C" void dfsan_flush() {
-  UnmapOrDie((void*)ShadowAddr(), UnusedAddr() - ShadowAddr());
   if (!MmapFixedNoReserve(ShadowAddr(), UnusedAddr() - ShadowAddr()))
     Die();
 }
Index: compiler-rt/include/sanitizer/dfsan_interface.h
===================================================================
--- compiler-rt/include/sanitizer/dfsan_interface.h
+++ compiler-rt/include/sanitizer/dfsan_interface.h
@@ -80,9 +80,11 @@
 size_t dfsan_get_label_count(void);
 
 /// Flushes the DFSan shadow, i.e. forgets about all labels currently associated
-/// with the application memory. Will work only if there are no other
-/// threads executing DFSan-instrumented code concurrently.
-/// Use this call to start over the taint tracking within the same procces.
+/// with the application memory.  Use this call to start over the taint tracking
+/// within the same process.
+///
+/// Note: If another thread is working with tainted data during the flush, that
+/// taint could still be written to shadow after the flush.
 void dfsan_flush(void);
 
 /// Sets a callback to be invoked on calls to write().  The callback is invoked


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