[llvm] r222763 - [msan] Annotate zlib functions for MemorySanitizer.

[Evgeniy Stepanov]

Author: eugenis
Date: Tue Nov 25 09:24:07 2014
New Revision: 222763

URL: http://llvm.org/viewvc/llvm-project?rev=222763&view=rev
Log:
[msan] Annotate zlib functions for MemorySanitizer.

Mark destination buffer in zlib::compress and zlib::decompress as fully
initialized.

When building LLVM with system zlib and MemorySanitizer instrumentation,
MSan does not observe memory writes in zlib code and erroneously considers
zlib output buffers as uninitialized, resulting in false use-of-uninitialized
memory reports. This change helps MSan understand the state of that memory
and prevents such reports.

Modified:
    llvm/trunk/lib/Support/Compression.cpp

Modified: llvm/trunk/lib/Support/Compression.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/Compression.cpp?rev=222763&r1=222762&r2=222763&view=diff
==============================================================================
--- llvm/trunk/lib/Support/Compression.cpp (original)
+++ llvm/trunk/lib/Support/Compression.cpp Tue Nov 25 09:24:07 2014
@@ -54,6 +54,9 @@ zlib::Status zlib::compress(StringRef In
   Status Res = encodeZlibReturnValue(::compress2(
       (Bytef *)CompressedBuffer.data(), &CompressedSize,
       (const Bytef *)InputBuffer.data(), InputBuffer.size(), CLevel));
+  // Tell MemorySanitizer that zlib output buffer is fully initialized.
+  // This avoids a false report when running LLVM with uninstrumented ZLib.
+  __msan_unpoison(CompressedBuffer.data(), CompressedSize);
   CompressedBuffer.resize(CompressedSize);
   return Res;
 }
@@ -65,6 +68,9 @@ zlib::Status zlib::uncompress(StringRef
   Status Res = encodeZlibReturnValue(::uncompress(
       (Bytef *)UncompressedBuffer.data(), (uLongf *)&UncompressedSize,
       (const Bytef *)InputBuffer.data(), InputBuffer.size()));
+  // Tell MemorySanitizer that zlib output buffer is fully initialized.
+  // This avoids a false report when running LLVM with uninstrumented ZLib.
+  __msan_unpoison(UncompressedBuffer.data(), UncompressedSize);
   UncompressedBuffer.resize(UncompressedSize);
   return Res;
 }