[Coverage] Ensure that coverage mapping data has an expected alignment in 'covmapping' files.

Coverage mapping data is organized in a sequence of blocks, each of which is expected
to be aligned by 8 bytes. This feature is used when reading those blocks, see
VersionedCovMapFuncRecordReader::readFunctionRecords(). If a misaligned covearge
mapping data has more than one block, it causes llvm-cov to fail.

Differential Revision: http://reviews.llvm.org/D20285

llvm-svn: 269887

1 files changed, 7 insertions, 0 deletions

diff --git a/llvm/lib/ProfileData/Coverage/CoverageMappingReader.cpp b/llvm/lib/ProfileData/Coverage/CoverageMappingReader.cpp
index 9f27de91bc5..9920c338f2d 100644
--- a/llvm/lib/ProfileData/Coverage/CoverageMappingReader.cpp
+++ b/llvm/lib/ProfileData/Coverage/CoverageMappingReader.cpp
@@ -491,6 +491,13 @@ static std::error_code loadTestingFormat(StringRef Data,
     return coveragemap_error::malformed;
   ProfileNames.create(Data.substr(0, ProfileNamesSize), Address);
   CoverageMapping = Data.substr(ProfileNamesSize);
+  // Skip the padding bytes because coverage map data has an alignment of 8.
+  if (CoverageMapping.size() < 1)
+    return coveragemap_error::truncated;
+  size_t Pad = alignmentAdjustment(CoverageMapping.data(), 8);
+  if (CoverageMapping.size() < Pad)
+    return coveragemap_error::malformed;
+  CoverageMapping = CoverageMapping.substr(Pad);
   return std::error_code();
 }