[compiler-rt][UBSan] Sanitization for alignment assumptions.

Summary:
This is the compiler-rt part.
The clang part is D54589.

This is a second commit, the original one was r351106,
which was mass-reverted in r351159 because 2 compiler-rt tests were failing.

Now, i have fundamentally changed the testing approach:
i malloc a few bytes, intentionally mis-align the pointer
(increment it by one), and check that. Also, i have decreased
the expected alignment. This hopefully should be enough to pacify
all the bots. If not, i guess i might just drop the two 'bad' tests.

Reviewers: filcab, vsk, #sanitizers, vitalybuka, rsmith, morehouse

Reviewed By: morehouse

Subscribers: rjmccall, krytarowski, rsmith, kcc, srhines, kubamracek, dberris, llvm-commits

Tags: #sanitizers

Differential Revision: https://reviews.llvm.org/D54590

llvm-svn: 351178

1 files changed, 11 insertions, 0 deletions

diff --git a/compiler-rt/lib/ubsan/ubsan_handlers.h b/compiler-rt/lib/ubsan/ubsan_handlers.h
index 04405770e58..2bf9ff4320e 100644
--- a/compiler-rt/lib/ubsan/ubsan_handlers.h
+++ b/compiler-rt/lib/ubsan/ubsan_handlers.h
@@ -39,6 +39,17 @@ struct TypeMismatchData {
 /// type.
 RECOVERABLE(type_mismatch_v1, TypeMismatchData *Data, ValueHandle Pointer)
 
+struct AlignmentAssumptionData {
+  SourceLocation Loc;
+  SourceLocation AssumptionLoc;
+  const TypeDescriptor &Type;
+};
+
+/// \brief Handle a runtime alignment assumption check failure,
+/// caused by a misaligned pointer.
+RECOVERABLE(alignment_assumption, AlignmentAssumptionData *Data,
+            ValueHandle Pointer, ValueHandle Alignment, ValueHandle Offset)
+
 struct OverflowData {
   SourceLocation Loc;
   const TypeDescriptor &Type;