[UBSan] Add returns-nonnull sanitizer.

Summary:
This patch adds a runtime check verifying that functions
annotated with "returns_nonnull" attribute do in fact return nonnull pointers.
It is based on suggestion by Jakub Jelinek:
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20140623/223693.html.

Test Plan: regression test suite

Reviewers: rsmith

Reviewed By: rsmith

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D4849

llvm-svn: 215485

3 files changed, 39 insertions, 0 deletions

diff --git a/compiler-rt/lib/ubsan/ubsan_handlers.cc b/compiler-rt/lib/ubsan/ubsan_handlers.cc
index afda39332f2..14b12b6a97f 100644
--- a/compiler-rt/lib/ubsan/ubsan_handlers.cc
+++ b/compiler-rt/lib/ubsan/ubsan_handlers.cc
@@ -308,3 +308,22 @@ void __ubsan::__ubsan_handle_function_type_mismatch_abort(
     FunctionTypeMismatchData *Data, ValueHandle Function) {
   handleFunctionTypeMismatch(Data, Function, true);
 }
+
+static void handleNonnullReturn(NonNullReturnData *Data, bool Abort) {
+  SourceLocation Loc = Data->Loc.acquire();
+  if (Loc.isDisabled())
+    return;
+
+  ScopedReport R(Abort);
+
+  Diag(Loc, DL_Error, "null pointer returned from function declared to never "
+                      "return null");
+}
+
+void __ubsan::__ubsan_handle_nonnull_return(NonNullReturnData *Data) {
+  handleNonnullReturn(Data, false);
+}
+
+void __ubsan::__ubsan_handle_nonnull_return_abort(NonNullReturnData *Data) {
+  handleNonnullReturn(Data, true);
+}
diff --git a/compiler-rt/lib/ubsan/ubsan_handlers.h b/compiler-rt/lib/ubsan/ubsan_handlers.h
index 14e6f04c2a1..910198c51a4 100644
--- a/compiler-rt/lib/ubsan/ubsan_handlers.h
+++ b/compiler-rt/lib/ubsan/ubsan_handlers.h
@@ -121,6 +121,13 @@ RECOVERABLE(function_type_mismatch,
             FunctionTypeMismatchData *Data,
             ValueHandle Val)
 
+struct NonNullReturnData {
+  SourceLocation Loc;
+};
+
+/// \brief Handle returning null from function with returns_nonnull attribute.
+RECOVERABLE(nonnull_return, NonNullReturnData *Data)
+
 }
 
 #endif // UBSAN_HANDLERS_H
diff --git a/compiler-rt/test/ubsan/TestCases/Misc/nonnull.cpp b/compiler-rt/test/ubsan/TestCases/Misc/nonnull.cpp
new file mode 100644
index 00000000000..8b5fcaf43bf
--- /dev/null
+++ b/compiler-rt/test/ubsan/TestCases/Misc/nonnull.cpp
@@ -0,0 +1,13 @@
+// RUN: %clangxx -fsanitize=returns-nonnull-attribute %s -O3 -o %t
+// RUN: %run %t foo
+// RUN: %run %t 2>&1 | FileCheck %s
+
+__attribute__((returns_nonnull))
+char *foo(char *a) {
+  return a;
+  // CHECK: nonnull.cpp:[[@LINE+1]]:1: runtime error: null pointer returned from function declared to never return null
+}
+
+int main(int argc, char **argv) {
+  return foo(argv[1]) == 0;
+}