Annotate V8 for MemorySanitizer.

src/msan.h

+// Copyright 2013 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// MemorySanitizer support.
+
+#ifndef V8_MSAN_H_
+#define V8_MSAN_H_
+
+#ifndef __has_feature
+#define __has_feature(x) 0
+#endif
+
+#if __has_feature(memory_sanitizer) || defined(MEMORY_SANITIZER)
+
+#include <sanitizer/msan_interface.h>
+
+#ifndef MEMORY_SANITIZER
+#define MEMORY_SANITIZER
+#endif
+
+// An annotation for JIT->C++ transition.
+#define MSAN_RUNTIME_FUNCTION3(a, b, c) \
+  do {                                  \
+    int dummy;                          \
+    __msan_unpoison(&dummy, 65536);     \

[danno, 2013/10/10 14:18:07]

This seems totally arbitrary and extremely fragile. Why 64K? You will end up
unpoisoning stuff in C++ frames above small stacks of JIT frames. If you need to
specifically unpoison parts of the stack, you should know how much and be
precise about it.

I don't feel comfortable at all adding this in this form, since it seems to be a
bug just waiting to happen and it feels likely to break through unrelated to V8
in the future.

+    __msan_unpoison(&(a), sizeof(a));   \
+    __msan_unpoison(&(b), sizeof(b));   \
+    __msan_unpoison(&(c), sizeof(c));   \

[danno, 2013/10/10 14:18:07]

Why are these not covered by the 64K above? From the usage, it appears the
arguments are always parameters to the function this macro is embedded in. If
they are pushed before the call, then they lie at an address above locals in the
current frame?, so the &dummy call should cover them.

[Evgeniy Stepanov, 2013/10/10 15:08:54]

Uninit information for function arguments is passed though a special TLS slot,
unpoisoning stack won't affect it. This is an unfortunate limitation of
operating at LLVM IR level - we don't know the details of the function calling
convention and have to work with an abstact argument list.

+  } while (0)
+#define MSAN_RUNTIME_FUNCTION6(a, b, c, d, e, f) \
+  do {                                           \
+    int dummy;                                   \
+    __msan_unpoison(&dummy, 65536);              \
+    __msan_unpoison(&(a), sizeof(a));            \
+    __msan_unpoison(&(b), sizeof(b));            \
+    __msan_unpoison(&(c), sizeof(c));            \
+    __msan_unpoison(&(d), sizeof(d));            \
+    __msan_unpoison(&(e), sizeof(e));            \
+    __msan_unpoison(&(f), sizeof(f));            \
+  } while (0)
+
+// Marks a memory range as fully initialized.
+#define MSAN_MEMORY_IS_INITIALIZED(p, s) __msan_unpoison((p), (s))
+
+#else
+
+#define MSAN_RUNTIME_FUNCTION3(a, b, c)
+#define MSAN_RUNTIME_FUNCTION6(a, b, c, d, e, f)
+#define MSAN_MEMORY_IS_INITIALIZED(p, s)
+
+#endif
+
+#endif  // V8_MSAN_H_