Imported from /home/lorry/working-area/delta_mozilla_mozjs24/mozjs-24.2.0.tar.bz2.HEADmozjs-24.2.0master

1 files changed, 61 insertions, 0 deletions

diff --git a/mfbt/Poison.h b/mfbt/Poison.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * A poison value that can be used to fill a memory space with
+ * an address that leads to a safe crash when dereferenced.
+ */
+
+#ifndef mozilla_Poison_h_
+#define mozilla_Poison_h_
+
+#include "mozilla/Assertions.h"
+#include "mozilla/StandardInteger.h"
+#include "mozilla/Types.h"
+
+MOZ_BEGIN_EXTERN_C
+
+extern MFBT_DATA uintptr_t gMozillaPoisonValue;
+
+/**
+ * @return the poison value.
+ */
+inline uintptr_t mozPoisonValue()
+{
+  return gMozillaPoisonValue;
+}
+
+/**
+ * Overwrite the memory block of aSize bytes at aPtr with the poison value.
+ * aPtr MUST be aligned at a sizeof(uintptr_t) boundary.
+ * Only an even number of sizeof(uintptr_t) bytes are overwritten, the last
+ * few bytes (if any) is not overwritten.
+ */
+inline void mozWritePoison(void* aPtr, size_t aSize)
+{
+  const uintptr_t POISON = mozPoisonValue();
+  char* p = (char*)aPtr;
+  char* limit = p + aSize;
+  MOZ_ASSERT((uintptr_t)aPtr % sizeof(uintptr_t) == 0, "bad alignment");
+  MOZ_ASSERT(aSize >= sizeof(uintptr_t), "poisoning this object has no effect");
+  for (; p < limit; p += sizeof(uintptr_t)) {
+    *((uintptr_t*)p) = POISON;
+  }
+}
+
+/**
+ * Initialize the poison value.
+ * This should only be called once.
+ */
+extern MFBT_API void mozPoisonValueInit();
+
+/* Values annotated by CrashReporter */
+extern MFBT_DATA uintptr_t gMozillaPoisonBase;
+extern MFBT_DATA uintptr_t gMozillaPoisonSize;
+
+MOZ_END_EXTERN_C
+
+#endif /* mozilla_Poison_h_ */