1 files changed, 113 insertions, 0 deletions
diff --git a/mozglue/misc/MmapFaultHandler.h b/mozglue/misc/MmapFaultHandler.h
new file mode 100644
index 0000000000..fca356921c
--- /dev/null
+++ b/mozglue/misc/MmapFaultHandler.h
@@ -0,0 +1,113 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/. */
+
+#ifndef MmapFaultHandler_h_
+#define MmapFaultHandler_h_
+
+#if defined(XP_WIN)
+// Windows
+
+#  ifdef HAVE_SEH_EXCEPTIONS
+#    define MMAP_FAULT_HANDLER_BEGIN_HANDLE(fd) __try {
+#    define MMAP_FAULT_HANDLER_BEGIN_BUFFER(buf, bufLen) __try {
+#    define MMAP_FAULT_HANDLER_CATCH(retval)                  \
+      }                                                       \
+      __except (GetExceptionCode() == EXCEPTION_IN_PAGE_ERROR \
+                    ? EXCEPTION_EXECUTE_HANDLER               \
+                    : EXCEPTION_CONTINUE_SEARCH) {            \
+        NS_WARNING("unexpected EXCEPTION_IN_PAGE_ERROR");     \
+        return retval;                                        \
+      }
+#  else
+#    define MMAP_FAULT_HANDLER_BEGIN_HANDLE(fd) {
+#    define MMAP_FAULT_HANDLER_BEGIN_BUFFER(buf, bufLen) {
+#    define MMAP_FAULT_HANDLER_CATCH(retval) }
+#  endif
+
+#elif defined(XP_DARWIN)
+// MacOS
+
+#  define MMAP_FAULT_HANDLER_BEGIN_HANDLE(fd) {
+#  define MMAP_FAULT_HANDLER_BEGIN_BUFFER(buf, bufLen) {
+#  define MMAP_FAULT_HANDLER_CATCH(retval) }
+
+#elif defined(__wasi__)
+
+#  define MMAP_FAULT_HANDLER_BEGIN_HANDLE(fd) {
+#  define MMAP_FAULT_HANDLER_BEGIN_BUFFER(buf, bufLen) {
+#  define MMAP_FAULT_HANDLER_CATCH(retval) }
+
+#else
+// Linux
+
+#  include "mozilla/Attributes.h"
+#  include "mozilla/Types.h"
+#  include <stdint.h>
+#  include <setjmp.h>
+
+class MOZ_RAII MmapAccessScope {
+ public:
+  MFBT_API MmapAccessScope(void* aBuf, uint32_t aBufLen,
+                           const char* aFilename = nullptr);
+  MFBT_API ~MmapAccessScope();
+
+  MmapAccessScope(const MmapAccessScope&) = delete;
+  MmapAccessScope& operator=(const MmapAccessScope&) = delete;
+
+  void SetThreadLocalScope();
+  bool IsInsideBuffer(void* aPtr);
+  void CrashWithInfo(void* aPtr);
+
+  // sigsetjmp cannot be called from a method that returns before calling
+  // siglongjmp, so the macro must call sigsetjmp directly and mJmpBuf must be
+  // public.
+  sigjmp_buf mJmpBuf;
+
+ private:
+  void* mBuf;
+  const char* mFilename;
+  uint32_t mBufLen;
+  MmapAccessScope* mPreviousScope;
+};
+
+// Gets around warnings for null-checking in a macro.
+template <typename T>
+inline bool ValidFD(T fd) {
+  return !!fd;
+}
+
+#  define MMAP_FAULT_HANDLER_BEGIN_HANDLE(fd)                  \
+    {                                                          \
+      void* mmapScopeBuf = nullptr;                            \
+      nsCString mmapScopeFilename;                             \
+      uint32_t mmapScopeBufLen = 0;                            \
+      if (ValidFD(fd) && fd->mMap) {                           \
+        mmapScopeBuf = (void*)fd->mFileStart;                  \
+        mmapScopeBufLen = fd->mTotalLen;                       \
+      }                                                        \
+      if (ValidFD(fd) && fd->mFile) {                          \
+        nsCOMPtr<nsIFile> file = fd->mFile.GetBaseFile();      \
+        if (file) {                                            \
+          file->GetNativeLeafName(mmapScopeFilename);          \
+        }                                                      \
+      }                                                        \
+      MmapAccessScope mmapScope(mmapScopeBuf, mmapScopeBufLen, \
+                                mmapScopeFilename.get());      \
+      if (sigsetjmp(mmapScope.mJmpBuf, 0) == 0) {
+#  define MMAP_FAULT_HANDLER_BEGIN_BUFFER(buf, bufLen)   \
+    {                                                    \
+      MmapAccessScope mmapScope((void*)(buf), (bufLen)); \
+      if (sigsetjmp(mmapScope.mJmpBuf, 0) == 0) {
+#  define MMAP_FAULT_HANDLER_CATCH(retval)                       \
+    }                                                            \
+    else {                                                       \
+      NS_WARNING("SIGBUS received when accessing mmapped file"); \
+      return retval;                                             \
+    }                                                            \
+    }
+
+#endif
+
+#endif