1 files changed, 87 insertions, 0 deletions
diff --git a/mfbt/TaggedAnonymousMemory.h b/mfbt/TaggedAnonymousMemory.h
new file mode 100644
index 0000000000..ebd2c00318
--- /dev/null
+++ b/mfbt/TaggedAnonymousMemory.h
@@ -0,0 +1,87 @@
+/* -*- 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/. */
+
+// Some Linux kernels -- specifically, newer versions of Android and
+// some B2G devices -- have a feature for assigning names to ranges of
+// anonymous memory (i.e., memory that doesn't have a "name" in the
+// form of an underlying mapped file).  These names are reported in
+// /proc/<pid>/smaps alongside system-level memory usage information
+// such as Proportional Set Size (memory usage adjusted for sharing
+// between processes), which allows reporting this information at a
+// finer granularity than would otherwise be possible (e.g.,
+// separating malloc() heap from JS heap).
+//
+// Existing memory can be tagged with MozTagAnonymousMemory(); it will
+// tag the range of complete pages containing the given interval, so
+// the results may be inexact if the range isn't page-aligned.
+// MozTaggedAnonymousMmap() can be used like mmap() with an extra
+// parameter, and will tag the returned memory if the mapping was
+// successful (and if it was in fact anonymous).
+//
+// NOTE: The pointer given as the "tag" argument MUST remain valid as
+// long as the mapping exists.  The referenced string is read when
+// /proc/<pid>/smaps or /proc/<pid>/maps is read, not when the tag is
+// established, so freeing it or changing its contents will have
+// unexpected results.  Using a static string is probably best.
+//
+// Also note that this header can be used by both C and C++ code.
+
+#ifndef mozilla_TaggedAnonymousMemory_h
+#define mozilla_TaggedAnonymousMemory_h
+
+#ifndef XP_WIN
+
+#  ifdef __wasi__
+#    include <stdlib.h>
+#  else
+#    include <sys/types.h>
+#    include <sys/mman.h>
+#  endif  // __wasi__
+
+#  include "mozilla/Types.h"
+
+#  ifdef ANDROID
+
+#    ifdef __cplusplus
+extern "C" {
+#    endif
+
+MFBT_API void MozTagAnonymousMemory(const void* aPtr, size_t aLength,
+                                    const char* aTag);
+
+MFBT_API void* MozTaggedAnonymousMmap(void* aAddr, size_t aLength, int aProt,
+                                      int aFlags, int aFd, off_t aOffset,
+                                      const char* aTag);
+
+MFBT_API int MozTaggedMemoryIsSupported(void);
+
+#    ifdef __cplusplus
+}  // extern "C"
+#    endif
+
+#  else  // ANDROID
+
+static inline void MozTagAnonymousMemory(const void* aPtr, size_t aLength,
+                                         const char* aTag) {}
+
+static inline void* MozTaggedAnonymousMmap(void* aAddr, size_t aLength,
+                                           int aProt, int aFlags, int aFd,
+                                           off_t aOffset, const char* aTag) {
+#    ifdef __wasi__
+  MOZ_CRASH("We don't use this memory for WASI right now.");
+  return nullptr;
+#    else
+  return mmap(aAddr, aLength, aProt, aFlags, aFd, aOffset);
+#    endif
+}
+
+static inline int MozTaggedMemoryIsSupported(void) { return 0; }
+
+#  endif  // ANDROID
+
+#endif  // !XP_WIN
+
+#endif  // mozilla_TaggedAnonymousMemory_h