1 files changed, 93 insertions, 0 deletions
diff --git a/mfbt/TaggedAnonymousMemory.cpp b/mfbt/TaggedAnonymousMemory.cpp
new file mode 100644
index 0000000000..07262b01ae
--- /dev/null
+++ b/mfbt/TaggedAnonymousMemory.cpp
@@ -0,0 +1,93 @@
+/* -*- 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/. */
+
+#ifdef ANDROID
+
+#  include "mozilla/TaggedAnonymousMemory.h"
+
+#  include <sys/types.h>
+#  include <sys/mman.h>
+#  include <sys/prctl.h>
+#  include <sys/syscall.h>
+#  include <unistd.h>
+
+#  include "mozilla/Assertions.h"
+
+// These constants are copied from <sys/prctl.h>, because the headers
+// used for building may not have them even though the running kernel
+// supports them.
+#  ifndef PR_SET_VMA
+#    define PR_SET_VMA 0x53564d41
+#  endif
+#  ifndef PR_SET_VMA_ANON_NAME
+#    define PR_SET_VMA_ANON_NAME 0
+#  endif
+
+namespace mozilla {
+
+// Returns 0 for success and -1 (with errno) for error.
+static int TagAnonymousMemoryAligned(const void* aPtr, size_t aLength,
+                                     const char* aTag) {
+  return prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME,
+               reinterpret_cast<unsigned long>(aPtr), aLength,
+               reinterpret_cast<unsigned long>(aTag));
+}
+
+// On some architectures, it's possible for the page size to be larger
+// than the PAGE_SIZE we were compiled with.  This computes the
+// equivalent of PAGE_MASK.
+static uintptr_t GetPageMask() {
+  static uintptr_t mask = 0;
+
+  if (mask == 0) {
+    uintptr_t pageSize = sysconf(_SC_PAGESIZE);
+    mask = ~(pageSize - 1);
+    MOZ_ASSERT((pageSize & (pageSize - 1)) == 0,
+               "Page size must be a power of 2!");
+  }
+  return mask;
+}
+
+}  // namespace mozilla
+
+int MozTaggedMemoryIsSupported(void) {
+  static int supported = -1;
+
+  if (supported == -1) {
+    // Tagging an empty range always "succeeds" if the feature is supported,
+    // regardless of the start pointer.
+    supported = mozilla::TagAnonymousMemoryAligned(nullptr, 0, nullptr) == 0;
+  }
+  return supported;
+}
+
+void MozTagAnonymousMemory(const void* aPtr, size_t aLength, const char* aTag) {
+  if (MozTaggedMemoryIsSupported()) {
+    // The kernel will round up the end of the range to the next page
+    // boundary if it's not aligned (comments indicate this behavior
+    // is based on that of madvise), but it will reject the request if
+    // the start is not aligned.  We therefore round down the start
+    // address and adjust the length accordingly.
+    uintptr_t addr = reinterpret_cast<uintptr_t>(aPtr);
+    uintptr_t end = addr + aLength;
+    uintptr_t addrRounded = addr & mozilla::GetPageMask();
+    const void* ptrRounded = reinterpret_cast<const void*>(addrRounded);
+
+    mozilla::TagAnonymousMemoryAligned(ptrRounded, end - addrRounded, aTag);
+  }
+}
+
+void* MozTaggedAnonymousMmap(void* aAddr, size_t aLength, int aProt, int aFlags,
+                             int aFd, off_t aOffset, const char* aTag) {
+  void* mapped = mmap(aAddr, aLength, aProt, aFlags, aFd, aOffset);
+  if (MozTaggedMemoryIsSupported() &&
+      (aFlags & MAP_ANONYMOUS) == MAP_ANONYMOUS && mapped != MAP_FAILED) {
+    mozilla::TagAnonymousMemoryAligned(mapped, aLength, aTag);
+  }
+  return mapped;
+}
+
+#endif  // ANDROID