diff --git a/libc/malloc_debug/GuardData.cpp b/libc/malloc_debug/GuardData.cpp
new file mode 100644
index 0000000..4ba5253
--- /dev/null
+++ b/libc/malloc_debug/GuardData.cpp
@@ -0,0 +1,101 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ * 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.
+ *
+ * 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.
+ */
+
+#include <stdint.h>
+#include <string.h>
+
+#include <vector>
+
+#include "backtrace.h"
+#include "Config.h"
+#include "debug_disable.h"
+#include "debug_log.h"
+#include "DebugData.h"
+#include "malloc_debug.h"
+#include "GuardData.h"
+
+GuardData::GuardData(int init_value, size_t num_bytes) {
+  // Create a buffer for fast comparisons of the front guard.
+  cmp_mem_.resize(num_bytes);
+  memset(cmp_mem_.data(), init_value, cmp_mem_.size());
+}
+
+void GuardData::LogFailure(const Header* header, const void* pointer, const void* data) {
+  ScopedDisableDebugCalls disable;
+
+  error_log(LOG_DIVIDER);
+  error_log("+++ ALLOCATION %p SIZE %zu HAS A CORRUPTED %s GUARD", pointer,
+            header->real_size(), GetTypeName());
+
+  // Log all of the failing bytes.
+  const uint8_t* expected = cmp_mem_.data();
+  int pointer_idx = reinterpret_cast<uintptr_t>(data) - reinterpret_cast<uintptr_t>(pointer);
+  const uint8_t* real = reinterpret_cast<const uint8_t*>(data);
+  for (size_t i = 0; i < cmp_mem_.size(); i++, pointer_idx++) {
+    if (real[i] != expected[i]) {
+      error_log("  pointer[%d] = 0x%02x (expected 0x%02x)", pointer_idx, real[i], expected[i]);
+    }
+  }
+
+  error_log("Backtrace at time of failure:");
+  std::vector<uintptr_t> frames(64);
+  size_t frame_num = backtrace_get(frames.data(), frames.size());
+  frames.resize(frame_num);
+  backtrace_log(frames.data(), frames.size());
+  error_log(LOG_DIVIDER);
+}
+
+FrontGuardData::FrontGuardData(const Config& config, size_t* offset)
+   : GuardData(config.front_guard_value, config.front_guard_bytes) {
+  // Create a buffer for fast comparisons of the front guard.
+  cmp_mem_.resize(config.front_guard_bytes);
+  memset(cmp_mem_.data(), config.front_guard_value, cmp_mem_.size());
+  // Assumes that front_bytes is a multiple of sizeof(uintptr_t).
+  offset_ = *offset;
+  *offset += config.front_guard_bytes;
+}
+
+bool FrontGuardData::Valid(DebugData& debug, const Header* header) {
+  return GuardData::Valid(debug.GetFrontGuard(header));
+}
+
+void FrontGuardData::LogFailure(DebugData& debug, const Header* header) {
+  GuardData::LogFailure(header, debug.GetPointer(header), debug.GetFrontGuard(header));
+}
+
+RearGuardData::RearGuardData(const Config& config)
+    : GuardData(config.rear_guard_value, config.rear_guard_bytes) {
+}
+
+bool RearGuardData::Valid(DebugData& debug, const Header* header) {
+  return GuardData::Valid(debug.GetRearGuard(header));
+}
+
+void RearGuardData::LogFailure(DebugData& debug, const Header* header) {
+  GuardData::LogFailure(header, debug.GetPointer(header), debug.GetRearGuard(header));
+}