diff --git a/libc/bionic/execinfo.cpp b/libc/bionic/execinfo.cpp
new file mode 100644
index 0000000..d129f7c
--- /dev/null
+++ b/libc/bionic/execinfo.cpp
@@ -0,0 +1,187 @@
+/*
+ * Copyright (C) 2012 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 <dlfcn.h>
+#include <execinfo.h>
+#include <inttypes.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <unistd.h>
+#include <unwind.h>
+
+#include "private/ScopedFd.h"
+
+struct StackState {
+  void** frames;
+  int frame_count;
+  int cur_frame = 0;
+
+  StackState(void** frames, int frame_count) : frames(frames), frame_count(frame_count) {}
+};
+
+static _Unwind_Reason_Code TraceFunction(_Unwind_Context* context, void* arg) {
+  // The instruction pointer is pointing at the instruction after the return
+  // call on all architectures.
+  // Modify the pc to point at the real function.
+  uintptr_t ip = _Unwind_GetIP(context);
+  if (ip != 0) {
+#if defined(__arm__)
+    // If the ip is suspiciously low, do nothing to avoid a segfault trying
+    // to access this memory.
+    if (ip >= 4096) {
+      // Check bits [15:11] of the first halfword assuming the instruction
+      // is 32 bits long. If the bits are any of these values, then our
+      // assumption was correct:
+      //  b11101
+      //  b11110
+      //  b11111
+      // Otherwise, this is a 16 bit instruction.
+      uint16_t value = (*reinterpret_cast<uint16_t*>(ip - 2)) >> 11;
+      if (value == 0x1f || value == 0x1e || value == 0x1d) {
+        ip -= 4;
+      } else {
+        ip -= 2;
+      }
+    }
+#elif defined(__aarch64__)
+    // All instructions are 4 bytes long, skip back one instruction.
+    ip -= 4;
+#elif defined(__i386__) || defined(__x86_64__)
+    // It's difficult to decode exactly where the previous instruction is,
+    // so subtract 1 to estimate where the instruction lives.
+    ip--;
+#endif
+  }
+
+  StackState* state = static_cast<StackState*>(arg);
+  state->frames[state->cur_frame++] = reinterpret_cast<void*>(ip);
+  return (state->cur_frame >= state->frame_count) ? _URC_END_OF_STACK : _URC_NO_REASON;
+}
+
+int backtrace(void** buffer, int size) {
+  if (size <= 0) {
+    return 0;
+  }
+
+  StackState state(buffer, size);
+  _Unwind_Backtrace(TraceFunction, &state);
+  return state.cur_frame;
+}
+
+char** backtrace_symbols(void* const* buffer, int size) {
+  if (size <= 0) {
+    return nullptr;
+  }
+  // Do this calculation first in case the user passes in a bad value.
+  size_t ptr_size;
+  if (__builtin_mul_overflow(sizeof(char*), size, &ptr_size)) {
+    return nullptr;
+  }
+
+  ScopedFd fd(memfd_create("backtrace_symbols_fd", MFD_CLOEXEC));
+  if (fd.get() == -1) {
+    return nullptr;
+  }
+  backtrace_symbols_fd(buffer, size, fd.get());
+
+  // Get the size of the file.
+  off_t file_size = lseek(fd.get(), 0, SEEK_END);
+  if (file_size <= 0) {
+    return nullptr;
+  }
+
+  // The interface for backtrace_symbols indicates that only the single
+  // returned pointer must be freed by the caller. Therefore, allocate a
+  // buffer that includes the memory for the strings and all of the pointers.
+  // Add one byte at the end just in case the file didn't end with a '\n'.
+  size_t symbol_data_size;
+  if (__builtin_add_overflow(ptr_size, file_size, &symbol_data_size) ||
+      __builtin_add_overflow(symbol_data_size, 1, &symbol_data_size)) {
+    return nullptr;
+  }
+
+  uint8_t* symbol_data = reinterpret_cast<uint8_t*>(malloc(symbol_data_size));
+  if (symbol_data == nullptr) {
+    return nullptr;
+  }
+
+  // Copy the string data into the buffer.
+  char* cur_string = reinterpret_cast<char*>(&symbol_data[ptr_size]);
+  // If this fails, the read won't read back the correct number of bytes.
+  lseek(fd.get(), 0, SEEK_SET);
+  ssize_t num_read = read(fd.get(), cur_string, file_size);
+  fd.reset(-1);
+  if (num_read != file_size) {
+    free(symbol_data);
+    return nullptr;
+  }
+
+  // Make sure the last character in the file is '\n'.
+  if (cur_string[file_size] != '\n') {
+    cur_string[file_size++] = '\n';
+  }
+
+  for (int i = 0; i < size; i++) {
+    (reinterpret_cast<char**>(symbol_data))[i] = cur_string;
+    cur_string = strchr(cur_string, '\n');
+    if (cur_string == nullptr) {
+      free(symbol_data);
+      return nullptr;
+    }
+    cur_string[0] = '\0';
+    cur_string++;
+  }
+  return reinterpret_cast<char**>(symbol_data);
+}
+
+// This function should do no allocations if possible.
+void backtrace_symbols_fd(void* const* buffer, int size, int fd) {
+  if (size <= 0 || fd < 0) {
+    return;
+  }
+
+  for (int frame_num = 0; frame_num < size; frame_num++) {
+    void* address = buffer[frame_num];
+    Dl_info info;
+    if (dladdr(address, &info) != 0) {
+      if (info.dli_fname != nullptr) {
+        write(fd, info.dli_fname, strlen(info.dli_fname));
+      }
+      if (info.dli_sname != nullptr) {
+        dprintf(fd, "(%s+0x%" PRIxPTR ") ", info.dli_sname,
+                reinterpret_cast<uintptr_t>(address) - reinterpret_cast<uintptr_t>(info.dli_saddr));
+      } else {
+        dprintf(fd, "(+%p) ", info.dli_saddr);
+      }
+    }
+
+    dprintf(fd, "[%p]\n", address);
+  }
+}