diff --git a/cmds/atrace/Android.mk b/cmds/atrace/Android.mk
index 12526d0..028ca8f 100644
--- a/cmds/atrace/Android.mk
+++ b/cmds/atrace/Android.mk
@@ -3,15 +3,18 @@
 LOCAL_PATH:= $(call my-dir)
 include $(CLEAR_VARS)
 
-LOCAL_SRC_FILES:= atrace.c
+LOCAL_SRC_FILES:= atrace.cpp
 
 LOCAL_C_INCLUDES += external/zlib
-LOCAL_CFLAGS += -std=c99
 
 LOCAL_MODULE:= atrace
 
 LOCAL_MODULE_TAGS:= optional
 
-LOCAL_SHARED_LIBRARIES := libz
+LOCAL_SHARED_LIBRARIES := \
+    libbinder \
+    libcutils \
+    libutils \
+    libz \
 
 include $(BUILD_EXECUTABLE)
diff --git a/cmds/atrace/atrace.c b/cmds/atrace/atrace.c
deleted file mode 100644
index 64f13e4..0000000
--- a/cmds/atrace/atrace.c
+++ /dev/null
@@ -1,643 +0,0 @@
-/*
- * Copyright (C) 2012 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#include <errno.h>
-#include <fcntl.h>
-#include <getopt.h>
-#include <signal.h>
-#include <stdarg.h>
-#include <stdbool.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <sys/sendfile.h>
-#include <time.h>
-#include <zlib.h>
-
-#define NELEM(x) ((int) (sizeof(x) / sizeof((x)[0])))
-
-/* Command line options */
-static int g_traceDurationSeconds = 5;
-static bool g_traceSchedSwitch = false;
-static bool g_traceFrequency = false;
-static bool g_traceBusUtilization = false;
-static bool g_traceCpuIdle = false;
-static bool g_traceDisk = false;
-static bool g_traceGovernorLoad = false;
-static bool g_traceSync = false;
-static bool g_traceWorkqueue = false;
-static bool g_traceOverwrite = false;
-static int g_traceBufferSizeKB = 2048;
-static bool g_compress = false;
-static bool g_nohup = false;
-static int g_initialSleepSecs = 0;
-
-/* Global state */
-static bool g_traceAborted = false;
-
-/* Sys file paths */
-static const char* k_traceClockPath =
-    "/sys/kernel/debug/tracing/trace_clock";
-
-static const char* k_traceBufferSizePath =
-    "/sys/kernel/debug/tracing/buffer_size_kb";
-
-static const char* k_tracingOverwriteEnablePath =
-    "/sys/kernel/debug/tracing/options/overwrite";
-
-static const char* k_schedSwitchEnablePath =
-    "/sys/kernel/debug/tracing/events/sched/sched_switch/enable";
-
-static const char* k_schedWakeupEnablePath =
-    "/sys/kernel/debug/tracing/events/sched/sched_wakeup/enable";
-
-static const char* k_memoryBusEnablePath =
-    "/sys/kernel/debug/tracing/events/memory_bus/enable";
-
-static const char* k_cpuFreqEnablePath =
-    "/sys/kernel/debug/tracing/events/power/cpu_frequency/enable";
-
-static const char *k_clockSetRateEnablePath =
-    "/sys/kernel/debug/tracing/events/power/clock_set_rate/enable";
-
-static const char* k_cpuIdleEnablePath =
-    "/sys/kernel/debug/tracing/events/power/cpu_idle/enable";
-
-static const char* k_governorLoadEnablePath =
-    "/sys/kernel/debug/tracing/events/cpufreq_interactive/enable";
-
-static const char* k_syncEnablePath =
-    "/sys/kernel/debug/tracing/events/sync/enable";
-
-static const char* k_workqueueEnablePath =
-    "/sys/kernel/debug/tracing/events/workqueue/enable";
-
-static const char* k_diskEnablePaths[] = {
-        "/sys/kernel/debug/tracing/events/ext4/ext4_sync_file_enter/enable",
-        "/sys/kernel/debug/tracing/events/ext4/ext4_sync_file_exit/enable",
-        "/sys/kernel/debug/tracing/events/block/block_rq_issue/enable",
-        "/sys/kernel/debug/tracing/events/block/block_rq_complete/enable",
-};
-
-static const char* k_tracingOnPath =
-    "/sys/kernel/debug/tracing/tracing_on";
-
-static const char* k_tracePath =
-    "/sys/kernel/debug/tracing/trace";
-
-static const char* k_traceMarkerPath =
-    "/sys/kernel/debug/tracing/trace_marker";
-
-// Check whether a file exists.
-static bool fileExists(const char* filename) {
-    return access(filename, F_OK) != -1;
-}
-
-// Write a string to a file, returning true if the write was successful.
-bool writeStr(const char* filename, const char* str)
-{
-    int fd = open(filename, O_WRONLY);
-    if (fd == -1) {
-        fprintf(stderr, "error opening %s: %s (%d)\n", filename,
-                strerror(errno), errno);
-        return false;
-    }
-
-    bool ok = true;
-    ssize_t len = strlen(str);
-    if (write(fd, str, len) != len) {
-        fprintf(stderr, "error writing to %s: %s (%d)\n", filename,
-                strerror(errno), errno);
-        ok = false;
-    }
-
-    close(fd);
-
-    return ok;
-}
-
-// Enable or disable a kernel option by writing a "1" or a "0" into a /sys file.
-static bool setKernelOptionEnable(const char* filename, bool enable)
-{
-    return writeStr(filename, enable ? "1" : "0");
-}
-
-// Enable or disable a collection of kernel options by writing a "1" or a "0" into each /sys file.
-static bool setMultipleKernelOptionsEnable(const char** filenames, size_t count, bool enable)
-{
-    bool result = true;
-    for (size_t i = 0; i < count; i++) {
-        result &= setKernelOptionEnable(filenames[i], enable);
-    }
-    return result;
-}
-
-// Enable or disable overwriting of the kernel trace buffers.  Disabling this
-// will cause tracing to stop once the trace buffers have filled up.
-static bool setTraceOverwriteEnable(bool enable)
-{
-    return setKernelOptionEnable(k_tracingOverwriteEnablePath, enable);
-}
-
-// Enable or disable tracing of the kernel scheduler switching.
-static bool setSchedSwitchTracingEnable(bool enable)
-{
-    bool ok = true;
-    ok &= setKernelOptionEnable(k_schedSwitchEnablePath, enable);
-    ok &= setKernelOptionEnable(k_schedWakeupEnablePath, enable);
-    return ok;
-}
-
-// Enable or disable tracing of the Bus utilization.
-static bool setBusUtilizationTracingEnable(bool enable)
-{
-    bool ok = true, oneSet = false;
-    // these can be platform specific so make sure that at least
-    // one succeeds.
-    if (fileExists(k_memoryBusEnablePath)) {
-        ok &= setKernelOptionEnable(k_memoryBusEnablePath, enable);
-        oneSet |= ok;
-    }
-    return ok && (oneSet || !enable);
-}
-
-// Enable or disable tracing of the CPU clock frequency.
-static bool setFrequencyTracingEnable(bool enable)
-{
-    bool ok = true;
-    ok &= setKernelOptionEnable(k_cpuFreqEnablePath, enable);
-    if (fileExists(k_clockSetRateEnablePath)) {
-        ok &= setKernelOptionEnable(k_clockSetRateEnablePath, enable);
-    }
-    return ok;
-}
-
-// Enable or disable tracing of CPU idle events.
-static bool setCpuIdleTracingEnable(bool enable)
-{
-    return setKernelOptionEnable(k_cpuIdleEnablePath, enable);
-}
-
-// Enable or disable tracing of the interactive CPU frequency governor's idea of
-// the CPU load.
-static bool setGovernorLoadTracingEnable(bool enable)
-{
-    bool ok = true;
-    if (fileExists(k_governorLoadEnablePath) || enable) {
-        ok &= setKernelOptionEnable(k_governorLoadEnablePath, enable);
-    }
-    return ok;
-}
-
-// Enable or disable tracing of sync timelines and waits.
-static bool setSyncTracingEnabled(bool enable)
-{
-    bool ok = true;
-    if (fileExists(k_syncEnablePath) || enable) {
-        ok &= setKernelOptionEnable(k_syncEnablePath, enable);
-    }
-    return ok;
-}
-
-// Enable or disable tracing of the kernel workqueues.
-static bool setWorkqueueTracingEnabled(bool enable)
-{
-    return setKernelOptionEnable(k_workqueueEnablePath, enable);
-}
-
-// Enable or disable tracing of disk I/O.
-static bool setDiskTracingEnabled(bool enable)
-{
-    return setMultipleKernelOptionsEnable(k_diskEnablePaths, NELEM(k_diskEnablePaths), enable);
-}
-
-// Enable or disable kernel tracing.
-static bool setTracingEnabled(bool enable)
-{
-    return setKernelOptionEnable(k_tracingOnPath, enable);
-}
-
-// Clear the contents of the kernel trace.
-static bool clearTrace()
-{
-    int traceFD = creat(k_tracePath, 0);
-    if (traceFD == -1) {
-        fprintf(stderr, "error truncating %s: %s (%d)\n", k_tracePath,
-                strerror(errno), errno);
-        return false;
-    }
-
-    close(traceFD);
-
-    return true;
-}
-
-// Set the size of the kernel's trace buffer in kilobytes.
-static bool setTraceBufferSizeKB(int size)
-{
-    char str[32] = "1";
-    int len;
-    if (size < 1) {
-        size = 1;
-    }
-    snprintf(str, 32, "%d", size);
-    return writeStr(k_traceBufferSizePath, str);
-}
-
-// Enable or disable the kernel's use of the global clock.  Disabling the global
-// clock will result in the kernel using a per-CPU local clock.
-static bool setGlobalClockEnable(bool enable)
-{
-    return writeStr(k_traceClockPath, enable ? "global" : "local");
-}
-
-// Enable tracing in the kernel.
-static bool startTrace(bool isRoot)
-{
-    bool ok = true;
-
-    // Set up the tracing options that don't require root.
-    ok &= setTraceOverwriteEnable(g_traceOverwrite);
-    ok &= setSchedSwitchTracingEnable(g_traceSchedSwitch);
-    ok &= setFrequencyTracingEnable(g_traceFrequency);
-    ok &= setCpuIdleTracingEnable(g_traceCpuIdle);
-    ok &= setGovernorLoadTracingEnable(g_traceGovernorLoad);
-    ok &= setTraceBufferSizeKB(g_traceBufferSizeKB);
-    ok &= setGlobalClockEnable(true);
-
-    // Set up the tracing options that do require root.  The options that
-    // require root should have errored out earlier if we're not running as
-    // root.
-    if (isRoot) {
-        ok &= setBusUtilizationTracingEnable(g_traceBusUtilization);
-        ok &= setSyncTracingEnabled(g_traceSync);
-        ok &= setWorkqueueTracingEnabled(g_traceWorkqueue);
-        ok &= setDiskTracingEnabled(g_traceDisk);
-    }
-
-    // Enable tracing.
-    ok &= setTracingEnabled(true);
-
-    if (!ok) {
-        fprintf(stderr, "error: unable to start trace\n");
-    }
-
-    return ok;
-}
-
-// Disable tracing in the kernel.
-static void stopTrace(bool isRoot)
-{
-    // Disable tracing.
-    setTracingEnabled(false);
-
-    // Set the options back to their defaults.
-    setTraceOverwriteEnable(true);
-    setSchedSwitchTracingEnable(false);
-    setFrequencyTracingEnable(false);
-    setGovernorLoadTracingEnable(false);
-    setGlobalClockEnable(false);
-
-    if (isRoot) {
-        setBusUtilizationTracingEnable(false);
-        setSyncTracingEnabled(false);
-        setWorkqueueTracingEnabled(false);
-        setDiskTracingEnabled(false);
-    }
-
-    // Note that we can't reset the trace buffer size here because that would
-    // clear the trace before we've read it.
-}
-
-// Read the current kernel trace and write it to stdout.
-static void dumpTrace()
-{
-    int traceFD = open(k_tracePath, O_RDWR);
-    if (traceFD == -1) {
-        fprintf(stderr, "error opening %s: %s (%d)\n", k_tracePath,
-                strerror(errno), errno);
-        return;
-    }
-
-    if (g_compress) {
-        z_stream zs;
-        uint8_t *in, *out;
-        int result, flush;
-
-        bzero(&zs, sizeof(zs));
-        result = deflateInit(&zs, Z_DEFAULT_COMPRESSION);
-        if (result != Z_OK) {
-            fprintf(stderr, "error initializing zlib: %d\n", result);
-            close(traceFD);
-            return;
-        }
-
-        const size_t bufSize = 64*1024;
-        in = (uint8_t*)malloc(bufSize);
-        out = (uint8_t*)malloc(bufSize);
-        flush = Z_NO_FLUSH;
-
-        zs.next_out = out;
-        zs.avail_out = bufSize;
-
-        do {
-
-            if (zs.avail_in == 0) {
-                // More input is needed.
-                result = read(traceFD, in, bufSize);
-                if (result < 0) {
-                    fprintf(stderr, "error reading trace: %s (%d)\n",
-                            strerror(errno), errno);
-                    result = Z_STREAM_END;
-                    break;
-                } else if (result == 0) {
-                    flush = Z_FINISH;
-                } else {
-                    zs.next_in = in;
-                    zs.avail_in = result;
-                }
-            }
-
-            if (zs.avail_out == 0) {
-                // Need to write the output.
-                result = write(STDOUT_FILENO, out, bufSize);
-                if ((size_t)result < bufSize) {
-                    fprintf(stderr, "error writing deflated trace: %s (%d)\n",
-                            strerror(errno), errno);
-                    result = Z_STREAM_END; // skip deflate error message
-                    zs.avail_out = bufSize; // skip the final write
-                    break;
-                }
-                zs.next_out = out;
-                zs.avail_out = bufSize;
-            }
-
-        } while ((result = deflate(&zs, flush)) == Z_OK);
-
-        if (result != Z_STREAM_END) {
-            fprintf(stderr, "error deflating trace: %s\n", zs.msg);
-        }
-
-        if (zs.avail_out < bufSize) {
-            size_t bytes = bufSize - zs.avail_out;
-            result = write(STDOUT_FILENO, out, bytes);
-            if ((size_t)result < bytes) {
-                fprintf(stderr, "error writing deflated trace: %s (%d)\n",
-                        strerror(errno), errno);
-            }
-        }
-
-        result = deflateEnd(&zs);
-        if (result != Z_OK) {
-            fprintf(stderr, "error cleaning up zlib: %d\n", result);
-        }
-
-        free(in);
-        free(out);
-    } else {
-        ssize_t sent = 0;
-        while ((sent = sendfile(STDOUT_FILENO, traceFD, NULL, 64*1024*1024)) > 0);
-        if (sent == -1) {
-            fprintf(stderr, "error dumping trace: %s (%d)\n", strerror(errno),
-                    errno);
-        }
-    }
-
-    close(traceFD);
-}
-
-// Print the command usage help to stderr.
-static void showHelp(const char *cmd)
-{
-    fprintf(stderr, "usage: %s [options]\n", cmd);
-    fprintf(stderr, "options include:\n"
-                    "  -b N            use a trace buffer size of N KB\n"
-                    "  -c              trace into a circular buffer\n"
-                    "  -d              trace disk I/O\n"
-                    "  -f              trace clock frequency changes\n"
-                    "  -l              trace CPU frequency governor load\n"
-                    "  -s              trace the kernel scheduler switches\n"
-                    "  -t N            trace for N seconds [defualt 5]\n"
-                    "  -u              trace bus utilization\n"
-                    "  -w              trace the kernel workqueue\n"
-                    "  -y              trace sync timelines and waits\n"
-                    "  -z              compress the trace dump\n"
-                    "  --async_start   start circular trace and return immediatly\n"
-                    "  --async_dump    dump the current contents of circular trace buffer\n"
-                    "  --async_stop    stop tracing and dump the current contents of circular\n"
-                    "                    trace buffer\n"
-            );
-}
-
-static void handleSignal(int signo) {
-    if (!g_nohup) {
-        g_traceAborted = true;
-    }
-}
-
-static void registerSigHandler() {
-    struct sigaction sa;
-    sigemptyset(&sa.sa_mask);
-    sa.sa_flags = 0;
-    sa.sa_handler = handleSignal;
-    sigaction(SIGHUP, &sa, NULL);
-    sigaction(SIGINT, &sa, NULL);
-    sigaction(SIGQUIT, &sa, NULL);
-    sigaction(SIGTERM, &sa, NULL);
-}
-
-int main(int argc, char **argv)
-{
-    bool isRoot = (getuid() == 0);
-    bool async = false;
-    bool traceStart = true;
-    bool traceStop = true;
-    bool traceDump = true;
-
-    if (argc == 2 && 0 == strcmp(argv[1], "--help")) {
-        showHelp(argv[0]);
-        exit(0);
-    }
-
-    for (;;) {
-        int ret;
-        int option_index = 0;
-        static struct option long_options[] = {
-            {"async_start",     no_argument, 0,  0 },
-            {"async_stop",      no_argument, 0,  0 },
-            {"async_dump",      no_argument, 0,  0 },
-            {0,         0,                 0,  0 }
-        };
-
-        ret = getopt_long(argc, argv, "b:cidflst:uwyznS:",
-                          long_options, &option_index);
-
-        if (ret < 0) {
-            break;
-        }
-
-        switch(ret) {
-            case 'b':
-                g_traceBufferSizeKB = atoi(optarg);
-            break;
-
-            case 'c':
-                g_traceOverwrite = true;
-            break;
-
-            case 'i':
-                g_traceCpuIdle = true;
-            break;
-
-            case 'l':
-                g_traceGovernorLoad = true;
-            break;
-
-            case 'd':
-                if (!isRoot) {
-                    fprintf(stderr, "error: tracing disk activity requires root privileges\n");
-                    exit(1);
-                }
-                g_traceDisk = true;
-            break;
-
-            case 'f':
-                g_traceFrequency = true;
-            break;
-
-            case 'n':
-                g_nohup = true;
-                break;
-
-            case 's':
-                g_traceSchedSwitch = true;
-            break;
-
-            case 'S':
-                g_initialSleepSecs = atoi(optarg);
-            break;
-
-            case 't':
-                g_traceDurationSeconds = atoi(optarg);
-            break;
-
-            case 'u':
-                if (!isRoot) {
-                    fprintf(stderr, "error: tracing bus utilization requires root privileges\n");
-                    exit(1);
-                }
-                g_traceBusUtilization = true;
-            break;
-
-            case 'w':
-                if (!isRoot) {
-                    fprintf(stderr, "error: tracing kernel work queues requires root privileges\n");
-                    exit(1);
-                }
-                g_traceWorkqueue = true;
-            break;
-
-            case 'y':
-                if (!isRoot) {
-                    fprintf(stderr, "error: tracing sync requires root privileges\n");
-                    exit(1);
-                }
-                g_traceSync = true;
-            break;
-
-            case 'z':
-                g_compress = true;
-            break;
-
-            case 0:
-                if (!strcmp(long_options[option_index].name, "async_start")) {
-                    async = true;
-                    traceStop = false;
-                    traceDump = false;
-                    g_traceOverwrite = true;
-                } else if (!strcmp(long_options[option_index].name, "async_stop")) {
-                    async = true;
-                    traceStop = false;
-                } else if (!strcmp(long_options[option_index].name, "async_dump")) {
-                    async = true;
-                    traceStart = false;
-                    traceStop = false;
-                }
-                break;
-
-            default:
-                fprintf(stderr, "\n");
-                showHelp(argv[0]);
-                exit(-1);
-            break;
-        }
-    }
-
-    registerSigHandler();
-
-    if (g_initialSleepSecs > 0) {
-        sleep(g_initialSleepSecs);
-    }
-
-    bool ok = startTrace(isRoot);
-
-    if (ok && traceStart) {
-        printf("capturing trace...");
-        fflush(stdout);
-
-        // We clear the trace after starting it because tracing gets enabled for
-        // each CPU individually in the kernel. Having the beginning of the trace
-        // contain entries from only one CPU can cause "begin" entries without a
-        // matching "end" entry to show up if a task gets migrated from one CPU to
-        // another.
-        ok = clearTrace();
-
-        if (ok && !async) {
-            // Sleep to allow the trace to be captured.
-            struct timespec timeLeft;
-            timeLeft.tv_sec = g_traceDurationSeconds;
-            timeLeft.tv_nsec = 0;
-            do {
-                if (g_traceAborted) {
-                    break;
-                }
-            } while (nanosleep(&timeLeft, &timeLeft) == -1 && errno == EINTR);
-        }
-    }
-
-    // Stop the trace and restore the default settings.
-    if (traceStop)
-        stopTrace(isRoot);
-
-    if (ok && traceDump) {
-        if (!g_traceAborted) {
-            printf(" done\nTRACE:\n");
-            fflush(stdout);
-            dumpTrace();
-        } else {
-            printf("\ntrace aborted.\n");
-            fflush(stdout);
-        }
-        clearTrace();
-    } else if (!ok) {
-        fprintf(stderr, "unable to start tracing\n");
-    }
-
-    // Reset the trace buffer size to 1.
-    if (traceStop)
-        setTraceBufferSizeKB(1);
-
-    return g_traceAborted ? 1 : 0;
-}
diff --git a/cmds/atrace/atrace.cpp b/cmds/atrace/atrace.cpp
new file mode 100644
index 0000000..a4bf674
--- /dev/null
+++ b/cmds/atrace/atrace.cpp
@@ -0,0 +1,711 @@
+/*
+ * Copyright (C) 2012 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <getopt.h>
+#include <signal.h>
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/sendfile.h>
+#include <time.h>
+#include <zlib.h>
+
+#include <binder/IBinder.h>
+#include <binder/IServiceManager.h>
+#include <binder/Parcel.h>
+
+#include <cutils/properties.h>
+
+#include <utils/String8.h>
+#include <utils/Trace.h>
+
+using namespace android;
+
+#define NELEM(x) ((int) (sizeof(x) / sizeof((x)[0])))
+
+enum { MAX_SYS_FILES = 8 };
+
+const char* k_traceTagsProperty = "debug.atrace.tags.enableflags";
+
+typedef enum { OPT, REQ } requiredness  ;
+
+struct TracingCategory {
+    // The name identifying the category.
+    const char* name;
+
+    // A longer description of the category.
+    const char* longname;
+
+    // The userland tracing tags that the category enables.
+    uint64_t tags;
+
+    // The fname==NULL terminated list of /sys/ files that the category
+    // enables.
+    struct {
+        // Whether the file must be writable in order to enable the tracing
+        // category.
+        requiredness required;
+
+        // The path to the enable file.
+        const char* path;
+    } sysfiles[MAX_SYS_FILES];
+};
+
+/* Tracing categories */
+static const TracingCategory k_categories[] = {
+    { "gfx",    "Graphics",         ATRACE_TAG_GRAPHICS, { } },
+    { "input",  "Input",            ATRACE_TAG_INPUT, { } },
+    { "view",   "View System",      ATRACE_TAG_VIEW, { } },
+    { "wm",     "Window Manager",   ATRACE_TAG_WINDOW_MANAGER, { } },
+    { "am",     "Activity Manager", ATRACE_TAG_ACTIVITY_MANAGER, { } },
+    { "audio",  "Audio",            ATRACE_TAG_AUDIO, { } },
+    { "video",  "Video",            ATRACE_TAG_VIDEO, { } },
+    { "camera", "Camera",           ATRACE_TAG_CAMERA, { } },
+    { "sched",  "CPU Scheduling",   0, {
+        { REQ,  "/sys/kernel/debug/tracing/events/sched/sched_switch/enable" },
+        { REQ,  "/sys/kernel/debug/tracing/events/sched/sched_wakeup/enable" },
+    } },
+    { "freq",   "CPU Frequency",    0, {
+        { REQ,  "/sys/kernel/debug/tracing/events/power/cpu_frequency/enable" },
+        { OPT, "/sys/kernel/debug/tracing/events/power/clock_set_rate/enable" },
+    } },
+    { "membus", "Memory Bus Utilization", 0, {
+        { REQ,  "/sys/kernel/debug/tracing/events/memory_bus/enable" },
+    } },
+    { "idle",   "CPU Idle",         0, {
+        { REQ,  "/sys/kernel/debug/tracing/events/power/cpu_idle/enable" },
+    } },
+    { "disk",   "Disk I/O",         0, {
+        { REQ,  "/sys/kernel/debug/tracing/events/ext4/ext4_sync_file_enter/enable" },
+        { REQ,  "/sys/kernel/debug/tracing/events/ext4/ext4_sync_file_exit/enable" },
+        { REQ,  "/sys/kernel/debug/tracing/events/block/block_rq_issue/enable" },
+        { REQ,  "/sys/kernel/debug/tracing/events/block/block_rq_complete/enable" },
+    } },
+    { "load",   "CPU Load",         0, {
+        { REQ,  "/sys/kernel/debug/tracing/events/cpufreq_interactive/enable" },
+    } },
+    { "sync",   "Synchronization",  0, {
+        { REQ,  "/sys/kernel/debug/tracing/events/sync/enable" },
+    } },
+    { "workq",  "Kernel Workqueues", 0, {
+        { REQ,  "/sys/kernel/debug/tracing/events/workqueue/enable" },
+    } },
+};
+
+/* Command line options */
+static int g_traceDurationSeconds = 5;
+static bool g_traceOverwrite = false;
+static int g_traceBufferSizeKB = 2048;
+static bool g_compress = false;
+static bool g_nohup = false;
+static int g_initialSleepSecs = 0;
+
+/* Global state */
+static bool g_traceAborted = false;
+static bool g_categoryEnables[NELEM(k_categories)] = {};
+
+/* Sys file paths */
+static const char* k_traceClockPath =
+    "/sys/kernel/debug/tracing/trace_clock";
+
+static const char* k_traceBufferSizePath =
+    "/sys/kernel/debug/tracing/buffer_size_kb";
+
+static const char* k_tracingOverwriteEnablePath =
+    "/sys/kernel/debug/tracing/options/overwrite";
+
+static const char* k_tracingOnPath =
+    "/sys/kernel/debug/tracing/tracing_on";
+
+static const char* k_tracePath =
+    "/sys/kernel/debug/tracing/trace";
+
+// Check whether a file exists.
+static bool fileExists(const char* filename) {
+    return access(filename, F_OK) != -1;
+}
+
+// Check whether a file is writable.
+static bool fileIsWritable(const char* filename) {
+    return access(filename, W_OK) != -1;
+}
+
+// Write a string to a file, returning true if the write was successful.
+static bool writeStr(const char* filename, const char* str)
+{
+    int fd = open(filename, O_WRONLY);
+    if (fd == -1) {
+        fprintf(stderr, "error opening %s: %s (%d)\n", filename,
+                strerror(errno), errno);
+        return false;
+    }
+
+    bool ok = true;
+    ssize_t len = strlen(str);
+    if (write(fd, str, len) != len) {
+        fprintf(stderr, "error writing to %s: %s (%d)\n", filename,
+                strerror(errno), errno);
+        ok = false;
+    }
+
+    close(fd);
+
+    return ok;
+}
+
+// Enable or disable a kernel option by writing a "1" or a "0" into a /sys
+// file.
+static bool setKernelOptionEnable(const char* filename, bool enable)
+{
+    return writeStr(filename, enable ? "1" : "0");
+}
+
+// Check whether the category is supported on the device with the current
+// rootness.  A category is supported only if all its required /sys/ files are
+// writable and if enabling the category will enable one or more tracing tags
+// or /sys/ files.
+static bool isCategorySupported(const TracingCategory& category)
+{
+    bool ok = category.tags != 0;
+    for (int i = 0; i < MAX_SYS_FILES; i++) {
+        const char* path = category.sysfiles[i].path;
+        bool req = category.sysfiles[i].required == REQ;
+        if (path != NULL) {
+            if (req) {
+                if (!fileIsWritable(path)) {
+                    return false;
+                } else {
+                    ok = true;
+                }
+            } else {
+                ok |= fileIsWritable(path);
+            }
+        }
+    }
+    return ok;
+}
+
+// Check whether the category would be supported on the device if the user
+// were root.  This function assumes that root is able to write to any file
+// that exists.  It performs the same logic as isCategorySupported, but it
+// uses file existance rather than writability in the /sys/ file checks.
+static bool isCategorySupportedForRoot(const TracingCategory& category)
+{
+    bool ok = category.tags != 0;
+    for (int i = 0; i < MAX_SYS_FILES; i++) {
+        const char* path = category.sysfiles[i].path;
+        bool req = category.sysfiles[i].required == REQ;
+        if (path != NULL) {
+            if (req) {
+                if (!fileExists(path)) {
+                    return false;
+                } else {
+                    ok = true;
+                }
+            } else {
+                ok |= fileExists(path);
+            }
+        }
+    }
+    return ok;
+}
+
+// Enable or disable overwriting of the kernel trace buffers.  Disabling this
+// will cause tracing to stop once the trace buffers have filled up.
+static bool setTraceOverwriteEnable(bool enable)
+{
+    return setKernelOptionEnable(k_tracingOverwriteEnablePath, enable);
+}
+
+// Enable or disable kernel tracing.
+static bool setTracingEnabled(bool enable)
+{
+    return setKernelOptionEnable(k_tracingOnPath, enable);
+}
+
+// Clear the contents of the kernel trace.
+static bool clearTrace()
+{
+    int traceFD = creat(k_tracePath, 0);
+    if (traceFD == -1) {
+        fprintf(stderr, "error truncating %s: %s (%d)\n", k_tracePath,
+                strerror(errno), errno);
+        return false;
+    }
+
+    close(traceFD);
+
+    return true;
+}
+
+// Set the size of the kernel's trace buffer in kilobytes.
+static bool setTraceBufferSizeKB(int size)
+{
+    char str[32] = "1";
+    int len;
+    if (size < 1) {
+        size = 1;
+    }
+    snprintf(str, 32, "%d", size);
+    return writeStr(k_traceBufferSizePath, str);
+}
+
+// Enable or disable the kernel's use of the global clock.  Disabling the global
+// clock will result in the kernel using a per-CPU local clock.
+static bool setGlobalClockEnable(bool enable)
+{
+    return writeStr(k_traceClockPath, enable ? "global" : "local");
+}
+
+// Poke all the binder-enabled processes in the system to get them to re-read
+// their system properties.
+static bool pokeBinderServices()
+{
+    sp<IServiceManager> sm = defaultServiceManager();
+    Vector<String16> services = sm->listServices();
+    for (size_t i = 0; i < services.size(); i++) {
+        sp<IBinder> obj = sm->checkService(services[i]);
+        if (obj != NULL) {
+            Parcel data;
+            if (obj->transact(IBinder::SYSPROPS_TRANSACTION, data,
+                    NULL, 0) != OK) {
+                if (false) {
+                    // XXX: For some reason this fails on tablets trying to
+                    // poke the "phone" service.  It's not clear whether some
+                    // are expected to fail.
+                    String8 svc(services[i]);
+                    fprintf(stderr, "error poking binder service %s\n",
+                        svc.string());
+                    return false;
+                }
+            }
+        }
+    }
+    return true;
+}
+
+// Set the trace tags that userland tracing uses, and poke the running
+// processes to pick up the new value.
+static bool setTagsProperty(uint64_t tags)
+{
+    char buf[64];
+    snprintf(buf, 64, "%#llx", tags);
+    if (property_set(k_traceTagsProperty, buf) < 0) {
+        fprintf(stderr, "error setting trace tags system property\n");
+        return false;
+    }
+    return pokeBinderServices();
+}
+
+// Disable all /sys/ enable files.
+static bool disableKernelTraceEvents() {
+    bool ok = true;
+    for (int i = 0; i < NELEM(k_categories); i++) {
+        const TracingCategory &c = k_categories[i];
+        for (int j = 0; j < MAX_SYS_FILES; j++) {
+            const char* path = c.sysfiles[j].path;
+            if (path != NULL && fileIsWritable(path)) {
+                ok &= setKernelOptionEnable(path, false);
+            }
+        }
+    }
+    return ok;
+}
+
+// Enable tracing in the kernel.
+static bool startTrace()
+{
+    bool ok = true;
+
+    // Set up the tracing options.
+    ok &= setTraceOverwriteEnable(g_traceOverwrite);
+    ok &= setTraceBufferSizeKB(g_traceBufferSizeKB);
+    ok &= setGlobalClockEnable(true);
+
+    // Set up the tags property.
+    uint64_t tags = 0;
+    for (int i = 0; i < NELEM(k_categories); i++) {
+        if (g_categoryEnables[i]) {
+            const TracingCategory &c = k_categories[i];
+            tags |= c.tags;
+        }
+    }
+    ok &= setTagsProperty(tags);
+
+    // Disable all the sysfs enables.  This is done as a separate loop from
+    // the enables to allow the same enable to exist in multiple categories.
+    ok &= disableKernelTraceEvents();
+
+    // Enable all the sysfs enables that are in an enabled category.
+    for (int i = 0; i < NELEM(k_categories); i++) {
+        if (g_categoryEnables[i]) {
+            const TracingCategory &c = k_categories[i];
+            for (int j = 0; j < MAX_SYS_FILES; j++) {
+                const char* path = c.sysfiles[j].path;
+                bool required = c.sysfiles[j].required == REQ;
+                if (path != NULL) {
+                    if (fileIsWritable(path)) {
+                        ok &= setKernelOptionEnable(path, true);
+                    } else if (required) {
+                        fprintf(stderr, "error writing file %s\n", path);
+                        ok = false;
+                    }
+                }
+            }
+        }
+    }
+
+    // Enable tracing.
+    ok &= setTracingEnabled(true);
+
+    return ok;
+}
+
+// Disable tracing in the kernel.
+static void stopTrace()
+{
+    // Disable tracing.
+    setTracingEnabled(false);
+
+    // Disable all tracing that we're able to.
+    disableKernelTraceEvents();
+
+    // Disable all the trace tags.
+    setTagsProperty(0);
+
+    // Set the options back to their defaults.
+    setTraceOverwriteEnable(true);
+    setGlobalClockEnable(false);
+
+    // Note that we can't reset the trace buffer size here because that would
+    // clear the trace before we've read it.
+}
+
+// Read the current kernel trace and write it to stdout.
+static void dumpTrace()
+{
+    int traceFD = open(k_tracePath, O_RDWR);
+    if (traceFD == -1) {
+        fprintf(stderr, "error opening %s: %s (%d)\n", k_tracePath,
+                strerror(errno), errno);
+        return;
+    }
+
+    if (g_compress) {
+        z_stream zs;
+        uint8_t *in, *out;
+        int result, flush;
+
+        bzero(&zs, sizeof(zs));
+        result = deflateInit(&zs, Z_DEFAULT_COMPRESSION);
+        if (result != Z_OK) {
+            fprintf(stderr, "error initializing zlib: %d\n", result);
+            close(traceFD);
+            return;
+        }
+
+        const size_t bufSize = 64*1024;
+        in = (uint8_t*)malloc(bufSize);
+        out = (uint8_t*)malloc(bufSize);
+        flush = Z_NO_FLUSH;
+
+        zs.next_out = out;
+        zs.avail_out = bufSize;
+
+        do {
+
+            if (zs.avail_in == 0) {
+                // More input is needed.
+                result = read(traceFD, in, bufSize);
+                if (result < 0) {
+                    fprintf(stderr, "error reading trace: %s (%d)\n",
+                            strerror(errno), errno);
+                    result = Z_STREAM_END;
+                    break;
+                } else if (result == 0) {
+                    flush = Z_FINISH;
+                } else {
+                    zs.next_in = in;
+                    zs.avail_in = result;
+                }
+            }
+
+            if (zs.avail_out == 0) {
+                // Need to write the output.
+                result = write(STDOUT_FILENO, out, bufSize);
+                if ((size_t)result < bufSize) {
+                    fprintf(stderr, "error writing deflated trace: %s (%d)\n",
+                            strerror(errno), errno);
+                    result = Z_STREAM_END; // skip deflate error message
+                    zs.avail_out = bufSize; // skip the final write
+                    break;
+                }
+                zs.next_out = out;
+                zs.avail_out = bufSize;
+            }
+
+        } while ((result = deflate(&zs, flush)) == Z_OK);
+
+        if (result != Z_STREAM_END) {
+            fprintf(stderr, "error deflating trace: %s\n", zs.msg);
+        }
+
+        if (zs.avail_out < bufSize) {
+            size_t bytes = bufSize - zs.avail_out;
+            result = write(STDOUT_FILENO, out, bytes);
+            if ((size_t)result < bytes) {
+                fprintf(stderr, "error writing deflated trace: %s (%d)\n",
+                        strerror(errno), errno);
+            }
+        }
+
+        result = deflateEnd(&zs);
+        if (result != Z_OK) {
+            fprintf(stderr, "error cleaning up zlib: %d\n", result);
+        }
+
+        free(in);
+        free(out);
+    } else {
+        ssize_t sent = 0;
+        while ((sent = sendfile(STDOUT_FILENO, traceFD, NULL, 64*1024*1024)) > 0);
+        if (sent == -1) {
+            fprintf(stderr, "error dumping trace: %s (%d)\n", strerror(errno),
+                    errno);
+        }
+    }
+
+    close(traceFD);
+}
+
+static void handleSignal(int signo)
+{
+    if (!g_nohup) {
+        g_traceAborted = true;
+    }
+}
+
+static void registerSigHandler()
+{
+    struct sigaction sa;
+    sigemptyset(&sa.sa_mask);
+    sa.sa_flags = 0;
+    sa.sa_handler = handleSignal;
+    sigaction(SIGHUP, &sa, NULL);
+    sigaction(SIGINT, &sa, NULL);
+    sigaction(SIGQUIT, &sa, NULL);
+    sigaction(SIGTERM, &sa, NULL);
+}
+
+static bool setCategoryEnable(const char* name, bool enable)
+{
+    for (int i = 0; i < NELEM(k_categories); i++) {
+        const TracingCategory& c = k_categories[i];
+        if (strcmp(name, c.name) == 0) {
+            if (isCategorySupported(c)) {
+                g_categoryEnables[i] = enable;
+                return true;
+            } else {
+                if (isCategorySupportedForRoot(c)) {
+                    fprintf(stderr, "error: category \"%s\" requires root "
+                            "privileges.\n", name);
+                } else {
+                    fprintf(stderr, "error: category \"%s\" is not supported "
+                            "on this device.\n", name);
+                }
+                return false;
+            }
+        }
+    }
+    fprintf(stderr, "error: unknown tracing category \"%s\"\n", name);
+    return false;
+}
+
+static void listSupportedCategories()
+{
+    for (int i = 0; i < NELEM(k_categories); i++) {
+        const TracingCategory& c = k_categories[i];
+        if (isCategorySupported(c)) {
+            printf("  %10s - %s\n", c.name, c.longname);
+        }
+    }
+}
+
+// Print the command usage help to stderr.
+static void showHelp(const char *cmd)
+{
+    fprintf(stderr, "usage: %s [options] [categories...]\n", cmd);
+    fprintf(stderr, "options include:\n"
+                    "  -b N            use a trace buffer size of N KB\n"
+                    "  -c              trace into a circular buffer\n"
+                    "  -n              ignore signals\n"
+                    "  -s N            sleep for N seconds before tracing [default 0]\n"
+                    "  -t N            trace for N seconds [defualt 5]\n"
+                    "  -z              compress the trace dump\n"
+                    "  --async_start   start circular trace and return immediatly\n"
+                    "  --async_dump    dump the current contents of circular trace buffer\n"
+                    "  --async_stop    stop tracing and dump the current contents of circular\n"
+                    "                    trace buffer\n"
+            );
+}
+
+int main(int argc, char **argv)
+{
+    bool async = false;
+    bool traceStart = true;
+    bool traceStop = true;
+    bool traceDump = true;
+
+    if (argc == 2 && 0 == strcmp(argv[1], "--help")) {
+        showHelp(argv[0]);
+        exit(0);
+    }
+
+    for (;;) {
+        int ret;
+        int option_index = 0;
+        static struct option long_options[] = {
+            {"async_start",     no_argument, 0,  0 },
+            {"async_stop",      no_argument, 0,  0 },
+            {"async_dump",      no_argument, 0,  0 },
+            {"list_categories", no_argument, 0,  0 },
+            {           0,                0, 0,  0 }
+        };
+
+        ret = getopt_long(argc, argv, "b:cns:t:z",
+                          long_options, &option_index);
+
+        if (ret < 0) {
+            for (int i = optind; i < argc; i++) {
+                if (!setCategoryEnable(argv[i], true)) {
+                    fprintf(stderr, "error enabling tracing category \"%s\"\n", argv[i]);
+                    exit(1);
+                }
+            }
+            break;
+        }
+
+        switch(ret) {
+            case 'b':
+                g_traceBufferSizeKB = atoi(optarg);
+            break;
+
+            case 'c':
+                g_traceOverwrite = true;
+            break;
+
+            case 'n':
+                g_nohup = true;
+                break;
+
+            case 's':
+                g_initialSleepSecs = atoi(optarg);
+            break;
+
+            case 't':
+                g_traceDurationSeconds = atoi(optarg);
+            break;
+
+            case 'z':
+                g_compress = true;
+            break;
+
+            case 0:
+                if (!strcmp(long_options[option_index].name, "async_start")) {
+                    async = true;
+                    traceStop = false;
+                    traceDump = false;
+                    g_traceOverwrite = true;
+                } else if (!strcmp(long_options[option_index].name, "async_stop")) {
+                    async = true;
+                    traceStop = false;
+                } else if (!strcmp(long_options[option_index].name, "async_dump")) {
+                    async = true;
+                    traceStart = false;
+                    traceStop = false;
+                } else if (!strcmp(long_options[option_index].name, "list_categories")) {
+                    listSupportedCategories();
+                    exit(0);
+                }
+                break;
+
+            default:
+                fprintf(stderr, "\n");
+                showHelp(argv[0]);
+                exit(-1);
+            break;
+        }
+    }
+
+    registerSigHandler();
+
+    if (g_initialSleepSecs > 0) {
+        sleep(g_initialSleepSecs);
+    }
+
+    bool ok = startTrace();
+
+    if (ok && traceStart) {
+        printf("capturing trace...");
+        fflush(stdout);
+
+        // We clear the trace after starting it because tracing gets enabled for
+        // each CPU individually in the kernel. Having the beginning of the trace
+        // contain entries from only one CPU can cause "begin" entries without a
+        // matching "end" entry to show up if a task gets migrated from one CPU to
+        // another.
+        ok = clearTrace();
+
+        if (ok && !async) {
+            // Sleep to allow the trace to be captured.
+            struct timespec timeLeft;
+            timeLeft.tv_sec = g_traceDurationSeconds;
+            timeLeft.tv_nsec = 0;
+            do {
+                if (g_traceAborted) {
+                    break;
+                }
+            } while (nanosleep(&timeLeft, &timeLeft) == -1 && errno == EINTR);
+        }
+    }
+
+    // Stop the trace and restore the default settings.
+    if (traceStop)
+        stopTrace();
+
+    if (ok && traceDump) {
+        if (!g_traceAborted) {
+            printf(" done\nTRACE:\n");
+            fflush(stdout);
+            dumpTrace();
+        } else {
+            printf("\ntrace aborted.\n");
+            fflush(stdout);
+        }
+        clearTrace();
+    } else if (!ok) {
+        fprintf(stderr, "unable to start tracing\n");
+    }
+
+    // Reset the trace buffer size to 1.
+    if (traceStop)
+        setTraceBufferSizeKB(1);
+
+    return g_traceAborted ? 1 : 0;
+}