1page.title=Debugging Native Android Platform Code 2@jd:body 3 4<!-- 5 Copyright 2015 The Android Open Source Project 6 7 Licensed under the Apache License, Version 2.0 (the "License"); 8 you may not use this file except in compliance with the License. 9 You may obtain a copy of the License at 10 11 http://www.apache.org/licenses/LICENSE-2.0 12 13 Unless required by applicable law or agreed to in writing, software 14 distributed under the License is distributed on an "AS IS" BASIS, 15 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 16 See the License for the specific language governing permissions and 17 limitations under the License. 18--> 19<div id="qv-wrapper"> 20 <div id="qv"> 21 <h2>In this document</h2> 22 <ol id="auto-toc"></ol> 23 </div> 24</div> 25 26<p>This page contains a summary of useful tools and related commands for 27debugging, tracing, and profiling native Android platform code. The pages 28within this section contain detailed information on other debugging tools for 29use during development of platform-level features.</p> 30 31<p>For example, you may learn how to explore system services with <a 32href="dumpsys.html">Dumpsys</a> and evaluate <a 33href="netstats.html">network</a> and <a href="procstats.html">RAM</a> use. See 34the subpages for tools and methods not described below.</p> 35 36<h2 id=debuggerd>debuggerd</h2> 37 38<p>The <code>debuggerd</code> process dumps registers and unwinds the 39stack. When a dynamically-linked executable starts, several signal handlers are 40registered that connect to <code>debuggerd</code> (or <code>debuggerd64)</code> in the event that signal 41is sent to the process.</p> 42 43<p>It's possible for <code>debuggerd</code> to attach only if nothing else is 44already attached. This means that using tools like <code>strace</code> or 45<code>gdb</code> will prevent <code>debuggerd</code> from working. Also, if 46you call <code>prctl(PR_SET_DUMPABLE, 0)</code> you can prevent 47<code>debuggerd</code> from attaching. This can be useful if you wish to 48explicitly opt out of crash reporting.</p> 49 50<p>Here is example output (with timestamps and extraneous information removed):</p> 51 52<pre class="no-pretty-print"> 53*** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** 54Build fingerprint: 'Android/aosp_flounder/flounder:5.1.51/AOSP/enh08201009:eng/test-keys' 55Revision: '0' 56ABI: 'arm' 57pid: 1656, tid: 1656, name: crasher >>> crasher <<< 58signal 6 (SIGABRT), code -6 (SI_TKILL), fault addr -------- 59Abort message: 'some_file.c:123: some_function: assertion "false" failed' 60 r0 00000000 r1 00000678 r2 00000006 r3 f70b6dc8 61 r4 f70b6dd0 r5 f70b6d80 r6 00000002 r7 0000010c 62 r8 ffffffed r9 00000000 sl 00000000 fp ff96ae1c 63 ip 00000006 sp ff96ad18 lr f700ced5 pc f700dc98 cpsr 400b0010 64backtrace: 65 #00 pc 00042c98 /system/lib/libc.so (tgkill+12) 66 #01 pc 00041ed1 /system/lib/libc.so (pthread_kill+32) 67 #02 pc 0001bb87 /system/lib/libc.so (raise+10) 68 #03 pc 00018cad /system/lib/libc.so (__libc_android_abort+34) 69 #04 pc 000168e8 /system/lib/libc.so (abort+4) 70 #05 pc 0001a78f /system/lib/libc.so (__libc_fatal+16) 71 #06 pc 00018d35 /system/lib/libc.so (__assert2+20) 72 #07 pc 00000f21 /system/xbin/crasher 73 #08 pc 00016795 /system/lib/libc.so (__libc_init+44) 74 #09 pc 00000abc /system/xbin/crasher 75Tombstone written to: /data/tombstones/tombstone_06 76</pre> 77 78<p>This can be pasted into <code>development/scripts/stack</code> to get a more detailed unwind 79with line number information (assuming the unstripped binaries can be found).</p> 80 81<p>Some libraries on the system are built with <code>LOCAL_STRIP_MODULE := 82keep_symbols</code> to provide usable backtraces directly from <code>debuggerd</code>. This makes 83your library or executable slightly larger, but not nearly as large as an 84unstripped version.</p> 85 86<p>Note also the last line of <code>debuggerd</code> output --- in addition to dumping a 87summary to the log, <code>debuggerd</code> writes a full “tombstone” to disk. This contains 88a lot of extra information that can be helpful in debugging a crash, in 89particular the stack traces for all the threads in the crashing process (not 90just the thread that caught the signal) and a full memory map.</p> 91 92<p>For more information about diagnosing native crashes and tombstones, see 93<a href="{@docRoot}devices/tech/debug/native-crash.html">Diagnosing Native Crashes</a></p> 94 95<h2 id=native>Native Debugging with GDB</h2> 96 97<h3 id=running>Debugging a running app</h3> 98 99<p>To connect to an already-running app or native daemon, use <code>gdbclient</code>.</p> 100 101<p>Current versions of gdbclient just require the process ID (PID). So to debug a process with 102PID 1234, simply run:</p> 103<pre class="no-pretty-print"> 104$ gdbclient 1234 105</pre> 106<p>The script will set up port forwarding, start the appropriate 107<code>gdbserver</code> on the device, start the appropriate <code>gdb</code> on 108the host, configure <code>gdb</code> to find symbols, and connect 109<code>gdb</code> to the remote <code>gdbserver</code>.</p> 110 111<h3 id=starts>Debugging a native process as it starts</h3> 112 113<p>If you want to debug a process as it starts, you’ll need to use <code>gdbserver</code> 114or <code>gdbserver64</code> manually, but that’s easy too:</p> 115 116<pre class="no-pretty-print"> 117$ adb shell gdbserver :5039 /system/bin/<em>my_test_app</em> 118Process my_test_app created; pid = 3460 119Listening on port 5039 120</pre> 121 122<p>Identify the app’s PID from the <code>gdbserver</code> output, and then in 123another window:</p> 124 125<pre class="no-pretty-print"> 126$ gdbclient <em><app pid></em> 127</pre> 128 129<p>Then enter <strong>continue</strong> at the <code>gdb</code> prompt.</p> 130 131<p>Note that to debug a 64-bit process, you'll need to use <code>gdbserver64</code>. 132The error messages from <code>gdb</code> if you made the wrong choice are unhelpful 133(along the lines of <code>Reply contains invalid hex digit 59</code>).</p> 134 135<h3 id=crash>Debugging processes that crash</h3> 136 137<p>If you want <code>debuggerd</code> to suspend crashed processes so you can 138attach <code>gdb</code>, set the appropriate property:</p> 139 140<pre class="no-pretty-print"> 141$ adb shell setprop debug.db.uid 999999 # <= M 142$ adb shell setprop debug.debuggerd.wait_for_gdb true # > M 143</pre> 144 145<p>At the end of the usual crash output, <code>debuggerd</code> will give you 146instructions on how to connect <code>gdb</code> using the typical command: 147<pre class="no-pretty-print"> 148$ gdbclient <pid> 149</pre> 150 151<h3 id=symbols>Debugging without symbols</h3> 152 153<p>If you don’t have symbols, sometimes <code>gdb</code> will get confused about the 154instruction set it is disassembling (ARM or Thumb). The instruction set that is 155chosen as the default when symbol information is missing can be switched 156between ARM or Thumb like so:</p> 157 158<pre class="no-pretty-print"> 159$ set arm fallback-mode arm # or 'thumb' 160</pre> 161 162<h2 id=symbols>Other tools</h2> 163 164<h3 id=valgrind>Valgrind</h3> 165 166<p>The following steps show you how to use <a 167href="http://valgrind.org/">Valgrind</a> on Android. This tool suite contains a 168number of tools including Memcheck for detecting memory-related errors in C and 169C++.</p> 170 171<p>Android platform developers usually use 172<a href="{@docRoot}devices/tech/debug/asan.html">AddressSanitizer (ASan)</a> rather than valgrind.</p> 173 174<ol> 175 <li>To build Valgrind, run: 176<pre class="no-pretty-print"> 177$ mmma -j6 external/valgrind 178</pre> 179 <li>Set up the temporary directory: 180<pre class="no-pretty-print"> 181$ adb shell mkdir /data/local/tmp 182$ adb shell chmod 777 /data/local/tmp 183</pre> 184 <li>Run the system server with Valgrind: 185<pre class="no-pretty-print"> 186$ adb shell setprop wrap.system_server "logwrapper valgrind" 187$ adb shell stop && adb shell start 188</pre> 189 <li>For debug symbols, push unstripped libraries to <code>/data/local/symbols</code>: 190<pre class="no-pretty-print"> 191$ adb shell mkdir /data/local/symbols 192$ adb push $OUT/symbols /data/local/symbols 193</pre> 194 <li>To use Valgrind during boot up, edit <code>out/target/product/XXXX/root/init.rc</code> and 195change:<br> 196<code>service example /system/bin/foo --arg1 --arg2</code><br> 197to:<br> 198<code>service example /system/bin/logwrapper /system/bin/valgrind /system/bin/foo --arg1 --arg2</code><br> 199To see the effects, you need to create a <code>boot.img</code> and reflash the device. 200</ol> 201 202<h3 id=systrace>Systrace</h3> 203 204<p>See <a 205href="https://developer.android.com/tools/help/systrace.html">Systrace on 206developer.android.com</a> for deriving execution times of applications and 207other Android system processes.</p> 208