page.title=Debugging Native Android Platform Code @jd:body

In this document

This page contains a summary of useful tools and related commands for debugging, tracing, and profiling native Android platform code. The pages within this section contain detailed information on other debugging tools for use during development of platform-level features.

For example, you may learn how to explore system services with Dumpsys and evaluate network and RAM use. See the subpages for tools and methods not described below.

debuggerd

When a dynamically-linked executable starts, several signal handlers are registered that connect to debuggerd (or debuggerd64) in the event that signal is sent to the process. The debuggerd process dumps registers and unwinds the stack. Here is example output (with timestamps and extraneous information removed):

*** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
Build fingerprint: 'Android/aosp_flounder/flounder:5.1.51/AOSP/enh08201009:eng/test-keys'
Revision: '0'
ABI: 'arm'
pid: 1656, tid: 1656, name: crasher  >>> crasher <<<
signal 6 (SIGABRT), code -6 (SI_TKILL), fault addr --------
Abort message: 'some_file.c:123: some_function: assertion "false" failed'
    r0 00000000  r1 00000678  r2 00000006  r3 f70b6dc8
    r4 f70b6dd0  r5 f70b6d80  r6 00000002  r7 0000010c
    r8 ffffffed  r9 00000000  sl 00000000  fp ff96ae1c
    ip 00000006  sp ff96ad18  lr f700ced5  pc f700dc98  cpsr 400b0010
backtrace:
    #00 pc 00042c98  /system/lib/libc.so (tgkill+12)
    #01 pc 00041ed1  /system/lib/libc.so (pthread_kill+32)
    #02 pc 0001bb87  /system/lib/libc.so (raise+10)
    #03 pc 00018cad  /system/lib/libc.so (__libc_android_abort+34)
    #04 pc 000168e8  /system/lib/libc.so (abort+4)
    #05 pc 0001a78f  /system/lib/libc.so (__libc_fatal+16)
    #06 pc 00018d35  /system/lib/libc.so (__assert2+20)
    #07 pc 00000f21  /system/xbin/crasher
    #08 pc 00016795  /system/lib/libc.so (__libc_init+44)
    #09 pc 00000abc  /system/xbin/crasher
Tombstone written to: /data/tombstones/tombstone_06

This can be pasted into development/scripts/stack to get a more detailed unwind with line number information (assuming the unstripped binaries can be found).

Some libraries on the system are built with LOCAL_STRIP_MODULE := keep_symbols to provide usable backtraces directly from debuggerd. This makes your library or executable slightly larger, but not nearly as large as an unstripped version.

Note also the last line of debuggerd output --- in addition to dumping a summary to the log, debuggerd writes a full “tombstone” to disk. This contains a lot of extra information that can be helpful in debugging a crash, in particular the stack traces for all the threads in the crashing process (not just the thread that caught the signal) and a full memory map.

Native Debugging with GDB

Debugging a running app

To connect to an already-running app or native daemon, use gdbclient.

Current versions of gdbclient just require the process ID (PID). So to debug a process with PID 1234, simply run:

$ gdbclient 1234

The script will set up port forwarding, start the appropriate gdbserver on the device, start the appropriate gdb on the host, configure gdb to find symbols, and connect gdb to the remote gdbserver.

Debugging a native process as it starts

If you want to debug a process as it starts, you’ll need to use gdbserver manually, but that’s easy too:

$ adb shell gdbserver :5039 /system/bin/my_test_app
Process my_test_app created; pid = 3460
Listening on port 5039

Identify the app’s PID from the gdbserver output, and then in another window:

$ gdbclient <app pid>

Then enter continue at the gdb prompt.

Debugging processes that crash

If you want debuggerd to suspend crashed processes so you can attach gdb, set the appropriate property:

$ adb shell setprop debug.db.uid 999999                 # <= M
$ adb shell setprop debug.debuggerd.wait_for_gdb true   # > M

At the end of the usual crash output, debuggerd will give you instructions on how to connect gdb using the typical command:

$ gdbclient <pid>

Debugging without symbols

If you don’t have symbols, sometimes gdb will get confused about the instruction set it is disassembling (ARM or Thumb). The instruction set that is chosen as the default when symbol information is missing can be switched between ARM or Thumb like so:

$ set arm fallback-mode arm   # or 'thumb'

Other tools

Valgrind

The following steps show you how to use Valgrind on Android. This tool suite contains a number of tools including Memcheck for detecting memory-related errors in C and C++.

To install Valgrind, run:
```
$ mmm -j6 external/valgrind
```
Push Valgrind to the device:
```
$ adb remount
$ adb sync
```

Set up the temporary directory:

$ adb shell mkdir /data/local/tmp
$ adb shell chmod 777 /data/local/tmp

Run the system server with Valgrind:

$ adb root
$ adb shell setprop wrap.system_server "logwrapper valgrind"
$ adb shell stop && adb shell start

For debug symbols, push unstripped libraries to /data/local/symbols:

$ adb shell mkdir /data/local/symbols
$ adb push $OUT/symbols /data/local/symbols

To use Valgrind during boot up, edit out/target/product/XXXX/root/init.rc and change:
service example /system/bin/foo --arg1 --arg2
to:
service example /system/bin/logwrapper /system/bin/valgrind /system/bin/foo --arg1 --arg2
To see the effects, you need to create a boot.img and reflash the device.

Systrace

See Systrace on developer.android.com for deriving execution times of applications and other Android system processes.