Tuesday, August 30, 2011

ease android stacktrace examination in vim with agdb

Continue the post view call stack of crashed application on android.
The agdb tool is able to convert PC register to source file information, but not convenient enough. After agdb outputs source file information, we still need to open the source file in vim and jump to the corresponding line manually.
Now agdb tool can generate a vim specific error file for the stacktrace to help us jump to source code directly.
Still consider the stacktrace below:


22 F/ASessionDescription(   33): frameworks/base/media/libstagefright/rtsp/ASessionDescription.cpp:264 CHECK_GT( end,s) failed:  vs.
23 I/DEBUG   (   30): *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
24 I/DEBUG   (   30): Build fingerprint: 'generic/generic/generic:2.3.1/GINGERBREAD/eng.raymond.20101222.130550:eng/test-keys'
25 I/DEBUG   (   30): pid: 33, tid: 450  >>> /system/bin/mediaserver <<<
26 I/DEBUG   (   30): signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr deadbaad
27 I/DEBUG   (   30):  r0 deadbaad  r1 0000000c  r2 00000027  r3 00000000
28 I/DEBUG   (   30):  r4 00000080  r5 afd46668  r6 40806c10  r7 00000000
29 I/DEBUG   (   30):  r8 8031db1d  r9 0000fae0  10 00100000  fp 00000001
30 I/DEBUG   (   30):  ip ffffffff  sp 40806778  lr afd19375  pc afd15ef0  cpsr 00000030
31 I/DEBUG   (   30):          #00  pc 00015ef0  /system/lib/libc.so
32 I/DEBUG   (   30):          #01  pc 00001440  /system/lib/liblog.so
33 I/DEBUG   (   30):
34 I/DEBUG   (   30): code around pc:
35 I/DEBUG   (   30): afd15ed0 68241c23 d1fb2c00 68dae027 d0042a00
36 I/DEBUG   (   30): afd15ee0 20014d18 6028447d 48174790 24802227
37 I/DEBUG   (   30): afd15ef0 f7f57002 2106eb56 ec92f7f6 0563aa01
38 I/DEBUG   (   30): afd15f00 60932100 91016051 1c112006 e818f7f6
39 I/DEBUG   (   30): afd15f10 2200a905 f7f62002 f7f5e824 2106eb42
40 I/DEBUG   (   30):
41 I/DEBUG   (   30): code around lr:
42 I/DEBUG   (   30): afd19354 b0834a0d 589c447b 26009001 686768a5
43 I/DEBUG   (   30): afd19364 220ce008 2b005eab 1c28d003 47889901
44 I/DEBUG   (   30): afd19374 35544306 d5f43f01 2c006824 b003d1ee
45 I/DEBUG   (   30): afd19384 bdf01c30 000281a8 ffffff88 1c0fb5f0
46 I/DEBUG   (   30): afd19394 43551c3d a904b087 1c16ac01 604d9004
47 I/DEBUG   (   30):
48 I/DEBUG   (   30): stack:
49 ........................
92 I/DEBUG   (   30):     408067e4  6f697470
93 I/BootReceiver(   75): Copying /data/tombstones/tombstone_09 to DropBox (SYSTEM_TOMBSTONE)

We run this command to convert it to vim error file:
agdb.py -v < tombstone_01.txt > vim_error_file
# the -v argument tells agdb to generate a vim error file

Then in vim, we run :cg vim_error_file to load the error file to vim's quickfix buffer.
After the error file is loaded, we run :cw command in vim to examine the call stack. It's shown below:

1 pid: 33, tid: 450  >>> /system/bin/mediaserver <<<
2 /path_to_android_src_root/bionic/libc/unistd/abort.c:82: #00 __libc_android_abort
3 /path_to_android_src_root/system/core/liblog/logd_write.c:235: #01 __android_log_assert
Now we can focus on the line that we'd like to further investigate, and press enter. Vim will bring us the the exact line that the error corresponds to.

The idea of the feature is very simple. As we vim users know, vim is able to recognize lots of compilers' error message. The agdb tool converts the format of stacktrace to gcc compiler's error format, then vim can load the output to quickfix and associate lines with corresponding source code.

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