ちょこっとGDB

gdbを使って、起動済みプロセスのデバッグを行う

$ gdb
GNU gdb Red Hat Linux (6.5-37.el5_2.2rh)
Copyright (C) 2006 Free Software Foundation, Inc.
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Type "show copying" to see the conditions.
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This GDB was configured as "i386-redhat-linux-gnu".
(gdb) dir GUI/bin/cgisessiond/ <==== 参照するソースのパスを登録 Tab補完できる
Source directories searched: /home/crk/hogehoge/GUI/bin/cgisessiond:$cdir:$cwd
(gdb) dir GUI/cgi/partition/remote_kvms_cr_setup/
Source directories searched: /home/crk/hogehoge/GUI/cgi/partition/remote_kvms_cr_setup:/home/crk/hogehoge/GUI/bin/cgisessiond:$cdir:$cwd
(gdb) dir lib/Setup/bin/
Source directories searched: /home/crk/hogehoge/lib/Setup/bin:/home/crk/hogehoge/GUI/cgi/partition/remote_kvms_cr_setup:/home/crk/hogehoge/GUI/bin/cgisessiond:$cdir:$cwd
(gdb) attach 20116 <==== デバッグするプロセスIDをattach
Attaching to process 20116
Reading symbols from /home/crk/hogehoge/GUI/bin/cgisessiond/cgisessiond...done.
Using host libthread_db library "/lib/libthread_db.so.1".
Reading symbols from /home/crk/hogehoge/lib/libdummy_ipmiclient.so.1...done.
Loaded symbols for /home/crk/hogehoge/lib/libdummy_ipmiclient.so.1
Reading symbols from /lib/libpam.so.0...done.
Loaded symbols for /lib/libpam.so.0
Reading symbols from /home/crk/hogehoge/lib/libschedule.so.1...done.
Loaded symbols for /home/crk/hogehoge/lib/libschedule.so.1
Reading symbols from /lib/libpthread.so.0...done.
[Thread debugging using libthread_db enabled]
[New Thread -1208051296 (LWP 20116)]
[New Thread 129751952 (LWP 20143)]
[New Thread 79842192 (LWP 20136)]
[New Thread 104491920 (LWP 20124)]
[New Thread 69352336 (LWP 20121)]
[New Thread 47803280 (LWP 20120)]
[New Thread 37313424 (LWP 20119)]
[New Thread 58862480 (LWP 20118)]
[New Thread 26823568 (LWP 20117)]
Loaded symbols for /lib/libpthread.so.0
Reading symbols from /home/crk/hogehoge/lib/libmmbcommon.so.1...done.
Loaded symbols for /home/crk/hogehoge/lib/libmmbcommon.so.1
　　　：
Reading symbols from /lib/librt.so.1...done.
Loaded symbols for /lib/librt.so.1
Reading symbols from /lib/libnsl.so.1...done.
Loaded symbols for /lib/libnsl.so.1
0x0084d402 in __kernel_vsyscall ()
(gdb) b RemoteKVMSCRSetupPage.cpp:382 <==== RemoteKVMSCRSetupPage.cppの382行目にブレークポイント設定
No source file named RemoteKVMSCRSetupPage.cpp. <==== でもこれってCGI側だから、このプロセスでは参照不可なのさ
Make breakpoint pending on future shared library load? (y or [n]) y
Breakpoint 1 (RemoteKVMSCRSetupPage.cpp:382) pending.
(gdb) b TrSetRemoteKVMSConfigData.cpp:41 <==== TrSetRemoteKVMSConfigData.cppの41行目にブレークポイント設定
Breakpoint 2 at 0x80d742f: file TrSetRemoteKVMSConfigData.cpp, line 41.
(gdb) i b <==== ブレークポイントの一覧
Num Type Disp Enb Address What
1 breakpoint keep y RemoteKVMSCRSetupPage.cpp:382
2 breakpoint keep y 0x080d742f in TrSetRemoteKVMSConfigData::execute() at TrSetRemoteKVMSConfigData.cpp:41
(gdb) del 1 <==== ブレークポイントの削除
(gdb) c <==== continueの指示
Continuing.
Breakpoint 2, TrSetRemoteKVMSConfigData::execute (this=0xb7c00468) at TrSetRemoteKVMSConfigData.cpp:42
42 if (!recieveData(&rcvInfo)) {
(gdb) next <==== 次の行へ。以降はリターンすると直前のコマンドの繰り返し
49 PrimitiveTypeWrapper() {}
(gdb) <==== なのでここはリターンのみ
53 if (!packet.setSerialized(rcvInfo, getReqDataLength())) {
(gdb)
135 if (size > sizeof(PRIMITIVE_TYPE)) {
(gdb)
138 memcpy(&data, inData, sizeof(PRIMITIVE_TYPE));
(gdb)
149 return data;
(gdb)
64 reqData = packet.getData();
(gdb)
67 RemoteKVMSConfigData::setRemoteKVMSConfigData( &reqData );
(gdb) p reqData <==== 変数の内容を表示　昔に比べて賢くなったなぁ
$1 = {part = {{modified = false, remote_kvm = true, remote_storage = false, console_redirection = false, routingIP = "▒\000", netmask = "▒▒▒▒"}, {
modified = false, remote_kvm = true, remote_storage = false, console_redirection = false, routingIP = "▒\000\001", netmask = "▒▒▒▒"}, {modified = false,
remote_kvm = true, remote_storage = false, console_redirection = false, routingIP = "▒\000\002", netmask = "▒▒▒▒"}, {modified = false,
remote_kvm = true, remote_storage = false, console_redirection = false, routingIP = "▒\000\003", netmask = "▒▒▒▒"}}}
(gdb)

バグでプロセスが死んだら、gdbの外で通常に再起動して、attachをやり直せば良い。dirやブレークポイントは保持できる。