调试apache模块及检测内存泄漏(转载)
上一篇 / 下一篇 2011-01-03 18:42:32 / 个人分类:测试技术
调试apache模块. 1. 调试工具 gdb, emacs 2. 在emacs里.M-x,gdb httpd. 出现gdb的shell. b mod_xx.c:fun (下断点在某个模块的某个函数上) r -X (以调试模式运行apache,只有一个工作者进程提供服务) 3. 在客户端(浏览器)发起一个请求. 4. 断到指定的函数上. 5. 常规的调试流程. 检测apache模块的内存泄漏 1. 工具 valgrind (瑞士军刀的说...) 2. valgrind --leak-check=full ./httpd -X 3. 在客户端(浏览器)发起一个请求. 4. 因为以-X模式运行,所以当前console被绑定到apache的输出上了. 5. 另开个shell输出./apachectl stop 6. 运行valgrind的console会输出结果. The Apache HTTP Server Project Apache Debugging Guide This document is a collection of notes regarding tools and techniques for debugging Apache and Apache modules. Got more tips? Send 'em to docs@httpd.apache.org. Thanks! 1. Using gdb 2. Getting a live backtrace 3. Using 'truss/trace/strace' to trace system calls and signals 4. Getting the server to dump core 5. Solaris 2.7 and coredumps 6. Getting and analyzing a TCP packet trace Using gdb If you use the gcc or egcs compilers, it is likely that the best debugger for your system is gdb. This is only a brief summary of how to run gdb on Apache -- you should look at the info and man files for gdb to get more information on gdb commands and common debugging techniques. Before running gdb, be sure that the server is compiled with the -g option in EXTRA_CFLAGS to include the symbol information in the object files. The only tricky part of running gdb on Apache is forcing the server into a single-process mode so that the parent process being debugged does the request-handling work instead of forking child processes. We have provided the -X option for that purpose, which will work fine for most cases. However, some modules don't like starting up with -X, but are happy if you force only one child to run (using "MaxClients 1"); you can then use gdb's attach command to debug the child server. The following example, with user input in green, shows the output of gdb run on a server executable (httpd) in the current working directory and using the server root of /usr/local/apache: % gdb httpd GDB is free software and you are welcome to distribute copies of it under certain conditions; type "show copying" to see the conditions. There is absolutely no warranty for GDB; type "show warranty" for details. GDB 4.16.gnat.1.13 (sparc-sun-solaris2.5), Copyright 1996 Free Software Foundation, Inc... (gdb) b ap_process_request Breakpoint 1 at 0x49fb4: file http_request.c, line 1164. (gdb) run -X -d /usr/local/apache Starting program: /usr/local/apache/src/httpd -X -d /usr/local/apache [at this point I make a request from another window] Breakpoint 1, ap_process_request (r=0x95250) at http_request.c:1164 1164 if (ap_extended_status) (gdb) s 1165 ap_time_process_request(r->connection->child_num, START_PREQUEST); (gdb) n 1167 process_request_internal(r); (gdb) s process_request_internal (r=0x95250) at http_request.c:1028 1028 if (!r->proxyreq && r->parsed_uri.path) { (gdb) s 1029 access_status = ap_unescape_url(r->parsed_uri.path); (gdb) n 1030 if (access_status) { (gdb) s 1036 ap_getparents(r->uri); /* OK --- shrinking transformations... */ (gdb) n 1038 if ((access_status = location_walk(r))) { (gdb) n 1043 if ((access_status = ap_translate_name(r))) { (gdb) n 1048 if (!r->proxyreq) { (gdb) n 1053 if (r->method_number == M_TRACE) { (gdb) n 1062 if (r->proto_num > HTTP_VERSION(1,0) && ap_table_get(r->subprocess_env, "downgrade-1.0")) { (gdb) n 1071 if ((access_status = directory_walk(r))) { (gdb) s directory_walk (r=0x95250) at http_request.c:288 288 core_server_config *sconf = ap_get_module_config(r->server->module_config, (gdb) b ap_send_error_response Breakpoint 2 at 0x47dcc: file http_protocol.c, line 2090. (gdb) c Continuing. Breakpoint 2, ap_send_error_response (r=0x95250, recursive_error=0) at http_protocol.c:2090 2090 BUFF *fd = r->connection->client; (gdb) where #0 ap_send_error_response (r=0x95250, recursive_error=0) at http_protocol.c:2090 #1 0x49b10 in ap_die (type=403, r=0x95250) at http_request.c:989 #2 0x49b60 in decl_die (status=403, phase=0x62db8 "check access", r=0x95250) at http_request.c:1000 #3 0x49f68 in process_request_internal (r=0x95250) at http_request.c:1141 #4 0x49fe0 in ap_process_request (r=0x95250) at http_request.c:1167 #5 0x439d8 in child_main (child_num_arg=550608) at http_main.c:3826 #6 0x43b5c in make_child (s=0x7c3e8, slot=0, now=907958743) at http_main.c:3898 #7 0x43ca8 in startup_children (number_to_start=6) at http_main.c:3972 #8 0x44260 in standalone_main (argc=392552, argv=0x75800) at http_main.c:4250 #9 0x449fc in main (argc=4, argv=0xefffee8c) at http_main.c:4534 (gdb) s 2091 int status = r->status; (gdb) p status $1 = 403 (gdb) There are a few things to note about the above example: 1. the "gdb httpd" command does not include any command-line options for httpd: those are provided when the "run" command is done within gdb; 2. I set a breakpoint before starting the run so that execution would stop at the top of ap_process_request(); 3. the "s" command steps through the code and into called procedures, whereas the "n" (next) command steps through the code but not into called procedures. 4. additional breakpoints can be set with the "b" command, and the run continued with the "c" command. 5. use the "where" command (a.k.a. "bt") to see a stack backtrace that shows the order of called procedures and their parameter values. 6. use the "p" command to print the value of a variable. A file in the src/ directory, .gdbinit, provides a useful macro for printing out the contents of a table structure, called dump_table. If you are debugging a repeatable crash, simply run gdb as above and make the request -- gdb should capture the crash and provide a prompt where it occurs. If you are debugging an apparent infinite loop, simply run gdb as above and type a Control-C -- gdb will interrupt the process and provide a prompt where it was stopped. If you are debugging a system crash and you have a core file from the crash, then do the following: % gdb httpd -c core (gdb) where and it will (hopefully) print a stack backtrace of where the core dump occurred during processing. Getting a live backtrace A backtrace will let you know the hierarchy of procedures that were called to get to a particular point in the process. On some platforms you can get a live backtrace of any process. For SVR4-based variants of Unix, the pstack command for proc can be used to display a a live backtrace. For example, on Solaris it looks like % /usr/proc/bin/pstack 10623 10623: httpd -d /usr/local/apache ef5b68d8 poll (efffcd08, 0, 3e8) ef5d21e0 select (0, ef612c28, 0, 0, 3e8, efffcd08) + 288 00042574 wait_or_timeout (0, 75000, 75000, 7c3e8, 60f40, 52c00) + 78 00044310 standalone_main (5fd68, 75800, 75c00, 75000, 2, 64) + 240 000449f4 main (3, efffeee4, efffeef4, 75fe4, 1, 0) + 374 000162fc _start (0, 0, 0, 0, 0, 0) + 5c Another technique is to use gdb to attach to the running process and then using "where" to print the backtrace, as in % gdb httpd 10623 GDB is free software and you are welcome to distribute copies of it under certain conditions; type "show copying" to see the conditions. There is absolutely no warranty for GDB; type "show warranty" for details. GDB 4.16.gnat.1.13 (sparc-sun-solaris2.5), Copyright 1996 Free Software Foundation, Inc... /usr/local/apache/src/10623: No such file or directory. Attaching to program `/usr/local/apache/src/httpd', process 10623 Reading symbols from /usr/lib/libsocket.so.1...done. Reading symbols from /usr/lib/libnsl.so.1...done. Reading symbols from /usr/lib/libc.so.1...done. Reading symbols from /usr/lib/libdl.so.1...done. Reading symbols from /usr/lib/libintl.so.1...done. Reading symbols from /usr/lib/libmp.so.1...done. Reading symbols from /usr/lib/libw.so.1...done. Reading symbols from /usr/platform/SUNW,Ultra-1/lib/libc_psr.so.1...done. 0xef5b68d8 in () (gdb) where #0 0xef5b68d8 in () #1 0xef5d21e8 in select () #2 0x4257c in wait_or_timeout (status=0x0) at http_main.c:2357 #3 0x44318 in standalone_main (argc=392552, argv=0x75800) at http_main.c:4273 #4 0x449fc in main (argc=3, argv=0xefffeee4) at http_main.c:4534 (gdb) Using '' to trace system calls and signals Most Unix-based systems have at least one command for displaying a trace of system calls and signals as they are accessed by a running process. This command is called truss on most SVR4-based systems and either trace or strace on many other systems. A useful tip for using the truss command on Solaris is the -f option; it tells truss to follow and continue tracing any child processes forked by the main process. The easiest way to get a full trace of a server is to do something like: % truss -f httpd -d /usr/local/apache >& outfile % egrep '^10698:' outfile to view just the trace of the process id 10698. Getting the server to dump core Strangely enough, sometimes you actually want to force the server to crash so that you can get a look at some nutty behavior. Normally this can be done simply by using the gcore command. However, for security reasons, most Unix systems do not allow a setuid process to dump core, since the file contents might reveal something that is supposed to be protected in memory. Here is one way to get a core file from a setuid Apache httpd process on Solaris, without knowing which httpd child might be the one to die [note: it is probably easier to use the MaxClients trick in the first section above]. # for pid in `ps -eaf | fgrep httpd | cut -d' ' -f4` do truss -f -l -t!all -S SIGSEGV -p $pid 2>&1 | egrep SIGSEGV & done The undocumented '-S' flag to truss will halt the process in place upon receipt of a given signal (SIGSEGV in this case). At this point you can use: # gcore PID and then look at the backtrace as discussed above for gdb. Solaris 2.7 and coredumps On Solaris 2.7 use coreadm to make setuid() processes actually dump core. By default an setuid() process does not dump core. Jens-Uwe Mager wrote: For example I am using: # coreadm global core file pattern: /var/core/core.%f.%p.u%u init core file pattern: core global core dumps: enabled per-process core dumps: enabled global setid core dumps: enabled per-process setid core dumps: enabled global core dump logging: disabled Getting and analyzing a TCP packet trace This is more difficult than I have time to describe at the moment. Here are some pointers to useful discussions and tools: * tools for producing TCP dumps * tcptrace is a TCP dump file analysis tool * tcpshow is another There is also a simple ASCII viewer for TCP dump traces in the Apache repository in the file src/test/tcpdumpscii.txt. Copyright © 1999-2002, The Apache Software Foundation 陈绪:要想调试apache,编译时必须加入-g参数,如 CFLAGS=-g ./configure --enable-module=most --enable-shared=max --enable-suexec --suexec-caller=nobody --suexec-docroot=/usr/local/apache/htdocs --suexec-logfile=/usr/local/apache/logs/suexec_log --suexec-userdir=public_html --suexec-uidmin=100 --suexec-gidmin=100 --suexec-safepath=/usr/local/bin:/usr/bin:/bin 模块中如果要使用Mysql的c函数: 1. 包含头文件<mysql.h> 2. 修改ld.so.conf,加入一行/usr/local/mysql/lib/mysql,然后ldconfig -v; 3. 修改/usr/local/apache/bin/apxs, 修改CFG_CFLAGS为 my $CFG_CFLAGS = q( -DLINUX=22 -I/usr/include/db1 -DUSE_HSREGEX -g `../apaci` -I/usr/include/mysql); 4. 修改/usr/local/apache/conf/httpd.conf, 修改加入3行为 LoadFile /usr/lib/mysql/libmysqlclient_r.so LoadModule random_module libexec/mod_random.so LoadModule php4_module libexec/libphp4.so http://hi.baidu.com/andrewhome/blog/item/3d8f74a2e2cb6baacbefd0e4.html |
TAG:
标题搜索
日历
|
|||||||||
日 | 一 | 二 | 三 | 四 | 五 | 六 | |||
1 | 2 | 3 | 4 | ||||||
5 | 6 | 7 | 8 | 9 | 10 | 11 | |||
12 | 13 | 14 | 15 | 16 | 17 | 18 | |||
19 | 20 | 21 | 22 | 23 | 24 | 25 | |||
26 | 27 | 28 | 29 | 30 | 31 |
我的存档
数据统计
- 访问量: 44586
- 日志数: 56
- 文件数: 1
- 建立时间: 2009-08-22
- 更新时间: 2018-07-26