On Sat, Apr 14, 2012 at 4:52 PM, Philippe Waroquiers <philippe.waroqui...@skynet.be> wrote:
<snip> > The FIFOs and shared mem used by vgdb are based on the user name and the > host name. > The logic to find the user name is: > First try the env variable LOGNAME > if not set, try the env variable USER > if still not set, then take ???. > For the host name, the variables examined are: > HOST > then HOSTNAME > then ??? > You should start your gdb and vgdb in the same "context/environment" as the > gdbserver > you are trying to connect to. Then both the Valgrind gdbserver and vgdb > should agree > on user and host, and use the same vgdb-pipe files. > > If you cannot do that for one reason or another, you might try the following > (without guarantee :) : > export LOGNAME="???" > export HOST="???" > and then launch gdb+vgdb. > If you launch your gdb/vgdb under another account, the launched vgdb will > not have > rw access to the vgdb-pipe* files. To change the permissions, you will have > to one way or another let the apache user either chmod a+rw these files > or else use apache user to launch gdb and vgdb > (or maybe use root ?). > I tried starting apache webserver and gdb from root login. Did not help, because the valgrind is still launched from under apache user. So I set the LOGNAME and HOST to "???" as suggested above and started the webserver and gdb from root login. I also changed the permissions of the FIFOs using a+rw. Here is the output of the commands: *A] A.1 Valgrind (Apache log message) - Note that the error messages shown in the log start to appear after I connect to valgrind using gdb+vgdb: [plug@playground build]$ sudo tail -f /var/log/httpd/error_log [Sat Apr 14 22:31:20 2012] [notice] SELinux policy enabled; httpd running as context unconfined_u:system_r:httpd_t:s0 [Sat Apr 14 22:31:20 2012] [notice] suEXEC mechanism enabled (wrapper: /usr/sbin/suexec) [Sat Apr 14 22:31:20 2012] [notice] Digest: generating secret for digest authentication ... [Sat Apr 14 22:31:20 2012] [notice] Digest: done [Sat Apr 14 22:31:20 2012] [notice] Apache/2.2.22 (Unix) DAV/2 mod_fcgid/2.3.6 configured -- resuming normal operations [2012-Apr-14 22:36:07.303928] 13140 - [info] "WServer/wtfcgi: initializing relay server" [2012-Apr-14 22:36:07.306978] 13140 - [info] "config: reading Wt config file: /etc/wt/wt_config.xml (location = '/var/www/html/plug/docroot/testwtdbg.wt')" [2012-Apr-14 22:36:07.308753] 13140 - [info] "wtfcgi: reading FastCGI stream from stdin" [2012-Apr-14 22:36:07.319148] 13140 - [info] "wtfcgi: spawned dedicated process for cMbPKxS2lzXyceXq: pid=13151" ==13151== Memcheck, a memory error detector ==13151== Copyright (C) 2002-2011, and GNU GPL'd, by Julian Seward et al. ==13151== Using Valgrind-3.7.0 and LibVEX; rerun with -h for copyright info ==13151== Command: /var/www/html/plug/docroot/testwtdbg.wt client cMbPKxS2lzXyceXq ==13151== --13151-- Valgrind options: --13151-- -v --13151-- --trace-children=yes --13151-- --vgdb=full --13151-- --vgdb-error=0 --13151-- Contents of /proc/version: --13151-- Linux version 3.3.1-3.fc16.x86_64 (mockbu...@x86-12.phx2.fedoraproject.org) (gcc version 4.6.3 20120306 (Red Hat 4.6.3-2) (GCC) ) #1 SMP Wed Apr 4 18:08:51 UTC 2012 --13151-- Arch and hwcaps: AMD64, amd64-sse3 --13151-- Page sizes: currently 4096, max supported 4096 --13151-- Valgrind library directory: /usr/local/lib/valgrind --13151-- Reading syms from /var/www/html/plug/docroot/testwtdbg.wt (0x400000) --13151-- Reading syms from /usr/local/lib/valgrind/memcheck-amd64-linux (0x38000000) --13151-- object doesn't have a dynamic symbol table --13151-- Reading syms from /lib64/ld-2.14.90.so (0x3d26200000) --13151-- Reading suppressions file: /usr/local/lib/valgrind/default.supp ==13151== (action at startup) vgdb me ... ==13151== embedded gdbserver: reading from /tmp/vgdb-pipe-from-vgdb-to-13151-by-???-on-??? ==13151== embedded gdbserver: writing to /tmp/vgdb-pipe-to-vgdb-from-13151-by-???-on-??? ==13151== embedded gdbserver: shared mem /tmp/vgdb-pipe-shared-mem-vgdb-13151-by-???-on-??? ==13151== ==13151== TO CONTROL THIS PROCESS USING vgdb (which you probably ==13151== don't want to do, unless you know exactly what you're doing, ==13151== or are doing some strange experiment): ==13151== /usr/local/lib/valgrind/../../bin/vgdb --pid=13151 ...command... ==13151== ==13151== TO DEBUG THIS PROCESS USING GDB: start GDB like this ==13151== /path/to/gdb /var/www/html/plug/docroot/testwtdbg.wt ==13151== and then give GDB the following command ==13151== target remote | /usr/local/lib/valgrind/../../bin/vgdb --pid=13151 ==13151== --pid is optional if only one valgrind process is running ==13151== ==13151== putpkt(write) error: no write_remote_desc ==13151== putpkt(write) error: no write_remote_desc ==13151== putpkt(write) error: no write_remote_desc ==13151== putpkt(write) error: no write_remote_desc ==13151== putpkt(write) error: no write_remote_desc ==13151== putpkt(write) error: no write_remote_desc ==13151== putpkt(write) error: no write_remote_desc ==13151== putpkt(write) error: no write_remote_desc ==13151== putpkt(write) error: no write_remote_desc ==13151== putpkt(write) error: no write_remote_desc ==13151== putpkt(write) error: no write_remote_desc ==13151== putpkt(write) error: no write_remote_desc ==13151== putpkt(write) error: no write_remote_desc ==13151== putpkt(write) error: no write_remote_desc ==13151== putpkt(write) error: no write_remote_desc *B] B.1 The read-write permissions of the FIFOs. I update the permissions after valgrind starts but before gdb+vgdb is launched. [plug@playground build]$ ls -la /tmp/vgdb* prw-rw-rw-. 1 apache apache 0 Apr 14 22:36 /tmp/vgdb-pipe-from-vgdb-to-13151-by-???-on-??? -rw-rw-rw-. 1 apache apache 48 Apr 14 22:36 /tmp/vgdb-pipe-shared-mem-vgdb-13151-by-???-on-??? prw-rw-rw-. 1 apache apache 0 Apr 14 22:36 /tmp/vgdb-pipe-to-vgdb-from-13151-by-???-on-??? *C] C.1 The output of gdb+vgdb (Note that I also tried setting the "remotetimeout" attribute of gdb to very large value as suggested in README_DEVELOPERS file. But the result is the same except that no error is displayed on gdb console and the control just waits (stalls?) after printing the message "Remote debugging using | vgdb --pid=13151" and does not return to gdb prompt. On the valgrind side though the same error, "putpkt(write) error: no write_remote_desc", is displayed as before except there is just one error rather than same error printed multiple times) [root@playground build]# gdb /var/www/html/plug/docroot/testwtdbg.wt GNU gdb (GDB) Fedora (7.3.50.20110722-13.fc16) Copyright (C) 2011 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. Type "show copying" and "show warranty" for details. This GDB was configured as "x86_64-redhat-linux-gnu". For bug reporting instructions, please see: <http://www.gnu.org/software/gdb/bugs/>... Reading symbols from /var/www/html/plug/docroot/testwtdbg.wt...done. (gdb) show env LOGNAME LOGNAME = ??? (gdb) show env HOST HOST = ??? (gdb) target remote | vgdb --pid=13151 Remote debugging using | vgdb --pid=13151 relaying data between gdb and process 13151 Ignoring packet error, continuing... warning: unrecognized item "timeout" in "qSupported" response Ignoring packet error, continuing... Ignoring packet error, continuing... Ignoring packet error, continuing... Ignoring packet error, continuing... Ignoring packet error, continuing... Ignoring packet error, continuing... Malformed response to offset query, timeout (gdb) *D] D.1 gdb, valgrind, apache and linux distro versions I am using: [plug@playground build]# gdb --version GNU gdb (GDB) Fedora (7.3.50.20110722-13.fc16) Copyright (C) 2011 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. Type "show copying" and "show warranty" for details. This GDB was configured as "x86_64-redhat-linux-gnu". For bug reporting instructions, please see: <http://www.gnu.org/software/gdb/bugs/>. [plug@playground build]# valgrind --version valgrind-3.7.0 [plug@playground build]$ uname -a Linux playground.fc16 3.3.1-3.fc16.x86_64 #1 SMP Wed Apr 4 18:08:51 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux Apache version is 2.2.22 and mod_fcgid is 2.3.6 *E] E.1 The output of `vgdb -d -d -d help --pid=13151` command is a continuous non-stop flow of following message: written_by_vgdb_before_sleep 1 seen_by_valgrind_before_sleep 1 Does valgrind ignore, for security reasons, the FIFOs with universal write access? I think I read something to this regard but am not able to recall where! Also, I am not able to login as user "apache" and instead have to login as root. But all this has not helped me debug using valgrind a process under apache's context. The constraint that gdb, vgdb and gdbserver all should start under the same context/environment is proving to be quite restrictive. Thanks and regards, ~Plug > Hope this helps ... > > Philippe ------------------------------------------------------------------------------ For Developers, A Lot Can Happen In A Second. Boundary is the first to Know...and Tell You. Monitor Your Applications in Ultra-Fine Resolution. Try it FREE! http://p.sf.net/sfu/Boundary-d2dvs2 _______________________________________________ Valgrind-users mailing list Valgrind-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/valgrind-users
