|Summary:||gdb unable to give stack traces across signal handler (UML)|
|Product:||[Retired] Red Hat Linux||Reporter:||Mike Shaver <shaver>|
|Component:||gdb||Assignee:||Elena Zannoni <ezannoni>|
|Status:||CLOSED ERRATA||QA Contact:||Jay Turner <jturner>|
|Fixed In Version:||Doc Type:||Bug Fix|
|Doc Text:||Story Points:||---|
|Last Closed:||2004-03-10 16:43:54 UTC||Type:||---|
|oVirt Team:||---||RHEL 7.3 requirements from Atomic Host:|
|Cloudforms Team:||---||Target Upstream Version:|
Description Mike Shaver 2002-10-24 15:34:21 UTC
When running user-mode Linux under gdb in Red Hat 8.0, I am unable to get a stack trace that goes back before a signal handler runs. Only the functions called from the signal handler (in this case, |segv| and |panic|) are visible when stopped at a breakpoint in |panic|. Manual walking of $ebp will let me find calling PCs, so the stack hasn't been trashed. I've tried with both gcc version 2.96 20000731 (Red Hat Linux 7.3 2.96-110) and gcc version 3.2 20020903 (Red Hat Linux 8.0 3.2-7) with similar results. I will try to find time to try with a RH7.3-era gdb to see if the results are different. The user-mode Linux in question is built from the Red Hat 2.4.18-14 kernel, with some VFS patches. gdb-5.2.1-4
Comment 1 Elena Zannoni 2002-10-31 19:26:59 UTC
Could you attach a copy of gdb's backtrace output? I suspect this is a known bug, and it is being fixed in the FSF gdb development branch. Thanks Elena
Comment 2 Mike Shaver 2002-10-31 19:38:00 UTC
Now that I've started using the compat-gcc-7.3 gcc to build my kernel, the problem has gone away. I can try to restore the old setup, if you really need me too, but the stack trace would look very much like: (gdb) bt #0 0xdeadbeef in panic (args to panic) at panic_source.c:42 #1 0xcafebabe in segv (args to segv) at segv_source.c:1977 (gdb) Trying to go up from frame 1 would tell me (gdb) up Initial frame selected; you cannot go up. I'll try a build with 3.2 this weekend, once I'm finished with my current development task.
Comment 3 Elena Zannoni 2002-10-31 19:56:20 UTC
Thanks, could I also bribe you in trying the current FSF gdb on sources.redhat.com/gdb? A fix was recently checked in for this problem. (Ignore the 5.3 branch). Elena
Comment 4 Mike Shaver 2002-10-31 19:58:05 UTC
Sure. Once I've torched my development environment, I don't mind dancing on the ashes. =) Can I just grab a today-or-later snapshot, or should I really pull from CVS?
Comment 5 Elena Zannoni 2002-10-31 20:21:22 UTC
The snapshots should be ok.
Comment 6 John Flanagan 2004-05-18 19:15:44 UTC
An errata has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on the solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHBA-2004-126.html