Bug 76645

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>
Severity:	medium	Docs Contact:
Priority:	medium
Version:	8.0	CC:	srevivo
Target Milestone:	---
Target Release:	---
Hardware:	athlon
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2004-03-10 16:43:54 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

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