Ubuntu
gdb package

dropped patch reintroduces gcore relro backtrace problem

Bug #954714 reported by Steve Beattie on 2012-03-14

This bug affects 1 person

Affects		Status	Importance	Assigned to	Milestone
	gdb (Ubuntu)	Fix Released	High	Matthias Klose	Ubuntu ubuntu-12.04-beta-2

Bug Description

The recent gdb upload https://launchpad.net/ubuntu/+source/gdb/7.4-2012.02-0ubuntu1 disabled the patch gdb-7.2-gcore-relro-writer.patch which was added to address bug 680588. The reason the patch was disabled was because it no longer cleanly applies to the gdb source tree; the gdb/linux-nat.c source file is significantly different in the 7.4-2012.02 version.

I've confirmed that an updated version of the patch is still necessary; with 7.4-2012.02-0ubuntu1 backtraces like the following are generated:

  (gdb) bt
  #0 0x00007fda019b82b0 in ?? ()
  #1 0x00007fda019b816c in ?? ()
  #2 0x0000000000000000 in ?? ()

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: gdb 7.4-2012.02-0ubuntu1
ProcVersionSignature: Ubuntu 3.2.0-18.29-generic 3.2.9
Uname: Linux 3.2.0-18-generic x86_64
ApportVersion: 1.94.1-0ubuntu2
Architecture: amd64
Date: Tue Mar 13 21:14:46 2012
InstallationMedia: Ubuntu-Server 10.04 "Lucid Lynx" - Alpha amd64 (20100330)
ProcEnviron:
TERM=screen
PATH=(custom, user)
LANG=en_US.UTF-8
SHELL=/bin/bash
SourcePackage: gdb
UpgradeStatus: Upgraded to precise on 2012-01-18 (55 days ago)

Tags:

Related branches

lp:ubuntu/precise/gdb

Revision history for this message

Steve Beattie (sbeattie) wrote on 2012-03-14:

Dependencies.txt Edit (758 bytes, text/plain; charset="utf-8")

Revision history for this message

Steve Beattie (sbeattie) wrote on 2012-03-14:

Attached is a first attempt at updating the relro patch for gdb-7.4-2012.02. It still needs to emit a warning if the sscanf(3) fails to match anything, but it appears to work correctly without issue in local testing.

Revision history for this message

Ubuntu Foundations Team Bug Bot (crichton) wrote on 2012-03-14:

The attachment "gdb-7.2-gcore-relro-writer.patch" of this bug report has been identified as being a patch. The ubuntu-reviewers team has been subscribed to the bug report so that they can review the patch. In the event that this is in fact not a patch you can resolve this situation by removing the tag 'patch' from the bug report and editing the attachment so that it is not flagged as a patch. Additionally, if you are member of the ubuntu-reviewers team please also unsubscribe the team from this bug report.

[This is an automated message performed by a Launchpad user owned by Brian Murray. Please contact him regarding any issues with the action taken in this bug report.]

tags:

added: patch

Marc Deslauriers (mdeslaur) on 2012-03-14

Changed in gdb (Ubuntu):
milestone:	none → ubuntu-12.04-beta-2
assignee:	nobody → Canonical Foundations Team (canonical-foundations)
tags:	added: rls-p-tracking

Revision history for this message

Steve Langasek (vorlon) wrote on 2012-03-14:

Matthias, please have a look at this.

Changed in gdb (Ubuntu):
assignee:	Canonical Foundations Team (canonical-foundations) → Matthias Klose (doko)
importance:	Undecided → High

Revision history for this message

Steve Beattie (sbeattie) wrote on 2012-03-15:

gdb-7.2-gcore-relro-writer.patch Edit (13.6 KiB, text/plain)

Here's an updated patch that adds a warning if the sscanf(3) line in gdb/linux-tdep.c fails. I've again verified locally that the patch causes gcore to generate a corefile such that gdb can generate an accurate backtrace from it.

I would appreciate review on the changes made to gdb/linux-tdep.c in the patch. It attempts to do what the prior version of the patch did, parsing /proc/PID/smaps instead of /proc/PID/maps and look for whether a few specific entries in each mapping are non-zero to indicate whether the mapping has been modified. The code in question was moved from gdb/linux-nat.c to gdb/linux-tdep.c and restructured to be line-oriented, which complicted things a bit.

Revision history for this message

Thiago Jung Bauermann (thiago-bauermann) wrote on 2012-03-15:

I'm reviewing this patch.

I ran the GDB testsuite with it and there are no regressions on i686-linux.

Tomorrow I'll test it on x86_64 and finish my review of the code.

Revision history for this message

Thiago Jung Bauermann (thiago-bauermann) wrote on 2012-03-15:

I finished reviewing the patch. It looks great to me. Also the gcore-relro.exp testcase which exercises the patch passes, and there are no regressions on i686 nor x86_64.

Thanks for working on it, Steve!

Revision history for this message

Launchpad Janitor (janitor) wrote on 2012-03-16:

This bug was fixed in the package gdb - 7.4-2012.02-0ubuntu2

---------------
gdb (7.4-2012.02-0ubuntu2) precise; urgency=low

* Update and re-enable the gdb-7.2-gcore-relro-writer patch (Steve Beattie).
LP: #954714.
-- Matthias Klose <email address hidden> Fri, 16 Mar 2012 01:32:38 +0100