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Bug#548842: marked as done (libc6: alignment error in /lib/ld-linux.so.3 on armel)

Your message dated Mon, 23 Nov 2009 23:37:00 -0500
with message-id <4B0B62EC.4030901@fifthhorseman.net>
and subject line debian bug #548842 resolved in libstdc++6 4.4.2-3
has caused the Debian Bug report #548842,
regarding libc6: alignment error in /lib/ld-linux.so.3 on armel
to be marked as done.

This means that you claim that the problem has been dealt with.
If this is not the case it is now your responsibility to reopen the
Bug report if necessary, and/or fix the problem forthwith.

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-- 
548842: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=548842
Debian Bug Tracking System
Contact owner@bugs.debian.org with problems
--- Begin Message --- 
Package: libc6
Version: 2.9-25
Severity: normal

I'm running alsaplayer on an armel platform, using the -text frontend 
and the -alsa output.  I've configured my armel machine to send a SIGBUS
to any process which makes an alignment error by doing this:

 echo 5 > /proc/cpu/alignment

when i launch the player (compiled with debug symbols), even before it 
gets to main() i get the SIGBUS.

Here's the backtrace i see with libc6-dbg installed:

(gdb) bt
#0  elf_machine_rel (scope=0x4001e1a0, lazy=1, consider_profiling=0) at ../ports/sysdeps/arm/dl-machine.h:429
#1  elf_dynamic_do_rel (scope=0x4001e1a0, lazy=1, consider_profiling=0) at do-rel.h:120
#2  _dl_relocate_object (scope=0x4001e1a0, lazy=1, consider_profiling=0) at dl-reloc.c:266
#3  0x400039bc in dl_main (phdr=0x8034, phnum=8, user_entry=0xbe98257c) at rtld.c:2231
#4  0x40015110 in _dl_sysdep_start (start_argptr=<value optimized out>, dl_main=0x400021d8 <dl_main>) at ../elf/dl-sysdep.c:239
#5  0x40000cd0 in _dl_start_final (arg=0xbe982870, info=0xbe9825f8) at rtld.c:332
#6  0x40000f68 in _dl_start (arg=0xbe982870) at rtld.c:560
#7  0x400007f0 in _start () from /lib/ld-linux.so.3
#8  0x400007f0 in _start () from /lib/ld-linux.so.3
Backtrace stopped: previous frame identical to this frame (corrupt stack?)
(gdb) 

that last line is just:

  *reloc_addr += value

but reloc_addr is optimized out.

unfortunately, rebuilding packages (esp. large packages like libc6) takes 
a long time on machines like this (it's an NSLU2, 266Mhz with 32MB RAM),
so i haven't had a chance to debug further.

People interested in this bug might also be interested in discussion 
from http://bugs.debian.org/397616 .  for examples of potential dangers 
of undetected memory alignment failures, see 
http://bugs.debian.org/548815 -- hopefully alignment failures in libc6 
won't cause higher-level trouble the way they do with some media codecs.

I also asked for discussion in general about alignment issues on armel:

 http://lists.debian.org/debian-arm/2009/09/msg00109.html
 
Let me know if i can provide more debugging help on this.  

	--dkg

-- System Information:
Debian Release: squeeze/sid
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: armel (armv5tel)

Kernel: Linux 2.6.30-1-ixp4xx
Locale: LANG=C, LC_CTYPE=C (charmap=ANSI_X3.4-1968)
Shell: /bin/sh linked to /bin/dash

Versions of packages libc6 depends on:
ii  libc-bin                      2.9-25     GNU C Library: Binaries
ii  libgcc1                       1:4.4.1-1  GCC support library

libc6 recommends no packages.

Versions of packages libc6 suggests:
ii  debconf [debconf-2.0]         1.5.27     Debian configuration management sy
pn  glibc-doc                     <none>     (no description available)
ii  locales                       2.9-25     GNU C Library: National Language (

-- debconf information:
* glibc/restart-services: cron
  glibc/disable-screensaver:
  glibc/restart-failed:
  glibc/upgrade: true

--- End Message ---
--- Begin Message --- 
Version: 4.4.2-3

Debian bug #548842 was resolved by upgrading libstdc++6 to version 4.4.2-3.

The last version that i saw that had the bug was 4.4.1-4, as detailed in
an earlier message to the bug log.

	--dkg

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