[Qemu-devel] [Bug 1311614] Re: qemu-arm segfaults with gcc 4.9.0

[Paulo César Pereira de Andrade]

I debugged it originally but did only suggest a temporary workaround...
The crash, not really in qemu, looks like this:

--%<--
Remote debugging using localhost:1235
Reading symbols from
/home/fedya/openmandriva/home/fedya/root/lib/ld-linux-armhf.so.3...Reading
symbols from
/home2/fedya/openmandriva/home/fedya/root/usr/lib/debug/lib/ld-2.19.so.debug...done.
done.
Loaded symbols for 
/home/fedya/openmandriva/home/fedya/root/lib/ld-linux-armhf.so.3
0xf67dfd00 in _start ()
   from /home/fedya/openmandriva/home/fedya/root/lib/ld-linux-armhf.so.3
(gdb) c
Continuing.

Program received signal SIGSEGV, Segmentation fault.
memset () at ../ports/sysdeps/arm/memset.S:53
53              sfi_breg r3, \
(gdb) bt
#0  memset () at ../ports/sysdeps/arm/memset.S:53
#1  0xf650b5da in __pthread_getaffinity_new (address@hidden, cpusetsize=4,
    cpuset=0xf008) at ../nptl/sysdeps/unix/sysv/linux/pthread_getaffinity.c:41
#2  0xf60ca6d8 in gomp_init_num_threads () at
../../../libgomp/config/linux/proc.c:93
#3  0xf60c28b2 in initialize_env () at ../../../libgomp/env.c:1187
#4  0xf67ea514 in call_init (env=<optimized out>, argv=<optimized out>,
    argc=<optimized out>, l=<optimized out>) at dl-init.c:76
#5  _dl_init (main_map=0xf67fe908, argc=1, argv=0xf6ffecf4, env=0xf6ffecfc)
    at dl-init.c:124
#6  0xf67dfd32 in _dl_start_user ()
   from /home/fedya/openmandriva/home/fedya/root/lib/ld-linux-armhf.so.3
Backtrace stopped: previous frame identical to this frame (corrupt stack?)
(gdb) q
A debugging session is active.

        Inferior 1 [Remote target] will be killed.

Quit anyway? (y or n) y
--%<--

My suggestion was to report problems upstream ofcourse, and
a temporary quick fix would be to replace libgomp from the one
from gcc 4.8x or replace the body of gomp_init_num_threads
from gcc-4.9.0/libgomp/config/linux/proc.c with the one from
gcc-4.8.2/libgomp/config/linux/proc.c

I believe gcc 4.9 is too smart, and some stub is missing somewhere,
e.g. in the arm chroot checking /proc/cpuinfo shows x86_64 cpus.

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https://bugs.launchpad.net/bugs/1311614

Title:
  qemu-arm segfaults with gcc 4.9.0

Status in QEMU:
  New

Bug description:
  I have an ARM chroot that working with qemu-arm emulation

  address@hidden fedya]# cat /proc/sys/fs/binfmt_misc/arm
  enabled
  interpreter /usr/bin/qemu-arm-binfmt
  flags: P
  offset 0
  magic 7f454c4601010100000000000000000002002800
  mask ffffffffffffff00fffffffffffffffffeffffff

  
  In chroot installed gcc dependencies with 4.9.0 version

  sudo rpm --root /home/fedya/root/ -qa | grep 4.9.0

  libgcc1-4.9.0_2014.04-1-omv2013.0.armv7hl
  libgomp1-4.9.0_2014.04-1-omv2013.0.armv7hl
  libstdc++6-4.9.0_2014.04-1-omv2013.0.armv7hl
  gcc-4.9.0_2014.04-1-omv2013.0.armv7hl
  gcc-cpp-4.9.0_2014.04-1-omv2013.0.armv7hl
  libstdc++-devel-4.9.0_2014.04-1-omv2013.0.armv7hl
  gcc-c++-4.9.0_2014.04-1-omv2013.0.armv7hl

  
  When i try to run "rpm" , "rpmbuild", "rpm2cpio"command i always see qemu 
segfault message

  
  example:

  address@hidden /]# uname -a
  Linux filzbach.lindev.ch 3.13.6-nrjQL-desktop-70omv #1 SMP PREEMPT Wed Mar 12 
21:40:00 UTC 2014 armv7l armv7l armv7l GNU/Linux

  address@hidden /]# rpm
  qemu: uncaught target signal 11 (Segmentation fault) - core dumped

  
  Segfault became apparent only after gcc upgrade from 4.8.3 to 4.9.0.

  When i downgrade it to 4.8.3 all working fine again.
  It looks like a qemu bug with gcc.

  
  P.S.
  I tried to rebuild qemu with gcc 4.9.0
  I tried to build qemu from git sources, from fedora sources, from suse 
sources etc.

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