Re: [Libunwind-devel] unwinding from signal handler (i586)

[Ken Werner]

On 08/22/2011 12:12 PM, Sven Neumann wrote:
> On Mon, 2011-08-22 at 13:03 +0300, Lassi Tuura wrote:
> > Hi,
> >
> > > > # ./main
> > > > standard frame  ip:  0x80488f3, sp: 0xbfbcea00   sig_handler
> > > > Segmentation fault
> > > >
> > > > I will try to find some time to debug this further...
> > >
> > > In the hope that it helps, here's the libunwind debug output from this
> > > segmentation fault:
> > >
> > > # UNW_DEBUG_LEVEL=9999 ./main
> > [...]
> >
> > > > access_reg: ebp ->  bfb4ebe8
> > > > access_mem: mem[bfb4ebec] ->  0
> > > > _Ux86_dwarf_step: returning 0
> > > > _Ux86_step: returning 0
> > > Segmentation fault
> >
> > Does it actually crash in libunwind? From above it sounds like it already
> > returned fine to your application and crashes there.
>
> Well, the code I am running is the test-case that Ken posted earlier in
> this thread.

I was not able to reproduce the segfault on my i686 system (Ubuntu 
11.04). This is how I've built libunwind on this machine:
  autoreconf -i
  ./configure CFLAGS="-U_FORTIFY_SOURCE"
  make -j`getconf _NPROCESSORS_ONLN`

The testcase passes with and without USE_TIMER defined:
  LD_LIBRARY_PATH=../../src/.libs ./main
  standard frame        ip:  0x8048873, sp: 0xbfa2b670   sig_handler
  signal frame  ip: 0x4009ff10, sp: 0xbfa2bc10   killpg
  standard frame        ip:  0x8048b90, sp: 0xbfa2bd20   main
  standard frame        ip: 0x4008be37, sp: 0xbfa2bd30   __libc_start_main
  standard frame        ip:  0x80487a1, sp: 0xbfa2bdb0   _start

When running the testsuite I see two failing testcases which are both 
unrelated to local unwinding:
  FAIL: test-setjmp
  FAIL: test-ptrace

Regards
Ken