Re: [Libunwind-devel] SIGSEGV in ARM+Alarm handler

[Harald Servat]

Hello,

  according to the same core and listing in gdb, the instr value is set 
by dwarf_get which does not returns an error.

  So can anyone experienced with ARM give his or her thoughts?

(gdb) list
239                   instr -= 8;
240                   if (dwarf_get(&c->dwarf, DWARF_LOC(instr, 0), &instr) < 0)
241                     {
242                       return 0;
243                     }
244                   if ((instr & 0xFFFFD800) == 0xE92DD800)
245                     {
246                       /* Standard APCS frame. */
247                       ip_loc = DWARF_LOC(frame - 4, 0);
248                       fp_loc = DWARF_LOC(frame - 12, 0);

(gdb) print instr
Cannot access memory at address 0x1539

Thank you.

On 09/28/2015 04:12 PM, Harald Servat wrote:
> Hello,
>
>    is there any hint that we can follow to fix this?
>
> Regards.
>
>
> On 09/23/2015 11:49 AM, Harald Servat wrote:
> > Dear all,
> >
> >    we have encountered the following SIGSEGV in a ARM system when
> > unwinding the stack in a alarm handler. We're currently using the latest
> > version of libunwind available from the GIT repository. The system is
> > currently running linux kernel 3.11 with the following processor
> >
> > model name    : ARMv7 Processor rev 4 (v7l)
> > Features    : swp half thumb fastmult vfp edsp neon vfpv3 tls vfpv4
> > idiva idivt vfpd32 lpae
> >
> >    The libunwind library was compiled using a regular
> >
> >    ./configure --prefix=<DIR> and the CFLAGS within the Makefile is
> >
> >    -g -O2 -fexceptions -Wall -Wsign-compare
> >
> >    Our sampling library is compiled with the following flags
> >
> >    -g -O2 -fno-optimize-sibling-calls -funwind-tables -Wall -W
> >
> >    and the binary to be sampled is compiled using
> >
> >    -O3 -g -funwind-tables -march=armv7 -mtune=cortex-a15
> > -mfloat-abi=hard -mfpu=neon
> >
> >    Any thoughts on what might be wrong? What else could I provide to
> > help fixing this issue?
> >
> > Thank you very much in advance.
> >
> > Core was generated by `./stream.i'.
> > Program terminated with signal SIGSEGV, Segmentation fault.
> > #0  _ULarm_step (address@hidden) at arm/Gstep.c:244
> > 244                  if ((instr & 0xFFFFD800) == 0xE92DD800)
> > (gdb) where
> > #0  _ULarm_step (address@hidden) at arm/Gstep.c:244
> > #1  0xb6db99b4 in trace_callers (time=4294967297, offset=5,
> > address@hidden,
> >      address@hidden) at calltrace.c:79
> > #2  0xb6dd0024 in Extrae_SamplingHandler (address=0xb6ce8b6c
> > <__memcpy_neon+748>)
> >      at sampling-timer.c:96
> > #3  0xb6dd00d0 in TimeSamplingHandler (sig=<optimized out>,
> > siginfo=<optimized out>,
> >      context=<optimized out>) at sampling-timer.c:206
> > #4  <signal handler called>
> > #5  0xb6ce8b6c in __memcpy_neon ()
> >      at ../ports/sysdeps/arm/armv7/multiarch/memcpy_impl.S:596
> > #6  0x00008944 in mysecond () at stream.c:422
> > #7  main () at stream.c:320
> >
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