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

[Ken Werner]

On 08/19/2011 04:53 PM, Ken Werner wrote:
> On 08/19/2011 02:39 PM, Sven Neumann wrote:
> > Now I've updated libunwind to 1.0-rc1 and this trick doesn't seem to
> > work any longer. The code appears to crash in libunwind if used as
> > above. I had a look at the ARM implementation and found that there is
> > now code that's supposed to unw_step a signal handler. So I tried
> > without our hack and just use unw_getcontext(). Now it doesn't crash any
> > longer, but it also doesn't unwind over the signal handler. All I get is
> > a stack trace like this:
> >
> > 0x4016cde0 logUnwind() from /usr/lib/libraumfeld-1.0.so.0
> > 0x40205654 ?? from /usr/lib/libunwind.so.7
> >
> > Any ideas what we could do?
>
> Hmm, this is interesting. How does your system look like (which libc,
> kernel version) and are you stepping over RT or non-RT signal frames? It
> would be helpful if you could share some code that shows the described
> behavior.
> In the meanwhile I'll prepare a simple testcase where I'll verify that
> it's working on my system.

Attached is a simple testcase that works on my PandaBoard. How does it 
look on your system? The output should look like this:
  standard frame        ip:     0x8988, sp: 0xbeffadd0   sig_handler
  signal frame  ip: 0x40113740, sp: 0xbefff2f0   __default_rt_sa_restorer_v2
  standard frame        ip:     0x8c4e, sp: 0xbefff660   main
  standard frame        ip: 0x40104623, sp: 0xbefff668   __libc_start_main
  standard frame        ip:     0x88b7, sp: 0xbefff7a8   _start

The ARMv7 board runs a Linaro evaluation build with a fairly recent 
Linux kernel and glibc (www.linaro.org/downloads).

Regards
Ken

PS: I'll be on vacation for a few days starting tomorrow - bad timing. 
But I'll follow the discussion afterwards.

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