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

[Harald Servat]

On 10/10/2015 08:00 PM, Arun Sharma wrote:
> On Thu, Oct 8, 2015 at 3:40 AM, Harald Servat <address@hidden> wrote:
> > 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?
>
> I'm not experienced with ARM. But here's what I'd do:

First of all, thank you for the pointers Arun.

> Run with UNW_DEBUG_LEVEL=n (list archives have more info) and get a
> trace that shows why dwarf_step() failed.

That generated lots of outputs. You can get it from

  https://www.dropbox.com/s/vl8p5ep0kypa9dh/libunwind-debug.txt?dl=0

> Recognizing signal frames using instruction signature matching such
> as: 0xE92DD800 is fragile and error prone. If the libc you're using
> has the right CFI annotation around the signal handler ('S' character
> in the CIE augmentation), you'll probably end up with more reliable
> stack unwinding.

  After looking at the output that I shared, I'm afraid that CFI 
annotation is only available on some libraries because I only see some

parse_cie: CIE parsed OK, augmentation = "S", handler=0x0

  should I ask my sysadmins to install any libc package in particular?

Again, thank you!!


>   -Arun
>
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