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Date: Fri, 7 Jul 2017 08:37:45 +0300
From: Konstantin Belousov <kostikbel@gmail.com>
To: Conrad Meyer <cem@freebsd.org>, Marc Branchaud <marcnarc@xiplink.com>,
 "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org>
Subject: Re: libexecinfo backtrace() in a signal handler
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On Fri, Jul 07, 2017 at 01:16:22AM +0200, Joerg Sonnenberger wrote:
> On Thu, Jul 06, 2017 at 03:58:04PM -0700, Conrad Meyer wrote:
> > Signal handlers use a special stack frame that libexecinfo is too
> > simple to understand.  To get a stack from a signal handler, you might
> > want to use libunwind instead.
> 
> Actually, that's not the problem. The problem is that nothing registers
> the necessary unwind data.

Actually, that's not the problem.  Libunwind port on FreeBSD knows how
to detect signal trampolines, either with the direct help from kernel,
or using some heuristic by parsing instructions, on (much) older kernels.