From: Andrew Haley <aph@redhat.com>
To: Jan Kratochvil <jan.kratochvil@redhat.com>
Cc: gcc@gcc.gnu.org, libc-alpha@sources.redhat.com,
gdb@sourceware.org, Jakub Jelinek <jakub@redhat.com>,
Richard Henderson <rth@redhat.com>
Subject: Re: Unwinding CFI gcc practice of assumed `same value' regs
Date: Tue, 12 Dec 2006 13:55:00 -0000 [thread overview]
Message-ID: <17790.46246.634400.638852@zebedee.pink> (raw)
In-Reply-To: <20061211190300.GA4372@host0.dyn.jankratochvil.net>
Jan Kratochvil writes:
> currently (on x86_64) the gdb backtrace does not properly stop at
> the outermost frame:
>
> #3 0x00000036ddb0610a in start_thread () from /lib64/tls/libpthread.so.0
> #4 0x00000036dd0c68c3 in clone () from /lib64/tls/libc.so.6
> #5 0x0000000000000000 in ?? ()
>
> Currently it relies only on clearing %rbp (0x0000000000000000 above is
> unrelated to it, it got read from uninitialized memory).
That's how it's defined to work: %rbp is zero.
> http://sourceware.org/ml/gdb/2004-08/msg00060.html suggests frame
> pointer 0x0 should be enough for a debugger not finding CFI to stop
> unwinding, still it is a heuristic.
Not by my understanding it isn't. It's set up by the runtime system,
and 0 (i.e. NULL on x86-64) marks the end of the stack. Officially.
See page 28, AMD64 ABI Draft 0.98 \u2013 September 27, 2006 -- 9:24.
Andrew.
next prev parent reply other threads:[~2006-12-12 13:55 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-12-11 19:03 Jan Kratochvil
2006-12-11 22:40 ` Roland McGrath
2006-12-12 15:54 ` Jakub Jelinek
2006-12-12 13:55 ` Andrew Haley [this message]
2006-12-12 14:55 ` Mark Kettenis
2006-12-12 15:04 ` Andrew Haley
2006-12-12 15:21 ` Ulrich Drepper
2006-12-12 15:26 ` Andrew Haley
2006-12-12 15:39 ` Ulrich Drepper
2006-12-13 18:11 ` Michael Matz
2006-12-12 15:50 ` Jan Kratochvil
2006-12-12 16:19 ` Jakub Jelinek
2006-12-12 16:55 ` Ian Lance Taylor
2006-12-12 17:06 ` Andrew Haley
2006-12-12 17:34 ` Mark Kettenis
2006-12-13 18:02 ` Michael Matz
2006-12-13 18:10 ` Michael Matz
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