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From: Mark Kettenis <kettenis@chello.nl>
To: Richard Henderson <rth@twiddle.net>
Cc: David.Mosberger@acm.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] fix vsyscall unwind information
Date: 06 May 2003 01:10:37 +0200	[thread overview]
Message-ID: <86d6ixdm6q.fsf@elgar.kettenis.dyndns.org> (raw)
In-Reply-To: Richard Henderson's message of "Mon, 5 May 2003 09:34:44 -0700"

Richard Henderson <rth@twiddle.net> writes:

> On Mon, May 05, 2003 at 08:05:58AM -0700, David Mosberger-Tang wrote:
> >   Richard> Why?  Certainly it isn't needed for x86.
> > 
> > Certain applications (such as debuggers) want to know.  Sure, you can
> > do symbol matching (if you have the symbol table) or code-reading
> > (assuming you know the exact sigreturn sequence), but having a marker
> > would be more reliable and faster.
> 
> Eh.  The whole point was to *eliminate* the special cases.
> 
> If the debugger does nothing special now, it'll see the symbol
> from the VDSO in the backtrace and print __kernel_sigreturn.
> Isn't this sufficient for the user to recognize what's going on?
> Does it really need to print <signal frame>?

Unfortunately, GDB needs to be able to recognize signal trampolines in
order to be able to single step correctly when a signal arrives.  At
least on some platforms.  Could be that the code-path in question
isn't used for Linux/i386, but I vaguely remember it does.

Anyway, signal trampolines could be marked with a special augmentation
in their CIE.

Mark

  parent reply	other threads:[~2003-05-05 22:58 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20030502004014$08e2@gated-at.bofh.it>
     [not found] ` <20030503210015$292c@gated-at.bofh.it>
     [not found]   ` <20030504063010$279f@gated-at.bofh.it>
2003-05-05  6:49     ` David Mosberger-Tang
2003-05-05  7:42       ` Richard Henderson
2003-05-05 15:05         ` David Mosberger-Tang
2003-05-05 16:34           ` Richard Henderson
2003-05-05 16:55             ` David Mosberger-Tang
2003-05-05 23:10             ` Mark Kettenis [this message]
2003-05-06  0:21               ` Richard Henderson
2003-05-06  6:16                 ` David Mosberger-Tang
2003-05-02  0:33 [PATCH] i386 vsyscall DSO implementation, take 2 Roland McGrath
2003-05-03 20:51 ` Richard Henderson
2003-05-04  6:21   ` [PATCH] fix vsyscall unwind information Richard Henderson
2003-05-04  7:34     ` Ulrich Drepper

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