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Message-ID: <20070619084116.GA1663@elte.hu>
Date: Tue, 19 Jun 2007 10:41:16 +0200
From: Ingo Molnar <mingo@...e.hu>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Thomas Gleixner <tglx@...utronix.de>,
LKML <linux-kernel@...r.kernel.org>,
RT <linux-rt-users@...r.kernel.org>
Subject: Re: [PATCH RT] Don't call mcount from vsyscall_fn's
* Steven Rostedt <rostedt@...dmis.org> wrote:
> This bit me in the butt.
>
> I couldn't understand why my init app was segfaulting, with a kernel
> address, but a user RIP and RSP. Well, the RIP I think was bogus, but
> the kernel address was always the start of "mcount". Looking deeper,
> I printed out what was in the RSP (even though it was a user stack).
> It ended up showing me that the calling address was from the VDSO
> area. Looking even further, I found the offending culprit, which was
> vread_hpet.
>
> Looking at the assembly dump, I saw the vread_hpet was calling mcount,
> but I could not see it in the code. Nor could I see it in hpet.i (-E
> option of compiling).
>
> Well, I guess Ingo is a magician when it comes to compiler tricks, and
> has the mcount being called by "every!!" function, unless you add the
> "notrace" option.
>
> This patch adds the notrace to vsyscall_fn, so that we don't have user
> land apps calling mcount and crashing!
doh - applied. Thanks!
Ingo
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