From: Ingo Molnar <mingo@elte.hu>
To: Vegard Nossum <vegard.nossum@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Arjan van de Ven <arjan@linux.intel.com>,
Andi Kleen <andi@firstfloor.org>,
Pekka Enberg <penberg@cs.helsinki.fi>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RESEND][PATCH] x86: don't destroy %rbp on kernel-mode faults
Date: Fri, 27 Jun 2008 17:46:07 +0200 [thread overview]
Message-ID: <20080627154607.GA15718@elte.hu> (raw)
In-Reply-To: <20080627152216.GA8852@damson.getinternet.no>
* Vegard Nossum <vegard.nossum@gmail.com> wrote:
> >From the code:
>
> "B stepping K8s sometimes report an truncated RIP for IRET exceptions
> returning to compat mode. Check for these here too."
>
> The code then proceeds to truncate the upper 32 bits of %rbp. This means
> that when do_page_fault() is finally called, its prologue,
>
> do_page_fault:
> push %rbp
> movl %rsp, %rbp
>
> will put the truncated base pointer on the stack. This means that the
> stack tracer will not be able to follow the base-pointer changes and
> will see all subsequent stack frames as unreliable.
>
> This patch changes the code to use a different register (%rcx) for the
> checking and leaves %rbp untouched.
applied to tip/x86/debug - thanks Vegard!
Ingo
next prev parent reply other threads:[~2008-06-27 15:46 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-06-27 15:22 [RESEND][PATCH] x86: don't destroy %rbp on kernel-mode faults Vegard Nossum
2008-06-27 15:46 ` Ingo Molnar [this message]
2008-06-27 16:12 ` Andi Kleen
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