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Date: Fri, 15 Jul 2011 13:42:32 -0500
From: Scott Wood <scottwood@freescale.com>
To: tiejun.chen <tiejun.chen@windriver.com>
Subject: Re: [v3 PATCH 1/1] booke/kprobe: make program exception to use one
	dedicated exception stack
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On Fri, 15 Jul 2011 13:28:15 +0800
tiejun.chen <tiejun.chen@windriver.com> wrote:

> Kumar Gala wrote:
> > I'm still very confused why we need a unique stack frame for kprobe/program exceptions on book-e devices.
> 
> Its a bug at least for Book-E.

But why only booke?  There's nothing booke-specific about the stwu
instruction.

> And if you'd like to check another topic thread,
> "[BUG?]3.0-rc4+ftrace+kprobe: set kprobe at instruction 'stwu' lead to system
> crash/freeze", you can know this story completely :)
> 
> This bug should not be reproduced on PPC64 with the exception prolog/endlog
> dedicated to PPC64.

What if the function you're stepping through is creating a stack frame that
is larger than the 288 bytes that get skipped?

> But I have no enough time to check other PPC32 & !BOOKE so
> I'm not sure if we should extend this modification.

Someone should.

-Scott