linux-kernel - Re: [PATCH] arm: Add unwinding annotations for 64bit division functions

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Date:	Thu, 22 Sep 2011 08:28:08 +0100
From:	"Jon Medhurst (Tixy)" <jon.medhurst@...aro.org>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Dave Martin <dave.martin@...aro.org>,
	Laura Abbott <lauraa@...eaurora.org>,
	Nicolas Pitre <nico@...xnic.net>,
	Catalin Marinas <catalin.marinas@....com>,
	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] arm: Add unwinding annotations for 64bit division
 functions

On Wed, 2011-09-21 at 12:55 +0100, Russell King - ARM Linux wrote:
> Instructions such as VFP, kprobes tracing, etc are expected fault
> locations, and those are fairly well controlled where they can be placed.
> With things like ftrace, it certainly is the case that the unwinder can
> theoretically be called from almost anywhere in a function.

Actually, kprobes can be places on any instruction in the kernel that
isn't in the section .kprobes.text.

I also strongly suspect that stack unwinding won't happen correctly
across the boundary between the kprobes handling code and the function
which was probed - there's an awful lot of stack jiggery pokery going on
there.

-- 
Tixy

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