Re: [PATCH 2/2] x86/uprobes: implement x86 specificarch_uprobe_*_step

From: Ananth N Mavinakayanahalli
Date: Thu Aug 02 2012 - 00:58:36 EST


On Wed, Aug 01, 2012 at 03:43:37PM +0200, Oleg Nesterov wrote:

...

> However, I am not sure we can trust it. We are in kernel mode,
> DEBUGCTLMSR_BTF can be cleared by kprobes (Ananth, please correct me).
> I think we need to check TIF_BLOCKSTEP.

Kprobes resets DEBUGCTLMSR_BTF only if we have to single-step in
hardware. It puts the flag back if TIF_BLOCKSTEP is set, after the
single-step is complete; so yes, a better check is TIF_BLOCKSTEP.

Ananth

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