linux-kernel - Re: [PATCH v2 4/4] uprobes/powerpc: Make use of generic routines to enable single step

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Date:	Fri, 14 Dec 2012 21:02:41 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	"Suzuki K. Poulose" <suzuki@...ibm.com>
Cc:	bigeasy@...utronix.de, ananth@...ibm.com,
	srikar@...ux.vnet.ibm.com, peterz@...radead.org,
	benh@...nel.crashing.org, mingo@...e.hu, anton@...hat.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/4] uprobes/powerpc: Make use of generic routines
	to enable single step

On 12/03, Suzuki K. Poulose wrote:
>
> Replace the ptrace helpers with the powerpc generic routines to
> enable/disable single step. We save/restore the MSR (and DCBR for BookE)
> across for the operation. We don't have to disable the single step,
> as restoring the MSR/DBCR would restore the previous state.

Obviously I can't review this series (although it looks fine to me).

Just one note,

> @@ -121,7 +132,7 @@ int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
>
>  	WARN_ON_ONCE(current->thread.trap_nr != UPROBE_TRAP_NR);
>
> -	uprobe_restore_context_sstep(&utask->autask);
> +	uprobe_restore_context_sstep(&utask->autask, regs);

I am not sure ppc needs this, but note that x86 does a bit more.

Not only we need to restore the "single-step" state, we need to
send SIGTRAP if it was not set by us. The same for _skip_sstep.

But even if I am right I do not suggest to change this series,
this can be done as a separate patch.

Oleg.

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