linux-kernel - Re: [PATCH 2/4] uprobes/powerpc: Do not use arch_uprobe_*

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Message-ID: <20121102050350.GE11125@linux.vnet.ibm.com>
Date:	Fri, 2 Nov 2012 10:33:50 +0530
From:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Anton Arapov <anton@...hat.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Rabin Vincent <rabin@....in>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] uprobes/powerpc: Do not use arch_uprobe_*_step()
 helpers

* Oleg Nesterov <oleg@...hat.com> [2012-10-28 18:39:28]:

> No functional changes.
> 
> powerpc is the only user of arch_uprobe_enable/disable_step() helpers,
> but they should die. They can not be used correctly, every arch needs
> its own implementation (like x86 does). And they do not really help
> even as initial-and-almost-working code, arch_uprobe_*_xol() hooks can
> easily use user_enable/disable_single_step() directly.
> 
> Change arch_uprobe_*_step() to do nothing, and convert powerpc to use
> ptrace helpers. This is equally wrong, powerpc needs the arch-specific
> fixes.
> 
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>


Acked-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>

> ---
>  arch/powerpc/kernel/uprobes.c |    6 ++++++
>  kernel/events/uprobes.c       |    2 --
>  2 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/uprobes.c b/arch/powerpc/kernel/uprobes.c
> index d2d46d1..bc77834 100644
> --- a/arch/powerpc/kernel/uprobes.c
> +++ b/arch/powerpc/kernel/uprobes.c
> @@ -64,6 +64,8 @@ int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
>  	autask->saved_trap_nr = current->thread.trap_nr;
>  	current->thread.trap_nr = UPROBE_TRAP_NR;
>  	regs->nip = current->utask->xol_vaddr;
> +
> +	user_enable_single_step(current);
>  	return 0;
>  }
> 
> @@ -119,6 +121,8 @@ int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
>  	 * to be executed.
>  	 */
>  	regs->nip = utask->vaddr + MAX_UINSN_BYTES;
> +
> +	user_disable_single_step(current);
>  	return 0;
>  }
> 
> @@ -162,6 +166,8 @@ void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
> 
>  	current->thread.trap_nr = utask->autask.saved_trap_nr;
>  	instruction_pointer_set(regs, utask->vaddr);
> +
> +	user_disable_single_step(current);
>  }
> 
>  /*
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index 672227a..916391e 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -1432,12 +1432,10 @@ static struct uprobe *find_active_uprobe(unsigned long bp_vaddr, int *is_swbp)
> 
>  void __weak arch_uprobe_enable_step(struct arch_uprobe *arch)
>  {
> -	user_enable_single_step(current);
>  }
> 
>  void __weak arch_uprobe_disable_step(struct arch_uprobe *arch)
>  {
> -	user_disable_single_step(current);
>  }
> 
>  /*
> -- 
> 1.5.5.1
> 

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