linux-kernel - Re: [PATCH 3/9] uprobes: allow ignoring of probe hits

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Message-ID: <20121015165218.GA10239@redhat.com>
Date:	Mon, 15 Oct 2012 18:52:18 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Rabin Vincent <rabin@....in>
Cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Peter Zijlstra <peterz@...radead.org>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Subject: Re: [PATCH 3/9] uprobes: allow ignoring of probe hits

On 10/14, Rabin Vincent wrote:
>
> Allow arches to decided to ignore a probe hit.  ARM will use this to
> only call handlers if the conditions to execute a conditionally executed
> instruction are satisfied.

Not sure I understand why we shouldn't call handlers in this case,
but OK, I know nothing about arm.

>  static struct uprobe *find_active_uprobe(unsigned long bp_vaddr, int *is_swbp)
>  {
>  	struct mm_struct *mm = current->mm;
> @@ -1469,6 +1474,7 @@ static void handle_swbp(struct pt_regs *regs)
>  	struct uprobe *uprobe;
>  	unsigned long bp_vaddr;
>  	int uninitialized_var(is_swbp);
> +	bool ignored = false;
>  
>  	bp_vaddr = uprobe_get_swbp_addr(regs);
>  	uprobe = find_active_uprobe(bp_vaddr, &is_swbp);
> @@ -1499,6 +1505,12 @@ static void handle_swbp(struct pt_regs *regs)
>  			goto cleanup_ret;
>  	}
>  	utask->active_uprobe = uprobe;
> +
> +	if (arch_uprobe_ignore(&uprobe->arch, regs)) {
> +		ignored = true;
> +		goto cleanup_ret;
> +	}
> +
>  	handler_chain(uprobe, regs);
>  	if (uprobe->flags & UPROBE_SKIP_SSTEP && can_skip_sstep(uprobe, regs))
>  		goto cleanup_ret;
> @@ -1514,7 +1526,7 @@ cleanup_ret:
>  		utask->active_uprobe = NULL;
>  		utask->state = UTASK_RUNNING;
>  	}
> -	if (!(uprobe->flags & UPROBE_SKIP_SSTEP))
> +	if (!ignored && !(uprobe->flags & UPROBE_SKIP_SSTEP))
>  
>  		/*
>  		 * cannot singlestep; cannot skip instruction;

This conflicts with other changes in

	git://git.kernel.org/pub/scm/linux/kernel/git/oleg/misc uprobes/core

Could you re-diff?

I'll try to read 1-7 tomorrow.

Oleg.

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