linux-kernel - Re: [PATCH v5 7/14] x86 support for Uprobes

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Message-ID: <20100614175423.GG23754@infradead.org>
Date:	Mon, 14 Jun 2010 13:54:23 -0400
From:	Christoph Hellwig <hch@...radead.org>
To:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Mel Gorman <mel@....ul.ie>,
	Randy Dunlap <rdunlap@...otime.net>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Roland McGrath <roland@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Christoph Hellwig <hch@...radead.org>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Mark Wielaard <mjw@...hat.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jim Keniston <jkenisto@...ux.vnet.ibm.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	"Frank Ch. Eigler" <fche@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [PATCH v5 7/14] x86 support for Uprobes

On Mon, Jun 14, 2010 at 01:59:13PM +0530, Srikar Dronamraju wrote:
> @@ -850,7 +850,19 @@ do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags)
>  
>  	if (thread_info_flags & _TIF_UPROBE) {
>  		clear_thread_flag(TIF_UPROBE);
> +#ifdef CONFIG_X86_32
> +		/*
> +		 * On x86_32, do_notify_resume() gets called with
> +		 * interrupts disabled. Hence enable interrupts if they
> +		 * are still disabled.
> +		 */
> +		native_irq_enable();
> +#endif
>  		uprobe_notify_resume(regs);
> +
> +#ifdef CONFIG_X86_32
> +		native_irq_disable();
> +#endif

I'm no x86 port guru, but this looks rather worriesome to me.  Why does
do_notify_resume have different calling conventions on 32 vs 64-bit?
And if there is a good reason that 32-bit has them disabled, why is
enabling them in the middle of do_notify_resume okay?

> +void arch_uprobe_disable_sstep(struct pt_regs *regs)
> +{
> +		/* Disable single-stepping by clearing what we set */
> +		clear_thread_flag(TIF_SINGLESTEP);
> +		clear_thread_flag(TIF_FORCED_TF);
> +		regs->flags &= ~X86_EFLAGS_TF;
> +}

This seems to have one layer of indentation too much.
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