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Date: Tue, 1 Sep 2015 13:41:20 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Frederic Weisbecker <fweisbec@gmail.com>
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        Linus Torvalds <torvalds@linux-foundation.org>,
        X86 ML <x86@kernel.org>
Subject: Re: [PATCH 1/3] x86/perf/hw_breakpoint: Disallow kernel breakpoints
 unless kprobe-safe
Message-ID: <20150901114120.GN18673@twins.programming.kicks-ass.net>
References: <cover.1438312874.git.luto@kernel.org>
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 <20150804155158.GB32738@lerouge>
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On Tue, Sep 01, 2015 at 01:36:08PM +0200, Peter Zijlstra wrote:
> +static inline bool kprobe_blacklisted(unsigned long addr)
> +{
> +	return false;

Ah, I think that wants to be true instead, to match the below comment.

> +}
> +
>  static inline int kprobes_built_in(void)
>  {
>  	return 0;
> diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c
> index 92ce5f4ccc26..7c08e6d1175c 100644
> --- a/kernel/events/hw_breakpoint.c
> +++ b/kernel/events/hw_breakpoint.c
> @@ -384,6 +384,14 @@ static int validate_hw_breakpoint(struct perf_event *bp)
>  		 */
>  		if (!capable(CAP_SYS_ADMIN))
>  			return -EPERM;
> +
> +		/*
> +		 * We don't allow kernel breakpoints in places that are not
> +		 * acceptable for kprobes.  On non-kprobes kernels, we don't
> +		 * allow kernel breakpoints at all.
> +		 */
> +		if (kprobe_blacklisted(bp->attr.bp_addr))
> +			return -EINVAL;
>  	}
>  
>  	return 0;