linux-kernel - Re: [PATCH 1/3] x86/perf/hw_breakpoint: Disallow kernel breakpoints unless kprobe-safe

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Date:	Tue, 1 Sep 2015 13:41:20 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	平松雅巳 / HIRAMATU，MASAMI 
	<masami.hiramatsu.pt@...achi.com>,
	Andy Lutomirski <luto@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Brian Gerst <brgerst@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Borislav Petkov <bp@...en8.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	X86 ML <x86@...nel.org>
Subject: Re: [PATCH 1/3] x86/perf/hw_breakpoint: Disallow kernel breakpoints
 unless kprobe-safe

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;
--
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