linux-kernel - Re: [PATCH] x86/hw_breakpoints, kprobes: Remove kprobes ifdeffery

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Message-Id: <20190128225730.557ab61746fea62d3f85f584@kernel.org>
Date:   Mon, 28 Jan 2019 22:57:30 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     X86 ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Frederic Weisbecker <frederic@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] x86/hw_breakpoints, kprobes: Remove kprobes ifdeffery

On Sun, 27 Jan 2019 14:12:37 +0100
Borislav Petkov <bp@...en8.de> wrote:

> From: Borislav Petkov <bp@...e.de>
> 
> Remove the ifdeffery in the breakpoint parsing arch_build_bp_info() by
> adding a within_kprobe_blacklist() stub for the !CONFIG_KPROBES case.
> 
> It is returning true when kprobes are not enabled to mean that any
> address is within the kprobes blacklist on such kernels and thus not
> allow kernel breakpoints on non-kprobes kernels.
> 

This looks good to me.

Acked-by: Masami Hiramatsu <mhiramat@...nel.org>

Thank you Borislav!!

> Signed-off-by: Borislav Petkov <bp@...e.de>
> Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Frederic Weisbecker <frederic@...nel.org>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Masami Hiramatsu <mhiramat@...nel.org>
> Cc: "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> ---
>  arch/x86/kernel/hw_breakpoint.c | 4 ----
>  include/linux/kprobes.h         | 5 +++++
>  2 files changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/kernel/hw_breakpoint.c b/arch/x86/kernel/hw_breakpoint.c
> index 7d6f91f2869a..ff9bfd40429e 100644
> --- a/arch/x86/kernel/hw_breakpoint.c
> +++ b/arch/x86/kernel/hw_breakpoint.c
> @@ -261,12 +261,8 @@ static int arch_build_bp_info(struct perf_event *bp,
>  		 * allow kernel breakpoints at all.
>  		 */
>  		if (attr->bp_addr >= TASK_SIZE_MAX) {
> -#ifdef CONFIG_KPROBES
>  			if (within_kprobe_blacklist(attr->bp_addr))
>  				return -EINVAL;
> -#else
> -			return -EINVAL;
> -#endif
>  		}
>  
>  		hw->type = X86_BREAKPOINT_EXECUTE;
> diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
> index e07e91daaacc..201f0f2683f2 100644
> --- a/include/linux/kprobes.h
> +++ b/include/linux/kprobes.h
> @@ -442,6 +442,11 @@ static inline int enable_kprobe(struct kprobe *kp)
>  {
>  	return -ENOSYS;
>  }
> +
> +static inline bool within_kprobe_blacklist(unsigned long addr)
> +{
> +	return true;
> +}
>  #endif /* CONFIG_KPROBES */
>  static inline int disable_kretprobe(struct kretprobe *rp)
>  {
> -- 
> 2.19.1
> 


-- 
Masami Hiramatsu <mhiramat@...nel.org>