linux-kernel - Re: [PATCH v3 1/2] kprobes: introduce weak arch_check_ftrace

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Message-ID: <544627D0.60309@hitachi.com>
Date:	Tue, 21 Oct 2014 18:30:56 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Heiko Carstens <heiko.carstens@...ibm.com>
Cc:	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
	"David S. Miller" <davem@...emloft.net>,
	Ingo Molnar <mingo@...hat.com>,
	Vojtech Pavlik <vojtech@...e.cz>,
	Jiri Kosina <jkosina@...e.cz>, Jiri Slaby <jslaby@...e.cz>,
	Steven Rostedt <rostedt@...dmis.org>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/2] kprobes: introduce weak arch_check_ftrace_location()
 helper function

(2014/10/21 17:30), Heiko Carstens wrote:
> Introduce weak arch_check_ftrace_location() helper function which
> architectures can override in order to implement handling of kprobes
> on function tracer call sites on their own, without depending on
> common code or implementing the KPROBES_ON_FTRACE feature.
> 
> Signed-off-by: Heiko Carstens <heiko.carstens@...ibm.com>

Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>

Thanks!

> ---
>  include/linux/kprobes.h |  1 +
>  kernel/kprobes.c        | 18 +++++++++++-------
>  2 files changed, 12 insertions(+), 7 deletions(-)
> 
> diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
> index f7296e57d614..5297f9fa0ef2 100644
> --- a/include/linux/kprobes.h
> +++ b/include/linux/kprobes.h
> @@ -335,6 +335,7 @@ extern void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
>  extern int arch_prepare_kprobe_ftrace(struct kprobe *p);
>  #endif
>  
> +int arch_check_ftrace_location(struct kprobe *p);
>  
>  /* Get the kprobe at this addr (if any) - called with preemption disabled */
>  struct kprobe *get_kprobe(void *addr);
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index 3995f546d0f3..317eb8ad28dd 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -1410,16 +1410,10 @@ static inline int check_kprobe_rereg(struct kprobe *p)
>  	return ret;
>  }
>  
> -static int check_kprobe_address_safe(struct kprobe *p,
> -				     struct module **probed_mod)
> +int __weak arch_check_ftrace_location(struct kprobe *p)
>  {
> -	int ret = 0;
>  	unsigned long ftrace_addr;
>  
> -	/*
> -	 * If the address is located on a ftrace nop, set the
> -	 * breakpoint to the following instruction.
> -	 */
>  	ftrace_addr = ftrace_location((unsigned long)p->addr);
>  	if (ftrace_addr) {
>  #ifdef CONFIG_KPROBES_ON_FTRACE
> @@ -1431,7 +1425,17 @@ static int check_kprobe_address_safe(struct kprobe *p,
>  		return -EINVAL;
>  #endif
>  	}
> +	return 0;
> +}
>  
> +static int check_kprobe_address_safe(struct kprobe *p,
> +				     struct module **probed_mod)
> +{
> +	int ret;
> +
> +	ret = arch_check_ftrace_location(p);
> +	if (ret)
> +		return ret;
>  	jump_label_lock();
>  	preempt_disable();
>  
> 


-- 
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com


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