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Message-Id: <20201106192513.80b330351c0cafd03134b0d1@kernel.org>
Date:   Fri, 6 Nov 2020 19:25:13 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Steven Rostedt (VMware) <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Jiri Kosina <jikos@...nel.org>,
        Miroslav Benes <mbenes@...e.cz>,
        Petr Mladek <pmladek@...e.com>, Guo Ren <guoren@...nel.org>,
        "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
        Helge Deller <deller@....de>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        linux-csky@...r.kernel.org, linux-parisc@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org
Subject: Re: [PATCH 05/11 v3] kprobes/ftrace: Add recursion protection to
 the ftrace callback

On Thu, 05 Nov 2020 21:32:40 -0500
Steven Rostedt (VMware) <rostedt@...dmis.org> wrote:

> From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>
> 
> If a ftrace callback does not supply its own recursion protection and
> does not set the RECURSION_SAFE flag in its ftrace_ops, then ftrace will
> make a helper trampoline to do so before calling the callback instead of
> just calling the callback directly.
> 
> The default for ftrace_ops is going to change. It will expect that handlers
> provide their own recursion protection, unless its ftrace_ops states
> otherwise.
> 
> Link: https://lkml.kernel.org/r/20201028115613.140212174@goodmis.org
> 

Looks good to me.

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

Thank you!

> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Masami Hiramatsu <mhiramat@...nel.org>
> Cc: Guo Ren <guoren@...nel.org>
> Cc: "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>
> Cc: Helge Deller <deller@....de>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: Heiko Carstens <hca@...ux.ibm.com>
> Cc: Vasily Gorbik <gor@...ux.ibm.com>
> Cc: Christian Borntraeger <borntraeger@...ibm.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: x86@...nel.org
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>
> Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: linux-csky@...r.kernel.org
> Cc: linux-parisc@...r.kernel.org
> Cc: linuxppc-dev@...ts.ozlabs.org
> Cc: linux-s390@...r.kernel.org
> Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
> ---
> 
> Changes since v2:
> 
>  - Move get_kprobe() into preempt disabled sections for various archs
> 
> 
>  arch/csky/kernel/probes/ftrace.c     | 12 ++++++++++--
>  arch/parisc/kernel/ftrace.c          | 16 +++++++++++++---
>  arch/powerpc/kernel/kprobes-ftrace.c | 11 ++++++++++-
>  arch/s390/kernel/ftrace.c            | 16 +++++++++++++---
>  arch/x86/kernel/kprobes/ftrace.c     | 12 ++++++++++--
>  5 files changed, 56 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/csky/kernel/probes/ftrace.c b/arch/csky/kernel/probes/ftrace.c
> index 5264763d05be..5eb2604fdf71 100644
> --- a/arch/csky/kernel/probes/ftrace.c
> +++ b/arch/csky/kernel/probes/ftrace.c
> @@ -13,16 +13,21 @@ int arch_check_ftrace_location(struct kprobe *p)
>  void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
>  			   struct ftrace_ops *ops, struct pt_regs *regs)
>  {
> +	int bit;
>  	bool lr_saver = false;
>  	struct kprobe *p;
>  	struct kprobe_ctlblk *kcb;
>  
> -	/* Preempt is disabled by ftrace */
> +	bit = ftrace_test_recursion_trylock();
> +	if (bit < 0)
> +		return;
> +
> +	preempt_disable_notrace();
>  	p = get_kprobe((kprobe_opcode_t *)ip);
>  	if (!p) {
>  		p = get_kprobe((kprobe_opcode_t *)(ip - MCOUNT_INSN_SIZE));
>  		if (unlikely(!p) || kprobe_disabled(p))
> -			return;
> +			goto out;
>  		lr_saver = true;
>  	}
>  
> @@ -56,6 +61,9 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
>  		 */
>  		__this_cpu_write(current_kprobe, NULL);
>  	}
> +out:
> +	preempt_enable_notrace();
> +	ftrace_test_recursion_unlock(bit);
>  }
>  NOKPROBE_SYMBOL(kprobe_ftrace_handler);
>  
> diff --git a/arch/parisc/kernel/ftrace.c b/arch/parisc/kernel/ftrace.c
> index 63e3ecb9da81..13d85042810a 100644
> --- a/arch/parisc/kernel/ftrace.c
> +++ b/arch/parisc/kernel/ftrace.c
> @@ -207,14 +207,21 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
>  			   struct ftrace_ops *ops, struct pt_regs *regs)
>  {
>  	struct kprobe_ctlblk *kcb;
> -	struct kprobe *p = get_kprobe((kprobe_opcode_t *)ip);
> +	struct kprobe *p;
> +	int bit;
>  
> -	if (unlikely(!p) || kprobe_disabled(p))
> +	bit = ftrace_test_recursion_trylock();
> +	if (bit < 0)
>  		return;
>  
> +	preempt_disable_notrace();
> +	p = get_kprobe((kprobe_opcode_t *)ip);
> +	if (unlikely(!p) || kprobe_disabled(p))
> +		goto out;
> +
>  	if (kprobe_running()) {
>  		kprobes_inc_nmissed_count(p);
> -		return;
> +		goto out;
>  	}
>  
>  	__this_cpu_write(current_kprobe, p);
> @@ -235,6 +242,9 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
>  		}
>  	}
>  	__this_cpu_write(current_kprobe, NULL);
> +out:
> +	preempt_enable_notrace();
> +	ftrace_test_recursion_unlock(bit);
>  }
>  NOKPROBE_SYMBOL(kprobe_ftrace_handler);
>  
> diff --git a/arch/powerpc/kernel/kprobes-ftrace.c b/arch/powerpc/kernel/kprobes-ftrace.c
> index 972cb28174b2..5df8d50c65ae 100644
> --- a/arch/powerpc/kernel/kprobes-ftrace.c
> +++ b/arch/powerpc/kernel/kprobes-ftrace.c
> @@ -18,10 +18,16 @@ void kprobe_ftrace_handler(unsigned long nip, unsigned long parent_nip,
>  {
>  	struct kprobe *p;
>  	struct kprobe_ctlblk *kcb;
> +	int bit;
>  
> +	bit = ftrace_test_recursion_trylock();
> +	if (bit < 0)
> +		return;
> +
> +	preempt_disable_notrace();
>  	p = get_kprobe((kprobe_opcode_t *)nip);
>  	if (unlikely(!p) || kprobe_disabled(p))
> -		return;
> +		goto out;
>  
>  	kcb = get_kprobe_ctlblk();
>  	if (kprobe_running()) {
> @@ -52,6 +58,9 @@ void kprobe_ftrace_handler(unsigned long nip, unsigned long parent_nip,
>  		 */
>  		__this_cpu_write(current_kprobe, NULL);
>  	}
> +out:
> +	preempt_enable_notrace();
> +	ftrace_test_recursion_unlock(bit);
>  }
>  NOKPROBE_SYMBOL(kprobe_ftrace_handler);
>  
> diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c
> index b388e87a08bf..8f31c726537a 100644
> --- a/arch/s390/kernel/ftrace.c
> +++ b/arch/s390/kernel/ftrace.c
> @@ -201,14 +201,21 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
>  		struct ftrace_ops *ops, struct pt_regs *regs)
>  {
>  	struct kprobe_ctlblk *kcb;
> -	struct kprobe *p = get_kprobe((kprobe_opcode_t *)ip);
> +	struct kprobe *p;
> +	int bit;
>  
> -	if (unlikely(!p) || kprobe_disabled(p))
> +	bit = ftrace_test_recursion_trylock();
> +	if (bit < 0)
>  		return;
>  
> +	preempt_disable_notrace();
> +	p = get_kprobe((kprobe_opcode_t *)ip);
> +	if (unlikely(!p) || kprobe_disabled(p))
> +		goto out;
> +
>  	if (kprobe_running()) {
>  		kprobes_inc_nmissed_count(p);
> -		return;
> +		goto out;
>  	}
>  
>  	__this_cpu_write(current_kprobe, p);
> @@ -228,6 +235,9 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
>  		}
>  	}
>  	__this_cpu_write(current_kprobe, NULL);
> +out:
> +	preempt_enable_notrace();
> +	ftrace_test_recursion_unlock(bit);
>  }
>  NOKPROBE_SYMBOL(kprobe_ftrace_handler);
>  
> diff --git a/arch/x86/kernel/kprobes/ftrace.c b/arch/x86/kernel/kprobes/ftrace.c
> index 681a4b36e9bb..a40a6cdfcca3 100644
> --- a/arch/x86/kernel/kprobes/ftrace.c
> +++ b/arch/x86/kernel/kprobes/ftrace.c
> @@ -18,11 +18,16 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
>  {
>  	struct kprobe *p;
>  	struct kprobe_ctlblk *kcb;
> +	int bit;
>  
> -	/* Preempt is disabled by ftrace */
> +	bit = ftrace_test_recursion_trylock();
> +	if (bit < 0)
> +		return;
> +
> +	preempt_disable_notrace();
>  	p = get_kprobe((kprobe_opcode_t *)ip);
>  	if (unlikely(!p) || kprobe_disabled(p))
> -		return;
> +		goto out;
>  
>  	kcb = get_kprobe_ctlblk();
>  	if (kprobe_running()) {
> @@ -52,6 +57,9 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
>  		 */
>  		__this_cpu_write(current_kprobe, NULL);
>  	}
> +out:
> +	preempt_enable_notrace();
> +	ftrace_test_recursion_unlock(bit);
>  }
>  NOKPROBE_SYMBOL(kprobe_ftrace_handler);
>  
> -- 
> 2.28.0
> 
> 


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

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