linux-kernel - Re: [PATCH 1/3] powerpc: kprobes: add support for KPROBES_ON

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Message-Id: <20170215161126.104c1db721182e1e75244125@kernel.org>
Date:   Wed, 15 Feb 2017 16:11:26 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
Cc:     Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 1/3] powerpc: kprobes: add support for KPROBES_ON_FTRACE

Hi Naveen,

On Wed, 15 Feb 2017 00:28:34 +0530
"Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com> wrote:

> diff --git a/arch/powerpc/kernel/optprobes.c b/arch/powerpc/kernel/optprobes.c
> index e51a045f3d3b..a8f414a0b141 100644
> --- a/arch/powerpc/kernel/optprobes.c
> +++ b/arch/powerpc/kernel/optprobes.c
> @@ -70,6 +70,9 @@ static unsigned long can_optimize(struct kprobe *p)
>  	struct instruction_op op;
>  	unsigned long nip = 0;
>  
> +	if (unlikely(kprobe_ftrace(p)))
> +		return 0;
> +

Hmm, this should not be checked in arch-depend code, since it may duplicate
code in each arch. Please try below.

Thanks,

commit 897bb304974c1b0c19a4274fea220b175b07f353
Author: Masami Hiramatsu <mhiramat@...nel.org>
Date:   Wed Feb 15 15:48:14 2017 +0900

    kprobes: Skip preparing optprobe if the probe is ftrace-based
    
    Skip preparing optprobe if the probe is ftrace-based, since
    anyway, it must not be optimized (or already optimized by
    ftrace).
    
    Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index ebb4dad..546a8b1 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -746,13 +746,20 @@ static void kill_optimized_kprobe(struct kprobe *p)
 	arch_remove_optimized_kprobe(op);
 }
 
+static inline
+void __prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
+{
+	if (!kprobe_ftrace(p))
+		arch_prepare_optimized_kprobe(op, p);
+}
+
 /* Try to prepare optimized instructions */
 static void prepare_optimized_kprobe(struct kprobe *p)
 {
 	struct optimized_kprobe *op;
 
 	op = container_of(p, struct optimized_kprobe, kp);
-	arch_prepare_optimized_kprobe(op, p);
+	__prepare_optimized_kprobe(op, p);
 }
 
 /* Allocate new optimized_kprobe and try to prepare optimized instructions */
@@ -766,7 +773,7 @@ static struct kprobe *alloc_aggr_kprobe(struct kprobe *p)
 
 	INIT_LIST_HEAD(&op->list);
 	op->kp.addr = p->addr;
-	arch_prepare_optimized_kprobe(op, p);
+	__prepare_optimized_kprobe(op, p);
 
 	return &op->kp;
 }



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