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Commit 5bb4fc2d authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Ingo Molnar
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kprobes/x86: Disable preemption in ftrace-based jprobes 



Disable preemption in ftrace-based jprobe handlers as
described in Documentation/kprobes.txt:

  "Probe handlers are run with preemption disabled."

This will fix jprobes behavior when CONFIG_PREEMPT=y.

Signed-off-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
Cc: Alexei Starovoitov <ast@fb.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E . McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/150581530024.32348.9863783558598926771.stgit@devbox


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 9a09f261

arch/x86/kernel/kprobes/ftrace.c

+14 −9
Original line number Diff line number Diff line
@@ -26,7 +26,7 @@ 
#include "common.h"



static nokprobe_inline

int __skip_singlestep(struct kprobe *p, struct pt_regs *regs,

void __skip_singlestep(struct kprobe *p, struct pt_regs *regs,

		      struct kprobe_ctlblk *kcb, unsigned long orig_ip)

{

	/*
@@ -41,20 +41,21 @@ int __skip_singlestep(struct kprobe *p, struct pt_regs *regs, 
	__this_cpu_write(current_kprobe, NULL);

	if (orig_ip)

		regs->ip = orig_ip;

	return 1;

}



int skip_singlestep(struct kprobe *p, struct pt_regs *regs,

		    struct kprobe_ctlblk *kcb)

{

	if (kprobe_ftrace(p))

		return __skip_singlestep(p, regs, kcb, 0);

	else

	if (kprobe_ftrace(p)) {

		__skip_singlestep(p, regs, kcb, 0);

		preempt_enable_no_resched();

		return 1;

	}

	return 0;

}

NOKPROBE_SYMBOL(skip_singlestep);



/* Ftrace callback handler for kprobes */

/* Ftrace callback handler for kprobes -- called under preepmt disabed */

void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,

			   struct ftrace_ops *ops, struct pt_regs *regs)

{
@@ -77,13 +78,17 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, 
		/* Kprobe handler expects regs->ip = ip + 1 as breakpoint hit */

		regs->ip = ip + sizeof(kprobe_opcode_t);



		/* To emulate trap based kprobes, preempt_disable here */

		preempt_disable();

		__this_cpu_write(current_kprobe, p);

		kcb->kprobe_status = KPROBE_HIT_ACTIVE;

		if (!p->pre_handler || !p->pre_handler(p, regs))

		if (!p->pre_handler || !p->pre_handler(p, regs)) {

			__skip_singlestep(p, regs, kcb, orig_ip);

			preempt_enable_no_resched();

		}

		/*

		 * If pre_handler returns !0, it sets regs->ip and

		 * resets current kprobe.

		 * resets current kprobe, and keep preempt count +1.

		 */

	}

end: