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Commit a19b2e3d authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Ingo Molnar
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kprobes/x86: Remove IRQ disabling from ftrace-based/optimized kprobes 



Kkprobes don't need to disable IRQs if they are called from the
ftrace/jump trampoline code, because Documentation/kprobes.txt says:

  -----
  Probe handlers are run with preemption disabled.  Depending on the
  architecture and optimization state, handlers may also run with
  interrupts disabled (e.g., kretprobe handlers and optimized kprobe
  handlers run without interrupt disabled on x86/x86-64).
  -----

So let's remove IRQ disabling from those handlers.

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/150581534039.32348.11331736206004264553.stgit@devbox


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 5bb4fc2d

arch/x86/kernel/kprobes/ftrace.c

+2 −7
Original line number Original line Diff line number Diff line
@@ -61,14 +61,11 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, 
{

{

	struct kprobe *p;

	struct kprobe *p;

	struct kprobe_ctlblk *kcb;

	struct kprobe_ctlblk *kcb;

	unsigned long flags;



	/* Disable irq for emulating a breakpoint and avoiding preempt */

	local_irq_save(flags);





	/* Preempt is disabled by ftrace */

	p = get_kprobe((kprobe_opcode_t *)ip);

	p = get_kprobe((kprobe_opcode_t *)ip);

	if (unlikely(!p) || kprobe_disabled(p))

	if (unlikely(!p) || kprobe_disabled(p))

		goto end;

		return;





	kcb = get_kprobe_ctlblk();

	kcb = get_kprobe_ctlblk();

	if (kprobe_running()) {

	if (kprobe_running()) {
@@ -91,8 +88,6 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, 
		 * resets current kprobe, and keep preempt count +1.

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

		 */

		 */

	}

	}

end:

	local_irq_restore(flags);

}

}

NOKPROBE_SYMBOL(kprobe_ftrace_handler);

NOKPROBE_SYMBOL(kprobe_ftrace_handler);

arch/x86/kernel/kprobes/opt.c

+0 −4
Original line number Original line Diff line number Diff line
@@ -154,13 +154,10 @@ STACK_FRAME_NON_STANDARD(optprobe_template_func); 
static void

static void

optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs)

optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs)

{

{

	unsigned long flags;



	/* This is possible if op is under delayed unoptimizing */

	/* This is possible if op is under delayed unoptimizing */

	if (kprobe_disabled(&op->kp))

	if (kprobe_disabled(&op->kp))

		return;

		return;





	local_irq_save(flags);

	preempt_disable();

	preempt_disable();

	if (kprobe_running()) {

	if (kprobe_running()) {

		kprobes_inc_nmissed_count(&op->kp);

		kprobes_inc_nmissed_count(&op->kp);
@@ -182,7 +179,6 @@ optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs) 
		__this_cpu_write(current_kprobe, NULL);

		__this_cpu_write(current_kprobe, NULL);

	}

	}

	preempt_enable_no_resched();

	preempt_enable_no_resched();

	local_irq_restore(flags);

}

}

NOKPROBE_SYMBOL(optimized_callback);

NOKPROBE_SYMBOL(optimized_callback);