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Commit 1ffabfc1 authored by Naveen N. Rao's avatar Naveen N. Rao Committed by Greg Kroah-Hartman
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powerpc/kprobes: Disable preemption before invoking probe handler for optprobes 



commit 8a2d71a3 upstream.

Per Documentation/kprobes.txt, probe handlers need to be invoked with
preemption disabled. Update optimized_callback() to do so. Also move
get_kprobe_ctlblk() invocation post preemption disable, since it
accesses pre-cpu data.

This was not an issue so far since optprobes wasn't selected if
CONFIG_PREEMPT was enabled. Commit a30b85df ("kprobes: Use
synchronize_rcu_tasks() for optprobe with CONFIG_PREEMPT=y") changes
this.

Signed-off-by: default avatarNaveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Acked-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent f8d07852

arch/powerpc/kernel/optprobes.c

+3 −2
Original line number Diff line number Diff line
@@ -115,7 +115,6 @@ static unsigned long can_optimize(struct kprobe *p) 
static void optimized_callback(struct optimized_kprobe *op,

			       struct pt_regs *regs)

{

	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();

	unsigned long flags;



	/* This is possible if op is under delayed unoptimizing */
@@ -124,13 +123,14 @@ static void optimized_callback(struct optimized_kprobe *op, 


	local_irq_save(flags);

	hard_irq_disable();

	preempt_disable();



	if (kprobe_running()) {

		kprobes_inc_nmissed_count(&op->kp);

	} else {

		__this_cpu_write(current_kprobe, &op->kp);

		regs->nip = (unsigned long)op->kp.addr;

		kcb->kprobe_status = KPROBE_HIT_ACTIVE;

		get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;

		opt_pre_handler(&op->kp, regs);

		__this_cpu_write(current_kprobe, NULL);

	}
@@ -140,6 +140,7 @@ static void optimized_callback(struct optimized_kprobe *op, 
	 * local_irq_restore() will re-enable interrupts,

	 * if they were hard disabled.

	 */

	preempt_enable_no_resched();

	local_irq_restore(flags);

}

NOKPROBE_SYMBOL(optimized_callback);