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Commit c39df470 authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Linus Torvalds
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[PATCH] kprobe-booster: disable in preemptible kernel 



The kprobe-booster's safety check against preemption does not work well
now, because the preemption count has been modified by read_rcu_lock() in
atomic_notifier_call_chain() before we check it.  So, I'd like to prevent
boosting kprobe temporarily if the kernel is preemptable.

Now we are searching for the good solution.

Signed-off-by: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 2a8a3d5b

arch/i386/kernel/kprobes.c

+3 −6
Original line number Diff line number Diff line
@@ -256,11 +256,6 @@ static int __kprobes kprobe_handler(struct pt_regs *regs) 
	int ret = 0;

	kprobe_opcode_t *addr;

	struct kprobe_ctlblk *kcb;

#ifdef CONFIG_PREEMPT

	unsigned pre_preempt_count = preempt_count();

#else

	unsigned pre_preempt_count = 1;

#endif



	addr = (kprobe_opcode_t *)(regs->eip - sizeof(kprobe_opcode_t));
@@ -338,13 +333,15 @@ static int __kprobes kprobe_handler(struct pt_regs *regs) 
		return 1;



ss_probe:

	if (pre_preempt_count && p->ainsn.boostable == 1 && !p->post_handler){

#ifndef CONFIG_PREEMPT

	if (p->ainsn.boostable == 1 && !p->post_handler){

		/* Boost up -- we can execute copied instructions directly */

		reset_current_kprobe();

		regs->eip = (unsigned long)p->ainsn.insn;

		preempt_enable_no_resched();

		return 1;

	}

#endif

	prepare_singlestep(p, regs);

	kcb->kprobe_status = KPROBE_HIT_SS;

	return 1;