[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: Masami 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: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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@ -256,11 +256,6 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
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int ret = 0;
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kprobe_opcode_t *addr;
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struct kprobe_ctlblk *kcb;
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#ifdef CONFIG_PREEMPT
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unsigned pre_preempt_count = preempt_count();
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#else
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unsigned pre_preempt_count = 1;
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#endif
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addr = (kprobe_opcode_t *)(regs->eip - sizeof(kprobe_opcode_t));
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@ -338,13 +333,15 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
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return 1;
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ss_probe:
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if (pre_preempt_count && p->ainsn.boostable == 1 && !p->post_handler){
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#ifndef CONFIG_PREEMPT
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if (p->ainsn.boostable == 1 && !p->post_handler){
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/* Boost up -- we can execute copied instructions directly */
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reset_current_kprobe();
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regs->eip = (unsigned long)p->ainsn.insn;
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preempt_enable_no_resched();
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return 1;
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}
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#endif
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prepare_singlestep(p, regs);
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kcb->kprobe_status = KPROBE_HIT_SS;
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return 1;
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