linux-kernel - [PATCH] kprobes,x86: disable irq durinr optimized callback

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Date:	Tue, 26 Apr 2011 15:01:31 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	masami.hiramatsu.pt@...achi.com
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu,
	Jiri Olsa <jolsa@...hat.com>
Subject: [PATCH] kprobes,x86: disable irq durinr optimized callback

hi,

attached patch is disabling irqs during optimized callback,
so we dont miss any in-irq kprobes as missed.

Also I think there's small window where current_kprobe variable
could be touched in non-safe way, but I was not able to hit
any issue.

I'm not sure wether this is a bug or if it was intentional to have
irqs enabled during the pre_handler callback.

wbr,
jirka

---
Disabling irqs during optimized callback, so we dont miss
any in-irq kprobes as missed.

Interrupts are also disabled during non-optimized kprobes callbacks.

Signed-off-by: Jiri Olsa <jolsa@...hat.com>
---
 arch/x86/kernel/kprobes.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c
index c969fd9..917cb31 100644
--- a/arch/x86/kernel/kprobes.c
+++ b/arch/x86/kernel/kprobes.c
@@ -1183,11 +1183,13 @@ static void __kprobes 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 */
 	if (kprobe_disabled(&op->kp))
 		return;
 
+	local_irq_save(flags);
 	preempt_disable();
 	if (kprobe_running()) {
 		kprobes_inc_nmissed_count(&op->kp);
@@ -1208,6 +1210,7 @@ static void __kprobes optimized_callback(struct optimized_kprobe *op,
 		__this_cpu_write(current_kprobe, NULL);
 	}
 	preempt_enable_no_resched();
+	local_irq_restore(flags);
 }
 
 static int __kprobes copy_optimized_instructions(u8 *dest, u8 *src)
-- 
1.7.1

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