linux-kernel - [PATCH -tip tracing/kprobes 2/6] kprobes/x86-64: Allow to reenter probe on post

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Date:	Thu, 27 Aug 2009 13:23:04 -0400
From:	Masami Hiramatsu <mhiramat@...hat.com>
To:	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	lkml <linux-kernel@...r.kernel.org>
Cc:	systemtap <systemtap@...rces.redhat.com>,
	DLE <dle-develop@...ts.sourceforge.net>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Ingo Molnar <mingo@...e.hu>
Subject: [PATCH -tip tracing/kprobes 2/6] kprobes/x86-64: Allow to reenter
	probe on post_handler

Allow to reenter probe on the post_handler of another probe on x86-64,
because x86-64 already allows reentering int3.
In that case, reentered probe just increases kp.nmissed and returns.

Signed-off-by: Masami Hiramatsu <mhiramat@...hat.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Ananth N Mavinakayanahalli <ananth@...ibm.com>
Cc: Ingo Molnar <mingo@...e.hu>
---

 arch/x86/kernel/kprobes.c |   11 -----------
 1 files changed, 0 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c
index e0fb615..c5f1f11 100644
--- a/arch/x86/kernel/kprobes.c
+++ b/arch/x86/kernel/kprobes.c
@@ -463,17 +463,6 @@ static int __kprobes reenter_kprobe(struct kprobe *p, struct pt_regs *regs,
 {
 	switch (kcb->kprobe_status) {
 	case KPROBE_HIT_SSDONE:
-#ifdef CONFIG_X86_64
-		/* TODO: Provide re-entrancy from post_kprobes_handler() and
-		 * avoid exception stack corruption while single-stepping on
-		 * the instruction of the new probe.
-		 */
-		arch_disarm_kprobe(p);
-		regs->ip = (unsigned long)p->addr;
-		reset_current_kprobe();
-		preempt_enable_no_resched();
-		break;
-#endif
 	case KPROBE_HIT_ACTIVE:
 		save_previous_kprobe(kcb);
 		set_current_kprobe(p, regs, kcb);


-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@...hat.com
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