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Date: Fri, 19 May 2006 16:13:02 -0400
From: Satoshi Oshima <soshima@redhat.com>
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To: Andrew Morton <akpm@osdl.org>
CC: linux-kernel@vger.kernel.org, systemtap@sources.redhat.com,
       Ananth N Mavinakayanahalli <mananth@in.ibm.com>,
       Jim Keniston <jkenisto@us.ibm.com>,
       Prasanna S Panchamukhi <prasanna@in.ibm.com>,
       "Keshavamurthy, Anil S" <anil.s.keshavamurthy@intel.com>,
       "Hideo AOKI@redhat" <haoki@redhat.com>,
       sugita <sugita@sdl.hitachi.co.jp>,
       Masami Hiramatsu <hiramatu@sdl.hitachi.co.jp>
Subject: [Patch] Kprobes: bugfix of kprobe-booster: reenable kprobe-booster
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Hi Andrew,

I found a bug of kprobes in i386.

Kprobe-booster doesn't work if CONFIG_PREEMPT is not set.
Because pre_preempt_count is always 0.

Boostability have been disabled when removing '#ifdef 
CONFIG_PREEMPT' I think.

This bug doesn't cause a kernel panic.

Regards,

Satoshi Oshima

Signed-off-by: Satoshi Oshima <soshima@redhat.com>

diff -Narup linux-2.6.17-rc3-mm1.orig/arch/i386/kernel/kprobes.c kprobes-i386-bugfix/arch/i386/kernel/kprobes.c
--- linux-2.6.17-rc3-mm1.orig/arch/i386/kernel/kprobes.c	2006-05-04 12:34:46.000000000 -0400
+++ kprobes-i386-bugfix/arch/i386/kernel/kprobes.c	2006-05-12 15:41:23.000000000 -0400
@@ -257,7 +257,11 @@ static int __kprobes kprobe_handler(stru
 	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));