linux-kernel - [RFC PATCH 01/11] ARM: kprobes: directly modify code if kprobe is not initialized.

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Date:	Wed, 7 Jan 2015 15:35:24 +0800
From:	Wang Nan <wangnan0@...wei.com>
To:	<linux@....linux.org.uk>, <mingo@...hat.com>, <x86@...nel.org>,
	<masami.hiramatsu.pt@...achi.com>,
	<anil.s.keshavamurthy@...el.com>, <davem@...emloft.net>,
	<ananth@...ibm.com>, <dave.long@...aro.org>, <tixy@...aro.org>
CC:	<lizefan@...wei.com>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>
Subject: [RFC PATCH 01/11] ARM: kprobes: directly modify code if kprobe is not initialized.

If kprobe is optimized before kprobe is initialized, there should
be only one core, the probed instruction is not armed with breakpoint,
so simply patch text is okay.

Signed-off-by: Wang Nan <wangnan0@...wei.com>
---
 arch/arm/probes/kprobes/opt-arm.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/arm/probes/kprobes/opt-arm.c b/arch/arm/probes/kprobes/opt-arm.c
index 15b37c0..a021474 100644
--- a/arch/arm/probes/kprobes/opt-arm.c
+++ b/arch/arm/probes/kprobes/opt-arm.c
@@ -325,8 +325,17 @@ void __kprobes arch_optimize_kprobes(struct list_head *oplist)
 		 * Similar to __arch_disarm_kprobe, operations which
 		 * removing breakpoints must be wrapped by stop_machine
 		 * to avoid racing.
+		 *
+		 * If this function is called before kprobes initialized,
+		 * the kprobe should be an early kprobe, the instruction
+		 * is not armed with breakpoint. There should be only
+		 * one core now, so directly __patch_text is enough.
 		 */
-		kprobes_remove_breakpoint(op->kp.addr, insn);
+		if (unlikely(!kprobes_initialized)) {
+			BUG_ON(!(op->kp.flags & KPROBE_FLAG_EARLY));
+			__patch_text(op->kp.addr, insn);
+		} else
+			kprobes_remove_breakpoint(op->kp.addr, insn);
 
 		list_del_init(&op->list);
 	}
-- 
1.8.4

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