linux-kernel - [RFC PATCH v3 13/26] early kprobes: ARM: directly modify code.

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Date:	Fri, 13 Feb 2015 13:40:48 +0800
From:	Wang Nan <wangnan0@...wei.com>
To:	<linux@....linux.org.uk>, <tglx@...utronix.de>, <mingo@...hat.com>,
	<hpa@...or.com>, <rostedt@...dmis.org>, <ananth@...ibm.com>,
	<anil.s.keshavamurthy@...el.com>, <davem@...emloft.net>,
	<masami.hiramatsu.pt@...achi.com>, <luto@...capital.net>,
	<keescook@...omium.org>, <oleg@...hat.com>, <wangnan0@...wei.com>,
	<dave.long@...aro.org>, <tixy@...aro.org>, <nico@...aro.org>,
	<yalin.wang2010@...il.com>, <catalin.marinas@....com>,
	<Yalin.Wang@...ymobile.com>, <mark.rutland@....com>,
	<dave.hansen@...ux.intel.com>, <jkenisto@...ibm.com>,
	<anton@...ba.org>, <stefani@...bold.net>, <JBeulich@...e.com>,
	<akpm@...ux-foundation.org>, <rusty@...tcorp.com.au>,
	<peterz@...radead.org>, <prarit@...hat.com>, <fabf@...net.be>,
	<hannes@...xchg.org>
CC:	<x86@...nel.org>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <lizefan@...wei.com>
Subject: [RFC PATCH v3 13/26] early kprobes: ARM: directly modify code.

For early kprobe, we can simply patch text because we are in a relative
simple environment.

Signed-off-by: Wang Nan <wangnan0@...wei.com>
---
 arch/arm/probes/kprobes/opt-arm.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/arch/arm/probes/kprobes/opt-arm.c b/arch/arm/probes/kprobes/opt-arm.c
index bcdecc2..43446df 100644
--- a/arch/arm/probes/kprobes/opt-arm.c
+++ b/arch/arm/probes/kprobes/opt-arm.c
@@ -330,8 +330,18 @@ 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_is_early())) {
+			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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