linux-kernel - [PATCH] ARM: probes: return directly when emulate not set

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Message-ID: <1409116109-67330-1-git-send-email-wangnan0@huawei.com>
Date:	Wed, 27 Aug 2014 13:08:29 +0800
From:	Wang Nan <wangnan0@...wei.com>
To:	"David A. Long" <dave.long@...aro.org>,
	Russell King <linux@....linux.org.uk>,
	Jon Medhurst <tixy@...aro.org>,
	Taras Kondratiuk <taras.kondratiuk@...aro.org>,
	Ben Dooks <ben.dooks@...ethink.co.uk>
CC:	Wang Nan <wangnan0@...wei.com>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <peifeiyue@...wei.com>
Subject: [PATCH] ARM: probes: return directly when emulate not set

When kprobe decoding instruction, original code calls instruction
specific decoder if emulate is set to false.  However, instructions with
DECODE_TYPE_EMULATE are in fact don't have their decoder. What in the
action table are in fact handlers.  For example:

	/* LDRD (immediate)	cccc 000x x1x0 xxxx xxxx xxxx 1101 xxxx */
	/* STRD (immediate)	cccc 000x x1x0 xxxx xxxx xxxx 1111 xxxx */
	DECODE_EMULATEX	(0x0e5000d0, 0x004000d0, PROBES_LDRSTRD,
						 REGS(NOPCWB, NOPCX, 0, 0, 0)),

	and

const union decode_action kprobes_arm_actions[NUM_PROBES_ARM_ACTIONS] = {
	...
	[PROBES_LDRSTRD] = {.handler = emulate_ldrdstrd},
	...

In this situation, original code calls 'emulate_ldrdstrd' as a decoder,
which is obviously incorrect.

This patch makes it returns INSN_GOOD directly when 'emulate' is not
true.

Signed-off-by: Wang Nan <wangnan0@...wei.com>
Cc: "David A. Long" <dave.long@...aro.org>
Cc: Russell King <linux@....linux.org.uk>
Cc: Jon Medhurst <tixy@...aro.org>
Cc: Taras Kondratiuk <taras.kondratiuk@...aro.org>
Cc: Ben Dooks <ben.dooks@...ethink.co.uk>
---
 arch/arm/kernel/probes.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/arm/kernel/probes.c b/arch/arm/kernel/probes.c
index a8ab540..1c77b8d 100644
--- a/arch/arm/kernel/probes.c
+++ b/arch/arm/kernel/probes.c
@@ -436,8 +436,7 @@ probes_decode_insn(probes_opcode_t insn, struct arch_probes_insn *asi,
 			struct decode_emulate *d = (struct decode_emulate *)h;
 
 			if (!emulate)
-				return actions[d->handler.action].decoder(insn,
-					asi, h);
+				return INSN_GOOD;
 
 			asi->insn_handler = actions[d->handler.action].handler;
 			set_emulated_insn(insn, asi, thumb);
-- 
1.8.4

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