ARM: kprobes: collects stack consumption for store instructions

This patch uses the previously introduced checker functionality on
store instructions to record their stack consumption information to
arch_probes_insn.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Reviewed-by: Jon Medhurst <tixy@linaro.org>
Signed-off-by: Jon Medhurst <tixy@linaro.org>

arch/arm/probes/kprobes/checkers-thumb.c

@@ -0,0 +1,110 @@
+/*
+ * arch/arm/probes/kprobes/checkers-thumb.c
+ *
+ * Copyright (C) 2014 Huawei Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+#include <linux/kernel.h>
+#include "../decode.h"
+#include "../decode-thumb.h"
+#include "checkers.h"
+
+static enum probes_insn __kprobes t32_check_stack(probes_opcode_t insn,
+		struct arch_probes_insn *asi,
+		const struct decode_header *h)
+{
+	/*
+	 * PROBES_T32_LDMSTM, PROBES_T32_LDRDSTRD and PROBES_T32_LDRSTR
+	 * may get here. Simply mark all normal insns as STACK_USE_NONE.
+	 */
+	static const union decode_item table[] = {
+
+		/*
+		 * First, filter out all ldr insns to make our life easier.
+		 * Following load insns may come here:
+		 * LDM, LDRD, LDR.
+		 * In T32 encoding, bit 20 is enough for distinguishing
+		 * load and store. All load insns have this bit set, when
+		 * all store insns have this bit clear.
+		 */
+		DECODE_CUSTOM	(0x00100000, 0x00100000, STACK_USE_NONE),
+
+		/*
+		 * Mark all 'STR{,B,H}, Rt, [Rn, Rm]' as STACK_USE_UNKNOWN
+		 * if Rn or Rm is SP. T32 doesn't encode STRD.
+		 */
+		/*                                 xx | Rn | Rt |         | Rm |*/
+		/* STR (register)	1111 1000 0100 xxxx xxxx 0000 00xx xxxx */
+		/* STRB (register)	1111 1000 0000 xxxx xxxx 0000 00xx xxxx */
+		/* STRH (register)	1111 1000 0010 xxxx xxxx 0000 00xx xxxx */
+		/* INVALID INSN		1111 1000 0110 xxxx xxxx 0000 00xx xxxx */
+		/* By Introducing INVALID INSN, bit 21 and 22 can be ignored. */
+		DECODE_OR	(0xff9f0fc0, 0xf80d0000),
+		DECODE_CUSTOM	(0xff900fcf, 0xf800000d, STACK_USE_UNKNOWN),
+
+
+		/*                                 xx | Rn | Rt | PUW|   imm8  |*/
+		/* STR (imm 8)		1111 1000 0100 1101 xxxx 110x xxxx xxxx */
+		/* STRB (imm 8)		1111 1000 0000 1101 xxxx 110x xxxx xxxx */
+		/* STRH (imm 8)		1111 1000 0010 1101 xxxx 110x xxxx xxxx */
+		/* INVALID INSN		1111 1000 0110 1101 xxxx 110x xxxx xxxx */
+		/* Only consider U == 0 and P == 1: strx rx, [sp, #-<imm>] */
+		DECODE_CUSTOM	(0xff9f0e00, 0xf80d0c00, STACK_USE_FIXED_0XX),
+
+		/* For STR{,B,H} (imm 12), offset is always positive, so ignore them. */
+
+		/*                              P U W | Rn | Rt | Rt2|   imm8  |*/
+		/* STRD (immediate)	1110 1001 01x0 1101 xxxx xxxx xxxx xxxx */
+		/*
+		 * Only consider U == 0 and P == 1.
+		 * Also note that STRD in T32 encoding is special:
+		 * imm = ZeroExtend(imm8:'00', 32)
+		 */
+		DECODE_CUSTOM	(0xffdf0000, 0xe94d0000, STACK_USE_T32STRD),
+
+		/*                                    | Rn | */
+		/* STMDB		1110 1001 00x0 1101 xxxx xxxx xxxx xxxx */
+		DECODE_CUSTOM	(0xffdf0000, 0xe90d0000, STACK_USE_STMDX),
+
+		/* fall through */
+		DECODE_CUSTOM	(0, 0, STACK_USE_NONE),
+		DECODE_END
+	};
+
+	return probes_decode_insn(insn, asi, table, false, false, stack_check_actions, NULL);
+}
+
+const struct decode_checker t32_stack_checker[NUM_PROBES_T32_ACTIONS] = {
+	[PROBES_T32_LDMSTM] = {.checker = t32_check_stack},
+	[PROBES_T32_LDRDSTRD] = {.checker = t32_check_stack},
+	[PROBES_T32_LDRSTR] = {.checker = t32_check_stack},
+};
+
+/*
+ * See following comments. This insn must be 'push'.
+ */
+static enum probes_insn __kprobes t16_check_stack(probes_opcode_t insn,
+		struct arch_probes_insn *asi,
+		const struct decode_header *h)
+{
+	unsigned int reglist = insn & 0x1ff;
+	asi->stack_space = hweight32(reglist) * 4;
+	return INSN_GOOD;
+}
+
+/*
+ * T16 encoding is simple: only the 'push' insn can need extra stack space.
+ * Other insns, like str, can only use r0-r7 as Rn.
+ */
+const struct decode_checker t16_stack_checker[NUM_PROBES_T16_ACTIONS] = {
+	[PROBES_T16_PUSH] = {.checker = t16_check_stack},
+};