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/include/asm/probes.h

@@ -38,6 +38,7 @@ struct arch_probes_insn {
 	probes_check_cc			*insn_check_cc;
 	probes_insn_singlestep_t	*insn_singlestep;
 	probes_insn_fn_t		*insn_fn;
+	int				stack_space;
 };
 
 #endif

arch/arm/probes/decode.c

@@ -425,6 +425,16 @@ probes_decode_insn(probes_opcode_t insn, struct arch_probes_insn *asi,
 	 */
 	probes_opcode_t origin_insn = insn;
 
+	/*
+	 * stack_space is initialized to 0 here. Checker functions
+	 * should update is value if they find this is a stack store
+	 * instruction: positive value means bytes of stack usage,
+	 * negitive value means unable to determine stack usage
+	 * statically. For instruction doesn't store to stack, checker
+	 * do nothing with it.
+	 */
+	asi->stack_space = 0;
+
 	if (emulate)
 		insn = prepare_emulated_insn(insn, asi, thumb);
 

arch/arm/probes/kprobes/Makefile

@@ -1,11 +1,11 @@
-obj-$(CONFIG_KPROBES)		+= core.o actions-common.o
+obj-$(CONFIG_KPROBES)		+= core.o actions-common.o checkers-common.o
 obj-$(CONFIG_ARM_KPROBES_TEST)	+= test-kprobes.o
 test-kprobes-objs		:= test-core.o
 
 ifdef CONFIG_THUMB2_KERNEL
-obj-$(CONFIG_KPROBES)		+= actions-thumb.o
+obj-$(CONFIG_KPROBES)		+= actions-thumb.o checkers-thumb.o
 test-kprobes-objs		+= test-thumb.o
 else
-obj-$(CONFIG_KPROBES)		+= actions-arm.o
+obj-$(CONFIG_KPROBES)		+= actions-arm.o checkers-arm.o
 test-kprobes-objs		+= test-arm.o
 endif

arch/arm/probes/kprobes/actions-arm.c

@@ -64,6 +64,7 @@
 
 #include "../decode-arm.h"
 #include "core.h"
+#include "checkers.h"
 
 #if  __LINUX_ARM_ARCH__ >= 6
 #define BLX(reg)	"blx	"reg"		\n\t"
@@ -340,4 +341,4 @@ const union decode_action kprobes_arm_actions[NUM_PROBES_ARM_ACTIONS] = {
 	[PROBES_LDMSTM] = {.decoder = kprobe_decode_ldmstm}
 };
 
-const struct decode_checker *kprobes_arm_checkers[] = {NULL};
+const struct decode_checker *kprobes_arm_checkers[] = {arm_stack_checker, NULL};

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

@@ -15,6 +15,7 @@
 
 #include "../decode-thumb.h"
 #include "core.h"
+#include "checkers.h"
 
 /* These emulation encodings are functionally equivalent... */
 #define t32_emulate_rd8rn16rm0ra12_noflags \
@@ -665,5 +666,5 @@ const union decode_action kprobes_t32_actions[NUM_PROBES_T32_ACTIONS] = {
 		.handler = t32_emulate_rdlo12rdhi8rn16rm0_noflags},
 };
 
-const struct decode_checker *kprobes_t32_checkers[] = {NULL};
-const struct decode_checker *kprobes_t16_checkers[] = {NULL};
+const struct decode_checker *kprobes_t32_checkers[] = {t32_stack_checker, NULL};
+const struct decode_checker *kprobes_t16_checkers[] = {t16_stack_checker, NULL};

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

@@ -0,0 +1,99 @@
+/*
+ * arch/arm/probes/kprobes/checkers-arm.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-arm.h"
+#include "checkers.h"
+
+static enum probes_insn __kprobes arm_check_stack(probes_opcode_t insn,
+		struct arch_probes_insn *asi,
+		const struct decode_header *h)
+{
+	/*
+	 * PROBES_LDRSTRD, PROBES_LDMSTM, PROBES_STORE,
+	 * PROBES_STORE_EXTRA may get here. Simply mark all normal
+	 * insns as STACK_USE_NONE.
+	 */
+	static const union decode_item table[] = {
+		/*
+		 * 'STR{,D,B,H}, Rt, [Rn, Rm]' should be marked as UNKNOWN
+		 * if Rn or Rm is SP.
+		 *                                 x
+		 * STR (register)	cccc 011x x0x0 xxxx xxxx xxxx xxxx xxxx
+		 * STRB (register)	cccc 011x x1x0 xxxx xxxx xxxx xxxx xxxx
+		 */
+		DECODE_OR	(0x0e10000f, 0x0600000d),
+		DECODE_OR	(0x0e1f0000, 0x060d0000),
+
+		/*
+		 *                                                     x
+		 * STRD (register)	cccc 000x x0x0 xxxx xxxx xxxx 1111 xxxx
+		 * STRH (register)	cccc 000x x0x0 xxxx xxxx xxxx 1011 xxxx
+		 */
+		DECODE_OR	(0x0e5000bf, 0x000000bd),
+		DECODE_CUSTOM	(0x0e5f00b0, 0x000d00b0, STACK_USE_UNKNOWN),
+
+		/*
+		 * For PROBES_LDMSTM, only stmdx sp, [...] need to examine
+		 *
+		 * Bit B/A (bit 24) encodes arithmetic operation order. 1 means
+		 * before, 0 means after.
+		 * Bit I/D (bit 23) encodes arithmetic operation. 1 means
+		 * increment, 0 means decrement.
+		 *
+		 * So:
+		 *                              B I
+		 *                              / /
+		 *                              A D   | Rn |
+		 * STMDX SP, [...]	cccc 100x 00x0 xxxx xxxx xxxx xxxx xxxx
+		 */
+		DECODE_CUSTOM	(0x0edf0000, 0x080d0000, STACK_USE_STMDX),
+
+		/*                              P U W | Rn | Rt |     imm12    |*/
+		/* STR (immediate)	cccc 010x x0x0 1101 xxxx xxxx xxxx xxxx */
+		/* STRB (immediate)	cccc 010x x1x0 1101 xxxx xxxx xxxx xxxx */
+		/*                              P U W | Rn | Rt |imm4|    |imm4|*/
+		/* STRD (immediate)	cccc 000x x1x0 1101 xxxx xxxx 1111 xxxx */
+		/* STRH (immediate)	cccc 000x x1x0 1101 xxxx xxxx 1011 xxxx */
+		/*
+		 * index = (P == '1'); add = (U == '1').
+		 * Above insns with:
+		 *    index == 0 (str{,d,h} rx, [sp], #+/-imm) or
+		 *    add == 1 (str{,d,h} rx, [sp, #+<imm>])
+		 * should be STACK_USE_NONE.
+		 * Only str{,b,d,h} rx,[sp,#-n] (P == 1 and U == 0) are
+		 * required to be examined.
+		 */
+		/* STR{,B} Rt,[SP,#-n]	cccc 0101 0xx0 1101 xxxx xxxx xxxx xxxx */
+		DECODE_CUSTOM	(0x0f9f0000, 0x050d0000, STACK_USE_FIXED_XXX),
+
+		/* STR{D,H} Rt,[SP,#-n]	cccc 0001 01x0 1101 xxxx xxxx 1x11 xxxx */
+		DECODE_CUSTOM	(0x0fdf00b0, 0x014d00b0, STACK_USE_FIXED_X0X),
+
+		/* 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 arm_stack_checker[NUM_PROBES_ARM_ACTIONS] = {
+	[PROBES_LDRSTRD] = {.checker = arm_check_stack},
+	[PROBES_STORE_EXTRA] = {.checker = arm_check_stack},
+	[PROBES_STORE] = {.checker = arm_check_stack},
+	[PROBES_LDMSTM] = {.checker = arm_check_stack},
+};

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

@@ -0,0 +1,101 @@
+/*
+ * arch/arm/probes/kprobes/checkers-common.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-arm.h"
+#include "checkers.h"
+
+enum probes_insn checker_stack_use_none(probes_opcode_t insn,
+		struct arch_probes_insn *asi,
+		const struct decode_header *h)
+{
+	asi->stack_space = 0;
+	return INSN_GOOD_NO_SLOT;
+}
+
+enum probes_insn checker_stack_use_unknown(probes_opcode_t insn,
+		struct arch_probes_insn *asi,
+		const struct decode_header *h)
+{
+	asi->stack_space = -1;
+	return INSN_GOOD_NO_SLOT;
+}
+
+#ifdef CONFIG_THUMB2_KERNEL
+enum probes_insn checker_stack_use_imm_0xx(probes_opcode_t insn,
+		struct arch_probes_insn *asi,
+		const struct decode_header *h)
+{
+	int imm = insn & 0xff;
+	asi->stack_space = imm;
+	return INSN_GOOD_NO_SLOT;
+}
+
+/*
+ * Different from other insn uses imm8, the real addressing offset of
+ * STRD in T32 encoding should be imm8 * 4. See ARMARM description.
+ */
+enum probes_insn checker_stack_use_t32strd(probes_opcode_t insn,
+		struct arch_probes_insn *asi,
+		const struct decode_header *h)
+{
+	int imm = insn & 0xff;
+	asi->stack_space = imm << 2;
+	return INSN_GOOD_NO_SLOT;
+}
+#else
+enum probes_insn checker_stack_use_imm_x0x(probes_opcode_t insn,
+		struct arch_probes_insn *asi,
+		const struct decode_header *h)
+{
+	int imm = ((insn & 0xf00) >> 4) + (insn & 0xf);
+	asi->stack_space = imm;
+	return INSN_GOOD_NO_SLOT;
+}
+#endif
+
+enum probes_insn checker_stack_use_imm_xxx(probes_opcode_t insn,
+		struct arch_probes_insn *asi,
+		const struct decode_header *h)
+{
+	int imm = insn & 0xfff;
+	asi->stack_space = imm;
+	return INSN_GOOD_NO_SLOT;
+}
+
+enum probes_insn checker_stack_use_stmdx(probes_opcode_t insn,
+		struct arch_probes_insn *asi,
+		const struct decode_header *h)
+{
+	unsigned int reglist = insn & 0xffff;
+	int pbit = insn & (1 << 24);
+	asi->stack_space = (hweight32(reglist) - (!pbit ? 1 : 0)) * 4;
+
+	return INSN_GOOD_NO_SLOT;
+}
+
+const union decode_action stack_check_actions[] = {
+	[STACK_USE_NONE] = {.decoder = checker_stack_use_none},
+	[STACK_USE_UNKNOWN] = {.decoder = checker_stack_use_unknown},
+#ifdef CONFIG_THUMB2_KERNEL
+	[STACK_USE_FIXED_0XX] = {.decoder = checker_stack_use_imm_0xx},
+	[STACK_USE_T32STRD] = {.decoder = checker_stack_use_t32strd},
+#else
+	[STACK_USE_FIXED_X0X] = {.decoder = checker_stack_use_imm_x0x},
+#endif
+	[STACK_USE_FIXED_XXX] = {.decoder = checker_stack_use_imm_xxx},
+	[STACK_USE_STMDX] = {.decoder = checker_stack_use_stmdx},
+};

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},
+};