1 /*
2  * arch/arm/probes/kprobes/checkers-arm.c
3  *
4  * Copyright (C) 2014 Huawei Inc.
5  *
6  * This program is free software; you can redistribute it and/or modify
7  * it under the terms of the GNU General Public License version 2 as
8  * published by the Free Software Foundation.
9  *
10  * This program is distributed in the hope that it will be useful,
11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13  * General Public License for more details.
14  */
15 
16 #include <linux/kernel.h>
17 #include "../decode.h"
18 #include "../decode-arm.h"
19 #include "checkers.h"
20 
21 static enum probes_insn __kprobes arm_check_stack(probes_opcode_t insn,
22 		struct arch_probes_insn *asi,
23 		const struct decode_header *h)
24 {
25 	/*
26 	 * PROBES_LDRSTRD, PROBES_LDMSTM, PROBES_STORE,
27 	 * PROBES_STORE_EXTRA may get here. Simply mark all normal
28 	 * insns as STACK_USE_NONE.
29 	 */
30 	static const union decode_item table[] = {
31 		/*
32 		 * 'STR{,D,B,H}, Rt, [Rn, Rm]' should be marked as UNKNOWN
33 		 * if Rn or Rm is SP.
34 		 *                                 x
35 		 * STR (register)	cccc 011x x0x0 xxxx xxxx xxxx xxxx xxxx
36 		 * STRB (register)	cccc 011x x1x0 xxxx xxxx xxxx xxxx xxxx
37 		 */
38 		DECODE_OR	(0x0e10000f, 0x0600000d),
39 		DECODE_OR	(0x0e1f0000, 0x060d0000),
40 
41 		/*
42 		 *                                                     x
43 		 * STRD (register)	cccc 000x x0x0 xxxx xxxx xxxx 1111 xxxx
44 		 * STRH (register)	cccc 000x x0x0 xxxx xxxx xxxx 1011 xxxx
45 		 */
46 		DECODE_OR	(0x0e5000bf, 0x000000bd),
47 		DECODE_CUSTOM	(0x0e5f00b0, 0x000d00b0, STACK_USE_UNKNOWN),
48 
49 		/*
50 		 * For PROBES_LDMSTM, only stmdx sp, [...] need to examine
51 		 *
52 		 * Bit B/A (bit 24) encodes arithmetic operation order. 1 means
53 		 * before, 0 means after.
54 		 * Bit I/D (bit 23) encodes arithmetic operation. 1 means
55 		 * increment, 0 means decrement.
56 		 *
57 		 * So:
58 		 *                              B I
59 		 *                              / /
60 		 *                              A D   | Rn |
61 		 * STMDX SP, [...]	cccc 100x 00x0 xxxx xxxx xxxx xxxx xxxx
62 		 */
63 		DECODE_CUSTOM	(0x0edf0000, 0x080d0000, STACK_USE_STMDX),
64 
65 		/*                              P U W | Rn | Rt |     imm12    |*/
66 		/* STR (immediate)	cccc 010x x0x0 1101 xxxx xxxx xxxx xxxx */
67 		/* STRB (immediate)	cccc 010x x1x0 1101 xxxx xxxx xxxx xxxx */
68 		/*                              P U W | Rn | Rt |imm4|    |imm4|*/
69 		/* STRD (immediate)	cccc 000x x1x0 1101 xxxx xxxx 1111 xxxx */
70 		/* STRH (immediate)	cccc 000x x1x0 1101 xxxx xxxx 1011 xxxx */
71 		/*
72 		 * index = (P == '1'); add = (U == '1').
73 		 * Above insns with:
74 		 *    index == 0 (str{,d,h} rx, [sp], #+/-imm) or
75 		 *    add == 1 (str{,d,h} rx, [sp, #+<imm>])
76 		 * should be STACK_USE_NONE.
77 		 * Only str{,b,d,h} rx,[sp,#-n] (P == 1 and U == 0) are
78 		 * required to be examined.
79 		 */
80 		/* STR{,B} Rt,[SP,#-n]	cccc 0101 0xx0 1101 xxxx xxxx xxxx xxxx */
81 		DECODE_CUSTOM	(0x0f9f0000, 0x050d0000, STACK_USE_FIXED_XXX),
82 
83 		/* STR{D,H} Rt,[SP,#-n]	cccc 0001 01x0 1101 xxxx xxxx 1x11 xxxx */
84 		DECODE_CUSTOM	(0x0fdf00b0, 0x014d00b0, STACK_USE_FIXED_X0X),
85 
86 		/* fall through */
87 		DECODE_CUSTOM	(0, 0, STACK_USE_NONE),
88 		DECODE_END
89 	};
90 
91 	return probes_decode_insn(insn, asi, table, false, false, stack_check_actions, NULL);
92 }
93 
94 const struct decode_checker arm_stack_checker[NUM_PROBES_ARM_ACTIONS] = {
95 	[PROBES_LDRSTRD] = {.checker = arm_check_stack},
96 	[PROBES_STORE_EXTRA] = {.checker = arm_check_stack},
97 	[PROBES_STORE] = {.checker = arm_check_stack},
98 	[PROBES_LDMSTM] = {.checker = arm_check_stack},
99 };
100 
101 static enum probes_insn __kprobes arm_check_regs_nouse(probes_opcode_t insn,
102 		struct arch_probes_insn *asi,
103 		const struct decode_header *h)
104 {
105 	asi->register_usage_flags = 0;
106 	return INSN_GOOD;
107 }
108 
109 static enum probes_insn arm_check_regs_normal(probes_opcode_t insn,
110 		struct arch_probes_insn *asi,
111 		const struct decode_header *h)
112 {
113 	u32 regs = h->type_regs.bits >> DECODE_TYPE_BITS;
114 	int i;
115 
116 	asi->register_usage_flags = 0;
117 	for (i = 0; i < 5; regs >>= 4, insn >>= 4, i++)
118 		if (regs & 0xf)
119 			asi->register_usage_flags |= 1 << (insn & 0xf);
120 
121 	return INSN_GOOD;
122 }
123 
124 
125 static enum probes_insn arm_check_regs_ldmstm(probes_opcode_t insn,
126 		struct arch_probes_insn *asi,
127 		const struct decode_header *h)
128 {
129 	unsigned int reglist = insn & 0xffff;
130 	unsigned int rn = (insn >> 16) & 0xf;
131 	asi->register_usage_flags = reglist | (1 << rn);
132 	return INSN_GOOD;
133 }
134 
135 static enum probes_insn arm_check_regs_mov_ip_sp(probes_opcode_t insn,
136 		struct arch_probes_insn *asi,
137 		const struct decode_header *h)
138 {
139 	/* Instruction is 'mov ip, sp' i.e. 'mov r12, r13' */
140 	asi->register_usage_flags = (1 << 12) | (1<< 13);
141 	return INSN_GOOD;
142 }
143 
144 /*
145  *                                    | Rn |Rt/d|         | Rm |
146  * LDRD (register)      cccc 000x x0x0 xxxx xxxx xxxx 1101 xxxx
147  * STRD (register)      cccc 000x x0x0 xxxx xxxx xxxx 1111 xxxx
148  *                                    | Rn |Rt/d|         |imm4L|
149  * LDRD (immediate)     cccc 000x x1x0 xxxx xxxx xxxx 1101 xxxx
150  * STRD (immediate)     cccc 000x x1x0 xxxx xxxx xxxx 1111 xxxx
151  *
152  * Such instructions access Rt/d and its next register, so different
153  * from others, a specific checker is required to handle this extra
154  * implicit register usage.
155  */
156 static enum probes_insn arm_check_regs_ldrdstrd(probes_opcode_t insn,
157 		struct arch_probes_insn *asi,
158 		const struct decode_header *h)
159 {
160 	int rdt = (insn >> 12) & 0xf;
161 	arm_check_regs_normal(insn, asi, h);
162 	asi->register_usage_flags |= 1 << (rdt + 1);
163 	return INSN_GOOD;
164 }
165 
166 
167 const struct decode_checker arm_regs_checker[NUM_PROBES_ARM_ACTIONS] = {
168 	[PROBES_MRS] = {.checker = arm_check_regs_normal},
169 	[PROBES_SATURATING_ARITHMETIC] = {.checker = arm_check_regs_normal},
170 	[PROBES_MUL1] = {.checker = arm_check_regs_normal},
171 	[PROBES_MUL2] = {.checker = arm_check_regs_normal},
172 	[PROBES_MUL_ADD_LONG] = {.checker = arm_check_regs_normal},
173 	[PROBES_MUL_ADD] = {.checker = arm_check_regs_normal},
174 	[PROBES_LOAD] = {.checker = arm_check_regs_normal},
175 	[PROBES_LOAD_EXTRA] = {.checker = arm_check_regs_normal},
176 	[PROBES_STORE] = {.checker = arm_check_regs_normal},
177 	[PROBES_STORE_EXTRA] = {.checker = arm_check_regs_normal},
178 	[PROBES_DATA_PROCESSING_REG] = {.checker = arm_check_regs_normal},
179 	[PROBES_DATA_PROCESSING_IMM] = {.checker = arm_check_regs_normal},
180 	[PROBES_SEV] = {.checker = arm_check_regs_nouse},
181 	[PROBES_WFE] = {.checker = arm_check_regs_nouse},
182 	[PROBES_SATURATE] = {.checker = arm_check_regs_normal},
183 	[PROBES_REV] = {.checker = arm_check_regs_normal},
184 	[PROBES_MMI] = {.checker = arm_check_regs_normal},
185 	[PROBES_PACK] = {.checker = arm_check_regs_normal},
186 	[PROBES_EXTEND] = {.checker = arm_check_regs_normal},
187 	[PROBES_EXTEND_ADD] = {.checker = arm_check_regs_normal},
188 	[PROBES_BITFIELD] = {.checker = arm_check_regs_normal},
189 	[PROBES_LDMSTM] = {.checker = arm_check_regs_ldmstm},
190 	[PROBES_MOV_IP_SP] = {.checker = arm_check_regs_mov_ip_sp},
191 	[PROBES_LDRSTRD] = {.checker = arm_check_regs_ldrdstrd},
192 };
193