1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * arch/arm/probes/kprobes/checkers-arm.c
4  *
5  * Copyright (C) 2014 Huawei Inc.
6  */
7 
8 #include <linux/kernel.h>
9 #include "../decode.h"
10 #include "../decode-arm.h"
11 #include "checkers.h"
12 
13 static enum probes_insn __kprobes arm_check_stack(probes_opcode_t insn,
14 		struct arch_probes_insn *asi,
15 		const struct decode_header *h)
16 {
17 	/*
18 	 * PROBES_LDRSTRD, PROBES_LDMSTM, PROBES_STORE,
19 	 * PROBES_STORE_EXTRA may get here. Simply mark all normal
20 	 * insns as STACK_USE_NONE.
21 	 */
22 	static const union decode_item table[] = {
23 		/*
24 		 * 'STR{,D,B,H}, Rt, [Rn, Rm]' should be marked as UNKNOWN
25 		 * if Rn or Rm is SP.
26 		 *                                 x
27 		 * STR (register)	cccc 011x x0x0 xxxx xxxx xxxx xxxx xxxx
28 		 * STRB (register)	cccc 011x x1x0 xxxx xxxx xxxx xxxx xxxx
29 		 */
30 		DECODE_OR	(0x0e10000f, 0x0600000d),
31 		DECODE_OR	(0x0e1f0000, 0x060d0000),
32 
33 		/*
34 		 *                                                     x
35 		 * STRD (register)	cccc 000x x0x0 xxxx xxxx xxxx 1111 xxxx
36 		 * STRH (register)	cccc 000x x0x0 xxxx xxxx xxxx 1011 xxxx
37 		 */
38 		DECODE_OR	(0x0e5000bf, 0x000000bd),
39 		DECODE_CUSTOM	(0x0e5f00b0, 0x000d00b0, STACK_USE_UNKNOWN),
40 
41 		/*
42 		 * For PROBES_LDMSTM, only stmdx sp, [...] need to examine
43 		 *
44 		 * Bit B/A (bit 24) encodes arithmetic operation order. 1 means
45 		 * before, 0 means after.
46 		 * Bit I/D (bit 23) encodes arithmetic operation. 1 means
47 		 * increment, 0 means decrement.
48 		 *
49 		 * So:
50 		 *                              B I
51 		 *                              / /
52 		 *                              A D   | Rn |
53 		 * STMDX SP, [...]	cccc 100x 00x0 xxxx xxxx xxxx xxxx xxxx
54 		 */
55 		DECODE_CUSTOM	(0x0edf0000, 0x080d0000, STACK_USE_STMDX),
56 
57 		/*                              P U W | Rn | Rt |     imm12    |*/
58 		/* STR (immediate)	cccc 010x x0x0 1101 xxxx xxxx xxxx xxxx */
59 		/* STRB (immediate)	cccc 010x x1x0 1101 xxxx xxxx xxxx xxxx */
60 		/*                              P U W | Rn | Rt |imm4|    |imm4|*/
61 		/* STRD (immediate)	cccc 000x x1x0 1101 xxxx xxxx 1111 xxxx */
62 		/* STRH (immediate)	cccc 000x x1x0 1101 xxxx xxxx 1011 xxxx */
63 		/*
64 		 * index = (P == '1'); add = (U == '1').
65 		 * Above insns with:
66 		 *    index == 0 (str{,d,h} rx, [sp], #+/-imm) or
67 		 *    add == 1 (str{,d,h} rx, [sp, #+<imm>])
68 		 * should be STACK_USE_NONE.
69 		 * Only str{,b,d,h} rx,[sp,#-n] (P == 1 and U == 0) are
70 		 * required to be examined.
71 		 */
72 		/* STR{,B} Rt,[SP,#-n]	cccc 0101 0xx0 1101 xxxx xxxx xxxx xxxx */
73 		DECODE_CUSTOM	(0x0f9f0000, 0x050d0000, STACK_USE_FIXED_XXX),
74 
75 		/* STR{D,H} Rt,[SP,#-n]	cccc 0001 01x0 1101 xxxx xxxx 1x11 xxxx */
76 		DECODE_CUSTOM	(0x0fdf00b0, 0x014d00b0, STACK_USE_FIXED_X0X),
77 
78 		/* fall through */
79 		DECODE_CUSTOM	(0, 0, STACK_USE_NONE),
80 		DECODE_END
81 	};
82 
83 	return probes_decode_insn(insn, asi, table, false, false, stack_check_actions, NULL);
84 }
85 
86 const struct decode_checker arm_stack_checker[NUM_PROBES_ARM_ACTIONS] = {
87 	[PROBES_LDRSTRD] = {.checker = arm_check_stack},
88 	[PROBES_STORE_EXTRA] = {.checker = arm_check_stack},
89 	[PROBES_STORE] = {.checker = arm_check_stack},
90 	[PROBES_LDMSTM] = {.checker = arm_check_stack},
91 };
92 
93 static enum probes_insn __kprobes arm_check_regs_nouse(probes_opcode_t insn,
94 		struct arch_probes_insn *asi,
95 		const struct decode_header *h)
96 {
97 	asi->register_usage_flags = 0;
98 	return INSN_GOOD;
99 }
100 
101 static enum probes_insn arm_check_regs_normal(probes_opcode_t insn,
102 		struct arch_probes_insn *asi,
103 		const struct decode_header *h)
104 {
105 	u32 regs = h->type_regs.bits >> DECODE_TYPE_BITS;
106 	int i;
107 
108 	asi->register_usage_flags = 0;
109 	for (i = 0; i < 5; regs >>= 4, insn >>= 4, i++)
110 		if (regs & 0xf)
111 			asi->register_usage_flags |= 1 << (insn & 0xf);
112 
113 	return INSN_GOOD;
114 }
115 
116 
117 static enum probes_insn arm_check_regs_ldmstm(probes_opcode_t insn,
118 		struct arch_probes_insn *asi,
119 		const struct decode_header *h)
120 {
121 	unsigned int reglist = insn & 0xffff;
122 	unsigned int rn = (insn >> 16) & 0xf;
123 	asi->register_usage_flags = reglist | (1 << rn);
124 	return INSN_GOOD;
125 }
126 
127 static enum probes_insn arm_check_regs_mov_ip_sp(probes_opcode_t insn,
128 		struct arch_probes_insn *asi,
129 		const struct decode_header *h)
130 {
131 	/* Instruction is 'mov ip, sp' i.e. 'mov r12, r13' */
132 	asi->register_usage_flags = (1 << 12) | (1<< 13);
133 	return INSN_GOOD;
134 }
135 
136 /*
137  *                                    | Rn |Rt/d|         | Rm |
138  * LDRD (register)      cccc 000x x0x0 xxxx xxxx xxxx 1101 xxxx
139  * STRD (register)      cccc 000x x0x0 xxxx xxxx xxxx 1111 xxxx
140  *                                    | Rn |Rt/d|         |imm4L|
141  * LDRD (immediate)     cccc 000x x1x0 xxxx xxxx xxxx 1101 xxxx
142  * STRD (immediate)     cccc 000x x1x0 xxxx xxxx xxxx 1111 xxxx
143  *
144  * Such instructions access Rt/d and its next register, so different
145  * from others, a specific checker is required to handle this extra
146  * implicit register usage.
147  */
148 static enum probes_insn arm_check_regs_ldrdstrd(probes_opcode_t insn,
149 		struct arch_probes_insn *asi,
150 		const struct decode_header *h)
151 {
152 	int rdt = (insn >> 12) & 0xf;
153 	arm_check_regs_normal(insn, asi, h);
154 	asi->register_usage_flags |= 1 << (rdt + 1);
155 	return INSN_GOOD;
156 }
157 
158 
159 const struct decode_checker arm_regs_checker[NUM_PROBES_ARM_ACTIONS] = {
160 	[PROBES_MRS] = {.checker = arm_check_regs_normal},
161 	[PROBES_SATURATING_ARITHMETIC] = {.checker = arm_check_regs_normal},
162 	[PROBES_MUL1] = {.checker = arm_check_regs_normal},
163 	[PROBES_MUL2] = {.checker = arm_check_regs_normal},
164 	[PROBES_MUL_ADD_LONG] = {.checker = arm_check_regs_normal},
165 	[PROBES_MUL_ADD] = {.checker = arm_check_regs_normal},
166 	[PROBES_LOAD] = {.checker = arm_check_regs_normal},
167 	[PROBES_LOAD_EXTRA] = {.checker = arm_check_regs_normal},
168 	[PROBES_STORE] = {.checker = arm_check_regs_normal},
169 	[PROBES_STORE_EXTRA] = {.checker = arm_check_regs_normal},
170 	[PROBES_DATA_PROCESSING_REG] = {.checker = arm_check_regs_normal},
171 	[PROBES_DATA_PROCESSING_IMM] = {.checker = arm_check_regs_normal},
172 	[PROBES_SEV] = {.checker = arm_check_regs_nouse},
173 	[PROBES_WFE] = {.checker = arm_check_regs_nouse},
174 	[PROBES_SATURATE] = {.checker = arm_check_regs_normal},
175 	[PROBES_REV] = {.checker = arm_check_regs_normal},
176 	[PROBES_MMI] = {.checker = arm_check_regs_normal},
177 	[PROBES_PACK] = {.checker = arm_check_regs_normal},
178 	[PROBES_EXTEND] = {.checker = arm_check_regs_normal},
179 	[PROBES_EXTEND_ADD] = {.checker = arm_check_regs_normal},
180 	[PROBES_BITFIELD] = {.checker = arm_check_regs_normal},
181 	[PROBES_LDMSTM] = {.checker = arm_check_regs_ldmstm},
182 	[PROBES_MOV_IP_SP] = {.checker = arm_check_regs_mov_ip_sp},
183 	[PROBES_LDRSTRD] = {.checker = arm_check_regs_ldrdstrd},
184 };
185