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
13static 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
86const 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
93static 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
101static 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
117static 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
127static 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 */
148static 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
159const 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