1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * arch/arm/probes/kprobes/checkers-thumb.c
4 *
5 * Copyright (C) 2014 Huawei Inc.
6 */
7
8 #include <linux/kernel.h>
9 #include "../decode.h"
10 #include "../decode-thumb.h"
11 #include "checkers.h"
12
13 static enum probes_insn __kprobes t32_check_stack(probes_opcode_t insn,
14 struct arch_probes_insn *asi,
15 const struct decode_header *h)
16 {
17 /*
18 * PROBES_T32_LDMSTM, PROBES_T32_LDRDSTRD and PROBES_T32_LDRSTR
19 * may get here. Simply mark all normal insns as STACK_USE_NONE.
20 */
21 static const union decode_item table[] = {
22
23 /*
24 * First, filter out all ldr insns to make our life easier.
25 * Following load insns may come here:
26 * LDM, LDRD, LDR.
27 * In T32 encoding, bit 20 is enough for distinguishing
28 * load and store. All load insns have this bit set, when
29 * all store insns have this bit clear.
30 */
31 DECODE_CUSTOM (0x00100000, 0x00100000, STACK_USE_NONE),
32
33 /*
34 * Mark all 'STR{,B,H}, Rt, [Rn, Rm]' as STACK_USE_UNKNOWN
35 * if Rn or Rm is SP. T32 doesn't encode STRD.
36 */
37 /* xx | Rn | Rt | | Rm |*/
38 /* STR (register) 1111 1000 0100 xxxx xxxx 0000 00xx xxxx */
39 /* STRB (register) 1111 1000 0000 xxxx xxxx 0000 00xx xxxx */
40 /* STRH (register) 1111 1000 0010 xxxx xxxx 0000 00xx xxxx */
41 /* INVALID INSN 1111 1000 0110 xxxx xxxx 0000 00xx xxxx */
42 /* By Introducing INVALID INSN, bit 21 and 22 can be ignored. */
43 DECODE_OR (0xff9f0fc0, 0xf80d0000),
44 DECODE_CUSTOM (0xff900fcf, 0xf800000d, STACK_USE_UNKNOWN),
45
46
47 /* xx | Rn | Rt | PUW| imm8 |*/
48 /* STR (imm 8) 1111 1000 0100 1101 xxxx 110x xxxx xxxx */
49 /* STRB (imm 8) 1111 1000 0000 1101 xxxx 110x xxxx xxxx */
50 /* STRH (imm 8) 1111 1000 0010 1101 xxxx 110x xxxx xxxx */
51 /* INVALID INSN 1111 1000 0110 1101 xxxx 110x xxxx xxxx */
52 /* Only consider U == 0 and P == 1: strx rx, [sp, #-<imm>] */
53 DECODE_CUSTOM (0xff9f0e00, 0xf80d0c00, STACK_USE_FIXED_0XX),
54
55 /* For STR{,B,H} (imm 12), offset is always positive, so ignore them. */
56
57 /* P U W | Rn | Rt | Rt2| imm8 |*/
58 /* STRD (immediate) 1110 1001 01x0 1101 xxxx xxxx xxxx xxxx */
59 /*
60 * Only consider U == 0 and P == 1.
61 * Also note that STRD in T32 encoding is special:
62 * imm = ZeroExtend(imm8:'00', 32)
63 */
64 DECODE_CUSTOM (0xffdf0000, 0xe94d0000, STACK_USE_T32STRD),
65
66 /* | Rn | */
67 /* STMDB 1110 1001 00x0 1101 xxxx xxxx xxxx xxxx */
68 DECODE_CUSTOM (0xffdf0000, 0xe90d0000, STACK_USE_STMDX),
69
70 /* fall through */
71 DECODE_CUSTOM (0, 0, STACK_USE_NONE),
72 DECODE_END
73 };
74
75 return probes_decode_insn(insn, asi, table, false, false, stack_check_actions, NULL);
76 }
77
78 const struct decode_checker t32_stack_checker[NUM_PROBES_T32_ACTIONS] = {
79 [PROBES_T32_LDMSTM] = {.checker = t32_check_stack},
80 [PROBES_T32_LDRDSTRD] = {.checker = t32_check_stack},
81 [PROBES_T32_LDRSTR] = {.checker = t32_check_stack},
82 };
83
84 /*
85 * See following comments. This insn must be 'push'.
86 */
87 static enum probes_insn __kprobes t16_check_stack(probes_opcode_t insn,
88 struct arch_probes_insn *asi,
89 const struct decode_header *h)
90 {
91 unsigned int reglist = insn & 0x1ff;
92 asi->stack_space = hweight32(reglist) * 4;
93 return INSN_GOOD;
94 }
95
96 /*
97 * T16 encoding is simple: only the 'push' insn can need extra stack space.
98 * Other insns, like str, can only use r0-r7 as Rn.
99 */
100 const struct decode_checker t16_stack_checker[NUM_PROBES_T16_ACTIONS] = {
101 [PROBES_T16_PUSH] = {.checker = t16_check_stack},
102 };
103
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