1 /*
2 * arch/arm/probes/kprobes/checkers-thumb.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-thumb.h"
19 #include "checkers.h"
20
t32_check_stack(probes_opcode_t insn,struct arch_probes_insn * asi,const struct decode_header * h)21 static enum probes_insn __kprobes t32_check_stack(probes_opcode_t insn,
22 struct arch_probes_insn *asi,
23 const struct decode_header *h)
24 {
25 /*
26 * PROBES_T32_LDMSTM, PROBES_T32_LDRDSTRD and PROBES_T32_LDRSTR
27 * may get here. Simply mark all normal insns as STACK_USE_NONE.
28 */
29 static const union decode_item table[] = {
30
31 /*
32 * First, filter out all ldr insns to make our life easier.
33 * Following load insns may come here:
34 * LDM, LDRD, LDR.
35 * In T32 encoding, bit 20 is enough for distinguishing
36 * load and store. All load insns have this bit set, when
37 * all store insns have this bit clear.
38 */
39 DECODE_CUSTOM (0x00100000, 0x00100000, STACK_USE_NONE),
40
41 /*
42 * Mark all 'STR{,B,H}, Rt, [Rn, Rm]' as STACK_USE_UNKNOWN
43 * if Rn or Rm is SP. T32 doesn't encode STRD.
44 */
45 /* xx | Rn | Rt | | Rm |*/
46 /* STR (register) 1111 1000 0100 xxxx xxxx 0000 00xx xxxx */
47 /* STRB (register) 1111 1000 0000 xxxx xxxx 0000 00xx xxxx */
48 /* STRH (register) 1111 1000 0010 xxxx xxxx 0000 00xx xxxx */
49 /* INVALID INSN 1111 1000 0110 xxxx xxxx 0000 00xx xxxx */
50 /* By Introducing INVALID INSN, bit 21 and 22 can be ignored. */
51 DECODE_OR (0xff9f0fc0, 0xf80d0000),
52 DECODE_CUSTOM (0xff900fcf, 0xf800000d, STACK_USE_UNKNOWN),
53
54
55 /* xx | Rn | Rt | PUW| imm8 |*/
56 /* STR (imm 8) 1111 1000 0100 1101 xxxx 110x xxxx xxxx */
57 /* STRB (imm 8) 1111 1000 0000 1101 xxxx 110x xxxx xxxx */
58 /* STRH (imm 8) 1111 1000 0010 1101 xxxx 110x xxxx xxxx */
59 /* INVALID INSN 1111 1000 0110 1101 xxxx 110x xxxx xxxx */
60 /* Only consider U == 0 and P == 1: strx rx, [sp, #-<imm>] */
61 DECODE_CUSTOM (0xff9f0e00, 0xf80d0c00, STACK_USE_FIXED_0XX),
62
63 /* For STR{,B,H} (imm 12), offset is always positive, so ignore them. */
64
65 /* P U W | Rn | Rt | Rt2| imm8 |*/
66 /* STRD (immediate) 1110 1001 01x0 1101 xxxx xxxx xxxx xxxx */
67 /*
68 * Only consider U == 0 and P == 1.
69 * Also note that STRD in T32 encoding is special:
70 * imm = ZeroExtend(imm8:'00', 32)
71 */
72 DECODE_CUSTOM (0xffdf0000, 0xe94d0000, STACK_USE_T32STRD),
73
74 /* | Rn | */
75 /* STMDB 1110 1001 00x0 1101 xxxx xxxx xxxx xxxx */
76 DECODE_CUSTOM (0xffdf0000, 0xe90d0000, STACK_USE_STMDX),
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 t32_stack_checker[NUM_PROBES_T32_ACTIONS] = {
87 [PROBES_T32_LDMSTM] = {.checker = t32_check_stack},
88 [PROBES_T32_LDRDSTRD] = {.checker = t32_check_stack},
89 [PROBES_T32_LDRSTR] = {.checker = t32_check_stack},
90 };
91
92 /*
93 * See following comments. This insn must be 'push'.
94 */
t16_check_stack(probes_opcode_t insn,struct arch_probes_insn * asi,const struct decode_header * h)95 static enum probes_insn __kprobes t16_check_stack(probes_opcode_t insn,
96 struct arch_probes_insn *asi,
97 const struct decode_header *h)
98 {
99 unsigned int reglist = insn & 0x1ff;
100 asi->stack_space = hweight32(reglist) * 4;
101 return INSN_GOOD;
102 }
103
104 /*
105 * T16 encoding is simple: only the 'push' insn can need extra stack space.
106 * Other insns, like str, can only use r0-r7 as Rn.
107 */
108 const struct decode_checker t16_stack_checker[NUM_PROBES_T16_ACTIONS] = {
109 [PROBES_T16_PUSH] = {.checker = t16_check_stack},
110 };
111
