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 
t32_check_stack(probes_opcode_t insn,struct arch_probes_insn * asi,const struct decode_header * h)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  */
t16_check_stack(probes_opcode_t insn,struct arch_probes_insn * asi,const struct decode_header * h)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