1 // SPDX-License-Identifier: GPL-2.0+
2 
3 #include <linux/bitops.h>
4 #include <linux/kernel.h>
5 #include <linux/kprobes.h>
6 
7 #include "decode-insn.h"
8 #include "simulate-insn.h"
9 
10 static inline bool rv_insn_reg_get_val(struct pt_regs *regs, u32 index,
11 				       unsigned long *ptr)
12 {
13 	if (index == 0)
14 		*ptr = 0;
15 	else if (index <= 31)
16 		*ptr = *((unsigned long *)regs + index);
17 	else
18 		return false;
19 
20 	return true;
21 }
22 
23 static inline bool rv_insn_reg_set_val(struct pt_regs *regs, u32 index,
24 				       unsigned long val)
25 {
26 	if (index == 0)
27 		return false;
28 	else if (index <= 31)
29 		*((unsigned long *)regs + index) = val;
30 	else
31 		return false;
32 
33 	return true;
34 }
35 
36 bool __kprobes simulate_jal(u32 opcode, unsigned long addr, struct pt_regs *regs)
37 {
38 	/*
39 	 *     31    30       21    20     19        12 11 7 6      0
40 	 * imm [20] | imm[10:1] | imm[11] | imm[19:12] | rd | opcode
41 	 *     1         10          1           8       5    JAL/J
42 	 */
43 	bool ret;
44 	u32 imm;
45 	u32 index = (opcode >> 7) & 0x1f;
46 
47 	ret = rv_insn_reg_set_val(regs, index, addr + 4);
48 	if (!ret)
49 		return ret;
50 
51 	imm  = ((opcode >> 21) & 0x3ff) << 1;
52 	imm |= ((opcode >> 20) & 0x1)   << 11;
53 	imm |= ((opcode >> 12) & 0xff)  << 12;
54 	imm |= ((opcode >> 31) & 0x1)   << 20;
55 
56 	instruction_pointer_set(regs, addr + sign_extend32((imm), 20));
57 
58 	return ret;
59 }
60 
61 bool __kprobes simulate_jalr(u32 opcode, unsigned long addr, struct pt_regs *regs)
62 {
63 	/*
64 	 * 31          20 19 15 14 12 11 7 6      0
65 	 *  offset[11:0] | rs1 | 010 | rd | opcode
66 	 *      12         5      3    5    JALR/JR
67 	 */
68 	bool ret;
69 	unsigned long base_addr;
70 	u32 imm = (opcode >> 20) & 0xfff;
71 	u32 rd_index = (opcode >> 7) & 0x1f;
72 	u32 rs1_index = (opcode >> 15) & 0x1f;
73 
74 	ret = rv_insn_reg_set_val(regs, rd_index, addr + 4);
75 	if (!ret)
76 		return ret;
77 
78 	ret = rv_insn_reg_get_val(regs, rs1_index, &base_addr);
79 	if (!ret)
80 		return ret;
81 
82 	instruction_pointer_set(regs, (base_addr + sign_extend32((imm), 11))&~1);
83 
84 	return ret;
85 }
86 
87 #define auipc_rd_idx(opcode) \
88 	((opcode >> 7) & 0x1f)
89 
90 #define auipc_imm(opcode) \
91 	((((opcode) >> 12) & 0xfffff) << 12)
92 
93 #if __riscv_xlen == 64
94 #define auipc_offset(opcode)	sign_extend64(auipc_imm(opcode), 31)
95 #elif __riscv_xlen == 32
96 #define auipc_offset(opcode)	auipc_imm(opcode)
97 #else
98 #error "Unexpected __riscv_xlen"
99 #endif
100 
101 bool __kprobes simulate_auipc(u32 opcode, unsigned long addr, struct pt_regs *regs)
102 {
103 	/*
104 	 * auipc instruction:
105 	 *  31        12 11 7 6      0
106 	 * | imm[31:12] | rd | opcode |
107 	 *        20       5     7
108 	 */
109 
110 	u32 rd_idx = auipc_rd_idx(opcode);
111 	unsigned long rd_val = addr + auipc_offset(opcode);
112 
113 	if (!rv_insn_reg_set_val(regs, rd_idx, rd_val))
114 		return false;
115 
116 	instruction_pointer_set(regs, addr + 4);
117 
118 	return true;
119 }
120 
121 #define branch_rs1_idx(opcode) \
122 	(((opcode) >> 15) & 0x1f)
123 
124 #define branch_rs2_idx(opcode) \
125 	(((opcode) >> 20) & 0x1f)
126 
127 #define branch_funct3(opcode) \
128 	(((opcode) >> 12) & 0x7)
129 
130 #define branch_imm(opcode) \
131 	(((((opcode) >>  8) & 0xf ) <<  1) | \
132 	 ((((opcode) >> 25) & 0x3f) <<  5) | \
133 	 ((((opcode) >>  7) & 0x1 ) << 11) | \
134 	 ((((opcode) >> 31) & 0x1 ) << 12))
135 
136 #define branch_offset(opcode) \
137 	sign_extend32((branch_imm(opcode)), 12)
138 
139 #define BRANCH_BEQ	0x0
140 #define BRANCH_BNE	0x1
141 #define BRANCH_BLT	0x4
142 #define BRANCH_BGE	0x5
143 #define BRANCH_BLTU	0x6
144 #define BRANCH_BGEU	0x7
145 
146 bool __kprobes simulate_branch(u32 opcode, unsigned long addr, struct pt_regs *regs)
147 {
148 	/*
149 	 * branch instructions:
150 	 *      31    30       25 24 20 19 15 14    12 11       8    7      6      0
151 	 * | imm[12] | imm[10:5] | rs2 | rs1 | funct3 | imm[4:1] | imm[11] | opcode |
152 	 *     1           6        5     5      3         4         1         7
153 	 *     imm[12|10:5]        rs2   rs1    000       imm[4:1|11]       1100011  BEQ
154 	 *     imm[12|10:5]        rs2   rs1    001       imm[4:1|11]       1100011  BNE
155 	 *     imm[12|10:5]        rs2   rs1    100       imm[4:1|11]       1100011  BLT
156 	 *     imm[12|10:5]        rs2   rs1    101       imm[4:1|11]       1100011  BGE
157 	 *     imm[12|10:5]        rs2   rs1    110       imm[4:1|11]       1100011  BLTU
158 	 *     imm[12|10:5]        rs2   rs1    111       imm[4:1|11]       1100011  BGEU
159 	 */
160 
161 	s32 offset;
162 	s32 offset_tmp;
163 	unsigned long rs1_val;
164 	unsigned long rs2_val;
165 
166 	if (!rv_insn_reg_get_val(regs, branch_rs1_idx(opcode), &rs1_val) ||
167 	    !rv_insn_reg_get_val(regs, branch_rs2_idx(opcode), &rs2_val))
168 		return false;
169 
170 	offset_tmp = branch_offset(opcode);
171 	switch (branch_funct3(opcode)) {
172 	case BRANCH_BEQ:
173 		offset = (rs1_val == rs2_val) ? offset_tmp : 4;
174 		break;
175 	case BRANCH_BNE:
176 		offset = (rs1_val != rs2_val) ? offset_tmp : 4;
177 		break;
178 	case BRANCH_BLT:
179 		offset = ((long)rs1_val < (long)rs2_val) ? offset_tmp : 4;
180 		break;
181 	case BRANCH_BGE:
182 		offset = ((long)rs1_val >= (long)rs2_val) ? offset_tmp : 4;
183 		break;
184 	case BRANCH_BLTU:
185 		offset = (rs1_val < rs2_val) ? offset_tmp : 4;
186 		break;
187 	case BRANCH_BGEU:
188 		offset = (rs1_val >= rs2_val) ? offset_tmp : 4;
189 		break;
190 	default:
191 		return false;
192 	}
193 
194 	instruction_pointer_set(regs, addr + offset);
195 
196 	return true;
197 }
198