1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (C) 2020 SiFive
4 */
5
6 #include <linux/ptrace.h>
7 #include <linux/kdebug.h>
8 #include <linux/bug.h>
9 #include <linux/kgdb.h>
10 #include <linux/irqflags.h>
11 #include <linux/string.h>
12 #include <asm/cacheflush.h>
13 #include <asm/gdb_xml.h>
14 #include <asm/insn.h>
15
16 enum {
17 NOT_KGDB_BREAK = 0,
18 KGDB_SW_BREAK,
19 KGDB_COMPILED_BREAK,
20 KGDB_SW_SINGLE_STEP
21 };
22
23 static unsigned long stepped_address;
24 static unsigned int stepped_opcode;
25
26 static int decode_register_index(unsigned long opcode, int offset)
27 {
28 return (opcode >> offset) & 0x1F;
29 }
30
31 static int decode_register_index_short(unsigned long opcode, int offset)
32 {
33 return ((opcode >> offset) & 0x7) + 8;
34 }
35
36 /* Calculate the new address for after a step */
37 static int get_step_address(struct pt_regs *regs, unsigned long *next_addr)
38 {
39 unsigned long pc = regs->epc;
40 unsigned long *regs_ptr = (unsigned long *)regs;
41 unsigned int rs1_num, rs2_num;
42 int op_code;
43
44 if (get_kernel_nofault(op_code, (void *)pc))
45 return -EINVAL;
46 if ((op_code & __INSN_LENGTH_MASK) != __INSN_LENGTH_GE_32) {
47 if (riscv_insn_is_c_jalr(op_code) ||
48 riscv_insn_is_c_jr(op_code)) {
49 rs1_num = decode_register_index(op_code, RVC_C2_RS1_OPOFF);
50 *next_addr = regs_ptr[rs1_num];
51 } else if (riscv_insn_is_c_j(op_code) ||
52 riscv_insn_is_c_jal(op_code)) {
53 *next_addr = RVC_EXTRACT_JTYPE_IMM(op_code) + pc;
54 } else if (riscv_insn_is_c_beqz(op_code)) {
55 rs1_num = decode_register_index_short(op_code,
56 RVC_C1_RS1_OPOFF);
57 if (!rs1_num || regs_ptr[rs1_num] == 0)
58 *next_addr = RVC_EXTRACT_BTYPE_IMM(op_code) + pc;
59 else
60 *next_addr = pc + 2;
61 } else if (riscv_insn_is_c_bnez(op_code)) {
62 rs1_num =
63 decode_register_index_short(op_code, RVC_C1_RS1_OPOFF);
64 if (rs1_num && regs_ptr[rs1_num] != 0)
65 *next_addr = RVC_EXTRACT_BTYPE_IMM(op_code) + pc;
66 else
67 *next_addr = pc + 2;
68 } else {
69 *next_addr = pc + 2;
70 }
71 } else {
72 if ((op_code & __INSN_OPCODE_MASK) == __INSN_BRANCH_OPCODE) {
73 bool result = false;
74 long imm = RV_EXTRACT_BTYPE_IMM(op_code);
75 unsigned long rs1_val = 0, rs2_val = 0;
76
77 rs1_num = decode_register_index(op_code, RVG_RS1_OPOFF);
78 rs2_num = decode_register_index(op_code, RVG_RS2_OPOFF);
79 if (rs1_num)
80 rs1_val = regs_ptr[rs1_num];
81 if (rs2_num)
82 rs2_val = regs_ptr[rs2_num];
83
84 if (riscv_insn_is_beq(op_code))
85 result = (rs1_val == rs2_val) ? true : false;
86 else if (riscv_insn_is_bne(op_code))
87 result = (rs1_val != rs2_val) ? true : false;
88 else if (riscv_insn_is_blt(op_code))
89 result =
90 ((long)rs1_val <
91 (long)rs2_val) ? true : false;
92 else if (riscv_insn_is_bge(op_code))
93 result =
94 ((long)rs1_val >=
95 (long)rs2_val) ? true : false;
96 else if (riscv_insn_is_bltu(op_code))
97 result = (rs1_val < rs2_val) ? true : false;
98 else if (riscv_insn_is_bgeu(op_code))
99 result = (rs1_val >= rs2_val) ? true : false;
100 if (result)
101 *next_addr = imm + pc;
102 else
103 *next_addr = pc + 4;
104 } else if (riscv_insn_is_jal(op_code)) {
105 *next_addr = RV_EXTRACT_JTYPE_IMM(op_code) + pc;
106 } else if (riscv_insn_is_jalr(op_code)) {
107 rs1_num = decode_register_index(op_code, RVG_RS1_OPOFF);
108 if (rs1_num)
109 *next_addr = ((unsigned long *)regs)[rs1_num];
110 *next_addr += RV_EXTRACT_ITYPE_IMM(op_code);
111 } else if (riscv_insn_is_sret(op_code)) {
112 *next_addr = pc;
113 } else {
114 *next_addr = pc + 4;
115 }
116 }
117 return 0;
118 }
119
120 static int do_single_step(struct pt_regs *regs)
121 {
122 /* Determine where the target instruction will send us to */
123 unsigned long addr = 0;
124 int error = get_step_address(regs, &addr);
125
126 if (error)
127 return error;
128
129 /* Store the op code in the stepped address */
130 error = get_kernel_nofault(stepped_opcode, (void *)addr);
131 if (error)
132 return error;
133
134 stepped_address = addr;
135
136 /* Replace the op code with the break instruction */
137 error = copy_to_kernel_nofault((void *)stepped_address,
138 arch_kgdb_ops.gdb_bpt_instr,
139 BREAK_INSTR_SIZE);
140 /* Flush and return */
141 if (!error) {
142 flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
143 kgdb_single_step = 1;
144 atomic_set(&kgdb_cpu_doing_single_step,
145 raw_smp_processor_id());
146 } else {
147 stepped_address = 0;
148 stepped_opcode = 0;
149 }
150 return error;
151 }
152
153 /* Undo a single step */
154 static void undo_single_step(struct pt_regs *regs)
155 {
156 if (stepped_opcode != 0) {
157 copy_to_kernel_nofault((void *)stepped_address,
158 (void *)&stepped_opcode, BREAK_INSTR_SIZE);
159 flush_icache_range(stepped_address,
160 stepped_address + BREAK_INSTR_SIZE);
161 }
162 stepped_address = 0;
163 stepped_opcode = 0;
164 kgdb_single_step = 0;
165 atomic_set(&kgdb_cpu_doing_single_step, -1);
166 }
167
168 struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] = {
169 {DBG_REG_ZERO, GDB_SIZEOF_REG, -1},
170 {DBG_REG_RA, GDB_SIZEOF_REG, offsetof(struct pt_regs, ra)},
171 {DBG_REG_SP, GDB_SIZEOF_REG, offsetof(struct pt_regs, sp)},
172 {DBG_REG_GP, GDB_SIZEOF_REG, offsetof(struct pt_regs, gp)},
173 {DBG_REG_TP, GDB_SIZEOF_REG, offsetof(struct pt_regs, tp)},
174 {DBG_REG_T0, GDB_SIZEOF_REG, offsetof(struct pt_regs, t0)},
175 {DBG_REG_T1, GDB_SIZEOF_REG, offsetof(struct pt_regs, t1)},
176 {DBG_REG_T2, GDB_SIZEOF_REG, offsetof(struct pt_regs, t2)},
177 {DBG_REG_FP, GDB_SIZEOF_REG, offsetof(struct pt_regs, s0)},
178 {DBG_REG_S1, GDB_SIZEOF_REG, offsetof(struct pt_regs, a1)},
179 {DBG_REG_A0, GDB_SIZEOF_REG, offsetof(struct pt_regs, a0)},
180 {DBG_REG_A1, GDB_SIZEOF_REG, offsetof(struct pt_regs, a1)},
181 {DBG_REG_A2, GDB_SIZEOF_REG, offsetof(struct pt_regs, a2)},
182 {DBG_REG_A3, GDB_SIZEOF_REG, offsetof(struct pt_regs, a3)},
183 {DBG_REG_A4, GDB_SIZEOF_REG, offsetof(struct pt_regs, a4)},
184 {DBG_REG_A5, GDB_SIZEOF_REG, offsetof(struct pt_regs, a5)},
185 {DBG_REG_A6, GDB_SIZEOF_REG, offsetof(struct pt_regs, a6)},
186 {DBG_REG_A7, GDB_SIZEOF_REG, offsetof(struct pt_regs, a7)},
187 {DBG_REG_S2, GDB_SIZEOF_REG, offsetof(struct pt_regs, s2)},
188 {DBG_REG_S3, GDB_SIZEOF_REG, offsetof(struct pt_regs, s3)},
189 {DBG_REG_S4, GDB_SIZEOF_REG, offsetof(struct pt_regs, s4)},
190 {DBG_REG_S5, GDB_SIZEOF_REG, offsetof(struct pt_regs, s5)},
191 {DBG_REG_S6, GDB_SIZEOF_REG, offsetof(struct pt_regs, s6)},
192 {DBG_REG_S7, GDB_SIZEOF_REG, offsetof(struct pt_regs, s7)},
193 {DBG_REG_S8, GDB_SIZEOF_REG, offsetof(struct pt_regs, s8)},
194 {DBG_REG_S9, GDB_SIZEOF_REG, offsetof(struct pt_regs, s9)},
195 {DBG_REG_S10, GDB_SIZEOF_REG, offsetof(struct pt_regs, s10)},
196 {DBG_REG_S11, GDB_SIZEOF_REG, offsetof(struct pt_regs, s11)},
197 {DBG_REG_T3, GDB_SIZEOF_REG, offsetof(struct pt_regs, t3)},
198 {DBG_REG_T4, GDB_SIZEOF_REG, offsetof(struct pt_regs, t4)},
199 {DBG_REG_T5, GDB_SIZEOF_REG, offsetof(struct pt_regs, t5)},
200 {DBG_REG_T6, GDB_SIZEOF_REG, offsetof(struct pt_regs, t6)},
201 {DBG_REG_EPC, GDB_SIZEOF_REG, offsetof(struct pt_regs, epc)},
202 {DBG_REG_STATUS, GDB_SIZEOF_REG, offsetof(struct pt_regs, status)},
203 {DBG_REG_BADADDR, GDB_SIZEOF_REG, offsetof(struct pt_regs, badaddr)},
204 {DBG_REG_CAUSE, GDB_SIZEOF_REG, offsetof(struct pt_regs, cause)},
205 };
206
207 char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs)
208 {
209 if (regno >= DBG_MAX_REG_NUM || regno < 0)
210 return NULL;
211
212 if (dbg_reg_def[regno].offset != -1)
213 memcpy(mem, (void *)regs + dbg_reg_def[regno].offset,
214 dbg_reg_def[regno].size);
215 else
216 memset(mem, 0, dbg_reg_def[regno].size);
217 return dbg_reg_def[regno].name;
218 }
219
220 int dbg_set_reg(int regno, void *mem, struct pt_regs *regs)
221 {
222 if (regno >= DBG_MAX_REG_NUM || regno < 0)
223 return -EINVAL;
224
225 if (dbg_reg_def[regno].offset != -1)
226 memcpy((void *)regs + dbg_reg_def[regno].offset, mem,
227 dbg_reg_def[regno].size);
228 return 0;
229 }
230
231 void
232 sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *task)
233 {
234 /* Initialize to zero */
235 memset((char *)gdb_regs, 0, NUMREGBYTES);
236
237 gdb_regs[DBG_REG_SP_OFF] = task->thread.sp;
238 gdb_regs[DBG_REG_FP_OFF] = task->thread.s[0];
239 gdb_regs[DBG_REG_S1_OFF] = task->thread.s[1];
240 gdb_regs[DBG_REG_S2_OFF] = task->thread.s[2];
241 gdb_regs[DBG_REG_S3_OFF] = task->thread.s[3];
242 gdb_regs[DBG_REG_S4_OFF] = task->thread.s[4];
243 gdb_regs[DBG_REG_S5_OFF] = task->thread.s[5];
244 gdb_regs[DBG_REG_S6_OFF] = task->thread.s[6];
245 gdb_regs[DBG_REG_S7_OFF] = task->thread.s[7];
246 gdb_regs[DBG_REG_S8_OFF] = task->thread.s[8];
247 gdb_regs[DBG_REG_S9_OFF] = task->thread.s[10];
248 gdb_regs[DBG_REG_S10_OFF] = task->thread.s[11];
249 gdb_regs[DBG_REG_EPC_OFF] = task->thread.ra;
250 }
251
252 void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long pc)
253 {
254 regs->epc = pc;
255 }
256
257 void kgdb_arch_handle_qxfer_pkt(char *remcom_in_buffer,
258 char *remcom_out_buffer)
259 {
260 if (!strncmp(remcom_in_buffer, gdb_xfer_read_target,
261 sizeof(gdb_xfer_read_target)))
262 strcpy(remcom_out_buffer, riscv_gdb_stub_target_desc);
263 else if (!strncmp(remcom_in_buffer, gdb_xfer_read_cpuxml,
264 sizeof(gdb_xfer_read_cpuxml)))
265 strcpy(remcom_out_buffer, riscv_gdb_stub_cpuxml);
266 }
267
268 static inline void kgdb_arch_update_addr(struct pt_regs *regs,
269 char *remcom_in_buffer)
270 {
271 unsigned long addr;
272 char *ptr;
273
274 ptr = &remcom_in_buffer[1];
275 if (kgdb_hex2long(&ptr, &addr))
276 regs->epc = addr;
277 }
278
279 int kgdb_arch_handle_exception(int vector, int signo, int err_code,
280 char *remcom_in_buffer, char *remcom_out_buffer,
281 struct pt_regs *regs)
282 {
283 int err = 0;
284
285 undo_single_step(regs);
286
287 switch (remcom_in_buffer[0]) {
288 case 'c':
289 case 'D':
290 case 'k':
291 if (remcom_in_buffer[0] == 'c')
292 kgdb_arch_update_addr(regs, remcom_in_buffer);
293 break;
294 case 's':
295 kgdb_arch_update_addr(regs, remcom_in_buffer);
296 err = do_single_step(regs);
297 break;
298 default:
299 err = -1;
300 }
301 return err;
302 }
303
304 static int kgdb_riscv_kgdbbreak(unsigned long addr)
305 {
306 if (stepped_address == addr)
307 return KGDB_SW_SINGLE_STEP;
308 if (atomic_read(&kgdb_setting_breakpoint))
309 if (addr == (unsigned long)&kgdb_compiled_break)
310 return KGDB_COMPILED_BREAK;
311
312 return kgdb_has_hit_break(addr);
313 }
314
315 static int kgdb_riscv_notify(struct notifier_block *self, unsigned long cmd,
316 void *ptr)
317 {
318 struct die_args *args = (struct die_args *)ptr;
319 struct pt_regs *regs = args->regs;
320 unsigned long flags;
321 int type;
322
323 if (user_mode(regs))
324 return NOTIFY_DONE;
325
326 type = kgdb_riscv_kgdbbreak(regs->epc);
327 if (type == NOT_KGDB_BREAK && cmd == DIE_TRAP)
328 return NOTIFY_DONE;
329
330 local_irq_save(flags);
331
332 if (kgdb_handle_exception(type == KGDB_SW_SINGLE_STEP ? 0 : 1,
333 args->signr, cmd, regs))
334 return NOTIFY_DONE;
335
336 if (type == KGDB_COMPILED_BREAK)
337 regs->epc += 4;
338
339 local_irq_restore(flags);
340
341 return NOTIFY_STOP;
342 }
343
344 static struct notifier_block kgdb_notifier = {
345 .notifier_call = kgdb_riscv_notify,
346 };
347
348 int kgdb_arch_init(void)
349 {
350 register_die_notifier(&kgdb_notifier);
351
352 return 0;
353 }
354
355 void kgdb_arch_exit(void)
356 {
357 unregister_die_notifier(&kgdb_notifier);
358 }
359
360 /*
361 * Global data
362 */
363 #ifdef CONFIG_RISCV_ISA_C
364 const struct kgdb_arch arch_kgdb_ops = {
365 .gdb_bpt_instr = {0x02, 0x90}, /* c.ebreak */
366 };
367 #else
368 const struct kgdb_arch arch_kgdb_ops = {
369 .gdb_bpt_instr = {0x73, 0x00, 0x10, 0x00}, /* ebreak */
370 };
371 #endif
372
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