arch/riscv/kernel/kgdb.c

   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/parse_asm.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 #if __riscv_xlen == 32
  27 /* C.JAL is an RV32C-only instruction */
  28 DECLARE_INSN(c_jal, MATCH_C_JAL, MASK_C_JAL)
  29 #else
  30 #define is_c_jal_insn(opcode) 0
  31 #endif
  32 DECLARE_INSN(jalr, MATCH_JALR, MASK_JALR)
  33 DECLARE_INSN(jal, MATCH_JAL, MASK_JAL)
  34 DECLARE_INSN(c_jr, MATCH_C_JR, MASK_C_JR)
  35 DECLARE_INSN(c_jalr, MATCH_C_JALR, MASK_C_JALR)
  36 DECLARE_INSN(c_j, MATCH_C_J, MASK_C_J)
  37 DECLARE_INSN(beq, MATCH_BEQ, MASK_BEQ)
  38 DECLARE_INSN(bne, MATCH_BNE, MASK_BNE)
  39 DECLARE_INSN(blt, MATCH_BLT, MASK_BLT)
  40 DECLARE_INSN(bge, MATCH_BGE, MASK_BGE)
  41 DECLARE_INSN(bltu, MATCH_BLTU, MASK_BLTU)
  42 DECLARE_INSN(bgeu, MATCH_BGEU, MASK_BGEU)
  43 DECLARE_INSN(c_beqz, MATCH_C_BEQZ, MASK_C_BEQZ)
  44 DECLARE_INSN(c_bnez, MATCH_C_BNEZ, MASK_C_BNEZ)
  45 DECLARE_INSN(sret, MATCH_SRET, MASK_SRET)
  46
  47 static int decode_register_index(unsigned long opcode, int offset)
  48 {
  49         return (opcode >> offset) & 0x1F;
  50 }
  51
  52 static int decode_register_index_short(unsigned long opcode, int offset)
  53 {
  54         return ((opcode >> offset) & 0x7) + 8;
  55 }
  56
  57 /* Calculate the new address for after a step */
  58 static int get_step_address(struct pt_regs *regs, unsigned long *next_addr)
  59 {
  60         unsigned long pc = regs->epc;
  61         unsigned long *regs_ptr = (unsigned long *)regs;
  62         unsigned int rs1_num, rs2_num;
  63         int op_code;
  64
  65         if (get_kernel_nofault(op_code, (void *)pc))
  66                 return -EINVAL;
  67         if ((op_code & __INSN_LENGTH_MASK) != __INSN_LENGTH_GE_32) {
  68                 if (is_c_jalr_insn(op_code) || is_c_jr_insn(op_code)) {
  69                         rs1_num = decode_register_index(op_code, RVC_C2_RS1_OPOFF);
  70                         *next_addr = regs_ptr[rs1_num];
  71                 } else if (is_c_j_insn(op_code) || is_c_jal_insn(op_code)) {
  72                         *next_addr = EXTRACT_RVC_J_IMM(op_code) + pc;
  73                 } else if (is_c_beqz_insn(op_code)) {
  74                         rs1_num = decode_register_index_short(op_code,
  75                                                               RVC_C1_RS1_OPOFF);
  76                         if (!rs1_num || regs_ptr[rs1_num] == 0)
  77                                 *next_addr = EXTRACT_RVC_B_IMM(op_code) + pc;
  78                         else
  79                                 *next_addr = pc + 2;
  80                 } else if (is_c_bnez_insn(op_code)) {
  81                         rs1_num =
  82                             decode_register_index_short(op_code, RVC_C1_RS1_OPOFF);
  83                         if (rs1_num && regs_ptr[rs1_num] != 0)
  84                                 *next_addr = EXTRACT_RVC_B_IMM(op_code) + pc;
  85                         else
  86                                 *next_addr = pc + 2;
  87                 } else {
  88                         *next_addr = pc + 2;
  89                 }
  90         } else {
  91                 if ((op_code & __INSN_OPCODE_MASK) == __INSN_BRANCH_OPCODE) {
  92                         bool result = false;
  93                         long imm = EXTRACT_BTYPE_IMM(op_code);
  94                         unsigned long rs1_val = 0, rs2_val = 0;
  95
  96                         rs1_num = decode_register_index(op_code, RVG_RS1_OPOFF);
  97                         rs2_num = decode_register_index(op_code, RVG_RS2_OPOFF);
  98                         if (rs1_num)
  99                                 rs1_val = regs_ptr[rs1_num];
 100                         if (rs2_num)
 101                                 rs2_val = regs_ptr[rs2_num];
 102
 103                         if (is_beq_insn(op_code))
 104                                 result = (rs1_val == rs2_val) ? true : false;
 105                         else if (is_bne_insn(op_code))
 106                                 result = (rs1_val != rs2_val) ? true : false;
 107                         else if (is_blt_insn(op_code))
 108                                 result =
 109                                     ((long)rs1_val <
 110                                      (long)rs2_val) ? true : false;
 111                         else if (is_bge_insn(op_code))
 112                                 result =
 113                                     ((long)rs1_val >=
 114                                      (long)rs2_val) ? true : false;
 115                         else if (is_bltu_insn(op_code))
 116                                 result = (rs1_val < rs2_val) ? true : false;
 117                         else if (is_bgeu_insn(op_code))
 118                                 result = (rs1_val >= rs2_val) ? true : false;
 119                         if (result)
 120                                 *next_addr = imm + pc;
 121                         else
 122                                 *next_addr = pc + 4;
 123                 } else if (is_jal_insn(op_code)) {
 124                         *next_addr = EXTRACT_JTYPE_IMM(op_code) + pc;
 125                 } else if (is_jalr_insn(op_code)) {
 126                         rs1_num = decode_register_index(op_code, RVG_RS1_OPOFF);
 127                         if (rs1_num)
 128                                 *next_addr = ((unsigned long *)regs)[rs1_num];
 129                         *next_addr += EXTRACT_ITYPE_IMM(op_code);
 130                 } else if (is_sret_insn(op_code)) {
 131                         *next_addr = pc;
 132                 } else {
 133                         *next_addr = pc + 4;
 134                 }
 135         }
 136         return 0;
 137 }
 138
 139 static int do_single_step(struct pt_regs *regs)
 140 {
 141         /* Determine where the target instruction will send us to */
 142         unsigned long addr = 0;
 143         int error = get_step_address(regs, &addr);
 144
 145         if (error)
 146                 return error;
 147
 148         /* Store the op code in the stepped address */
 149         error = get_kernel_nofault(stepped_opcode, (void *)addr);
 150         if (error)
 151                 return error;
 152
 153         stepped_address = addr;
 154
 155         /* Replace the op code with the break instruction */
 156         error = copy_to_kernel_nofault((void *)stepped_address,
 157                                    arch_kgdb_ops.gdb_bpt_instr,
 158                                    BREAK_INSTR_SIZE);
 159         /* Flush and return */
 160         if (!error) {
 161                 flush_icache_range(addr, addr + BREAK_INSTR_SIZE);
 162                 kgdb_single_step = 1;
 163                 atomic_set(&kgdb_cpu_doing_single_step,
 164                            raw_smp_processor_id());
 165         } else {
 166                 stepped_address = 0;
 167                 stepped_opcode = 0;
 168         }
 169         return error;
 170 }
 171
 172 /* Undo a single step */
 173 static void undo_single_step(struct pt_regs *regs)
 174 {
 175         if (stepped_opcode != 0) {
 176                 copy_to_kernel_nofault((void *)stepped_address,
 177                                    (void *)&stepped_opcode, BREAK_INSTR_SIZE);
 178                 flush_icache_range(stepped_address,
 179                                    stepped_address + BREAK_INSTR_SIZE);
 180         }
 181         stepped_address = 0;
 182         stepped_opcode = 0;
 183         kgdb_single_step = 0;
 184         atomic_set(&kgdb_cpu_doing_single_step, -1);
 185 }
 186
 187 struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] = {
 188         {DBG_REG_ZERO, GDB_SIZEOF_REG, -1},
 189         {DBG_REG_RA, GDB_SIZEOF_REG, offsetof(struct pt_regs, ra)},
 190         {DBG_REG_SP, GDB_SIZEOF_REG, offsetof(struct pt_regs, sp)},
 191         {DBG_REG_GP, GDB_SIZEOF_REG, offsetof(struct pt_regs, gp)},
 192         {DBG_REG_TP, GDB_SIZEOF_REG, offsetof(struct pt_regs, tp)},
 193         {DBG_REG_T0, GDB_SIZEOF_REG, offsetof(struct pt_regs, t0)},
 194         {DBG_REG_T1, GDB_SIZEOF_REG, offsetof(struct pt_regs, t1)},
 195         {DBG_REG_T2, GDB_SIZEOF_REG, offsetof(struct pt_regs, t2)},
 196         {DBG_REG_FP, GDB_SIZEOF_REG, offsetof(struct pt_regs, s0)},
 197         {DBG_REG_S1, GDB_SIZEOF_REG, offsetof(struct pt_regs, a1)},
 198         {DBG_REG_A0, GDB_SIZEOF_REG, offsetof(struct pt_regs, a0)},
 199         {DBG_REG_A1, GDB_SIZEOF_REG, offsetof(struct pt_regs, a1)},
 200         {DBG_REG_A2, GDB_SIZEOF_REG, offsetof(struct pt_regs, a2)},
 201         {DBG_REG_A3, GDB_SIZEOF_REG, offsetof(struct pt_regs, a3)},
 202         {DBG_REG_A4, GDB_SIZEOF_REG, offsetof(struct pt_regs, a4)},
 203         {DBG_REG_A5, GDB_SIZEOF_REG, offsetof(struct pt_regs, a5)},
 204         {DBG_REG_A6, GDB_SIZEOF_REG, offsetof(struct pt_regs, a6)},
 205         {DBG_REG_A7, GDB_SIZEOF_REG, offsetof(struct pt_regs, a7)},
 206         {DBG_REG_S2, GDB_SIZEOF_REG, offsetof(struct pt_regs, s2)},
 207         {DBG_REG_S3, GDB_SIZEOF_REG, offsetof(struct pt_regs, s3)},
 208         {DBG_REG_S4, GDB_SIZEOF_REG, offsetof(struct pt_regs, s4)},
 209         {DBG_REG_S5, GDB_SIZEOF_REG, offsetof(struct pt_regs, s5)},
 210         {DBG_REG_S6, GDB_SIZEOF_REG, offsetof(struct pt_regs, s6)},
 211         {DBG_REG_S7, GDB_SIZEOF_REG, offsetof(struct pt_regs, s7)},
 212         {DBG_REG_S8, GDB_SIZEOF_REG, offsetof(struct pt_regs, s8)},
 213         {DBG_REG_S9, GDB_SIZEOF_REG, offsetof(struct pt_regs, s9)},
 214         {DBG_REG_S10, GDB_SIZEOF_REG, offsetof(struct pt_regs, s10)},
 215         {DBG_REG_S11, GDB_SIZEOF_REG, offsetof(struct pt_regs, s11)},
 216         {DBG_REG_T3, GDB_SIZEOF_REG, offsetof(struct pt_regs, t3)},
 217         {DBG_REG_T4, GDB_SIZEOF_REG, offsetof(struct pt_regs, t4)},
 218         {DBG_REG_T5, GDB_SIZEOF_REG, offsetof(struct pt_regs, t5)},
 219         {DBG_REG_T6, GDB_SIZEOF_REG, offsetof(struct pt_regs, t6)},
 220         {DBG_REG_EPC, GDB_SIZEOF_REG, offsetof(struct pt_regs, epc)},
 221         {DBG_REG_STATUS, GDB_SIZEOF_REG, offsetof(struct pt_regs, status)},
 222         {DBG_REG_BADADDR, GDB_SIZEOF_REG, offsetof(struct pt_regs, badaddr)},
 223         {DBG_REG_CAUSE, GDB_SIZEOF_REG, offsetof(struct pt_regs, cause)},
 224 };
 225
 226 char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs)
 227 {
 228         if (regno >= DBG_MAX_REG_NUM || regno < 0)
 229                 return NULL;
 230
 231         if (dbg_reg_def[regno].offset != -1)
 232                 memcpy(mem, (void *)regs + dbg_reg_def[regno].offset,
 233                        dbg_reg_def[regno].size);
 234         else
 235                 memset(mem, 0, dbg_reg_def[regno].size);
 236         return dbg_reg_def[regno].name;
 237 }
 238
 239 int dbg_set_reg(int regno, void *mem, struct pt_regs *regs)
 240 {
 241         if (regno >= DBG_MAX_REG_NUM || regno < 0)
 242                 return -EINVAL;
 243
 244         if (dbg_reg_def[regno].offset != -1)
 245                 memcpy((void *)regs + dbg_reg_def[regno].offset, mem,
 246                        dbg_reg_def[regno].size);
 247         return 0;
 248 }
 249
 250 void
 251 sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *task)
 252 {
 253         /* Initialize to zero */
 254         memset((char *)gdb_regs, 0, NUMREGBYTES);
 255
 256         gdb_regs[DBG_REG_SP_OFF] = task->thread.sp;
 257         gdb_regs[DBG_REG_FP_OFF] = task->thread.s[0];
 258         gdb_regs[DBG_REG_S1_OFF] = task->thread.s[1];
 259         gdb_regs[DBG_REG_S2_OFF] = task->thread.s[2];
 260         gdb_regs[DBG_REG_S3_OFF] = task->thread.s[3];
 261         gdb_regs[DBG_REG_S4_OFF] = task->thread.s[4];
 262         gdb_regs[DBG_REG_S5_OFF] = task->thread.s[5];
 263         gdb_regs[DBG_REG_S6_OFF] = task->thread.s[6];
 264         gdb_regs[DBG_REG_S7_OFF] = task->thread.s[7];
 265         gdb_regs[DBG_REG_S8_OFF] = task->thread.s[8];
 266         gdb_regs[DBG_REG_S9_OFF] = task->thread.s[10];
 267         gdb_regs[DBG_REG_S10_OFF] = task->thread.s[11];
 268         gdb_regs[DBG_REG_EPC_OFF] = task->thread.ra;
 269 }
 270
 271 void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long pc)
 272 {
 273         regs->epc = pc;
 274 }
 275
 276 void kgdb_arch_handle_qxfer_pkt(char *remcom_in_buffer,
 277                                 char *remcom_out_buffer)
 278 {
 279         if (!strncmp(remcom_in_buffer, gdb_xfer_read_target,
 280                      sizeof(gdb_xfer_read_target)))
 281                 strcpy(remcom_out_buffer, riscv_gdb_stub_target_desc);
 282         else if (!strncmp(remcom_in_buffer, gdb_xfer_read_cpuxml,
 283                           sizeof(gdb_xfer_read_cpuxml)))
 284                 strcpy(remcom_out_buffer, riscv_gdb_stub_cpuxml);
 285 }
 286
 287 static inline void kgdb_arch_update_addr(struct pt_regs *regs,
 288                                          char *remcom_in_buffer)
 289 {
 290         unsigned long addr;
 291         char *ptr;
 292
 293         ptr = &remcom_in_buffer[1];
 294         if (kgdb_hex2long(&ptr, &addr))
 295                 regs->epc = addr;
 296 }
 297
 298 int kgdb_arch_handle_exception(int vector, int signo, int err_code,
 299                                char *remcom_in_buffer, char *remcom_out_buffer,
 300                                struct pt_regs *regs)
 301 {
 302         int err = 0;
 303
 304         undo_single_step(regs);
 305
 306         switch (remcom_in_buffer[0]) {
 307         case 'c':
 308         case 'D':
 309         case 'k':
 310                 if (remcom_in_buffer[0] == 'c')
 311                         kgdb_arch_update_addr(regs, remcom_in_buffer);
 312                 break;
 313         case 's':
 314                 kgdb_arch_update_addr(regs, remcom_in_buffer);
 315                 err = do_single_step(regs);
 316                 break;
 317         default:
 318                 err = -1;
 319         }
 320         return err;
 321 }
 322
 323 static int kgdb_riscv_kgdbbreak(unsigned long addr)
 324 {
 325         if (stepped_address == addr)
 326                 return KGDB_SW_SINGLE_STEP;
 327         if (atomic_read(&kgdb_setting_breakpoint))
 328                 if (addr == (unsigned long)&kgdb_compiled_break)
 329                         return KGDB_COMPILED_BREAK;
 330
 331         return kgdb_has_hit_break(addr);
 332 }
 333
 334 static int kgdb_riscv_notify(struct notifier_block *self, unsigned long cmd,
 335                              void *ptr)
 336 {
 337         struct die_args *args = (struct die_args *)ptr;
 338         struct pt_regs *regs = args->regs;
 339         unsigned long flags;
 340         int type;
 341
 342         if (user_mode(regs))
 343                 return NOTIFY_DONE;
 344
 345         type = kgdb_riscv_kgdbbreak(regs->epc);
 346         if (type == NOT_KGDB_BREAK && cmd == DIE_TRAP)
 347                 return NOTIFY_DONE;
 348
 349         local_irq_save(flags);
 350
 351         if (kgdb_handle_exception(type == KGDB_SW_SINGLE_STEP ? 0 : 1,
 352                                   args->signr, cmd, regs))
 353                 return NOTIFY_DONE;
 354
 355         if (type == KGDB_COMPILED_BREAK)
 356                 regs->epc += 4;
 357
 358         local_irq_restore(flags);
 359
 360         return NOTIFY_STOP;
 361 }
 362
 363 static struct notifier_block kgdb_notifier = {
 364         .notifier_call = kgdb_riscv_notify,
 365 };
 366
 367 int kgdb_arch_init(void)
 368 {
 369         register_die_notifier(&kgdb_notifier);
 370
 371         return 0;
 372 }
 373
 374 void kgdb_arch_exit(void)
 375 {
 376         unregister_die_notifier(&kgdb_notifier);
 377 }
 378
 379 /*
 380  * Global data
 381  */
 382 #ifdef CONFIG_RISCV_ISA_C
 383 const struct kgdb_arch arch_kgdb_ops = {
 384         .gdb_bpt_instr = {0x02, 0x90},  /* c.ebreak */
 385 };
 386 #else
 387 const struct kgdb_arch arch_kgdb_ops = {
 388         .gdb_bpt_instr = {0x73, 0x00, 0x10, 0x00},      /* ebreak */
 389 };
 390 #endif