1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * SuperH KGDB support 4 * 5 * Copyright (C) 2008 - 2012 Paul Mundt 6 * 7 * Single stepping taken from the old stub by Henry Bell and Jeremy Siegel. 8 */ 9 #include <linux/kgdb.h> 10 #include <linux/kdebug.h> 11 #include <linux/irq.h> 12 #include <linux/io.h> 13 #include <linux/sched.h> 14 #include <linux/sched/task_stack.h> 15 16 #include <asm/cacheflush.h> 17 #include <asm/traps.h> 18 19 /* Macros for single step instruction identification */ 20 #define OPCODE_BT(op) (((op) & 0xff00) == 0x8900) 21 #define OPCODE_BF(op) (((op) & 0xff00) == 0x8b00) 22 #define OPCODE_BTF_DISP(op) (((op) & 0x80) ? (((op) | 0xffffff80) << 1) : \ 23 (((op) & 0x7f ) << 1)) 24 #define OPCODE_BFS(op) (((op) & 0xff00) == 0x8f00) 25 #define OPCODE_BTS(op) (((op) & 0xff00) == 0x8d00) 26 #define OPCODE_BRA(op) (((op) & 0xf000) == 0xa000) 27 #define OPCODE_BRA_DISP(op) (((op) & 0x800) ? (((op) | 0xfffff800) << 1) : \ 28 (((op) & 0x7ff) << 1)) 29 #define OPCODE_BRAF(op) (((op) & 0xf0ff) == 0x0023) 30 #define OPCODE_BRAF_REG(op) (((op) & 0x0f00) >> 8) 31 #define OPCODE_BSR(op) (((op) & 0xf000) == 0xb000) 32 #define OPCODE_BSR_DISP(op) (((op) & 0x800) ? (((op) | 0xfffff800) << 1) : \ 33 (((op) & 0x7ff) << 1)) 34 #define OPCODE_BSRF(op) (((op) & 0xf0ff) == 0x0003) 35 #define OPCODE_BSRF_REG(op) (((op) >> 8) & 0xf) 36 #define OPCODE_JMP(op) (((op) & 0xf0ff) == 0x402b) 37 #define OPCODE_JMP_REG(op) (((op) >> 8) & 0xf) 38 #define OPCODE_JSR(op) (((op) & 0xf0ff) == 0x400b) 39 #define OPCODE_JSR_REG(op) (((op) >> 8) & 0xf) 40 #define OPCODE_RTS(op) ((op) == 0xb) 41 #define OPCODE_RTE(op) ((op) == 0x2b) 42 43 #define SR_T_BIT_MASK 0x1 44 #define STEP_OPCODE 0xc33d 45 46 /* Calculate the new address for after a step */ 47 static short *get_step_address(struct pt_regs *linux_regs) 48 { 49 insn_size_t op = __raw_readw(linux_regs->pc); 50 long addr; 51 52 /* BT */ 53 if (OPCODE_BT(op)) { 54 if (linux_regs->sr & SR_T_BIT_MASK) 55 addr = linux_regs->pc + 4 + OPCODE_BTF_DISP(op); 56 else 57 addr = linux_regs->pc + 2; 58 } 59 60 /* BTS */ 61 else if (OPCODE_BTS(op)) { 62 if (linux_regs->sr & SR_T_BIT_MASK) 63 addr = linux_regs->pc + 4 + OPCODE_BTF_DISP(op); 64 else 65 addr = linux_regs->pc + 4; /* Not in delay slot */ 66 } 67 68 /* BF */ 69 else if (OPCODE_BF(op)) { 70 if (!(linux_regs->sr & SR_T_BIT_MASK)) 71 addr = linux_regs->pc + 4 + OPCODE_BTF_DISP(op); 72 else 73 addr = linux_regs->pc + 2; 74 } 75 76 /* BFS */ 77 else if (OPCODE_BFS(op)) { 78 if (!(linux_regs->sr & SR_T_BIT_MASK)) 79 addr = linux_regs->pc + 4 + OPCODE_BTF_DISP(op); 80 else 81 addr = linux_regs->pc + 4; /* Not in delay slot */ 82 } 83 84 /* BRA */ 85 else if (OPCODE_BRA(op)) 86 addr = linux_regs->pc + 4 + OPCODE_BRA_DISP(op); 87 88 /* BRAF */ 89 else if (OPCODE_BRAF(op)) 90 addr = linux_regs->pc + 4 91 + linux_regs->regs[OPCODE_BRAF_REG(op)]; 92 93 /* BSR */ 94 else if (OPCODE_BSR(op)) 95 addr = linux_regs->pc + 4 + OPCODE_BSR_DISP(op); 96 97 /* BSRF */ 98 else if (OPCODE_BSRF(op)) 99 addr = linux_regs->pc + 4 100 + linux_regs->regs[OPCODE_BSRF_REG(op)]; 101 102 /* JMP */ 103 else if (OPCODE_JMP(op)) 104 addr = linux_regs->regs[OPCODE_JMP_REG(op)]; 105 106 /* JSR */ 107 else if (OPCODE_JSR(op)) 108 addr = linux_regs->regs[OPCODE_JSR_REG(op)]; 109 110 /* RTS */ 111 else if (OPCODE_RTS(op)) 112 addr = linux_regs->pr; 113 114 /* RTE */ 115 else if (OPCODE_RTE(op)) 116 addr = linux_regs->regs[15]; 117 118 /* Other */ 119 else 120 addr = linux_regs->pc + instruction_size(op); 121 122 flush_icache_range(addr, addr + instruction_size(op)); 123 return (short *)addr; 124 } 125 126 /* 127 * Replace the instruction immediately after the current instruction 128 * (i.e. next in the expected flow of control) with a trap instruction, 129 * so that returning will cause only a single instruction to be executed. 130 * Note that this model is slightly broken for instructions with delay 131 * slots (e.g. B[TF]S, BSR, BRA etc), where both the branch and the 132 * instruction in the delay slot will be executed. 133 */ 134 135 static unsigned long stepped_address; 136 static insn_size_t stepped_opcode; 137 138 static void do_single_step(struct pt_regs *linux_regs) 139 { 140 /* Determine where the target instruction will send us to */ 141 unsigned short *addr = get_step_address(linux_regs); 142 143 stepped_address = (int)addr; 144 145 /* Replace it */ 146 stepped_opcode = __raw_readw((long)addr); 147 *addr = STEP_OPCODE; 148 149 /* Flush and return */ 150 flush_icache_range((long)addr, (long)addr + 151 instruction_size(stepped_opcode)); 152 } 153 154 /* Undo a single step */ 155 static void undo_single_step(struct pt_regs *linux_regs) 156 { 157 /* If we have stepped, put back the old instruction */ 158 /* Use stepped_address in case we stopped elsewhere */ 159 if (stepped_opcode != 0) { 160 __raw_writew(stepped_opcode, stepped_address); 161 flush_icache_range(stepped_address, stepped_address + 2); 162 } 163 164 stepped_opcode = 0; 165 } 166 167 struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] = { 168 { "r0", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[0]) }, 169 { "r1", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[1]) }, 170 { "r2", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[2]) }, 171 { "r3", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[3]) }, 172 { "r4", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[4]) }, 173 { "r5", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[5]) }, 174 { "r6", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[6]) }, 175 { "r7", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[7]) }, 176 { "r8", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[8]) }, 177 { "r9", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[9]) }, 178 { "r10", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[10]) }, 179 { "r11", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[11]) }, 180 { "r12", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[12]) }, 181 { "r13", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[13]) }, 182 { "r14", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[14]) }, 183 { "r15", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[15]) }, 184 { "pc", GDB_SIZEOF_REG, offsetof(struct pt_regs, pc) }, 185 { "pr", GDB_SIZEOF_REG, offsetof(struct pt_regs, pr) }, 186 { "sr", GDB_SIZEOF_REG, offsetof(struct pt_regs, sr) }, 187 { "gbr", GDB_SIZEOF_REG, offsetof(struct pt_regs, gbr) }, 188 { "mach", GDB_SIZEOF_REG, offsetof(struct pt_regs, mach) }, 189 { "macl", GDB_SIZEOF_REG, offsetof(struct pt_regs, macl) }, 190 { "vbr", GDB_SIZEOF_REG, -1 }, 191 }; 192 193 int dbg_set_reg(int regno, void *mem, struct pt_regs *regs) 194 { 195 if (regno < 0 || regno >= DBG_MAX_REG_NUM) 196 return -EINVAL; 197 198 if (dbg_reg_def[regno].offset != -1) 199 memcpy((void *)regs + dbg_reg_def[regno].offset, mem, 200 dbg_reg_def[regno].size); 201 202 return 0; 203 } 204 205 char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs) 206 { 207 if (regno >= DBG_MAX_REG_NUM || regno < 0) 208 return NULL; 209 210 if (dbg_reg_def[regno].size != -1) 211 memcpy(mem, (void *)regs + dbg_reg_def[regno].offset, 212 dbg_reg_def[regno].size); 213 214 switch (regno) { 215 case GDB_VBR: 216 __asm__ __volatile__ ("stc vbr, %0" : "=r" (mem)); 217 break; 218 } 219 220 return dbg_reg_def[regno].name; 221 } 222 223 void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p) 224 { 225 struct pt_regs *thread_regs = task_pt_regs(p); 226 int reg; 227 228 /* Initialize to zero */ 229 for (reg = 0; reg < DBG_MAX_REG_NUM; reg++) 230 gdb_regs[reg] = 0; 231 232 /* 233 * Copy out GP regs 8 to 14. 234 * 235 * switch_to() relies on SR.RB toggling, so regs 0->7 are banked 236 * and need privileged instructions to get to. The r15 value we 237 * fetch from the thread info directly. 238 */ 239 for (reg = GDB_R8; reg < GDB_R15; reg++) 240 gdb_regs[reg] = thread_regs->regs[reg]; 241 242 gdb_regs[GDB_R15] = p->thread.sp; 243 gdb_regs[GDB_PC] = p->thread.pc; 244 245 /* 246 * Additional registers we have context for 247 */ 248 gdb_regs[GDB_PR] = thread_regs->pr; 249 gdb_regs[GDB_GBR] = thread_regs->gbr; 250 } 251 252 int kgdb_arch_handle_exception(int e_vector, int signo, int err_code, 253 char *remcomInBuffer, char *remcomOutBuffer, 254 struct pt_regs *linux_regs) 255 { 256 unsigned long addr; 257 char *ptr; 258 259 /* Undo any stepping we may have done */ 260 undo_single_step(linux_regs); 261 262 switch (remcomInBuffer[0]) { 263 case 'c': 264 case 's': 265 /* try to read optional parameter, pc unchanged if no parm */ 266 ptr = &remcomInBuffer[1]; 267 if (kgdb_hex2long(&ptr, &addr)) 268 linux_regs->pc = addr; 269 fallthrough; 270 case 'D': 271 case 'k': 272 atomic_set(&kgdb_cpu_doing_single_step, -1); 273 274 if (remcomInBuffer[0] == 's') { 275 do_single_step(linux_regs); 276 kgdb_single_step = 1; 277 278 atomic_set(&kgdb_cpu_doing_single_step, 279 raw_smp_processor_id()); 280 } 281 282 return 0; 283 } 284 285 /* this means that we do not want to exit from the handler: */ 286 return -1; 287 } 288 289 unsigned long kgdb_arch_pc(int exception, struct pt_regs *regs) 290 { 291 if (exception == 60) 292 return instruction_pointer(regs) - 2; 293 return instruction_pointer(regs); 294 } 295 296 void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long ip) 297 { 298 regs->pc = ip; 299 } 300 301 /* 302 * The primary entry points for the kgdb debug trap table entries. 303 */ 304 BUILD_TRAP_HANDLER(singlestep) 305 { 306 unsigned long flags; 307 TRAP_HANDLER_DECL; 308 309 local_irq_save(flags); 310 regs->pc -= instruction_size(__raw_readw(regs->pc - 4)); 311 kgdb_handle_exception(0, SIGTRAP, 0, regs); 312 local_irq_restore(flags); 313 } 314 315 static int __kgdb_notify(struct die_args *args, unsigned long cmd) 316 { 317 int ret; 318 319 switch (cmd) { 320 case DIE_BREAKPOINT: 321 /* 322 * This means a user thread is single stepping 323 * a system call which should be ignored 324 */ 325 if (test_thread_flag(TIF_SINGLESTEP)) 326 return NOTIFY_DONE; 327 328 ret = kgdb_handle_exception(args->trapnr & 0xff, args->signr, 329 args->err, args->regs); 330 if (ret) 331 return NOTIFY_DONE; 332 333 break; 334 } 335 336 return NOTIFY_STOP; 337 } 338 339 static int 340 kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr) 341 { 342 unsigned long flags; 343 int ret; 344 345 local_irq_save(flags); 346 ret = __kgdb_notify(ptr, cmd); 347 local_irq_restore(flags); 348 349 return ret; 350 } 351 352 static struct notifier_block kgdb_notifier = { 353 .notifier_call = kgdb_notify, 354 355 /* 356 * Lowest-prio notifier priority, we want to be notified last: 357 */ 358 .priority = -INT_MAX, 359 }; 360 361 int kgdb_arch_init(void) 362 { 363 return register_die_notifier(&kgdb_notifier); 364 } 365 366 void kgdb_arch_exit(void) 367 { 368 unregister_die_notifier(&kgdb_notifier); 369 } 370 371 const struct kgdb_arch arch_kgdb_ops = { 372 /* Breakpoint instruction: trapa #0x3c */ 373 #ifdef CONFIG_CPU_LITTLE_ENDIAN 374 .gdb_bpt_instr = { 0x3c, 0xc3 }, 375 #else 376 .gdb_bpt_instr = { 0xc3, 0x3c }, 377 #endif 378 }; 379