arch/sh/kernel/kgdb.c

   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 };