arch/sh/kernel/kgdb.c

   1 /*
   2  * SuperH KGDB support
   3  *
   4  * Copyright (C) 2008 - 2012  Paul Mundt
   5  *
   6  * Single stepping taken from the old stub by Henry Bell and Jeremy Siegel.
   7  *
   8  * This file is subject to the terms and conditions of the GNU General Public
   9  * License.  See the file "COPYING" in the main directory of this archive
  10  * for more details.
  11  */
  12 #include <linux/kgdb.h>
  13 #include <linux/kdebug.h>
  14 #include <linux/irq.h>
  15 #include <linux/io.h>
  16 #include <linux/sched.h>
  17 #include <asm/cacheflush.h>
  18 #include <asm/traps.h>
  19
  20 /* Macros for single step instruction identification */
  21 #define OPCODE_BT(op)           (((op) & 0xff00) == 0x8900)
  22 #define OPCODE_BF(op)           (((op) & 0xff00) == 0x8b00)
  23 #define OPCODE_BTF_DISP(op)     (((op) & 0x80) ? (((op) | 0xffffff80) << 1) : \
  24                                  (((op) & 0x7f ) << 1))
  25 #define OPCODE_BFS(op)          (((op) & 0xff00) == 0x8f00)
  26 #define OPCODE_BTS(op)          (((op) & 0xff00) == 0x8d00)
  27 #define OPCODE_BRA(op)          (((op) & 0xf000) == 0xa000)
  28 #define OPCODE_BRA_DISP(op)     (((op) & 0x800) ? (((op) | 0xfffff800) << 1) : \
  29                                  (((op) & 0x7ff) << 1))
  30 #define OPCODE_BRAF(op)         (((op) & 0xf0ff) == 0x0023)
  31 #define OPCODE_BRAF_REG(op)     (((op) & 0x0f00) >> 8)
  32 #define OPCODE_BSR(op)          (((op) & 0xf000) == 0xb000)
  33 #define OPCODE_BSR_DISP(op)     (((op) & 0x800) ? (((op) | 0xfffff800) << 1) : \
  34                                  (((op) & 0x7ff) << 1))
  35 #define OPCODE_BSRF(op)         (((op) & 0xf0ff) == 0x0003)
  36 #define OPCODE_BSRF_REG(op)     (((op) >> 8) & 0xf)
  37 #define OPCODE_JMP(op)          (((op) & 0xf0ff) == 0x402b)
  38 #define OPCODE_JMP_REG(op)      (((op) >> 8) & 0xf)
  39 #define OPCODE_JSR(op)          (((op) & 0xf0ff) == 0x400b)
  40 #define OPCODE_JSR_REG(op)      (((op) >> 8) & 0xf)
  41 #define OPCODE_RTS(op)          ((op) == 0xb)
  42 #define OPCODE_RTE(op)          ((op) == 0x2b)
  43
  44 #define SR_T_BIT_MASK           0x1
  45 #define STEP_OPCODE             0xc33d
  46
  47 /* Calculate the new address for after a step */
  48 static short *get_step_address(struct pt_regs *linux_regs)
  49 {
  50         insn_size_t op = __raw_readw(linux_regs->pc);
  51         long addr;
  52
  53         /* BT */
  54         if (OPCODE_BT(op)) {
  55                 if (linux_regs->sr & SR_T_BIT_MASK)
  56                         addr = linux_regs->pc + 4 + OPCODE_BTF_DISP(op);
  57                 else
  58                         addr = linux_regs->pc + 2;
  59         }
  60
  61         /* BTS */
  62         else if (OPCODE_BTS(op)) {
  63                 if (linux_regs->sr & SR_T_BIT_MASK)
  64                         addr = linux_regs->pc + 4 + OPCODE_BTF_DISP(op);
  65                 else
  66                         addr = linux_regs->pc + 4;      /* Not in delay slot */
  67         }
  68
  69         /* BF */
  70         else if (OPCODE_BF(op)) {
  71                 if (!(linux_regs->sr & SR_T_BIT_MASK))
  72                         addr = linux_regs->pc + 4 + OPCODE_BTF_DISP(op);
  73                 else
  74                         addr = linux_regs->pc + 2;
  75         }
  76
  77         /* BFS */
  78         else if (OPCODE_BFS(op)) {
  79                 if (!(linux_regs->sr & SR_T_BIT_MASK))
  80                         addr = linux_regs->pc + 4 + OPCODE_BTF_DISP(op);
  81                 else
  82                         addr = linux_regs->pc + 4;      /* Not in delay slot */
  83         }
  84
  85         /* BRA */
  86         else if (OPCODE_BRA(op))
  87                 addr = linux_regs->pc + 4 + OPCODE_BRA_DISP(op);
  88
  89         /* BRAF */
  90         else if (OPCODE_BRAF(op))
  91                 addr = linux_regs->pc + 4
  92                     + linux_regs->regs[OPCODE_BRAF_REG(op)];
  93
  94         /* BSR */
  95         else if (OPCODE_BSR(op))
  96                 addr = linux_regs->pc + 4 + OPCODE_BSR_DISP(op);
  97
  98         /* BSRF */
  99         else if (OPCODE_BSRF(op))
 100                 addr = linux_regs->pc + 4
 101                     + linux_regs->regs[OPCODE_BSRF_REG(op)];
 102
 103         /* JMP */
 104         else if (OPCODE_JMP(op))
 105                 addr = linux_regs->regs[OPCODE_JMP_REG(op)];
 106
 107         /* JSR */
 108         else if (OPCODE_JSR(op))
 109                 addr = linux_regs->regs[OPCODE_JSR_REG(op)];
 110
 111         /* RTS */
 112         else if (OPCODE_RTS(op))
 113                 addr = linux_regs->pr;
 114
 115         /* RTE */
 116         else if (OPCODE_RTE(op))
 117                 addr = linux_regs->regs[15];
 118
 119         /* Other */
 120         else
 121                 addr = linux_regs->pc + instruction_size(op);
 122
 123         flush_icache_range(addr, addr + instruction_size(op));
 124         return (short *)addr;
 125 }
 126
 127 /*
 128  * Replace the instruction immediately after the current instruction
 129  * (i.e. next in the expected flow of control) with a trap instruction,
 130  * so that returning will cause only a single instruction to be executed.
 131  * Note that this model is slightly broken for instructions with delay
 132  * slots (e.g. B[TF]S, BSR, BRA etc), where both the branch and the
 133  * instruction in the delay slot will be executed.
 134  */
 135
 136 static unsigned long stepped_address;
 137 static insn_size_t stepped_opcode;
 138
 139 static void do_single_step(struct pt_regs *linux_regs)
 140 {
 141         /* Determine where the target instruction will send us to */
 142         unsigned short *addr = get_step_address(linux_regs);
 143
 144         stepped_address = (int)addr;
 145
 146         /* Replace it */
 147         stepped_opcode = __raw_readw((long)addr);
 148         *addr = STEP_OPCODE;
 149
 150         /* Flush and return */
 151         flush_icache_range((long)addr, (long)addr +
 152                            instruction_size(stepped_opcode));
 153 }
 154
 155 /* Undo a single step */
 156 static void undo_single_step(struct pt_regs *linux_regs)
 157 {
 158         /* If we have stepped, put back the old instruction */
 159         /* Use stepped_address in case we stopped elsewhere */
 160         if (stepped_opcode != 0) {
 161                 __raw_writew(stepped_opcode, stepped_address);
 162                 flush_icache_range(stepped_address, stepped_address + 2);
 163         }
 164
 165         stepped_opcode = 0;
 166 }
 167
 168 struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] = {
 169         { "r0",         GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[0]) },
 170         { "r1",         GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[1]) },
 171         { "r2",         GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[2]) },
 172         { "r3",         GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[3]) },
 173         { "r4",         GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[4]) },
 174         { "r5",         GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[5]) },
 175         { "r6",         GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[6]) },
 176         { "r7",         GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[7]) },
 177         { "r8",         GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[8]) },
 178         { "r9",         GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[9]) },
 179         { "r10",        GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[10]) },
 180         { "r11",        GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[11]) },
 181         { "r12",        GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[12]) },
 182         { "r13",        GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[13]) },
 183         { "r14",        GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[14]) },
 184         { "r15",        GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[15]) },
 185         { "pc",         GDB_SIZEOF_REG, offsetof(struct pt_regs, pc) },
 186         { "pr",         GDB_SIZEOF_REG, offsetof(struct pt_regs, pr) },
 187         { "sr",         GDB_SIZEOF_REG, offsetof(struct pt_regs, sr) },
 188         { "gbr",        GDB_SIZEOF_REG, offsetof(struct pt_regs, gbr) },
 189         { "mach",       GDB_SIZEOF_REG, offsetof(struct pt_regs, mach) },
 190         { "macl",       GDB_SIZEOF_REG, offsetof(struct pt_regs, macl) },
 191         { "vbr",        GDB_SIZEOF_REG, -1 },
 192 };
 193
 194 int dbg_set_reg(int regno, void *mem, struct pt_regs *regs)
 195 {
 196         if (regno < 0 || regno >= DBG_MAX_REG_NUM)
 197                 return -EINVAL;
 198
 199         if (dbg_reg_def[regno].offset != -1)
 200                 memcpy((void *)regs + dbg_reg_def[regno].offset, mem,
 201                        dbg_reg_def[regno].size);
 202
 203         return 0;
 204 }
 205
 206 char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs)
 207 {
 208         if (regno >= DBG_MAX_REG_NUM || regno < 0)
 209                 return NULL;
 210
 211         if (dbg_reg_def[regno].size != -1)
 212                 memcpy(mem, (void *)regs + dbg_reg_def[regno].offset,
 213                        dbg_reg_def[regno].size);
 214
 215         switch (regno) {
 216         case GDB_VBR:
 217                 __asm__ __volatile__ ("stc vbr, %0" : "=r" (mem));
 218                 break;
 219         }
 220
 221         return dbg_reg_def[regno].name;
 222 }
 223
 224 void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
 225 {
 226         struct pt_regs *thread_regs = task_pt_regs(p);
 227         int reg;
 228
 229         /* Initialize to zero */
 230         for (reg = 0; reg < DBG_MAX_REG_NUM; reg++)
 231                 gdb_regs[reg] = 0;
 232
 233         /*
 234          * Copy out GP regs 8 to 14.
 235          *
 236          * switch_to() relies on SR.RB toggling, so regs 0->7 are banked
 237          * and need privileged instructions to get to. The r15 value we
 238          * fetch from the thread info directly.
 239          */
 240         for (reg = GDB_R8; reg < GDB_R15; reg++)
 241                 gdb_regs[reg] = thread_regs->regs[reg];
 242
 243         gdb_regs[GDB_R15] = p->thread.sp;
 244         gdb_regs[GDB_PC] = p->thread.pc;
 245
 246         /*
 247          * Additional registers we have context for
 248          */
 249         gdb_regs[GDB_PR] = thread_regs->pr;
 250         gdb_regs[GDB_GBR] = thread_regs->gbr;
 251 }
 252
 253 int kgdb_arch_handle_exception(int e_vector, int signo, int err_code,
 254                                char *remcomInBuffer, char *remcomOutBuffer,
 255                                struct pt_regs *linux_regs)
 256 {
 257         unsigned long addr;
 258         char *ptr;
 259
 260         /* Undo any stepping we may have done */
 261         undo_single_step(linux_regs);
 262
 263         switch (remcomInBuffer[0]) {
 264         case 'c':
 265         case 's':
 266                 /* try to read optional parameter, pc unchanged if no parm */
 267                 ptr = &remcomInBuffer[1];
 268                 if (kgdb_hex2long(&ptr, &addr))
 269                         linux_regs->pc = addr;
 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 void kgdb_call_nmi_hook(void *ignored)
 316 {
 317         kgdb_nmicallback(raw_smp_processor_id(), get_irq_regs());
 318 }
 319
 320 void kgdb_roundup_cpus(unsigned long flags)
 321 {
 322         local_irq_enable();
 323         smp_call_function(kgdb_call_nmi_hook, NULL, 0);
 324         local_irq_disable();
 325 }
 326
 327 static int __kgdb_notify(struct die_args *args, unsigned long cmd)
 328 {
 329         int ret;
 330
 331         switch (cmd) {
 332         case DIE_BREAKPOINT:
 333                 /*
 334                  * This means a user thread is single stepping
 335                  * a system call which should be ignored
 336                  */
 337                 if (test_thread_flag(TIF_SINGLESTEP))
 338                         return NOTIFY_DONE;
 339
 340                 ret = kgdb_handle_exception(args->trapnr & 0xff, args->signr,
 341                                             args->err, args->regs);
 342                 if (ret)
 343                         return NOTIFY_DONE;
 344
 345                 break;
 346         }
 347
 348         return NOTIFY_STOP;
 349 }
 350
 351 static int
 352 kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
 353 {
 354         unsigned long flags;
 355         int ret;
 356
 357         local_irq_save(flags);
 358         ret = __kgdb_notify(ptr, cmd);
 359         local_irq_restore(flags);
 360
 361         return ret;
 362 }
 363
 364 static struct notifier_block kgdb_notifier = {
 365         .notifier_call  = kgdb_notify,
 366
 367         /*
 368          * Lowest-prio notifier priority, we want to be notified last:
 369          */
 370         .priority       = -INT_MAX,
 371 };
 372
 373 int kgdb_arch_init(void)
 374 {
 375         return register_die_notifier(&kgdb_notifier);
 376 }
 377
 378 void kgdb_arch_exit(void)
 379 {
 380         unregister_die_notifier(&kgdb_notifier);
 381 }
 382
 383 struct kgdb_arch arch_kgdb_ops = {
 384         /* Breakpoint instruction: trapa #0x3c */
 385 #ifdef CONFIG_CPU_LITTLE_ENDIAN
 386         .gdb_bpt_instr          = { 0x3c, 0xc3 },
 387 #else
 388         .gdb_bpt_instr          = { 0xc3, 0x3c },
 389 #endif
 390 };