arch/sh/kernel/kgdb.c

   1 /*
   2  * SuperH KGDB support
   3  *
   4  * Copyright (C) 2008 - 2009  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 <asm/cacheflush.h>
  17
  18 /* Macros for single step instruction identification */
  19 #define OPCODE_BT(op)           (((op) & 0xff00) == 0x8900)
  20 #define OPCODE_BF(op)           (((op) & 0xff00) == 0x8b00)
  21 #define OPCODE_BTF_DISP(op)     (((op) & 0x80) ? (((op) | 0xffffff80) << 1) : \
  22                                  (((op) & 0x7f ) << 1))
  23 #define OPCODE_BFS(op)          (((op) & 0xff00) == 0x8f00)
  24 #define OPCODE_BTS(op)          (((op) & 0xff00) == 0x8d00)
  25 #define OPCODE_BRA(op)          (((op) & 0xf000) == 0xa000)
  26 #define OPCODE_BRA_DISP(op)     (((op) & 0x800) ? (((op) | 0xfffff800) << 1) : \
  27                                  (((op) & 0x7ff) << 1))
  28 #define OPCODE_BRAF(op)         (((op) & 0xf0ff) == 0x0023)
  29 #define OPCODE_BRAF_REG(op)     (((op) & 0x0f00) >> 8)
  30 #define OPCODE_BSR(op)          (((op) & 0xf000) == 0xb000)
  31 #define OPCODE_BSR_DISP(op)     (((op) & 0x800) ? (((op) | 0xfffff800) << 1) : \
  32                                  (((op) & 0x7ff) << 1))
  33 #define OPCODE_BSRF(op)         (((op) & 0xf0ff) == 0x0003)
  34 #define OPCODE_BSRF_REG(op)     (((op) >> 8) & 0xf)
  35 #define OPCODE_JMP(op)          (((op) & 0xf0ff) == 0x402b)
  36 #define OPCODE_JMP_REG(op)      (((op) >> 8) & 0xf)
  37 #define OPCODE_JSR(op)          (((op) & 0xf0ff) == 0x400b)
  38 #define OPCODE_JSR_REG(op)      (((op) >> 8) & 0xf)
  39 #define OPCODE_RTS(op)          ((op) == 0xb)
  40 #define OPCODE_RTE(op)          ((op) == 0x2b)
  41
  42 #define SR_T_BIT_MASK           0x1
  43 #define STEP_OPCODE             0xc33d
  44
  45 /* Calculate the new address for after a step */
  46 static short *get_step_address(struct pt_regs *linux_regs)
  47 {
  48         insn_size_t op = __raw_readw(linux_regs->pc);
  49         long addr;
  50
  51         /* BT */
  52         if (OPCODE_BT(op)) {
  53                 if (linux_regs->sr & SR_T_BIT_MASK)
  54                         addr = linux_regs->pc + 4 + OPCODE_BTF_DISP(op);
  55                 else
  56                         addr = linux_regs->pc + 2;
  57         }
  58
  59         /* BTS */
  60         else if (OPCODE_BTS(op)) {
  61                 if (linux_regs->sr & SR_T_BIT_MASK)
  62                         addr = linux_regs->pc + 4 + OPCODE_BTF_DISP(op);
  63                 else
  64                         addr = linux_regs->pc + 4;      /* Not in delay slot */
  65         }
  66
  67         /* BF */
  68         else if (OPCODE_BF(op)) {
  69                 if (!(linux_regs->sr & SR_T_BIT_MASK))
  70                         addr = linux_regs->pc + 4 + OPCODE_BTF_DISP(op);
  71                 else
  72                         addr = linux_regs->pc + 2;
  73         }
  74
  75         /* BFS */
  76         else if (OPCODE_BFS(op)) {
  77                 if (!(linux_regs->sr & SR_T_BIT_MASK))
  78                         addr = linux_regs->pc + 4 + OPCODE_BTF_DISP(op);
  79                 else
  80                         addr = linux_regs->pc + 4;      /* Not in delay slot */
  81         }
  82
  83         /* BRA */
  84         else if (OPCODE_BRA(op))
  85                 addr = linux_regs->pc + 4 + OPCODE_BRA_DISP(op);
  86
  87         /* BRAF */
  88         else if (OPCODE_BRAF(op))
  89                 addr = linux_regs->pc + 4
  90                     + linux_regs->regs[OPCODE_BRAF_REG(op)];
  91
  92         /* BSR */
  93         else if (OPCODE_BSR(op))
  94                 addr = linux_regs->pc + 4 + OPCODE_BSR_DISP(op);
  95
  96         /* BSRF */
  97         else if (OPCODE_BSRF(op))
  98                 addr = linux_regs->pc + 4
  99                     + linux_regs->regs[OPCODE_BSRF_REG(op)];
 100
 101         /* JMP */
 102         else if (OPCODE_JMP(op))
 103                 addr = linux_regs->regs[OPCODE_JMP_REG(op)];
 104
 105         /* JSR */
 106         else if (OPCODE_JSR(op))
 107                 addr = linux_regs->regs[OPCODE_JSR_REG(op)];
 108
 109         /* RTS */
 110         else if (OPCODE_RTS(op))
 111                 addr = linux_regs->pr;
 112
 113         /* RTE */
 114         else if (OPCODE_RTE(op))
 115                 addr = linux_regs->regs[15];
 116
 117         /* Other */
 118         else
 119                 addr = linux_regs->pc + instruction_size(op);
 120
 121         flush_icache_range(addr, addr + instruction_size(op));
 122         return (short *)addr;
 123 }
 124
 125 /*
 126  * Replace the instruction immediately after the current instruction
 127  * (i.e. next in the expected flow of control) with a trap instruction,
 128  * so that returning will cause only a single instruction to be executed.
 129  * Note that this model is slightly broken for instructions with delay
 130  * slots (e.g. B[TF]S, BSR, BRA etc), where both the branch and the
 131  * instruction in the delay slot will be executed.
 132  */
 133
 134 static unsigned long stepped_address;
 135 static insn_size_t stepped_opcode;
 136
 137 static void do_single_step(struct pt_regs *linux_regs)
 138 {
 139         /* Determine where the target instruction will send us to */
 140         unsigned short *addr = get_step_address(linux_regs);
 141
 142         stepped_address = (int)addr;
 143
 144         /* Replace it */
 145         stepped_opcode = __raw_readw((long)addr);
 146         *addr = STEP_OPCODE;
 147
 148         /* Flush and return */
 149         flush_icache_range((long)addr, (long)addr +
 150                            instruction_size(stepped_opcode));
 151 }
 152
 153 /* Undo a single step */
 154 static void undo_single_step(struct pt_regs *linux_regs)
 155 {
 156         /* If we have stepped, put back the old instruction */
 157         /* Use stepped_address in case we stopped elsewhere */
 158         if (stepped_opcode != 0) {
 159                 __raw_writew(stepped_opcode, stepped_address);
 160                 flush_icache_range(stepped_address, stepped_address + 2);
 161         }
 162
 163         stepped_opcode = 0;
 164 }
 165
 166 void pt_regs_to_gdb_regs(unsigned long *gdb_regs, struct pt_regs *regs)
 167 {
 168         int i;
 169
 170         for (i = 0; i < 16; i++)
 171                 gdb_regs[GDB_R0 + i] = regs->regs[i];
 172
 173         gdb_regs[GDB_PC] = regs->pc;
 174         gdb_regs[GDB_PR] = regs->pr;
 175         gdb_regs[GDB_SR] = regs->sr;
 176         gdb_regs[GDB_GBR] = regs->gbr;
 177         gdb_regs[GDB_MACH] = regs->mach;
 178         gdb_regs[GDB_MACL] = regs->macl;
 179
 180         __asm__ __volatile__ ("stc vbr, %0" : "=r" (gdb_regs[GDB_VBR]));
 181 }
 182
 183 void gdb_regs_to_pt_regs(unsigned long *gdb_regs, struct pt_regs *regs)
 184 {
 185         int i;
 186
 187         for (i = 0; i < 16; i++)
 188                 regs->regs[GDB_R0 + i] = gdb_regs[GDB_R0 + i];
 189
 190         regs->pc = gdb_regs[GDB_PC];
 191         regs->pr = gdb_regs[GDB_PR];
 192         regs->sr = gdb_regs[GDB_SR];
 193         regs->gbr = gdb_regs[GDB_GBR];
 194         regs->mach = gdb_regs[GDB_MACH];
 195         regs->macl = gdb_regs[GDB_MACL];
 196 }
 197
 198 void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
 199 {
 200         gdb_regs[GDB_R15] = p->thread.sp;
 201         gdb_regs[GDB_PC] = p->thread.pc;
 202 }
 203
 204 int kgdb_arch_handle_exception(int e_vector, int signo, int err_code,
 205                                char *remcomInBuffer, char *remcomOutBuffer,
 206                                struct pt_regs *linux_regs)
 207 {
 208         unsigned long addr;
 209         char *ptr;
 210
 211         /* Undo any stepping we may have done */
 212         undo_single_step(linux_regs);
 213
 214         switch (remcomInBuffer[0]) {
 215         case 'c':
 216         case 's':
 217                 /* try to read optional parameter, pc unchanged if no parm */
 218                 ptr = &remcomInBuffer[1];
 219                 if (kgdb_hex2long(&ptr, &addr))
 220                         linux_regs->pc = addr;
 221         case 'D':
 222         case 'k':
 223                 atomic_set(&kgdb_cpu_doing_single_step, -1);
 224
 225                 if (remcomInBuffer[0] == 's') {
 226                         do_single_step(linux_regs);
 227                         kgdb_single_step = 1;
 228
 229                         atomic_set(&kgdb_cpu_doing_single_step,
 230                                    raw_smp_processor_id());
 231                 }
 232
 233                 return 0;
 234         }
 235
 236         /* this means that we do not want to exit from the handler: */
 237         return -1;
 238 }
 239
 240 unsigned long kgdb_arch_pc(int exception, struct pt_regs *regs)
 241 {
 242         if (exception == 60)
 243                 return instruction_pointer(regs) - 2;
 244         return instruction_pointer(regs);
 245 }
 246
 247 void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long ip)
 248 {
 249         regs->pc = ip;
 250 }
 251
 252 /*
 253  * The primary entry points for the kgdb debug trap table entries.
 254  */
 255 BUILD_TRAP_HANDLER(singlestep)
 256 {
 257         unsigned long flags;
 258         TRAP_HANDLER_DECL;
 259
 260         local_irq_save(flags);
 261         regs->pc -= instruction_size(__raw_readw(regs->pc - 4));
 262         kgdb_handle_exception(0, SIGTRAP, 0, regs);
 263         local_irq_restore(flags);
 264 }
 265
 266 static int __kgdb_notify(struct die_args *args, unsigned long cmd)
 267 {
 268         int ret;
 269
 270         switch (cmd) {
 271         case DIE_BREAKPOINT:
 272                 /*
 273                  * This means a user thread is single stepping
 274                  * a system call which should be ignored
 275                  */
 276                 if (test_thread_flag(TIF_SINGLESTEP))
 277                         return NOTIFY_DONE;
 278
 279                 ret = kgdb_handle_exception(args->trapnr & 0xff, args->signr,
 280                                             args->err, args->regs);
 281                 if (ret)
 282                         return NOTIFY_DONE;
 283
 284                 break;
 285         }
 286
 287         return NOTIFY_STOP;
 288 }
 289
 290 static int
 291 kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
 292 {
 293         unsigned long flags;
 294         int ret;
 295
 296         local_irq_save(flags);
 297         ret = __kgdb_notify(ptr, cmd);
 298         local_irq_restore(flags);
 299
 300         return ret;
 301 }
 302
 303 static struct notifier_block kgdb_notifier = {
 304         .notifier_call  = kgdb_notify,
 305
 306         /*
 307          * Lowest-prio notifier priority, we want to be notified last:
 308          */
 309         .priority       = -INT_MAX,
 310 };
 311
 312 int kgdb_arch_init(void)
 313 {
 314         return register_die_notifier(&kgdb_notifier);
 315 }
 316
 317 void kgdb_arch_exit(void)
 318 {
 319         unregister_die_notifier(&kgdb_notifier);
 320 }
 321
 322 struct kgdb_arch arch_kgdb_ops = {
 323         /* Breakpoint instruction: trapa #0x3c */
 324 #ifdef CONFIG_CPU_LITTLE_ENDIAN
 325         .gdb_bpt_instr          = { 0x3c, 0xc3 },
 326 #else
 327         .gdb_bpt_instr          = { 0xc3, 0x3c },
 328 #endif
 329 };