arch/sh/kernel/kgdb.c

   1 /*
   2  * SuperH KGDB support
   3  *
   4  * Copyright (C) 2008  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 char in_nmi = 0;        /* Set during NMI to prevent re-entry */
  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         opcode_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 opcode_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 void pt_regs_to_gdb_regs(unsigned long *gdb_regs, struct pt_regs *regs)
 169 {
 170         int i;
 171
 172         for (i = 0; i < 16; i++)
 173                 gdb_regs[GDB_R0 + i] = regs->regs[i];
 174
 175         gdb_regs[GDB_PC] = regs->pc;
 176         gdb_regs[GDB_PR] = regs->pr;
 177         gdb_regs[GDB_SR] = regs->sr;
 178         gdb_regs[GDB_GBR] = regs->gbr;
 179         gdb_regs[GDB_MACH] = regs->mach;
 180         gdb_regs[GDB_MACL] = regs->macl;
 181
 182         __asm__ __volatile__ ("stc vbr, %0" : "=r" (gdb_regs[GDB_VBR]));
 183 }
 184
 185 void gdb_regs_to_pt_regs(unsigned long *gdb_regs, struct pt_regs *regs)
 186 {
 187         int i;
 188
 189         for (i = 0; i < 16; i++)
 190                 regs->regs[GDB_R0 + i] = gdb_regs[GDB_R0 + i];
 191
 192         regs->pc = gdb_regs[GDB_PC];
 193         regs->pr = gdb_regs[GDB_PR];
 194         regs->sr = gdb_regs[GDB_SR];
 195         regs->gbr = gdb_regs[GDB_GBR];
 196         regs->mach = gdb_regs[GDB_MACH];
 197         regs->macl = gdb_regs[GDB_MACL];
 198
 199         __asm__ __volatile__ ("ldc %0, vbr" : : "r" (gdb_regs[GDB_VBR]));
 200 }
 201
 202 void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
 203 {
 204         gdb_regs[GDB_R15] = p->thread.sp;
 205         gdb_regs[GDB_PC] = p->thread.pc;
 206 }
 207
 208 int kgdb_arch_handle_exception(int e_vector, int signo, int err_code,
 209                                char *remcomInBuffer, char *remcomOutBuffer,
 210                                struct pt_regs *linux_regs)
 211 {
 212         unsigned long addr;
 213         char *ptr;
 214
 215         /* Undo any stepping we may have done */
 216         undo_single_step(linux_regs);
 217
 218         switch (remcomInBuffer[0]) {
 219         case 'c':
 220         case 's':
 221                 /* try to read optional parameter, pc unchanged if no parm */
 222                 ptr = &remcomInBuffer[1];
 223                 if (kgdb_hex2long(&ptr, &addr))
 224                         linux_regs->pc = addr;
 225         case 'D':
 226         case 'k':
 227                 atomic_set(&kgdb_cpu_doing_single_step, -1);
 228
 229                 if (remcomInBuffer[0] == 's') {
 230                         do_single_step(linux_regs);
 231                         kgdb_single_step = 1;
 232
 233                         atomic_set(&kgdb_cpu_doing_single_step,
 234                                    raw_smp_processor_id());
 235                 }
 236
 237                 return 0;
 238         }
 239
 240         /* this means that we do not want to exit from the handler: */
 241         return -1;
 242 }
 243
 244 /*
 245  * The primary entry points for the kgdb debug trap table entries.
 246  */
 247 BUILD_TRAP_HANDLER(singlestep)
 248 {
 249         unsigned long flags;
 250         TRAP_HANDLER_DECL;
 251
 252         local_irq_save(flags);
 253         regs->pc -= instruction_size(__raw_readw(regs->pc - 4));
 254         kgdb_handle_exception(vec >> 2, SIGTRAP, 0, regs);
 255         local_irq_restore(flags);
 256 }
 257
 258
 259 BUILD_TRAP_HANDLER(breakpoint)
 260 {
 261         unsigned long flags;
 262         TRAP_HANDLER_DECL;
 263
 264         local_irq_save(flags);
 265         kgdb_handle_exception(vec >> 2, SIGTRAP, 0, regs);
 266         local_irq_restore(flags);
 267 }
 268
 269 int kgdb_arch_init(void)
 270 {
 271         return 0;
 272 }
 273
 274 void kgdb_arch_exit(void)
 275 {
 276 }
 277
 278 struct kgdb_arch arch_kgdb_ops = {
 279         /* Breakpoint instruction: trapa #0x3c */
 280 #ifdef CONFIG_CPU_LITTLE_ENDIAN
 281         .gdb_bpt_instr          = { 0x3c, 0xc3 },
 282 #else
 283         .gdb_bpt_instr          = { 0xc3, 0x3c },
 284 #endif
 285 };