gdb/tm-68k.h

   1 /* Parameters for execution on a 68000 series machine.
   2    Copyright 1986, 1987, 1989, 1990, 1992 Free Software Foundation, Inc.
   3
   4 This file is part of GDB.
   5
   6 This program is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2 of the License, or
   9 (at your option) any later version.
  10
  11 This program is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with this program; if not, write to the Free Software
  18 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */
  19
  20 /* Generic 68000 stuff, to be included by other tm-*.h files.
  21    Define HAVE_68881 if that is the case.  */
  22
  23 #if defined (HAVE_68881)
  24 #define IEEE_FLOAT 1
  25 #endif
  26
  27 /* Define the bit, byte, and word ordering of the machine.  */
  28 #define TARGET_BYTE_ORDER BIG_ENDIAN
  29
  30 /* Offset from address of function to start of its code.
  31    Zero on most machines.  */
  32
  33 #define FUNCTION_START_OFFSET 0
  34
  35 /* Advance PC across any function entry prologue instructions
  36    to reach some "real" code.  */
  37
  38 #if !defined(SKIP_PROLOGUE)
  39 #define SKIP_PROLOGUE(ip)   {(ip) = m68k_skip_prologue(ip);}
  40 extern CORE_ADDR m68k_skip_prologue PARAMS ((CORE_ADDR ip));
  41 #endif
  42
  43 /* Immediately after a function call, return the saved pc.
  44    Can't always go through the frames for this because on some machines
  45    the new frame is not set up until the new function executes
  46    some instructions.  */
  47
  48 #define SAVED_PC_AFTER_CALL(frame) \
  49 read_memory_integer (read_register (SP_REGNUM), 4)
  50
  51 /* Stack grows downward.  */
  52
  53 #define INNER_THAN <
  54
  55 /* Sequence of bytes for breakpoint instruction.
  56    This is a TRAP instruction.  The last 4 bits (0xf below) is the
  57    vector.  Systems which don't use 0xf should define BPT_VECTOR
  58    themselves before including this file.  */
  59
  60 #if !defined (BPT_VECTOR)
  61 #define BPT_VECTOR 0xf
  62 #endif
  63
  64 #if !defined (BREAKPOINT)
  65 #define BREAKPOINT {0x4e, (0x40 | BPT_VECTOR)}
  66 #endif
  67
  68 /* If your kernel resets the pc after the trap happens you may need to
  69    define this before including this file.  */
  70
  71 #if !defined (DECR_PC_AFTER_BREAK)
  72 #define DECR_PC_AFTER_BREAK 2
  73 #endif
  74
  75 /* Nonzero if instruction at PC is a return instruction.  */
  76 /* Allow any of the return instructions, including a trapv and a return
  77    from interupt.  */
  78
  79 #define ABOUT_TO_RETURN(pc) ((read_memory_integer (pc, 2) & ~0x3) == 0x4e74)
  80
  81 /* Return 1 if P points to an invalid floating point value.  */
  82
  83 #define INVALID_FLOAT(p, len) 0   /* Just a first guess; not checked */
  84
  85 /* Say how long registers are.  */
  86
  87 #define REGISTER_TYPE long
  88
  89 #if defined (HAVE_68881)
  90 #  if defined (GDB_TARGET_IS_SUN3)
  91     /* Sun3 status includes fpflags, which shows whether the FPU has been used
  92        by the process, and whether the FPU was done with an instruction or
  93        was interrupted in the middle of a long instruction.  See
  94        <machine/reg.h>.  */
  95     /*                      a&d, pc,sr, fp, fpstat, fpflags   */
  96 #    define NUM_REGS 31
  97 #    define REGISTER_BYTES (16*4 + 8 + 8*12 + 3*4 + 4)
  98 #  else /* Not sun3.  */
  99 #    define NUM_REGS 29
 100 #    define REGISTER_BYTES (16*4 + 8 + 8*12 + 3*4)
 101 #  endif /* Not sun3.  */
 102 #else /* No 68881.  */
 103 #  define NUM_REGS 18
 104 #  define REGISTER_BYTES (16*4 + 8)
 105 #endif /* No 68881.  */
 106
 107 /* Index within `registers' of the first byte of the space for
 108    register N.  */
 109
 110 #if defined (HAVE_68881)
 111 #define REGISTER_BYTE(N)  \
 112  ((N) >= FPC_REGNUM ? (((N) - FPC_REGNUM) * 4) + 168    \
 113   : (N) >= FP0_REGNUM ? (((N) - FP0_REGNUM) * 12) + 72  \
 114   : (N) * 4)
 115
 116 /* Number of bytes of storage in the actual machine representation
 117    for register N.  On the 68000, all regs are 4 bytes
 118    except the floating point regs which are 12 bytes.  */
 119 /* Note that the unsigned cast here forces the result of the
 120    subtraction to very high positive values if N < FP0_REGNUM */
 121
 122 #define REGISTER_RAW_SIZE(N) (((unsigned)(N) - FP0_REGNUM) < 8 ? 12 : 4)
 123
 124 /* Number of bytes of storage in the program's representation
 125    for register N.  On the 68000, all regs are 4 bytes
 126    except the floating point regs which are 8-byte doubles.  */
 127
 128 #define REGISTER_VIRTUAL_SIZE(N) (((unsigned)(N) - FP0_REGNUM) < 8 ? 8 : 4)
 129
 130 /* Largest value REGISTER_RAW_SIZE can have.  */
 131
 132 #define MAX_REGISTER_RAW_SIZE 12
 133
 134 /* Largest value REGISTER_VIRTUAL_SIZE can have.  */
 135
 136 #define MAX_REGISTER_VIRTUAL_SIZE 8
 137
 138 /* Nonzero if register N requires conversion
 139    from raw format to virtual format.  */
 140
 141 #define REGISTER_CONVERTIBLE(N) (((unsigned)(N) - FP0_REGNUM) < 8)
 142
 143 /* Put the declaration out here because if it's in the macros, PCC
 144    will complain.  */
 145 extern const struct ext_format ext_format_68881;
 146
 147 /* Convert data from raw format for register REGNUM
 148    to virtual format for register REGNUM.  */
 149
 150 #define REGISTER_CONVERT_TO_VIRTUAL(REGNUM,FROM,TO)     \
 151 { \
 152   if ((REGNUM) >= FP0_REGNUM && (REGNUM) < FPC_REGNUM)  \
 153     ieee_extended_to_double (&ext_format_68881, (FROM), (double *)(TO)); \
 154   else                                  \
 155     memcpy ((TO), (FROM), 4);   \
 156 }
 157
 158 /* Convert data from virtual format for register REGNUM
 159    to raw format for register REGNUM.  */
 160
 161 #define REGISTER_CONVERT_TO_RAW(REGNUM,FROM,TO) \
 162 { \
 163   if ((REGNUM) >= FP0_REGNUM && (REGNUM) < FPC_REGNUM)  \
 164     double_to_ieee_extended (&ext_format_68881, (double *)(FROM), (TO)); \
 165   else                                  \
 166     memcpy ((TO), (FROM), 4);   \
 167 }
 168
 169 /* Return the GDB type object for the "standard" data type
 170    of data in register N.  */
 171 /* Note, for registers which contain addresses return
 172    pointer to void, not pointer to char, because we don't
 173    want to attempt to print the string after printing the address.  */
 174 #define REGISTER_VIRTUAL_TYPE(N) \
 175  (((unsigned)(N) - FP0_REGNUM) < 8 ? builtin_type_double :           \
 176   (N) == PC_REGNUM || (N) == FP_REGNUM || (N) == SP_REGNUM ?         \
 177   lookup_pointer_type (builtin_type_void) : builtin_type_int)
 178
 179 #else /* no 68881.  */
 180 /* Index within `registers' of the first byte of the space for
 181    register N.  */
 182
 183 #define REGISTER_BYTE(N)  ((N) * 4)
 184
 185 /* Number of bytes of storage in the actual machine representation
 186    for register N.  On the 68000, all regs are 4 bytes.  */
 187
 188 #define REGISTER_RAW_SIZE(N) 4
 189
 190 /* Number of bytes of storage in the program's representation
 191    for register N.  On the 68000, all regs are 4 bytes.  */
 192
 193 #define REGISTER_VIRTUAL_SIZE(N) 4
 194
 195 /* Largest value REGISTER_RAW_SIZE can have.  */
 196
 197 #define MAX_REGISTER_RAW_SIZE 4
 198
 199 /* Largest value REGISTER_VIRTUAL_SIZE can have.  */
 200
 201 #define MAX_REGISTER_VIRTUAL_SIZE 4
 202
 203 /* Nonzero if register N requires conversion
 204    from raw format to virtual format.  */
 205
 206 #define REGISTER_CONVERTIBLE(N) 0
 207
 208 /* Convert data from raw format for register REGNUM
 209    to virtual format for register REGNUM.  */
 210
 211 #define REGISTER_CONVERT_TO_VIRTUAL(REGNUM,FROM,TO)  memcpy ((TO), (FROM), 4);
 212
 213 /* Convert data from virtual format for register REGNUM
 214    to raw format for register REGNUM.  */
 215
 216 #define REGISTER_CONVERT_TO_RAW(REGNUM,FROM,TO)  memcpy ((TO), (FROM), 4);
 217
 218 /* Return the GDB type object for the "standard" data type
 219    of data in register N.  */
 220
 221 #define REGISTER_VIRTUAL_TYPE(N)  builtin_type_int
 222
 223 #endif /* No 68881.  */
 224
 225 /* Initializer for an array of names of registers.
 226    Entries beyond the first NUM_REGS are ignored.  */
 227
 228 #define REGISTER_NAMES  \
 229  {"d0", "d1", "d2", "d3", "d4", "d5", "d6", "d7", \
 230   "a0", "a1", "a2", "a3", "a4", "a5", "fp", "sp", \
 231   "ps", "pc",  \
 232   "fp0", "fp1", "fp2", "fp3", "fp4", "fp5", "fp6", "fp7", \
 233   "fpcontrol", "fpstatus", "fpiaddr", "fpcode", "fpflags" }
 234
 235 /* Register numbers of various important registers.
 236    Note that some of these values are "real" register numbers,
 237    and correspond to the general registers of the machine,
 238    and some are "phony" register numbers which are too large
 239    to be actual register numbers as far as the user is concerned
 240    but do serve to get the desired values when passed to read_register.  */
 241
 242 #define A1_REGNUM 9
 243 #define FP_REGNUM 14            /* Contains address of executing stack frame */
 244 #define SP_REGNUM 15            /* Contains address of top of stack */
 245 #define PS_REGNUM 16            /* Contains processor status */
 246 #define PC_REGNUM 17            /* Contains program counter */
 247 #if defined (HAVE_68881)
 248 #define FP0_REGNUM 18           /* Floating point register 0 */
 249 #define FPC_REGNUM 26           /* 68881 control register */
 250 #define FPS_REGNUM 27           /* 68881 status register */
 251 #define FPI_REGNUM 28           /* 68881 iaddr register */
 252 #endif /* 68881.  */
 253
 254 /* Store the address of the place in which to copy the structure the
 255    subroutine will return.  This is called from call_function. */
 256
 257 #define STORE_STRUCT_RETURN(ADDR, SP) \
 258   { write_register (A1_REGNUM, (ADDR)); }
 259
 260 /* Extract from an array REGBUF containing the (raw) register state
 261    a function return value of type TYPE, and copy that, in virtual format,
 262    into VALBUF.  This is assuming that floating point values are returned
 263    as doubles in d0/d1.  */
 264
 265 #if !defined (EXTRACT_RETURN_VALUE)
 266 #define EXTRACT_RETURN_VALUE(TYPE,REGBUF,VALBUF) \
 267   memcpy ((VALBUF),                                                     \
 268           (char *)(REGBUF) +                                            \
 269                  (TYPE_LENGTH(TYPE) >= 4 ? 0 : 4 - TYPE_LENGTH(TYPE)),  \
 270           TYPE_LENGTH(TYPE))
 271 #endif
 272
 273 /* Write into appropriate registers a function return value
 274    of type TYPE, given in virtual format.  Assumes floats are passed
 275    in d0/d1.  */
 276
 277 #if !defined (STORE_RETURN_VALUE)
 278 #define STORE_RETURN_VALUE(TYPE,VALBUF) \
 279   write_register_bytes (0, VALBUF, TYPE_LENGTH (TYPE))
 280 #endif
 281
 282 /* Extract from an array REGBUF containing the (raw) register state
 283    the address in which a function should return its structure value,
 284    as a CORE_ADDR (or an expression that can be used as one).  */
 285
 286 #define EXTRACT_STRUCT_VALUE_ADDRESS(REGBUF) (*(CORE_ADDR *)(REGBUF))
 287 \f
 288 /* Describe the pointer in each stack frame to the previous stack frame
 289    (its caller).  */
 290
 291 /* FRAME_CHAIN takes a frame's nominal address and produces the frame's
 292    chain-pointer.
 293    In the case of the 68000, the frame's nominal address
 294    is the address of a 4-byte word containing the calling frame's address.  */
 295
 296 #define FRAME_CHAIN(thisframe)  \
 297   (!inside_entry_file ((thisframe)->pc) ? \
 298    read_memory_integer ((thisframe)->frame, 4) :\
 299    0)
 300
 301 /* Define other aspects of the stack frame.  */
 302
 303 /* A macro that tells us whether the function invocation represented
 304    by FI does not have a frame on the stack associated with it.  If it
 305    does not, FRAMELESS is set to 1, else 0.  */
 306 #define FRAMELESS_FUNCTION_INVOCATION(FI, FRAMELESS) \
 307   (FRAMELESS) = frameless_look_for_prologue(FI)
 308
 309 #define FRAME_SAVED_PC(FRAME) (read_memory_integer ((FRAME)->frame + 4, 4))
 310
 311 #define FRAME_ARGS_ADDRESS(fi) ((fi)->frame)
 312
 313 #define FRAME_LOCALS_ADDRESS(fi) ((fi)->frame)
 314
 315 /* Set VAL to the number of args passed to frame described by FI.
 316    Can set VAL to -1, meaning no way to tell.  */
 317
 318 /* We can't tell how many args there are
 319    now that the C compiler delays popping them.  */
 320 #if !defined (FRAME_NUM_ARGS)
 321 #define FRAME_NUM_ARGS(val,fi) (val = -1)
 322 #endif
 323
 324 /* Return number of bytes at start of arglist that are not really args.  */
 325
 326 #define FRAME_ARGS_SKIP 8
 327
 328 /* Put here the code to store, into a struct frame_saved_regs,
 329    the addresses of the saved registers of frame described by FRAME_INFO.
 330    This includes special registers such as pc and fp saved in special
 331    ways in the stack frame.  sp is even more special:
 332    the address we return for it IS the sp for the next frame.  */
 333
 334 #if !defined (FRAME_FIND_SAVED_REGS)
 335 #if defined (HAVE_68881)
 336 #define FRAME_FIND_SAVED_REGS(frame_info, frame_saved_regs)             \
 337 { register int regnum;                                                  \
 338   register int regmask;                                                 \
 339   register CORE_ADDR next_addr;                                         \
 340   register CORE_ADDR pc;                                                \
 341   int nextinsn;                                                         \
 342   bzero (&frame_saved_regs, sizeof frame_saved_regs);                   \
 343   if ((frame_info)->pc >= (frame_info)->frame - CALL_DUMMY_LENGTH - FP_REGNUM*4 - 8*12 - 4 \
 344       && (frame_info)->pc <= (frame_info)->frame)                               \
 345     { next_addr = (frame_info)->frame;                                  \
 346       pc = (frame_info)->frame - CALL_DUMMY_LENGTH - FP_REGNUM * 4 - 8*12 - 4; }\
 347   else                                                                  \
 348     { pc = get_pc_function_start ((frame_info)->pc);                    \
 349       /* Verify we have a link a6 instruction next;                     \
 350          if not we lose.  If we win, find the address above the saved   \
 351          regs using the amount of storage from the link instruction.  */\
 352       if (044016 == read_memory_integer (pc, 2))                        \
 353         next_addr = (frame_info)->frame + read_memory_integer (pc += 2, 4), pc+=4; \
 354       else if (047126 == read_memory_integer (pc, 2))                   \
 355         next_addr = (frame_info)->frame + read_memory_integer (pc += 2, 2), pc+=2; \
 356       else goto lose;                                                   \
 357       /* If have an addal #-n, sp next, adjust next_addr.  */           \
 358       if ((0177777 & read_memory_integer (pc, 2)) == 0157774)           \
 359         next_addr += read_memory_integer (pc += 2, 4), pc += 4;         \
 360     }                                                                   \
 361   /* next should be a moveml to (sp) or -(sp) or a movl r,-(sp) */      \
 362   regmask = read_memory_integer (pc + 2, 2);                            \
 363   /* But before that can come an fmovem.  Check for it.  */             \
 364   nextinsn = 0xffff & read_memory_integer (pc, 2);                      \
 365   if (0xf227 == nextinsn                                                \
 366       && (regmask & 0xff00) == 0xe000)                                  \
 367     { pc += 4; /* Regmask's low bit is for register fp7, the first pushed */ \
 368       for (regnum = FP0_REGNUM + 7; regnum >= FP0_REGNUM; regnum--, regmask >>= 1)              \
 369         if (regmask & 1)                                                \
 370           (frame_saved_regs).regs[regnum] = (next_addr -= 12);          \
 371       regmask = read_memory_integer (pc + 2, 2); }                      \
 372   if (0044327 == read_memory_integer (pc, 2))                           \
 373     { pc += 4; /* Regmask's low bit is for register 0, the first written */ \
 374       for (regnum = 0; regnum < 16; regnum++, regmask >>= 1)            \
 375         if (regmask & 1)                                                \
 376           (frame_saved_regs).regs[regnum] = (next_addr += 4) - 4; }     \
 377   else if (0044347 == read_memory_integer (pc, 2))                      \
 378     { pc += 4; /* Regmask's low bit is for register 15, the first pushed */ \
 379       for (regnum = 15; regnum >= 0; regnum--, regmask >>= 1)           \
 380         if (regmask & 1)                                                \
 381           (frame_saved_regs).regs[regnum] = (next_addr -= 4); }         \
 382   else if (0x2f00 == (0xfff0 & read_memory_integer (pc, 2)))            \
 383     { regnum = 0xf & read_memory_integer (pc, 2); pc += 2;              \
 384       (frame_saved_regs).regs[regnum] = (next_addr -= 4); }             \
 385   /* fmovemx to index of sp may follow.  */                             \
 386   regmask = read_memory_integer (pc + 2, 2);                            \
 387   nextinsn = 0xffff & read_memory_integer (pc, 2);                      \
 388   if (0xf236 == nextinsn                                                \
 389       && (regmask & 0xff00) == 0xf000)                                  \
 390     { pc += 10; /* Regmask's low bit is for register fp0, the first written */ \
 391       for (regnum = FP0_REGNUM + 7; regnum >= FP0_REGNUM; regnum--, regmask >>= 1)              \
 392         if (regmask & 1)                                                \
 393           (frame_saved_regs).regs[regnum] = (next_addr += 12) - 12;     \
 394       regmask = read_memory_integer (pc + 2, 2); }                      \
 395   /* clrw -(sp); movw ccr,-(sp) may follow.  */                         \
 396   if (0x426742e7 == read_memory_integer (pc, 4))                        \
 397     (frame_saved_regs).regs[PS_REGNUM] = (next_addr -= 4);              \
 398   lose: ;                                                               \
 399   (frame_saved_regs).regs[SP_REGNUM] = (frame_info)->frame + 8;         \
 400   (frame_saved_regs).regs[FP_REGNUM] = (frame_info)->frame;             \
 401   (frame_saved_regs).regs[PC_REGNUM] = (frame_info)->frame + 4;         \
 402 }
 403 #else /* no 68881.  */
 404 #define FRAME_FIND_SAVED_REGS(frame_info, frame_saved_regs)             \
 405 { register int regnum;                                                  \
 406   register int regmask;                                                 \
 407   register CORE_ADDR next_addr;                                         \
 408   register CORE_ADDR pc;                                                \
 409   bzero (&frame_saved_regs, sizeof frame_saved_regs);                   \
 410   if ((frame_info)->pc >= (frame_info)->frame - CALL_DUMMY_LENGTH - FP_REGNUM*4 - 4 \
 411       && (frame_info)->pc <= (frame_info)->frame)                               \
 412     { next_addr = (frame_info)->frame;                                  \
 413       pc = (frame_info)->frame - CALL_DUMMY_LENGTH - FP_REGNUM * 4 - 4; }\
 414   else                                                                  \
 415     { pc = get_pc_function_start ((frame_info)->pc);                    \
 416       /* Verify we have a link a6 instruction next;                     \
 417          if not we lose.  If we win, find the address above the saved   \
 418          regs using the amount of storage from the link instruction.  */\
 419       if (044016 == read_memory_integer (pc, 2))                        \
 420         next_addr = (frame_info)->frame + read_memory_integer (pc += 2, 4), pc+=4; \
 421       else if (047126 == read_memory_integer (pc, 2))                   \
 422         next_addr = (frame_info)->frame + read_memory_integer (pc += 2, 2), pc+=2; \
 423       else goto lose;                                                   \
 424       /* If have an addal #-n, sp next, adjust next_addr.  */           \
 425       if ((0177777 & read_memory_integer (pc, 2)) == 0157774)           \
 426         next_addr += read_memory_integer (pc += 2, 4), pc += 4;         \
 427     }                                                                   \
 428   /* next should be a moveml to (sp) or -(sp) or a movl r,-(sp) */      \
 429   regmask = read_memory_integer (pc + 2, 2);                            \
 430   if (0044327 == read_memory_integer (pc, 2))                           \
 431     { pc += 4; /* Regmask's low bit is for register 0, the first written */ \
 432       for (regnum = 0; regnum < 16; regnum++, regmask >>= 1)            \
 433         if (regmask & 1)                                                \
 434           (frame_saved_regs).regs[regnum] = (next_addr += 4) - 4; }     \
 435   else if (0044347 == read_memory_integer (pc, 2))                      \
 436     { pc += 4; /* Regmask's low bit is for register 15, the first pushed */ \
 437       for (regnum = 15; regnum >= 0; regnum--, regmask >>= 1)           \
 438         if (regmask & 1)                                                \
 439           (frame_saved_regs).regs[regnum] = (next_addr -= 4); }         \
 440   else if (0x2f00 == (0xfff0 & read_memory_integer (pc, 2)))            \
 441     { regnum = 0xf & read_memory_integer (pc, 2); pc += 2;              \
 442       (frame_saved_regs).regs[regnum] = (next_addr -= 4); }             \
 443   /* clrw -(sp); movw ccr,-(sp) may follow.  */                         \
 444   if (0x426742e7 == read_memory_integer (pc, 4))                        \
 445     (frame_saved_regs).regs[PS_REGNUM] = (next_addr -= 4);              \
 446   lose: ;                                                               \
 447   (frame_saved_regs).regs[SP_REGNUM] = (frame_info)->frame + 8;         \
 448   (frame_saved_regs).regs[FP_REGNUM] = (frame_info)->frame;             \
 449   (frame_saved_regs).regs[PC_REGNUM] = (frame_info)->frame + 4;         \
 450 }
 451 #endif /* no 68881.  */
 452 #endif /* no FIND_FRAME_SAVED_REGS.  */
 453
 454 \f
 455 /* Things needed for making the inferior call functions.
 456    It seems like every m68k based machine has almost identical definitions
 457    in the individual machine's configuration files.  Most other cpu types
 458    (mips, i386, etc) have routines in their *-tdep.c files to handle this
 459    for most configurations.  The m68k family should be able to do this as
 460    well.  These macros can still be overridden when necessary.  */
 461
 462 /* The CALL_DUMMY macro is the sequence of instructions, as disassembled
 463    by gdb itself:
 464
 465         fmovemx fp0-fp7,sp@-                    0xf227 0xe0ff
 466         moveml d0-a5,sp@-                       0x48e7 0xfffc
 467         clrw sp@-                               0x4267
 468         movew ccr,sp@-                          0x42e7
 469
 470         /..* The arguments are pushed at this point by GDB;
 471         no code is needed in the dummy for this.
 472         The CALL_DUMMY_START_OFFSET gives the position of
 473         the following jsr instruction.  *../
 474
 475         jsr @#0x32323232                        0x4eb9 0x3232 0x3232
 476         addal #0x69696969,sp                    0xdffc 0x6969 0x6969
 477         trap #<your BPT_VECTOR number here>     0x4e4?
 478         nop                                     0x4e71
 479
 480    Note this is CALL_DUMMY_LENGTH bytes (28 for the above example).
 481    We actually start executing at the jsr, since the pushing of the
 482    registers is done by PUSH_DUMMY_FRAME.  If this were real code,
 483    the arguments for the function called by the jsr would be pushed
 484    between the moveml and the jsr, and we could allow it to execute through.
 485    But the arguments have to be pushed by GDB after the PUSH_DUMMY_FRAME is
 486    done, and we cannot allow the moveml to push the registers again lest
 487    they be taken for the arguments.  */
 488
 489 #if defined (HAVE_68881)
 490
 491 #define CALL_DUMMY {0xf227e0ff, 0x48e7fffc, 0x426742e7, 0x4eb93232, 0x3232dffc, 0x69696969, (0x4e404e71 | (BPT_VECTOR << 16))}
 492 #define CALL_DUMMY_LENGTH 28            /* Size of CALL_DUMMY */
 493 #define CALL_DUMMY_START_OFFSET 12      /* Offset to jsr instruction*/
 494
 495 #else
 496
 497 #define CALL_DUMMY {0x48e7fffc, 0x426742e7, 0x4eb93232, 0x3232dffc, 0x69696969, (0x4e404e71 | (BPT_VECTOR << 16))}
 498 #define CALL_DUMMY_LENGTH 24            /* Size of CALL_DUMMY */
 499 #define CALL_DUMMY_START_OFFSET 8       /* Offset to jsr instruction*/
 500
 501 #endif  /* HAVE_68881 */
 502
 503 /* Insert the specified number of args and function address
 504    into a call sequence of the above form stored at DUMMYNAME.
 505    We use the BFD routines to store a big-endian value of known size.  */
 506
 507 #define FIX_CALL_DUMMY(dummyname, pc, fun, nargs, args, type, gcc_p)     \
 508 { _do_putb32 (fun,     (char *) dummyname + CALL_DUMMY_START_OFFSET + 2);  \
 509   _do_putb32 (nargs*4, (char *) dummyname + CALL_DUMMY_START_OFFSET + 8); }
 510
 511 /* Push an empty stack frame, to record the current PC, etc.  */
 512
 513 #define PUSH_DUMMY_FRAME        { m68k_push_dummy_frame (); }
 514
 515 extern void m68k_push_dummy_frame PARAMS ((void));
 516
 517 extern void m68k_pop_frame PARAMS ((void));
 518
 519 /* Discard from the stack the innermost frame, restoring all registers.  */
 520
 521 #define POP_FRAME               { m68k_pop_frame (); }
 522
 523 /* Offset from SP to first arg on stack at first instruction of a function */
 524
 525 #define SP_ARG0 (1 * 4)