gdb/tm-68k.h

   1 /* Parameters for execution on a 68000 series machine.
   2    Copyright (C) 1986, 1987, 1989, 1990 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 ();
  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 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     bcopy ((FROM), (TO), 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     bcopy ((FROM), (TO), 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)  bcopy ((FROM), (TO), 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)  bcopy ((FROM), (TO), 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   bcopy ((char *)(REGBUF) +                                             \
 268                  (TYPE_LENGTH(TYPE) >= 4 ? 0 : 4 - TYPE_LENGTH(TYPE)),  \
 269          VALBUF, TYPE_LENGTH(TYPE))
 270 #endif
 271
 272 /* Write into appropriate registers a function return value
 273    of type TYPE, given in virtual format.  Assumes floats are passed
 274    in d0/d1.  */
 275
 276 #if !defined (STORE_RETURN_VALUE)
 277 #define STORE_RETURN_VALUE(TYPE,VALBUF) \
 278   write_register_bytes (0, VALBUF, TYPE_LENGTH (TYPE))
 279 #endif
 280
 281 /* Extract from an array REGBUF containing the (raw) register state
 282    the address in which a function should return its structure value,
 283    as a CORE_ADDR (or an expression that can be used as one).  */
 284
 285 #define EXTRACT_STRUCT_VALUE_ADDRESS(REGBUF) (*(CORE_ADDR *)(REGBUF))
 286 \f
 287 /* Describe the pointer in each stack frame to the previous stack frame
 288    (its caller).  */
 289
 290 /* FRAME_CHAIN takes a frame's nominal address
 291    and produces the frame's chain-pointer.
 292
 293    However, if FRAME_CHAIN_VALID returns zero,
 294    it means the given frame is the outermost one and has no caller.  */
 295
 296 /* In the case of the 68000, the frame's nominal address
 297    is the address of a 4-byte word containing the calling frame's address.  */
 298
 299 #define FRAME_CHAIN(thisframe)  \
 300   (outside_startup_file ((thisframe)->pc) ? \
 301    read_memory_integer ((thisframe)->frame, 4) :\
 302    0)
 303
 304 #if defined (FRAME_CHAIN_VALID_ALTERNATE)
 305
 306 /* Use the alternate method of avoiding running up off the end of
 307    the frame chain or following frames back into the startup code.
 308    See the comments in blockframe.c */
 309
 310 #define FRAME_CHAIN_VALID(chain, thisframe)     \
 311   (chain != 0                                   \
 312    && !(inside_main_scope ((thisframe)->pc))    \
 313    && !(inside_entry_scope ((thisframe)->pc)))
 314
 315 #else
 316
 317 #define FRAME_CHAIN_VALID(chain, thisframe) \
 318   (chain != 0 && outside_startup_file (FRAME_SAVED_PC (thisframe)))
 319
 320 #endif  /* FRAME_CHAIN_VALID_ALTERNATE */
 321
 322 /* Define other aspects of the stack frame.  */
 323
 324 /* A macro that tells us whether the function invocation represented
 325    by FI does not have a frame on the stack associated with it.  If it
 326    does not, FRAMELESS is set to 1, else 0.  */
 327 #define FRAMELESS_FUNCTION_INVOCATION(FI, FRAMELESS) \
 328   (FRAMELESS) = frameless_look_for_prologue(FI)
 329
 330 #define FRAME_SAVED_PC(FRAME) (read_memory_integer ((FRAME)->frame + 4, 4))
 331
 332 #define FRAME_ARGS_ADDRESS(fi) ((fi)->frame)
 333
 334 #define FRAME_LOCALS_ADDRESS(fi) ((fi)->frame)
 335
 336 /* Set VAL to the number of args passed to frame described by FI.
 337    Can set VAL to -1, meaning no way to tell.  */
 338
 339 /* We can't tell how many args there are
 340    now that the C compiler delays popping them.  */
 341 #if !defined (FRAME_NUM_ARGS)
 342 #define FRAME_NUM_ARGS(val,fi) (val = -1)
 343 #endif
 344
 345 /* Return number of bytes at start of arglist that are not really args.  */
 346
 347 #define FRAME_ARGS_SKIP 8
 348
 349 /* Put here the code to store, into a struct frame_saved_regs,
 350    the addresses of the saved registers of frame described by FRAME_INFO.
 351    This includes special registers such as pc and fp saved in special
 352    ways in the stack frame.  sp is even more special:
 353    the address we return for it IS the sp for the next frame.  */
 354
 355 #if !defined (FRAME_FIND_SAVED_REGS)
 356 #if defined (HAVE_68881)
 357 #define FRAME_FIND_SAVED_REGS(frame_info, frame_saved_regs)             \
 358 { register int regnum;                                                  \
 359   register int regmask;                                                 \
 360   register CORE_ADDR next_addr;                                         \
 361   register CORE_ADDR pc;                                                \
 362   int nextinsn;                                                         \
 363   bzero (&frame_saved_regs, sizeof frame_saved_regs);                   \
 364   if ((frame_info)->pc >= (frame_info)->frame - CALL_DUMMY_LENGTH - FP_REGNUM*4 - 8*12 - 4 \
 365       && (frame_info)->pc <= (frame_info)->frame)                               \
 366     { next_addr = (frame_info)->frame;                                  \
 367       pc = (frame_info)->frame - CALL_DUMMY_LENGTH - FP_REGNUM * 4 - 8*12 - 4; }\
 368   else                                                                  \
 369     { pc = get_pc_function_start ((frame_info)->pc);                    \
 370       /* Verify we have a link a6 instruction next;                     \
 371          if not we lose.  If we win, find the address above the saved   \
 372          regs using the amount of storage from the link instruction.  */\
 373       if (044016 == read_memory_integer (pc, 2))                        \
 374         next_addr = (frame_info)->frame + read_memory_integer (pc += 2, 4), pc+=4; \
 375       else if (047126 == read_memory_integer (pc, 2))                   \
 376         next_addr = (frame_info)->frame + read_memory_integer (pc += 2, 2), pc+=2; \
 377       else goto lose;                                                   \
 378       /* If have an addal #-n, sp next, adjust next_addr.  */           \
 379       if ((0177777 & read_memory_integer (pc, 2)) == 0157774)           \
 380         next_addr += read_memory_integer (pc += 2, 4), pc += 4;         \
 381     }                                                                   \
 382   /* next should be a moveml to (sp) or -(sp) or a movl r,-(sp) */      \
 383   regmask = read_memory_integer (pc + 2, 2);                            \
 384   /* But before that can come an fmovem.  Check for it.  */             \
 385   nextinsn = 0xffff & read_memory_integer (pc, 2);                      \
 386   if (0xf227 == nextinsn                                                \
 387       && (regmask & 0xff00) == 0xe000)                                  \
 388     { pc += 4; /* Regmask's low bit is for register fp7, the first pushed */ \
 389       for (regnum = FP0_REGNUM + 7; regnum >= FP0_REGNUM; regnum--, regmask >>= 1)              \
 390         if (regmask & 1)                                                \
 391           (frame_saved_regs).regs[regnum] = (next_addr -= 12);          \
 392       regmask = read_memory_integer (pc + 2, 2); }                      \
 393   if (0044327 == read_memory_integer (pc, 2))                           \
 394     { pc += 4; /* Regmask's low bit is for register 0, the first written */ \
 395       for (regnum = 0; regnum < 16; regnum++, regmask >>= 1)            \
 396         if (regmask & 1)                                                \
 397           (frame_saved_regs).regs[regnum] = (next_addr += 4) - 4; }     \
 398   else if (0044347 == read_memory_integer (pc, 2))                      \
 399     { pc += 4; /* Regmask's low bit is for register 15, the first pushed */ \
 400       for (regnum = 15; regnum >= 0; regnum--, regmask >>= 1)           \
 401         if (regmask & 1)                                                \
 402           (frame_saved_regs).regs[regnum] = (next_addr -= 4); }         \
 403   else if (0x2f00 == (0xfff0 & read_memory_integer (pc, 2)))            \
 404     { regnum = 0xf & read_memory_integer (pc, 2); pc += 2;              \
 405       (frame_saved_regs).regs[regnum] = (next_addr -= 4); }             \
 406   /* fmovemx to index of sp may follow.  */                             \
 407   regmask = read_memory_integer (pc + 2, 2);                            \
 408   nextinsn = 0xffff & read_memory_integer (pc, 2);                      \
 409   if (0xf236 == nextinsn                                                \
 410       && (regmask & 0xff00) == 0xf000)                                  \
 411     { pc += 10; /* Regmask's low bit is for register fp0, the first written */ \
 412       for (regnum = FP0_REGNUM + 7; regnum >= FP0_REGNUM; regnum--, regmask >>= 1)              \
 413         if (regmask & 1)                                                \
 414           (frame_saved_regs).regs[regnum] = (next_addr += 12) - 12;     \
 415       regmask = read_memory_integer (pc + 2, 2); }                      \
 416   /* clrw -(sp); movw ccr,-(sp) may follow.  */                         \
 417   if (0x426742e7 == read_memory_integer (pc, 4))                        \
 418     (frame_saved_regs).regs[PS_REGNUM] = (next_addr -= 4);              \
 419   lose: ;                                                               \
 420   (frame_saved_regs).regs[SP_REGNUM] = (frame_info)->frame + 8;         \
 421   (frame_saved_regs).regs[FP_REGNUM] = (frame_info)->frame;             \
 422   (frame_saved_regs).regs[PC_REGNUM] = (frame_info)->frame + 4;         \
 423 }
 424 #else /* no 68881.  */
 425 #define FRAME_FIND_SAVED_REGS(frame_info, frame_saved_regs)             \
 426 { register int regnum;                                                  \
 427   register int regmask;                                                 \
 428   register CORE_ADDR next_addr;                                         \
 429   register CORE_ADDR pc;                                                \
 430   bzero (&frame_saved_regs, sizeof frame_saved_regs);                   \
 431   if ((frame_info)->pc >= (frame_info)->frame - CALL_DUMMY_LENGTH - FP_REGNUM*4 - 4 \
 432       && (frame_info)->pc <= (frame_info)->frame)                               \
 433     { next_addr = (frame_info)->frame;                                  \
 434       pc = (frame_info)->frame - CALL_DUMMY_LENGTH - FP_REGNUM * 4 - 4; }\
 435   else                                                                  \
 436     { pc = get_pc_function_start ((frame_info)->pc);                    \
 437       /* Verify we have a link a6 instruction next;                     \
 438          if not we lose.  If we win, find the address above the saved   \
 439          regs using the amount of storage from the link instruction.  */\
 440       if (044016 == read_memory_integer (pc, 2))                        \
 441         next_addr = (frame_info)->frame + read_memory_integer (pc += 2, 4), pc+=4; \
 442       else if (047126 == read_memory_integer (pc, 2))                   \
 443         next_addr = (frame_info)->frame + read_memory_integer (pc += 2, 2), pc+=2; \
 444       else goto lose;                                                   \
 445       /* If have an addal #-n, sp next, adjust next_addr.  */           \
 446       if ((0177777 & read_memory_integer (pc, 2)) == 0157774)           \
 447         next_addr += read_memory_integer (pc += 2, 4), pc += 4;         \
 448     }                                                                   \
 449   /* next should be a moveml to (sp) or -(sp) or a movl r,-(sp) */      \
 450   regmask = read_memory_integer (pc + 2, 2);                            \
 451   if (0044327 == read_memory_integer (pc, 2))                           \
 452     { pc += 4; /* Regmask's low bit is for register 0, the first written */ \
 453       for (regnum = 0; regnum < 16; regnum++, regmask >>= 1)            \
 454         if (regmask & 1)                                                \
 455           (frame_saved_regs).regs[regnum] = (next_addr += 4) - 4; }     \
 456   else if (0044347 == read_memory_integer (pc, 2))                      \
 457     { pc += 4; /* Regmask's low bit is for register 15, the first pushed */ \
 458       for (regnum = 15; regnum >= 0; regnum--, regmask >>= 1)           \
 459         if (regmask & 1)                                                \
 460           (frame_saved_regs).regs[regnum] = (next_addr -= 4); }         \
 461   else if (0x2f00 == 0xfff0 & read_memory_integer (pc, 2))              \
 462     { regnum = 0xf & read_memory_integer (pc, 2); pc += 2;              \
 463       (frame_saved_regs).regs[regnum] = (next_addr -= 4); }             \
 464   /* clrw -(sp); movw ccr,-(sp) may follow.  */                         \
 465   if (0x426742e7 == read_memory_integer (pc, 4))                        \
 466     (frame_saved_regs).regs[PS_REGNUM] = (next_addr -= 4);              \
 467   lose: ;                                                               \
 468   (frame_saved_regs).regs[SP_REGNUM] = (frame_info)->frame + 8;         \
 469   (frame_saved_regs).regs[FP_REGNUM] = (frame_info)->frame;             \
 470   (frame_saved_regs).regs[PC_REGNUM] = (frame_info)->frame + 4;         \
 471 }
 472 #endif /* no 68881.  */
 473 #endif /* no FIND_FRAME_SAVED_REGS.  */
 474
 475 \f
 476 /* Things needed for making the inferior call functions.
 477    It seems like every m68k based machine has almost identical definitions
 478    in the individual machine's configuration files.  Most other cpu types
 479    (mips, i386, etc) have routines in their *-tdep.c files to handle this
 480    for most configurations.  The m68k family should be able to do this as
 481    well.  These macros can still be overridden when necessary.  */
 482
 483 /* The CALL_DUMMY macro is the sequence of instructions, as disassembled
 484    by gdb itself:
 485
 486         fmovemx fp0-fp7,sp@-                    0xf227 0xe0ff
 487         moveml d0-a5,sp@-                       0x48e7 0xfffc
 488         clrw sp@-                               0x4267
 489         movew ccr,sp@-                          0x42e7
 490
 491         /..* The arguments are pushed at this point by GDB;
 492         no code is needed in the dummy for this.
 493         The CALL_DUMMY_START_OFFSET gives the position of
 494         the following jsr instruction.  *../
 495
 496         jsr @#0x32323232                        0x4eb9 0x3232 0x3232
 497         addal #0x69696969,sp                    0xdffc 0x6969 0x6969
 498         trap #<your BPT_VECTOR number here>     0x4e4?
 499         nop                                     0x4e71
 500
 501    Note this is CALL_DUMMY_LENGTH bytes (28 for the above example).
 502    We actually start executing at the jsr, since the pushing of the
 503    registers is done by PUSH_DUMMY_FRAME.  If this were real code,
 504    the arguments for the function called by the jsr would be pushed
 505    between the moveml and the jsr, and we could allow it to execute through.
 506    But the arguments have to be pushed by GDB after the PUSH_DUMMY_FRAME is
 507    done, and we cannot allow the moveml to push the registers again lest
 508    they be taken for the arguments.  */
 509
 510 #if defined (HAVE_68881)
 511
 512 #define CALL_DUMMY {0xf227e0ff, 0x48e7fffc, 0x426742e7, 0x4eb93232, 0x3232dffc, 0x69696969, (0x4e404e71 | (BPT_VECTOR << 16))}
 513 #define CALL_DUMMY_LENGTH 28            /* Size of CALL_DUMMY */
 514 #define CALL_DUMMY_START_OFFSET 12      /* Offset to jsr instruction*/
 515
 516 #else
 517
 518 #define CALL_DUMMY {0x48e7fffc, 0x426742e7, 0x4eb93232, 0x3232dffc, 0x69696969, (0x4e404e71 | (BPT_VECTOR << 16))}
 519 #define CALL_DUMMY_LENGTH 24            /* Size of CALL_DUMMY */
 520 #define CALL_DUMMY_START_OFFSET 8       /* Offset to jsr instruction*/
 521
 522 #endif  /* HAVE_68881 */
 523
 524 /* Insert the specified number of args and function address
 525    into a call sequence of the above form stored at DUMMYNAME.  */
 526
 527 #define FIX_CALL_DUMMY(dummyname, pc, fun, nargs, args, type, gcc_p)     \
 528 { *(int *)((char *) dummyname + CALL_DUMMY_START_OFFSET + 2) = fun;  \
 529   *(int *)((char *) dummyname + CALL_DUMMY_START_OFFSET + 8) = nargs * 4; }
 530
 531 /* Push an empty stack frame, to record the current PC, etc.  */
 532
 533 #define PUSH_DUMMY_FRAME        { m68k_push_dummy_frame (); }
 534
 535 /* Discard from the stack the innermost frame, restoring all registers.  */
 536
 537 #define POP_FRAME               { m68k_pop_frame (); }
 538