gdb/v850-tdep.c

   1 /* Target-dependent code for the NEC V850 for GDB, the GNU debugger.
   2    Copyright 1996, 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  19
  20 #include "defs.h"
  21 #include "frame.h"
  22 #include "inferior.h"
  23 #include "obstack.h"
  24 #include "target.h"
  25 #include "value.h"
  26 #include "bfd.h"
  27 #include "gdb_string.h"
  28 #include "gdbcore.h"
  29 #include "symfile.h"
  30
  31 /* Info gleaned from scanning a function's prologue.  */
  32
  33 struct pifsr                    /* Info about one saved reg */
  34 {
  35   int framereg;                 /* Frame reg (SP or FP) */
  36   int offset;                   /* Offset from framereg */
  37   int reg;                      /* Saved register number */
  38 };
  39
  40 struct prologue_info
  41 {
  42   int framereg;
  43   int frameoffset;
  44   int start_function;
  45   struct pifsr *pifsrs;
  46 };
  47
  48 static CORE_ADDR v850_scan_prologue PARAMS ((CORE_ADDR pc,
  49                                              struct prologue_info *fs));
  50 \f
  51 /* Function: scan_prologue
  52    Scan the prologue of the function that contains PC, and record what
  53    we find in PI.  PI->fsr must be zeroed by the called.  Returns the
  54    pc after the prologue.  Note that the addresses saved in pi->fsr
  55    are actually just frame relative (negative offsets from the frame
  56    pointer).  This is because we don't know the actual value of the
  57    frame pointer yet.  In some circumstances, the frame pointer can't
  58    be determined till after we have scanned the prologue.  */
  59
  60 static CORE_ADDR
  61 v850_scan_prologue (pc, pi)
  62      CORE_ADDR pc;
  63      struct prologue_info *pi;
  64 {
  65   CORE_ADDR func_addr, prologue_end, current_pc;
  66   struct pifsr *pifsr;
  67   int fp_used;
  68
  69   /* First, figure out the bounds of the prologue so that we can limit the
  70      search to something reasonable.  */
  71
  72   if (find_pc_partial_function (pc, NULL, &func_addr, NULL))
  73     {
  74       struct symtab_and_line sal;
  75
  76       sal = find_pc_line (func_addr, 0);
  77
  78       if (func_addr == entry_point_address ())
  79         pi->start_function = 1;
  80       else
  81         pi->start_function = 0;
  82
  83 #if 0
  84       if (sal.line == 0)
  85         prologue_end = pc;
  86       else
  87         prologue_end = sal.end;
  88 #else
  89       prologue_end = pc;
  90 #endif
  91     }
  92   else
  93     {                           /* We're in the boondocks */
  94       func_addr = pc - 100;
  95       prologue_end = pc;
  96     }
  97
  98   prologue_end = min (prologue_end, pc);
  99
 100   /* Now, search the prologue looking for instructions that setup fp, save
 101      rp, adjust sp and such.  We also record the frame offset of any saved
 102      registers. */
 103
 104   pi->frameoffset = 0;
 105   pi->framereg = SP_REGNUM;
 106   fp_used = 0;
 107   pifsr = pi->pifsrs;
 108
 109   for (current_pc = func_addr; current_pc < prologue_end; current_pc += 2)
 110     {
 111       int insn;
 112
 113       insn = read_memory_unsigned_integer (current_pc, 2);
 114
 115       if ((insn & 0x07c0) == 0x0780 /* jarl or jr */
 116           || (insn & 0xffe0) == 0x0060 /* jmp */
 117           || (insn & 0x0780) == 0x0580) /* branch */
 118         break;                  /* Ran into end of prologue */
 119       if ((insn & 0xffe0) == ((SP_REGNUM << 11) | 0x0240)) /* add <imm>,sp */
 120         pi->frameoffset = ((insn & 0x1f) ^ 0x10) - 0x10;
 121       else if (insn == ((SP_REGNUM << 11) | 0x0600 | SP_REGNUM)) /* addi <imm>,sp,sp */
 122         pi->frameoffset = read_memory_integer (current_pc + 2, 2);
 123       else if (insn == ((FP_REGNUM << 11) | 0x0000 | 12)) /* mov r12,fp */
 124         {
 125           fp_used = 1;
 126           pi->framereg = FP_REGNUM;
 127         }
 128       else if ((insn & 0x07ff) == (0x0760 | SP_REGNUM)  /* st.w <reg>,<offset>[sp] */
 129                || (fp_used
 130                    && (insn & 0x07ff) == (0x0760 | FP_REGNUM))) /* st.w <reg>,<offset>[fp] */
 131         if (pifsr)
 132           {
 133             pifsr->framereg = insn & 0x1f;
 134             pifsr->reg = (insn >> 11) & 0x1f; /* Extract <reg> */
 135
 136             pifsr->offset = read_memory_integer (current_pc + 2, 2) & ~1;
 137
 138             pifsr++;
 139           }
 140
 141       if ((insn & 0x0780) >= 0x0600) /* Four byte instruction? */
 142         current_pc += 2;
 143     }
 144
 145   if (pifsr)
 146     pifsr->framereg = 0;        /* Tie off last entry */
 147
 148   return current_pc;
 149 }
 150
 151 /* Function: init_extra_frame_info
 152    Setup the frame's frame pointer, pc, and frame addresses for saved
 153    registers.  Most of the work is done in scan_prologue().
 154
 155    Note that when we are called for the last frame (currently active frame),
 156    that fi->pc and fi->frame will already be setup.  However, fi->frame will
 157    be valid only if this routine uses FP.  For previous frames, fi-frame will
 158    always be correct (since that is derived from v850_frame_chain ()).
 159
 160    We can be called with the PC in the call dummy under two circumstances.
 161    First, during normal backtracing, second, while figuring out the frame
 162    pointer just prior to calling the target function (see run_stack_dummy).  */
 163
 164 void
 165 v850_init_extra_frame_info (fi)
 166      struct frame_info *fi;
 167 {
 168   struct prologue_info pi;
 169   struct pifsr pifsrs[NUM_REGS + 1], *pifsr;
 170   int reg;
 171
 172   if (fi->next)
 173     fi->pc = FRAME_SAVED_PC (fi->next);
 174
 175   memset (fi->fsr.regs, '\000', sizeof fi->fsr.regs);
 176
 177   /* The call dummy doesn't save any registers on the stack, so we can return
 178      now.  */
 179   if (PC_IN_CALL_DUMMY (fi->pc, fi->frame, fi->frame))
 180       return;
 181
 182   pi.pifsrs = pifsrs;
 183
 184   v850_scan_prologue (fi->pc, &pi);
 185
 186   if (!fi->next && pi.framereg == SP_REGNUM)
 187     fi->frame = read_register (pi.framereg) - pi.frameoffset;
 188
 189   for (pifsr = pifsrs; pifsr->framereg; pifsr++)
 190     {
 191       fi->fsr.regs[pifsr->reg] = pifsr->offset + fi->frame;
 192
 193       if (pifsr->framereg == SP_REGNUM)
 194         fi->fsr.regs[pifsr->reg] += pi.frameoffset;
 195     }
 196 }
 197
 198 /* Function: frame_chain
 199    Figure out the frame prior to FI.  Unfortunately, this involves
 200    scanning the prologue of the caller, which will also be done
 201    shortly by v850_init_extra_frame_info.  For the dummy frame, we
 202    just return the stack pointer that was in use at the time the
 203    function call was made.  */
 204
 205 CORE_ADDR
 206 v850_frame_chain (fi)
 207      struct frame_info *fi;
 208 {
 209   struct prologue_info pi;
 210   CORE_ADDR callers_pc, fp;
 211
 212   /* First, find out who called us */
 213   callers_pc = FRAME_SAVED_PC (fi);
 214   /* If caller is a call-dummy, then our FP bears no relation to his FP! */
 215   fp = v850_find_callers_reg (fi, FP_REGNUM);
 216   if (PC_IN_CALL_DUMMY(callers_pc, fp, fp))
 217     return fp;  /* caller is call-dummy: return oldest value of FP */
 218
 219   /* Caller is NOT a call-dummy, so everything else should just work.
 220      Even if THIS frame is a call-dummy! */
 221   pi.pifsrs = NULL;
 222
 223   v850_scan_prologue (callers_pc, &pi);
 224
 225   if (pi.start_function)
 226     return 0;                   /* Don't chain beyond the start function */
 227
 228   if (pi.framereg == FP_REGNUM)
 229     return v850_find_callers_reg (fi, pi.framereg);
 230
 231   return fi->frame - pi.frameoffset;
 232 }
 233
 234 /* Function: find_callers_reg
 235    Find REGNUM on the stack.  Otherwise, it's in an active register.
 236    One thing we might want to do here is to check REGNUM against the
 237    clobber mask, and somehow flag it as invalid if it isn't saved on
 238    the stack somewhere.  This would provide a graceful failure mode
 239    when trying to get the value of caller-saves registers for an inner
 240    frame.  */
 241
 242 CORE_ADDR
 243 v850_find_callers_reg (fi, regnum)
 244      struct frame_info *fi;
 245      int regnum;
 246 {
 247   for (; fi; fi = fi->next)
 248     if (PC_IN_CALL_DUMMY (fi->pc, fi->frame, fi->frame))
 249       return generic_read_register_dummy (fi->pc, fi->frame, regnum);
 250     else if (fi->fsr.regs[regnum] != 0)
 251       return read_memory_unsigned_integer (fi->fsr.regs[regnum],
 252                                            REGISTER_RAW_SIZE(regnum));
 253
 254   return read_register (regnum);
 255 }
 256
 257 /* Function: skip_prologue
 258    Return the address of the first code past the prologue of the function.  */
 259
 260 CORE_ADDR
 261 v850_skip_prologue (pc)
 262      CORE_ADDR pc;
 263 {
 264   CORE_ADDR func_addr, func_end;
 265
 266   /* See what the symbol table says */
 267
 268   if (find_pc_partial_function (pc, NULL, &func_addr, &func_end))
 269     {
 270       struct symtab_and_line sal;
 271
 272       sal = find_pc_line (func_addr, 0);
 273
 274       if (sal.line != 0 && sal.end < func_end)
 275         return sal.end;
 276       else
 277         /* Either there's no line info, or the line after the prologue is after
 278            the end of the function.  In this case, there probably isn't a
 279            prologue.  */
 280         return pc;
 281     }
 282
 283 /* We can't find the start of this function, so there's nothing we can do. */
 284   return pc;
 285 }
 286
 287 /* Function: pop_frame
 288    This routine gets called when either the user uses the `return'
 289    command, or the call dummy breakpoint gets hit.  */
 290
 291 void
 292 v850_pop_frame (frame)
 293      struct frame_info *frame;
 294 {
 295   int regnum;
 296
 297   if (PC_IN_CALL_DUMMY(frame->pc, frame->frame, frame->frame))
 298     generic_pop_dummy_frame ();
 299   else
 300     {
 301       write_register (PC_REGNUM, FRAME_SAVED_PC (frame));
 302
 303       for (regnum = 0; regnum < NUM_REGS; regnum++)
 304         if (frame->fsr.regs[regnum] != 0)
 305           write_register (regnum,
 306                           read_memory_unsigned_integer (frame->fsr.regs[regnum],
 307                                                         REGISTER_RAW_SIZE(regnum)));
 308
 309       write_register (SP_REGNUM, FRAME_FP (frame));
 310     }
 311
 312   flush_cached_frames ();
 313 }
 314
 315 /* Function: push_arguments
 316    Setup arguments and RP for a call to the target.  First four args
 317    go in R6->R9, subsequent args go into sp + 16 -> sp + ...  Structs
 318    are passed by reference.  64 bit quantities (doubles and long
 319    longs) may be split between the regs and the stack.  When calling a
 320    function that returns a struct, a pointer to the struct is passed
 321    in as a secret first argument (always in R6).
 322
 323    Stack space for the args has NOT been allocated: that job is up to us.
 324    */
 325
 326 CORE_ADDR
 327 v850_push_arguments (nargs, args, sp, struct_return, struct_addr)
 328      int nargs;
 329      value_ptr *args;
 330      CORE_ADDR sp;
 331      unsigned char struct_return;
 332      CORE_ADDR struct_addr;
 333 {
 334   int argreg;
 335   int argnum;
 336   int len = 0;
 337   int stack_offset;
 338
 339   /* First, just for safety, make sure stack is aligned */
 340   sp &= ~3;
 341
 342   /* Now make space on the stack for the args. */
 343   for (argnum = 0; argnum < nargs; argnum++)
 344     len += ((TYPE_LENGTH(VALUE_TYPE(args[argnum])) + 3) & ~3);
 345   sp -= len;    /* possibly over-allocating, but it works... */
 346                 /* (you might think we could allocate 16 bytes */
 347                 /* less, but the ABI seems to use it all! )  */
 348   argreg = ARG0_REGNUM;
 349
 350   /* the struct_return pointer occupies the first parameter-passing reg */
 351   if (struct_return)
 352       write_register (argreg++, struct_addr);
 353
 354   stack_offset = 16;
 355   /* The offset onto the stack at which we will start copying parameters
 356      (after the registers are used up) begins at 16 rather than at zero.
 357      I don't really know why, that's just the way it seems to work.  */
 358
 359   /* Now load as many as possible of the first arguments into
 360      registers, and push the rest onto the stack.  There are 16 bytes
 361      in four registers available.  Loop thru args from first to last.  */
 362   for (argnum = 0; argnum < nargs; argnum++)
 363     {
 364       int len;
 365       char *val;
 366       char valbuf[REGISTER_RAW_SIZE(ARG0_REGNUM)];
 367
 368       if (TYPE_CODE (VALUE_TYPE (*args)) == TYPE_CODE_STRUCT
 369           && TYPE_LENGTH (VALUE_TYPE (*args)) > 8)
 370         {
 371           store_address (valbuf, 4, VALUE_ADDRESS (*args));
 372           len = 4;
 373           val = valbuf;
 374         }
 375       else
 376         {
 377           len = TYPE_LENGTH (VALUE_TYPE (*args));
 378           val = (char *)VALUE_CONTENTS (*args);
 379         }
 380
 381       while (len > 0)
 382         if  (argreg <= ARGLAST_REGNUM)
 383           {
 384             CORE_ADDR regval;
 385
 386             regval = extract_address (val, REGISTER_RAW_SIZE (argreg));
 387             write_register (argreg, regval);
 388
 389             len -= REGISTER_RAW_SIZE (argreg);
 390             val += REGISTER_RAW_SIZE (argreg);
 391             argreg++;
 392           }
 393         else
 394           {
 395             write_memory (sp + stack_offset, val, 4);
 396
 397             len -= 4;
 398             val += 4;
 399             stack_offset += 4;
 400           }
 401       args++;
 402     }
 403   return sp;
 404 }
 405
 406 /* Function: push_return_address (pc)
 407    Set up the return address for the inferior function call.
 408    Needed for targets where we don't actually execute a JSR/BSR instruction */
 409
 410 CORE_ADDR
 411 v850_push_return_address (pc, sp)
 412      CORE_ADDR pc;
 413      CORE_ADDR sp;
 414 {
 415   write_register (RP_REGNUM, CALL_DUMMY_ADDRESS ());
 416   return sp;
 417 }
 418
 419 /* Function: frame_saved_pc
 420    Find the caller of this frame.  We do this by seeing if RP_REGNUM
 421    is saved in the stack anywhere, otherwise we get it from the
 422    registers.  If the inner frame is a dummy frame, return its PC
 423    instead of RP, because that's where "caller" of the dummy-frame
 424    will be found.  */
 425
 426 CORE_ADDR
 427 v850_frame_saved_pc (fi)
 428      struct frame_info *fi;
 429 {
 430   if (PC_IN_CALL_DUMMY(fi->pc, fi->frame, fi->frame))
 431     return generic_read_register_dummy(fi->pc, fi->frame, PC_REGNUM);
 432   else
 433     return v850_find_callers_reg (fi, RP_REGNUM);
 434 }
 435
 436 void
 437 get_saved_register (raw_buffer, optimized, addrp, frame, regnum, lval)
 438      char *raw_buffer;
 439      int *optimized;
 440      CORE_ADDR *addrp;
 441      struct frame_info *frame;
 442      int regnum;
 443      enum lval_type *lval;
 444 {
 445   generic_get_saved_register (raw_buffer, optimized, addrp,
 446                               frame, regnum, lval);
 447 }
 448
 449
 450 /* Function: fix_call_dummy
 451    Pokes the callee function's address into the CALL_DUMMY assembly stub.
 452    Assumes that the CALL_DUMMY looks like this:
 453         jarl <offset24>, r31
 454         trap
 455    */
 456
 457 int
 458 v850_fix_call_dummy (dummy, sp, fun, nargs, args, type, gcc_p)
 459      char *dummy;
 460      CORE_ADDR sp;
 461      CORE_ADDR fun;
 462      int nargs;
 463      value_ptr *args;
 464      struct type *type;
 465      int gcc_p;
 466 {
 467   long offset24;
 468
 469   offset24 = (long) fun - (long) entry_point_address ();
 470   offset24 &= 0x3fffff;
 471   offset24 |= 0xff800000;       /* jarl <offset24>, r31 */
 472
 473   store_unsigned_integer ((unsigned int *)&dummy[2], 2, offset24 & 0xffff);
 474   store_unsigned_integer ((unsigned int *)&dummy[0], 2, offset24 >> 16);
 475   return 0;
 476 }
 477
 478 void
 479 _initialize_v850_tdep ()
 480 {
 481   tm_print_insn = print_insn_v850;
 482 }