gdb/dummy-frame.c

   1 /* Code dealing with dummy stack frames, for GDB, the GNU debugger.
   2
   3    Copyright 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994,
   4    1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002 Free Software
   5    Foundation, Inc.
   6
   7    This file is part of GDB.
   8
   9    This program is free software; you can redistribute it and/or modify
  10    it under the terms of the GNU General Public License as published by
  11    the Free Software Foundation; either version 2 of the License, or
  12    (at your option) any later version.
  13
  14    This program is distributed in the hope that it will be useful,
  15    but WITHOUT ANY WARRANTY; without even the implied warranty of
  16    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17    GNU General Public License for more details.
  18
  19    You should have received a copy of the GNU General Public License
  20    along with this program; if not, write to the Free Software
  21    Foundation, Inc., 59 Temple Place - Suite 330,
  22    Boston, MA 02111-1307, USA.  */
  23
  24
  25 #include "defs.h"
  26 #include "dummy-frame.h"
  27 #include "regcache.h"
  28 #include "frame.h"
  29 #include "inferior.h"
  30 #include "gdb_assert.h"
  31
  32 /* Dummy frame.  This saves the processor state just prior to setting
  33    up the inferior function call.  Older targets save the registers
  34    on the target stack (but that really slows down function calls).  */
  35
  36 struct dummy_frame
  37 {
  38   struct dummy_frame *next;
  39
  40   /* These values belong to the caller (the previous frame, the frame
  41      that this unwinds back to).  */
  42   CORE_ADDR pc;
  43   CORE_ADDR fp;
  44   CORE_ADDR sp;
  45   CORE_ADDR top;
  46   struct frame_id id;
  47   struct regcache *regcache;
  48
  49   /* Address range of the call dummy code.  Look for PC in the range
  50      [LO..HI) (after allowing for DECR_PC_AFTER_BREAK).  */
  51   CORE_ADDR call_lo;
  52   CORE_ADDR call_hi;
  53 };
  54
  55 static struct dummy_frame *dummy_frame_stack = NULL;
  56
  57 /* Function: find_dummy_frame(pc, fp, sp)
  58
  59    Search the stack of dummy frames for one matching the given PC and
  60    FP/SP.  Unlike pc_in_dummy_frame(), this function doesn't need to
  61    adjust for DECR_PC_AFTER_BREAK.  This is because it is only legal
  62    to call this function after the PC has been adjusted.  */
  63
  64 static struct dummy_frame *
  65 find_dummy_frame (CORE_ADDR pc, CORE_ADDR fp)
  66 {
  67   struct dummy_frame *dummyframe;
  68
  69   for (dummyframe = dummy_frame_stack; dummyframe != NULL;
  70        dummyframe = dummyframe->next)
  71     {
  72       /* Does the PC fall within the dummy frame's breakpoint
  73          instruction.  If not, discard this one.  */
  74       if (!(pc >= dummyframe->call_lo && pc < dummyframe->call_hi))
  75         continue;
  76       /* Does the FP match?  */
  77       if (dummyframe->top != 0)
  78         {
  79           /* If the target architecture explicitly saved the
  80              top-of-stack before the inferior function call, assume
  81              that that same architecture will always pass in an FP
  82              (frame base) value that eactly matches that saved TOS.
  83              Don't check the saved SP and SP as they can lead to false
  84              hits.  */
  85           if (fp != dummyframe->top)
  86             continue;
  87         }
  88       else
  89         {
  90           /* An older target that hasn't explicitly or implicitly
  91              saved the dummy frame's top-of-stack.  Try matching the
  92              FP against the saved SP and FP.  NOTE: If you're trying
  93              to fix a problem with GDB not correctly finding a dummy
  94              frame, check the comments that go with FRAME_ALIGN() and
  95              SAVE_DUMMY_FRAME_TOS().  */
  96           if (fp != dummyframe->fp && fp != dummyframe->sp)
  97             continue;
  98         }
  99       /* The FP matches this dummy frame.  */
 100       return dummyframe;
 101     }
 102
 103   return NULL;
 104 }
 105
 106 struct dummy_frame *
 107 cached_find_dummy_frame (struct frame_info *frame, void **cache)
 108 {
 109   if ((*cache) == NULL)
 110     (*cache) = find_dummy_frame (get_frame_pc (frame), get_frame_base (frame));
 111   return (*cache);
 112 }
 113
 114 struct regcache *
 115 generic_find_dummy_frame (CORE_ADDR pc, CORE_ADDR fp)
 116 {
 117   struct dummy_frame *dummy = find_dummy_frame (pc, fp);
 118   if (dummy != NULL)
 119     return dummy->regcache;
 120   else
 121     return NULL;
 122 }
 123
 124 char *
 125 deprecated_generic_find_dummy_frame (CORE_ADDR pc, CORE_ADDR fp)
 126 {
 127   struct regcache *regcache = generic_find_dummy_frame (pc, fp);
 128   if (regcache == NULL)
 129     return NULL;
 130   return deprecated_grub_regcache_for_registers (regcache);
 131 }
 132
 133 /* Function: pc_in_call_dummy (pc, sp, fp)
 134
 135    Return true if the PC falls in a dummy frame created by gdb for an
 136    inferior call.  The code below which allows DECR_PC_AFTER_BREAK is
 137    for infrun.c, which may give the function a PC without that
 138    subtracted out.  */
 139
 140 int
 141 generic_pc_in_call_dummy (CORE_ADDR pc, CORE_ADDR sp, CORE_ADDR fp)
 142 {
 143   return pc_in_dummy_frame (pc);
 144 }
 145
 146 /* Return non-zero if the PC falls in a dummy frame.
 147
 148    The code below which allows DECR_PC_AFTER_BREAK is for infrun.c,
 149    which may give the function a PC without that subtracted out.
 150
 151    FIXME: cagney/2002-11-23: This is silly.  Surely "infrun.c" can
 152    figure out what the real PC (as in the resume address) is BEFORE
 153    calling this function (Oh, and I'm not even sure that this function
 154    is called with an decremented PC, the call to pc_in_call_dummy() in
 155    that file is conditional on !CALL_DUMMY_BREAKPOINT_OFFSET_P yet
 156    generic dummy targets set CALL_DUMMY_BREAKPOINT_OFFSET. True?).  */
 157
 158 int
 159 pc_in_dummy_frame (CORE_ADDR pc)
 160 {
 161   struct dummy_frame *dummyframe;
 162   for (dummyframe = dummy_frame_stack;
 163        dummyframe != NULL;
 164        dummyframe = dummyframe->next)
 165     {
 166       if ((pc >= dummyframe->call_lo)
 167           && (pc < dummyframe->call_hi + DECR_PC_AFTER_BREAK))
 168         return 1;
 169     }
 170   return 0;
 171 }
 172
 173 /* Function: read_register_dummy
 174    Find a saved register from before GDB calls a function in the inferior */
 175
 176 CORE_ADDR
 177 deprecated_read_register_dummy (CORE_ADDR pc, CORE_ADDR fp, int regno)
 178 {
 179   struct regcache *dummy_regs = generic_find_dummy_frame (pc, fp);
 180
 181   if (dummy_regs)
 182     {
 183       /* NOTE: cagney/2002-08-12: Replaced a call to
 184          regcache_raw_read_as_address() with a call to
 185          regcache_cooked_read_unsigned().  The old, ...as_address
 186          function was eventually calling extract_unsigned_integer (via
 187          extract_address) to unpack the registers value.  The below is
 188          doing an unsigned extract so that it is functionally
 189          equivalent.  The read needs to be cooked as, otherwise, it
 190          will never correctly return the value of a register in the
 191          [NUM_REGS .. NUM_REGS+NUM_PSEUDO_REGS) range.  */
 192       ULONGEST val;
 193       regcache_cooked_read_unsigned (dummy_regs, regno, &val);
 194       return val;
 195     }
 196   else
 197     return 0;
 198 }
 199
 200 /* Save all the registers on the dummy frame stack.  Most ports save the
 201    registers on the target stack.  This results in lots of unnecessary memory
 202    references, which are slow when debugging via a serial line.  Instead, we
 203    save all the registers internally, and never write them to the stack.  The
 204    registers get restored when the called function returns to the entry point,
 205    where a breakpoint is laying in wait.  */
 206
 207 void
 208 generic_push_dummy_frame (void)
 209 {
 210   struct dummy_frame *dummy_frame;
 211   CORE_ADDR fp = get_frame_base (get_current_frame ());
 212
 213   /* check to see if there are stale dummy frames,
 214      perhaps left over from when a longjump took us out of a
 215      function that was called by the debugger */
 216
 217   dummy_frame = dummy_frame_stack;
 218   while (dummy_frame)
 219     if (INNER_THAN (dummy_frame->fp, fp))       /* stale -- destroy! */
 220       {
 221         dummy_frame_stack = dummy_frame->next;
 222         regcache_xfree (dummy_frame->regcache);
 223         xfree (dummy_frame);
 224         dummy_frame = dummy_frame_stack;
 225       }
 226     else
 227       dummy_frame = dummy_frame->next;
 228
 229   dummy_frame = xmalloc (sizeof (struct dummy_frame));
 230   dummy_frame->regcache = regcache_xmalloc (current_gdbarch);
 231
 232   dummy_frame->pc = read_pc ();
 233   dummy_frame->sp = read_sp ();
 234   dummy_frame->top = 0;
 235   dummy_frame->fp = fp;
 236   dummy_frame->id = get_frame_id (get_current_frame ());
 237   regcache_cpy (dummy_frame->regcache, current_regcache);
 238   dummy_frame->next = dummy_frame_stack;
 239   dummy_frame_stack = dummy_frame;
 240 }
 241
 242 void
 243 generic_save_dummy_frame_tos (CORE_ADDR sp)
 244 {
 245   dummy_frame_stack->top = sp;
 246 }
 247
 248 /* Record the upper/lower bounds on the address of the call dummy.  */
 249
 250 void
 251 generic_save_call_dummy_addr (CORE_ADDR lo, CORE_ADDR hi)
 252 {
 253   dummy_frame_stack->call_lo = lo;
 254   dummy_frame_stack->call_hi = hi;
 255 }
 256
 257 /* Restore the machine state from either the saved dummy stack or a
 258    real stack frame. */
 259
 260 void
 261 generic_pop_current_frame (void (*popper) (struct frame_info * frame))
 262 {
 263   struct frame_info *frame = get_current_frame ();
 264   if (get_frame_type (frame) == DUMMY_FRAME)
 265     /* NOTE: cagney/2002-22-23: Does this ever occure?  Surely a dummy
 266        frame will have already been poped by the "infrun.c" code.  */
 267     generic_pop_dummy_frame ();
 268   else
 269     (*popper) (frame);
 270 }
 271
 272 /* Function: pop_dummy_frame
 273    Restore the machine state from a saved dummy stack frame. */
 274
 275 void
 276 generic_pop_dummy_frame (void)
 277 {
 278   struct dummy_frame *dummy_frame = dummy_frame_stack;
 279
 280   /* FIXME: what if the first frame isn't the right one, eg..
 281      because one call-by-hand function has done a longjmp into another one? */
 282
 283   if (!dummy_frame)
 284     error ("Can't pop dummy frame!");
 285   dummy_frame_stack = dummy_frame->next;
 286   regcache_cpy (current_regcache, dummy_frame->regcache);
 287   flush_cached_frames ();
 288
 289   regcache_xfree (dummy_frame->regcache);
 290   xfree (dummy_frame);
 291 }
 292
 293 /* Function: fix_call_dummy
 294    Stub function.  Generic dummy frames typically do not need to fix
 295    the frame being created */
 296
 297 void
 298 generic_fix_call_dummy (char *dummy, CORE_ADDR pc, CORE_ADDR fun, int nargs,
 299                         struct value **args, struct type *type, int gcc_p)
 300 {
 301   return;
 302 }
 303
 304 /* Given a call-dummy dummy-frame, return the registers.  Here the
 305    register value is taken from the local copy of the register buffer.  */
 306
 307 void
 308 dummy_frame_register_unwind (struct frame_info *frame, void **cache,
 309                              int regnum, int *optimized,
 310                              enum lval_type *lvalp, CORE_ADDR *addrp,
 311                              int *realnum, void *bufferp)
 312 {
 313   struct dummy_frame *dummy = cached_find_dummy_frame (frame, cache);
 314   gdb_assert (dummy != NULL);
 315
 316   /* Describe the register's location.  Generic dummy frames always
 317      have the register value in an ``expression''.  */
 318   *optimized = 0;
 319   *lvalp = not_lval;
 320   *addrp = 0;
 321   *realnum = -1;
 322
 323   /* If needed, find and return the value of the register.  */
 324   if (bufferp != NULL)
 325     {
 326       /* Return the actual value.  */
 327       /* Use the regcache_cooked_read() method so that it, on the fly,
 328          constructs either a raw or pseudo register from the raw
 329          register cache.  */
 330       regcache_cooked_read (dummy->regcache, regnum, bufferp);
 331     }
 332 }
 333
 334 CORE_ADDR
 335 dummy_frame_pc_unwind (struct frame_info *frame,
 336                        void **cache)
 337 {
 338   struct dummy_frame *dummy = cached_find_dummy_frame (frame, cache);
 339   /* Oops!  In a dummy-frame but can't find the stack dummy.  Pretend
 340      that the frame doesn't unwind.  Should this function instead
 341      return a has-no-caller indication?  */
 342   if (dummy == NULL)
 343     return 0;
 344   return dummy->pc;
 345 }
 346
 347
 348 void
 349 dummy_frame_id_unwind (struct frame_info *frame, void **cache,
 350                        struct frame_id *id)
 351 {
 352   struct dummy_frame *dummy = cached_find_dummy_frame (frame, cache);
 353   /* Oops!  In a dummy-frame but can't find the stack dummy.  Pretend
 354      that the frame doesn't unwind.  Should this function instead
 355      return a has-no-caller indication?  */
 356   if (dummy == NULL)
 357     (*id) = null_frame_id;
 358   else
 359     (*id) = dummy->id;
 360 }
 361