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 #include "frame-unwind.h"
  32 #include "command.h"
  33 #include "gdbcmd.h"
  34
  35 static void dummy_frame_this_id (struct frame_info *next_frame,
  36                                  void **this_prologue_cache,
  37                                  struct frame_id *this_id);
  38
  39 /* Dummy frame.  This saves the processor state just prior to setting
  40    up the inferior function call.  Older targets save the registers
  41    on the target stack (but that really slows down function calls).  */
  42
  43 struct dummy_frame
  44 {
  45   struct dummy_frame *next;
  46
  47   /* These values belong to the caller (the previous frame, the frame
  48      that this unwinds back to).  */
  49   CORE_ADDR pc;
  50   CORE_ADDR fp;
  51   CORE_ADDR sp;
  52   CORE_ADDR top;
  53   struct frame_id id;
  54   struct regcache *regcache;
  55
  56   /* Address range of the call dummy code.  Look for PC in the range
  57      [LO..HI) (after allowing for DECR_PC_AFTER_BREAK).  */
  58   CORE_ADDR call_lo;
  59   CORE_ADDR call_hi;
  60 };
  61
  62 static struct dummy_frame *dummy_frame_stack = NULL;
  63
  64 /* Function: find_dummy_frame(pc, fp, sp)
  65
  66    Search the stack of dummy frames for one matching the given PC and
  67    FP/SP.  Unlike pc_in_dummy_frame(), this function doesn't need to
  68    adjust for DECR_PC_AFTER_BREAK.  This is because it is only legal
  69    to call this function after the PC has been adjusted.  */
  70
  71 static struct dummy_frame *
  72 find_dummy_frame (CORE_ADDR pc, CORE_ADDR fp)
  73 {
  74   struct dummy_frame *dummyframe;
  75
  76   for (dummyframe = dummy_frame_stack; dummyframe != NULL;
  77        dummyframe = dummyframe->next)
  78     {
  79       /* Does the PC fall within the dummy frame's breakpoint
  80          instruction.  If not, discard this one.  */
  81       if (!(pc >= dummyframe->call_lo && pc < dummyframe->call_hi))
  82         continue;
  83       /* Does the FP match?  */
  84       if (dummyframe->top != 0)
  85         {
  86           /* If the target architecture explicitly saved the
  87              top-of-stack before the inferior function call, assume
  88              that that same architecture will always pass in an FP
  89              (frame base) value that eactly matches that saved TOS.
  90              Don't check the saved SP and SP as they can lead to false
  91              hits.  */
  92           if (fp != dummyframe->top)
  93             continue;
  94         }
  95       else
  96         {
  97           /* An older target that hasn't explicitly or implicitly
  98              saved the dummy frame's top-of-stack.  Try matching the
  99              FP against the saved SP and FP.  NOTE: If you're trying
 100              to fix a problem with GDB not correctly finding a dummy
 101              frame, check the comments that go with FRAME_ALIGN() and
 102              UNWIND_DUMMY_ID().  */
 103           if (fp != dummyframe->fp && fp != dummyframe->sp)
 104             continue;
 105         }
 106       /* The FP matches this dummy frame.  */
 107       return dummyframe;
 108     }
 109
 110   return NULL;
 111 }
 112
 113 struct regcache *
 114 deprecated_find_dummy_frame_regcache (CORE_ADDR pc, CORE_ADDR fp)
 115 {
 116   struct dummy_frame *dummy = find_dummy_frame (pc, fp);
 117   if (dummy != NULL)
 118     return dummy->regcache;
 119   else
 120     return NULL;
 121 }
 122
 123 char *
 124 deprecated_generic_find_dummy_frame (CORE_ADDR pc, CORE_ADDR fp)
 125 {
 126   struct regcache *regcache = deprecated_find_dummy_frame_regcache (pc, fp);
 127   if (regcache == NULL)
 128     return NULL;
 129   return deprecated_grub_regcache_for_registers (regcache);
 130 }
 131
 132 /* Function: pc_in_call_dummy (pc, sp, fp)
 133
 134    Return true if the PC falls in a dummy frame created by gdb for an
 135    inferior call.  The code below which allows DECR_PC_AFTER_BREAK is
 136    for infrun.c, which may give the function a PC without that
 137    subtracted out.  */
 138
 139 int
 140 generic_pc_in_call_dummy (CORE_ADDR pc, CORE_ADDR sp, CORE_ADDR fp)
 141 {
 142   return pc_in_dummy_frame (pc);
 143 }
 144
 145 /* Return non-zero if the PC falls in a dummy frame.
 146
 147    The code below which allows DECR_PC_AFTER_BREAK is for infrun.c,
 148    which may give the function a PC without that subtracted out.
 149
 150    FIXME: cagney/2002-11-23: This is silly.  Surely "infrun.c" can
 151    figure out what the real PC (as in the resume address) is BEFORE
 152    calling this function (Oh, and I'm not even sure that this function
 153    is called with an decremented PC, the call to pc_in_call_dummy() in
 154    that file is conditional on
 155    !DEPRECATED_CALL_DUMMY_BREAKPOINT_OFFSET_P yet generic dummy
 156    targets set DEPRECATED_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 = deprecated_find_dummy_frame_regcache (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 (nee
 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 /* Discard the innermost dummy frame from the dummy frame stack
 273    (passed in as a parameter).  */
 274
 275 static void
 276 discard_innermost_dummy (struct dummy_frame **stack)
 277 {
 278   struct dummy_frame *tbd = (*stack);
 279   (*stack) = (*stack)->next;
 280   regcache_xfree (tbd->regcache);
 281   xfree (tbd);
 282 }
 283
 284 void
 285 generic_pop_dummy_frame (void)
 286 {
 287   struct dummy_frame *dummy_frame = dummy_frame_stack;
 288
 289   /* FIXME: what if the first frame isn't the right one, eg..
 290      because one call-by-hand function has done a longjmp into another one? */
 291
 292   if (!dummy_frame)
 293     error ("Can't pop dummy frame!");
 294   regcache_cpy (current_regcache, dummy_frame->regcache);
 295   flush_cached_frames ();
 296
 297   discard_innermost_dummy (&dummy_frame_stack);
 298 }
 299
 300 /* Given a call-dummy dummy-frame, return the registers.  Here the
 301    register value is taken from the local copy of the register buffer.  */
 302
 303 static void
 304 dummy_frame_prev_register (struct frame_info *next_frame,
 305                            void **this_prologue_cache,
 306                            int regnum, int *optimized,
 307                            enum lval_type *lvalp, CORE_ADDR *addrp,
 308                            int *realnum, void *bufferp)
 309 {
 310   struct dummy_frame *dummy;
 311   struct frame_id id;
 312
 313   /* Call the ID method which, if at all possible, will set the
 314      prologue cache.  */
 315   dummy_frame_this_id (next_frame, this_prologue_cache, &id);
 316   dummy = (*this_prologue_cache);
 317   gdb_assert (dummy != NULL);
 318
 319   /* Describe the register's location.  Generic dummy frames always
 320      have the register value in an ``expression''.  */
 321   *optimized = 0;
 322   *lvalp = not_lval;
 323   *addrp = 0;
 324   *realnum = -1;
 325
 326   /* If needed, find and return the value of the register.  */
 327   if (bufferp != NULL)
 328     {
 329       /* Return the actual value.  */
 330       /* Use the regcache_cooked_read() method so that it, on the fly,
 331          constructs either a raw or pseudo register from the raw
 332          register cache.  */
 333       regcache_cooked_read (dummy->regcache, regnum, bufferp);
 334     }
 335 }
 336
 337 /* Assuming that THIS frame is a dummy (remember, the NEXT and not
 338    THIS frame is passed in), return the ID of THIS frame.  That ID is
 339    determined by examining the NEXT frame's unwound registers using
 340    the method unwind_dummy_id().  As a side effect, THIS dummy frame's
 341    dummy cache is located and and saved in THIS_PROLOGUE_CACHE.  */
 342
 343 static void
 344 dummy_frame_this_id (struct frame_info *next_frame,
 345                      void **this_prologue_cache,
 346                      struct frame_id *this_id)
 347 {
 348   struct dummy_frame *dummy = (*this_prologue_cache);
 349   if (dummy != NULL)
 350     {
 351       (*this_id) = dummy->id;
 352       return;
 353     }
 354   /* When unwinding a normal frame, the stack structure is determined
 355      by analyzing the frame's function's code (be it using brute force
 356      prologue analysis, or the dwarf2 CFI).  In the case of a dummy
 357      frame, that simply isn't possible.  The The PC is either the
 358      program entry point, or some random address on the stack.  Trying
 359      to use that PC to apply standard frame ID unwind techniques is
 360      just asking for trouble.  */
 361   if (gdbarch_unwind_dummy_id_p (current_gdbarch))
 362     {
 363       /* Use an architecture specific method to extract the prev's
 364          dummy ID from the next frame.  Note that this method uses
 365          frame_register_unwind to obtain the register values needed to
 366          determine the dummy frame's ID.  */
 367       (*this_id) = gdbarch_unwind_dummy_id (current_gdbarch, next_frame);
 368     }
 369   else if (frame_relative_level (next_frame) < 0)
 370     {
 371       /* We're unwinding a sentinel frame, the PC of which is pointing
 372          at a stack dummy.  Fake up the dummy frame's ID using the
 373          same sequence as is found a traditional unwinder.  Once all
 374          architectures supply the unwind_dummy_id method, this code
 375          can go away.  */
 376       (*this_id) = frame_id_build (deprecated_read_fp (), read_pc ());
 377     }
 378   else if (legacy_frame_p (current_gdbarch)
 379            && get_prev_frame (next_frame))
 380     {
 381       /* Things are looking seriously grim!  Assume that the legacy
 382          get_prev_frame code has already created THIS frame and linked
 383          it in to the frame chain (a pretty bold assumption), extract
 384          the ID from THIS base / pc.  */
 385       (*this_id) = frame_id_build (get_frame_base (get_prev_frame (next_frame)),
 386                                    get_frame_pc (get_prev_frame (next_frame)));
 387     }
 388   else
 389     {
 390       /* Outch!  We're not trying to find the innermost frame's ID yet
 391          we're trying to unwind to a dummy.  The architecture must
 392          provide the unwind_dummy_id() method.  Abandon the unwind
 393          process but only after first warning the user.  */
 394       internal_warning (__FILE__, __LINE__,
 395                         "Missing unwind_dummy_id architecture method");
 396       (*this_id) = null_frame_id;
 397       return;
 398     }
 399   (*this_prologue_cache) = find_dummy_frame ((*this_id).code_addr,
 400                                              (*this_id).stack_addr);
 401 }
 402
 403 static struct frame_unwind dummy_frame_unwind =
 404 {
 405   DUMMY_FRAME,
 406   dummy_frame_this_id,
 407   dummy_frame_prev_register
 408 };
 409
 410 const struct frame_unwind *
 411 dummy_frame_sniffer (struct frame_info *next_frame)
 412 {
 413   CORE_ADDR pc = frame_pc_unwind (next_frame);
 414   if (DEPRECATED_PC_IN_CALL_DUMMY_P ()
 415       ? DEPRECATED_PC_IN_CALL_DUMMY (pc, 0, 0)
 416       : pc_in_dummy_frame (pc))
 417     return &dummy_frame_unwind;
 418   else
 419     return NULL;
 420 }
 421
 422 static void
 423 fprint_dummy_frames (struct ui_file *file)
 424 {
 425   struct dummy_frame *s;
 426   for (s = dummy_frame_stack; s != NULL; s = s->next)
 427     {
 428       gdb_print_host_address (s, file);
 429       fprintf_unfiltered (file, ":");
 430       fprintf_unfiltered (file, " pc=0x%s", paddr (s->pc));
 431       fprintf_unfiltered (file, " fp=0x%s", paddr (s->fp));
 432       fprintf_unfiltered (file, " sp=0x%s", paddr (s->sp));
 433       fprintf_unfiltered (file, " top=0x%s", paddr (s->top));
 434       fprintf_unfiltered (file, " id=");
 435       fprint_frame_id (file, s->id);
 436       fprintf_unfiltered (file, " call_lo=0x%s", paddr (s->call_lo));
 437       fprintf_unfiltered (file, " call_hi=0x%s", paddr (s->call_hi));
 438       fprintf_unfiltered (file, "\n");
 439     }
 440 }
 441
 442 static void
 443 maintenance_print_dummy_frames (char *args, int from_tty)
 444 {
 445   if (args == NULL)
 446     fprint_dummy_frames (gdb_stdout);
 447   else
 448     {
 449       struct ui_file *file = gdb_fopen (args, "w");
 450       if (file == NULL)
 451         perror_with_name ("maintenance print dummy-frames");
 452       fprint_dummy_frames (file);
 453       ui_file_delete (file);
 454     }
 455 }
 456
 457 extern void _initialize_dummy_frame (void);
 458
 459 void
 460 _initialize_dummy_frame (void)
 461 {
 462   add_cmd ("dummy-frames", class_maintenance, maintenance_print_dummy_frames,
 463            "Print the contents of the internal dummy-frame stack.",
 464            &maintenanceprintlist);
 465
 466 }