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 static int pc_in_dummy_frame (CORE_ADDR pc);
  40
  41 /* Dummy frame.  This saves the processor state just prior to setting
  42    up the inferior function call.  Older targets save the registers
  43    on the target stack (but that really slows down function calls).  */
  44
  45 struct dummy_frame
  46 {
  47   struct dummy_frame *next;
  48
  49   /* These values belong to the caller (the previous frame, the frame
  50      that this unwinds back to).  */
  51   CORE_ADDR pc;
  52   CORE_ADDR fp;
  53   CORE_ADDR sp;
  54   CORE_ADDR top;
  55   struct frame_id id;
  56   struct regcache *regcache;
  57
  58   /* Address range of the call dummy code.  Look for PC in the range
  59      [LO..HI) (after allowing for DECR_PC_AFTER_BREAK).  */
  60   CORE_ADDR call_lo;
  61   CORE_ADDR call_hi;
  62 };
  63
  64 static struct dummy_frame *dummy_frame_stack = NULL;
  65
  66 /* Function: find_dummy_frame(pc, fp, sp)
  67
  68    Search the stack of dummy frames for one matching the given PC and
  69    FP/SP.  Unlike pc_in_dummy_frame(), this function doesn't need to
  70    adjust for DECR_PC_AFTER_BREAK.  This is because it is only legal
  71    to call this function after the PC has been adjusted.  */
  72
  73 static struct dummy_frame *
  74 find_dummy_frame (CORE_ADDR pc, CORE_ADDR fp)
  75 {
  76   struct dummy_frame *dummyframe;
  77
  78   for (dummyframe = dummy_frame_stack; dummyframe != NULL;
  79        dummyframe = dummyframe->next)
  80     {
  81       /* Does the PC fall within the dummy frame's breakpoint
  82          instruction.  If not, discard this one.  */
  83       if (!(pc >= dummyframe->call_lo && pc < dummyframe->call_hi))
  84         continue;
  85       /* Does the FP match?  */
  86       if (dummyframe->top != 0)
  87         {
  88           /* If the target architecture explicitly saved the
  89              top-of-stack before the inferior function call, assume
  90              that that same architecture will always pass in an FP
  91              (frame base) value that eactly matches that saved TOS.
  92              Don't check the saved SP and SP as they can lead to false
  93              hits.  */
  94           if (fp != dummyframe->top)
  95             continue;
  96         }
  97       else
  98         {
  99           /* An older target that hasn't explicitly or implicitly
 100              saved the dummy frame's top-of-stack.  Try matching the
 101              FP against the saved SP and FP.  NOTE: If you're trying
 102              to fix a problem with GDB not correctly finding a dummy
 103              frame, check the comments that go with FRAME_ALIGN() and
 104              UNWIND_DUMMY_ID().  */
 105           if (fp != dummyframe->fp && fp != dummyframe->sp)
 106             continue;
 107         }
 108       /* The FP matches this dummy frame.  */
 109       return dummyframe;
 110     }
 111
 112   return NULL;
 113 }
 114
 115 struct regcache *
 116 deprecated_find_dummy_frame_regcache (CORE_ADDR pc, CORE_ADDR fp)
 117 {
 118   struct dummy_frame *dummy = find_dummy_frame (pc, fp);
 119   if (dummy != NULL)
 120     return dummy->regcache;
 121   else
 122     return NULL;
 123 }
 124
 125 char *
 126 deprecated_generic_find_dummy_frame (CORE_ADDR pc, CORE_ADDR fp)
 127 {
 128   struct regcache *regcache = deprecated_find_dummy_frame_regcache (pc, fp);
 129   if (regcache == NULL)
 130     return NULL;
 131   return deprecated_grub_regcache_for_registers (regcache);
 132 }
 133
 134 /* Function: pc_in_call_dummy (pc, sp, fp)
 135
 136    Return true if the PC falls in a dummy frame created by gdb for an
 137    inferior call.  The code below which allows DECR_PC_AFTER_BREAK is
 138    for infrun.c, which may give the function a PC without that
 139    subtracted out.  */
 140
 141 int
 142 deprecated_pc_in_call_dummy (CORE_ADDR pc, CORE_ADDR sp, CORE_ADDR fp)
 143 {
 144   return pc_in_dummy_frame (pc);
 145 }
 146
 147 /* Return non-zero if the PC falls in a dummy frame.
 148
 149    The code below which allows DECR_PC_AFTER_BREAK is for infrun.c,
 150    which may give the function a PC without that subtracted out.
 151
 152    FIXME: cagney/2002-11-23: This is silly.  Surely "infrun.c" can
 153    figure out what the real PC (as in the resume address) is BEFORE
 154    calling this function (Oh, and I'm not even sure that this function
 155    is called with an decremented PC, the call to pc_in_call_dummy() in
 156    that file is conditional on
 157    !DEPRECATED_CALL_DUMMY_BREAKPOINT_OFFSET_P yet generic dummy
 158    targets set DEPRECATED_CALL_DUMMY_BREAKPOINT_OFFSET. True?).  */
 159
 160 static int
 161 pc_in_dummy_frame (CORE_ADDR pc)
 162 {
 163   struct dummy_frame *dummyframe;
 164   for (dummyframe = dummy_frame_stack;
 165        dummyframe != NULL;
 166        dummyframe = dummyframe->next)
 167     {
 168       if ((pc >= dummyframe->call_lo)
 169           && (pc < dummyframe->call_hi + DECR_PC_AFTER_BREAK))
 170         return 1;
 171     }
 172   return 0;
 173 }
 174
 175 /* Function: read_register_dummy
 176    Find a saved register from before GDB calls a function in the inferior */
 177
 178 CORE_ADDR
 179 deprecated_read_register_dummy (CORE_ADDR pc, CORE_ADDR fp, int regno)
 180 {
 181   struct regcache *dummy_regs = deprecated_find_dummy_frame_regcache (pc, fp);
 182
 183   if (dummy_regs)
 184     {
 185       /* NOTE: cagney/2002-08-12: Replaced a call to
 186          regcache_raw_read_as_address() with a call to
 187          regcache_cooked_read_unsigned().  The old, ...as_address
 188          function was eventually calling extract_unsigned_integer (nee
 189          extract_address) to unpack the registers value.  The below is
 190          doing an unsigned extract so that it is functionally
 191          equivalent.  The read needs to be cooked as, otherwise, it
 192          will never correctly return the value of a register in the
 193          [NUM_REGS .. NUM_REGS+NUM_PSEUDO_REGS) range.  */
 194       ULONGEST val;
 195       regcache_cooked_read_unsigned (dummy_regs, regno, &val);
 196       return val;
 197     }
 198   else
 199     return 0;
 200 }
 201
 202 /* Save all the registers on the dummy frame stack.  Most ports save the
 203    registers on the target stack.  This results in lots of unnecessary memory
 204    references, which are slow when debugging via a serial line.  Instead, we
 205    save all the registers internally, and never write them to the stack.  The
 206    registers get restored when the called function returns to the entry point,
 207    where a breakpoint is laying in wait.  */
 208
 209 void
 210 generic_push_dummy_frame (void)
 211 {
 212   struct dummy_frame *dummy_frame;
 213   CORE_ADDR fp = get_frame_base (get_current_frame ());
 214
 215   /* check to see if there are stale dummy frames,
 216      perhaps left over from when a longjump took us out of a
 217      function that was called by the debugger */
 218
 219   dummy_frame = dummy_frame_stack;
 220   while (dummy_frame)
 221     if (INNER_THAN (dummy_frame->fp, fp))       /* stale -- destroy! */
 222       {
 223         dummy_frame_stack = dummy_frame->next;
 224         regcache_xfree (dummy_frame->regcache);
 225         xfree (dummy_frame);
 226         dummy_frame = dummy_frame_stack;
 227       }
 228     else
 229       dummy_frame = dummy_frame->next;
 230
 231   dummy_frame = xmalloc (sizeof (struct dummy_frame));
 232   dummy_frame->regcache = regcache_xmalloc (current_gdbarch);
 233
 234   dummy_frame->pc = read_pc ();
 235   dummy_frame->sp = read_sp ();
 236   dummy_frame->top = 0;
 237   dummy_frame->fp = fp;
 238   dummy_frame->id = get_frame_id (get_current_frame ());
 239   regcache_cpy (dummy_frame->regcache, current_regcache);
 240   dummy_frame->next = dummy_frame_stack;
 241   dummy_frame_stack = dummy_frame;
 242 }
 243
 244 void
 245 generic_save_dummy_frame_tos (CORE_ADDR sp)
 246 {
 247   dummy_frame_stack->top = sp;
 248 }
 249
 250 /* Record the upper/lower bounds on the address of the call dummy.  */
 251
 252 void
 253 generic_save_call_dummy_addr (CORE_ADDR lo, CORE_ADDR hi)
 254 {
 255   dummy_frame_stack->call_lo = lo;
 256   dummy_frame_stack->call_hi = hi;
 257 }
 258
 259 /* Restore the machine state from either the saved dummy stack or a
 260    real stack frame. */
 261
 262 void
 263 generic_pop_current_frame (void (*popper) (struct frame_info * frame))
 264 {
 265   struct frame_info *frame = get_current_frame ();
 266   if (get_frame_type (frame) == DUMMY_FRAME)
 267     /* NOTE: cagney/2002-22-23: Does this ever occure?  Surely a dummy
 268        frame will have already been poped by the "infrun.c" code.  */
 269     generic_pop_dummy_frame ();
 270   else
 271     (*popper) (frame);
 272 }
 273
 274 /* Discard the innermost dummy frame from the dummy frame stack
 275    (passed in as a parameter).  */
 276
 277 static void
 278 discard_innermost_dummy (struct dummy_frame **stack)
 279 {
 280   struct dummy_frame *tbd = (*stack);
 281   (*stack) = (*stack)->next;
 282   regcache_xfree (tbd->regcache);
 283   xfree (tbd);
 284 }
 285
 286 void
 287 generic_pop_dummy_frame (void)
 288 {
 289   struct dummy_frame *dummy_frame = dummy_frame_stack;
 290
 291   /* FIXME: what if the first frame isn't the right one, eg..
 292      because one call-by-hand function has done a longjmp into another one? */
 293
 294   if (!dummy_frame)
 295     error ("Can't pop dummy frame!");
 296   regcache_cpy (current_regcache, dummy_frame->regcache);
 297   flush_cached_frames ();
 298
 299   discard_innermost_dummy (&dummy_frame_stack);
 300 }
 301
 302 /* Given a call-dummy dummy-frame, return the registers.  Here the
 303    register value is taken from the local copy of the register buffer.  */
 304
 305 static void
 306 dummy_frame_prev_register (struct frame_info *next_frame,
 307                            void **this_prologue_cache,
 308                            int regnum, int *optimized,
 309                            enum lval_type *lvalp, CORE_ADDR *addrp,
 310                            int *realnum, void *bufferp)
 311 {
 312   struct dummy_frame *dummy;
 313   struct frame_id id;
 314
 315   /* Call the ID method which, if at all possible, will set the
 316      prologue cache.  */
 317   dummy_frame_this_id (next_frame, this_prologue_cache, &id);
 318   dummy = (*this_prologue_cache);
 319   gdb_assert (dummy != NULL);
 320
 321   /* Describe the register's location.  Generic dummy frames always
 322      have the register value in an ``expression''.  */
 323   *optimized = 0;
 324   *lvalp = not_lval;
 325   *addrp = 0;
 326   *realnum = -1;
 327
 328   /* If needed, find and return the value of the register.  */
 329   if (bufferp != NULL)
 330     {
 331       /* Return the actual value.  */
 332       /* Use the regcache_cooked_read() method so that it, on the fly,
 333          constructs either a raw or pseudo register from the raw
 334          register cache.  */
 335       regcache_cooked_read (dummy->regcache, regnum, bufferp);
 336     }
 337 }
 338
 339 /* Assuming that THIS frame is a dummy (remember, the NEXT and not
 340    THIS frame is passed in), return the ID of THIS frame.  That ID is
 341    determined by examining the NEXT frame's unwound registers using
 342    the method unwind_dummy_id().  As a side effect, THIS dummy frame's
 343    dummy cache is located and and saved in THIS_PROLOGUE_CACHE.  */
 344
 345 static void
 346 dummy_frame_this_id (struct frame_info *next_frame,
 347                      void **this_prologue_cache,
 348                      struct frame_id *this_id)
 349 {
 350   struct dummy_frame *dummy = (*this_prologue_cache);
 351   if (dummy != NULL)
 352     {
 353       (*this_id) = dummy->id;
 354       return;
 355     }
 356   /* When unwinding a normal frame, the stack structure is determined
 357      by analyzing the frame's function's code (be it using brute force
 358      prologue analysis, or the dwarf2 CFI).  In the case of a dummy
 359      frame, that simply isn't possible.  The The PC is either the
 360      program entry point, or some random address on the stack.  Trying
 361      to use that PC to apply standard frame ID unwind techniques is
 362      just asking for trouble.  */
 363   if (gdbarch_unwind_dummy_id_p (current_gdbarch))
 364     {
 365       /* Use an architecture specific method to extract the prev's
 366          dummy ID from the next frame.  Note that this method uses
 367          frame_register_unwind to obtain the register values needed to
 368          determine the dummy frame's ID.  */
 369       (*this_id) = gdbarch_unwind_dummy_id (current_gdbarch, next_frame);
 370     }
 371   else if (frame_relative_level (next_frame) < 0)
 372     {
 373       /* We're unwinding a sentinel frame, the PC of which is pointing
 374          at a stack dummy.  Fake up the dummy frame's ID using the
 375          same sequence as is found a traditional unwinder.  Once all
 376          architectures supply the unwind_dummy_id method, this code
 377          can go away.  */
 378       (*this_id) = frame_id_build (deprecated_read_fp (), read_pc ());
 379     }
 380   else if (legacy_frame_p (current_gdbarch)
 381            && get_prev_frame (next_frame))
 382     {
 383       /* Things are looking seriously grim!  Assume that the legacy
 384          get_prev_frame code has already created THIS frame and linked
 385          it in to the frame chain (a pretty bold assumption), extract
 386          the ID from THIS base / pc.  */
 387       (*this_id) = frame_id_build (get_frame_base (get_prev_frame (next_frame)),
 388                                    get_frame_pc (get_prev_frame (next_frame)));
 389     }
 390   else
 391     {
 392       /* Ouch!  We're not trying to find the innermost frame's ID yet
 393          we're trying to unwind to a dummy.  The architecture must
 394          provide the unwind_dummy_id() method.  Abandon the unwind
 395          process but only after first warning the user.  */
 396       internal_warning (__FILE__, __LINE__,
 397                         "Missing unwind_dummy_id architecture method");
 398       (*this_id) = null_frame_id;
 399       return;
 400     }
 401   (*this_prologue_cache) = find_dummy_frame ((*this_id).code_addr,
 402                                              (*this_id).stack_addr);
 403 }
 404
 405 static struct frame_unwind dummy_frame_unwind =
 406 {
 407   DUMMY_FRAME,
 408   dummy_frame_this_id,
 409   dummy_frame_prev_register
 410 };
 411
 412 const struct frame_unwind *
 413 dummy_frame_sniffer (struct frame_info *next_frame)
 414 {
 415   CORE_ADDR pc = frame_pc_unwind (next_frame);
 416   gdb_assert (DEPRECATED_USE_GENERIC_DUMMY_FRAMES);
 417   if (pc_in_dummy_frame (pc))
 418     return &dummy_frame_unwind;
 419   else
 420     return NULL;
 421 }
 422
 423 static void
 424 fprint_dummy_frames (struct ui_file *file)
 425 {
 426   struct dummy_frame *s;
 427   for (s = dummy_frame_stack; s != NULL; s = s->next)
 428     {
 429       gdb_print_host_address (s, file);
 430       fprintf_unfiltered (file, ":");
 431       fprintf_unfiltered (file, " pc=0x%s", paddr (s->pc));
 432       fprintf_unfiltered (file, " fp=0x%s", paddr (s->fp));
 433       fprintf_unfiltered (file, " sp=0x%s", paddr (s->sp));
 434       fprintf_unfiltered (file, " top=0x%s", paddr (s->top));
 435       fprintf_unfiltered (file, " id=");
 436       fprint_frame_id (file, s->id);
 437       fprintf_unfiltered (file, " call_lo=0x%s", paddr (s->call_lo));
 438       fprintf_unfiltered (file, " call_hi=0x%s", paddr (s->call_hi));
 439       fprintf_unfiltered (file, "\n");
 440     }
 441 }
 442
 443 static void
 444 maintenance_print_dummy_frames (char *args, int from_tty)
 445 {
 446   if (args == NULL)
 447     fprint_dummy_frames (gdb_stdout);
 448   else
 449     {
 450       struct ui_file *file = gdb_fopen (args, "w");
 451       if (file == NULL)
 452         perror_with_name ("maintenance print dummy-frames");
 453       fprint_dummy_frames (file);
 454       ui_file_delete (file);
 455     }
 456 }
 457
 458 extern void _initialize_dummy_frame (void);
 459
 460 void
 461 _initialize_dummy_frame (void)
 462 {
 463   add_cmd ("dummy-frames", class_maintenance, maintenance_print_dummy_frames,
 464            "Print the contents of the internal dummy-frame stack.",
 465            &maintenanceprintlist);
 466
 467 }