gdb/dummy-frame.c

   1 /* Code dealing with dummy stack frames, for GDB, the GNU debugger.
   2
   3    Copyright (C) 1986-2015 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20
  21 #include "defs.h"
  22 #include "dummy-frame.h"
  23 #include "regcache.h"
  24 #include "frame.h"
  25 #include "inferior.h"
  26 #include "frame-unwind.h"
  27 #include "command.h"
  28 #include "gdbcmd.h"
  29 #include "observer.h"
  30 #include "gdbthread.h"
  31 #include "infcall.h"
  32
  33 struct dummy_frame_id
  34 {
  35   /* This frame's ID.  Must match the value returned by
  36      gdbarch_dummy_id.  */
  37   struct frame_id id;
  38
  39   /* The thread this dummy_frame relates to.  */
  40   ptid_t ptid;
  41 };
  42
  43 /* Return whether dummy_frame_id *ID1 and *ID2 are equal.  */
  44
  45 static int
  46 dummy_frame_id_eq (struct dummy_frame_id *id1,
  47                    struct dummy_frame_id *id2)
  48 {
  49   return frame_id_eq (id1->id, id2->id) && ptid_equal (id1->ptid, id2->ptid);
  50 }
  51
  52 /* Dummy frame.  This saves the processor state just prior to setting
  53    up the inferior function call.  Older targets save the registers
  54    on the target stack (but that really slows down function calls).  */
  55
  56 struct dummy_frame
  57 {
  58   struct dummy_frame *next;
  59
  60   /* An id represents a dummy frame.  */
  61   struct dummy_frame_id id;
  62
  63   /* The caller's state prior to the call.  */
  64   struct infcall_suspend_state *caller_state;
  65
  66   /* If non-NULL, a destructor that is run when this dummy frame is freed.  */
  67   dummy_frame_dtor_ftype *dtor;
  68
  69   /* Arbitrary data that is passed to DTOR.  */
  70   void *dtor_data;
  71 };
  72
  73 static struct dummy_frame *dummy_frame_stack = NULL;
  74
  75 /* Push the caller's state, along with the dummy frame info, onto the
  76    dummy-frame stack.  */
  77
  78 void
  79 dummy_frame_push (struct infcall_suspend_state *caller_state,
  80                   const struct frame_id *dummy_id, ptid_t ptid)
  81 {
  82   struct dummy_frame *dummy_frame;
  83
  84   dummy_frame = XCNEW (struct dummy_frame);
  85   dummy_frame->caller_state = caller_state;
  86   dummy_frame->id.id = (*dummy_id);
  87   dummy_frame->id.ptid = ptid;
  88   dummy_frame->next = dummy_frame_stack;
  89   dummy_frame_stack = dummy_frame;
  90 }
  91
  92 /* Remove *DUMMY_PTR from the dummy frame stack.  */
  93
  94 static void
  95 remove_dummy_frame (struct dummy_frame **dummy_ptr)
  96 {
  97   struct dummy_frame *dummy = *dummy_ptr;
  98
  99   if (dummy->dtor != NULL)
 100     dummy->dtor (dummy->dtor_data, 0);
 101
 102   *dummy_ptr = dummy->next;
 103   discard_infcall_suspend_state (dummy->caller_state);
 104   xfree (dummy);
 105 }
 106
 107 /* Delete any breakpoint B which is a momentary breakpoint for return from
 108    inferior call matching DUMMY_VOIDP.  */
 109
 110 static int
 111 pop_dummy_frame_bpt (struct breakpoint *b, void *dummy_voidp)
 112 {
 113   struct dummy_frame *dummy = dummy_voidp;
 114
 115   if (b->thread == pid_to_thread_id (dummy->id.ptid)
 116       && b->disposition == disp_del && frame_id_eq (b->frame_id, dummy->id.id))
 117     {
 118       while (b->related_breakpoint != b)
 119         delete_breakpoint (b->related_breakpoint);
 120
 121       delete_breakpoint (b);
 122
 123       /* Stop the traversal.  */
 124       return 1;
 125     }
 126
 127   /* Continue the traversal.  */
 128   return 0;
 129 }
 130
 131 /* Pop *DUMMY_PTR, restoring program state to that before the
 132    frame was created.  */
 133
 134 static void
 135 pop_dummy_frame (struct dummy_frame **dummy_ptr)
 136 {
 137   struct dummy_frame *dummy = *dummy_ptr;
 138
 139   gdb_assert (ptid_equal (dummy->id.ptid, inferior_ptid));
 140
 141   if (dummy->dtor != NULL)
 142     dummy->dtor (dummy->dtor_data, 1);
 143
 144   restore_infcall_suspend_state (dummy->caller_state);
 145
 146   iterate_over_breakpoints (pop_dummy_frame_bpt, dummy);
 147
 148   /* restore_infcall_control_state frees inf_state,
 149      all that remains is to pop *dummy_ptr.  */
 150   *dummy_ptr = dummy->next;
 151   xfree (dummy);
 152
 153   /* We've made right mess of GDB's local state, just discard
 154      everything.  */
 155   reinit_frame_cache ();
 156 }
 157
 158 /* Look up DUMMY_ID.
 159    Return NULL if not found.  */
 160
 161 static struct dummy_frame **
 162 lookup_dummy_frame (struct dummy_frame_id *dummy_id)
 163 {
 164   struct dummy_frame **dp;
 165
 166   for (dp = &dummy_frame_stack; *dp != NULL; dp = &(*dp)->next)
 167     {
 168       if (dummy_frame_id_eq (&(*dp)->id, dummy_id))
 169         return dp;
 170     }
 171
 172   return NULL;
 173 }
 174
 175 /* Find the dummy frame by DUMMY_ID and PTID, and pop it, restoring
 176    program state to that before the frame was created.
 177    On return reinit_frame_cache has been called.
 178    If the frame isn't found, flag an internal error.  */
 179
 180 void
 181 dummy_frame_pop (struct frame_id dummy_id, ptid_t ptid)
 182 {
 183   struct dummy_frame **dp;
 184   struct dummy_frame_id id = { dummy_id, ptid };
 185
 186   dp = lookup_dummy_frame (&id);
 187   gdb_assert (dp != NULL);
 188
 189   pop_dummy_frame (dp);
 190 }
 191
 192 /* Find the dummy frame by DUMMY_ID and PTID and drop it.  Do nothing
 193    if it is not found.  Do not restore its state into inferior, just
 194    free its memory.  */
 195
 196 void
 197 dummy_frame_discard (struct frame_id dummy_id, ptid_t ptid)
 198 {
 199   struct dummy_frame **dp;
 200   struct dummy_frame_id id = { dummy_id, ptid };
 201
 202   dp = lookup_dummy_frame (&id);
 203   if (dp)
 204     remove_dummy_frame (dp);
 205 }
 206
 207 /* See dummy-frame.h.  */
 208
 209 void
 210 register_dummy_frame_dtor (struct frame_id dummy_id, ptid_t ptid,
 211                            dummy_frame_dtor_ftype *dtor, void *dtor_data)
 212 {
 213   struct dummy_frame_id id = { dummy_id, ptid };
 214   struct dummy_frame **dp, *d;
 215
 216   dp = lookup_dummy_frame (&id);
 217   gdb_assert (dp != NULL);
 218   d = *dp;
 219   gdb_assert (d->dtor == NULL);
 220   d->dtor = dtor;
 221   d->dtor_data = dtor_data;
 222 }
 223
 224 /* See dummy-frame.h.  */
 225
 226 int
 227 find_dummy_frame_dtor (dummy_frame_dtor_ftype *dtor, void *dtor_data)
 228 {
 229   struct dummy_frame *d;
 230
 231   for (d = dummy_frame_stack; d != NULL; d = d->next)
 232     if (d->dtor == dtor && d->dtor_data == dtor_data)
 233       return 1;
 234   return 0;
 235 }
 236
 237 /* There may be stale dummy frames, perhaps left over from when an uncaught
 238    longjmp took us out of a function that was called by the debugger.  Clean
 239    them up at least once whenever we start a new inferior.  */
 240
 241 static void
 242 cleanup_dummy_frames (struct target_ops *target, int from_tty)
 243 {
 244   while (dummy_frame_stack != NULL)
 245     remove_dummy_frame (&dummy_frame_stack);
 246 }
 247
 248 /* Return the dummy frame cache, it contains both the ID, and a
 249    pointer to the regcache.  */
 250 struct dummy_frame_cache
 251 {
 252   struct frame_id this_id;
 253   struct regcache *prev_regcache;
 254 };
 255
 256 static int
 257 dummy_frame_sniffer (const struct frame_unwind *self,
 258                      struct frame_info *this_frame,
 259                      void **this_prologue_cache)
 260 {
 261   /* When unwinding a normal frame, the stack structure is determined
 262      by analyzing the frame's function's code (be it using brute force
 263      prologue analysis, or the dwarf2 CFI).  In the case of a dummy
 264      frame, that simply isn't possible.  The PC is either the program
 265      entry point, or some random address on the stack.  Trying to use
 266      that PC to apply standard frame ID unwind techniques is just
 267      asking for trouble.  */
 268
 269   /* Don't bother unless there is at least one dummy frame.  */
 270   if (dummy_frame_stack != NULL)
 271     {
 272       struct dummy_frame *dummyframe;
 273       /* Use an architecture specific method to extract this frame's
 274          dummy ID, assuming it is a dummy frame.  */
 275       struct frame_id this_id
 276         = gdbarch_dummy_id (get_frame_arch (this_frame), this_frame);
 277       struct dummy_frame_id dummy_id = { this_id, inferior_ptid };
 278
 279       /* Use that ID to find the corresponding cache entry.  */
 280       for (dummyframe = dummy_frame_stack;
 281            dummyframe != NULL;
 282            dummyframe = dummyframe->next)
 283         {
 284           if (dummy_frame_id_eq (&dummyframe->id, &dummy_id))
 285             {
 286               struct dummy_frame_cache *cache;
 287
 288               cache = FRAME_OBSTACK_ZALLOC (struct dummy_frame_cache);
 289               cache->prev_regcache = get_infcall_suspend_state_regcache
 290                                                    (dummyframe->caller_state);
 291               cache->this_id = this_id;
 292               (*this_prologue_cache) = cache;
 293               return 1;
 294             }
 295         }
 296     }
 297   return 0;
 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 struct value *
 304 dummy_frame_prev_register (struct frame_info *this_frame,
 305                            void **this_prologue_cache,
 306                            int regnum)
 307 {
 308   struct dummy_frame_cache *cache = (*this_prologue_cache);
 309   struct gdbarch *gdbarch = get_frame_arch (this_frame);
 310   struct value *reg_val;
 311
 312   /* The dummy-frame sniffer always fills in the cache.  */
 313   gdb_assert (cache != NULL);
 314
 315   /* Describe the register's location.  Generic dummy frames always
 316      have the register value in an ``expression''.  */
 317   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 318
 319   /* Use the regcache_cooked_read() method so that it, on the fly,
 320      constructs either a raw or pseudo register from the raw
 321      register cache.  */
 322   regcache_cooked_read (cache->prev_regcache, regnum,
 323                         value_contents_writeable (reg_val));
 324   return reg_val;
 325 }
 326
 327 /* Assuming that THIS_FRAME is a dummy, return its ID.  That ID is
 328    determined by examining the NEXT frame's unwound registers using
 329    the method dummy_id().  As a side effect, THIS dummy frame's
 330    dummy cache is located and saved in THIS_PROLOGUE_CACHE.  */
 331
 332 static void
 333 dummy_frame_this_id (struct frame_info *this_frame,
 334                      void **this_prologue_cache,
 335                      struct frame_id *this_id)
 336 {
 337   /* The dummy-frame sniffer always fills in the cache.  */
 338   struct dummy_frame_cache *cache = (*this_prologue_cache);
 339
 340   gdb_assert (cache != NULL);
 341   (*this_id) = cache->this_id;
 342 }
 343
 344 const struct frame_unwind dummy_frame_unwind =
 345 {
 346   DUMMY_FRAME,
 347   default_frame_unwind_stop_reason,
 348   dummy_frame_this_id,
 349   dummy_frame_prev_register,
 350   NULL,
 351   dummy_frame_sniffer,
 352 };
 353
 354 static void
 355 fprint_dummy_frames (struct ui_file *file)
 356 {
 357   struct dummy_frame *s;
 358
 359   for (s = dummy_frame_stack; s != NULL; s = s->next)
 360     {
 361       gdb_print_host_address (s, file);
 362       fprintf_unfiltered (file, ":");
 363       fprintf_unfiltered (file, " id=");
 364       fprint_frame_id (file, s->id.id);
 365       fprintf_unfiltered (file, ", ptid=%s",
 366                           target_pid_to_str (s->id.ptid));
 367       fprintf_unfiltered (file, "\n");
 368     }
 369 }
 370
 371 static void
 372 maintenance_print_dummy_frames (char *args, int from_tty)
 373 {
 374   if (args == NULL)
 375     fprint_dummy_frames (gdb_stdout);
 376   else
 377     {
 378       struct cleanup *cleanups;
 379       struct ui_file *file = gdb_fopen (args, "w");
 380
 381       if (file == NULL)
 382         perror_with_name (_("maintenance print dummy-frames"));
 383       cleanups = make_cleanup_ui_file_delete (file);
 384       fprint_dummy_frames (file);
 385       do_cleanups (cleanups);
 386     }
 387 }
 388
 389 extern void _initialize_dummy_frame (void);
 390
 391 void
 392 _initialize_dummy_frame (void)
 393 {
 394   add_cmd ("dummy-frames", class_maintenance, maintenance_print_dummy_frames,
 395            _("Print the contents of the internal dummy-frame stack."),
 396            &maintenanceprintlist);
 397
 398   observer_attach_inferior_created (cleanup_dummy_frames);
 399 }