gdb/dummy-frame.c

   1 /* Code dealing with dummy stack frames, for GDB, the GNU debugger.
   2
   3    Copyright (C) 1986-2024 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 "dummy-frame.h"
  22 #include "regcache.h"
  23 #include "frame.h"
  24 #include "inferior.h"
  25 #include "frame-unwind.h"
  26 #include "command.h"
  27 #include "gdbcmd.h"
  28 #include "observable.h"
  29 #include "gdbthread.h"
  30 #include "infcall.h"
  31 #include "gdbarch.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   thread_info *thread;
  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 id1->id == id2->id && id1->thread == id2->thread;
  50 }
  51
  52 /* List of dummy_frame destructors.  */
  53
  54 struct dummy_frame_dtor_list
  55 {
  56   /* Next element in the list or NULL if this is the last element.  */
  57   struct dummy_frame_dtor_list *next;
  58
  59   /* If non-NULL, a destructor that is run when this dummy frame is freed.  */
  60   dummy_frame_dtor_ftype *dtor;
  61
  62   /* Arbitrary data that is passed to DTOR.  */
  63   void *dtor_data;
  64 };
  65
  66 /* Dummy frame.  This saves the processor state just prior to setting
  67    up the inferior function call.  Older targets save the registers
  68    on the target stack (but that really slows down function calls).  */
  69
  70 struct dummy_frame
  71 {
  72   struct dummy_frame *next;
  73
  74   /* An id represents a dummy frame.  */
  75   struct dummy_frame_id id;
  76
  77   /* The caller's state prior to the call.  */
  78   struct infcall_suspend_state *caller_state;
  79
  80   /* First element of destructors list or NULL if there are no
  81      destructors registered for this dummy_frame.  */
  82   struct dummy_frame_dtor_list *dtor_list;
  83 };
  84
  85 static struct dummy_frame *dummy_frame_stack = NULL;
  86
  87 /* Push the caller's state, along with the dummy frame info, onto the
  88    dummy-frame stack.  */
  89
  90 void
  91 dummy_frame_push (struct infcall_suspend_state *caller_state,
  92                   const frame_id *dummy_id, thread_info *thread)
  93 {
  94   struct dummy_frame *dummy_frame;
  95
  96   dummy_frame = XCNEW (struct dummy_frame);
  97   dummy_frame->caller_state = caller_state;
  98   dummy_frame->id.id = (*dummy_id);
  99   dummy_frame->id.thread = thread;
 100   dummy_frame->next = dummy_frame_stack;
 101   dummy_frame_stack = dummy_frame;
 102 }
 103
 104 /* Remove *DUMMY_PTR from the dummy frame stack.  */
 105
 106 static void
 107 remove_dummy_frame (struct dummy_frame **dummy_ptr)
 108 {
 109   struct dummy_frame *dummy = *dummy_ptr;
 110
 111   while (dummy->dtor_list != NULL)
 112     {
 113       struct dummy_frame_dtor_list *list = dummy->dtor_list;
 114
 115       dummy->dtor_list = list->next;
 116       list->dtor (list->dtor_data, 0);
 117       xfree (list);
 118     }
 119
 120   *dummy_ptr = dummy->next;
 121   discard_infcall_suspend_state (dummy->caller_state);
 122   xfree (dummy);
 123 }
 124
 125 /* Delete any breakpoint B which is a momentary breakpoint for return from
 126    inferior call matching DUMMY_VOIDP.  */
 127
 128 static bool
 129 pop_dummy_frame_bpt (struct breakpoint *b, struct dummy_frame *dummy)
 130 {
 131   if (b->thread == dummy->id.thread->global_num
 132       && b->disposition == disp_del && b->frame_id == dummy->id.id)
 133     {
 134       while (b->related_breakpoint != b)
 135         delete_breakpoint (b->related_breakpoint);
 136
 137       delete_breakpoint (b);
 138
 139       /* Stop the traversal.  */
 140       return true;
 141     }
 142
 143   /* Continue the traversal.  */
 144   return false;
 145 }
 146
 147 /* Pop *DUMMY_PTR, restoring program state to that before the
 148    frame was created.  */
 149
 150 static void
 151 pop_dummy_frame (struct dummy_frame **dummy_ptr)
 152 {
 153   struct dummy_frame *dummy = *dummy_ptr;
 154
 155   gdb_assert (dummy->id.thread == inferior_thread ());
 156
 157   while (dummy->dtor_list != NULL)
 158     {
 159       struct dummy_frame_dtor_list *list = dummy->dtor_list;
 160
 161       dummy->dtor_list = list->next;
 162       list->dtor (list->dtor_data, 1);
 163       xfree (list);
 164     }
 165
 166   restore_infcall_suspend_state (dummy->caller_state);
 167
 168   for (breakpoint &bp : all_breakpoints_safe ())
 169     if (pop_dummy_frame_bpt (&bp, dummy))
 170       break;
 171
 172   /* restore_infcall_control_state frees inf_state,
 173      all that remains is to pop *dummy_ptr.  */
 174   *dummy_ptr = dummy->next;
 175   xfree (dummy);
 176
 177   /* We've made right mess of GDB's local state, just discard
 178      everything.  */
 179   reinit_frame_cache ();
 180 }
 181
 182 /* Look up DUMMY_ID.
 183    Return NULL if not found.  */
 184
 185 static struct dummy_frame **
 186 lookup_dummy_frame (struct dummy_frame_id *dummy_id)
 187 {
 188   struct dummy_frame **dp;
 189
 190   for (dp = &dummy_frame_stack; *dp != NULL; dp = &(*dp)->next)
 191     {
 192       if (dummy_frame_id_eq (&(*dp)->id, dummy_id))
 193         return dp;
 194     }
 195
 196   return NULL;
 197 }
 198
 199 /* Find the dummy frame by DUMMY_ID and THREAD, and pop it, restoring
 200    program state to that before the frame was created.
 201    On return reinit_frame_cache has been called.
 202    If the frame isn't found, flag an internal error.  */
 203
 204 void
 205 dummy_frame_pop (frame_id dummy_id, thread_info *thread)
 206 {
 207   struct dummy_frame **dp;
 208   struct dummy_frame_id id = { dummy_id, thread };
 209
 210   dp = lookup_dummy_frame (&id);
 211   gdb_assert (dp != NULL);
 212
 213   pop_dummy_frame (dp);
 214 }
 215
 216 /* Find the dummy frame by DUMMY_ID and PTID and drop it.  Do nothing
 217    if it is not found.  Do not restore its state into inferior, just
 218    free its memory.  */
 219
 220 void
 221 dummy_frame_discard (struct frame_id dummy_id, thread_info *thread)
 222 {
 223   struct dummy_frame **dp;
 224   struct dummy_frame_id id = { dummy_id, thread };
 225
 226   dp = lookup_dummy_frame (&id);
 227   if (dp)
 228     remove_dummy_frame (dp);
 229 }
 230
 231 /* See dummy-frame.h.  */
 232
 233 void
 234 register_dummy_frame_dtor (frame_id dummy_id, thread_info *thread,
 235                            dummy_frame_dtor_ftype *dtor, void *dtor_data)
 236 {
 237   struct dummy_frame_id id = { dummy_id, thread };
 238   struct dummy_frame **dp, *d;
 239   struct dummy_frame_dtor_list *list;
 240
 241   dp = lookup_dummy_frame (&id);
 242   gdb_assert (dp != NULL);
 243   d = *dp;
 244   list = XNEW (struct dummy_frame_dtor_list);
 245   list->next = d->dtor_list;
 246   d->dtor_list = list;
 247   list->dtor = dtor;
 248   list->dtor_data = dtor_data;
 249 }
 250
 251 /* See dummy-frame.h.  */
 252
 253 int
 254 find_dummy_frame_dtor (dummy_frame_dtor_ftype *dtor, void *dtor_data)
 255 {
 256   struct dummy_frame *d;
 257
 258   for (d = dummy_frame_stack; d != NULL; d = d->next)
 259     {
 260       struct dummy_frame_dtor_list *list;
 261
 262       for (list = d->dtor_list; list != NULL; list = list->next)
 263         if (list->dtor == dtor && list->dtor_data == dtor_data)
 264           return 1;
 265     }
 266   return 0;
 267 }
 268
 269 /* There may be stale dummy frames, perhaps left over from when an uncaught
 270    longjmp took us out of a function that was called by the debugger.  Clean
 271    them up at least once whenever we start a new inferior.  */
 272
 273 static void
 274 cleanup_dummy_frames (inferior *inf)
 275 {
 276   while (dummy_frame_stack != NULL)
 277     remove_dummy_frame (&dummy_frame_stack);
 278 }
 279
 280 /* Return the dummy frame cache, it contains both the ID, and a
 281    pointer to the regcache.  */
 282 struct dummy_frame_cache
 283 {
 284   struct frame_id this_id;
 285   readonly_detached_regcache *prev_regcache;
 286 };
 287
 288 static int
 289 dummy_frame_sniffer (const struct frame_unwind *self,
 290                      const frame_info_ptr &this_frame,
 291                      void **this_prologue_cache)
 292 {
 293   /* When unwinding a normal frame, the stack structure is determined
 294      by analyzing the frame's function's code (be it using brute force
 295      prologue analysis, or the dwarf2 CFI).  In the case of a dummy
 296      frame, that simply isn't possible.  The PC is either the program
 297      entry point, or some random address on the stack.  Trying to use
 298      that PC to apply standard frame ID unwind techniques is just
 299      asking for trouble.  */
 300
 301   /* Don't bother unless there is at least one dummy frame.  */
 302   if (dummy_frame_stack != NULL)
 303     {
 304       struct dummy_frame *dummyframe;
 305       /* Use an architecture specific method to extract this frame's
 306          dummy ID, assuming it is a dummy frame.  */
 307       struct frame_id this_id
 308         = gdbarch_dummy_id (get_frame_arch (this_frame), this_frame);
 309       struct dummy_frame_id dummy_id = { this_id, inferior_thread () };
 310
 311       /* Use that ID to find the corresponding cache entry.  */
 312       for (dummyframe = dummy_frame_stack;
 313            dummyframe != NULL;
 314            dummyframe = dummyframe->next)
 315         {
 316           if (dummy_frame_id_eq (&dummyframe->id, &dummy_id))
 317             {
 318               struct dummy_frame_cache *cache;
 319
 320               cache = FRAME_OBSTACK_ZALLOC (struct dummy_frame_cache);
 321               cache->prev_regcache = get_infcall_suspend_state_regcache
 322                                                    (dummyframe->caller_state);
 323               cache->this_id = this_id;
 324               (*this_prologue_cache) = cache;
 325               return 1;
 326             }
 327         }
 328     }
 329   return 0;
 330 }
 331
 332 /* Given a call-dummy dummy-frame, return the registers.  Here the
 333    register value is taken from the local copy of the register buffer.  */
 334
 335 static struct value *
 336 dummy_frame_prev_register (const frame_info_ptr &this_frame,
 337                            void **this_prologue_cache,
 338                            int regnum)
 339 {
 340   struct dummy_frame_cache *cache
 341     = (struct dummy_frame_cache *) *this_prologue_cache;
 342   struct gdbarch *gdbarch = get_frame_arch (this_frame);
 343   struct value *reg_val;
 344
 345   /* The dummy-frame sniffer always fills in the cache.  */
 346   gdb_assert (cache != NULL);
 347
 348   /* Describe the register's location.  Generic dummy frames always
 349      have the register value in an ``expression''.  */
 350   reg_val = value::zero (register_type (gdbarch, regnum), not_lval);
 351
 352   /* Use the regcache_cooked_read() method so that it, on the fly,
 353      constructs either a raw or pseudo register from the raw
 354      register cache.  */
 355   cache->prev_regcache->cooked_read
 356     (regnum, reg_val->contents_writeable ().data ());
 357   return reg_val;
 358 }
 359
 360 /* Assuming that THIS_FRAME is a dummy, return its ID.  That ID is
 361    determined by examining the NEXT frame's unwound registers using
 362    the method dummy_id().  As a side effect, THIS dummy frame's
 363    dummy cache is located and saved in THIS_PROLOGUE_CACHE.  */
 364
 365 static void
 366 dummy_frame_this_id (const frame_info_ptr &this_frame,
 367                      void **this_prologue_cache,
 368                      struct frame_id *this_id)
 369 {
 370   /* The dummy-frame sniffer always fills in the cache.  */
 371   struct dummy_frame_cache *cache
 372     = (struct dummy_frame_cache *) *this_prologue_cache;
 373
 374   gdb_assert (cache != NULL);
 375   (*this_id) = cache->this_id;
 376 }
 377
 378 const struct frame_unwind dummy_frame_unwind =
 379 {
 380   "dummy",
 381   DUMMY_FRAME,
 382   default_frame_unwind_stop_reason,
 383   dummy_frame_this_id,
 384   dummy_frame_prev_register,
 385   NULL,
 386   dummy_frame_sniffer,
 387 };
 388
 389 /* See dummy-frame.h.  */
 390
 391 struct frame_id
 392 default_dummy_id (struct gdbarch *gdbarch, const frame_info_ptr &this_frame)
 393 {
 394   CORE_ADDR sp, pc;
 395
 396   sp = get_frame_sp (this_frame);
 397   pc = get_frame_pc (this_frame);
 398   return frame_id_build (sp, pc);
 399 }
 400
 401 static void
 402 fprint_dummy_frames (struct ui_file *file)
 403 {
 404   struct dummy_frame *s;
 405
 406   for (s = dummy_frame_stack; s != NULL; s = s->next)
 407     gdb_printf (file, "%s: id=%s, ptid=%s\n",
 408                 host_address_to_string (s),
 409                 s->id.id.to_string ().c_str (),
 410                 s->id.thread->ptid.to_string ().c_str ());
 411 }
 412
 413 static void
 414 maintenance_print_dummy_frames (const char *args, int from_tty)
 415 {
 416   if (args == NULL)
 417     fprint_dummy_frames (gdb_stdout);
 418   else
 419     {
 420       stdio_file file;
 421
 422       if (!file.open (args, "w"))
 423         perror_with_name (_("maintenance print dummy-frames"));
 424       fprint_dummy_frames (&file);
 425     }
 426 }
 427
 428 void _initialize_dummy_frame ();
 429 void
 430 _initialize_dummy_frame ()
 431 {
 432   add_cmd ("dummy-frames", class_maintenance, maintenance_print_dummy_frames,
 433            _("Print the contents of the internal dummy-frame stack."),
 434            &maintenanceprintlist);
 435
 436   gdb::observers::inferior_created.attach (cleanup_dummy_frames, "dummy-frame");
 437 }