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
  32 struct dummy_frame_id
  33 {
  34   /* This frame's ID.  Must match the value returned by
  35      gdbarch_dummy_id.  */
  36   struct frame_id id;
  37
  38   /* The thread this dummy_frame relates to.  */
  39   ptid_t ptid;
  40 };
  41
  42 /* Return whether dummy_frame_id *ID1 and *ID2 are equal.  */
  43
  44 static int
  45 dummy_frame_id_eq (struct dummy_frame_id *id1,
  46                    struct dummy_frame_id *id2)
  47 {
  48   return frame_id_eq (id1->id, id2->id) && ptid_equal (id1->ptid, id2->ptid);
  49 }
  50
  51 /* Dummy frame.  This saves the processor state just prior to setting
  52    up the inferior function call.  Older targets save the registers
  53    on the target stack (but that really slows down function calls).  */
  54
  55 struct dummy_frame
  56 {
  57   struct dummy_frame *next;
  58
  59   /* An id represents a dummy frame.  */
  60   struct dummy_frame_id id;
  61
  62   /* The caller's state prior to the call.  */
  63   struct infcall_suspend_state *caller_state;
  64
  65   /* If non-NULL, a destructor that is run when this dummy frame is
  66      popped.  */
  67   void (*dtor) (void *data);
  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   *dummy_ptr = dummy->next;
 100   discard_infcall_suspend_state (dummy->caller_state);
 101   xfree (dummy);
 102 }
 103
 104 /* Delete any breakpoint B which is a momentary breakpoint for return from
 105    inferior call matching DUMMY_VOIDP.  */
 106
 107 static int
 108 pop_dummy_frame_bpt (struct breakpoint *b, void *dummy_voidp)
 109 {
 110   struct dummy_frame *dummy = dummy_voidp;
 111
 112   if (b->thread == pid_to_thread_id (dummy->id.ptid)
 113       && b->disposition == disp_del && frame_id_eq (b->frame_id, dummy->id.id))
 114     {
 115       while (b->related_breakpoint != b)
 116         delete_breakpoint (b->related_breakpoint);
 117
 118       delete_breakpoint (b);
 119
 120       /* Stop the traversal.  */
 121       return 1;
 122     }
 123
 124   /* Continue the traversal.  */
 125   return 0;
 126 }
 127
 128 /* Pop *DUMMY_PTR, restoring program state to that before the
 129    frame was created.  */
 130
 131 static void
 132 pop_dummy_frame (struct dummy_frame **dummy_ptr)
 133 {
 134   struct dummy_frame *dummy = *dummy_ptr;
 135
 136   gdb_assert (ptid_equal (dummy->id.ptid, inferior_ptid));
 137
 138   if (dummy->dtor != NULL)
 139     dummy->dtor (dummy->dtor_data);
 140
 141   restore_infcall_suspend_state (dummy->caller_state);
 142
 143   iterate_over_breakpoints (pop_dummy_frame_bpt, dummy);
 144
 145   /* restore_infcall_control_state frees inf_state,
 146      all that remains is to pop *dummy_ptr.  */
 147   *dummy_ptr = dummy->next;
 148   xfree (dummy);
 149
 150   /* We've made right mess of GDB's local state, just discard
 151      everything.  */
 152   reinit_frame_cache ();
 153 }
 154
 155 /* Look up DUMMY_ID.
 156    Return NULL if not found.  */
 157
 158 static struct dummy_frame **
 159 lookup_dummy_frame (struct dummy_frame_id *dummy_id)
 160 {
 161   struct dummy_frame **dp;
 162
 163   for (dp = &dummy_frame_stack; *dp != NULL; dp = &(*dp)->next)
 164     {
 165       if (dummy_frame_id_eq (&(*dp)->id, dummy_id))
 166         return dp;
 167     }
 168
 169   return NULL;
 170 }
 171
 172 /* Find the dummy frame by DUMMY_ID and PTID, and pop it, restoring
 173    program state to that before the frame was created.
 174    On return reinit_frame_cache has been called.
 175    If the frame isn't found, flag an internal error.  */
 176
 177 void
 178 dummy_frame_pop (struct frame_id dummy_id, ptid_t ptid)
 179 {
 180   struct dummy_frame **dp;
 181   struct dummy_frame_id id = { dummy_id, ptid };
 182
 183   dp = lookup_dummy_frame (&id);
 184   gdb_assert (dp != NULL);
 185
 186   pop_dummy_frame (dp);
 187 }
 188
 189 /* Find the dummy frame by DUMMY_ID and PTID and drop it.  Do nothing
 190    if it is not found.  Do not restore its state into inferior, just
 191    free its memory.  */
 192
 193 void
 194 dummy_frame_discard (struct frame_id dummy_id, ptid_t ptid)
 195 {
 196   struct dummy_frame **dp;
 197   struct dummy_frame_id id = { dummy_id, ptid };
 198
 199   dp = lookup_dummy_frame (&id);
 200   if (dp)
 201     remove_dummy_frame (dp);
 202 }
 203
 204 /* See dummy-frame.h.  */
 205
 206 void
 207 register_dummy_frame_dtor (struct frame_id dummy_id, ptid_t ptid,
 208                            dummy_frame_dtor_ftype *dtor, void *dtor_data)
 209 {
 210   struct dummy_frame_id id = { dummy_id, ptid };
 211   struct dummy_frame **dp, *d;
 212
 213   dp = lookup_dummy_frame (&id);
 214   gdb_assert (dp != NULL);
 215   d = *dp;
 216   gdb_assert (d->dtor == NULL);
 217   d->dtor = dtor;
 218   d->dtor_data = dtor_data;
 219 }
 220
 221 /* See dummy-frame.h.  */
 222
 223 int
 224 find_dummy_frame_dtor (dummy_frame_dtor_ftype *dtor, void *dtor_data)
 225 {
 226   struct dummy_frame *d;
 227
 228   for (d = dummy_frame_stack; d != NULL; d = d->next)
 229     if (d->dtor == dtor && d->dtor_data == dtor_data)
 230       return 1;
 231   return 0;
 232 }
 233
 234 /* There may be stale dummy frames, perhaps left over from when an uncaught
 235    longjmp took us out of a function that was called by the debugger.  Clean
 236    them up at least once whenever we start a new inferior.  */
 237
 238 static void
 239 cleanup_dummy_frames (struct target_ops *target, int from_tty)
 240 {
 241   while (dummy_frame_stack != NULL)
 242     remove_dummy_frame (&dummy_frame_stack);
 243 }
 244
 245 /* Return the dummy frame cache, it contains both the ID, and a
 246    pointer to the regcache.  */
 247 struct dummy_frame_cache
 248 {
 249   struct frame_id this_id;
 250   struct regcache *prev_regcache;
 251 };
 252
 253 static int
 254 dummy_frame_sniffer (const struct frame_unwind *self,
 255                      struct frame_info *this_frame,
 256                      void **this_prologue_cache)
 257 {
 258   /* When unwinding a normal frame, the stack structure is determined
 259      by analyzing the frame's function's code (be it using brute force
 260      prologue analysis, or the dwarf2 CFI).  In the case of a dummy
 261      frame, that simply isn't possible.  The PC is either the program
 262      entry point, or some random address on the stack.  Trying to use
 263      that PC to apply standard frame ID unwind techniques is just
 264      asking for trouble.  */
 265
 266   /* Don't bother unless there is at least one dummy frame.  */
 267   if (dummy_frame_stack != NULL)
 268     {
 269       struct dummy_frame *dummyframe;
 270       /* Use an architecture specific method to extract this frame's
 271          dummy ID, assuming it is a dummy frame.  */
 272       struct frame_id this_id
 273         = gdbarch_dummy_id (get_frame_arch (this_frame), this_frame);
 274       struct dummy_frame_id dummy_id = { this_id, inferior_ptid };
 275
 276       /* Use that ID to find the corresponding cache entry.  */
 277       for (dummyframe = dummy_frame_stack;
 278            dummyframe != NULL;
 279            dummyframe = dummyframe->next)
 280         {
 281           if (dummy_frame_id_eq (&dummyframe->id, &dummy_id))
 282             {
 283               struct dummy_frame_cache *cache;
 284
 285               cache = FRAME_OBSTACK_ZALLOC (struct dummy_frame_cache);
 286               cache->prev_regcache = get_infcall_suspend_state_regcache
 287                                                    (dummyframe->caller_state);
 288               cache->this_id = this_id;
 289               (*this_prologue_cache) = cache;
 290               return 1;
 291             }
 292         }
 293     }
 294   return 0;
 295 }
 296
 297 /* Given a call-dummy dummy-frame, return the registers.  Here the
 298    register value is taken from the local copy of the register buffer.  */
 299
 300 static struct value *
 301 dummy_frame_prev_register (struct frame_info *this_frame,
 302                            void **this_prologue_cache,
 303                            int regnum)
 304 {
 305   struct dummy_frame_cache *cache = (*this_prologue_cache);
 306   struct gdbarch *gdbarch = get_frame_arch (this_frame);
 307   struct value *reg_val;
 308
 309   /* The dummy-frame sniffer always fills in the cache.  */
 310   gdb_assert (cache != NULL);
 311
 312   /* Describe the register's location.  Generic dummy frames always
 313      have the register value in an ``expression''.  */
 314   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 315
 316   /* Use the regcache_cooked_read() method so that it, on the fly,
 317      constructs either a raw or pseudo register from the raw
 318      register cache.  */
 319   regcache_cooked_read (cache->prev_regcache, regnum,
 320                         value_contents_writeable (reg_val));
 321   return reg_val;
 322 }
 323
 324 /* Assuming that THIS_FRAME is a dummy, return its ID.  That ID is
 325    determined by examining the NEXT frame's unwound registers using
 326    the method dummy_id().  As a side effect, THIS dummy frame's
 327    dummy cache is located and saved in THIS_PROLOGUE_CACHE.  */
 328
 329 static void
 330 dummy_frame_this_id (struct frame_info *this_frame,
 331                      void **this_prologue_cache,
 332                      struct frame_id *this_id)
 333 {
 334   /* The dummy-frame sniffer always fills in the cache.  */
 335   struct dummy_frame_cache *cache = (*this_prologue_cache);
 336
 337   gdb_assert (cache != NULL);
 338   (*this_id) = cache->this_id;
 339 }
 340
 341 const struct frame_unwind dummy_frame_unwind =
 342 {
 343   DUMMY_FRAME,
 344   default_frame_unwind_stop_reason,
 345   dummy_frame_this_id,
 346   dummy_frame_prev_register,
 347   NULL,
 348   dummy_frame_sniffer,
 349 };
 350
 351 static void
 352 fprint_dummy_frames (struct ui_file *file)
 353 {
 354   struct dummy_frame *s;
 355
 356   for (s = dummy_frame_stack; s != NULL; s = s->next)
 357     {
 358       gdb_print_host_address (s, file);
 359       fprintf_unfiltered (file, ":");
 360       fprintf_unfiltered (file, " id=");
 361       fprint_frame_id (file, s->id.id);
 362       fprintf_unfiltered (file, ", ptid=%s",
 363                           target_pid_to_str (s->id.ptid));
 364       fprintf_unfiltered (file, "\n");
 365     }
 366 }
 367
 368 static void
 369 maintenance_print_dummy_frames (char *args, int from_tty)
 370 {
 371   if (args == NULL)
 372     fprint_dummy_frames (gdb_stdout);
 373   else
 374     {
 375       struct cleanup *cleanups;
 376       struct ui_file *file = gdb_fopen (args, "w");
 377
 378       if (file == NULL)
 379         perror_with_name (_("maintenance print dummy-frames"));
 380       cleanups = make_cleanup_ui_file_delete (file);
 381       fprint_dummy_frames (file);
 382       do_cleanups (cleanups);
 383     }
 384 }
 385
 386 extern void _initialize_dummy_frame (void);
 387
 388 void
 389 _initialize_dummy_frame (void)
 390 {
 391   add_cmd ("dummy-frames", class_maintenance, maintenance_print_dummy_frames,
 392            _("Print the contents of the internal dummy-frame stack."),
 393            &maintenanceprintlist);
 394
 395   observer_attach_inferior_created (cleanup_dummy_frames);
 396 }