gdb/dummy-frame.c

   1 /* Code dealing with dummy stack frames, for GDB, the GNU debugger.
   2
   3    Copyright (C) 1986-2014 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
  66 static struct dummy_frame *dummy_frame_stack = NULL;
  67
  68 /* Push the caller's state, along with the dummy frame info, onto the
  69    dummy-frame stack.  */
  70
  71 void
  72 dummy_frame_push (struct infcall_suspend_state *caller_state,
  73                   const struct frame_id *dummy_id, ptid_t ptid)
  74 {
  75   struct dummy_frame *dummy_frame;
  76
  77   dummy_frame = XCNEW (struct dummy_frame);
  78   dummy_frame->caller_state = caller_state;
  79   dummy_frame->id.id = (*dummy_id);
  80   dummy_frame->id.ptid = ptid;
  81   dummy_frame->next = dummy_frame_stack;
  82   dummy_frame_stack = dummy_frame;
  83 }
  84
  85 /* Remove *DUMMY_PTR from the dummy frame stack.  */
  86
  87 static void
  88 remove_dummy_frame (struct dummy_frame **dummy_ptr)
  89 {
  90   struct dummy_frame *dummy = *dummy_ptr;
  91
  92   *dummy_ptr = dummy->next;
  93   discard_infcall_suspend_state (dummy->caller_state);
  94   xfree (dummy);
  95 }
  96
  97 /* Delete any breakpoint B which is a momentary breakpoint for return from
  98    inferior call matching DUMMY_VOIDP.  */
  99
 100 static int
 101 pop_dummy_frame_bpt (struct breakpoint *b, void *dummy_voidp)
 102 {
 103   struct dummy_frame *dummy = dummy_voidp;
 104
 105   if (b->thread == pid_to_thread_id (dummy->id.ptid)
 106       && b->disposition == disp_del && frame_id_eq (b->frame_id, dummy->id.id))
 107     {
 108       while (b->related_breakpoint != b)
 109         delete_breakpoint (b->related_breakpoint);
 110
 111       delete_breakpoint (b);
 112
 113       /* Stop the traversal.  */
 114       return 1;
 115     }
 116
 117   /* Continue the traversal.  */
 118   return 0;
 119 }
 120
 121 /* Pop *DUMMY_PTR, restoring program state to that before the
 122    frame was created.  */
 123
 124 static void
 125 pop_dummy_frame (struct dummy_frame **dummy_ptr)
 126 {
 127   struct dummy_frame *dummy = *dummy_ptr;
 128
 129   gdb_assert (ptid_equal (dummy->id.ptid, inferior_ptid));
 130   restore_infcall_suspend_state (dummy->caller_state);
 131
 132   iterate_over_breakpoints (pop_dummy_frame_bpt, dummy);
 133
 134   /* restore_infcall_control_state frees inf_state,
 135      all that remains is to pop *dummy_ptr.  */
 136   *dummy_ptr = dummy->next;
 137   xfree (dummy);
 138
 139   /* We've made right mess of GDB's local state, just discard
 140      everything.  */
 141   reinit_frame_cache ();
 142 }
 143
 144 /* Look up DUMMY_ID.
 145    Return NULL if not found.  */
 146
 147 static struct dummy_frame **
 148 lookup_dummy_frame (struct dummy_frame_id *dummy_id)
 149 {
 150   struct dummy_frame **dp;
 151
 152   for (dp = &dummy_frame_stack; *dp != NULL; dp = &(*dp)->next)
 153     {
 154       if (dummy_frame_id_eq (&(*dp)->id, dummy_id))
 155         return dp;
 156     }
 157
 158   return NULL;
 159 }
 160
 161 /* Find the dummy frame by DUMMY_ID and PTID, and pop it, restoring
 162    program state to that before the frame was created.
 163    On return reinit_frame_cache has been called.
 164    If the frame isn't found, flag an internal error.  */
 165
 166 void
 167 dummy_frame_pop (struct frame_id dummy_id, ptid_t ptid)
 168 {
 169   struct dummy_frame **dp;
 170   struct dummy_frame_id id = { dummy_id, ptid };
 171
 172   dp = lookup_dummy_frame (&id);
 173   gdb_assert (dp != NULL);
 174
 175   pop_dummy_frame (dp);
 176 }
 177
 178 /* Find the dummy frame by DUMMY_ID and PTID and drop it.  Do nothing
 179    if it is not found.  Do not restore its state into inferior, just
 180    free its memory.  */
 181
 182 void
 183 dummy_frame_discard (struct frame_id dummy_id, ptid_t ptid)
 184 {
 185   struct dummy_frame **dp;
 186   struct dummy_frame_id id = { dummy_id, ptid };
 187
 188   dp = lookup_dummy_frame (&id);
 189   if (dp)
 190     remove_dummy_frame (dp);
 191 }
 192
 193 /* There may be stale dummy frames, perhaps left over from when an uncaught
 194    longjmp took us out of a function that was called by the debugger.  Clean
 195    them up at least once whenever we start a new inferior.  */
 196
 197 static void
 198 cleanup_dummy_frames (struct target_ops *target, int from_tty)
 199 {
 200   while (dummy_frame_stack != NULL)
 201     remove_dummy_frame (&dummy_frame_stack);
 202 }
 203
 204 /* Return the dummy frame cache, it contains both the ID, and a
 205    pointer to the regcache.  */
 206 struct dummy_frame_cache
 207 {
 208   struct frame_id this_id;
 209   struct regcache *prev_regcache;
 210 };
 211
 212 static int
 213 dummy_frame_sniffer (const struct frame_unwind *self,
 214                      struct frame_info *this_frame,
 215                      void **this_prologue_cache)
 216 {
 217   /* When unwinding a normal frame, the stack structure is determined
 218      by analyzing the frame's function's code (be it using brute force
 219      prologue analysis, or the dwarf2 CFI).  In the case of a dummy
 220      frame, that simply isn't possible.  The PC is either the program
 221      entry point, or some random address on the stack.  Trying to use
 222      that PC to apply standard frame ID unwind techniques is just
 223      asking for trouble.  */
 224
 225   /* Don't bother unless there is at least one dummy frame.  */
 226   if (dummy_frame_stack != NULL)
 227     {
 228       struct dummy_frame *dummyframe;
 229       /* Use an architecture specific method to extract this frame's
 230          dummy ID, assuming it is a dummy frame.  */
 231       struct frame_id this_id
 232         = gdbarch_dummy_id (get_frame_arch (this_frame), this_frame);
 233       struct dummy_frame_id dummy_id = { this_id, inferior_ptid };
 234
 235       /* Use that ID to find the corresponding cache entry.  */
 236       for (dummyframe = dummy_frame_stack;
 237            dummyframe != NULL;
 238            dummyframe = dummyframe->next)
 239         {
 240           if (dummy_frame_id_eq (&dummyframe->id, &dummy_id))
 241             {
 242               struct dummy_frame_cache *cache;
 243
 244               cache = FRAME_OBSTACK_ZALLOC (struct dummy_frame_cache);
 245               cache->prev_regcache = get_infcall_suspend_state_regcache
 246                                                    (dummyframe->caller_state);
 247               cache->this_id = this_id;
 248               (*this_prologue_cache) = cache;
 249               return 1;
 250             }
 251         }
 252     }
 253   return 0;
 254 }
 255
 256 /* Given a call-dummy dummy-frame, return the registers.  Here the
 257    register value is taken from the local copy of the register buffer.  */
 258
 259 static struct value *
 260 dummy_frame_prev_register (struct frame_info *this_frame,
 261                            void **this_prologue_cache,
 262                            int regnum)
 263 {
 264   struct dummy_frame_cache *cache = (*this_prologue_cache);
 265   struct gdbarch *gdbarch = get_frame_arch (this_frame);
 266   struct value *reg_val;
 267
 268   /* The dummy-frame sniffer always fills in the cache.  */
 269   gdb_assert (cache != NULL);
 270
 271   /* Describe the register's location.  Generic dummy frames always
 272      have the register value in an ``expression''.  */
 273   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 274
 275   /* Use the regcache_cooked_read() method so that it, on the fly,
 276      constructs either a raw or pseudo register from the raw
 277      register cache.  */
 278   regcache_cooked_read (cache->prev_regcache, regnum,
 279                         value_contents_writeable (reg_val));
 280   return reg_val;
 281 }
 282
 283 /* Assuming that THIS_FRAME is a dummy, return its ID.  That ID is
 284    determined by examining the NEXT frame's unwound registers using
 285    the method dummy_id().  As a side effect, THIS dummy frame's
 286    dummy cache is located and saved in THIS_PROLOGUE_CACHE.  */
 287
 288 static void
 289 dummy_frame_this_id (struct frame_info *this_frame,
 290                      void **this_prologue_cache,
 291                      struct frame_id *this_id)
 292 {
 293   /* The dummy-frame sniffer always fills in the cache.  */
 294   struct dummy_frame_cache *cache = (*this_prologue_cache);
 295
 296   gdb_assert (cache != NULL);
 297   (*this_id) = cache->this_id;
 298 }
 299
 300 const struct frame_unwind dummy_frame_unwind =
 301 {
 302   DUMMY_FRAME,
 303   default_frame_unwind_stop_reason,
 304   dummy_frame_this_id,
 305   dummy_frame_prev_register,
 306   NULL,
 307   dummy_frame_sniffer,
 308 };
 309
 310 static void
 311 fprint_dummy_frames (struct ui_file *file)
 312 {
 313   struct dummy_frame *s;
 314
 315   for (s = dummy_frame_stack; s != NULL; s = s->next)
 316     {
 317       gdb_print_host_address (s, file);
 318       fprintf_unfiltered (file, ":");
 319       fprintf_unfiltered (file, " id=");
 320       fprint_frame_id (file, s->id.id);
 321       fprintf_unfiltered (file, ", ptid=%s",
 322                           target_pid_to_str (s->id.ptid));
 323       fprintf_unfiltered (file, "\n");
 324     }
 325 }
 326
 327 static void
 328 maintenance_print_dummy_frames (char *args, int from_tty)
 329 {
 330   if (args == NULL)
 331     fprint_dummy_frames (gdb_stdout);
 332   else
 333     {
 334       struct cleanup *cleanups;
 335       struct ui_file *file = gdb_fopen (args, "w");
 336
 337       if (file == NULL)
 338         perror_with_name (_("maintenance print dummy-frames"));
 339       cleanups = make_cleanup_ui_file_delete (file);
 340       fprint_dummy_frames (file);
 341       do_cleanups (cleanups);
 342     }
 343 }
 344
 345 extern void _initialize_dummy_frame (void);
 346
 347 void
 348 _initialize_dummy_frame (void)
 349 {
 350   add_cmd ("dummy-frames", class_maintenance, maintenance_print_dummy_frames,
 351            _("Print the contents of the internal dummy-frame stack."),
 352            &maintenanceprintlist);
 353
 354   observer_attach_inferior_created (cleanup_dummy_frames);
 355 }