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 <string.h>
  30 #include "observer.h"
  31 #include "gdbthread.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
  67 static struct dummy_frame *dummy_frame_stack = NULL;
  68
  69 /* Push the caller's state, along with the dummy frame info, onto the
  70    dummy-frame stack.  */
  71
  72 void
  73 dummy_frame_push (struct infcall_suspend_state *caller_state,
  74                   const struct frame_id *dummy_id, ptid_t ptid)
  75 {
  76   struct dummy_frame *dummy_frame;
  77
  78   dummy_frame = XCNEW (struct dummy_frame);
  79   dummy_frame->caller_state = caller_state;
  80   dummy_frame->id.id = (*dummy_id);
  81   dummy_frame->id.ptid = ptid;
  82   dummy_frame->next = dummy_frame_stack;
  83   dummy_frame_stack = dummy_frame;
  84 }
  85
  86 /* Remove *DUMMY_PTR from the dummy frame stack.  */
  87
  88 static void
  89 remove_dummy_frame (struct dummy_frame **dummy_ptr)
  90 {
  91   struct dummy_frame *dummy = *dummy_ptr;
  92
  93   *dummy_ptr = dummy->next;
  94   discard_infcall_suspend_state (dummy->caller_state);
  95   xfree (dummy);
  96 }
  97
  98 /* Delete any breakpoint B which is a momentary breakpoint for return from
  99    inferior call matching DUMMY_VOIDP.  */
 100
 101 static int
 102 pop_dummy_frame_bpt (struct breakpoint *b, void *dummy_voidp)
 103 {
 104   struct dummy_frame *dummy = dummy_voidp;
 105
 106   if (b->thread == pid_to_thread_id (dummy->id.ptid)
 107       && b->disposition == disp_del && frame_id_eq (b->frame_id, dummy->id.id))
 108     {
 109       while (b->related_breakpoint != b)
 110         delete_breakpoint (b->related_breakpoint);
 111
 112       delete_breakpoint (b);
 113
 114       /* Stop the traversal.  */
 115       return 1;
 116     }
 117
 118   /* Continue the traversal.  */
 119   return 0;
 120 }
 121
 122 /* Pop *DUMMY_PTR, restoring program state to that before the
 123    frame was created.  */
 124
 125 static void
 126 pop_dummy_frame (struct dummy_frame **dummy_ptr)
 127 {
 128   struct dummy_frame *dummy = *dummy_ptr;
 129
 130   gdb_assert (ptid_equal (dummy->id.ptid, inferior_ptid));
 131   restore_infcall_suspend_state (dummy->caller_state);
 132
 133   iterate_over_breakpoints (pop_dummy_frame_bpt, dummy);
 134
 135   /* restore_infcall_control_state frees inf_state,
 136      all that remains is to pop *dummy_ptr.  */
 137   *dummy_ptr = dummy->next;
 138   xfree (dummy);
 139
 140   /* We've made right mess of GDB's local state, just discard
 141      everything.  */
 142   reinit_frame_cache ();
 143 }
 144
 145 /* Look up DUMMY_ID.
 146    Return NULL if not found.  */
 147
 148 static struct dummy_frame **
 149 lookup_dummy_frame (struct dummy_frame_id *dummy_id)
 150 {
 151   struct dummy_frame **dp;
 152
 153   for (dp = &dummy_frame_stack; *dp != NULL; dp = &(*dp)->next)
 154     {
 155       if (dummy_frame_id_eq (&(*dp)->id, dummy_id))
 156         return dp;
 157     }
 158
 159   return NULL;
 160 }
 161
 162 /* Find the dummy frame by DUMMY_ID and PTID, and pop it, restoring
 163    program state to that before the frame was created.
 164    On return reinit_frame_cache has been called.
 165    If the frame isn't found, flag an internal error.  */
 166
 167 void
 168 dummy_frame_pop (struct frame_id dummy_id, ptid_t ptid)
 169 {
 170   struct dummy_frame **dp;
 171   struct dummy_frame_id id = { dummy_id, ptid };
 172
 173   dp = lookup_dummy_frame (&id);
 174   gdb_assert (dp != NULL);
 175
 176   pop_dummy_frame (dp);
 177 }
 178
 179 /* Find the dummy frame by DUMMY_ID and PTID and drop it.  Do nothing
 180    if it is not found.  Do not restore its state into inferior, just
 181    free its memory.  */
 182
 183 void
 184 dummy_frame_discard (struct frame_id dummy_id, ptid_t ptid)
 185 {
 186   struct dummy_frame **dp;
 187   struct dummy_frame_id id = { dummy_id, ptid };
 188
 189   dp = lookup_dummy_frame (&id);
 190   if (dp)
 191     remove_dummy_frame (dp);
 192 }
 193
 194 /* There may be stale dummy frames, perhaps left over from when an uncaught
 195    longjmp took us out of a function that was called by the debugger.  Clean
 196    them up at least once whenever we start a new inferior.  */
 197
 198 static void
 199 cleanup_dummy_frames (struct target_ops *target, int from_tty)
 200 {
 201   while (dummy_frame_stack != NULL)
 202     remove_dummy_frame (&dummy_frame_stack);
 203 }
 204
 205 /* Return the dummy frame cache, it contains both the ID, and a
 206    pointer to the regcache.  */
 207 struct dummy_frame_cache
 208 {
 209   struct frame_id this_id;
 210   struct regcache *prev_regcache;
 211 };
 212
 213 static int
 214 dummy_frame_sniffer (const struct frame_unwind *self,
 215                      struct frame_info *this_frame,
 216                      void **this_prologue_cache)
 217 {
 218   /* When unwinding a normal frame, the stack structure is determined
 219      by analyzing the frame's function's code (be it using brute force
 220      prologue analysis, or the dwarf2 CFI).  In the case of a dummy
 221      frame, that simply isn't possible.  The PC is either the program
 222      entry point, or some random address on the stack.  Trying to use
 223      that PC to apply standard frame ID unwind techniques is just
 224      asking for trouble.  */
 225
 226   /* Don't bother unless there is at least one dummy frame.  */
 227   if (dummy_frame_stack != NULL)
 228     {
 229       struct dummy_frame *dummyframe;
 230       /* Use an architecture specific method to extract this frame's
 231          dummy ID, assuming it is a dummy frame.  */
 232       struct frame_id this_id
 233         = gdbarch_dummy_id (get_frame_arch (this_frame), this_frame);
 234       struct dummy_frame_id dummy_id = { this_id, inferior_ptid };
 235
 236       /* Use that ID to find the corresponding cache entry.  */
 237       for (dummyframe = dummy_frame_stack;
 238            dummyframe != NULL;
 239            dummyframe = dummyframe->next)
 240         {
 241           if (dummy_frame_id_eq (&dummyframe->id, &dummy_id))
 242             {
 243               struct dummy_frame_cache *cache;
 244
 245               cache = FRAME_OBSTACK_ZALLOC (struct dummy_frame_cache);
 246               cache->prev_regcache = get_infcall_suspend_state_regcache
 247                                                    (dummyframe->caller_state);
 248               cache->this_id = this_id;
 249               (*this_prologue_cache) = cache;
 250               return 1;
 251             }
 252         }
 253     }
 254   return 0;
 255 }
 256
 257 /* Given a call-dummy dummy-frame, return the registers.  Here the
 258    register value is taken from the local copy of the register buffer.  */
 259
 260 static struct value *
 261 dummy_frame_prev_register (struct frame_info *this_frame,
 262                            void **this_prologue_cache,
 263                            int regnum)
 264 {
 265   struct dummy_frame_cache *cache = (*this_prologue_cache);
 266   struct gdbarch *gdbarch = get_frame_arch (this_frame);
 267   struct value *reg_val;
 268
 269   /* The dummy-frame sniffer always fills in the cache.  */
 270   gdb_assert (cache != NULL);
 271
 272   /* Describe the register's location.  Generic dummy frames always
 273      have the register value in an ``expression''.  */
 274   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 275
 276   /* Use the regcache_cooked_read() method so that it, on the fly,
 277      constructs either a raw or pseudo register from the raw
 278      register cache.  */
 279   regcache_cooked_read (cache->prev_regcache, regnum,
 280                         value_contents_writeable (reg_val));
 281   return reg_val;
 282 }
 283
 284 /* Assuming that THIS_FRAME is a dummy, return its ID.  That ID is
 285    determined by examining the NEXT frame's unwound registers using
 286    the method dummy_id().  As a side effect, THIS dummy frame's
 287    dummy cache is located and saved in THIS_PROLOGUE_CACHE.  */
 288
 289 static void
 290 dummy_frame_this_id (struct frame_info *this_frame,
 291                      void **this_prologue_cache,
 292                      struct frame_id *this_id)
 293 {
 294   /* The dummy-frame sniffer always fills in the cache.  */
 295   struct dummy_frame_cache *cache = (*this_prologue_cache);
 296
 297   gdb_assert (cache != NULL);
 298   (*this_id) = cache->this_id;
 299 }
 300
 301 const struct frame_unwind dummy_frame_unwind =
 302 {
 303   DUMMY_FRAME,
 304   default_frame_unwind_stop_reason,
 305   dummy_frame_this_id,
 306   dummy_frame_prev_register,
 307   NULL,
 308   dummy_frame_sniffer,
 309 };
 310
 311 static void
 312 fprint_dummy_frames (struct ui_file *file)
 313 {
 314   struct dummy_frame *s;
 315
 316   for (s = dummy_frame_stack; s != NULL; s = s->next)
 317     {
 318       gdb_print_host_address (s, file);
 319       fprintf_unfiltered (file, ":");
 320       fprintf_unfiltered (file, " id=");
 321       fprint_frame_id (file, s->id.id);
 322       fprintf_unfiltered (file, ", ptid=%s",
 323                           target_pid_to_str (s->id.ptid));
 324       fprintf_unfiltered (file, "\n");
 325     }
 326 }
 327
 328 static void
 329 maintenance_print_dummy_frames (char *args, int from_tty)
 330 {
 331   if (args == NULL)
 332     fprint_dummy_frames (gdb_stdout);
 333   else
 334     {
 335       struct cleanup *cleanups;
 336       struct ui_file *file = gdb_fopen (args, "w");
 337
 338       if (file == NULL)
 339         perror_with_name (_("maintenance print dummy-frames"));
 340       cleanups = make_cleanup_ui_file_delete (file);
 341       fprint_dummy_frames (file);
 342       do_cleanups (cleanups);
 343     }
 344 }
 345
 346 extern void _initialize_dummy_frame (void);
 347
 348 void
 349 _initialize_dummy_frame (void)
 350 {
 351   add_cmd ("dummy-frames", class_maintenance, maintenance_print_dummy_frames,
 352            _("Print the contents of the internal dummy-frame stack."),
 353            &maintenanceprintlist);
 354
 355   observer_attach_inferior_created (cleanup_dummy_frames);
 356 }