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 "gdb_assert.h"
  27 #include "frame-unwind.h"
  28 #include "command.h"
  29 #include "gdbcmd.h"
  30 #include <string.h>
  31 #include "observer.h"
  32 #include "gdbthread.h"
  33
  34 struct dummy_frame_id
  35 {
  36   /* This frame's ID.  Must match the value returned by
  37      gdbarch_dummy_id.  */
  38   struct frame_id id;
  39
  40   /* The thread this dummy_frame relates to.  */
  41   ptid_t ptid;
  42 };
  43
  44 /* Return whether dummy_frame_id *ID1 and *ID2 are equal.  */
  45
  46 static int
  47 dummy_frame_id_eq (struct dummy_frame_id *id1,
  48                    struct dummy_frame_id *id2)
  49 {
  50   return frame_id_eq (id1->id, id2->id) && ptid_equal (id1->ptid, id2->ptid);
  51 }
  52
  53 /* Dummy frame.  This saves the processor state just prior to setting
  54    up the inferior function call.  Older targets save the registers
  55    on the target stack (but that really slows down function calls).  */
  56
  57 struct dummy_frame
  58 {
  59   struct dummy_frame *next;
  60
  61   /* An id represents a dummy frame.  */
  62   struct dummy_frame_id id;
  63
  64   /* The caller's state prior to the call.  */
  65   struct infcall_suspend_state *caller_state;
  66 };
  67
  68 static struct dummy_frame *dummy_frame_stack = NULL;
  69
  70 /* Push the caller's state, along with the dummy frame info, onto the
  71    dummy-frame stack.  */
  72
  73 void
  74 dummy_frame_push (struct infcall_suspend_state *caller_state,
  75                   const struct frame_id *dummy_id, ptid_t ptid)
  76 {
  77   struct dummy_frame *dummy_frame;
  78
  79   dummy_frame = XCNEW (struct dummy_frame);
  80   dummy_frame->caller_state = caller_state;
  81   dummy_frame->id.id = (*dummy_id);
  82   dummy_frame->id.ptid = ptid;
  83   dummy_frame->next = dummy_frame_stack;
  84   dummy_frame_stack = dummy_frame;
  85 }
  86
  87 /* Remove *DUMMY_PTR from the dummy frame stack.  */
  88
  89 static void
  90 remove_dummy_frame (struct dummy_frame **dummy_ptr)
  91 {
  92   struct dummy_frame *dummy = *dummy_ptr;
  93
  94   *dummy_ptr = dummy->next;
  95   discard_infcall_suspend_state (dummy->caller_state);
  96   xfree (dummy);
  97 }
  98
  99 /* Delete any breakpoint B which is a momentary breakpoint for return from
 100    inferior call matching DUMMY_VOIDP.  */
 101
 102 static int
 103 pop_dummy_frame_bpt (struct breakpoint *b, void *dummy_voidp)
 104 {
 105   struct dummy_frame *dummy = dummy_voidp;
 106
 107   if (b->thread == pid_to_thread_id (dummy->id.ptid)
 108       && b->disposition == disp_del && frame_id_eq (b->frame_id, dummy->id.id))
 109     {
 110       while (b->related_breakpoint != b)
 111         delete_breakpoint (b->related_breakpoint);
 112
 113       delete_breakpoint (b);
 114
 115       /* Stop the traversal.  */
 116       return 1;
 117     }
 118
 119   /* Continue the traversal.  */
 120   return 0;
 121 }
 122
 123 /* Pop *DUMMY_PTR, restoring program state to that before the
 124    frame was created.  */
 125
 126 static void
 127 pop_dummy_frame (struct dummy_frame **dummy_ptr)
 128 {
 129   struct dummy_frame *dummy = *dummy_ptr;
 130
 131   gdb_assert (ptid_equal (dummy->id.ptid, inferior_ptid));
 132   restore_infcall_suspend_state (dummy->caller_state);
 133
 134   iterate_over_breakpoints (pop_dummy_frame_bpt, dummy);
 135
 136   /* restore_infcall_control_state frees inf_state,
 137      all that remains is to pop *dummy_ptr.  */
 138   *dummy_ptr = dummy->next;
 139   xfree (dummy);
 140
 141   /* We've made right mess of GDB's local state, just discard
 142      everything.  */
 143   reinit_frame_cache ();
 144 }
 145
 146 /* Look up DUMMY_ID.
 147    Return NULL if not found.  */
 148
 149 static struct dummy_frame **
 150 lookup_dummy_frame (struct dummy_frame_id *dummy_id)
 151 {
 152   struct dummy_frame **dp;
 153
 154   for (dp = &dummy_frame_stack; *dp != NULL; dp = &(*dp)->next)
 155     {
 156       if (dummy_frame_id_eq (&(*dp)->id, dummy_id))
 157         return dp;
 158     }
 159
 160   return NULL;
 161 }
 162
 163 /* Find the dummy frame by DUMMY_ID and PTID, and pop it, restoring
 164    program state to that before the frame was created.
 165    On return reinit_frame_cache has been called.
 166    If the frame isn't found, flag an internal error.  */
 167
 168 void
 169 dummy_frame_pop (struct frame_id dummy_id, ptid_t ptid)
 170 {
 171   struct dummy_frame **dp;
 172   struct dummy_frame_id id = { dummy_id, ptid };
 173
 174   dp = lookup_dummy_frame (&id);
 175   gdb_assert (dp != NULL);
 176
 177   pop_dummy_frame (dp);
 178 }
 179
 180 /* Find the dummy frame by DUMMY_ID and PTID and drop it.  Do nothing
 181    if it is not found.  Do not restore its state into inferior, just
 182    free its memory.  */
 183
 184 void
 185 dummy_frame_discard (struct frame_id dummy_id, ptid_t ptid)
 186 {
 187   struct dummy_frame **dp;
 188   struct dummy_frame_id id = { dummy_id, ptid };
 189
 190   dp = lookup_dummy_frame (&id);
 191   if (dp)
 192     remove_dummy_frame (dp);
 193 }
 194
 195 /* There may be stale dummy frames, perhaps left over from when an uncaught
 196    longjmp took us out of a function that was called by the debugger.  Clean
 197    them up at least once whenever we start a new inferior.  */
 198
 199 static void
 200 cleanup_dummy_frames (struct target_ops *target, int from_tty)
 201 {
 202   while (dummy_frame_stack != NULL)
 203     remove_dummy_frame (&dummy_frame_stack);
 204 }
 205
 206 /* Return the dummy frame cache, it contains both the ID, and a
 207    pointer to the regcache.  */
 208 struct dummy_frame_cache
 209 {
 210   struct frame_id this_id;
 211   struct regcache *prev_regcache;
 212 };
 213
 214 static int
 215 dummy_frame_sniffer (const struct frame_unwind *self,
 216                      struct frame_info *this_frame,
 217                      void **this_prologue_cache)
 218 {
 219   /* When unwinding a normal frame, the stack structure is determined
 220      by analyzing the frame's function's code (be it using brute force
 221      prologue analysis, or the dwarf2 CFI).  In the case of a dummy
 222      frame, that simply isn't possible.  The PC is either the program
 223      entry point, or some random address on the stack.  Trying to use
 224      that PC to apply standard frame ID unwind techniques is just
 225      asking for trouble.  */
 226
 227   /* Don't bother unless there is at least one dummy frame.  */
 228   if (dummy_frame_stack != NULL)
 229     {
 230       struct dummy_frame *dummyframe;
 231       /* Use an architecture specific method to extract this frame's
 232          dummy ID, assuming it is a dummy frame.  */
 233       struct frame_id this_id
 234         = gdbarch_dummy_id (get_frame_arch (this_frame), this_frame);
 235       struct dummy_frame_id dummy_id = { this_id, inferior_ptid };
 236
 237       /* Use that ID to find the corresponding cache entry.  */
 238       for (dummyframe = dummy_frame_stack;
 239            dummyframe != NULL;
 240            dummyframe = dummyframe->next)
 241         {
 242           if (dummy_frame_id_eq (&dummyframe->id, &dummy_id))
 243             {
 244               struct dummy_frame_cache *cache;
 245
 246               cache = FRAME_OBSTACK_ZALLOC (struct dummy_frame_cache);
 247               cache->prev_regcache = get_infcall_suspend_state_regcache
 248                                                    (dummyframe->caller_state);
 249               cache->this_id = this_id;
 250               (*this_prologue_cache) = cache;
 251               return 1;
 252             }
 253         }
 254     }
 255   return 0;
 256 }
 257
 258 /* Given a call-dummy dummy-frame, return the registers.  Here the
 259    register value is taken from the local copy of the register buffer.  */
 260
 261 static struct value *
 262 dummy_frame_prev_register (struct frame_info *this_frame,
 263                            void **this_prologue_cache,
 264                            int regnum)
 265 {
 266   struct dummy_frame_cache *cache = (*this_prologue_cache);
 267   struct gdbarch *gdbarch = get_frame_arch (this_frame);
 268   struct value *reg_val;
 269
 270   /* The dummy-frame sniffer always fills in the cache.  */
 271   gdb_assert (cache != NULL);
 272
 273   /* Describe the register's location.  Generic dummy frames always
 274      have the register value in an ``expression''.  */
 275   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 276
 277   /* Use the regcache_cooked_read() method so that it, on the fly,
 278      constructs either a raw or pseudo register from the raw
 279      register cache.  */
 280   regcache_cooked_read (cache->prev_regcache, regnum,
 281                         value_contents_writeable (reg_val));
 282   return reg_val;
 283 }
 284
 285 /* Assuming that THIS_FRAME is a dummy, return its ID.  That ID is
 286    determined by examining the NEXT frame's unwound registers using
 287    the method dummy_id().  As a side effect, THIS dummy frame's
 288    dummy cache is located and saved in THIS_PROLOGUE_CACHE.  */
 289
 290 static void
 291 dummy_frame_this_id (struct frame_info *this_frame,
 292                      void **this_prologue_cache,
 293                      struct frame_id *this_id)
 294 {
 295   /* The dummy-frame sniffer always fills in the cache.  */
 296   struct dummy_frame_cache *cache = (*this_prologue_cache);
 297
 298   gdb_assert (cache != NULL);
 299   (*this_id) = cache->this_id;
 300 }
 301
 302 const struct frame_unwind dummy_frame_unwind =
 303 {
 304   DUMMY_FRAME,
 305   default_frame_unwind_stop_reason,
 306   dummy_frame_this_id,
 307   dummy_frame_prev_register,
 308   NULL,
 309   dummy_frame_sniffer,
 310 };
 311
 312 static void
 313 fprint_dummy_frames (struct ui_file *file)
 314 {
 315   struct dummy_frame *s;
 316
 317   for (s = dummy_frame_stack; s != NULL; s = s->next)
 318     {
 319       gdb_print_host_address (s, file);
 320       fprintf_unfiltered (file, ":");
 321       fprintf_unfiltered (file, " id=");
 322       fprint_frame_id (file, s->id.id);
 323       fprintf_unfiltered (file, ", ptid=%s",
 324                           target_pid_to_str (s->id.ptid));
 325       fprintf_unfiltered (file, "\n");
 326     }
 327 }
 328
 329 static void
 330 maintenance_print_dummy_frames (char *args, int from_tty)
 331 {
 332   if (args == NULL)
 333     fprint_dummy_frames (gdb_stdout);
 334   else
 335     {
 336       struct cleanup *cleanups;
 337       struct ui_file *file = gdb_fopen (args, "w");
 338
 339       if (file == NULL)
 340         perror_with_name (_("maintenance print dummy-frames"));
 341       cleanups = make_cleanup_ui_file_delete (file);
 342       fprint_dummy_frames (file);
 343       do_cleanups (cleanups);
 344     }
 345 }
 346
 347 extern void _initialize_dummy_frame (void);
 348
 349 void
 350 _initialize_dummy_frame (void)
 351 {
 352   add_cmd ("dummy-frames", class_maintenance, maintenance_print_dummy_frames,
 353            _("Print the contents of the internal dummy-frame stack."),
 354            &maintenanceprintlist);
 355
 356   observer_attach_inferior_created (cleanup_dummy_frames);
 357 }