gdb/dummy-frame.c

   1 /* Code dealing with dummy stack frames, for GDB, the GNU debugger.
   2
   3    Copyright (C) 1986-2013 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 /* Dummy frame.  This saves the processor state just prior to setting
  35    up the inferior function call.  Older targets save the registers
  36    on the target stack (but that really slows down function calls).  */
  37
  38 struct dummy_frame
  39 {
  40   struct dummy_frame *next;
  41   /* This frame's ID.  Must match the value returned by
  42      gdbarch_dummy_id.  */
  43   struct frame_id id;
  44   /* The caller's state prior to the call.  */
  45   struct infcall_suspend_state *caller_state;
  46 };
  47
  48 static struct dummy_frame *dummy_frame_stack = NULL;
  49
  50 /* Push the caller's state, along with the dummy frame info, onto the
  51    dummy-frame stack.  */
  52
  53 void
  54 dummy_frame_push (struct infcall_suspend_state *caller_state,
  55                   const struct frame_id *dummy_id)
  56 {
  57   struct dummy_frame *dummy_frame;
  58
  59   dummy_frame = XZALLOC (struct dummy_frame);
  60   dummy_frame->caller_state = caller_state;
  61   dummy_frame->id = (*dummy_id);
  62   dummy_frame->next = dummy_frame_stack;
  63   dummy_frame_stack = dummy_frame;
  64 }
  65
  66 /* Remove *DUMMY_PTR from the dummy frame stack.  */
  67
  68 static void
  69 remove_dummy_frame (struct dummy_frame **dummy_ptr)
  70 {
  71   struct dummy_frame *dummy = *dummy_ptr;
  72
  73   *dummy_ptr = dummy->next;
  74   discard_infcall_suspend_state (dummy->caller_state);
  75   xfree (dummy);
  76 }
  77
  78 /* Delete any breakpoint B which is a momentary breakpoint for return from
  79    inferior call matching DUMMY_VOIDP.  */
  80
  81 static int
  82 pop_dummy_frame_bpt (struct breakpoint *b, void *dummy_voidp)
  83 {
  84   struct dummy_frame *dummy = dummy_voidp;
  85
  86   if (b->thread == pid_to_thread_id (inferior_ptid)
  87       && b->disposition == disp_del && frame_id_eq (b->frame_id, dummy->id))
  88     {
  89       while (b->related_breakpoint != b)
  90         delete_breakpoint (b->related_breakpoint);
  91
  92       delete_breakpoint (b);
  93
  94       /* Stop the traversal.  */
  95       return 1;
  96     }
  97
  98   /* Continue the traversal.  */
  99   return 0;
 100 }
 101
 102 /* Pop *DUMMY_PTR, restoring program state to that before the
 103    frame was created.  */
 104
 105 static void
 106 pop_dummy_frame (struct dummy_frame **dummy_ptr)
 107 {
 108   struct dummy_frame *dummy = *dummy_ptr;
 109
 110   restore_infcall_suspend_state (dummy->caller_state);
 111
 112   iterate_over_breakpoints (pop_dummy_frame_bpt, dummy);
 113
 114   /* restore_infcall_control_state frees inf_state,
 115      all that remains is to pop *dummy_ptr.  */
 116   *dummy_ptr = dummy->next;
 117   xfree (dummy);
 118
 119   /* We've made right mess of GDB's local state, just discard
 120      everything.  */
 121   reinit_frame_cache ();
 122 }
 123
 124 /* Look up DUMMY_ID.
 125    Return NULL if not found.  */
 126
 127 static struct dummy_frame **
 128 lookup_dummy_frame (struct frame_id dummy_id)
 129 {
 130   struct dummy_frame **dp;
 131
 132   for (dp = &dummy_frame_stack; *dp != NULL; dp = &(*dp)->next)
 133     {
 134       if (frame_id_eq ((*dp)->id, dummy_id))
 135         return dp;
 136     }
 137
 138   return NULL;
 139 }
 140
 141 /* Pop the dummy frame DUMMY_ID, restoring program state to that before the
 142    frame was created.
 143    On return reinit_frame_cache has been called.
 144    If the frame isn't found, flag an internal error.
 145
 146    NOTE: This can only pop the one frame, even if it is in the middle of the
 147    stack, because the other frames may be for different threads, and there's
 148    currently no way to tell which stack frame is for which thread.  */
 149
 150 void
 151 dummy_frame_pop (struct frame_id dummy_id)
 152 {
 153   struct dummy_frame **dp;
 154
 155   dp = lookup_dummy_frame (dummy_id);
 156   gdb_assert (dp != NULL);
 157
 158   pop_dummy_frame (dp);
 159 }
 160
 161 /* Drop dummy frame DUMMY_ID.  Do nothing if it is not found.  Do not restore
 162    its state into inferior, just free its memory.  */
 163
 164 void
 165 dummy_frame_discard (struct frame_id dummy_id)
 166 {
 167   struct dummy_frame **dp;
 168
 169   dp = lookup_dummy_frame (dummy_id);
 170   if (dp)
 171     remove_dummy_frame (dp);
 172 }
 173
 174 /* There may be stale dummy frames, perhaps left over from when an uncaught
 175    longjmp took us out of a function that was called by the debugger.  Clean
 176    them up at least once whenever we start a new inferior.  */
 177
 178 static void
 179 cleanup_dummy_frames (struct target_ops *target, int from_tty)
 180 {
 181   while (dummy_frame_stack != NULL)
 182     remove_dummy_frame (&dummy_frame_stack);
 183 }
 184
 185 /* Return the dummy frame cache, it contains both the ID, and a
 186    pointer to the regcache.  */
 187 struct dummy_frame_cache
 188 {
 189   struct frame_id this_id;
 190   struct regcache *prev_regcache;
 191 };
 192
 193 static int
 194 dummy_frame_sniffer (const struct frame_unwind *self,
 195                      struct frame_info *this_frame,
 196                      void **this_prologue_cache)
 197 {
 198   struct dummy_frame *dummyframe;
 199   struct frame_id this_id;
 200
 201   /* When unwinding a normal frame, the stack structure is determined
 202      by analyzing the frame's function's code (be it using brute force
 203      prologue analysis, or the dwarf2 CFI).  In the case of a dummy
 204      frame, that simply isn't possible.  The PC is either the program
 205      entry point, or some random address on the stack.  Trying to use
 206      that PC to apply standard frame ID unwind techniques is just
 207      asking for trouble.  */
 208
 209   /* Don't bother unless there is at least one dummy frame.  */
 210   if (dummy_frame_stack != NULL)
 211     {
 212       /* Use an architecture specific method to extract this frame's
 213          dummy ID, assuming it is a dummy frame.  */
 214       this_id = gdbarch_dummy_id (get_frame_arch (this_frame), this_frame);
 215
 216       /* Use that ID to find the corresponding cache entry.  */
 217       for (dummyframe = dummy_frame_stack;
 218            dummyframe != NULL;
 219            dummyframe = dummyframe->next)
 220         {
 221           if (frame_id_eq (dummyframe->id, this_id))
 222             {
 223               struct dummy_frame_cache *cache;
 224
 225               cache = FRAME_OBSTACK_ZALLOC (struct dummy_frame_cache);
 226               cache->prev_regcache = get_infcall_suspend_state_regcache
 227                                                    (dummyframe->caller_state);
 228               cache->this_id = this_id;
 229               (*this_prologue_cache) = cache;
 230               return 1;
 231             }
 232         }
 233     }
 234   return 0;
 235 }
 236
 237 /* Given a call-dummy dummy-frame, return the registers.  Here the
 238    register value is taken from the local copy of the register buffer.  */
 239
 240 static struct value *
 241 dummy_frame_prev_register (struct frame_info *this_frame,
 242                            void **this_prologue_cache,
 243                            int regnum)
 244 {
 245   struct dummy_frame_cache *cache = (*this_prologue_cache);
 246   struct gdbarch *gdbarch = get_frame_arch (this_frame);
 247   struct value *reg_val;
 248
 249   /* The dummy-frame sniffer always fills in the cache.  */
 250   gdb_assert (cache != NULL);
 251
 252   /* Describe the register's location.  Generic dummy frames always
 253      have the register value in an ``expression''.  */
 254   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 255
 256   /* Use the regcache_cooked_read() method so that it, on the fly,
 257      constructs either a raw or pseudo register from the raw
 258      register cache.  */
 259   regcache_cooked_read (cache->prev_regcache, regnum,
 260                         value_contents_writeable (reg_val));
 261   return reg_val;
 262 }
 263
 264 /* Assuming that THIS_FRAME is a dummy, return its ID.  That ID is
 265    determined by examining the NEXT frame's unwound registers using
 266    the method dummy_id().  As a side effect, THIS dummy frame's
 267    dummy cache is located and saved in THIS_PROLOGUE_CACHE.  */
 268
 269 static void
 270 dummy_frame_this_id (struct frame_info *this_frame,
 271                      void **this_prologue_cache,
 272                      struct frame_id *this_id)
 273 {
 274   /* The dummy-frame sniffer always fills in the cache.  */
 275   struct dummy_frame_cache *cache = (*this_prologue_cache);
 276
 277   gdb_assert (cache != NULL);
 278   (*this_id) = cache->this_id;
 279 }
 280
 281 const struct frame_unwind dummy_frame_unwind =
 282 {
 283   DUMMY_FRAME,
 284   default_frame_unwind_stop_reason,
 285   dummy_frame_this_id,
 286   dummy_frame_prev_register,
 287   NULL,
 288   dummy_frame_sniffer,
 289 };
 290
 291 static void
 292 fprint_dummy_frames (struct ui_file *file)
 293 {
 294   struct dummy_frame *s;
 295
 296   for (s = dummy_frame_stack; s != NULL; s = s->next)
 297     {
 298       gdb_print_host_address (s, file);
 299       fprintf_unfiltered (file, ":");
 300       fprintf_unfiltered (file, " id=");
 301       fprint_frame_id (file, s->id);
 302       fprintf_unfiltered (file, "\n");
 303     }
 304 }
 305
 306 static void
 307 maintenance_print_dummy_frames (char *args, int from_tty)
 308 {
 309   if (args == NULL)
 310     fprint_dummy_frames (gdb_stdout);
 311   else
 312     {
 313       struct cleanup *cleanups;
 314       struct ui_file *file = gdb_fopen (args, "w");
 315
 316       if (file == NULL)
 317         perror_with_name (_("maintenance print dummy-frames"));
 318       cleanups = make_cleanup_ui_file_delete (file);
 319       fprint_dummy_frames (file);
 320       do_cleanups (cleanups);
 321     }
 322 }
 323
 324 extern void _initialize_dummy_frame (void);
 325
 326 void
 327 _initialize_dummy_frame (void)
 328 {
 329   add_cmd ("dummy-frames", class_maintenance, maintenance_print_dummy_frames,
 330            _("Print the contents of the internal dummy-frame stack."),
 331            &maintenanceprintlist);
 332
 333   observer_attach_inferior_created (cleanup_dummy_frames);
 334 }