gdb/dummy-frame.c

   1 /* Code dealing with dummy stack frames, for GDB, the GNU debugger.
   2
   3    Copyright (C) 1986-2004, 2007-2012 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 "gdb_string.h"
  31 #include "observer.h"
  32
  33 /* Dummy frame.  This saves the processor state just prior to setting
  34    up the inferior function call.  Older targets save the registers
  35    on the target stack (but that really slows down function calls).  */
  36
  37 struct dummy_frame
  38 {
  39   struct dummy_frame *next;
  40   /* This frame's ID.  Must match the value returned by
  41      gdbarch_dummy_id.  */
  42   struct frame_id id;
  43   /* The caller's state prior to the call.  */
  44   struct infcall_suspend_state *caller_state;
  45 };
  46
  47 static struct dummy_frame *dummy_frame_stack = NULL;
  48
  49 /* Function: deprecated_pc_in_call_dummy (pc)
  50
  51    Return non-zero if the PC falls in a dummy frame created by gdb for
  52    an inferior call.  The code below which allows gdbarch_decr_pc_after_break
  53    is for infrun.c, which may give the function a PC without that
  54    subtracted out.
  55
  56    FIXME: cagney/2002-11-23: This is silly.  Surely "infrun.c" can
  57    figure out what the real PC (as in the resume address) is BEFORE
  58    calling this function.
  59
  60    NOTE: cagney/2004-08-02: I'm pretty sure that, with the introduction of
  61    infrun.c:adjust_pc_after_break (thanks), this function is now
  62    always called with a correctly adjusted PC!
  63
  64    NOTE: cagney/2004-08-02: Code should not need to call this.  */
  65
  66 int
  67 deprecated_pc_in_call_dummy (struct gdbarch *gdbarch, CORE_ADDR pc)
  68 {
  69   struct dummy_frame *dummyframe;
  70
  71   for (dummyframe = dummy_frame_stack;
  72        dummyframe != NULL;
  73        dummyframe = dummyframe->next)
  74     {
  75       if ((pc >= dummyframe->id.code_addr)
  76           && (pc <= dummyframe->id.code_addr
  77                     + gdbarch_decr_pc_after_break (gdbarch)))
  78         return 1;
  79     }
  80   return 0;
  81 }
  82
  83 /* Push the caller's state, along with the dummy frame info, onto the
  84    dummy-frame stack.  */
  85
  86 void
  87 dummy_frame_push (struct infcall_suspend_state *caller_state,
  88                   const struct frame_id *dummy_id)
  89 {
  90   struct dummy_frame *dummy_frame;
  91
  92   dummy_frame = XZALLOC (struct dummy_frame);
  93   dummy_frame->caller_state = caller_state;
  94   dummy_frame->id = (*dummy_id);
  95   dummy_frame->next = dummy_frame_stack;
  96   dummy_frame_stack = dummy_frame;
  97 }
  98
  99 /* Remove *DUMMY_PTR from the dummy frame stack.  */
 100
 101 static void
 102 remove_dummy_frame (struct dummy_frame **dummy_ptr)
 103 {
 104   struct dummy_frame *dummy = *dummy_ptr;
 105
 106   *dummy_ptr = dummy->next;
 107   discard_infcall_suspend_state (dummy->caller_state);
 108   xfree (dummy);
 109 }
 110
 111 /* Pop *DUMMY_PTR, restoring program state to that before the
 112    frame was created.  */
 113
 114 static void
 115 pop_dummy_frame (struct dummy_frame **dummy_ptr)
 116 {
 117   struct dummy_frame *dummy;
 118
 119   restore_infcall_suspend_state ((*dummy_ptr)->caller_state);
 120
 121   /* restore_infcall_control_state frees inf_state,
 122      all that remains is to pop *dummy_ptr.  */
 123   dummy = *dummy_ptr;
 124   *dummy_ptr = dummy->next;
 125   xfree (dummy);
 126
 127   /* We've made right mess of GDB's local state, just discard
 128      everything.  */
 129   reinit_frame_cache ();
 130 }
 131
 132 /* Look up DUMMY_ID.
 133    Return NULL if not found.  */
 134
 135 static struct dummy_frame **
 136 lookup_dummy_frame (struct frame_id dummy_id)
 137 {
 138   struct dummy_frame **dp;
 139
 140   for (dp = &dummy_frame_stack; *dp != NULL; dp = &(*dp)->next)
 141     {
 142       if (frame_id_eq ((*dp)->id, dummy_id))
 143         return dp;
 144     }
 145
 146   return NULL;
 147 }
 148
 149 /* Pop the dummy frame DUMMY_ID, restoring program state to that before the
 150    frame was created.
 151    On return reinit_frame_cache has been called.
 152    If the frame isn't found, flag an internal error.
 153
 154    NOTE: This can only pop the one frame, even if it is in the middle of the
 155    stack, because the other frames may be for different threads, and there's
 156    currently no way to tell which stack frame is for which thread.  */
 157
 158 void
 159 dummy_frame_pop (struct frame_id dummy_id)
 160 {
 161   struct dummy_frame **dp;
 162
 163   dp = lookup_dummy_frame (dummy_id);
 164   gdb_assert (dp != NULL);
 165
 166   pop_dummy_frame (dp);
 167 }
 168
 169 /* There may be stale dummy frames, perhaps left over from when a longjump took
 170    us out of a function that was called by the debugger.  Clean them up at
 171    least once whenever we start a new inferior.  */
 172
 173 static void
 174 cleanup_dummy_frames (struct target_ops *target, int from_tty)
 175 {
 176   while (dummy_frame_stack != NULL)
 177     remove_dummy_frame (&dummy_frame_stack);
 178 }
 179
 180 /* Return the dummy frame cache, it contains both the ID, and a
 181    pointer to the regcache.  */
 182 struct dummy_frame_cache
 183 {
 184   struct frame_id this_id;
 185   struct regcache *prev_regcache;
 186 };
 187
 188 static int
 189 dummy_frame_sniffer (const struct frame_unwind *self,
 190                      struct frame_info *this_frame,
 191                      void **this_prologue_cache)
 192 {
 193   struct dummy_frame *dummyframe;
 194   struct frame_id this_id;
 195
 196   /* When unwinding a normal frame, the stack structure is determined
 197      by analyzing the frame's function's code (be it using brute force
 198      prologue analysis, or the dwarf2 CFI).  In the case of a dummy
 199      frame, that simply isn't possible.  The PC is either the program
 200      entry point, or some random address on the stack.  Trying to use
 201      that PC to apply standard frame ID unwind techniques is just
 202      asking for trouble.  */
 203
 204   /* Don't bother unless there is at least one dummy frame.  */
 205   if (dummy_frame_stack != NULL)
 206     {
 207       /* Use an architecture specific method to extract this frame's
 208          dummy ID, assuming it is a dummy frame.  */
 209       this_id = gdbarch_dummy_id (get_frame_arch (this_frame), this_frame);
 210
 211       /* Use that ID to find the corresponding cache entry.  */
 212       for (dummyframe = dummy_frame_stack;
 213            dummyframe != NULL;
 214            dummyframe = dummyframe->next)
 215         {
 216           if (frame_id_eq (dummyframe->id, this_id))
 217             {
 218               struct dummy_frame_cache *cache;
 219
 220               cache = FRAME_OBSTACK_ZALLOC (struct dummy_frame_cache);
 221               cache->prev_regcache = get_infcall_suspend_state_regcache
 222                                                    (dummyframe->caller_state);
 223               cache->this_id = this_id;
 224               (*this_prologue_cache) = cache;
 225               return 1;
 226             }
 227         }
 228     }
 229   return 0;
 230 }
 231
 232 /* Given a call-dummy dummy-frame, return the registers.  Here the
 233    register value is taken from the local copy of the register buffer.  */
 234
 235 static struct value *
 236 dummy_frame_prev_register (struct frame_info *this_frame,
 237                            void **this_prologue_cache,
 238                            int regnum)
 239 {
 240   struct dummy_frame_cache *cache = (*this_prologue_cache);
 241   struct gdbarch *gdbarch = get_frame_arch (this_frame);
 242   struct value *reg_val;
 243
 244   /* The dummy-frame sniffer always fills in the cache.  */
 245   gdb_assert (cache != NULL);
 246
 247   /* Describe the register's location.  Generic dummy frames always
 248      have the register value in an ``expression''.  */
 249   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 250
 251   /* Use the regcache_cooked_read() method so that it, on the fly,
 252      constructs either a raw or pseudo register from the raw
 253      register cache.  */
 254   regcache_cooked_read (cache->prev_regcache, regnum,
 255                         value_contents_writeable (reg_val));
 256   return reg_val;
 257 }
 258
 259 /* Assuming that THIS_FRAME is a dummy, return its ID.  That ID is
 260    determined by examining the NEXT frame's unwound registers using
 261    the method dummy_id().  As a side effect, THIS dummy frame's
 262    dummy cache is located and saved in THIS_PROLOGUE_CACHE.  */
 263
 264 static void
 265 dummy_frame_this_id (struct frame_info *this_frame,
 266                      void **this_prologue_cache,
 267                      struct frame_id *this_id)
 268 {
 269   /* The dummy-frame sniffer always fills in the cache.  */
 270   struct dummy_frame_cache *cache = (*this_prologue_cache);
 271
 272   gdb_assert (cache != NULL);
 273   (*this_id) = cache->this_id;
 274 }
 275
 276 const struct frame_unwind dummy_frame_unwind =
 277 {
 278   DUMMY_FRAME,
 279   default_frame_unwind_stop_reason,
 280   dummy_frame_this_id,
 281   dummy_frame_prev_register,
 282   NULL,
 283   dummy_frame_sniffer,
 284 };
 285
 286 static void
 287 fprint_dummy_frames (struct ui_file *file)
 288 {
 289   struct dummy_frame *s;
 290
 291   for (s = dummy_frame_stack; s != NULL; s = s->next)
 292     {
 293       gdb_print_host_address (s, file);
 294       fprintf_unfiltered (file, ":");
 295       fprintf_unfiltered (file, " id=");
 296       fprint_frame_id (file, s->id);
 297       fprintf_unfiltered (file, "\n");
 298     }
 299 }
 300
 301 static void
 302 maintenance_print_dummy_frames (char *args, int from_tty)
 303 {
 304   if (args == NULL)
 305     fprint_dummy_frames (gdb_stdout);
 306   else
 307     {
 308       struct cleanup *cleanups;
 309       struct ui_file *file = gdb_fopen (args, "w");
 310
 311       if (file == NULL)
 312         perror_with_name (_("maintenance print dummy-frames"));
 313       cleanups = make_cleanup_ui_file_delete (file);
 314       fprint_dummy_frames (file);
 315       do_cleanups (cleanups);
 316     }
 317 }
 318
 319 extern void _initialize_dummy_frame (void);
 320
 321 void
 322 _initialize_dummy_frame (void)
 323 {
 324   add_cmd ("dummy-frames", class_maintenance, maintenance_print_dummy_frames,
 325            _("Print the contents of the internal dummy-frame stack."),
 326            &maintenanceprintlist);
 327
 328   observer_attach_inferior_created (cleanup_dummy_frames);
 329 }