gdb/dummy-frame.c

   1 /* Code dealing with dummy stack frames, for GDB, the GNU debugger.
   2
   3    Copyright (C) 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
   4    1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2007, 2008, 2009,
   5    2010 Free Software Foundation, Inc.
   6
   7    This file is part of GDB.
   8
   9    This program is free software; you can redistribute it and/or modify
  10    it under the terms of the GNU General Public License as published by
  11    the Free Software Foundation; either version 3 of the License, or
  12    (at your option) any later version.
  13
  14    This program is distributed in the hope that it will be useful,
  15    but WITHOUT ANY WARRANTY; without even the implied warranty of
  16    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17    GNU General Public License for more details.
  18
  19    You should have received a copy of the GNU General Public License
  20    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  21
  22
  23 #include "defs.h"
  24 #include "dummy-frame.h"
  25 #include "regcache.h"
  26 #include "frame.h"
  27 #include "inferior.h"
  28 #include "gdb_assert.h"
  29 #include "frame-unwind.h"
  30 #include "command.h"
  31 #include "gdbcmd.h"
  32 #include "gdb_string.h"
  33 #include "observer.h"
  34
  35 /* Dummy frame.  This saves the processor state just prior to setting
  36    up the inferior function call.  Older targets save the registers
  37    on the target stack (but that really slows down function calls).  */
  38
  39 struct dummy_frame
  40 {
  41   struct dummy_frame *next;
  42   /* This frame's ID.  Must match the value returned by
  43      gdbarch_dummy_id.  */
  44   struct frame_id id;
  45   /* The caller's state prior to the call.  */
  46   struct inferior_thread_state *caller_state;
  47 };
  48
  49 static struct dummy_frame *dummy_frame_stack = NULL;
  50
  51 /* Function: deprecated_pc_in_call_dummy (pc)
  52
  53    Return non-zero if the PC falls in a dummy frame created by gdb for
  54    an inferior call.  The code below which allows gdbarch_decr_pc_after_break
  55    is for infrun.c, which may give the function a PC without that
  56    subtracted out.
  57
  58    FIXME: cagney/2002-11-23: This is silly.  Surely "infrun.c" can
  59    figure out what the real PC (as in the resume address) is BEFORE
  60    calling this function.
  61
  62    NOTE: cagney/2004-08-02: I'm pretty sure that, with the introduction of
  63    infrun.c:adjust_pc_after_break (thanks), this function is now
  64    always called with a correctly adjusted PC!
  65
  66    NOTE: cagney/2004-08-02: Code should not need to call this.  */
  67
  68 int
  69 deprecated_pc_in_call_dummy (struct gdbarch *gdbarch, CORE_ADDR pc)
  70 {
  71   struct dummy_frame *dummyframe;
  72
  73   for (dummyframe = dummy_frame_stack;
  74        dummyframe != NULL;
  75        dummyframe = dummyframe->next)
  76     {
  77       if ((pc >= dummyframe->id.code_addr)
  78           && (pc <= dummyframe->id.code_addr
  79                     + gdbarch_decr_pc_after_break (gdbarch)))
  80         return 1;
  81     }
  82   return 0;
  83 }
  84
  85 /* Push the caller's state, along with the dummy frame info, onto the
  86    dummy-frame stack.  */
  87
  88 void
  89 dummy_frame_push (struct inferior_thread_state *caller_state,
  90                   const struct frame_id *dummy_id)
  91 {
  92   struct dummy_frame *dummy_frame;
  93
  94   dummy_frame = XZALLOC (struct dummy_frame);
  95   dummy_frame->caller_state = caller_state;
  96   dummy_frame->id = (*dummy_id);
  97   dummy_frame->next = dummy_frame_stack;
  98   dummy_frame_stack = dummy_frame;
  99 }
 100
 101 /* Remove *DUMMY_PTR from the dummy frame stack.  */
 102
 103 static void
 104 remove_dummy_frame (struct dummy_frame **dummy_ptr)
 105 {
 106   struct dummy_frame *dummy = *dummy_ptr;
 107
 108   *dummy_ptr = dummy->next;
 109   discard_inferior_thread_state (dummy->caller_state);
 110   xfree (dummy);
 111 }
 112
 113 /* Pop *DUMMY_PTR, restoring program state to that before the
 114    frame was created.  */
 115
 116 static void
 117 pop_dummy_frame (struct dummy_frame **dummy_ptr)
 118 {
 119   struct dummy_frame *dummy;
 120
 121   restore_inferior_thread_state ((*dummy_ptr)->caller_state);
 122
 123   /* restore_inferior_status frees inf_state,
 124      all that remains is to pop *dummy_ptr */
 125   dummy = *dummy_ptr;
 126   *dummy_ptr = dummy->next;
 127   xfree (dummy);
 128
 129   /* We've made right mess of GDB's local state, just discard
 130      everything.  */
 131   reinit_frame_cache ();
 132 }
 133
 134 /* Look up DUMMY_ID.
 135    Return NULL if not found.  */
 136
 137 static struct dummy_frame **
 138 lookup_dummy_frame (struct frame_id dummy_id)
 139 {
 140   struct dummy_frame **dp;
 141
 142   for (dp = &dummy_frame_stack; *dp != NULL; dp = &(*dp)->next)
 143     {
 144       if (frame_id_eq ((*dp)->id, dummy_id))
 145         return dp;
 146     }
 147
 148   return NULL;
 149 }
 150
 151 /* Pop the dummy frame DUMMY_ID, restoring program state to that before the
 152    frame was created.
 153    On return reinit_frame_cache has been called.
 154    If the frame isn't found, flag an internal error.
 155
 156    NOTE: This can only pop the one frame, even if it is in the middle of the
 157    stack, because the other frames may be for different threads, and there's
 158    currently no way to tell which stack frame is for which thread.  */
 159
 160 void
 161 dummy_frame_pop (struct frame_id dummy_id)
 162 {
 163   struct dummy_frame **dp;
 164
 165   dp = lookup_dummy_frame (dummy_id);
 166   gdb_assert (dp != NULL);
 167
 168   pop_dummy_frame (dp);
 169 }
 170
 171 /* There may be stale dummy frames, perhaps left over from when a longjump took
 172    us out of a function that was called by the debugger.  Clean them up at
 173    least once whenever we start a new inferior.  */
 174
 175 static void
 176 cleanup_dummy_frames (struct target_ops *target, int from_tty)
 177 {
 178   while (dummy_frame_stack != NULL)
 179     remove_dummy_frame (&dummy_frame_stack);
 180 }
 181
 182 /* Return the dummy frame cache, it contains both the ID, and a
 183    pointer to the regcache.  */
 184 struct dummy_frame_cache
 185 {
 186   struct frame_id this_id;
 187   struct regcache *prev_regcache;
 188 };
 189
 190 static int
 191 dummy_frame_sniffer (const struct frame_unwind *self,
 192                      struct frame_info *this_frame,
 193                      void **this_prologue_cache)
 194 {
 195   struct dummy_frame *dummyframe;
 196   struct frame_id this_id;
 197
 198   /* When unwinding a normal frame, the stack structure is determined
 199      by analyzing the frame's function's code (be it using brute force
 200      prologue analysis, or the dwarf2 CFI).  In the case of a dummy
 201      frame, that simply isn't possible.  The PC is either the program
 202      entry point, or some random address on the stack.  Trying to use
 203      that PC to apply standard frame ID unwind techniques is just
 204      asking for trouble.  */
 205
 206   /* Don't bother unless there is at least one dummy frame.  */
 207   if (dummy_frame_stack != NULL)
 208     {
 209       /* Use an architecture specific method to extract this frame's
 210          dummy ID, assuming it is a dummy frame.  */
 211       this_id = gdbarch_dummy_id (get_frame_arch (this_frame), this_frame);
 212
 213       /* Use that ID to find the corresponding cache entry.  */
 214       for (dummyframe = dummy_frame_stack;
 215            dummyframe != NULL;
 216            dummyframe = dummyframe->next)
 217         {
 218           if (frame_id_eq (dummyframe->id, this_id))
 219             {
 220               struct dummy_frame_cache *cache;
 221
 222               cache = FRAME_OBSTACK_ZALLOC (struct dummy_frame_cache);
 223               cache->prev_regcache = get_inferior_thread_state_regcache (dummyframe->caller_state);
 224               cache->this_id = this_id;
 225               (*this_prologue_cache) = cache;
 226               return 1;
 227             }
 228         }
 229     }
 230   return 0;
 231 }
 232
 233 /* Given a call-dummy dummy-frame, return the registers.  Here the
 234    register value is taken from the local copy of the register buffer.  */
 235
 236 static struct value *
 237 dummy_frame_prev_register (struct frame_info *this_frame,
 238                            void **this_prologue_cache,
 239                            int regnum)
 240 {
 241   struct dummy_frame_cache *cache = (*this_prologue_cache);
 242   struct gdbarch *gdbarch = get_frame_arch (this_frame);
 243   struct value *reg_val;
 244
 245   /* The dummy-frame sniffer always fills in the cache.  */
 246   gdb_assert (cache != NULL);
 247
 248   /* Describe the register's location.  Generic dummy frames always
 249      have the register value in an ``expression''.  */
 250   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 251
 252   /* Use the regcache_cooked_read() method so that it, on the fly,
 253      constructs either a raw or pseudo register from the raw
 254      register cache.  */
 255   regcache_cooked_read (cache->prev_regcache, regnum,
 256                         value_contents_writeable (reg_val));
 257   return reg_val;
 258 }
 259
 260 /* Assuming that THIS_FRAME is a dummy, return its ID.  That ID is
 261    determined by examining the NEXT frame's unwound registers using
 262    the method dummy_id().  As a side effect, THIS dummy frame's
 263    dummy cache is located and and saved in THIS_PROLOGUE_CACHE.  */
 264
 265 static void
 266 dummy_frame_this_id (struct frame_info *this_frame,
 267                      void **this_prologue_cache,
 268                      struct frame_id *this_id)
 269 {
 270   /* The dummy-frame sniffer always fills in the cache.  */
 271   struct dummy_frame_cache *cache = (*this_prologue_cache);
 272
 273   gdb_assert (cache != NULL);
 274   (*this_id) = cache->this_id;
 275 }
 276
 277 const struct frame_unwind dummy_frame_unwind =
 278 {
 279   DUMMY_FRAME,
 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 }