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   for (dummyframe = dummy_frame_stack;
  73        dummyframe != NULL;
  74        dummyframe = dummyframe->next)
  75     {
  76       if ((pc >= dummyframe->id.code_addr)
  77           && (pc <= dummyframe->id.code_addr
  78                     + gdbarch_decr_pc_after_break (gdbarch)))
  79         return 1;
  80     }
  81   return 0;
  82 }
  83
  84 /* Push the caller's state, along with the dummy frame info, onto the
  85    dummy-frame stack.  */
  86
  87 void
  88 dummy_frame_push (struct inferior_thread_state *caller_state,
  89                   const struct frame_id *dummy_id)
  90 {
  91   struct dummy_frame *dummy_frame;
  92
  93   dummy_frame = XZALLOC (struct dummy_frame);
  94   dummy_frame->caller_state = caller_state;
  95   dummy_frame->id = (*dummy_id);
  96   dummy_frame->next = dummy_frame_stack;
  97   dummy_frame_stack = dummy_frame;
  98 }
  99
 100 /* Remove *DUMMY_PTR from the dummy frame stack.  */
 101
 102 static void
 103 remove_dummy_frame (struct dummy_frame **dummy_ptr)
 104 {
 105   struct dummy_frame *dummy = *dummy_ptr;
 106
 107   *dummy_ptr = dummy->next;
 108   discard_inferior_thread_state (dummy->caller_state);
 109   xfree (dummy);
 110 }
 111
 112 /* Pop *DUMMY_PTR, restoring program state to that before the
 113    frame was created.  */
 114
 115 static void
 116 pop_dummy_frame (struct dummy_frame **dummy_ptr)
 117 {
 118   struct dummy_frame *dummy;
 119
 120   restore_inferior_thread_state ((*dummy_ptr)->caller_state);
 121
 122   /* restore_inferior_status frees inf_state,
 123      all that remains is to pop *dummy_ptr */
 124   dummy = *dummy_ptr;
 125   *dummy_ptr = dummy->next;
 126   xfree (dummy);
 127
 128   /* We've made right mess of GDB's local state, just discard
 129      everything.  */
 130   reinit_frame_cache ();
 131 }
 132
 133 /* Look up DUMMY_ID.
 134    Return NULL if not found.  */
 135
 136 static struct dummy_frame **
 137 lookup_dummy_frame (struct frame_id dummy_id)
 138 {
 139   struct dummy_frame **dp;
 140
 141   for (dp = &dummy_frame_stack; *dp != NULL; dp = &(*dp)->next)
 142     {
 143       if (frame_id_eq ((*dp)->id, dummy_id))
 144         return dp;
 145     }
 146
 147   return NULL;
 148 }
 149
 150 /* Pop the dummy frame DUMMY_ID, restoring program state to that before the
 151    frame was created.
 152    On return reinit_frame_cache has been called.
 153    If the frame isn't found, flag an internal error.
 154
 155    NOTE: This can only pop the one frame, even if it is in the middle of the
 156    stack, because the other frames may be for different threads, and there's
 157    currently no way to tell which stack frame is for which thread.  */
 158
 159 void
 160 dummy_frame_pop (struct frame_id dummy_id)
 161 {
 162   struct dummy_frame **dp;
 163
 164   dp = lookup_dummy_frame (dummy_id);
 165   gdb_assert (dp != NULL);
 166
 167   pop_dummy_frame (dp);
 168 }
 169
 170 /* There may be stale dummy frames, perhaps left over from when a longjump took
 171    us out of a function that was called by the debugger.  Clean them up at
 172    least once whenever we start a new inferior.  */
 173
 174 static void
 175 cleanup_dummy_frames (struct target_ops *target, int from_tty)
 176 {
 177   while (dummy_frame_stack != NULL)
 178     remove_dummy_frame (&dummy_frame_stack);
 179 }
 180
 181 /* Return the dummy frame cache, it contains both the ID, and a
 182    pointer to the regcache.  */
 183 struct dummy_frame_cache
 184 {
 185   struct frame_id this_id;
 186   struct regcache *prev_regcache;
 187 };
 188
 189 static int
 190 dummy_frame_sniffer (const struct frame_unwind *self,
 191                      struct frame_info *this_frame,
 192                      void **this_prologue_cache)
 193 {
 194   struct dummy_frame *dummyframe;
 195   struct frame_id this_id;
 196
 197   /* When unwinding a normal frame, the stack structure is determined
 198      by analyzing the frame's function's code (be it using brute force
 199      prologue analysis, or the dwarf2 CFI).  In the case of a dummy
 200      frame, that simply isn't possible.  The PC is either the program
 201      entry point, or some random address on the stack.  Trying to use
 202      that PC to apply standard frame ID unwind techniques is just
 203      asking for trouble.  */
 204
 205   /* Don't bother unless there is at least one dummy frame.  */
 206   if (dummy_frame_stack != NULL)
 207     {
 208       /* Use an architecture specific method to extract this frame's
 209          dummy ID, assuming it is a dummy frame.  */
 210       this_id = gdbarch_dummy_id (get_frame_arch (this_frame), this_frame);
 211
 212       /* Use that ID to find the corresponding cache entry.  */
 213       for (dummyframe = dummy_frame_stack;
 214            dummyframe != NULL;
 215            dummyframe = dummyframe->next)
 216         {
 217           if (frame_id_eq (dummyframe->id, this_id))
 218             {
 219               struct dummy_frame_cache *cache;
 220               cache = FRAME_OBSTACK_ZALLOC (struct dummy_frame_cache);
 221               cache->prev_regcache = get_inferior_thread_state_regcache (dummyframe->caller_state);
 222               cache->this_id = this_id;
 223               (*this_prologue_cache) = cache;
 224               return 1;
 225             }
 226         }
 227     }
 228   return 0;
 229 }
 230
 231 /* Given a call-dummy dummy-frame, return the registers.  Here the
 232    register value is taken from the local copy of the register buffer.  */
 233
 234 static struct value *
 235 dummy_frame_prev_register (struct frame_info *this_frame,
 236                            void **this_prologue_cache,
 237                            int regnum)
 238 {
 239   struct dummy_frame_cache *cache = (*this_prologue_cache);
 240   struct gdbarch *gdbarch = get_frame_arch (this_frame);
 241   struct value *reg_val;
 242
 243   /* The dummy-frame sniffer always fills in the cache.  */
 244   gdb_assert (cache != NULL);
 245
 246   /* Describe the register's location.  Generic dummy frames always
 247      have the register value in an ``expression''.  */
 248   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 249
 250   /* Use the regcache_cooked_read() method so that it, on the fly,
 251      constructs either a raw or pseudo register from the raw
 252      register cache.  */
 253   regcache_cooked_read (cache->prev_regcache, regnum,
 254                         value_contents_writeable (reg_val));
 255   return reg_val;
 256 }
 257
 258 /* Assuming that THIS_FRAME is a dummy, return its ID.  That ID is
 259    determined by examining the NEXT frame's unwound registers using
 260    the method dummy_id().  As a side effect, THIS dummy frame's
 261    dummy cache is located and and saved in THIS_PROLOGUE_CACHE.  */
 262
 263 static void
 264 dummy_frame_this_id (struct frame_info *this_frame,
 265                      void **this_prologue_cache,
 266                      struct frame_id *this_id)
 267 {
 268   /* The dummy-frame sniffer always fills in the cache.  */
 269   struct dummy_frame_cache *cache = (*this_prologue_cache);
 270   gdb_assert (cache != NULL);
 271   (*this_id) = cache->this_id;
 272 }
 273
 274 static const struct frame_unwind dummy_frame_unwinder =
 275 {
 276   DUMMY_FRAME,
 277   dummy_frame_this_id,
 278   dummy_frame_prev_register,
 279   NULL,
 280   dummy_frame_sniffer,
 281 };
 282
 283 const struct frame_unwind *const dummy_frame_unwind = {
 284   &dummy_frame_unwinder
 285 };
 286
 287 static void
 288 fprint_dummy_frames (struct ui_file *file)
 289 {
 290   struct dummy_frame *s;
 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       if (file == NULL)
 311         perror_with_name (_("maintenance print dummy-frames"));
 312       cleanups = make_cleanup_ui_file_delete (file);
 313       fprint_dummy_frames (file);
 314       do_cleanups (cleanups);
 315     }
 316 }
 317
 318 extern void _initialize_dummy_frame (void);
 319
 320 void
 321 _initialize_dummy_frame (void)
 322 {
 323   add_cmd ("dummy-frames", class_maintenance, maintenance_print_dummy_frames,
 324            _("Print the contents of the internal dummy-frame stack."),
 325            &maintenanceprintlist);
 326
 327   observer_attach_inferior_created (cleanup_dummy_frames);
 328 }