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
   5    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
  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_unwind_dummy_id.  */
  43   struct frame_id id;
  44   /* The caller's regcache.  */
  45   struct regcache *regcache;
  46 };
  47
  48 static struct dummy_frame *dummy_frame_stack = NULL;
  49
  50 /* Function: deprecated_pc_in_call_dummy (pc)
  51
  52    Return non-zero if the PC falls in a dummy frame created by gdb for
  53    an inferior call.  The code below which allows gdbarch_decr_pc_after_break
  54    is for infrun.c, which may give the function a PC without that
  55    subtracted out.
  56
  57    FIXME: cagney/2002-11-23: This is silly.  Surely "infrun.c" can
  58    figure out what the real PC (as in the resume address) is BEFORE
  59    calling this function.
  60
  61    NOTE: cagney/2004-08-02: I'm pretty sure that, with the introduction of
  62    infrun.c:adjust_pc_after_break (thanks), this function is now
  63    always called with a correctly adjusted PC!
  64
  65    NOTE: cagney/2004-08-02: Code should not need to call this.  */
  66
  67 int
  68 deprecated_pc_in_call_dummy (CORE_ADDR pc)
  69 {
  70   struct dummy_frame *dummyframe;
  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 (current_gdbarch)))
  78         return 1;
  79     }
  80   return 0;
  81 }
  82
  83 /* Push the caller's state, along with the dummy frame info, onto a
  84    dummy-frame stack.  */
  85
  86 void
  87 dummy_frame_push (struct regcache *caller_regcache,
  88                   const struct frame_id *dummy_id)
  89 {
  90   struct dummy_frame *dummy_frame;
  91
  92   /* Check to see if there are stale dummy frames, perhaps left over
  93      from when a longjump took us out of a function that was called by
  94      the debugger.  */
  95   dummy_frame = dummy_frame_stack;
  96   while (dummy_frame)
  97     /* FIXME: cagney/2004-08-02: Should just test IDs.  */
  98     if (frame_id_inner (dummy_frame->id, (*dummy_id)))
  99       /* Stale -- destroy!  */
 100       {
 101         dummy_frame_stack = dummy_frame->next;
 102         regcache_xfree (dummy_frame->regcache);
 103         xfree (dummy_frame);
 104         dummy_frame = dummy_frame_stack;
 105       }
 106     else
 107       dummy_frame = dummy_frame->next;
 108
 109   dummy_frame = XZALLOC (struct dummy_frame);
 110   dummy_frame->regcache = caller_regcache;
 111   dummy_frame->id = (*dummy_id);
 112   dummy_frame->next = dummy_frame_stack;
 113   dummy_frame_stack = dummy_frame;
 114 }
 115
 116 /* Return the dummy frame cache, it contains both the ID, and a
 117    pointer to the regcache.  */
 118 struct dummy_frame_cache
 119 {
 120   struct frame_id this_id;
 121   struct regcache *prev_regcache;
 122 };
 123
 124 int
 125 dummy_frame_sniffer (const struct frame_unwind *self,
 126                      struct frame_info *next_frame,
 127                      void **this_prologue_cache)
 128 {
 129   struct dummy_frame *dummyframe;
 130   struct frame_id this_id;
 131
 132   /* When unwinding a normal frame, the stack structure is determined
 133      by analyzing the frame's function's code (be it using brute force
 134      prologue analysis, or the dwarf2 CFI).  In the case of a dummy
 135      frame, that simply isn't possible.  The PC is either the program
 136      entry point, or some random address on the stack.  Trying to use
 137      that PC to apply standard frame ID unwind techniques is just
 138      asking for trouble.  */
 139
 140   /* Don't bother unles there is at least one dummy frame.  */
 141   if (dummy_frame_stack != NULL)
 142     {
 143       /* Use an architecture specific method to extract the prev's
 144          dummy ID from the next frame.  Note that this method uses
 145          frame_register_unwind to obtain the register values needed to
 146          determine the dummy frame's ID.  */
 147       this_id = gdbarch_unwind_dummy_id (get_frame_arch (next_frame),
 148                                          next_frame);
 149
 150       /* Use that ID to find the corresponding cache entry.  */
 151       for (dummyframe = dummy_frame_stack;
 152            dummyframe != NULL;
 153            dummyframe = dummyframe->next)
 154         {
 155           if (frame_id_eq (dummyframe->id, this_id))
 156             {
 157               struct dummy_frame_cache *cache;
 158               cache = FRAME_OBSTACK_ZALLOC (struct dummy_frame_cache);
 159               cache->prev_regcache = dummyframe->regcache;
 160               cache->this_id = this_id;
 161               (*this_prologue_cache) = cache;
 162               return 1;
 163             }
 164         }
 165     }
 166   return 0;
 167 }
 168
 169 /* Given a call-dummy dummy-frame, return the registers.  Here the
 170    register value is taken from the local copy of the register buffer.  */
 171
 172 static void
 173 dummy_frame_prev_register (struct frame_info *next_frame,
 174                            void **this_prologue_cache,
 175                            int regnum, int *optimized,
 176                            enum lval_type *lvalp, CORE_ADDR *addrp,
 177                            int *realnum, gdb_byte *bufferp)
 178 {
 179   /* The dummy-frame sniffer always fills in the cache.  */
 180   struct dummy_frame_cache *cache = (*this_prologue_cache);
 181   gdb_assert (cache != NULL);
 182
 183   /* Describe the register's location.  Generic dummy frames always
 184      have the register value in an ``expression''.  */
 185   *optimized = 0;
 186   *lvalp = not_lval;
 187   *addrp = 0;
 188   *realnum = -1;
 189
 190   /* If needed, find and return the value of the register.  */
 191   if (bufferp != NULL)
 192     {
 193       /* Return the actual value.  */
 194       /* Use the regcache_cooked_read() method so that it, on the fly,
 195          constructs either a raw or pseudo register from the raw
 196          register cache.  */
 197       regcache_cooked_read (cache->prev_regcache, regnum, bufferp);
 198     }
 199 }
 200
 201 /* Assuming that THIS frame is a dummy (remember, the NEXT and not
 202    THIS frame is passed in), return the ID of THIS frame.  That ID is
 203    determined by examining the NEXT frame's unwound registers using
 204    the method unwind_dummy_id().  As a side effect, THIS dummy frame's
 205    dummy cache is located and and saved in THIS_PROLOGUE_CACHE.  */
 206
 207 static void
 208 dummy_frame_this_id (struct frame_info *next_frame,
 209                      void **this_prologue_cache,
 210                      struct frame_id *this_id)
 211 {
 212   /* The dummy-frame sniffer always fills in the cache.  */
 213   struct dummy_frame_cache *cache = (*this_prologue_cache);
 214   gdb_assert (cache != NULL);
 215   (*this_id) = cache->this_id;
 216 }
 217
 218 static const struct frame_unwind dummy_frame_unwinder =
 219 {
 220   DUMMY_FRAME,
 221   dummy_frame_this_id,
 222   dummy_frame_prev_register,
 223   NULL,
 224   dummy_frame_sniffer,
 225 };
 226
 227 const struct frame_unwind *const dummy_frame_unwind = {
 228   &dummy_frame_unwinder
 229 };
 230
 231 static void
 232 fprint_dummy_frames (struct ui_file *file)
 233 {
 234   struct dummy_frame *s;
 235   for (s = dummy_frame_stack; s != NULL; s = s->next)
 236     {
 237       gdb_print_host_address (s, file);
 238       fprintf_unfiltered (file, ":");
 239       fprintf_unfiltered (file, " id=");
 240       fprint_frame_id (file, s->id);
 241       fprintf_unfiltered (file, "\n");
 242     }
 243 }
 244
 245 static void
 246 maintenance_print_dummy_frames (char *args, int from_tty)
 247 {
 248   if (args == NULL)
 249     fprint_dummy_frames (gdb_stdout);
 250   else
 251     {
 252       struct ui_file *file = gdb_fopen (args, "w");
 253       if (file == NULL)
 254         perror_with_name (_("maintenance print dummy-frames"));
 255       fprint_dummy_frames (file);
 256       ui_file_delete (file);
 257     }
 258 }
 259
 260 extern void _initialize_dummy_frame (void);
 261
 262 void
 263 _initialize_dummy_frame (void)
 264 {
 265   add_cmd ("dummy-frames", class_maintenance, maintenance_print_dummy_frames,
 266            _("Print the contents of the internal dummy-frame stack."),
 267            &maintenanceprintlist);
 268
 269 }