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,
   4    1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004 Free
   5    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 2 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, write to the Free Software
  21    Foundation, Inc., 51 Franklin Street, Fifth Floor,
  22    Boston, MA 02110-1301, USA.  */
  23
  24
  25 #include "defs.h"
  26 #include "dummy-frame.h"
  27 #include "regcache.h"
  28 #include "frame.h"
  29 #include "inferior.h"
  30 #include "gdb_assert.h"
  31 #include "frame-unwind.h"
  32 #include "command.h"
  33 #include "gdbcmd.h"
  34 #include "gdb_string.h"
  35
  36 /* Dummy frame.  This saves the processor state just prior to setting
  37    up the inferior function call.  Older targets save the registers
  38    on the target stack (but that really slows down function calls).  */
  39
  40 struct dummy_frame
  41 {
  42   struct dummy_frame *next;
  43   /* This frame's ID.  Must match the value returned by
  44      gdbarch_unwind_dummy_id.  */
  45   struct frame_id id;
  46   /* The caller's regcache.  */
  47   struct regcache *regcache;
  48 };
  49
  50 static struct dummy_frame *dummy_frame_stack = NULL;
  51
  52 /* Function: deprecated_pc_in_call_dummy (pc)
  53
  54    Return non-zero if the PC falls in a dummy frame created by gdb for
  55    an inferior call.  The code below which allows DECR_PC_AFTER_BREAK
  56    is for infrun.c, which may give the function a PC without that
  57    subtracted out.
  58
  59    FIXME: cagney/2002-11-23: This is silly.  Surely "infrun.c" can
  60    figure out what the real PC (as in the resume address) is BEFORE
  61    calling this function.
  62
  63    NOTE: cagney/2004-08-02: I'm pretty sure that, with the introduction of
  64    infrun.c:adjust_pc_after_break (thanks), this function is now
  65    always called with a correctly adjusted PC!
  66
  67    NOTE: cagney/2004-08-02: Code should not need to call this.  */
  68
  69 int
  70 deprecated_pc_in_call_dummy (CORE_ADDR pc)
  71 {
  72   struct dummy_frame *dummyframe;
  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 + DECR_PC_AFTER_BREAK))
  79         return 1;
  80     }
  81   return 0;
  82 }
  83
  84 /* Push the caller's state, along with the dummy frame info, onto a
  85    dummy-frame stack.  */
  86
  87 void
  88 dummy_frame_push (struct regcache *caller_regcache,
  89                   const struct frame_id *dummy_id)
  90 {
  91   struct dummy_frame *dummy_frame;
  92
  93   /* Check to see if there are stale dummy frames, perhaps left over
  94      from when a longjump took us out of a function that was called by
  95      the debugger.  */
  96   dummy_frame = dummy_frame_stack;
  97   while (dummy_frame)
  98     /* FIXME: cagney/2004-08-02: Should just test IDs.  */
  99     if (frame_id_inner (dummy_frame->id, (*dummy_id)))
 100       /* Stale -- destroy!  */
 101       {
 102         dummy_frame_stack = dummy_frame->next;
 103         regcache_xfree (dummy_frame->regcache);
 104         xfree (dummy_frame);
 105         dummy_frame = dummy_frame_stack;
 106       }
 107     else
 108       dummy_frame = dummy_frame->next;
 109
 110   dummy_frame = XZALLOC (struct dummy_frame);
 111   dummy_frame->regcache = caller_regcache;
 112   dummy_frame->id = (*dummy_id);
 113   dummy_frame->next = dummy_frame_stack;
 114   dummy_frame_stack = dummy_frame;
 115 }
 116
 117 /* Return the dummy frame cache, it contains both the ID, and a
 118    pointer to the regcache.  */
 119 struct dummy_frame_cache
 120 {
 121   struct frame_id this_id;
 122   struct regcache *prev_regcache;
 123 };
 124
 125 int
 126 dummy_frame_sniffer (const struct frame_unwind *self,
 127                      struct frame_info *next_frame,
 128                      void **this_prologue_cache)
 129 {
 130   struct dummy_frame *dummyframe;
 131   struct frame_id this_id;
 132
 133   /* When unwinding a normal frame, the stack structure is determined
 134      by analyzing the frame's function's code (be it using brute force
 135      prologue analysis, or the dwarf2 CFI).  In the case of a dummy
 136      frame, that simply isn't possible.  The PC is either the program
 137      entry point, or some random address on the stack.  Trying to use
 138      that PC to apply standard frame ID unwind techniques is just
 139      asking for trouble.  */
 140
 141   /* Don't bother unles there is at least one dummy frame.  */
 142   if (dummy_frame_stack != NULL)
 143     {
 144       /* Use an architecture specific method to extract the prev's
 145          dummy ID from the next frame.  Note that this method uses
 146          frame_register_unwind to obtain the register values needed to
 147          determine the dummy frame's ID.  */
 148       this_id = gdbarch_unwind_dummy_id (get_frame_arch (next_frame),
 149                                          next_frame);
 150
 151       /* Use that ID to find the corresponding cache entry.  */
 152       for (dummyframe = dummy_frame_stack;
 153            dummyframe != NULL;
 154            dummyframe = dummyframe->next)
 155         {
 156           if (frame_id_eq (dummyframe->id, this_id))
 157             {
 158               struct dummy_frame_cache *cache;
 159               cache = FRAME_OBSTACK_ZALLOC (struct dummy_frame_cache);
 160               cache->prev_regcache = dummyframe->regcache;
 161               cache->this_id = this_id;
 162               (*this_prologue_cache) = cache;
 163               return 1;
 164             }
 165         }
 166     }
 167   return 0;
 168 }
 169
 170 /* Given a call-dummy dummy-frame, return the registers.  Here the
 171    register value is taken from the local copy of the register buffer.  */
 172
 173 static void
 174 dummy_frame_prev_register (struct frame_info *next_frame,
 175                            void **this_prologue_cache,
 176                            int regnum, int *optimized,
 177                            enum lval_type *lvalp, CORE_ADDR *addrp,
 178                            int *realnum, gdb_byte *bufferp)
 179 {
 180   /* The dummy-frame sniffer always fills in the cache.  */
 181   struct dummy_frame_cache *cache = (*this_prologue_cache);
 182   gdb_assert (cache != NULL);
 183
 184   /* Describe the register's location.  Generic dummy frames always
 185      have the register value in an ``expression''.  */
 186   *optimized = 0;
 187   *lvalp = not_lval;
 188   *addrp = 0;
 189   *realnum = -1;
 190
 191   /* If needed, find and return the value of the register.  */
 192   if (bufferp != NULL)
 193     {
 194       /* Return the actual value.  */
 195       /* Use the regcache_cooked_read() method so that it, on the fly,
 196          constructs either a raw or pseudo register from the raw
 197          register cache.  */
 198       regcache_cooked_read (cache->prev_regcache, regnum, bufferp);
 199     }
 200 }
 201
 202 /* Assuming that THIS frame is a dummy (remember, the NEXT and not
 203    THIS frame is passed in), return the ID of THIS frame.  That ID is
 204    determined by examining the NEXT frame's unwound registers using
 205    the method unwind_dummy_id().  As a side effect, THIS dummy frame's
 206    dummy cache is located and and saved in THIS_PROLOGUE_CACHE.  */
 207
 208 static void
 209 dummy_frame_this_id (struct frame_info *next_frame,
 210                      void **this_prologue_cache,
 211                      struct frame_id *this_id)
 212 {
 213   /* The dummy-frame sniffer always fills in the cache.  */
 214   struct dummy_frame_cache *cache = (*this_prologue_cache);
 215   gdb_assert (cache != NULL);
 216   (*this_id) = cache->this_id;
 217 }
 218
 219 static const struct frame_unwind dummy_frame_unwinder =
 220 {
 221   DUMMY_FRAME,
 222   dummy_frame_this_id,
 223   dummy_frame_prev_register,
 224   NULL,
 225   dummy_frame_sniffer,
 226 };
 227
 228 const struct frame_unwind *const dummy_frame_unwind = {
 229   &dummy_frame_unwinder
 230 };
 231
 232 static void
 233 fprint_dummy_frames (struct ui_file *file)
 234 {
 235   struct dummy_frame *s;
 236   for (s = dummy_frame_stack; s != NULL; s = s->next)
 237     {
 238       gdb_print_host_address (s, file);
 239       fprintf_unfiltered (file, ":");
 240       fprintf_unfiltered (file, " id=");
 241       fprint_frame_id (file, s->id);
 242       fprintf_unfiltered (file, "\n");
 243     }
 244 }
 245
 246 static void
 247 maintenance_print_dummy_frames (char *args, int from_tty)
 248 {
 249   if (args == NULL)
 250     fprint_dummy_frames (gdb_stdout);
 251   else
 252     {
 253       struct ui_file *file = gdb_fopen (args, "w");
 254       if (file == NULL)
 255         perror_with_name (_("maintenance print dummy-frames"));
 256       fprint_dummy_frames (file);
 257       ui_file_delete (file);
 258     }
 259 }
 260
 261 extern void _initialize_dummy_frame (void);
 262
 263 void
 264 _initialize_dummy_frame (void)
 265 {
 266   add_cmd ("dummy-frames", class_maintenance, maintenance_print_dummy_frames,
 267            _("Print the contents of the internal dummy-frame stack."),
 268            &maintenanceprintlist);
 269
 270 }