gdb/dummy-frame.c

   1 /* Code dealing with dummy stack frames, for GDB, the GNU debugger.
   2
   3    Copyright 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., 59 Temple Place - Suite 330,
  22    Boston, MA 02111-1307, 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   /* Use an architecture specific method to extract the prev's dummy
 141      ID from the next frame.  Note that this method uses
 142      frame_register_unwind to obtain the register values needed to
 143      determine the dummy frame's ID.  */
 144   this_id = gdbarch_unwind_dummy_id (get_frame_arch (next_frame), next_frame);
 145
 146   /* Use that ID to find the corresponding cache entry.  */
 147   for (dummyframe = dummy_frame_stack;
 148        dummyframe != NULL;
 149        dummyframe = dummyframe->next)
 150     {
 151       if (frame_id_eq (dummyframe->id, this_id))
 152         {
 153           struct dummy_frame_cache *cache;
 154           cache = FRAME_OBSTACK_ZALLOC (struct dummy_frame_cache);
 155           cache->prev_regcache = dummyframe->regcache;
 156           cache->this_id = this_id;
 157           (*this_prologue_cache) = cache;
 158           return 1;
 159         }
 160     }
 161   return 0;
 162 }
 163
 164 /* Given a call-dummy dummy-frame, return the registers.  Here the
 165    register value is taken from the local copy of the register buffer.  */
 166
 167 static void
 168 dummy_frame_prev_register (struct frame_info *next_frame,
 169                            void **this_prologue_cache,
 170                            int regnum, int *optimized,
 171                            enum lval_type *lvalp, CORE_ADDR *addrp,
 172                            int *realnum, void *bufferp)
 173 {
 174   /* The dummy-frame sniffer always fills in the cache.  */
 175   struct dummy_frame_cache *cache = (*this_prologue_cache);
 176   gdb_assert (cache != NULL);
 177
 178   /* Describe the register's location.  Generic dummy frames always
 179      have the register value in an ``expression''.  */
 180   *optimized = 0;
 181   *lvalp = not_lval;
 182   *addrp = 0;
 183   *realnum = -1;
 184
 185   /* If needed, find and return the value of the register.  */
 186   if (bufferp != NULL)
 187     {
 188       /* Return the actual value.  */
 189       /* Use the regcache_cooked_read() method so that it, on the fly,
 190          constructs either a raw or pseudo register from the raw
 191          register cache.  */
 192       regcache_cooked_read (cache->prev_regcache, regnum, bufferp);
 193     }
 194 }
 195
 196 /* Assuming that THIS frame is a dummy (remember, the NEXT and not
 197    THIS frame is passed in), return the ID of THIS frame.  That ID is
 198    determined by examining the NEXT frame's unwound registers using
 199    the method unwind_dummy_id().  As a side effect, THIS dummy frame's
 200    dummy cache is located and and saved in THIS_PROLOGUE_CACHE.  */
 201
 202 static void
 203 dummy_frame_this_id (struct frame_info *next_frame,
 204                      void **this_prologue_cache,
 205                      struct frame_id *this_id)
 206 {
 207   /* The dummy-frame sniffer always fills in the cache.  */
 208   struct dummy_frame_cache *cache = (*this_prologue_cache);
 209   gdb_assert (cache != NULL);
 210   (*this_id) = cache->this_id;
 211 }
 212
 213 static const struct frame_unwind dummy_frame_unwinder =
 214 {
 215   DUMMY_FRAME,
 216   dummy_frame_this_id,
 217   dummy_frame_prev_register,
 218   NULL,
 219   dummy_frame_sniffer,
 220 };
 221
 222 const struct frame_unwind *const dummy_frame_unwind = {
 223   &dummy_frame_unwinder
 224 };
 225
 226 static void
 227 fprint_dummy_frames (struct ui_file *file)
 228 {
 229   struct dummy_frame *s;
 230   for (s = dummy_frame_stack; s != NULL; s = s->next)
 231     {
 232       gdb_print_host_address (s, file);
 233       fprintf_unfiltered (file, ":");
 234       fprintf_unfiltered (file, " id=");
 235       fprint_frame_id (file, s->id);
 236       fprintf_unfiltered (file, "\n");
 237     }
 238 }
 239
 240 static void
 241 maintenance_print_dummy_frames (char *args, int from_tty)
 242 {
 243   if (args == NULL)
 244     fprint_dummy_frames (gdb_stdout);
 245   else
 246     {
 247       struct ui_file *file = gdb_fopen (args, "w");
 248       if (file == NULL)
 249         perror_with_name (_("maintenance print dummy-frames"));
 250       fprint_dummy_frames (file);
 251       ui_file_delete (file);
 252     }
 253 }
 254
 255 extern void _initialize_dummy_frame (void);
 256
 257 void
 258 _initialize_dummy_frame (void)
 259 {
 260   add_cmd ("dummy-frames", class_maintenance, maintenance_print_dummy_frames,
 261            "Print the contents of the internal dummy-frame stack.",
 262            &maintenanceprintlist);
 263
 264 }