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
  35 static void dummy_frame_this_id (struct frame_info *next_frame,
  36                                  void **this_prologue_cache,
  37                                  struct frame_id *this_id);
  38
  39 static int pc_in_dummy_frame (CORE_ADDR pc);
  40
  41 /* Dummy frame.  This saves the processor state just prior to setting
  42    up the inferior function call.  Older targets save the registers
  43    on the target stack (but that really slows down function calls).  */
  44
  45 struct dummy_frame
  46 {
  47   struct dummy_frame *next;
  48
  49   /* These values belong to the caller (the previous frame, the frame
  50      that this unwinds back to).  */
  51   CORE_ADDR pc;
  52   CORE_ADDR top;
  53   struct frame_id id;
  54   struct regcache *regcache;
  55
  56   /* Address range of the call dummy code.  Look for PC in the range
  57      [LO..HI) (after allowing for DECR_PC_AFTER_BREAK).  */
  58   CORE_ADDR call_lo;
  59   CORE_ADDR call_hi;
  60 };
  61
  62 static struct dummy_frame *dummy_frame_stack = NULL;
  63
  64 /* Function: find_dummy_frame(pc, fp, sp)
  65
  66    Search the stack of dummy frames for one matching the given PC and
  67    FP/SP.  Unlike pc_in_dummy_frame(), this function doesn't need to
  68    adjust for DECR_PC_AFTER_BREAK.  This is because it is only legal
  69    to call this function after the PC has been adjusted.  */
  70
  71 static struct dummy_frame *
  72 find_dummy_frame (CORE_ADDR pc, CORE_ADDR fp)
  73 {
  74   struct dummy_frame *dummyframe;
  75
  76   for (dummyframe = dummy_frame_stack; dummyframe != NULL;
  77        dummyframe = dummyframe->next)
  78     {
  79       /* Does the PC fall within the dummy frame's breakpoint
  80          instruction.  If not, discard this one.  */
  81       if (!(pc >= dummyframe->call_lo && pc < dummyframe->call_hi))
  82         continue;
  83       /* Does the FP match?  */
  84       /* "infcall.c" explicitly saved the top-of-stack before the
  85          inferior function call, assume unwind_dummy_id() returns that
  86          same stack value.  */
  87       if (fp != dummyframe->top)
  88         continue;
  89       /* The FP matches this dummy frame.  */
  90       return dummyframe;
  91     }
  92
  93   return NULL;
  94 }
  95
  96 /* Function: pc_in_call_dummy (pc)
  97
  98    Return true if the PC falls in a dummy frame created by gdb for an
  99    inferior call.  The code below which allows DECR_PC_AFTER_BREAK is
 100    for infrun.c, which may give the function a PC without that
 101    subtracted out.  */
 102
 103 int
 104 deprecated_pc_in_call_dummy (CORE_ADDR pc)
 105 {
 106   return pc_in_dummy_frame (pc);
 107 }
 108
 109 /* Return non-zero if the PC falls in a dummy frame.
 110
 111    The code below which allows DECR_PC_AFTER_BREAK is for infrun.c,
 112    which may give the function a PC without that subtracted out.
 113
 114    FIXME: cagney/2002-11-23: This is silly.  Surely "infrun.c" can
 115    figure out what the real PC (as in the resume address) is BEFORE
 116    calling this function.  */
 117
 118 static int
 119 pc_in_dummy_frame (CORE_ADDR pc)
 120 {
 121   struct dummy_frame *dummyframe;
 122   for (dummyframe = dummy_frame_stack;
 123        dummyframe != NULL;
 124        dummyframe = dummyframe->next)
 125     {
 126       if ((pc >= dummyframe->call_lo)
 127           && (pc < dummyframe->call_hi + DECR_PC_AFTER_BREAK))
 128         return 1;
 129     }
 130   return 0;
 131 }
 132
 133 /* Save all the registers on the dummy frame stack.  Most ports save the
 134    registers on the target stack.  This results in lots of unnecessary memory
 135    references, which are slow when debugging via a serial line.  Instead, we
 136    save all the registers internally, and never write them to the stack.  The
 137    registers get restored when the called function returns to the entry point,
 138    where a breakpoint is laying in wait.  */
 139
 140 void
 141 generic_push_dummy_frame (void)
 142 {
 143   struct dummy_frame *dummy_frame;
 144   CORE_ADDR fp = get_frame_base (get_current_frame ());
 145
 146   /* check to see if there are stale dummy frames,
 147      perhaps left over from when a longjump took us out of a
 148      function that was called by the debugger */
 149
 150   dummy_frame = dummy_frame_stack;
 151   while (dummy_frame)
 152     if (gdbarch_inner_than (current_gdbarch, dummy_frame->top, fp))
 153       /* stale -- destroy! */
 154       {
 155         dummy_frame_stack = dummy_frame->next;
 156         regcache_xfree (dummy_frame->regcache);
 157         xfree (dummy_frame);
 158         dummy_frame = dummy_frame_stack;
 159       }
 160     else
 161       dummy_frame = dummy_frame->next;
 162
 163   dummy_frame = xmalloc (sizeof (struct dummy_frame));
 164   dummy_frame->regcache = frame_save_as_regcache (get_current_frame ());
 165
 166   dummy_frame->pc = read_pc ();
 167   dummy_frame->top = 0;
 168   dummy_frame->id = get_frame_id (get_current_frame ());
 169   dummy_frame->next = dummy_frame_stack;
 170   dummy_frame_stack = dummy_frame;
 171 }
 172
 173 void
 174 generic_save_dummy_frame_tos (CORE_ADDR sp)
 175 {
 176   dummy_frame_stack->top = sp;
 177 }
 178
 179 /* Record the upper/lower bounds on the address of the call dummy.  */
 180
 181 void
 182 generic_save_call_dummy_addr (CORE_ADDR lo, CORE_ADDR hi)
 183 {
 184   dummy_frame_stack->call_lo = lo;
 185   dummy_frame_stack->call_hi = hi;
 186 }
 187
 188 /* Given a call-dummy dummy-frame, return the registers.  Here the
 189    register value is taken from the local copy of the register buffer.  */
 190
 191 static void
 192 dummy_frame_prev_register (struct frame_info *next_frame,
 193                            void **this_prologue_cache,
 194                            int regnum, int *optimized,
 195                            enum lval_type *lvalp, CORE_ADDR *addrp,
 196                            int *realnum, void *bufferp)
 197 {
 198   struct dummy_frame *dummy;
 199   struct frame_id id;
 200
 201   /* Call the ID method which, if at all possible, will set the
 202      prologue cache.  */
 203   dummy_frame_this_id (next_frame, this_prologue_cache, &id);
 204   dummy = (*this_prologue_cache);
 205   gdb_assert (dummy != NULL);
 206
 207   /* Describe the register's location.  Generic dummy frames always
 208      have the register value in an ``expression''.  */
 209   *optimized = 0;
 210   *lvalp = not_lval;
 211   *addrp = 0;
 212   *realnum = -1;
 213
 214   /* If needed, find and return the value of the register.  */
 215   if (bufferp != NULL)
 216     {
 217       /* Return the actual value.  */
 218       /* Use the regcache_cooked_read() method so that it, on the fly,
 219          constructs either a raw or pseudo register from the raw
 220          register cache.  */
 221       regcache_cooked_read (dummy->regcache, regnum, bufferp);
 222     }
 223 }
 224
 225 /* Assuming that THIS frame is a dummy (remember, the NEXT and not
 226    THIS frame is passed in), return the ID of THIS frame.  That ID is
 227    determined by examining the NEXT frame's unwound registers using
 228    the method unwind_dummy_id().  As a side effect, THIS dummy frame's
 229    dummy cache is located and and saved in THIS_PROLOGUE_CACHE.  */
 230
 231 static void
 232 dummy_frame_this_id (struct frame_info *next_frame,
 233                      void **this_prologue_cache,
 234                      struct frame_id *this_id)
 235 {
 236   struct dummy_frame *dummy = (*this_prologue_cache);
 237   if (dummy != NULL)
 238     {
 239       (*this_id) = dummy->id;
 240       return;
 241     }
 242   /* When unwinding a normal frame, the stack structure is determined
 243      by analyzing the frame's function's code (be it using brute force
 244      prologue analysis, or the dwarf2 CFI).  In the case of a dummy
 245      frame, that simply isn't possible.  The PC is either the program
 246      entry point, or some random address on the stack.  Trying to use
 247      that PC to apply standard frame ID unwind techniques is just
 248      asking for trouble.  */
 249   /* Use an architecture specific method to extract the prev's dummy
 250      ID from the next frame.  Note that this method uses
 251      frame_register_unwind to obtain the register values needed to
 252      determine the dummy frame's ID.  */
 253   gdb_assert (gdbarch_unwind_dummy_id_p (current_gdbarch));
 254   (*this_id) = gdbarch_unwind_dummy_id (current_gdbarch, next_frame);
 255   (*this_prologue_cache) = find_dummy_frame ((*this_id).code_addr,
 256                                              (*this_id).stack_addr);
 257 }
 258
 259 static struct frame_unwind dummy_frame_unwind =
 260 {
 261   DUMMY_FRAME,
 262   dummy_frame_this_id,
 263   dummy_frame_prev_register
 264 };
 265
 266 const struct frame_unwind *
 267 dummy_frame_sniffer (struct frame_info *next_frame)
 268 {
 269   CORE_ADDR pc = frame_pc_unwind (next_frame);
 270   if (pc_in_dummy_frame (pc))
 271     return &dummy_frame_unwind;
 272   else
 273     return NULL;
 274 }
 275
 276 static void
 277 fprint_dummy_frames (struct ui_file *file)
 278 {
 279   struct dummy_frame *s;
 280   for (s = dummy_frame_stack; s != NULL; s = s->next)
 281     {
 282       gdb_print_host_address (s, file);
 283       fprintf_unfiltered (file, ":");
 284       fprintf_unfiltered (file, " pc=0x%s", paddr (s->pc));
 285       fprintf_unfiltered (file, " top=0x%s", paddr (s->top));
 286       fprintf_unfiltered (file, " id=");
 287       fprint_frame_id (file, s->id);
 288       fprintf_unfiltered (file, " call_lo=0x%s", paddr (s->call_lo));
 289       fprintf_unfiltered (file, " call_hi=0x%s", paddr (s->call_hi));
 290       fprintf_unfiltered (file, "\n");
 291     }
 292 }
 293
 294 static void
 295 maintenance_print_dummy_frames (char *args, int from_tty)
 296 {
 297   if (args == NULL)
 298     fprint_dummy_frames (gdb_stdout);
 299   else
 300     {
 301       struct ui_file *file = gdb_fopen (args, "w");
 302       if (file == NULL)
 303         perror_with_name ("maintenance print dummy-frames");
 304       fprint_dummy_frames (file);
 305       ui_file_delete (file);
 306     }
 307 }
 308
 309 extern void _initialize_dummy_frame (void);
 310
 311 void
 312 _initialize_dummy_frame (void)
 313 {
 314   add_cmd ("dummy-frames", class_maintenance, maintenance_print_dummy_frames,
 315            "Print the contents of the internal dummy-frame stack.",
 316            &maintenanceprintlist);
 317
 318 }