gdb/frame-unwind.c

   1 /* Definitions for frame unwinder, for GDB, the GNU debugger.
   2
   3    Copyright (C) 2003-2014 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #include "defs.h"
  21 #include "frame.h"
  22 #include "frame-unwind.h"
  23 #include "dummy-frame.h"
  24 #include "inline-frame.h"
  25 #include "value.h"
  26 #include "regcache.h"
  27 #include "exceptions.h"
  28 #include "gdb_assert.h"
  29 #include "gdb_obstack.h"
  30 #include "target.h"
  31
  32 static struct gdbarch_data *frame_unwind_data;
  33
  34 struct frame_unwind_table_entry
  35 {
  36   const struct frame_unwind *unwinder;
  37   struct frame_unwind_table_entry *next;
  38 };
  39
  40 struct frame_unwind_table
  41 {
  42   struct frame_unwind_table_entry *list;
  43   /* The head of the OSABI part of the search list.  */
  44   struct frame_unwind_table_entry **osabi_head;
  45 };
  46
  47 static void *
  48 frame_unwind_init (struct obstack *obstack)
  49 {
  50   struct frame_unwind_table *table
  51     = OBSTACK_ZALLOC (obstack, struct frame_unwind_table);
  52
  53   /* Start the table out with a few default sniffers.  OSABI code
  54      can't override this.  */
  55   table->list = OBSTACK_ZALLOC (obstack, struct frame_unwind_table_entry);
  56   table->list->unwinder = &dummy_frame_unwind;
  57   table->list->next = OBSTACK_ZALLOC (obstack,
  58                                       struct frame_unwind_table_entry);
  59   table->list->next->unwinder = &inline_frame_unwind;
  60   /* The insertion point for OSABI sniffers.  */
  61   table->osabi_head = &table->list->next->next;
  62   return table;
  63 }
  64
  65 void
  66 frame_unwind_prepend_unwinder (struct gdbarch *gdbarch,
  67                                 const struct frame_unwind *unwinder)
  68 {
  69   struct frame_unwind_table *table = gdbarch_data (gdbarch, frame_unwind_data);
  70   struct frame_unwind_table_entry *entry;
  71
  72   /* Insert the new entry at the start of the list.  */
  73   entry = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct frame_unwind_table_entry);
  74   entry->unwinder = unwinder;
  75   entry->next = (*table->osabi_head);
  76   (*table->osabi_head) = entry;
  77 }
  78
  79 void
  80 frame_unwind_append_unwinder (struct gdbarch *gdbarch,
  81                               const struct frame_unwind *unwinder)
  82 {
  83   struct frame_unwind_table *table = gdbarch_data (gdbarch, frame_unwind_data);
  84   struct frame_unwind_table_entry **ip;
  85
  86   /* Find the end of the list and insert the new entry there.  */
  87   for (ip = table->osabi_head; (*ip) != NULL; ip = &(*ip)->next);
  88   (*ip) = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct frame_unwind_table_entry);
  89   (*ip)->unwinder = unwinder;
  90 }
  91
  92 /* Call SNIFFER from UNWINDER.  If it succeeded set UNWINDER for
  93    THIS_FRAME and return 1.  Otherwise the function keeps THIS_FRAME
  94    unchanged and returns 0.  */
  95
  96 static int
  97 frame_unwind_try_unwinder (struct frame_info *this_frame, void **this_cache,
  98                           const struct frame_unwind *unwinder)
  99 {
 100   struct cleanup *old_cleanup;
 101   volatile struct gdb_exception ex;
 102   int res = 0;
 103
 104   old_cleanup = frame_prepare_for_sniffer (this_frame, unwinder);
 105
 106   TRY_CATCH (ex, RETURN_MASK_ERROR)
 107     {
 108       res = unwinder->sniffer (unwinder, this_frame, this_cache);
 109     }
 110   if (ex.reason < 0 && ex.error == NOT_AVAILABLE_ERROR)
 111     {
 112       /* This usually means that not even the PC is available,
 113         thus most unwinders aren't able to determine if they're
 114         the best fit.  Keep trying.  Fallback prologue unwinders
 115         should always accept the frame.  */
 116       do_cleanups (old_cleanup);
 117       return 0;
 118     }
 119   else if (ex.reason < 0)
 120     throw_exception (ex);
 121   else if (res)
 122     {
 123       discard_cleanups (old_cleanup);
 124       return 1;
 125     }
 126   else
 127     {
 128       do_cleanups (old_cleanup);
 129       return 0;
 130     }
 131   gdb_assert_not_reached ("frame_unwind_try_unwinder");
 132 }
 133
 134 /* Iterate through sniffers for THIS_FRAME frame until one returns with an
 135    unwinder implementation.  THIS_FRAME->UNWIND must be NULL, it will get set
 136    by this function.  Possibly initialize THIS_CACHE.  */
 137
 138 void
 139 frame_unwind_find_by_frame (struct frame_info *this_frame, void **this_cache)
 140 {
 141   struct gdbarch *gdbarch = get_frame_arch (this_frame);
 142   struct frame_unwind_table *table = gdbarch_data (gdbarch, frame_unwind_data);
 143   struct frame_unwind_table_entry *entry;
 144   const struct frame_unwind *unwinder_from_target;
 145
 146   unwinder_from_target = target_get_unwinder ();
 147   if (unwinder_from_target != NULL
 148       && frame_unwind_try_unwinder (this_frame, this_cache,
 149                                    unwinder_from_target))
 150     return;
 151
 152   unwinder_from_target = target_get_tailcall_unwinder ();
 153   if (unwinder_from_target != NULL
 154       && frame_unwind_try_unwinder (this_frame, this_cache,
 155                                    unwinder_from_target))
 156     return;
 157
 158   for (entry = table->list; entry != NULL; entry = entry->next)
 159     if (frame_unwind_try_unwinder (this_frame, this_cache, entry->unwinder))
 160       return;
 161
 162   internal_error (__FILE__, __LINE__, _("frame_unwind_find_by_frame failed"));
 163 }
 164
 165 /* A default frame sniffer which always accepts the frame.  Used by
 166    fallback prologue unwinders.  */
 167
 168 int
 169 default_frame_sniffer (const struct frame_unwind *self,
 170                        struct frame_info *this_frame,
 171                        void **this_prologue_cache)
 172 {
 173   return 1;
 174 }
 175
 176 /* The default frame unwinder stop_reason callback.  */
 177
 178 enum unwind_stop_reason
 179 default_frame_unwind_stop_reason (struct frame_info *this_frame,
 180                                   void **this_cache)
 181 {
 182   struct frame_id this_id = get_frame_id (this_frame);
 183
 184   if (frame_id_eq (this_id, outer_frame_id))
 185     return UNWIND_OUTERMOST;
 186   else
 187     return UNWIND_NO_REASON;
 188 }
 189
 190 /* Helper functions for value-based register unwinding.  These return
 191    a (possibly lazy) value of the appropriate type.  */
 192
 193 /* Return a value which indicates that FRAME did not save REGNUM.  */
 194
 195 struct value *
 196 frame_unwind_got_optimized (struct frame_info *frame, int regnum)
 197 {
 198   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 199   struct type *type = register_type (gdbarch, regnum);
 200   struct value *val;
 201
 202   /* Return an lval_register value, so that we print it as
 203      "<not saved>".  */
 204   val = allocate_value_lazy (type);
 205   set_value_lazy (val, 0);
 206   set_value_optimized_out (val, 1);
 207   VALUE_LVAL (val) = lval_register;
 208   VALUE_REGNUM (val) = regnum;
 209   VALUE_FRAME_ID (val) = get_frame_id (frame);
 210   return val;
 211 }
 212
 213 /* Return a value which indicates that FRAME copied REGNUM into
 214    register NEW_REGNUM.  */
 215
 216 struct value *
 217 frame_unwind_got_register (struct frame_info *frame,
 218                            int regnum, int new_regnum)
 219 {
 220   return value_of_register_lazy (frame, new_regnum);
 221 }
 222
 223 /* Return a value which indicates that FRAME saved REGNUM in memory at
 224    ADDR.  */
 225
 226 struct value *
 227 frame_unwind_got_memory (struct frame_info *frame, int regnum, CORE_ADDR addr)
 228 {
 229   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 230   struct value *v = value_at_lazy (register_type (gdbarch, regnum), addr);
 231
 232   set_value_stack (v, 1);
 233   return v;
 234 }
 235
 236 /* Return a value which indicates that FRAME's saved version of
 237    REGNUM has a known constant (computed) value of VAL.  */
 238
 239 struct value *
 240 frame_unwind_got_constant (struct frame_info *frame, int regnum,
 241                            ULONGEST val)
 242 {
 243   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 244   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
 245   struct value *reg_val;
 246
 247   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 248   store_unsigned_integer (value_contents_writeable (reg_val),
 249                           register_size (gdbarch, regnum), byte_order, val);
 250   return reg_val;
 251 }
 252
 253 struct value *
 254 frame_unwind_got_bytes (struct frame_info *frame, int regnum, gdb_byte *buf)
 255 {
 256   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 257   struct value *reg_val;
 258
 259   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 260   memcpy (value_contents_raw (reg_val), buf, register_size (gdbarch, regnum));
 261   return reg_val;
 262 }
 263
 264 /* Return a value which indicates that FRAME's saved version of REGNUM
 265    has a known constant (computed) value of ADDR.  Convert the
 266    CORE_ADDR to a target address if necessary.  */
 267
 268 struct value *
 269 frame_unwind_got_address (struct frame_info *frame, int regnum,
 270                           CORE_ADDR addr)
 271 {
 272   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 273   struct value *reg_val;
 274
 275   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 276   pack_long (value_contents_writeable (reg_val),
 277              register_type (gdbarch, regnum), addr);
 278   return reg_val;
 279 }
 280
 281 /* -Wmissing-prototypes */
 282 extern initialize_file_ftype _initialize_frame_unwind;
 283
 284 void
 285 _initialize_frame_unwind (void)
 286 {
 287   frame_unwind_data = gdbarch_data_register_pre_init (frame_unwind_init);
 288 }