gdb/frame-unwind.c

   1 /* Definitions for frame unwinder, for GDB, the GNU debugger.
   2
   3    Copyright (C) 2003-2015 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 "gdb_obstack.h"
  28 #include "target.h"
  29
  30 static struct gdbarch_data *frame_unwind_data;
  31
  32 struct frame_unwind_table_entry
  33 {
  34   const struct frame_unwind *unwinder;
  35   struct frame_unwind_table_entry *next;
  36 };
  37
  38 struct frame_unwind_table
  39 {
  40   struct frame_unwind_table_entry *list;
  41   /* The head of the OSABI part of the search list.  */
  42   struct frame_unwind_table_entry **osabi_head;
  43 };
  44
  45 static void *
  46 frame_unwind_init (struct obstack *obstack)
  47 {
  48   struct frame_unwind_table *table
  49     = OBSTACK_ZALLOC (obstack, struct frame_unwind_table);
  50
  51   /* Start the table out with a few default sniffers.  OSABI code
  52      can't override this.  */
  53   table->list = OBSTACK_ZALLOC (obstack, struct frame_unwind_table_entry);
  54   table->list->unwinder = &dummy_frame_unwind;
  55   table->list->next = OBSTACK_ZALLOC (obstack,
  56                                       struct frame_unwind_table_entry);
  57   table->list->next->unwinder = &inline_frame_unwind;
  58   /* The insertion point for OSABI sniffers.  */
  59   table->osabi_head = &table->list->next->next;
  60   return table;
  61 }
  62
  63 void
  64 frame_unwind_prepend_unwinder (struct gdbarch *gdbarch,
  65                                 const struct frame_unwind *unwinder)
  66 {
  67   struct frame_unwind_table *table = gdbarch_data (gdbarch, frame_unwind_data);
  68   struct frame_unwind_table_entry *entry;
  69
  70   /* Insert the new entry at the start of the list.  */
  71   entry = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct frame_unwind_table_entry);
  72   entry->unwinder = unwinder;
  73   entry->next = (*table->osabi_head);
  74   (*table->osabi_head) = entry;
  75 }
  76
  77 void
  78 frame_unwind_append_unwinder (struct gdbarch *gdbarch,
  79                               const struct frame_unwind *unwinder)
  80 {
  81   struct frame_unwind_table *table = gdbarch_data (gdbarch, frame_unwind_data);
  82   struct frame_unwind_table_entry **ip;
  83
  84   /* Find the end of the list and insert the new entry there.  */
  85   for (ip = table->osabi_head; (*ip) != NULL; ip = &(*ip)->next);
  86   (*ip) = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct frame_unwind_table_entry);
  87   (*ip)->unwinder = unwinder;
  88 }
  89
  90 /* Call SNIFFER from UNWINDER.  If it succeeded set UNWINDER for
  91    THIS_FRAME and return 1.  Otherwise the function keeps THIS_FRAME
  92    unchanged and returns 0.  */
  93
  94 static int
  95 frame_unwind_try_unwinder (struct frame_info *this_frame, void **this_cache,
  96                           const struct frame_unwind *unwinder)
  97 {
  98   struct cleanup *old_cleanup;
  99   int res = 0;
 100
 101   old_cleanup = frame_prepare_for_sniffer (this_frame, unwinder);
 102
 103   TRY
 104     {
 105       res = unwinder->sniffer (unwinder, this_frame, this_cache);
 106     }
 107   CATCH (ex, RETURN_MASK_ERROR)
 108     {
 109       if (ex.error == NOT_AVAILABLE_ERROR)
 110         {
 111           /* This usually means that not even the PC is available,
 112              thus most unwinders aren't able to determine if they're
 113              the best fit.  Keep trying.  Fallback prologue unwinders
 114              should always accept the frame.  */
 115           do_cleanups (old_cleanup);
 116           return 0;
 117         }
 118       throw_exception (ex);
 119     }
 120   END_CATCH
 121
 122   if (res)
 123     {
 124       discard_cleanups (old_cleanup);
 125       return 1;
 126     }
 127   else
 128     {
 129       do_cleanups (old_cleanup);
 130       return 0;
 131     }
 132   gdb_assert_not_reached ("frame_unwind_try_unwinder");
 133 }
 134
 135 /* Iterate through sniffers for THIS_FRAME frame until one returns with an
 136    unwinder implementation.  THIS_FRAME->UNWIND must be NULL, it will get set
 137    by this function.  Possibly initialize THIS_CACHE.  */
 138
 139 void
 140 frame_unwind_find_by_frame (struct frame_info *this_frame, void **this_cache)
 141 {
 142   struct gdbarch *gdbarch = get_frame_arch (this_frame);
 143   struct frame_unwind_table *table = gdbarch_data (gdbarch, frame_unwind_data);
 144   struct frame_unwind_table_entry *entry;
 145   const struct frame_unwind *unwinder_from_target;
 146
 147   unwinder_from_target = target_get_unwinder ();
 148   if (unwinder_from_target != NULL
 149       && frame_unwind_try_unwinder (this_frame, this_cache,
 150                                    unwinder_from_target))
 151     return;
 152
 153   unwinder_from_target = target_get_tailcall_unwinder ();
 154   if (unwinder_from_target != NULL
 155       && frame_unwind_try_unwinder (this_frame, this_cache,
 156                                    unwinder_from_target))
 157     return;
 158
 159   for (entry = table->list; entry != NULL; entry = entry->next)
 160     if (frame_unwind_try_unwinder (this_frame, this_cache, entry->unwinder))
 161       return;
 162
 163   internal_error (__FILE__, __LINE__, _("frame_unwind_find_by_frame failed"));
 164 }
 165
 166 /* A default frame sniffer which always accepts the frame.  Used by
 167    fallback prologue unwinders.  */
 168
 169 int
 170 default_frame_sniffer (const struct frame_unwind *self,
 171                        struct frame_info *this_frame,
 172                        void **this_prologue_cache)
 173 {
 174   return 1;
 175 }
 176
 177 /* The default frame unwinder stop_reason callback.  */
 178
 179 enum unwind_stop_reason
 180 default_frame_unwind_stop_reason (struct frame_info *this_frame,
 181                                   void **this_cache)
 182 {
 183   struct frame_id this_id = get_frame_id (this_frame);
 184
 185   if (frame_id_eq (this_id, outer_frame_id))
 186     return UNWIND_OUTERMOST;
 187   else
 188     return UNWIND_NO_REASON;
 189 }
 190
 191 /* Helper functions for value-based register unwinding.  These return
 192    a (possibly lazy) value of the appropriate type.  */
 193
 194 /* Return a value which indicates that FRAME did not save REGNUM.  */
 195
 196 struct value *
 197 frame_unwind_got_optimized (struct frame_info *frame, int regnum)
 198 {
 199   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 200   struct type *type = register_type (gdbarch, regnum);
 201   struct value *val;
 202
 203   /* Return an lval_register value, so that we print it as
 204      "<not saved>".  */
 205   val = allocate_value_lazy (type);
 206   set_value_lazy (val, 0);
 207   mark_value_bytes_optimized_out (val, 0, TYPE_LENGTH (type));
 208   VALUE_LVAL (val) = lval_register;
 209   VALUE_REGNUM (val) = regnum;
 210   VALUE_FRAME_ID (val) = get_frame_id (frame);
 211   return val;
 212 }
 213
 214 /* Return a value which indicates that FRAME copied REGNUM into
 215    register NEW_REGNUM.  */
 216
 217 struct value *
 218 frame_unwind_got_register (struct frame_info *frame,
 219                            int regnum, int new_regnum)
 220 {
 221   return value_of_register_lazy (frame, new_regnum);
 222 }
 223
 224 /* Return a value which indicates that FRAME saved REGNUM in memory at
 225    ADDR.  */
 226
 227 struct value *
 228 frame_unwind_got_memory (struct frame_info *frame, int regnum, CORE_ADDR addr)
 229 {
 230   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 231   struct value *v = value_at_lazy (register_type (gdbarch, regnum), addr);
 232
 233   set_value_stack (v, 1);
 234   return v;
 235 }
 236
 237 /* Return a value which indicates that FRAME's saved version of
 238    REGNUM has a known constant (computed) value of VAL.  */
 239
 240 struct value *
 241 frame_unwind_got_constant (struct frame_info *frame, int regnum,
 242                            ULONGEST val)
 243 {
 244   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 245   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
 246   struct value *reg_val;
 247
 248   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 249   store_unsigned_integer (value_contents_writeable (reg_val),
 250                           register_size (gdbarch, regnum), byte_order, val);
 251   return reg_val;
 252 }
 253
 254 struct value *
 255 frame_unwind_got_bytes (struct frame_info *frame, int regnum, gdb_byte *buf)
 256 {
 257   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 258   struct value *reg_val;
 259
 260   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 261   memcpy (value_contents_raw (reg_val), buf, register_size (gdbarch, regnum));
 262   return reg_val;
 263 }
 264
 265 /* Return a value which indicates that FRAME's saved version of REGNUM
 266    has a known constant (computed) value of ADDR.  Convert the
 267    CORE_ADDR to a target address if necessary.  */
 268
 269 struct value *
 270 frame_unwind_got_address (struct frame_info *frame, int regnum,
 271                           CORE_ADDR addr)
 272 {
 273   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 274   struct value *reg_val;
 275
 276   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 277   pack_long (value_contents_writeable (reg_val),
 278              register_type (gdbarch, regnum), addr);
 279   return reg_val;
 280 }
 281
 282 /* -Wmissing-prototypes */
 283 extern initialize_file_ftype _initialize_frame_unwind;
 284
 285 void
 286 _initialize_frame_unwind (void)
 287 {
 288   frame_unwind_data = gdbarch_data_register_pre_init (frame_unwind_init);
 289 }