gdb/frame-unwind.c

   1 /* Definitions for frame unwinder, for GDB, the GNU debugger.
   2
   3    Copyright (C) 2003-2017 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
  68     = (struct frame_unwind_table *) gdbarch_data (gdbarch, frame_unwind_data);
  69   struct frame_unwind_table_entry *entry;
  70
  71   /* Insert the new entry at the start of the list.  */
  72   entry = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct frame_unwind_table_entry);
  73   entry->unwinder = unwinder;
  74   entry->next = (*table->osabi_head);
  75   (*table->osabi_head) = entry;
  76 }
  77
  78 void
  79 frame_unwind_append_unwinder (struct gdbarch *gdbarch,
  80                               const struct frame_unwind *unwinder)
  81 {
  82   struct frame_unwind_table *table
  83     = (struct frame_unwind_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   int res = 0;
 102
 103   old_cleanup = frame_prepare_for_sniffer (this_frame, unwinder);
 104
 105   TRY
 106     {
 107       res = unwinder->sniffer (unwinder, this_frame, this_cache);
 108     }
 109   CATCH (ex, RETURN_MASK_ERROR)
 110     {
 111       if (ex.error == NOT_AVAILABLE_ERROR)
 112         {
 113           /* This usually means that not even the PC is available,
 114              thus most unwinders aren't able to determine if they're
 115              the best fit.  Keep trying.  Fallback prologue unwinders
 116              should always accept the frame.  */
 117           do_cleanups (old_cleanup);
 118           return 0;
 119         }
 120       throw_exception (ex);
 121     }
 122   END_CATCH
 123
 124   if (res)
 125     {
 126       discard_cleanups (old_cleanup);
 127       return 1;
 128     }
 129   else
 130     {
 131       do_cleanups (old_cleanup);
 132       return 0;
 133     }
 134   gdb_assert_not_reached ("frame_unwind_try_unwinder");
 135 }
 136
 137 /* Iterate through sniffers for THIS_FRAME frame until one returns with an
 138    unwinder implementation.  THIS_FRAME->UNWIND must be NULL, it will get set
 139    by this function.  Possibly initialize THIS_CACHE.  */
 140
 141 void
 142 frame_unwind_find_by_frame (struct frame_info *this_frame, void **this_cache)
 143 {
 144   struct gdbarch *gdbarch = get_frame_arch (this_frame);
 145   struct frame_unwind_table *table
 146     = (struct frame_unwind_table *) gdbarch_data (gdbarch, frame_unwind_data);
 147   struct frame_unwind_table_entry *entry;
 148   const struct frame_unwind *unwinder_from_target;
 149
 150   unwinder_from_target = target_get_unwinder ();
 151   if (unwinder_from_target != NULL
 152       && frame_unwind_try_unwinder (this_frame, this_cache,
 153                                    unwinder_from_target))
 154     return;
 155
 156   unwinder_from_target = target_get_tailcall_unwinder ();
 157   if (unwinder_from_target != NULL
 158       && frame_unwind_try_unwinder (this_frame, this_cache,
 159                                    unwinder_from_target))
 160     return;
 161
 162   for (entry = table->list; entry != NULL; entry = entry->next)
 163     if (frame_unwind_try_unwinder (this_frame, this_cache, entry->unwinder))
 164       return;
 165
 166   internal_error (__FILE__, __LINE__, _("frame_unwind_find_by_frame failed"));
 167 }
 168
 169 /* A default frame sniffer which always accepts the frame.  Used by
 170    fallback prologue unwinders.  */
 171
 172 int
 173 default_frame_sniffer (const struct frame_unwind *self,
 174                        struct frame_info *this_frame,
 175                        void **this_prologue_cache)
 176 {
 177   return 1;
 178 }
 179
 180 /* The default frame unwinder stop_reason callback.  */
 181
 182 enum unwind_stop_reason
 183 default_frame_unwind_stop_reason (struct frame_info *this_frame,
 184                                   void **this_cache)
 185 {
 186   struct frame_id this_id = get_frame_id (this_frame);
 187
 188   if (frame_id_eq (this_id, outer_frame_id))
 189     return UNWIND_OUTERMOST;
 190   else
 191     return UNWIND_NO_REASON;
 192 }
 193
 194 /* Helper functions for value-based register unwinding.  These return
 195    a (possibly lazy) value of the appropriate type.  */
 196
 197 /* Return a value which indicates that FRAME did not save REGNUM.  */
 198
 199 struct value *
 200 frame_unwind_got_optimized (struct frame_info *frame, int regnum)
 201 {
 202   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 203   struct type *type = register_type (gdbarch, regnum);
 204   struct value *val;
 205
 206   /* Return an lval_register value, so that we print it as
 207      "<not saved>".  */
 208   val = allocate_value_lazy (type);
 209   set_value_lazy (val, 0);
 210   mark_value_bytes_optimized_out (val, 0, TYPE_LENGTH (type));
 211   VALUE_LVAL (val) = lval_register;
 212   VALUE_REGNUM (val) = regnum;
 213   VALUE_NEXT_FRAME_ID (val)
 214     = get_frame_id (get_next_frame_sentinel_okay (frame));
 215   return val;
 216 }
 217
 218 /* Return a value which indicates that FRAME copied REGNUM into
 219    register NEW_REGNUM.  */
 220
 221 struct value *
 222 frame_unwind_got_register (struct frame_info *frame,
 223                            int regnum, int new_regnum)
 224 {
 225   return value_of_register_lazy (frame, new_regnum);
 226 }
 227
 228 /* Return a value which indicates that FRAME saved REGNUM in memory at
 229    ADDR.  */
 230
 231 struct value *
 232 frame_unwind_got_memory (struct frame_info *frame, int regnum, CORE_ADDR addr)
 233 {
 234   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 235   struct value *v = value_at_lazy (register_type (gdbarch, regnum), addr);
 236
 237   set_value_stack (v, 1);
 238   return v;
 239 }
 240
 241 /* Return a value which indicates that FRAME's saved version of
 242    REGNUM has a known constant (computed) value of VAL.  */
 243
 244 struct value *
 245 frame_unwind_got_constant (struct frame_info *frame, int regnum,
 246                            ULONGEST val)
 247 {
 248   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 249   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
 250   struct value *reg_val;
 251
 252   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 253   store_unsigned_integer (value_contents_writeable (reg_val),
 254                           register_size (gdbarch, regnum), byte_order, val);
 255   return reg_val;
 256 }
 257
 258 struct value *
 259 frame_unwind_got_bytes (struct frame_info *frame, int regnum, gdb_byte *buf)
 260 {
 261   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 262   struct value *reg_val;
 263
 264   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 265   memcpy (value_contents_raw (reg_val), buf, register_size (gdbarch, regnum));
 266   return reg_val;
 267 }
 268
 269 /* Return a value which indicates that FRAME's saved version of REGNUM
 270    has a known constant (computed) value of ADDR.  Convert the
 271    CORE_ADDR to a target address if necessary.  */
 272
 273 struct value *
 274 frame_unwind_got_address (struct frame_info *frame, int regnum,
 275                           CORE_ADDR addr)
 276 {
 277   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 278   struct value *reg_val;
 279
 280   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 281   pack_long (value_contents_writeable (reg_val),
 282              register_type (gdbarch, regnum), addr);
 283   return reg_val;
 284 }
 285
 286 /* -Wmissing-prototypes */
 287 extern initialize_file_ftype _initialize_frame_unwind;
 288
 289 void
 290 _initialize_frame_unwind (void)
 291 {
 292   frame_unwind_data = gdbarch_data_register_pre_init (frame_unwind_init);
 293 }