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_ALL)
 110     {
 111       /* Catch all exceptions, caused by either interrupt or error.
 112          Reset *THIS_CACHE.  */
 113       *this_cache = NULL;
 114       if (ex.error == NOT_AVAILABLE_ERROR)
 115         {
 116           /* This usually means that not even the PC is available,
 117              thus most unwinders aren't able to determine if they're
 118              the best fit.  Keep trying.  Fallback prologue unwinders
 119              should always accept the frame.  */
 120           do_cleanups (old_cleanup);
 121           return 0;
 122         }
 123       throw_exception (ex);
 124     }
 125   END_CATCH
 126
 127   if (res)
 128     {
 129       discard_cleanups (old_cleanup);
 130       return 1;
 131     }
 132   else
 133     {
 134       /* Don't set *THIS_CACHE to NULL here, because sniffer has to do
 135          so.  */
 136       do_cleanups (old_cleanup);
 137       return 0;
 138     }
 139   gdb_assert_not_reached ("frame_unwind_try_unwinder");
 140 }
 141
 142 /* Iterate through sniffers for THIS_FRAME frame until one returns with an
 143    unwinder implementation.  THIS_FRAME->UNWIND must be NULL, it will get set
 144    by this function.  Possibly initialize THIS_CACHE.  */
 145
 146 void
 147 frame_unwind_find_by_frame (struct frame_info *this_frame, void **this_cache)
 148 {
 149   struct gdbarch *gdbarch = get_frame_arch (this_frame);
 150   struct frame_unwind_table *table
 151     = (struct frame_unwind_table *) gdbarch_data (gdbarch, frame_unwind_data);
 152   struct frame_unwind_table_entry *entry;
 153   const struct frame_unwind *unwinder_from_target;
 154
 155   unwinder_from_target = target_get_unwinder ();
 156   if (unwinder_from_target != NULL
 157       && frame_unwind_try_unwinder (this_frame, this_cache,
 158                                    unwinder_from_target))
 159     return;
 160
 161   unwinder_from_target = target_get_tailcall_unwinder ();
 162   if (unwinder_from_target != NULL
 163       && frame_unwind_try_unwinder (this_frame, this_cache,
 164                                    unwinder_from_target))
 165     return;
 166
 167   for (entry = table->list; entry != NULL; entry = entry->next)
 168     if (frame_unwind_try_unwinder (this_frame, this_cache, entry->unwinder))
 169       return;
 170
 171   internal_error (__FILE__, __LINE__, _("frame_unwind_find_by_frame failed"));
 172 }
 173
 174 /* A default frame sniffer which always accepts the frame.  Used by
 175    fallback prologue unwinders.  */
 176
 177 int
 178 default_frame_sniffer (const struct frame_unwind *self,
 179                        struct frame_info *this_frame,
 180                        void **this_prologue_cache)
 181 {
 182   return 1;
 183 }
 184
 185 /* The default frame unwinder stop_reason callback.  */
 186
 187 enum unwind_stop_reason
 188 default_frame_unwind_stop_reason (struct frame_info *this_frame,
 189                                   void **this_cache)
 190 {
 191   struct frame_id this_id = get_frame_id (this_frame);
 192
 193   if (frame_id_eq (this_id, outer_frame_id))
 194     return UNWIND_OUTERMOST;
 195   else
 196     return UNWIND_NO_REASON;
 197 }
 198
 199 /* Helper functions for value-based register unwinding.  These return
 200    a (possibly lazy) value of the appropriate type.  */
 201
 202 /* Return a value which indicates that FRAME did not save REGNUM.  */
 203
 204 struct value *
 205 frame_unwind_got_optimized (struct frame_info *frame, int regnum)
 206 {
 207   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 208   struct type *type = register_type (gdbarch, regnum);
 209   struct value *val;
 210
 211   /* Return an lval_register value, so that we print it as
 212      "<not saved>".  */
 213   val = allocate_value_lazy (type);
 214   set_value_lazy (val, 0);
 215   mark_value_bytes_optimized_out (val, 0, TYPE_LENGTH (type));
 216   VALUE_LVAL (val) = lval_register;
 217   VALUE_REGNUM (val) = regnum;
 218   VALUE_NEXT_FRAME_ID (val)
 219     = get_frame_id (get_next_frame_sentinel_okay (frame));
 220   return val;
 221 }
 222
 223 /* Return a value which indicates that FRAME copied REGNUM into
 224    register NEW_REGNUM.  */
 225
 226 struct value *
 227 frame_unwind_got_register (struct frame_info *frame,
 228                            int regnum, int new_regnum)
 229 {
 230   return value_of_register_lazy (frame, new_regnum);
 231 }
 232
 233 /* Return a value which indicates that FRAME saved REGNUM in memory at
 234    ADDR.  */
 235
 236 struct value *
 237 frame_unwind_got_memory (struct frame_info *frame, int regnum, CORE_ADDR addr)
 238 {
 239   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 240   struct value *v = value_at_lazy (register_type (gdbarch, regnum), addr);
 241
 242   set_value_stack (v, 1);
 243   return v;
 244 }
 245
 246 /* Return a value which indicates that FRAME's saved version of
 247    REGNUM has a known constant (computed) value of VAL.  */
 248
 249 struct value *
 250 frame_unwind_got_constant (struct frame_info *frame, int regnum,
 251                            ULONGEST val)
 252 {
 253   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 254   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
 255   struct value *reg_val;
 256
 257   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 258   store_unsigned_integer (value_contents_writeable (reg_val),
 259                           register_size (gdbarch, regnum), byte_order, val);
 260   return reg_val;
 261 }
 262
 263 struct value *
 264 frame_unwind_got_bytes (struct frame_info *frame, int regnum, gdb_byte *buf)
 265 {
 266   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 267   struct value *reg_val;
 268
 269   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 270   memcpy (value_contents_raw (reg_val), buf, register_size (gdbarch, regnum));
 271   return reg_val;
 272 }
 273
 274 /* Return a value which indicates that FRAME's saved version of REGNUM
 275    has a known constant (computed) value of ADDR.  Convert the
 276    CORE_ADDR to a target address if necessary.  */
 277
 278 struct value *
 279 frame_unwind_got_address (struct frame_info *frame, int regnum,
 280                           CORE_ADDR addr)
 281 {
 282   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 283   struct value *reg_val;
 284
 285   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 286   pack_long (value_contents_writeable (reg_val),
 287              register_type (gdbarch, regnum), addr);
 288   return reg_val;
 289 }
 290
 291 /* -Wmissing-prototypes */
 292 extern initialize_file_ftype _initialize_frame_unwind;
 293
 294 void
 295 _initialize_frame_unwind (void)
 296 {
 297   frame_unwind_data = gdbarch_data_register_pre_init (frame_unwind_init);
 298 }