gdb/frame-unwind.c

   1 /* Definitions for frame unwinder, for GDB, the GNU debugger.
   2
   3    Copyright (C) 2003-2019 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
  22 /* Local non-gdb includes.  */
  23 #include "dummy-frame.h"
  24 #include "frame-unwind.h"
  25 #include "frame.h"
  26 #include "gdb_obstack.h"
  27 #include "inline-frame.h"
  28 #include "regcache.h"
  29 #include "target.h"
  30 #include "value.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
  70     = (struct frame_unwind_table *) gdbarch_data (gdbarch, frame_unwind_data);
  71   struct frame_unwind_table_entry *entry;
  72
  73   /* Insert the new entry at the start of the list.  */
  74   entry = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct frame_unwind_table_entry);
  75   entry->unwinder = unwinder;
  76   entry->next = (*table->osabi_head);
  77   (*table->osabi_head) = entry;
  78 }
  79
  80 void
  81 frame_unwind_append_unwinder (struct gdbarch *gdbarch,
  82                               const struct frame_unwind *unwinder)
  83 {
  84   struct frame_unwind_table *table
  85     = (struct frame_unwind_table *) gdbarch_data (gdbarch, frame_unwind_data);
  86   struct frame_unwind_table_entry **ip;
  87
  88   /* Find the end of the list and insert the new entry there.  */
  89   for (ip = table->osabi_head; (*ip) != NULL; ip = &(*ip)->next);
  90   (*ip) = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct frame_unwind_table_entry);
  91   (*ip)->unwinder = unwinder;
  92 }
  93
  94 /* Call SNIFFER from UNWINDER.  If it succeeded set UNWINDER for
  95    THIS_FRAME and return 1.  Otherwise the function keeps THIS_FRAME
  96    unchanged and returns 0.  */
  97
  98 static int
  99 frame_unwind_try_unwinder (struct frame_info *this_frame, void **this_cache,
 100                           const struct frame_unwind *unwinder)
 101 {
 102   int res = 0;
 103
 104   frame_prepare_for_sniffer (this_frame, unwinder);
 105
 106   TRY
 107     {
 108       res = unwinder->sniffer (unwinder, this_frame, this_cache);
 109     }
 110   CATCH (ex, RETURN_MASK_ALL)
 111     {
 112       /* Catch all exceptions, caused by either interrupt or error.
 113          Reset *THIS_CACHE.  */
 114       *this_cache = NULL;
 115       frame_cleanup_after_sniffer (this_frame);
 116
 117       if (ex.error == NOT_AVAILABLE_ERROR)
 118         {
 119           /* This usually means that not even the PC is available,
 120              thus most unwinders aren't able to determine if they're
 121              the best fit.  Keep trying.  Fallback prologue unwinders
 122              should always accept the frame.  */
 123           return 0;
 124         }
 125       throw_exception (ex);
 126     }
 127   END_CATCH
 128
 129   if (res)
 130     return 1;
 131   else
 132     {
 133       /* Don't set *THIS_CACHE to NULL here, because sniffer has to do
 134          so.  */
 135       frame_cleanup_after_sniffer (this_frame);
 136       return 0;
 137     }
 138   gdb_assert_not_reached ("frame_unwind_try_unwinder");
 139 }
 140
 141 /* Iterate through sniffers for THIS_FRAME frame until one returns with an
 142    unwinder implementation.  THIS_FRAME->UNWIND must be NULL, it will get set
 143    by this function.  Possibly initialize THIS_CACHE.  */
 144
 145 void
 146 frame_unwind_find_by_frame (struct frame_info *this_frame, void **this_cache)
 147 {
 148   struct gdbarch *gdbarch = get_frame_arch (this_frame);
 149   struct frame_unwind_table *table
 150     = (struct frame_unwind_table *) gdbarch_data (gdbarch, frame_unwind_data);
 151   struct frame_unwind_table_entry *entry;
 152   const struct frame_unwind *unwinder_from_target;
 153
 154   unwinder_from_target = target_get_unwinder ();
 155   if (unwinder_from_target != NULL
 156       && frame_unwind_try_unwinder (this_frame, this_cache,
 157                                    unwinder_from_target))
 158     return;
 159
 160   unwinder_from_target = target_get_tailcall_unwinder ();
 161   if (unwinder_from_target != NULL
 162       && frame_unwind_try_unwinder (this_frame, this_cache,
 163                                    unwinder_from_target))
 164     return;
 165
 166   for (entry = table->list; entry != NULL; entry = entry->next)
 167     if (frame_unwind_try_unwinder (this_frame, this_cache, entry->unwinder))
 168       return;
 169
 170   internal_error (__FILE__, __LINE__, _("frame_unwind_find_by_frame failed"));
 171 }
 172
 173 /* A default frame sniffer which always accepts the frame.  Used by
 174    fallback prologue unwinders.  */
 175
 176 int
 177 default_frame_sniffer (const struct frame_unwind *self,
 178                        struct frame_info *this_frame,
 179                        void **this_prologue_cache)
 180 {
 181   return 1;
 182 }
 183
 184 /* The default frame unwinder stop_reason callback.  */
 185
 186 enum unwind_stop_reason
 187 default_frame_unwind_stop_reason (struct frame_info *this_frame,
 188                                   void **this_cache)
 189 {
 190   struct frame_id this_id = get_frame_id (this_frame);
 191
 192   if (frame_id_eq (this_id, outer_frame_id))
 193     return UNWIND_OUTERMOST;
 194   else
 195     return UNWIND_NO_REASON;
 196 }
 197
 198 /* See frame-unwind.h.  */
 199
 200 CORE_ADDR
 201 default_unwind_pc (struct gdbarch *gdbarch, struct frame_info *next_frame)
 202 {
 203   int pc_regnum = gdbarch_pc_regnum (gdbarch);
 204   CORE_ADDR pc = frame_unwind_register_unsigned (next_frame, pc_regnum);
 205   pc = gdbarch_addr_bits_remove (gdbarch, pc);
 206   return pc;
 207 }
 208
 209 /* See frame-unwind.h.  */
 210
 211 CORE_ADDR
 212 default_unwind_sp (struct gdbarch *gdbarch, struct frame_info *next_frame)
 213 {
 214   int sp_regnum = gdbarch_sp_regnum (gdbarch);
 215   return frame_unwind_register_unsigned (next_frame, sp_regnum);
 216 }
 217
 218 /* Helper functions for value-based register unwinding.  These return
 219    a (possibly lazy) value of the appropriate type.  */
 220
 221 /* Return a value which indicates that FRAME did not save REGNUM.  */
 222
 223 struct value *
 224 frame_unwind_got_optimized (struct frame_info *frame, int regnum)
 225 {
 226   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 227   struct type *type = register_type (gdbarch, regnum);
 228   struct value *val;
 229
 230   /* Return an lval_register value, so that we print it as
 231      "<not saved>".  */
 232   val = allocate_value_lazy (type);
 233   set_value_lazy (val, 0);
 234   mark_value_bytes_optimized_out (val, 0, TYPE_LENGTH (type));
 235   VALUE_LVAL (val) = lval_register;
 236   VALUE_REGNUM (val) = regnum;
 237   VALUE_NEXT_FRAME_ID (val)
 238     = get_frame_id (get_next_frame_sentinel_okay (frame));
 239   return val;
 240 }
 241
 242 /* Return a value which indicates that FRAME copied REGNUM into
 243    register NEW_REGNUM.  */
 244
 245 struct value *
 246 frame_unwind_got_register (struct frame_info *frame,
 247                            int regnum, int new_regnum)
 248 {
 249   return value_of_register_lazy (frame, new_regnum);
 250 }
 251
 252 /* Return a value which indicates that FRAME saved REGNUM in memory at
 253    ADDR.  */
 254
 255 struct value *
 256 frame_unwind_got_memory (struct frame_info *frame, int regnum, CORE_ADDR addr)
 257 {
 258   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 259   struct value *v = value_at_lazy (register_type (gdbarch, regnum), addr);
 260
 261   set_value_stack (v, 1);
 262   return v;
 263 }
 264
 265 /* Return a value which indicates that FRAME's saved version of
 266    REGNUM has a known constant (computed) value of VAL.  */
 267
 268 struct value *
 269 frame_unwind_got_constant (struct frame_info *frame, int regnum,
 270                            ULONGEST val)
 271 {
 272   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 273   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
 274   struct value *reg_val;
 275
 276   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 277   store_unsigned_integer (value_contents_writeable (reg_val),
 278                           register_size (gdbarch, regnum), byte_order, val);
 279   return reg_val;
 280 }
 281
 282 struct value *
 283 frame_unwind_got_bytes (struct frame_info *frame, int regnum, gdb_byte *buf)
 284 {
 285   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 286   struct value *reg_val;
 287
 288   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 289   memcpy (value_contents_raw (reg_val), buf, register_size (gdbarch, regnum));
 290   return reg_val;
 291 }
 292
 293 /* Return a value which indicates that FRAME's saved version of REGNUM
 294    has a known constant (computed) value of ADDR.  Convert the
 295    CORE_ADDR to a target address if necessary.  */
 296
 297 struct value *
 298 frame_unwind_got_address (struct frame_info *frame, int regnum,
 299                           CORE_ADDR addr)
 300 {
 301   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 302   struct value *reg_val;
 303
 304   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 305   pack_long (value_contents_writeable (reg_val),
 306              register_type (gdbarch, regnum), addr);
 307   return reg_val;
 308 }
 309
 310 void
 311 _initialize_frame_unwind (void)
 312 {
 313   frame_unwind_data = gdbarch_data_register_pre_init (frame_unwind_init);
 314 }