gdb/frame-unwind.c

   1 /* Definitions for frame unwinder, for GDB, the GNU debugger.
   2
   3    Copyright (C) 2003-2018 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   int res = 0;
 101
 102   frame_prepare_for_sniffer (this_frame, unwinder);
 103
 104   TRY
 105     {
 106       res = unwinder->sniffer (unwinder, this_frame, this_cache);
 107     }
 108   CATCH (ex, RETURN_MASK_ALL)
 109     {
 110       /* Catch all exceptions, caused by either interrupt or error.
 111          Reset *THIS_CACHE.  */
 112       *this_cache = NULL;
 113       frame_cleanup_after_sniffer (this_frame);
 114
 115       if (ex.error == NOT_AVAILABLE_ERROR)
 116         {
 117           /* This usually means that not even the PC is available,
 118              thus most unwinders aren't able to determine if they're
 119              the best fit.  Keep trying.  Fallback prologue unwinders
 120              should always accept the frame.  */
 121           return 0;
 122         }
 123       throw_exception (ex);
 124     }
 125   END_CATCH
 126
 127   if (res)
 128     return 1;
 129   else
 130     {
 131       /* Don't set *THIS_CACHE to NULL here, because sniffer has to do
 132          so.  */
 133       frame_cleanup_after_sniffer (this_frame);
 134       return 0;
 135     }
 136   gdb_assert_not_reached ("frame_unwind_try_unwinder");
 137 }
 138
 139 /* Iterate through sniffers for THIS_FRAME frame until one returns with an
 140    unwinder implementation.  THIS_FRAME->UNWIND must be NULL, it will get set
 141    by this function.  Possibly initialize THIS_CACHE.  */
 142
 143 void
 144 frame_unwind_find_by_frame (struct frame_info *this_frame, void **this_cache)
 145 {
 146   struct gdbarch *gdbarch = get_frame_arch (this_frame);
 147   struct frame_unwind_table *table
 148     = (struct frame_unwind_table *) gdbarch_data (gdbarch, frame_unwind_data);
 149   struct frame_unwind_table_entry *entry;
 150   const struct frame_unwind *unwinder_from_target;
 151
 152   unwinder_from_target = target_get_unwinder ();
 153   if (unwinder_from_target != NULL
 154       && frame_unwind_try_unwinder (this_frame, this_cache,
 155                                    unwinder_from_target))
 156     return;
 157
 158   unwinder_from_target = target_get_tailcall_unwinder ();
 159   if (unwinder_from_target != NULL
 160       && frame_unwind_try_unwinder (this_frame, this_cache,
 161                                    unwinder_from_target))
 162     return;
 163
 164   for (entry = table->list; entry != NULL; entry = entry->next)
 165     if (frame_unwind_try_unwinder (this_frame, this_cache, entry->unwinder))
 166       return;
 167
 168   internal_error (__FILE__, __LINE__, _("frame_unwind_find_by_frame failed"));
 169 }
 170
 171 /* A default frame sniffer which always accepts the frame.  Used by
 172    fallback prologue unwinders.  */
 173
 174 int
 175 default_frame_sniffer (const struct frame_unwind *self,
 176                        struct frame_info *this_frame,
 177                        void **this_prologue_cache)
 178 {
 179   return 1;
 180 }
 181
 182 /* The default frame unwinder stop_reason callback.  */
 183
 184 enum unwind_stop_reason
 185 default_frame_unwind_stop_reason (struct frame_info *this_frame,
 186                                   void **this_cache)
 187 {
 188   struct frame_id this_id = get_frame_id (this_frame);
 189
 190   if (frame_id_eq (this_id, outer_frame_id))
 191     return UNWIND_OUTERMOST;
 192   else
 193     return UNWIND_NO_REASON;
 194 }
 195
 196 /* Helper functions for value-based register unwinding.  These return
 197    a (possibly lazy) value of the appropriate type.  */
 198
 199 /* Return a value which indicates that FRAME did not save REGNUM.  */
 200
 201 struct value *
 202 frame_unwind_got_optimized (struct frame_info *frame, int regnum)
 203 {
 204   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 205   struct type *type = register_type (gdbarch, regnum);
 206   struct value *val;
 207
 208   /* Return an lval_register value, so that we print it as
 209      "<not saved>".  */
 210   val = allocate_value_lazy (type);
 211   set_value_lazy (val, 0);
 212   mark_value_bytes_optimized_out (val, 0, TYPE_LENGTH (type));
 213   VALUE_LVAL (val) = lval_register;
 214   VALUE_REGNUM (val) = regnum;
 215   VALUE_NEXT_FRAME_ID (val)
 216     = get_frame_id (get_next_frame_sentinel_okay (frame));
 217   return val;
 218 }
 219
 220 /* Return a value which indicates that FRAME copied REGNUM into
 221    register NEW_REGNUM.  */
 222
 223 struct value *
 224 frame_unwind_got_register (struct frame_info *frame,
 225                            int regnum, int new_regnum)
 226 {
 227   return value_of_register_lazy (frame, new_regnum);
 228 }
 229
 230 /* Return a value which indicates that FRAME saved REGNUM in memory at
 231    ADDR.  */
 232
 233 struct value *
 234 frame_unwind_got_memory (struct frame_info *frame, int regnum, CORE_ADDR addr)
 235 {
 236   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 237   struct value *v = value_at_lazy (register_type (gdbarch, regnum), addr);
 238
 239   set_value_stack (v, 1);
 240   return v;
 241 }
 242
 243 /* Return a value which indicates that FRAME's saved version of
 244    REGNUM has a known constant (computed) value of VAL.  */
 245
 246 struct value *
 247 frame_unwind_got_constant (struct frame_info *frame, int regnum,
 248                            ULONGEST val)
 249 {
 250   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 251   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
 252   struct value *reg_val;
 253
 254   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 255   store_unsigned_integer (value_contents_writeable (reg_val),
 256                           register_size (gdbarch, regnum), byte_order, val);
 257   return reg_val;
 258 }
 259
 260 struct value *
 261 frame_unwind_got_bytes (struct frame_info *frame, int regnum, gdb_byte *buf)
 262 {
 263   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 264   struct value *reg_val;
 265
 266   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 267   memcpy (value_contents_raw (reg_val), buf, register_size (gdbarch, regnum));
 268   return reg_val;
 269 }
 270
 271 /* Return a value which indicates that FRAME's saved version of REGNUM
 272    has a known constant (computed) value of ADDR.  Convert the
 273    CORE_ADDR to a target address if necessary.  */
 274
 275 struct value *
 276 frame_unwind_got_address (struct frame_info *frame, int regnum,
 277                           CORE_ADDR addr)
 278 {
 279   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 280   struct value *reg_val;
 281
 282   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 283   pack_long (value_contents_writeable (reg_val),
 284              register_type (gdbarch, regnum), addr);
 285   return reg_val;
 286 }
 287
 288 void
 289 _initialize_frame_unwind (void)
 290 {
 291   frame_unwind_data = gdbarch_data_register_pre_init (frame_unwind_init);
 292 }