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