gdb/frame-unwind.c

   1 /* Definitions for frame unwinder, for GDB, the GNU debugger.
   2
   3    Copyright (C) 2003-2013 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 "exceptions.h"
  28 #include "gdb_assert.h"
  29 #include "gdb_obstack.h"
  30
  31 static struct gdbarch_data *frame_unwind_data;
  32
  33 struct frame_unwind_table_entry
  34 {
  35   const struct frame_unwind *unwinder;
  36   struct frame_unwind_table_entry *next;
  37 };
  38
  39 struct frame_unwind_table
  40 {
  41   struct frame_unwind_table_entry *list;
  42   /* The head of the OSABI part of the search list.  */
  43   struct frame_unwind_table_entry **osabi_head;
  44 };
  45
  46 static void *
  47 frame_unwind_init (struct obstack *obstack)
  48 {
  49   struct frame_unwind_table *table
  50     = OBSTACK_ZALLOC (obstack, struct frame_unwind_table);
  51
  52   /* Start the table out with a few default sniffers.  OSABI code
  53      can't override this.  */
  54   table->list = OBSTACK_ZALLOC (obstack, struct frame_unwind_table_entry);
  55   table->list->unwinder = &dummy_frame_unwind;
  56   table->list->next = OBSTACK_ZALLOC (obstack,
  57                                       struct frame_unwind_table_entry);
  58   table->list->next->unwinder = &inline_frame_unwind;
  59   /* The insertion point for OSABI sniffers.  */
  60   table->osabi_head = &table->list->next->next;
  61   return table;
  62 }
  63
  64 void
  65 frame_unwind_prepend_unwinder (struct gdbarch *gdbarch,
  66                                 const struct frame_unwind *unwinder)
  67 {
  68   struct frame_unwind_table *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 = gdbarch_data (gdbarch, frame_unwind_data);
  83   struct frame_unwind_table_entry **ip;
  84
  85   /* Find the end of the list and insert the new entry there.  */
  86   for (ip = table->osabi_head; (*ip) != NULL; ip = &(*ip)->next);
  87   (*ip) = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct frame_unwind_table_entry);
  88   (*ip)->unwinder = unwinder;
  89 }
  90
  91 /* Iterate through sniffers for THIS_FRAME frame until one returns with an
  92    unwinder implementation.  THIS_FRAME->UNWIND must be NULL, it will get set
  93    by this function.  Possibly initialize THIS_CACHE.  */
  94
  95 void
  96 frame_unwind_find_by_frame (struct frame_info *this_frame, void **this_cache)
  97 {
  98   struct gdbarch *gdbarch = get_frame_arch (this_frame);
  99   struct frame_unwind_table *table = gdbarch_data (gdbarch, frame_unwind_data);
 100   struct frame_unwind_table_entry *entry;
 101
 102   for (entry = table->list; entry != NULL; entry = entry->next)
 103     {
 104       struct cleanup *old_cleanup;
 105       volatile struct gdb_exception ex;
 106       int res = 0;
 107
 108       old_cleanup = frame_prepare_for_sniffer (this_frame, entry->unwinder);
 109
 110       TRY_CATCH (ex, RETURN_MASK_ERROR)
 111         {
 112           res = entry->unwinder->sniffer (entry->unwinder, this_frame,
 113                                           this_cache);
 114         }
 115       if (ex.reason < 0 && 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         }
 122       else if (ex.reason < 0)
 123         throw_exception (ex);
 124       else if (res)
 125         {
 126           discard_cleanups (old_cleanup);
 127           return;
 128         }
 129
 130       do_cleanups (old_cleanup);
 131     }
 132   internal_error (__FILE__, __LINE__, _("frame_unwind_find_by_frame failed"));
 133 }
 134
 135 /* A default frame sniffer which always accepts the frame.  Used by
 136    fallback prologue unwinders.  */
 137
 138 int
 139 default_frame_sniffer (const struct frame_unwind *self,
 140                        struct frame_info *this_frame,
 141                        void **this_prologue_cache)
 142 {
 143   return 1;
 144 }
 145
 146 /* The default frame unwinder stop_reason callback.  */
 147
 148 enum unwind_stop_reason
 149 default_frame_unwind_stop_reason (struct frame_info *this_frame,
 150                                   void **this_cache)
 151 {
 152   struct frame_id this_id = get_frame_id (this_frame);
 153
 154   if (frame_id_eq (this_id, outer_frame_id))
 155     return UNWIND_OUTERMOST;
 156   else
 157     return UNWIND_NO_REASON;
 158 }
 159
 160 /* Helper functions for value-based register unwinding.  These return
 161    a (possibly lazy) value of the appropriate type.  */
 162
 163 /* Return a value which indicates that FRAME did not save REGNUM.  */
 164
 165 struct value *
 166 frame_unwind_got_optimized (struct frame_info *frame, int regnum)
 167 {
 168   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 169   struct type *type = register_type (gdbarch, regnum);
 170   struct value *val;
 171
 172   /* Return an lval_register value, so that we print it as
 173      "<not saved>".  */
 174   val = allocate_value_lazy (type);
 175   set_value_lazy (val, 0);
 176   set_value_optimized_out (val, 1);
 177   VALUE_LVAL (val) = lval_register;
 178   VALUE_REGNUM (val) = regnum;
 179   VALUE_FRAME_ID (val) = get_frame_id (frame);
 180   return val;
 181 }
 182
 183 /* Return a value which indicates that FRAME copied REGNUM into
 184    register NEW_REGNUM.  */
 185
 186 struct value *
 187 frame_unwind_got_register (struct frame_info *frame,
 188                            int regnum, int new_regnum)
 189 {
 190   return value_of_register_lazy (frame, new_regnum);
 191 }
 192
 193 /* Return a value which indicates that FRAME saved REGNUM in memory at
 194    ADDR.  */
 195
 196 struct value *
 197 frame_unwind_got_memory (struct frame_info *frame, int regnum, CORE_ADDR addr)
 198 {
 199   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 200   struct value *v = value_at_lazy (register_type (gdbarch, regnum), addr);
 201
 202   set_value_stack (v, 1);
 203   return v;
 204 }
 205
 206 /* Return a value which indicates that FRAME's saved version of
 207    REGNUM has a known constant (computed) value of VAL.  */
 208
 209 struct value *
 210 frame_unwind_got_constant (struct frame_info *frame, int regnum,
 211                            ULONGEST val)
 212 {
 213   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 214   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
 215   struct value *reg_val;
 216
 217   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 218   store_unsigned_integer (value_contents_writeable (reg_val),
 219                           register_size (gdbarch, regnum), byte_order, val);
 220   return reg_val;
 221 }
 222
 223 struct value *
 224 frame_unwind_got_bytes (struct frame_info *frame, int regnum, gdb_byte *buf)
 225 {
 226   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 227   struct value *reg_val;
 228
 229   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 230   memcpy (value_contents_raw (reg_val), buf, register_size (gdbarch, regnum));
 231   return reg_val;
 232 }
 233
 234 /* Return a value which indicates that FRAME's saved version of REGNUM
 235    has a known constant (computed) value of ADDR.  Convert the
 236    CORE_ADDR to a target address if necessary.  */
 237
 238 struct value *
 239 frame_unwind_got_address (struct frame_info *frame, int regnum,
 240                           CORE_ADDR addr)
 241 {
 242   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 243   struct value *reg_val;
 244
 245   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 246   pack_long (value_contents_writeable (reg_val),
 247              register_type (gdbarch, regnum), addr);
 248   return reg_val;
 249 }
 250
 251 /* -Wmissing-prototypes */
 252 extern initialize_file_ftype _initialize_frame_unwind;
 253
 254 void
 255 _initialize_frame_unwind (void)
 256 {
 257   frame_unwind_data = gdbarch_data_register_pre_init (frame_unwind_init);
 258 }