gdb/frame-unwind.c

   1 /* Definitions for frame unwinder, for GDB, the GNU debugger.
   2
   3    Copyright (C) 2003-2020 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 #include "gdbarch.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
  69     = (struct frame_unwind_table *) gdbarch_data (gdbarch, frame_unwind_data);
  70   struct frame_unwind_table_entry *entry;
  71
  72   /* Insert the new entry at the start of the list.  */
  73   entry = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct frame_unwind_table_entry);
  74   entry->unwinder = unwinder;
  75   entry->next = (*table->osabi_head);
  76   (*table->osabi_head) = entry;
  77 }
  78
  79 void
  80 frame_unwind_append_unwinder (struct gdbarch *gdbarch,
  81                               const struct frame_unwind *unwinder)
  82 {
  83   struct frame_unwind_table *table
  84     = (struct frame_unwind_table *) gdbarch_data (gdbarch, frame_unwind_data);
  85   struct frame_unwind_table_entry **ip;
  86
  87   /* Find the end of the list and insert the new entry there.  */
  88   for (ip = table->osabi_head; (*ip) != NULL; ip = &(*ip)->next);
  89   (*ip) = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct frame_unwind_table_entry);
  90   (*ip)->unwinder = unwinder;
  91 }
  92
  93 /* Call SNIFFER from UNWINDER.  If it succeeded set UNWINDER for
  94    THIS_FRAME and return 1.  Otherwise the function keeps THIS_FRAME
  95    unchanged and returns 0.  */
  96
  97 static int
  98 frame_unwind_try_unwinder (struct frame_info *this_frame, void **this_cache,
  99                           const struct frame_unwind *unwinder)
 100 {
 101   int res = 0;
 102
 103   frame_prepare_for_sniffer (this_frame, unwinder);
 104
 105   try
 106     {
 107       res = unwinder->sniffer (unwinder, this_frame, this_cache);
 108     }
 109   catch (const gdb_exception &ex)
 110     {
 111       /* Catch all exceptions, caused by either interrupt or error.
 112          Reset *THIS_CACHE.  */
 113       *this_cache = NULL;
 114       frame_cleanup_after_sniffer (this_frame);
 115
 116       if (ex.error == NOT_AVAILABLE_ERROR)
 117         {
 118           /* This usually means that not even the PC is available,
 119              thus most unwinders aren't able to determine if they're
 120              the best fit.  Keep trying.  Fallback prologue unwinders
 121              should always accept the frame.  */
 122           return 0;
 123         }
 124       throw;
 125     }
 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 /* See frame-unwind.h.  */
 197
 198 CORE_ADDR
 199 default_unwind_pc (struct gdbarch *gdbarch, struct frame_info *next_frame)
 200 {
 201   int pc_regnum = gdbarch_pc_regnum (gdbarch);
 202   CORE_ADDR pc = frame_unwind_register_unsigned (next_frame, pc_regnum);
 203   pc = gdbarch_addr_bits_remove (gdbarch, pc);
 204   return pc;
 205 }
 206
 207 /* See frame-unwind.h.  */
 208
 209 CORE_ADDR
 210 default_unwind_sp (struct gdbarch *gdbarch, struct frame_info *next_frame)
 211 {
 212   int sp_regnum = gdbarch_sp_regnum (gdbarch);
 213   return frame_unwind_register_unsigned (next_frame, sp_regnum);
 214 }
 215
 216 /* Helper functions for value-based register unwinding.  These return
 217    a (possibly lazy) value of the appropriate type.  */
 218
 219 /* Return a value which indicates that FRAME did not save REGNUM.  */
 220
 221 struct value *
 222 frame_unwind_got_optimized (struct frame_info *frame, int regnum)
 223 {
 224   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 225   struct type *type = register_type (gdbarch, regnum);
 226   struct value *val;
 227
 228   /* Return an lval_register value, so that we print it as
 229      "<not saved>".  */
 230   val = allocate_value_lazy (type);
 231   set_value_lazy (val, 0);
 232   mark_value_bytes_optimized_out (val, 0, TYPE_LENGTH (type));
 233   VALUE_LVAL (val) = lval_register;
 234   VALUE_REGNUM (val) = regnum;
 235   VALUE_NEXT_FRAME_ID (val)
 236     = get_frame_id (get_next_frame_sentinel_okay (frame));
 237   return val;
 238 }
 239
 240 /* Return a value which indicates that FRAME copied REGNUM into
 241    register NEW_REGNUM.  */
 242
 243 struct value *
 244 frame_unwind_got_register (struct frame_info *frame,
 245                            int regnum, int new_regnum)
 246 {
 247   return value_of_register_lazy (frame, new_regnum);
 248 }
 249
 250 /* Return a value which indicates that FRAME saved REGNUM in memory at
 251    ADDR.  */
 252
 253 struct value *
 254 frame_unwind_got_memory (struct frame_info *frame, int regnum, CORE_ADDR addr)
 255 {
 256   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 257   struct value *v = value_at_lazy (register_type (gdbarch, regnum), addr);
 258
 259   set_value_stack (v, 1);
 260   return v;
 261 }
 262
 263 /* Return a value which indicates that FRAME's saved version of
 264    REGNUM has a known constant (computed) value of VAL.  */
 265
 266 struct value *
 267 frame_unwind_got_constant (struct frame_info *frame, int regnum,
 268                            ULONGEST val)
 269 {
 270   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 271   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
 272   struct value *reg_val;
 273
 274   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 275   store_unsigned_integer (value_contents_writeable (reg_val),
 276                           register_size (gdbarch, regnum), byte_order, val);
 277   return reg_val;
 278 }
 279
 280 struct value *
 281 frame_unwind_got_bytes (struct frame_info *frame, int regnum, gdb_byte *buf)
 282 {
 283   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 284   struct value *reg_val;
 285
 286   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 287   memcpy (value_contents_raw (reg_val), buf, register_size (gdbarch, regnum));
 288   return reg_val;
 289 }
 290
 291 /* Return a value which indicates that FRAME's saved version of REGNUM
 292    has a known constant (computed) value of ADDR.  Convert the
 293    CORE_ADDR to a target address if necessary.  */
 294
 295 struct value *
 296 frame_unwind_got_address (struct frame_info *frame, int regnum,
 297                           CORE_ADDR addr)
 298 {
 299   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 300   struct value *reg_val;
 301
 302   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 303   pack_long (value_contents_writeable (reg_val),
 304              register_type (gdbarch, regnum), addr);
 305   return reg_val;
 306 }
 307
 308 void
 309 _initialize_frame_unwind (void)
 310 {
 311   frame_unwind_data = gdbarch_data_register_pre_init (frame_unwind_init);
 312 }