gdb/frame-unwind.c

   1 /* Definitions for frame unwinder, for GDB, the GNU debugger.
   2
   3    Copyright (C) 2003-2022 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 "gdbsupport/gdb_obstack.h"
  28 #include "target.h"
  29 #include "gdbarch.h"
  30 #include "dwarf2/frame-tailcall.h"
  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 = nullptr;
  41   /* The head of the OSABI part of the search list.  */
  42   struct frame_unwind_table_entry **osabi_head = nullptr;
  43 };
  44
  45 static const registry<gdbarch>::key<struct frame_unwind_table>
  46      frame_unwind_data;
  47
  48 /* A helper function to add an unwinder to a list.  LINK says where to
  49    install the new unwinder.  The new link is returned.  */
  50
  51 static struct frame_unwind_table_entry **
  52 add_unwinder (struct obstack *obstack, const struct frame_unwind *unwinder,
  53               struct frame_unwind_table_entry **link)
  54 {
  55   *link = OBSTACK_ZALLOC (obstack, struct frame_unwind_table_entry);
  56   (*link)->unwinder = unwinder;
  57   return &(*link)->next;
  58 }
  59
  60 static struct frame_unwind_table *
  61 get_frame_unwind_table (struct gdbarch *gdbarch)
  62 {
  63   struct frame_unwind_table *table = frame_unwind_data.get (gdbarch);
  64   if (table != nullptr)
  65     return table;
  66
  67   table = new frame_unwind_table;
  68
  69   /* Start the table out with a few default sniffers.  OSABI code
  70      can't override this.  */
  71   struct frame_unwind_table_entry **link = &table->list;
  72
  73   struct obstack *obstack = gdbarch_obstack (gdbarch);
  74   link = add_unwinder (obstack, &dummy_frame_unwind, link);
  75   /* The DWARF tailcall sniffer must come before the inline sniffer.
  76      Otherwise, we can end up in a situation where a DWARF frame finds
  77      tailcall information, but then the inline sniffer claims a frame
  78      before the tailcall sniffer, resulting in confusion.  This is
  79      safe to do always because the tailcall sniffer can only ever be
  80      activated if the newer frame was created using the DWARF
  81      unwinder, and it also found tailcall information.  */
  82   link = add_unwinder (obstack, &dwarf2_tailcall_frame_unwind, link);
  83   link = add_unwinder (obstack, &inline_frame_unwind, link);
  84
  85   /* The insertion point for OSABI sniffers.  */
  86   table->osabi_head = link;
  87   frame_unwind_data.set (gdbarch, table);
  88
  89   return table;
  90 }
  91
  92 void
  93 frame_unwind_prepend_unwinder (struct gdbarch *gdbarch,
  94                                 const struct frame_unwind *unwinder)
  95 {
  96   struct frame_unwind_table *table = get_frame_unwind_table (gdbarch);
  97   struct frame_unwind_table_entry *entry;
  98
  99   /* Insert the new entry at the start of the list.  */
 100   entry = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct frame_unwind_table_entry);
 101   entry->unwinder = unwinder;
 102   entry->next = (*table->osabi_head);
 103   (*table->osabi_head) = entry;
 104 }
 105
 106 void
 107 frame_unwind_append_unwinder (struct gdbarch *gdbarch,
 108                               const struct frame_unwind *unwinder)
 109 {
 110   struct frame_unwind_table *table = get_frame_unwind_table (gdbarch);
 111   struct frame_unwind_table_entry **ip;
 112
 113   /* Find the end of the list and insert the new entry there.  */
 114   for (ip = table->osabi_head; (*ip) != NULL; ip = &(*ip)->next);
 115   (*ip) = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct frame_unwind_table_entry);
 116   (*ip)->unwinder = unwinder;
 117 }
 118
 119 /* Call SNIFFER from UNWINDER.  If it succeeded set UNWINDER for
 120    THIS_FRAME and return 1.  Otherwise the function keeps THIS_FRAME
 121    unchanged and returns 0.  */
 122
 123 static int
 124 frame_unwind_try_unwinder (frame_info_ptr this_frame, void **this_cache,
 125                           const struct frame_unwind *unwinder)
 126 {
 127   int res = 0;
 128
 129   unsigned int entry_generation = get_frame_cache_generation ();
 130
 131   frame_prepare_for_sniffer (this_frame, unwinder);
 132
 133   try
 134     {
 135       frame_debug_printf ("trying unwinder \"%s\"", unwinder->name);
 136       res = unwinder->sniffer (unwinder, this_frame, this_cache);
 137     }
 138   catch (const gdb_exception &ex)
 139     {
 140       frame_debug_printf ("caught exception: %s", ex.message->c_str ());
 141
 142       /* Catch all exceptions, caused by either interrupt or error.
 143          Reset *THIS_CACHE, unless something reinitialized the frame
 144          cache meanwhile, in which case THIS_FRAME/THIS_CACHE are now
 145          dangling.  */
 146       if (get_frame_cache_generation () == entry_generation)
 147         {
 148           *this_cache = NULL;
 149           frame_cleanup_after_sniffer (this_frame);
 150         }
 151
 152       if (ex.error == NOT_AVAILABLE_ERROR)
 153         {
 154           /* This usually means that not even the PC is available,
 155              thus most unwinders aren't able to determine if they're
 156              the best fit.  Keep trying.  Fallback prologue unwinders
 157              should always accept the frame.  */
 158           return 0;
 159         }
 160       throw;
 161     }
 162
 163   if (res)
 164     {
 165       frame_debug_printf ("yes");
 166       return 1;
 167     }
 168   else
 169     {
 170       frame_debug_printf ("no");
 171       /* Don't set *THIS_CACHE to NULL here, because sniffer has to do
 172          so.  */
 173       frame_cleanup_after_sniffer (this_frame);
 174       return 0;
 175     }
 176   gdb_assert_not_reached ("frame_unwind_try_unwinder");
 177 }
 178
 179 /* Iterate through sniffers for THIS_FRAME frame until one returns with an
 180    unwinder implementation.  THIS_FRAME->UNWIND must be NULL, it will get set
 181    by this function.  Possibly initialize THIS_CACHE.  */
 182
 183 void
 184 frame_unwind_find_by_frame (frame_info_ptr this_frame, void **this_cache)
 185 {
 186   FRAME_SCOPED_DEBUG_ENTER_EXIT;
 187   frame_debug_printf ("this_frame=%d", frame_relative_level (this_frame));
 188
 189   struct gdbarch *gdbarch = get_frame_arch (this_frame);
 190   struct frame_unwind_table *table = get_frame_unwind_table (gdbarch);
 191   struct frame_unwind_table_entry *entry;
 192   const struct frame_unwind *unwinder_from_target;
 193
 194   unwinder_from_target = target_get_unwinder ();
 195   if (unwinder_from_target != NULL
 196       && frame_unwind_try_unwinder (this_frame, this_cache,
 197                                    unwinder_from_target))
 198     return;
 199
 200   unwinder_from_target = target_get_tailcall_unwinder ();
 201   if (unwinder_from_target != NULL
 202       && frame_unwind_try_unwinder (this_frame, this_cache,
 203                                    unwinder_from_target))
 204     return;
 205
 206   for (entry = table->list; entry != NULL; entry = entry->next)
 207     if (frame_unwind_try_unwinder (this_frame, this_cache, entry->unwinder))
 208       return;
 209
 210   internal_error (_("frame_unwind_find_by_frame failed"));
 211 }
 212
 213 /* A default frame sniffer which always accepts the frame.  Used by
 214    fallback prologue unwinders.  */
 215
 216 int
 217 default_frame_sniffer (const struct frame_unwind *self,
 218                        frame_info_ptr this_frame,
 219                        void **this_prologue_cache)
 220 {
 221   return 1;
 222 }
 223
 224 /* The default frame unwinder stop_reason callback.  */
 225
 226 enum unwind_stop_reason
 227 default_frame_unwind_stop_reason (frame_info_ptr this_frame,
 228                                   void **this_cache)
 229 {
 230   struct frame_id this_id = get_frame_id (this_frame);
 231
 232   if (this_id == outer_frame_id)
 233     return UNWIND_OUTERMOST;
 234   else
 235     return UNWIND_NO_REASON;
 236 }
 237
 238 /* See frame-unwind.h.  */
 239
 240 CORE_ADDR
 241 default_unwind_pc (struct gdbarch *gdbarch, frame_info_ptr next_frame)
 242 {
 243   int pc_regnum = gdbarch_pc_regnum (gdbarch);
 244   CORE_ADDR pc = frame_unwind_register_unsigned (next_frame, pc_regnum);
 245   pc = gdbarch_addr_bits_remove (gdbarch, pc);
 246   return pc;
 247 }
 248
 249 /* See frame-unwind.h.  */
 250
 251 CORE_ADDR
 252 default_unwind_sp (struct gdbarch *gdbarch, frame_info_ptr next_frame)
 253 {
 254   int sp_regnum = gdbarch_sp_regnum (gdbarch);
 255   return frame_unwind_register_unsigned (next_frame, sp_regnum);
 256 }
 257
 258 /* Helper functions for value-based register unwinding.  These return
 259    a (possibly lazy) value of the appropriate type.  */
 260
 261 /* Return a value which indicates that FRAME did not save REGNUM.  */
 262
 263 struct value *
 264 frame_unwind_got_optimized (frame_info_ptr frame, int regnum)
 265 {
 266   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 267   struct type *type = register_type (gdbarch, regnum);
 268
 269   return allocate_optimized_out_value (type);
 270 }
 271
 272 /* Return a value which indicates that FRAME copied REGNUM into
 273    register NEW_REGNUM.  */
 274
 275 struct value *
 276 frame_unwind_got_register (frame_info_ptr frame,
 277                            int regnum, int new_regnum)
 278 {
 279   return value_of_register_lazy (frame, new_regnum);
 280 }
 281
 282 /* Return a value which indicates that FRAME saved REGNUM in memory at
 283    ADDR.  */
 284
 285 struct value *
 286 frame_unwind_got_memory (frame_info_ptr frame, int regnum, CORE_ADDR addr)
 287 {
 288   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 289   struct value *v = value_at_lazy (register_type (gdbarch, regnum), addr);
 290
 291   set_value_stack (v, 1);
 292   return v;
 293 }
 294
 295 /* Return a value which indicates that FRAME's saved version of
 296    REGNUM has a known constant (computed) value of VAL.  */
 297
 298 struct value *
 299 frame_unwind_got_constant (frame_info_ptr frame, int regnum,
 300                            ULONGEST val)
 301 {
 302   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 303   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
 304   struct value *reg_val;
 305
 306   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 307   store_unsigned_integer (value_contents_writeable (reg_val).data (),
 308                           register_size (gdbarch, regnum), byte_order, val);
 309   return reg_val;
 310 }
 311
 312 struct value *
 313 frame_unwind_got_bytes (frame_info_ptr frame, int regnum, const gdb_byte *buf)
 314 {
 315   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 316   struct value *reg_val;
 317
 318   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 319   memcpy (value_contents_raw (reg_val).data (), buf,
 320           register_size (gdbarch, regnum));
 321   return reg_val;
 322 }
 323
 324 /* Return a value which indicates that FRAME's saved version of REGNUM
 325    has a known constant (computed) value of ADDR.  Convert the
 326    CORE_ADDR to a target address if necessary.  */
 327
 328 struct value *
 329 frame_unwind_got_address (frame_info_ptr frame, int regnum,
 330                           CORE_ADDR addr)
 331 {
 332   struct gdbarch *gdbarch = frame_unwind_arch (frame);
 333   struct value *reg_val;
 334
 335   reg_val = value_zero (register_type (gdbarch, regnum), not_lval);
 336   pack_long (value_contents_writeable (reg_val).data (),
 337              register_type (gdbarch, regnum), addr);
 338   return reg_val;
 339 }