gdb/inline-frame.c

   1 /* Inline frame unwinder for GDB.
   2
   3    Copyright (C) 2008-2021 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 "breakpoint.h"
  22 #include "inline-frame.h"
  23 #include "addrmap.h"
  24 #include "block.h"
  25 #include "frame-unwind.h"
  26 #include "inferior.h"
  27 #include "gdbthread.h"
  28 #include "regcache.h"
  29 #include "symtab.h"
  30 #include "frame.h"
  31 #include <algorithm>
  32
  33 /* We need to save a few variables for every thread stopped at the
  34    virtual call site of an inlined function.  If there was always a
  35    "struct thread_info", we could hang it off that; in the mean time,
  36    keep our own list.  */
  37 struct inline_state
  38 {
  39   inline_state (thread_info *thread_, int skipped_frames_, CORE_ADDR saved_pc_,
  40                 std::vector<symbol *> &&skipped_symbols_)
  41     : thread (thread_), skipped_frames (skipped_frames_), saved_pc (saved_pc_),
  42       skipped_symbols (std::move (skipped_symbols_))
  43   {}
  44
  45   /* The thread this data relates to.  It should be a currently
  46      stopped thread.  */
  47   thread_info *thread;
  48
  49   /* The number of inlined functions we are skipping.  Each of these
  50      functions can be stepped in to.  */
  51   int skipped_frames;
  52
  53   /* Only valid if SKIPPED_FRAMES is non-zero.  This is the PC used
  54      when calculating SKIPPED_FRAMES; used to check whether we have
  55      moved to a new location by user request.  If so, we invalidate
  56      any skipped frames.  */
  57   CORE_ADDR saved_pc;
  58
  59   /* Only valid if SKIPPED_FRAMES is non-zero.  This is the list of all
  60      function symbols that have been skipped, from inner most to outer
  61      most.  It is used to find the call site of the current frame.  */
  62   std::vector<struct symbol *> skipped_symbols;
  63 };
  64
  65 static std::vector<inline_state> inline_states;
  66
  67 /* Locate saved inlined frame state for THREAD, if it exists and is
  68    valid.  */
  69
  70 static struct inline_state *
  71 find_inline_frame_state (thread_info *thread)
  72 {
  73   auto state_it = std::find_if (inline_states.begin (), inline_states.end (),
  74                                 [thread] (const inline_state &state)
  75                                   {
  76                                     return state.thread == thread;
  77                                   });
  78
  79   if (state_it == inline_states.end ())
  80     return nullptr;
  81
  82   inline_state &state = *state_it;
  83   struct regcache *regcache = get_thread_regcache (thread);
  84   CORE_ADDR current_pc = regcache_read_pc (regcache);
  85
  86   if (current_pc != state.saved_pc)
  87     {
  88       /* PC has changed - this context is invalid.  Use the
  89          default behavior.  */
  90
  91       unordered_remove (inline_states, state_it);
  92       return nullptr;
  93     }
  94
  95   return &state;
  96 }
  97
  98 /* See inline-frame.h.  */
  99
 100 void
 101 clear_inline_frame_state (process_stratum_target *target, ptid_t filter_ptid)
 102 {
 103   gdb_assert (target != NULL);
 104
 105   if (filter_ptid == minus_one_ptid || filter_ptid.is_pid ())
 106     {
 107       auto matcher = [target, &filter_ptid] (const inline_state &state)
 108         {
 109           thread_info *t = state.thread;
 110           return (t->inf->process_target () == target
 111                   && t->ptid.matches (filter_ptid));
 112         };
 113
 114       auto it = std::remove_if (inline_states.begin (), inline_states.end (),
 115                                 matcher);
 116
 117       inline_states.erase (it, inline_states.end ());
 118
 119       return;
 120     }
 121
 122
 123   auto matcher = [target, &filter_ptid] (const inline_state &state)
 124     {
 125       thread_info *t = state.thread;
 126       return (t->inf->process_target () == target
 127               && filter_ptid == t->ptid);
 128     };
 129
 130   auto it = std::find_if (inline_states.begin (), inline_states.end (),
 131                           matcher);
 132
 133   if (it != inline_states.end ())
 134     unordered_remove (inline_states, it);
 135 }
 136
 137 /* See inline-frame.h.  */
 138
 139 void
 140 clear_inline_frame_state (thread_info *thread)
 141 {
 142   auto it = std::find_if (inline_states.begin (), inline_states.end (),
 143                           [thread] (const inline_state &state)
 144                             {
 145                               return thread == state.thread;
 146                             });
 147
 148   if (it != inline_states.end ())
 149     unordered_remove (inline_states, it);
 150 }
 151
 152 static void
 153 inline_frame_this_id (struct frame_info *this_frame,
 154                       void **this_cache,
 155                       struct frame_id *this_id)
 156 {
 157   struct symbol *func;
 158
 159   /* In order to have a stable frame ID for a given inline function,
 160      we must get the stack / special addresses from the underlying
 161      real frame's this_id method.  So we must call
 162      get_prev_frame_always.  Because we are inlined into some
 163      function, there must be previous frames, so this is safe - as
 164      long as we're careful not to create any cycles.  See related
 165      comments in get_prev_frame_always_1.  */
 166   *this_id = get_frame_id (get_prev_frame_always (this_frame));
 167
 168   /* We need a valid frame ID, so we need to be based on a valid
 169      frame.  FSF submission NOTE: this would be a good assertion to
 170      apply to all frames, all the time.  That would fix the ambiguity
 171      of null_frame_id (between "no/any frame" and "the outermost
 172      frame").  This will take work.  */
 173   gdb_assert (frame_id_p (*this_id));
 174
 175   /* Future work NOTE: Alexandre Oliva applied a patch to GCC 4.3
 176      which generates DW_AT_entry_pc for inlined functions when
 177      possible.  If this attribute is available, we should use it
 178      in the frame ID (and eventually, to set breakpoints).  */
 179   func = get_frame_function (this_frame);
 180   gdb_assert (func != NULL);
 181   (*this_id).code_addr = BLOCK_ENTRY_PC (SYMBOL_BLOCK_VALUE (func));
 182   (*this_id).artificial_depth++;
 183 }
 184
 185 static struct value *
 186 inline_frame_prev_register (struct frame_info *this_frame, void **this_cache,
 187                             int regnum)
 188 {
 189   /* Use get_frame_register_value instead of
 190      frame_unwind_got_register, to avoid requiring this frame's ID.
 191      This frame's ID depends on the previous frame's ID (unusual), and
 192      the previous frame's ID depends on this frame's unwound
 193      registers.  If unwinding registers from this frame called
 194      get_frame_id, there would be a loop.
 195
 196      Do not copy this code into any other unwinder!  Inlined functions
 197      are special; other unwinders must not have a dependency on the
 198      previous frame's ID, and therefore can and should use
 199      frame_unwind_got_register instead.  */
 200   return get_frame_register_value (this_frame, regnum);
 201 }
 202
 203 /* Check whether we are at an inlining site that does not already
 204    have an associated frame.  */
 205
 206 static int
 207 inline_frame_sniffer (const struct frame_unwind *self,
 208                       struct frame_info *this_frame,
 209                       void **this_cache)
 210 {
 211   CORE_ADDR this_pc;
 212   const struct block *frame_block, *cur_block;
 213   int depth;
 214   struct frame_info *next_frame;
 215   struct inline_state *state = find_inline_frame_state (inferior_thread ());
 216
 217   this_pc = get_frame_address_in_block (this_frame);
 218   frame_block = block_for_pc (this_pc);
 219   if (frame_block == NULL)
 220     return 0;
 221
 222   /* Calculate DEPTH, the number of inlined functions at this
 223      location.  */
 224   depth = 0;
 225   cur_block = frame_block;
 226   while (BLOCK_SUPERBLOCK (cur_block))
 227     {
 228       if (block_inlined_p (cur_block))
 229         depth++;
 230       else if (BLOCK_FUNCTION (cur_block) != NULL)
 231         break;
 232
 233       cur_block = BLOCK_SUPERBLOCK (cur_block);
 234     }
 235
 236   /* Check how many inlined functions already have frames.  */
 237   for (next_frame = get_next_frame (this_frame);
 238        next_frame && get_frame_type (next_frame) == INLINE_FRAME;
 239        next_frame = get_next_frame (next_frame))
 240     {
 241       gdb_assert (depth > 0);
 242       depth--;
 243     }
 244
 245   /* If this is the topmost frame, or all frames above us are inlined,
 246      then check whether we were requested to skip some frames (so they
 247      can be stepped into later).  */
 248   if (state != NULL && state->skipped_frames > 0 && next_frame == NULL)
 249     {
 250       gdb_assert (depth >= state->skipped_frames);
 251       depth -= state->skipped_frames;
 252     }
 253
 254   /* If all the inlined functions here already have frames, then pass
 255      to the normal unwinder for this PC.  */
 256   if (depth == 0)
 257     return 0;
 258
 259   /* If the next frame is an inlined function, but not the outermost, then
 260      we are the next outer.  If it is not an inlined function, then we
 261      are the innermost inlined function of a different real frame.  */
 262   return 1;
 263 }
 264
 265 const struct frame_unwind inline_frame_unwind = {
 266   INLINE_FRAME,
 267   default_frame_unwind_stop_reason,
 268   inline_frame_this_id,
 269   inline_frame_prev_register,
 270   NULL,
 271   inline_frame_sniffer
 272 };
 273
 274 /* Return non-zero if BLOCK, an inlined function block containing PC,
 275    has a group of contiguous instructions starting at PC (but not
 276    before it).  */
 277
 278 static int
 279 block_starting_point_at (CORE_ADDR pc, const struct block *block)
 280 {
 281   const struct blockvector *bv;
 282   const struct block *new_block;
 283
 284   bv = blockvector_for_pc (pc, NULL);
 285   if (BLOCKVECTOR_MAP (bv) == NULL)
 286     return 0;
 287
 288   new_block = (const struct block *) addrmap_find (BLOCKVECTOR_MAP (bv),
 289                                                    pc - 1);
 290   if (new_block == NULL)
 291     return 1;
 292
 293   if (new_block == block || contained_in (new_block, block))
 294     return 0;
 295
 296   /* The immediately preceding address belongs to a different block,
 297      which is not a child of this one.  Treat this as an entrance into
 298      BLOCK.  */
 299   return 1;
 300 }
 301
 302 /* Loop over the stop chain and determine if execution stopped in an
 303    inlined frame because of a breakpoint with a user-specified location
 304    set at FRAME_BLOCK.  */
 305
 306 static bool
 307 stopped_by_user_bp_inline_frame (const block *frame_block, bpstat stop_chain)
 308 {
 309   for (bpstat s = stop_chain; s != NULL; s = s->next)
 310     {
 311       struct breakpoint *bpt = s->breakpoint_at;
 312
 313       if (bpt != NULL
 314           && (user_breakpoint_p (bpt) || bpt->type == bp_until))
 315         {
 316           bp_location *loc = s->bp_location_at.get ();
 317           enum bp_loc_type t = loc->loc_type;
 318
 319           if (t == bp_loc_software_breakpoint
 320               || t == bp_loc_hardware_breakpoint)
 321             {
 322               /* If the location has a function symbol, check whether
 323                  the frame was for that inlined function.  If it has
 324                  no function symbol, then assume it is.  I.e., default
 325                  to presenting the stop at the innermost inline
 326                  function.  */
 327               if (loc->symbol == nullptr
 328                   || frame_block == SYMBOL_BLOCK_VALUE (loc->symbol))
 329                 return true;
 330             }
 331         }
 332     }
 333
 334   return false;
 335 }
 336
 337 /* See inline-frame.h.  */
 338
 339 void
 340 skip_inline_frames (thread_info *thread, bpstat stop_chain)
 341 {
 342   const struct block *frame_block, *cur_block;
 343   std::vector<struct symbol *> skipped_syms;
 344   int skip_count = 0;
 345
 346   /* This function is called right after reinitializing the frame
 347      cache.  We try not to do more unwinding than absolutely
 348      necessary, for performance.  */
 349   CORE_ADDR this_pc = get_frame_pc (get_current_frame ());
 350   frame_block = block_for_pc (this_pc);
 351
 352   if (frame_block != NULL)
 353     {
 354       cur_block = frame_block;
 355       while (BLOCK_SUPERBLOCK (cur_block))
 356         {
 357           if (block_inlined_p (cur_block))
 358             {
 359               /* See comments in inline_frame_this_id about this use
 360                  of BLOCK_ENTRY_PC.  */
 361               if (BLOCK_ENTRY_PC (cur_block) == this_pc
 362                   || block_starting_point_at (this_pc, cur_block))
 363                 {
 364                   /* Do not skip the inlined frame if execution
 365                      stopped in an inlined frame because of a user
 366                      breakpoint for this inline function.  */
 367                   if (stopped_by_user_bp_inline_frame (cur_block, stop_chain))
 368                     break;
 369
 370                   skip_count++;
 371                   skipped_syms.push_back (BLOCK_FUNCTION (cur_block));
 372                 }
 373               else
 374                 break;
 375             }
 376           else if (BLOCK_FUNCTION (cur_block) != NULL)
 377             break;
 378
 379           cur_block = BLOCK_SUPERBLOCK (cur_block);
 380         }
 381     }
 382
 383   gdb_assert (find_inline_frame_state (thread) == NULL);
 384   inline_states.emplace_back (thread, skip_count, this_pc,
 385                               std::move (skipped_syms));
 386
 387   if (skip_count != 0)
 388     reinit_frame_cache ();
 389 }
 390
 391 /* Step into an inlined function by unhiding it.  */
 392
 393 void
 394 step_into_inline_frame (thread_info *thread)
 395 {
 396   inline_state *state = find_inline_frame_state (thread);
 397
 398   gdb_assert (state != NULL && state->skipped_frames > 0);
 399   state->skipped_frames--;
 400   reinit_frame_cache ();
 401 }
 402
 403 /* Return the number of hidden functions inlined into the current
 404    frame.  */
 405
 406 int
 407 inline_skipped_frames (thread_info *thread)
 408 {
 409   inline_state *state = find_inline_frame_state (thread);
 410
 411   if (state == NULL)
 412     return 0;
 413   else
 414     return state->skipped_frames;
 415 }
 416
 417 /* If one or more inlined functions are hidden, return the symbol for
 418    the function inlined into the current frame.  */
 419
 420 struct symbol *
 421 inline_skipped_symbol (thread_info *thread)
 422 {
 423   inline_state *state = find_inline_frame_state (thread);
 424   gdb_assert (state != NULL);
 425
 426   /* This should only be called when we are skipping at least one frame,
 427      hence SKIPPED_FRAMES will be greater than zero when we get here.
 428      We initialise SKIPPED_FRAMES at the same time as we build
 429      SKIPPED_SYMBOLS, hence it should be true that SKIPPED_FRAMES never
 430      indexes outside of the SKIPPED_SYMBOLS vector.  */
 431   gdb_assert (state->skipped_frames > 0);
 432   gdb_assert (state->skipped_frames <= state->skipped_symbols.size ());
 433   return state->skipped_symbols[state->skipped_frames - 1];
 434 }
 435
 436 /* Return the number of functions inlined into THIS_FRAME.  Some of
 437    the callees may not have associated frames (see
 438    skip_inline_frames).  */
 439
 440 int
 441 frame_inlined_callees (struct frame_info *this_frame)
 442 {
 443   struct frame_info *next_frame;
 444   int inline_count = 0;
 445
 446   /* First count how many inlined functions at this PC have frames
 447      above FRAME (are inlined into FRAME).  */
 448   for (next_frame = get_next_frame (this_frame);
 449        next_frame && get_frame_type (next_frame) == INLINE_FRAME;
 450        next_frame = get_next_frame (next_frame))
 451     inline_count++;
 452
 453   /* Simulate some most-inner inlined frames which were suppressed, so
 454      they can be stepped into later.  If we are unwinding already
 455      outer frames from some non-inlined frame this does not apply.  */
 456   if (next_frame == NULL)
 457     inline_count += inline_skipped_frames (inferior_thread ());
 458
 459   return inline_count;
 460 }