gdb/inline-frame.c

   1 /* Inline frame unwinder for GDB.
   2
   3    Copyright (C) 2008-2020 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 "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.  */
 165   *this_id = get_frame_id (get_prev_frame_always (this_frame));
 166
 167   /* We need a valid frame ID, so we need to be based on a valid
 168      frame.  FSF submission NOTE: this would be a good assertion to
 169      apply to all frames, all the time.  That would fix the ambiguity
 170      of null_frame_id (between "no/any frame" and "the outermost
 171      frame").  This will take work.  */
 172   gdb_assert (frame_id_p (*this_id));
 173
 174   /* Future work NOTE: Alexandre Oliva applied a patch to GCC 4.3
 175      which generates DW_AT_entry_pc for inlined functions when
 176      possible.  If this attribute is available, we should use it
 177      in the frame ID (and eventually, to set breakpoints).  */
 178   func = get_frame_function (this_frame);
 179   gdb_assert (func != NULL);
 180   (*this_id).code_addr = BLOCK_ENTRY_PC (SYMBOL_BLOCK_VALUE (func));
 181   (*this_id).artificial_depth++;
 182 }
 183
 184 static struct value *
 185 inline_frame_prev_register (struct frame_info *this_frame, void **this_cache,
 186                             int regnum)
 187 {
 188   /* Use get_frame_register_value instead of
 189      frame_unwind_got_register, to avoid requiring this frame's ID.
 190      This frame's ID depends on the previous frame's ID (unusual), and
 191      the previous frame's ID depends on this frame's unwound
 192      registers.  If unwinding registers from this frame called
 193      get_frame_id, there would be a loop.
 194
 195      Do not copy this code into any other unwinder!  Inlined functions
 196      are special; other unwinders must not have a dependency on the
 197      previous frame's ID, and therefore can and should use
 198      frame_unwind_got_register instead.  */
 199   return get_frame_register_value (this_frame, regnum);
 200 }
 201
 202 /* Check whether we are at an inlining site that does not already
 203    have an associated frame.  */
 204
 205 static int
 206 inline_frame_sniffer (const struct frame_unwind *self,
 207                       struct frame_info *this_frame,
 208                       void **this_cache)
 209 {
 210   CORE_ADDR this_pc;
 211   const struct block *frame_block, *cur_block;
 212   int depth;
 213   struct frame_info *next_frame;
 214   struct inline_state *state = find_inline_frame_state (inferior_thread ());
 215
 216   this_pc = get_frame_address_in_block (this_frame);
 217   frame_block = block_for_pc (this_pc);
 218   if (frame_block == NULL)
 219     return 0;
 220
 221   /* Calculate DEPTH, the number of inlined functions at this
 222      location.  */
 223   depth = 0;
 224   cur_block = frame_block;
 225   while (BLOCK_SUPERBLOCK (cur_block))
 226     {
 227       if (block_inlined_p (cur_block))
 228         depth++;
 229       else if (BLOCK_FUNCTION (cur_block) != NULL)
 230         break;
 231
 232       cur_block = BLOCK_SUPERBLOCK (cur_block);
 233     }
 234
 235   /* Check how many inlined functions already have frames.  */
 236   for (next_frame = get_next_frame (this_frame);
 237        next_frame && get_frame_type (next_frame) == INLINE_FRAME;
 238        next_frame = get_next_frame (next_frame))
 239     {
 240       gdb_assert (depth > 0);
 241       depth--;
 242     }
 243
 244   /* If this is the topmost frame, or all frames above us are inlined,
 245      then check whether we were requested to skip some frames (so they
 246      can be stepped into later).  */
 247   if (state != NULL && state->skipped_frames > 0 && next_frame == NULL)
 248     {
 249       gdb_assert (depth >= state->skipped_frames);
 250       depth -= state->skipped_frames;
 251     }
 252
 253   /* If all the inlined functions here already have frames, then pass
 254      to the normal unwinder for this PC.  */
 255   if (depth == 0)
 256     return 0;
 257
 258   /* If the next frame is an inlined function, but not the outermost, then
 259      we are the next outer.  If it is not an inlined function, then we
 260      are the innermost inlined function of a different real frame.  */
 261   return 1;
 262 }
 263
 264 const struct frame_unwind inline_frame_unwind = {
 265   INLINE_FRAME,
 266   default_frame_unwind_stop_reason,
 267   inline_frame_this_id,
 268   inline_frame_prev_register,
 269   NULL,
 270   inline_frame_sniffer
 271 };
 272
 273 /* Return non-zero if BLOCK, an inlined function block containing PC,
 274    has a group of contiguous instructions starting at PC (but not
 275    before it).  */
 276
 277 static int
 278 block_starting_point_at (CORE_ADDR pc, const struct block *block)
 279 {
 280   const struct blockvector *bv;
 281   const struct block *new_block;
 282
 283   bv = blockvector_for_pc (pc, NULL);
 284   if (BLOCKVECTOR_MAP (bv) == NULL)
 285     return 0;
 286
 287   new_block = (const struct block *) addrmap_find (BLOCKVECTOR_MAP (bv),
 288                                                    pc - 1);
 289   if (new_block == NULL)
 290     return 1;
 291
 292   if (new_block == block || contained_in (new_block, block))
 293     return 0;
 294
 295   /* The immediately preceding address belongs to a different block,
 296      which is not a child of this one.  Treat this as an entrance into
 297      BLOCK.  */
 298   return 1;
 299 }
 300
 301 /* Loop over the stop chain and determine if execution stopped in an
 302    inlined frame because of a breakpoint with a user-specified location
 303    set at FRAME_BLOCK.  */
 304
 305 static bool
 306 stopped_by_user_bp_inline_frame (const block *frame_block, bpstat stop_chain)
 307 {
 308   for (bpstat s = stop_chain; s != NULL; s = s->next)
 309     {
 310       struct breakpoint *bpt = s->breakpoint_at;
 311
 312       if (bpt != NULL
 313           && (user_breakpoint_p (bpt) || bpt->type == bp_until))
 314         {
 315           bp_location *loc = s->bp_location_at;
 316           enum bp_loc_type t = loc->loc_type;
 317
 318           if (t == bp_loc_software_breakpoint
 319               || t == bp_loc_hardware_breakpoint)
 320             {
 321               /* If the location has a function symbol, check whether
 322                  the frame was for that inlined function.  If it has
 323                  no function symbol, then assume it is.  I.e., default
 324                  to presenting the stop at the innermost inline
 325                  function.  */
 326               if (loc->symbol == nullptr
 327                   || frame_block == SYMBOL_BLOCK_VALUE (loc->symbol))
 328                 return true;
 329             }
 330         }
 331     }
 332
 333   return false;
 334 }
 335
 336 /* See inline-frame.h.  */
 337
 338 void
 339 skip_inline_frames (thread_info *thread, bpstat stop_chain)
 340 {
 341   const struct block *frame_block, *cur_block;
 342   std::vector<struct symbol *> skipped_syms;
 343   int skip_count = 0;
 344
 345   /* This function is called right after reinitializing the frame
 346      cache.  We try not to do more unwinding than absolutely
 347      necessary, for performance.  */
 348   CORE_ADDR this_pc = get_frame_pc (get_current_frame ());
 349   frame_block = block_for_pc (this_pc);
 350
 351   if (frame_block != NULL)
 352     {
 353       cur_block = frame_block;
 354       while (BLOCK_SUPERBLOCK (cur_block))
 355         {
 356           if (block_inlined_p (cur_block))
 357             {
 358               /* See comments in inline_frame_this_id about this use
 359                  of BLOCK_ENTRY_PC.  */
 360               if (BLOCK_ENTRY_PC (cur_block) == this_pc
 361                   || block_starting_point_at (this_pc, cur_block))
 362                 {
 363                   /* Do not skip the inlined frame if execution
 364                      stopped in an inlined frame because of a user
 365                      breakpoint for this inline function.  */
 366                   if (stopped_by_user_bp_inline_frame (cur_block, stop_chain))
 367                     break;
 368
 369                   skip_count++;
 370                   skipped_syms.push_back (BLOCK_FUNCTION (cur_block));
 371                 }
 372               else
 373                 break;
 374             }
 375           else if (BLOCK_FUNCTION (cur_block) != NULL)
 376             break;
 377
 378           cur_block = BLOCK_SUPERBLOCK (cur_block);
 379         }
 380     }
 381
 382   gdb_assert (find_inline_frame_state (thread) == NULL);
 383   inline_states.emplace_back (thread, skip_count, this_pc,
 384                               std::move (skipped_syms));
 385
 386   if (skip_count != 0)
 387     reinit_frame_cache ();
 388 }
 389
 390 /* Step into an inlined function by unhiding it.  */
 391
 392 void
 393 step_into_inline_frame (thread_info *thread)
 394 {
 395   inline_state *state = find_inline_frame_state (thread);
 396
 397   gdb_assert (state != NULL && state->skipped_frames > 0);
 398   state->skipped_frames--;
 399   reinit_frame_cache ();
 400 }
 401
 402 /* Return the number of hidden functions inlined into the current
 403    frame.  */
 404
 405 int
 406 inline_skipped_frames (thread_info *thread)
 407 {
 408   inline_state *state = find_inline_frame_state (thread);
 409
 410   if (state == NULL)
 411     return 0;
 412   else
 413     return state->skipped_frames;
 414 }
 415
 416 /* If one or more inlined functions are hidden, return the symbol for
 417    the function inlined into the current frame.  */
 418
 419 struct symbol *
 420 inline_skipped_symbol (thread_info *thread)
 421 {
 422   inline_state *state = find_inline_frame_state (thread);
 423   gdb_assert (state != NULL);
 424
 425   /* This should only be called when we are skipping at least one frame,
 426      hence SKIPPED_FRAMES will be greater than zero when we get here.
 427      We initialise SKIPPED_FRAMES at the same time as we build
 428      SKIPPED_SYMBOLS, hence it should be true that SKIPPED_FRAMES never
 429      indexes outside of the SKIPPED_SYMBOLS vector.  */
 430   gdb_assert (state->skipped_frames > 0);
 431   gdb_assert (state->skipped_frames <= state->skipped_symbols.size ());
 432   return state->skipped_symbols[state->skipped_frames - 1];
 433 }
 434
 435 /* Return the number of functions inlined into THIS_FRAME.  Some of
 436    the callees may not have associated frames (see
 437    skip_inline_frames).  */
 438
 439 int
 440 frame_inlined_callees (struct frame_info *this_frame)
 441 {
 442   struct frame_info *next_frame;
 443   int inline_count = 0;
 444
 445   /* First count how many inlined functions at this PC have frames
 446      above FRAME (are inlined into FRAME).  */
 447   for (next_frame = get_next_frame (this_frame);
 448        next_frame && get_frame_type (next_frame) == INLINE_FRAME;
 449        next_frame = get_next_frame (next_frame))
 450     inline_count++;
 451
 452   /* Simulate some most-inner inlined frames which were suppressed, so
 453      they can be stepped into later.  If we are unwinding already
 454      outer frames from some non-inlined frame this does not apply.  */
 455   if (next_frame == NULL)
 456     inline_count += inline_skipped_frames (inferior_thread ());
 457
 458   return inline_count;
 459 }