gdb/inline-frame.c

   1 /* Inline frame unwinder for GDB.
   2
   3    Copyright (C) 2008-2020 Free Software Foundation, Inc.
   4    Copyright (C) 2019-2020 Advanced Micro Devices, Inc. All rights reserved.
   5
   6    This file is part of GDB.
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  20
  21 #include "defs.h"
  22 #include "breakpoint.h"
  23 #include "inline-frame.h"
  24 #include "addrmap.h"
  25 #include "block.h"
  26 #include "frame-unwind.h"
  27 #include "inferior.h"
  28 #include "gdbthread.h"
  29 #include "regcache.h"
  30 #include "symtab.h"
  31 #include "frame.h"
  32 #include <algorithm>
  33
  34 /* We need to save a few variables for every thread stopped at the
  35    virtual call site of an inlined function.  If there was always a
  36    "struct thread_info", we could hang it off that; in the mean time,
  37    keep our own list.  */
  38 struct inline_state
  39 {
  40   inline_state (thread_info *thread_, int skipped_frames_, CORE_ADDR saved_pc_,
  41                 symbol *skipped_symbol_)
  42     : thread (thread_), skipped_frames (skipped_frames_), saved_pc (saved_pc_),
  43       skipped_symbol (skipped_symbol_)
  44   {}
  45
  46   /* The thread this data relates to.  It should be a currently
  47      stopped thread.  */
  48   thread_info *thread;
  49
  50   /* The number of inlined functions we are skipping.  Each of these
  51      functions can be stepped in to.  */
  52   int skipped_frames;
  53
  54   /* Only valid if SKIPPED_FRAMES is non-zero.  This is the PC used
  55      when calculating SKIPPED_FRAMES; used to check whether we have
  56      moved to a new location by user request.  If so, we invalidate
  57      any skipped frames.  */
  58   CORE_ADDR saved_pc;
  59
  60   /* Only valid if SKIPPED_FRAMES is non-zero.  This is the symbol
  61      of the outermost skipped inline function.  It's used to find the
  62      call site of the current frame.  */
  63   struct symbol *skipped_symbol;
  64 };
  65
  66 static std::vector<inline_state> inline_states;
  67
  68 /* Locate saved inlined frame state for THREAD, if it exists and is
  69    valid.  */
  70
  71 static struct inline_state *
  72 find_inline_frame_state (thread_info *thread)
  73 {
  74   auto state_it = std::find_if (inline_states.begin (), inline_states.end (),
  75                                 [thread] (const inline_state &state)
  76                                   {
  77                                     return state.thread == thread;
  78                                   });
  79
  80   if (state_it == inline_states.end ())
  81     return nullptr;
  82
  83   inline_state &state = *state_it;
  84   struct regcache *regcache = get_thread_regcache (thread);
  85   CORE_ADDR current_pc = regcache_read_pc (regcache);
  86
  87   if (current_pc != state.saved_pc)
  88     {
  89       /* PC has changed - this context is invalid.  Use the
  90          default behavior.  */
  91
  92       unordered_remove (inline_states, state_it);
  93       return nullptr;
  94     }
  95
  96   return &state;
  97 }
  98
  99 /* See inline-frame.h.  */
 100
 101 void
 102 clear_inline_frame_state (process_stratum_target *target, ptid_t filter_ptid)
 103 {
 104   gdb_assert (target != NULL);
 105
 106   if (filter_ptid == minus_one_ptid || filter_ptid.is_pid ())
 107     {
 108       auto matcher = [target, &filter_ptid] (const inline_state &state)
 109         {
 110           thread_info *t = state.thread;
 111           return (t->inf->process_target () == target
 112                   && t->ptid.matches (filter_ptid));
 113         };
 114
 115       auto it = std::remove_if (inline_states.begin (), inline_states.end (),
 116                                 matcher);
 117
 118       inline_states.erase (it, inline_states.end ());
 119
 120       return;
 121     }
 122
 123
 124   auto matcher = [target, &filter_ptid] (const inline_state &state)
 125     {
 126       thread_info *t = state.thread;
 127       return (t->inf->process_target () == target
 128               && filter_ptid == t->ptid);
 129     };
 130
 131   auto it = std::find_if (inline_states.begin (), inline_states.end (),
 132                           matcher);
 133
 134   if (it != inline_states.end ())
 135     unordered_remove (inline_states, it);
 136 }
 137
 138 /* See inline-frame.h.  */
 139
 140 void
 141 clear_inline_frame_state (thread_info *thread)
 142 {
 143   auto it = std::find_if (inline_states.begin (), inline_states.end (),
 144                           [thread] (const inline_state &state)
 145                             {
 146                               return thread == state.thread;
 147                             });
 148
 149   if (it != inline_states.end ())
 150     unordered_remove (inline_states, it);
 151 }
 152
 153 static void
 154 inline_frame_this_id (struct frame_info *this_frame,
 155                       void **this_cache,
 156                       struct frame_id *this_id)
 157 {
 158   struct symbol *func;
 159
 160   /* In order to have a stable frame ID for a given inline function,
 161      we must get the stack / special addresses from the underlying
 162      real frame's this_id method.  So we must call
 163      get_prev_frame_always.  Because we are inlined into some
 164      function, there must be previous frames, so this is safe - as
 165      long as we're careful not to create any cycles.  */
 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 user breakpoint 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 && user_breakpoint_p (bpt))
 313         {
 314           bp_location *loc = s->bp_location_at;
 315           enum bp_loc_type t = loc->loc_type;
 316
 317           if (t == bp_loc_software_breakpoint
 318               || t == bp_loc_hardware_breakpoint)
 319             {
 320               /* If the location has a function symbol, check whether
 321                  the frame was for that inlined function.  If it has
 322                  no function symbol, then assume it is.  I.e., default
 323                  to presenting the stop at the innermost inline
 324                  function.  */
 325               if (loc->symbol == nullptr
 326                   || frame_block == SYMBOL_BLOCK_VALUE (loc->symbol))
 327                 return true;
 328             }
 329         }
 330     }
 331
 332   return false;
 333 }
 334
 335 /* See inline-frame.h.  */
 336
 337 void
 338 skip_inline_frames (thread_info *thread, bpstat stop_chain)
 339 {
 340   const struct block *frame_block, *cur_block;
 341   struct symbol *last_sym = NULL;
 342   int skip_count = 0;
 343
 344   /* This function is called right after reinitializing the frame
 345      cache.  We try not to do more unwinding than absolutely
 346      necessary, for performance.  */
 347   CORE_ADDR this_pc = get_frame_pc (get_current_frame ());
 348   frame_block = block_for_pc (this_pc);
 349
 350   if (frame_block != NULL)
 351     {
 352       cur_block = frame_block;
 353       while (BLOCK_SUPERBLOCK (cur_block))
 354         {
 355           if (block_inlined_p (cur_block))
 356             {
 357               /* See comments in inline_frame_this_id about this use
 358                  of BLOCK_ENTRY_PC.  */
 359               if (BLOCK_ENTRY_PC (cur_block) == this_pc
 360                   || block_starting_point_at (this_pc, cur_block))
 361                 {
 362                   /* Do not skip the inlined frame if execution
 363                      stopped in an inlined frame because of a user
 364                      breakpoint for this inline function.  */
 365                   if (stopped_by_user_bp_inline_frame (cur_block, stop_chain))
 366                     break;
 367
 368                   skip_count++;
 369                   last_sym = BLOCK_FUNCTION (cur_block);
 370                 }
 371               else
 372                 break;
 373             }
 374           else if (BLOCK_FUNCTION (cur_block) != NULL)
 375             break;
 376
 377           cur_block = BLOCK_SUPERBLOCK (cur_block);
 378         }
 379     }
 380
 381   gdb_assert (find_inline_frame_state (thread) == NULL);
 382   inline_states.emplace_back (thread, skip_count, this_pc, last_sym);
 383
 384   if (skip_count != 0)
 385     reinit_frame_cache ();
 386 }
 387
 388 /* Step into an inlined function by unhiding it.  */
 389
 390 void
 391 step_into_inline_frame (thread_info *thread)
 392 {
 393   inline_state *state = find_inline_frame_state (thread);
 394
 395   gdb_assert (state != NULL && state->skipped_frames > 0);
 396   state->skipped_frames--;
 397   reinit_frame_cache ();
 398 }
 399
 400 /* Return the number of hidden functions inlined into the current
 401    frame.  */
 402
 403 int
 404 inline_skipped_frames (thread_info *thread)
 405 {
 406   inline_state *state = find_inline_frame_state (thread);
 407
 408   if (state == NULL)
 409     return 0;
 410   else
 411     return state->skipped_frames;
 412 }
 413
 414 /* If one or more inlined functions are hidden, return the symbol for
 415    the function inlined into the current frame.  */
 416
 417 struct symbol *
 418 inline_skipped_symbol (thread_info *thread)
 419 {
 420   inline_state *state = find_inline_frame_state (thread);
 421
 422   gdb_assert (state != NULL);
 423   return state->skipped_symbol;
 424 }
 425
 426 /* Return the number of functions inlined into THIS_FRAME.  Some of
 427    the callees may not have associated frames (see
 428    skip_inline_frames).  */
 429
 430 int
 431 frame_inlined_callees (struct frame_info *this_frame)
 432 {
 433   struct frame_info *next_frame;
 434   int inline_count = 0;
 435
 436   /* First count how many inlined functions at this PC have frames
 437      above FRAME (are inlined into FRAME).  */
 438   for (next_frame = get_next_frame (this_frame);
 439        next_frame && get_frame_type (next_frame) == INLINE_FRAME;
 440        next_frame = get_next_frame (next_frame))
 441     inline_count++;
 442
 443   /* Simulate some most-inner inlined frames which were suppressed, so
 444      they can be stepped into later.  If we are unwinding already
 445      outer frames from some non-inlined frame this does not apply.  */
 446   if (next_frame == NULL)
 447     inline_count += inline_skipped_frames (inferior_thread ());
 448
 449   return inline_count;
 450 }