gdb/inline-frame.c

   1 /* Inline frame unwinder for GDB.
   2
   3    Copyright (C) 2008-2019 Free Software Foundation, Inc.
   4    Copyright (C) 2019 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 /* Forget about any hidden inlined functions in PTID, which is new or
 100    about to be resumed.  PTID may be minus_one_ptid (all processes)
 101    or a PID (all threads in this process).  */
 102
 103 void
 104 clear_inline_frame_state (ptid_t ptid)
 105 {
 106   if (ptid == minus_one_ptid)
 107     {
 108       inline_states.clear ();
 109       return;
 110     }
 111
 112   if (ptid.is_pid ())
 113     {
 114       int pid = ptid.pid ();
 115       auto it = std::remove_if (inline_states.begin (), inline_states.end (),
 116                                 [pid] (const inline_state &state)
 117                                   {
 118                                     return pid == state.thread->inf->pid;
 119                                   });
 120
 121       inline_states.erase (it, inline_states.end ());
 122
 123       return;
 124     }
 125
 126   auto it = std::find_if (inline_states.begin (), inline_states.end (),
 127                           [&ptid] (const inline_state &state)
 128                             {
 129                               return ptid == state.thread->ptid;
 130                             });
 131
 132   if (it != inline_states.end ())
 133     unordered_remove (inline_states, it);
 134 }
 135
 136 static void
 137 inline_frame_this_id (struct frame_info *this_frame,
 138                       void **this_cache,
 139                       struct frame_id *this_id)
 140 {
 141   struct symbol *func;
 142
 143   /* In order to have a stable frame ID for a given inline function,
 144      we must get the stack / special addresses from the underlying
 145      real frame's this_id method.  So we must call
 146      get_prev_frame_always.  Because we are inlined into some
 147      function, there must be previous frames, so this is safe - as
 148      long as we're careful not to create any cycles.  */
 149   *this_id = get_frame_id (get_prev_frame_always (this_frame));
 150
 151   /* We need a valid frame ID, so we need to be based on a valid
 152      frame.  FSF submission NOTE: this would be a good assertion to
 153      apply to all frames, all the time.  That would fix the ambiguity
 154      of null_frame_id (between "no/any frame" and "the outermost
 155      frame").  This will take work.  */
 156   gdb_assert (frame_id_p (*this_id));
 157
 158   /* Future work NOTE: Alexandre Oliva applied a patch to GCC 4.3
 159      which generates DW_AT_entry_pc for inlined functions when
 160      possible.  If this attribute is available, we should use it
 161      in the frame ID (and eventually, to set breakpoints).  */
 162   func = get_frame_function (this_frame);
 163   gdb_assert (func != NULL);
 164   (*this_id).code_addr = BLOCK_ENTRY_PC (SYMBOL_BLOCK_VALUE (func));
 165   (*this_id).artificial_depth++;
 166 }
 167
 168 static struct value *
 169 inline_frame_prev_register (struct frame_info *this_frame, void **this_cache,
 170                             int regnum)
 171 {
 172   /* Use get_frame_register_value instead of
 173      frame_unwind_got_register, to avoid requiring this frame's ID.
 174      This frame's ID depends on the previous frame's ID (unusual), and
 175      the previous frame's ID depends on this frame's unwound
 176      registers.  If unwinding registers from this frame called
 177      get_frame_id, there would be a loop.
 178
 179      Do not copy this code into any other unwinder!  Inlined functions
 180      are special; other unwinders must not have a dependency on the
 181      previous frame's ID, and therefore can and should use
 182      frame_unwind_got_register instead.  */
 183   return get_frame_register_value (this_frame, regnum);
 184 }
 185
 186 /* Check whether we are at an inlining site that does not already
 187    have an associated frame.  */
 188
 189 static int
 190 inline_frame_sniffer (const struct frame_unwind *self,
 191                       struct frame_info *this_frame,
 192                       void **this_cache)
 193 {
 194   CORE_ADDR this_pc;
 195   const struct block *frame_block, *cur_block;
 196   int depth;
 197   struct frame_info *next_frame;
 198   struct inline_state *state = find_inline_frame_state (inferior_thread ());
 199
 200   this_pc = get_frame_address_in_block (this_frame);
 201   frame_block = block_for_pc (this_pc);
 202   if (frame_block == NULL)
 203     return 0;
 204
 205   /* Calculate DEPTH, the number of inlined functions at this
 206      location.  */
 207   depth = 0;
 208   cur_block = frame_block;
 209   while (BLOCK_SUPERBLOCK (cur_block))
 210     {
 211       if (block_inlined_p (cur_block))
 212         depth++;
 213       else if (BLOCK_FUNCTION (cur_block) != NULL)
 214         break;
 215
 216       cur_block = BLOCK_SUPERBLOCK (cur_block);
 217     }
 218
 219   /* Check how many inlined functions already have frames.  */
 220   for (next_frame = get_next_frame (this_frame);
 221        next_frame && get_frame_type (next_frame) == INLINE_FRAME;
 222        next_frame = get_next_frame (next_frame))
 223     {
 224       gdb_assert (depth > 0);
 225       depth--;
 226     }
 227
 228   /* If this is the topmost frame, or all frames above us are inlined,
 229      then check whether we were requested to skip some frames (so they
 230      can be stepped into later).  */
 231   if (state != NULL && state->skipped_frames > 0 && next_frame == NULL)
 232     {
 233       gdb_assert (depth >= state->skipped_frames);
 234       depth -= state->skipped_frames;
 235     }
 236
 237   /* If all the inlined functions here already have frames, then pass
 238      to the normal unwinder for this PC.  */
 239   if (depth == 0)
 240     return 0;
 241
 242   /* If the next frame is an inlined function, but not the outermost, then
 243      we are the next outer.  If it is not an inlined function, then we
 244      are the innermost inlined function of a different real frame.  */
 245   return 1;
 246 }
 247
 248 const struct frame_unwind inline_frame_unwind = {
 249   INLINE_FRAME,
 250   default_frame_unwind_stop_reason,
 251   inline_frame_this_id,
 252   inline_frame_prev_register,
 253   NULL,
 254   inline_frame_sniffer
 255 };
 256
 257 /* Return non-zero if BLOCK, an inlined function block containing PC,
 258    has a group of contiguous instructions starting at PC (but not
 259    before it).  */
 260
 261 static int
 262 block_starting_point_at (CORE_ADDR pc, const struct block *block)
 263 {
 264   const struct blockvector *bv;
 265   const struct block *new_block;
 266
 267   bv = blockvector_for_pc (pc, NULL);
 268   if (BLOCKVECTOR_MAP (bv) == NULL)
 269     return 0;
 270
 271   new_block = (const struct block *) addrmap_find (BLOCKVECTOR_MAP (bv),
 272                                                    pc - 1);
 273   if (new_block == NULL)
 274     return 1;
 275
 276   if (new_block == block || contained_in (new_block, block))
 277     return 0;
 278
 279   /* The immediately preceding address belongs to a different block,
 280      which is not a child of this one.  Treat this as an entrance into
 281      BLOCK.  */
 282   return 1;
 283 }
 284
 285 /* Loop over the stop chain and determine if execution stopped in an
 286    inlined frame because of a user breakpoint set at FRAME_BLOCK.  */
 287
 288 static bool
 289 stopped_by_user_bp_inline_frame (const block *frame_block, bpstat stop_chain)
 290 {
 291   for (bpstat s = stop_chain; s != NULL; s = s->next)
 292     {
 293       struct breakpoint *bpt = s->breakpoint_at;
 294
 295       if (bpt != NULL && user_breakpoint_p (bpt))
 296         {
 297           bp_location *loc = s->bp_location_at;
 298           enum bp_loc_type t = loc->loc_type;
 299
 300           if (t == bp_loc_software_breakpoint
 301               || t == bp_loc_hardware_breakpoint)
 302             {
 303               /* If the location has a function symbol, check whether
 304                  the frame was for that inlined function.  If it has
 305                  no function symbol, then assume it is.  I.e., default
 306                  to presenting the stop at the innermost inline
 307                  function.  */
 308               if (loc->symbol == nullptr
 309                   || frame_block == SYMBOL_BLOCK_VALUE (loc->symbol))
 310                 return true;
 311             }
 312         }
 313     }
 314
 315   return false;
 316 }
 317
 318 /* See inline-frame.h.  */
 319
 320 void
 321 skip_inline_frames (thread_info *thread, bpstat stop_chain)
 322 {
 323   const struct block *frame_block, *cur_block;
 324   struct symbol *last_sym = NULL;
 325   int skip_count = 0;
 326
 327   /* This function is called right after reinitializing the frame
 328      cache.  We try not to do more unwinding than absolutely
 329      necessary, for performance.  */
 330   CORE_ADDR this_pc = get_frame_pc (get_current_frame ());
 331   frame_block = block_for_pc (this_pc);
 332
 333   if (frame_block != NULL)
 334     {
 335       cur_block = frame_block;
 336       while (BLOCK_SUPERBLOCK (cur_block))
 337         {
 338           if (block_inlined_p (cur_block))
 339             {
 340               /* See comments in inline_frame_this_id about this use
 341                  of BLOCK_ENTRY_PC.  */
 342               if (BLOCK_ENTRY_PC (cur_block) == this_pc
 343                   || block_starting_point_at (this_pc, cur_block))
 344                 {
 345                   /* Do not skip the inlined frame if execution
 346                      stopped in an inlined frame because of a user
 347                      breakpoint for this inline function.  */
 348                   if (stopped_by_user_bp_inline_frame (cur_block, stop_chain))
 349                     break;
 350
 351                   skip_count++;
 352                   last_sym = BLOCK_FUNCTION (cur_block);
 353                 }
 354               else
 355                 break;
 356             }
 357           else if (BLOCK_FUNCTION (cur_block) != NULL)
 358             break;
 359
 360           cur_block = BLOCK_SUPERBLOCK (cur_block);
 361         }
 362     }
 363
 364   gdb_assert (find_inline_frame_state (thread) == NULL);
 365   inline_states.emplace_back (thread, skip_count, this_pc, last_sym);
 366
 367   if (skip_count != 0)
 368     reinit_frame_cache ();
 369 }
 370
 371 /* Step into an inlined function by unhiding it.  */
 372
 373 void
 374 step_into_inline_frame (thread_info *thread)
 375 {
 376   inline_state *state = find_inline_frame_state (thread);
 377
 378   gdb_assert (state != NULL && state->skipped_frames > 0);
 379   state->skipped_frames--;
 380   reinit_frame_cache ();
 381 }
 382
 383 /* Return the number of hidden functions inlined into the current
 384    frame.  */
 385
 386 int
 387 inline_skipped_frames (thread_info *thread)
 388 {
 389   inline_state *state = find_inline_frame_state (thread);
 390
 391   if (state == NULL)
 392     return 0;
 393   else
 394     return state->skipped_frames;
 395 }
 396
 397 /* If one or more inlined functions are hidden, return the symbol for
 398    the function inlined into the current frame.  */
 399
 400 struct symbol *
 401 inline_skipped_symbol (thread_info *thread)
 402 {
 403   inline_state *state = find_inline_frame_state (thread);
 404
 405   gdb_assert (state != NULL);
 406   return state->skipped_symbol;
 407 }
 408
 409 /* Return the number of functions inlined into THIS_FRAME.  Some of
 410    the callees may not have associated frames (see
 411    skip_inline_frames).  */
 412
 413 int
 414 frame_inlined_callees (struct frame_info *this_frame)
 415 {
 416   struct frame_info *next_frame;
 417   int inline_count = 0;
 418
 419   /* First count how many inlined functions at this PC have frames
 420      above FRAME (are inlined into FRAME).  */
 421   for (next_frame = get_next_frame (this_frame);
 422        next_frame && get_frame_type (next_frame) == INLINE_FRAME;
 423        next_frame = get_next_frame (next_frame))
 424     inline_count++;
 425
 426   /* Simulate some most-inner inlined frames which were suppressed, so
 427      they can be stepped into later.  If we are unwinding already
 428      outer frames from some non-inlined frame this does not apply.  */
 429   if (next_frame == NULL)
 430     inline_count += inline_skipped_frames (inferior_thread ());
 431
 432   return inline_count;
 433 }