gdb/inline-frame.c

   1 /* Inline frame unwinder for GDB.
   2
   3    Copyright (C) 2008-2018 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 "regcache.h"
  28 #include "symtab.h"
  29 #include "vec.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 (ptid_t ptid_, int skipped_frames_, CORE_ADDR saved_pc_,
  40                 symbol *skipped_symbol_)
  41     : ptid (ptid_), skipped_frames (skipped_frames_), saved_pc (saved_pc_),
  42       skipped_symbol (skipped_symbol_)
  43   {}
  44
  45   /* The thread this data relates to.  It should be a currently
  46      stopped thread; we assume thread IDs never change while the
  47      thread is stopped.  */
  48   ptid_t ptid;
  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 PTID, if it exists
  69    and is valid.  */
  70
  71 static struct inline_state *
  72 find_inline_frame_state (ptid_t ptid)
  73 {
  74   auto state_it = std::find_if (inline_states.begin (), inline_states.end (),
  75                                 [&ptid] (const inline_state &state)
  76                                   {
  77                                     return ptid == state.ptid;
  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 (ptid);
  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.ptid.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.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   /* For now, require we don't match outer_frame_id either (see
 159      comment above).  */
 160   gdb_assert (!frame_id_eq (*this_id, outer_frame_id));
 161
 162   /* Future work NOTE: Alexandre Oliva applied a patch to GCC 4.3
 163      which generates DW_AT_entry_pc for inlined functions when
 164      possible.  If this attribute is available, we should use it
 165      in the frame ID (and eventually, to set breakpoints).  */
 166   func = get_frame_function (this_frame);
 167   gdb_assert (func != NULL);
 168   (*this_id).code_addr = BLOCK_START (SYMBOL_BLOCK_VALUE (func));
 169   (*this_id).artificial_depth++;
 170 }
 171
 172 static struct value *
 173 inline_frame_prev_register (struct frame_info *this_frame, void **this_cache,
 174                             int regnum)
 175 {
 176   /* Use get_frame_register_value instead of
 177      frame_unwind_got_register, to avoid requiring this frame's ID.
 178      This frame's ID depends on the previous frame's ID (unusual), and
 179      the previous frame's ID depends on this frame's unwound
 180      registers.  If unwinding registers from this frame called
 181      get_frame_id, there would be a loop.
 182
 183      Do not copy this code into any other unwinder!  Inlined functions
 184      are special; other unwinders must not have a dependency on the
 185      previous frame's ID, and therefore can and should use
 186      frame_unwind_got_register instead.  */
 187   return get_frame_register_value (this_frame, regnum);
 188 }
 189
 190 /* Check whether we are at an inlining site that does not already
 191    have an associated frame.  */
 192
 193 static int
 194 inline_frame_sniffer (const struct frame_unwind *self,
 195                       struct frame_info *this_frame,
 196                       void **this_cache)
 197 {
 198   CORE_ADDR this_pc;
 199   const struct block *frame_block, *cur_block;
 200   int depth;
 201   struct frame_info *next_frame;
 202   struct inline_state *state = find_inline_frame_state (inferior_ptid);
 203
 204   this_pc = get_frame_address_in_block (this_frame);
 205   frame_block = block_for_pc (this_pc);
 206   if (frame_block == NULL)
 207     return 0;
 208
 209   /* Calculate DEPTH, the number of inlined functions at this
 210      location.  */
 211   depth = 0;
 212   cur_block = frame_block;
 213   while (BLOCK_SUPERBLOCK (cur_block))
 214     {
 215       if (block_inlined_p (cur_block))
 216         depth++;
 217       else if (BLOCK_FUNCTION (cur_block) != NULL)
 218         break;
 219
 220       cur_block = BLOCK_SUPERBLOCK (cur_block);
 221     }
 222
 223   /* Check how many inlined functions already have frames.  */
 224   for (next_frame = get_next_frame (this_frame);
 225        next_frame && get_frame_type (next_frame) == INLINE_FRAME;
 226        next_frame = get_next_frame (next_frame))
 227     {
 228       gdb_assert (depth > 0);
 229       depth--;
 230     }
 231
 232   /* If this is the topmost frame, or all frames above us are inlined,
 233      then check whether we were requested to skip some frames (so they
 234      can be stepped into later).  */
 235   if (state != NULL && state->skipped_frames > 0 && next_frame == NULL)
 236     {
 237       gdb_assert (depth >= state->skipped_frames);
 238       depth -= state->skipped_frames;
 239     }
 240
 241   /* If all the inlined functions here already have frames, then pass
 242      to the normal unwinder for this PC.  */
 243   if (depth == 0)
 244     return 0;
 245
 246   /* If the next frame is an inlined function, but not the outermost, then
 247      we are the next outer.  If it is not an inlined function, then we
 248      are the innermost inlined function of a different real frame.  */
 249   return 1;
 250 }
 251
 252 const struct frame_unwind inline_frame_unwind = {
 253   INLINE_FRAME,
 254   default_frame_unwind_stop_reason,
 255   inline_frame_this_id,
 256   inline_frame_prev_register,
 257   NULL,
 258   inline_frame_sniffer
 259 };
 260
 261 /* Return non-zero if BLOCK, an inlined function block containing PC,
 262    has a group of contiguous instructions starting at PC (but not
 263    before it).  */
 264
 265 static int
 266 block_starting_point_at (CORE_ADDR pc, const struct block *block)
 267 {
 268   const struct blockvector *bv;
 269   struct block *new_block;
 270
 271   bv = blockvector_for_pc (pc, NULL);
 272   if (BLOCKVECTOR_MAP (bv) == NULL)
 273     return 0;
 274
 275   new_block = (struct block *) addrmap_find (BLOCKVECTOR_MAP (bv), pc - 1);
 276   if (new_block == NULL)
 277     return 1;
 278
 279   if (new_block == block || contained_in (new_block, block))
 280     return 0;
 281
 282   /* The immediately preceding address belongs to a different block,
 283      which is not a child of this one.  Treat this as an entrance into
 284      BLOCK.  */
 285   return 1;
 286 }
 287
 288 /* Loop over the stop chain and determine if execution stopped in an
 289    inlined frame because of a user breakpoint.  THIS_PC is the current
 290    frame's PC.  */
 291
 292 static bool
 293 stopped_by_user_bp_inline_frame (CORE_ADDR this_pc, bpstat stop_chain)
 294 {
 295   for (bpstat s = stop_chain; s != NULL; s = s->next)
 296     {
 297       struct breakpoint *bpt = s->breakpoint_at;
 298
 299       if (bpt != NULL && user_breakpoint_p (bpt))
 300         {
 301           bp_location *loc = s->bp_location_at;
 302           enum bp_loc_type t = loc->loc_type;
 303
 304           if (loc->address == this_pc
 305               && (t == bp_loc_software_breakpoint
 306                   || t == bp_loc_hardware_breakpoint))
 307             return true;
 308         }
 309     }
 310
 311   return false;
 312 }
 313
 314 /* See inline-frame.h.  */
 315
 316 void
 317 skip_inline_frames (ptid_t ptid, bpstat stop_chain)
 318 {
 319   const struct block *frame_block, *cur_block;
 320   struct symbol *last_sym = NULL;
 321   int skip_count = 0;
 322
 323   /* This function is called right after reinitializing the frame
 324      cache.  We try not to do more unwinding than absolutely
 325      necessary, for performance.  */
 326   CORE_ADDR this_pc = get_frame_pc (get_current_frame ());
 327   frame_block = block_for_pc (this_pc);
 328
 329   if (frame_block != NULL)
 330     {
 331       cur_block = frame_block;
 332       while (BLOCK_SUPERBLOCK (cur_block))
 333         {
 334           if (block_inlined_p (cur_block))
 335             {
 336               /* See comments in inline_frame_this_id about this use
 337                  of BLOCK_START.  */
 338               if (BLOCK_START (cur_block) == this_pc
 339                   || block_starting_point_at (this_pc, cur_block))
 340                 {
 341                   /* Do not skip the inlined frame if execution
 342                      stopped in an inlined frame because of a user
 343                      breakpoint.  */
 344                   if (!stopped_by_user_bp_inline_frame (this_pc, stop_chain))
 345                     {
 346                       skip_count++;
 347                       last_sym = BLOCK_FUNCTION (cur_block);
 348                     }
 349                 }
 350               else
 351                 break;
 352             }
 353           else if (BLOCK_FUNCTION (cur_block) != NULL)
 354             break;
 355
 356           cur_block = BLOCK_SUPERBLOCK (cur_block);
 357         }
 358     }
 359
 360   gdb_assert (find_inline_frame_state (ptid) == NULL);
 361   inline_states.emplace_back (ptid, skip_count, this_pc, last_sym);
 362
 363   if (skip_count != 0)
 364     reinit_frame_cache ();
 365 }
 366
 367 /* Step into an inlined function by unhiding it.  */
 368
 369 void
 370 step_into_inline_frame (ptid_t ptid)
 371 {
 372   struct inline_state *state = find_inline_frame_state (ptid);
 373
 374   gdb_assert (state != NULL && state->skipped_frames > 0);
 375   state->skipped_frames--;
 376   reinit_frame_cache ();
 377 }
 378
 379 /* Return the number of hidden functions inlined into the current
 380    frame.  */
 381
 382 int
 383 inline_skipped_frames (ptid_t ptid)
 384 {
 385   struct inline_state *state = find_inline_frame_state (ptid);
 386
 387   if (state == NULL)
 388     return 0;
 389   else
 390     return state->skipped_frames;
 391 }
 392
 393 /* If one or more inlined functions are hidden, return the symbol for
 394    the function inlined into the current frame.  */
 395
 396 struct symbol *
 397 inline_skipped_symbol (ptid_t ptid)
 398 {
 399   struct inline_state *state = find_inline_frame_state (ptid);
 400
 401   gdb_assert (state != NULL);
 402   return state->skipped_symbol;
 403 }
 404
 405 /* Return the number of functions inlined into THIS_FRAME.  Some of
 406    the callees may not have associated frames (see
 407    skip_inline_frames).  */
 408
 409 int
 410 frame_inlined_callees (struct frame_info *this_frame)
 411 {
 412   struct frame_info *next_frame;
 413   int inline_count = 0;
 414
 415   /* First count how many inlined functions at this PC have frames
 416      above FRAME (are inlined into FRAME).  */
 417   for (next_frame = get_next_frame (this_frame);
 418        next_frame && get_frame_type (next_frame) == INLINE_FRAME;
 419        next_frame = get_next_frame (next_frame))
 420     inline_count++;
 421
 422   /* Simulate some most-inner inlined frames which were suppressed, so
 423      they can be stepped into later.  If we are unwinding already
 424      outer frames from some non-inlined frame this does not apply.  */
 425   if (next_frame == NULL)
 426     inline_count += inline_skipped_frames (inferior_ptid);
 427
 428   return inline_count;
 429 }