gdb/inline-frame.c

   1 /* Inline frame unwinder for GDB.
   2
   3    Copyright (C) 2008-2015 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 "inline-frame.h"
  22 #include "addrmap.h"
  23 #include "block.h"
  24 #include "frame-unwind.h"
  25 #include "inferior.h"
  26 #include "regcache.h"
  27 #include "symtab.h"
  28 #include "vec.h"
  29 #include "frame.h"
  30
  31 /* We need to save a few variables for every thread stopped at the
  32    virtual call site of an inlined function.  If there was always a
  33    "struct thread_info", we could hang it off that; in the mean time,
  34    keep our own list.  */
  35 struct inline_state
  36 {
  37   /* The thread this data relates to.  It should be a currently
  38      stopped thread; we assume thread IDs never change while the
  39      thread is stopped.  */
  40   ptid_t ptid;
  41
  42   /* The number of inlined functions we are skipping.  Each of these
  43      functions can be stepped in to.  */
  44   int skipped_frames;
  45
  46   /* Only valid if SKIPPED_FRAMES is non-zero.  This is the PC used
  47      when calculating SKIPPED_FRAMES; used to check whether we have
  48      moved to a new location by user request.  If so, we invalidate
  49      any skipped frames.  */
  50   CORE_ADDR saved_pc;
  51
  52   /* Only valid if SKIPPED_FRAMES is non-zero.  This is the symbol
  53      of the outermost skipped inline function.  It's used to find the
  54      call site of the current frame.  */
  55   struct symbol *skipped_symbol;
  56 };
  57
  58 typedef struct inline_state inline_state_s;
  59 DEF_VEC_O(inline_state_s);
  60
  61 static VEC(inline_state_s) *inline_states;
  62
  63 /* Locate saved inlined frame state for PTID, if it exists
  64    and is valid.  */
  65
  66 static struct inline_state *
  67 find_inline_frame_state (ptid_t ptid)
  68 {
  69   struct inline_state *state;
  70   int ix;
  71
  72   for (ix = 0; VEC_iterate (inline_state_s, inline_states, ix, state); ix++)
  73     {
  74       if (ptid_equal (state->ptid, ptid))
  75         {
  76           struct regcache *regcache = get_thread_regcache (ptid);
  77           CORE_ADDR current_pc = regcache_read_pc (regcache);
  78
  79           if (current_pc != state->saved_pc)
  80             {
  81               /* PC has changed - this context is invalid.  Use the
  82                  default behavior.  */
  83               VEC_unordered_remove (inline_state_s, inline_states, ix);
  84               return NULL;
  85             }
  86           else
  87             return state;
  88         }
  89     }
  90
  91   return NULL;
  92 }
  93
  94 /* Allocate saved inlined frame state for PTID.  */
  95
  96 static struct inline_state *
  97 allocate_inline_frame_state (ptid_t ptid)
  98 {
  99   struct inline_state *state;
 100
 101   state = VEC_safe_push (inline_state_s, inline_states, NULL);
 102   memset (state, 0, sizeof (*state));
 103   state->ptid = ptid;
 104
 105   return state;
 106 }
 107
 108 /* Forget about any hidden inlined functions in PTID, which is new or
 109    about to be resumed.  PTID may be minus_one_ptid (all processes)
 110    or a PID (all threads in this process).  */
 111
 112 void
 113 clear_inline_frame_state (ptid_t ptid)
 114 {
 115   struct inline_state *state;
 116   int ix;
 117
 118   if (ptid_equal (ptid, minus_one_ptid))
 119     {
 120       VEC_free (inline_state_s, inline_states);
 121       return;
 122     }
 123
 124   if (ptid_is_pid (ptid))
 125     {
 126       VEC (inline_state_s) *new_states = NULL;
 127       int pid = ptid_get_pid (ptid);
 128
 129       for (ix = 0;
 130            VEC_iterate (inline_state_s, inline_states, ix, state);
 131            ix++)
 132         if (pid != ptid_get_pid (state->ptid))
 133           VEC_safe_push (inline_state_s, new_states, state);
 134       VEC_free (inline_state_s, inline_states);
 135       inline_states = new_states;
 136       return;
 137     }
 138
 139   for (ix = 0; VEC_iterate (inline_state_s, inline_states, ix, state); ix++)
 140     if (ptid_equal (state->ptid, ptid))
 141       {
 142         VEC_unordered_remove (inline_state_s, inline_states, ix);
 143         return;
 144       }
 145 }
 146
 147 static void
 148 inline_frame_this_id (struct frame_info *this_frame,
 149                       void **this_cache,
 150                       struct frame_id *this_id)
 151 {
 152   struct symbol *func;
 153
 154   /* In order to have a stable frame ID for a given inline function,
 155      we must get the stack / special addresses from the underlying
 156      real frame's this_id method.  So we must call
 157      get_prev_frame_always.  Because we are inlined into some
 158      function, there must be previous frames, so this is safe - as
 159      long as we're careful not to create any cycles.  */
 160   *this_id = get_frame_id (get_prev_frame_always (this_frame));
 161
 162   /* We need a valid frame ID, so we need to be based on a valid
 163      frame.  FSF submission NOTE: this would be a good assertion to
 164      apply to all frames, all the time.  That would fix the ambiguity
 165      of null_frame_id (between "no/any frame" and "the outermost
 166      frame").  This will take work.  */
 167   gdb_assert (frame_id_p (*this_id));
 168
 169   /* For now, require we don't match outer_frame_id either (see
 170      comment above).  */
 171   gdb_assert (!frame_id_eq (*this_id, outer_frame_id));
 172
 173   /* Future work NOTE: Alexandre Oliva applied a patch to GCC 4.3
 174      which generates DW_AT_entry_pc for inlined functions when
 175      possible.  If this attribute is available, we should use it
 176      in the frame ID (and eventually, to set breakpoints).  */
 177   func = get_frame_function (this_frame);
 178   gdb_assert (func != NULL);
 179   (*this_id).code_addr = BLOCK_START (SYMBOL_BLOCK_VALUE (func));
 180   (*this_id).artificial_depth++;
 181 }
 182
 183 static struct value *
 184 inline_frame_prev_register (struct frame_info *this_frame, void **this_cache,
 185                             int regnum)
 186 {
 187   /* Use get_frame_register_value instead of
 188      frame_unwind_got_register, to avoid requiring this frame's ID.
 189      This frame's ID depends on the previous frame's ID (unusual), and
 190      the previous frame's ID depends on this frame's unwound
 191      registers.  If unwinding registers from this frame called
 192      get_frame_id, there would be a loop.
 193
 194      Do not copy this code into any other unwinder!  Inlined functions
 195      are special; other unwinders must not have a dependency on the
 196      previous frame's ID, and therefore can and should use
 197      frame_unwind_got_register instead.  */
 198   return get_frame_register_value (this_frame, regnum);
 199 }
 200
 201 /* Check whether we are at an inlining site that does not already
 202    have an associated frame.  */
 203
 204 static int
 205 inline_frame_sniffer (const struct frame_unwind *self,
 206                       struct frame_info *this_frame,
 207                       void **this_cache)
 208 {
 209   CORE_ADDR this_pc;
 210   const struct block *frame_block, *cur_block;
 211   int depth;
 212   struct frame_info *next_frame;
 213   struct inline_state *state = find_inline_frame_state (inferior_ptid);
 214
 215   this_pc = get_frame_address_in_block (this_frame);
 216   frame_block = block_for_pc (this_pc);
 217   if (frame_block == NULL)
 218     return 0;
 219
 220   /* Calculate DEPTH, the number of inlined functions at this
 221      location.  */
 222   depth = 0;
 223   cur_block = frame_block;
 224   while (BLOCK_SUPERBLOCK (cur_block))
 225     {
 226       if (block_inlined_p (cur_block))
 227         depth++;
 228
 229       cur_block = BLOCK_SUPERBLOCK (cur_block);
 230     }
 231
 232   /* Check how many inlined functions already have frames.  */
 233   for (next_frame = get_next_frame (this_frame);
 234        next_frame && get_frame_type (next_frame) == INLINE_FRAME;
 235        next_frame = get_next_frame (next_frame))
 236     {
 237       gdb_assert (depth > 0);
 238       depth--;
 239     }
 240
 241   /* If this is the topmost frame, or all frames above us are inlined,
 242      then check whether we were requested to skip some frames (so they
 243      can be stepped into later).  */
 244   if (state != NULL && state->skipped_frames > 0 && next_frame == NULL)
 245     {
 246       gdb_assert (depth >= state->skipped_frames);
 247       depth -= state->skipped_frames;
 248     }
 249
 250   /* If all the inlined functions here already have frames, then pass
 251      to the normal unwinder for this PC.  */
 252   if (depth == 0)
 253     return 0;
 254
 255   /* If the next frame is an inlined function, but not the outermost, then
 256      we are the next outer.  If it is not an inlined function, then we
 257      are the innermost inlined function of a different real frame.  */
 258   return 1;
 259 }
 260
 261 const struct frame_unwind inline_frame_unwind = {
 262   INLINE_FRAME,
 263   default_frame_unwind_stop_reason,
 264   inline_frame_this_id,
 265   inline_frame_prev_register,
 266   NULL,
 267   inline_frame_sniffer
 268 };
 269
 270 /* Return non-zero if BLOCK, an inlined function block containing PC,
 271    has a group of contiguous instructions starting at PC (but not
 272    before it).  */
 273
 274 static int
 275 block_starting_point_at (CORE_ADDR pc, const struct block *block)
 276 {
 277   const struct blockvector *bv;
 278   struct block *new_block;
 279
 280   bv = blockvector_for_pc (pc, NULL);
 281   if (BLOCKVECTOR_MAP (bv) == NULL)
 282     return 0;
 283
 284   new_block = addrmap_find (BLOCKVECTOR_MAP (bv), pc - 1);
 285   if (new_block == NULL)
 286     return 1;
 287
 288   if (new_block == block || contained_in (new_block, block))
 289     return 0;
 290
 291   /* The immediately preceding address belongs to a different block,
 292      which is not a child of this one.  Treat this as an entrance into
 293      BLOCK.  */
 294   return 1;
 295 }
 296
 297 /* Skip all inlined functions whose call sites are at the current PC.
 298    Frames for the hidden functions will not appear in the backtrace until the
 299    user steps into them.  */
 300
 301 void
 302 skip_inline_frames (ptid_t ptid)
 303 {
 304   CORE_ADDR this_pc;
 305   const struct block *frame_block, *cur_block;
 306   struct symbol *last_sym = NULL;
 307   int skip_count = 0;
 308   struct inline_state *state;
 309
 310   /* This function is called right after reinitializing the frame
 311      cache.  We try not to do more unwinding than absolutely
 312      necessary, for performance.  */
 313   this_pc = get_frame_pc (get_current_frame ());
 314   frame_block = block_for_pc (this_pc);
 315
 316   if (frame_block != NULL)
 317     {
 318       cur_block = frame_block;
 319       while (BLOCK_SUPERBLOCK (cur_block))
 320         {
 321           if (block_inlined_p (cur_block))
 322             {
 323               /* See comments in inline_frame_this_id about this use
 324                  of BLOCK_START.  */
 325               if (BLOCK_START (cur_block) == this_pc
 326                   || block_starting_point_at (this_pc, cur_block))
 327                 {
 328                   skip_count++;
 329                   last_sym = BLOCK_FUNCTION (cur_block);
 330                 }
 331               else
 332                 break;
 333             }
 334           cur_block = BLOCK_SUPERBLOCK (cur_block);
 335         }
 336     }
 337
 338   gdb_assert (find_inline_frame_state (ptid) == NULL);
 339   state = allocate_inline_frame_state (ptid);
 340   state->skipped_frames = skip_count;
 341   state->saved_pc = this_pc;
 342   state->skipped_symbol = last_sym;
 343
 344   if (skip_count != 0)
 345     reinit_frame_cache ();
 346 }
 347
 348 /* Step into an inlined function by unhiding it.  */
 349
 350 void
 351 step_into_inline_frame (ptid_t ptid)
 352 {
 353   struct inline_state *state = find_inline_frame_state (ptid);
 354
 355   gdb_assert (state != NULL && state->skipped_frames > 0);
 356   state->skipped_frames--;
 357   reinit_frame_cache ();
 358 }
 359
 360 /* Return the number of hidden functions inlined into the current
 361    frame.  */
 362
 363 int
 364 inline_skipped_frames (ptid_t ptid)
 365 {
 366   struct inline_state *state = find_inline_frame_state (ptid);
 367
 368   if (state == NULL)
 369     return 0;
 370   else
 371     return state->skipped_frames;
 372 }
 373
 374 /* If one or more inlined functions are hidden, return the symbol for
 375    the function inlined into the current frame.  */
 376
 377 struct symbol *
 378 inline_skipped_symbol (ptid_t ptid)
 379 {
 380   struct inline_state *state = find_inline_frame_state (ptid);
 381
 382   gdb_assert (state != NULL);
 383   return state->skipped_symbol;
 384 }
 385
 386 /* Return the number of functions inlined into THIS_FRAME.  Some of
 387    the callees may not have associated frames (see
 388    skip_inline_frames).  */
 389
 390 int
 391 frame_inlined_callees (struct frame_info *this_frame)
 392 {
 393   struct frame_info *next_frame;
 394   int inline_count = 0;
 395
 396   /* First count how many inlined functions at this PC have frames
 397      above FRAME (are inlined into FRAME).  */
 398   for (next_frame = get_next_frame (this_frame);
 399        next_frame && get_frame_type (next_frame) == INLINE_FRAME;
 400        next_frame = get_next_frame (next_frame))
 401     inline_count++;
 402
 403   /* Simulate some most-inner inlined frames which were suppressed, so
 404      they can be stepped into later.  If we are unwinding already
 405      outer frames from some non-inlined frame this does not apply.  */
 406   if (next_frame == NULL)
 407     inline_count += inline_skipped_frames (inferior_ptid);
 408
 409   return inline_count;
 410 }