gdb/inline-frame.c

   1 /* Inline frame unwinder for GDB.
   2
   3    Copyright (C) 2008, 2009, 2010 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 "addrmap.h"
  22 #include "block.h"
  23 #include "frame-unwind.h"
  24 #include "inferior.h"
  25 #include "regcache.h"
  26 #include "symtab.h"
  27 #include "vec.h"
  28
  29 #include "gdb_assert.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           if (current_pc != state->saved_pc)
  79             {
  80               /* PC has changed - this context is invalid.  Use the
  81                  default behavior.  */
  82               VEC_unordered_remove (inline_state_s, inline_states, ix);
  83               return NULL;
  84             }
  85           else
  86             return state;
  87         }
  88     }
  89
  90   return NULL;
  91 }
  92
  93 /* Allocate saved inlined frame state for PTID.  */
  94
  95 static struct inline_state *
  96 allocate_inline_frame_state (ptid_t ptid)
  97 {
  98   struct inline_state *state;
  99
 100   state = VEC_safe_push (inline_state_s, inline_states, NULL);
 101   memset (state, 0, sizeof (*state));
 102   state->ptid = ptid;
 103
 104   return state;
 105 }
 106
 107 /* Forget about any hidden inlined functions in PTID, which is new or
 108    about to be resumed.  PTID may be minus_one_ptid (all processes)
 109    or a PID (all threads in this process).  */
 110
 111 void
 112 clear_inline_frame_state (ptid_t ptid)
 113 {
 114   struct inline_state *state;
 115   int ix;
 116
 117   if (ptid_equal (ptid, minus_one_ptid))
 118     {
 119       VEC_free (inline_state_s, inline_states);
 120       return;
 121     }
 122
 123   if (ptid_is_pid (ptid))
 124     {
 125       VEC (inline_state_s) *new_states = NULL;
 126       int pid = ptid_get_pid (ptid);
 127       for (ix = 0; VEC_iterate (inline_state_s, inline_states, ix, state); ix++)
 128         if (pid != ptid_get_pid (state->ptid))
 129           VEC_safe_push (inline_state_s, new_states, state);
 130       VEC_free (inline_state_s, inline_states);
 131       inline_states = new_states;
 132       return;
 133     }
 134
 135   for (ix = 0; VEC_iterate (inline_state_s, inline_states, ix, state); ix++)
 136     if (ptid_equal (state->ptid, ptid))
 137       {
 138         VEC_unordered_remove (inline_state_s, inline_states, ix);
 139         return;
 140       }
 141 }
 142
 143 static void
 144 inline_frame_this_id (struct frame_info *this_frame,
 145                       void **this_cache,
 146                       struct frame_id *this_id)
 147 {
 148   struct symbol *func;
 149
 150   /* In order to have a stable frame ID for a given inline function,
 151      we must get the stack / special addresses from the underlying
 152      real frame's this_id method.  So we must call get_prev_frame.
 153      Because we are inlined into some function, there must be previous
 154      frames, so this is safe - as long as we're careful not to
 155      create any cycles.  */
 156   *this_id = get_frame_id (get_prev_frame (this_frame));
 157
 158   /* We need a valid frame ID, so we need to be based on a valid
 159      frame.  FSF submission NOTE: this would be a good assertion to
 160      apply to all frames, all the time.  That would fix the ambiguity
 161      of null_frame_id (between "no/any frame" and "the outermost
 162      frame").  This will take work.  */
 163   gdb_assert (frame_id_p (*this_id));
 164
 165   /* For now, require we don't match outer_frame_id either (see
 166      comment above).  */
 167   gdb_assert (!frame_id_eq (*this_id, outer_frame_id));
 168
 169   /* Future work NOTE: Alexandre Oliva applied a patch to GCC 4.3
 170      which generates DW_AT_entry_pc for inlined functions when
 171      possible.  If this attribute is available, we should use it
 172      in the frame ID (and eventually, to set breakpoints).  */
 173   func = get_frame_function (this_frame);
 174   gdb_assert (func != NULL);
 175   (*this_id).code_addr = BLOCK_START (SYMBOL_BLOCK_VALUE (func));
 176   (*this_id).inline_depth++;
 177 }
 178
 179 static struct value *
 180 inline_frame_prev_register (struct frame_info *this_frame, void **this_cache,
 181                             int regnum)
 182 {
 183   /* Use get_frame_register_value instead of
 184      frame_unwind_got_register, to avoid requiring this frame's ID.
 185      This frame's ID depends on the previous frame's ID (unusual), and
 186      the previous frame's ID depends on this frame's unwound
 187      registers.  If unwinding registers from this frame called
 188      get_frame_id, there would be a loop.
 189
 190      Do not copy this code into any other unwinder!  Inlined functions
 191      are special; other unwinders must not have a dependency on the
 192      previous frame's ID, and therefore can and should use
 193      frame_unwind_got_register instead.  */
 194   return get_frame_register_value (this_frame, regnum);
 195 }
 196
 197 /* Check whether we are at an inlining site that does not already
 198    have an associated frame.  */
 199
 200 static int
 201 inline_frame_sniffer (const struct frame_unwind *self,
 202                       struct frame_info *this_frame,
 203                       void **this_cache)
 204 {
 205   CORE_ADDR this_pc;
 206   struct block *frame_block, *cur_block;
 207   int depth;
 208   struct frame_info *next_frame;
 209   struct inline_state *state = find_inline_frame_state (inferior_ptid);
 210
 211   this_pc = get_frame_address_in_block (this_frame);
 212   frame_block = block_for_pc (this_pc);
 213   if (frame_block == NULL)
 214     return 0;
 215
 216   /* Calculate DEPTH, the number of inlined functions at this
 217      location.  */
 218   depth = 0;
 219   cur_block = frame_block;
 220   while (BLOCK_SUPERBLOCK (cur_block))
 221     {
 222       if (block_inlined_p (cur_block))
 223         depth++;
 224
 225       cur_block = BLOCK_SUPERBLOCK (cur_block);
 226     }
 227
 228   /* Check how many inlined functions already have frames.  */
 229   for (next_frame = get_next_frame (this_frame);
 230        next_frame && get_frame_type (next_frame) == INLINE_FRAME;
 231        next_frame = get_next_frame (next_frame))
 232     {
 233       gdb_assert (depth > 0);
 234       depth--;
 235     }
 236
 237   /* If this is the topmost frame, or all frames above us are inlined,
 238      then check whether we were requested to skip some frames (so they
 239      can be stepped into later).  */
 240   if (state != NULL && state->skipped_frames > 0 && next_frame == NULL)
 241     {
 242       gdb_assert (depth >= state->skipped_frames);
 243       depth -= state->skipped_frames;
 244     }
 245
 246   /* If all the inlined functions here already have frames, then pass
 247      to the normal unwinder for this PC.  */
 248   if (depth == 0)
 249     return 0;
 250
 251   /* If the next frame is an inlined function, but not the outermost, then
 252      we are the next outer.  If it is not an inlined function, then we
 253      are the innermost inlined function of a different real frame.  */
 254   return 1;
 255 }
 256
 257 const struct frame_unwind inline_frame_unwinder = {
 258   INLINE_FRAME,
 259   inline_frame_this_id,
 260   inline_frame_prev_register,
 261   NULL,
 262   inline_frame_sniffer
 263 };
 264
 265 const struct frame_unwind *const inline_frame_unwind = &inline_frame_unwinder;
 266
 267 /* Return non-zero if BLOCK, an inlined function block containing PC,
 268    has a group of contiguous instructions starting at PC (but not
 269    before it).  */
 270
 271 static int
 272 block_starting_point_at (CORE_ADDR pc, struct block *block)
 273 {
 274   struct blockvector *bv;
 275   struct block *new_block;
 276
 277   bv = blockvector_for_pc (pc, NULL);
 278   if (BLOCKVECTOR_MAP (bv) == NULL)
 279     return 0;
 280
 281   new_block = addrmap_find (BLOCKVECTOR_MAP (bv), pc - 1);
 282   if (new_block == NULL)
 283     return 1;
 284
 285   if (new_block == block || contained_in (new_block, block))
 286     return 0;
 287
 288   /* The immediately preceeding address belongs to a different block,
 289      which is not a child of this one.  Treat this as an entrance into
 290      BLOCK.  */
 291   return 1;
 292 }
 293
 294 /* Skip all inlined functions whose call sites are at the current PC.
 295    Frames for the hidden functions will not appear in the backtrace until the
 296    user steps into them.  */
 297
 298 void
 299 skip_inline_frames (ptid_t ptid)
 300 {
 301   CORE_ADDR this_pc;
 302   struct block *frame_block, *cur_block;
 303   struct symbol *last_sym = NULL;
 304   int skip_count = 0;
 305   struct inline_state *state;
 306
 307   /* This function is called right after reinitializing the frame
 308      cache.  We try not to do more unwinding than absolutely
 309      necessary, for performance.  */
 310   this_pc = get_frame_pc (get_current_frame ());
 311   frame_block = block_for_pc (this_pc);
 312
 313   if (frame_block != NULL)
 314     {
 315       cur_block = frame_block;
 316       while (BLOCK_SUPERBLOCK (cur_block))
 317         {
 318           if (block_inlined_p (cur_block))
 319             {
 320               /* See comments in inline_frame_this_id about this use
 321                  of BLOCK_START.  */
 322               if (BLOCK_START (cur_block) == this_pc
 323                   || block_starting_point_at (this_pc, cur_block))
 324                 {
 325                   skip_count++;
 326                   last_sym = BLOCK_FUNCTION (cur_block);
 327                 }
 328               else
 329                 break;
 330             }
 331           cur_block = BLOCK_SUPERBLOCK (cur_block);
 332         }
 333     }
 334
 335   gdb_assert (find_inline_frame_state (ptid) == NULL);
 336   state = allocate_inline_frame_state (ptid);
 337   state->skipped_frames = skip_count;
 338   state->saved_pc = this_pc;
 339   state->skipped_symbol = last_sym;
 340
 341   if (skip_count != 0)
 342     reinit_frame_cache ();
 343 }
 344
 345 /* Step into an inlined function by unhiding it.  */
 346
 347 void
 348 step_into_inline_frame (ptid_t ptid)
 349 {
 350   struct inline_state *state = find_inline_frame_state (ptid);
 351
 352   gdb_assert (state != NULL && state->skipped_frames > 0);
 353   state->skipped_frames--;
 354   reinit_frame_cache ();
 355 }
 356
 357 /* Return the number of hidden functions inlined into the current
 358    frame.  */
 359
 360 int
 361 inline_skipped_frames (ptid_t ptid)
 362 {
 363   struct inline_state *state = find_inline_frame_state (ptid);
 364
 365   if (state == NULL)
 366     return 0;
 367   else
 368     return state->skipped_frames;
 369 }
 370
 371 /* If one or more inlined functions are hidden, return the symbol for
 372    the function inlined into the current frame.  */
 373
 374 struct symbol *
 375 inline_skipped_symbol (ptid_t ptid)
 376 {
 377   struct inline_state *state = find_inline_frame_state (ptid);
 378
 379   gdb_assert (state != NULL);
 380   return state->skipped_symbol;
 381 }
 382
 383 /* Return the number of functions inlined into THIS_FRAME.  Some of
 384    the callees may not have associated frames (see
 385    skip_inline_frames).  */
 386
 387 int
 388 frame_inlined_callees (struct frame_info *this_frame)
 389 {
 390   struct frame_info *next_frame;
 391   int inline_count = 0;
 392
 393   /* First count how many inlined functions at this PC have frames
 394      above FRAME (are inlined into FRAME).  */
 395   for (next_frame = get_next_frame (this_frame);
 396        next_frame && get_frame_type (next_frame) == INLINE_FRAME;
 397        next_frame = get_next_frame (next_frame))
 398     inline_count++;
 399
 400   /* Simulate some most-inner inlined frames which were suppressed, so
 401      they can be stepped into later.  If we are unwinding already
 402      outer frames from some non-inlined frame this does not apply.  */
 403   if (next_frame == NULL)
 404     inline_count += inline_skipped_frames (inferior_ptid);
 405
 406   return inline_count;
 407 }