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
  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; VEC_iterate (inline_state_s, inline_states, ix, state); ix++)
 130         if (pid != ptid_get_pid (state->ptid))
 131           VEC_safe_push (inline_state_s, new_states, state);
 132       VEC_free (inline_state_s, inline_states);
 133       inline_states = new_states;
 134       return;
 135     }
 136
 137   for (ix = 0; VEC_iterate (inline_state_s, inline_states, ix, state); ix++)
 138     if (ptid_equal (state->ptid, ptid))
 139       {
 140         VEC_unordered_remove (inline_state_s, inline_states, ix);
 141         return;
 142       }
 143 }
 144
 145 static void
 146 inline_frame_this_id (struct frame_info *this_frame,
 147                       void **this_cache,
 148                       struct frame_id *this_id)
 149 {
 150   struct symbol *func;
 151
 152   /* In order to have a stable frame ID for a given inline function,
 153      we must get the stack / special addresses from the underlying
 154      real frame's this_id method.  So we must call get_prev_frame.
 155      Because we are inlined into some function, there must be previous
 156      frames, so this is safe - as long as we're careful not to
 157      create any cycles.  */
 158   *this_id = get_frame_id (get_prev_frame (this_frame));
 159
 160   /* We need a valid frame ID, so we need to be based on a valid
 161      frame.  FSF submission NOTE: this would be a good assertion to
 162      apply to all frames, all the time.  That would fix the ambiguity
 163      of null_frame_id (between "no/any frame" and "the outermost
 164      frame").  This will take work.  */
 165   gdb_assert (frame_id_p (*this_id));
 166
 167   /* For now, require we don't match outer_frame_id either (see
 168      comment above).  */
 169   gdb_assert (!frame_id_eq (*this_id, outer_frame_id));
 170
 171   /* Future work NOTE: Alexandre Oliva applied a patch to GCC 4.3
 172      which generates DW_AT_entry_pc for inlined functions when
 173      possible.  If this attribute is available, we should use it
 174      in the frame ID (and eventually, to set breakpoints).  */
 175   func = get_frame_function (this_frame);
 176   gdb_assert (func != NULL);
 177   (*this_id).code_addr = BLOCK_START (SYMBOL_BLOCK_VALUE (func));
 178   (*this_id).inline_depth++;
 179 }
 180
 181 static struct value *
 182 inline_frame_prev_register (struct frame_info *this_frame, void **this_cache,
 183                             int regnum)
 184 {
 185   /* Use get_frame_register_value instead of
 186      frame_unwind_got_register, to avoid requiring this frame's ID.
 187      This frame's ID depends on the previous frame's ID (unusual), and
 188      the previous frame's ID depends on this frame's unwound
 189      registers.  If unwinding registers from this frame called
 190      get_frame_id, there would be a loop.
 191
 192      Do not copy this code into any other unwinder!  Inlined functions
 193      are special; other unwinders must not have a dependency on the
 194      previous frame's ID, and therefore can and should use
 195      frame_unwind_got_register instead.  */
 196   return get_frame_register_value (this_frame, regnum);
 197 }
 198
 199 /* Check whether we are at an inlining site that does not already
 200    have an associated frame.  */
 201
 202 static int
 203 inline_frame_sniffer (const struct frame_unwind *self,
 204                       struct frame_info *this_frame,
 205                       void **this_cache)
 206 {
 207   CORE_ADDR this_pc;
 208   struct block *frame_block, *cur_block;
 209   int depth;
 210   struct frame_info *next_frame;
 211   struct inline_state *state = find_inline_frame_state (inferior_ptid);
 212
 213   this_pc = get_frame_address_in_block (this_frame);
 214   frame_block = block_for_pc (this_pc);
 215   if (frame_block == NULL)
 216     return 0;
 217
 218   /* Calculate DEPTH, the number of inlined functions at this
 219      location.  */
 220   depth = 0;
 221   cur_block = frame_block;
 222   while (BLOCK_SUPERBLOCK (cur_block))
 223     {
 224       if (block_inlined_p (cur_block))
 225         depth++;
 226
 227       cur_block = BLOCK_SUPERBLOCK (cur_block);
 228     }
 229
 230   /* Check how many inlined functions already have frames.  */
 231   for (next_frame = get_next_frame (this_frame);
 232        next_frame && get_frame_type (next_frame) == INLINE_FRAME;
 233        next_frame = get_next_frame (next_frame))
 234     {
 235       gdb_assert (depth > 0);
 236       depth--;
 237     }
 238
 239   /* If this is the topmost frame, or all frames above us are inlined,
 240      then check whether we were requested to skip some frames (so they
 241      can be stepped into later).  */
 242   if (state != NULL && state->skipped_frames > 0 && next_frame == NULL)
 243     {
 244       gdb_assert (depth >= state->skipped_frames);
 245       depth -= state->skipped_frames;
 246     }
 247
 248   /* If all the inlined functions here already have frames, then pass
 249      to the normal unwinder for this PC.  */
 250   if (depth == 0)
 251     return 0;
 252
 253   /* If the next frame is an inlined function, but not the outermost, then
 254      we are the next outer.  If it is not an inlined function, then we
 255      are the innermost inlined function of a different real frame.  */
 256   return 1;
 257 }
 258
 259 const struct frame_unwind inline_frame_unwind = {
 260   INLINE_FRAME,
 261   inline_frame_this_id,
 262   inline_frame_prev_register,
 263   NULL,
 264   inline_frame_sniffer
 265 };
 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 }