gdb/inline-frame.c

   1 /* Inline frame unwinder for GDB.
   2
   3    Copyright (C) 2008-2016 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       else if (BLOCK_FUNCTION (cur_block) != NULL)
 229         break;
 230
 231       cur_block = BLOCK_SUPERBLOCK (cur_block);
 232     }
 233
 234   /* Check how many inlined functions already have frames.  */
 235   for (next_frame = get_next_frame (this_frame);
 236        next_frame && get_frame_type (next_frame) == INLINE_FRAME;
 237        next_frame = get_next_frame (next_frame))
 238     {
 239       gdb_assert (depth > 0);
 240       depth--;
 241     }
 242
 243   /* If this is the topmost frame, or all frames above us are inlined,
 244      then check whether we were requested to skip some frames (so they
 245      can be stepped into later).  */
 246   if (state != NULL && state->skipped_frames > 0 && next_frame == NULL)
 247     {
 248       gdb_assert (depth >= state->skipped_frames);
 249       depth -= state->skipped_frames;
 250     }
 251
 252   /* If all the inlined functions here already have frames, then pass
 253      to the normal unwinder for this PC.  */
 254   if (depth == 0)
 255     return 0;
 256
 257   /* If the next frame is an inlined function, but not the outermost, then
 258      we are the next outer.  If it is not an inlined function, then we
 259      are the innermost inlined function of a different real frame.  */
 260   return 1;
 261 }
 262
 263 const struct frame_unwind inline_frame_unwind = {
 264   INLINE_FRAME,
 265   default_frame_unwind_stop_reason,
 266   inline_frame_this_id,
 267   inline_frame_prev_register,
 268   NULL,
 269   inline_frame_sniffer
 270 };
 271
 272 /* Return non-zero if BLOCK, an inlined function block containing PC,
 273    has a group of contiguous instructions starting at PC (but not
 274    before it).  */
 275
 276 static int
 277 block_starting_point_at (CORE_ADDR pc, const struct block *block)
 278 {
 279   const struct blockvector *bv;
 280   struct block *new_block;
 281
 282   bv = blockvector_for_pc (pc, NULL);
 283   if (BLOCKVECTOR_MAP (bv) == NULL)
 284     return 0;
 285
 286   new_block = (struct block *) addrmap_find (BLOCKVECTOR_MAP (bv), pc - 1);
 287   if (new_block == NULL)
 288     return 1;
 289
 290   if (new_block == block || contained_in (new_block, block))
 291     return 0;
 292
 293   /* The immediately preceding address belongs to a different block,
 294      which is not a child of this one.  Treat this as an entrance into
 295      BLOCK.  */
 296   return 1;
 297 }
 298
 299 /* Skip all inlined functions whose call sites are at the current PC.
 300    Frames for the hidden functions will not appear in the backtrace until the
 301    user steps into them.  */
 302
 303 void
 304 skip_inline_frames (ptid_t ptid)
 305 {
 306   CORE_ADDR this_pc;
 307   const struct block *frame_block, *cur_block;
 308   struct symbol *last_sym = NULL;
 309   int skip_count = 0;
 310   struct inline_state *state;
 311
 312   /* This function is called right after reinitializing the frame
 313      cache.  We try not to do more unwinding than absolutely
 314      necessary, for performance.  */
 315   this_pc = get_frame_pc (get_current_frame ());
 316   frame_block = block_for_pc (this_pc);
 317
 318   if (frame_block != NULL)
 319     {
 320       cur_block = frame_block;
 321       while (BLOCK_SUPERBLOCK (cur_block))
 322         {
 323           if (block_inlined_p (cur_block))
 324             {
 325               /* See comments in inline_frame_this_id about this use
 326                  of BLOCK_START.  */
 327               if (BLOCK_START (cur_block) == this_pc
 328                   || block_starting_point_at (this_pc, cur_block))
 329                 {
 330                   skip_count++;
 331                   last_sym = BLOCK_FUNCTION (cur_block);
 332                 }
 333               else
 334                 break;
 335             }
 336           else if (BLOCK_FUNCTION (cur_block) != NULL)
 337             break;
 338
 339           cur_block = BLOCK_SUPERBLOCK (cur_block);
 340         }
 341     }
 342
 343   gdb_assert (find_inline_frame_state (ptid) == NULL);
 344   state = allocate_inline_frame_state (ptid);
 345   state->skipped_frames = skip_count;
 346   state->saved_pc = this_pc;
 347   state->skipped_symbol = last_sym;
 348
 349   if (skip_count != 0)
 350     reinit_frame_cache ();
 351 }
 352
 353 /* Step into an inlined function by unhiding it.  */
 354
 355 void
 356 step_into_inline_frame (ptid_t ptid)
 357 {
 358   struct inline_state *state = find_inline_frame_state (ptid);
 359
 360   gdb_assert (state != NULL && state->skipped_frames > 0);
 361   state->skipped_frames--;
 362   reinit_frame_cache ();
 363 }
 364
 365 /* Return the number of hidden functions inlined into the current
 366    frame.  */
 367
 368 int
 369 inline_skipped_frames (ptid_t ptid)
 370 {
 371   struct inline_state *state = find_inline_frame_state (ptid);
 372
 373   if (state == NULL)
 374     return 0;
 375   else
 376     return state->skipped_frames;
 377 }
 378
 379 /* If one or more inlined functions are hidden, return the symbol for
 380    the function inlined into the current frame.  */
 381
 382 struct symbol *
 383 inline_skipped_symbol (ptid_t ptid)
 384 {
 385   struct inline_state *state = find_inline_frame_state (ptid);
 386
 387   gdb_assert (state != NULL);
 388   return state->skipped_symbol;
 389 }
 390
 391 /* Return the number of functions inlined into THIS_FRAME.  Some of
 392    the callees may not have associated frames (see
 393    skip_inline_frames).  */
 394
 395 int
 396 frame_inlined_callees (struct frame_info *this_frame)
 397 {
 398   struct frame_info *next_frame;
 399   int inline_count = 0;
 400
 401   /* First count how many inlined functions at this PC have frames
 402      above FRAME (are inlined into FRAME).  */
 403   for (next_frame = get_next_frame (this_frame);
 404        next_frame && get_frame_type (next_frame) == INLINE_FRAME;
 405        next_frame = get_next_frame (next_frame))
 406     inline_count++;
 407
 408   /* Simulate some most-inner inlined frames which were suppressed, so
 409      they can be stepped into later.  If we are unwinding already
 410      outer frames from some non-inlined frame this does not apply.  */
 411   if (next_frame == NULL)
 412     inline_count += inline_skipped_frames (inferior_ptid);
 413
 414   return inline_count;
 415 }