1 /* Virtual tail call frames unwinder for GDB.
3 Copyright (C) 2010-2014 Free Software Foundation, Inc.
5 This file is part of GDB.
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.
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.
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/>. */
22 #include "dwarf2-frame-tailcall.h"
23 #include "dwarf2loc.h"
24 #include "frame-unwind.h"
27 #include "exceptions.h"
31 #include "dwarf2-frame.h"
33 /* Contains struct tailcall_cache indexed by next_bottom_frame. */
34 static htab_t cache_htab
;
36 /* Associate structure of the unwinder to call_site_chain. Lifetime of this
37 structure is maintained by REFC decremented by dealloc_cache, all of them
38 get deleted during reinit_frame_cache. */
41 /* It must be the first one of this struct. It is the furthest callee. */
42 struct frame_info
*next_bottom_frame
;
44 /* Reference count. The whole chain of virtual tail call frames shares one
48 /* Associated found virtual taill call frames chain, it is never NULL. */
49 struct call_site_chain
*chain
;
51 /* Cached pretended_chain_levels result. */
54 /* Unwound PC from the top (caller) frame, as it is not contained
58 /* Compensate SP in caller frames appropriately. prev_sp and
59 entry_cfa_sp_offset are valid only if PREV_SP_P. PREV_SP is SP at the top
60 (caller) frame. ENTRY_CFA_SP_OFFSET is shift of SP in tail call frames
61 against next_bottom_frame SP. */
62 unsigned prev_sp_p
: 1;
64 LONGEST entry_cfa_sp_offset
;
67 /* hash_f for htab_create_alloc of cache_htab. */
70 cache_hash (const void *arg
)
72 const struct tailcall_cache
*cache
= arg
;
74 return htab_hash_pointer (cache
->next_bottom_frame
);
77 /* eq_f for htab_create_alloc of cache_htab. */
80 cache_eq (const void *arg1
, const void *arg2
)
82 const struct tailcall_cache
*cache1
= arg1
;
83 const struct tailcall_cache
*cache2
= arg2
;
85 return cache1
->next_bottom_frame
== cache2
->next_bottom_frame
;
88 /* Create new tailcall_cache for NEXT_BOTTOM_FRAME, NEXT_BOTTOM_FRAME must not
89 yet have been indexed by cache_htab. Caller holds one reference of the new
92 static struct tailcall_cache
*
93 cache_new_ref1 (struct frame_info
*next_bottom_frame
)
95 struct tailcall_cache
*cache
;
98 cache
= xzalloc (sizeof (*cache
));
100 cache
->next_bottom_frame
= next_bottom_frame
;
103 slot
= htab_find_slot (cache_htab
, cache
, INSERT
);
104 gdb_assert (*slot
== NULL
);
110 /* Create new reference to CACHE. */
113 cache_ref (struct tailcall_cache
*cache
)
115 gdb_assert (cache
->refc
> 0);
120 /* Drop reference to CACHE, possibly fully freeing it and unregistering it from
124 cache_unref (struct tailcall_cache
*cache
)
126 gdb_assert (cache
->refc
> 0);
130 gdb_assert (htab_find_slot (cache_htab
, cache
, NO_INSERT
) != NULL
);
131 htab_remove_elt (cache_htab
, cache
);
133 xfree (cache
->chain
);
138 /* Return 1 if FI is a non-bottom (not the callee) tail call frame. Otherwise
142 frame_is_tailcall (struct frame_info
*fi
)
144 return frame_unwinder_is (fi
, &dwarf2_tailcall_frame_unwind
);
147 /* Try to find tailcall_cache in cache_htab if FI is a part of its virtual tail
148 call chain. Otherwise return NULL. No new reference is created. */
150 static struct tailcall_cache
*
151 cache_find (struct frame_info
*fi
)
153 struct tailcall_cache
*cache
;
156 while (frame_is_tailcall (fi
))
158 fi
= get_next_frame (fi
);
159 gdb_assert (fi
!= NULL
);
162 slot
= htab_find_slot (cache_htab
, &fi
, NO_INSERT
);
167 gdb_assert (cache
!= NULL
);
171 /* Number of virtual frames between THIS_FRAME and CACHE->NEXT_BOTTOM_FRAME.
172 If THIS_FRAME is CACHE-> NEXT_BOTTOM_FRAME return -1. */
175 existing_next_levels (struct frame_info
*this_frame
,
176 struct tailcall_cache
*cache
)
178 int retval
= (frame_relative_level (this_frame
)
179 - frame_relative_level (cache
->next_bottom_frame
) - 1);
181 gdb_assert (retval
>= -1);
186 /* The number of virtual tail call frames in CHAIN. With no virtual tail call
187 frames the function would return 0 (but CHAIN does not exist in such
191 pretended_chain_levels (struct call_site_chain
*chain
)
195 gdb_assert (chain
!= NULL
);
197 if (chain
->callers
== chain
->length
&& chain
->callees
== chain
->length
)
198 return chain
->length
;
200 chain_levels
= chain
->callers
+ chain
->callees
;
201 gdb_assert (chain_levels
< chain
->length
);
206 /* Implementation of frame_this_id_ftype. THIS_CACHE must be already
207 initialized with tailcall_cache, THIS_FRAME must be a part of THIS_CACHE.
209 Specific virtual tail call frames are tracked by INLINE_DEPTH. */
212 tailcall_frame_this_id (struct frame_info
*this_frame
, void **this_cache
,
213 struct frame_id
*this_id
)
215 struct tailcall_cache
*cache
= *this_cache
;
216 struct frame_info
*next_frame
;
218 /* Tail call does not make sense for a sentinel frame. */
219 next_frame
= get_next_frame (this_frame
);
220 gdb_assert (next_frame
!= NULL
);
222 *this_id
= get_frame_id (next_frame
);
223 (*this_id
).code_addr
= get_frame_pc (this_frame
);
224 (*this_id
).code_addr_p
= 1;
225 (*this_id
).artificial_depth
= (cache
->chain_levels
226 - existing_next_levels (this_frame
, cache
));
227 gdb_assert ((*this_id
).artificial_depth
> 0);
230 /* Find PC to be unwound from THIS_FRAME. THIS_FRAME must be a part of
234 pretend_pc (struct frame_info
*this_frame
, struct tailcall_cache
*cache
)
236 int next_levels
= existing_next_levels (this_frame
, cache
);
237 struct call_site_chain
*chain
= cache
->chain
;
239 gdb_assert (chain
!= NULL
);
242 gdb_assert (next_levels
>= 0);
244 if (next_levels
< chain
->callees
)
245 return chain
->call_site
[chain
->length
- next_levels
- 1]->pc
;
246 next_levels
-= chain
->callees
;
248 /* Otherwise CHAIN->CALLEES are already covered by CHAIN->CALLERS. */
249 if (chain
->callees
!= chain
->length
)
251 if (next_levels
< chain
->callers
)
252 return chain
->call_site
[chain
->callers
- next_levels
- 1]->pc
;
253 next_levels
-= chain
->callers
;
256 gdb_assert (next_levels
== 0);
257 return cache
->prev_pc
;
260 /* Implementation of frame_prev_register_ftype. If no specific register
261 override is supplied NULL is returned (this is incompatible with
262 frame_prev_register_ftype semantics). next_bottom_frame and tail call
263 frames unwind the NULL case differently. */
266 dwarf2_tailcall_prev_register_first (struct frame_info
*this_frame
,
267 void **tailcall_cachep
, int regnum
)
269 struct gdbarch
*this_gdbarch
= get_frame_arch (this_frame
);
270 struct tailcall_cache
*cache
= *tailcall_cachep
;
273 if (regnum
== gdbarch_pc_regnum (this_gdbarch
))
274 addr
= pretend_pc (this_frame
, cache
);
275 else if (cache
->prev_sp_p
&& regnum
== gdbarch_sp_regnum (this_gdbarch
))
277 int next_levels
= existing_next_levels (this_frame
, cache
);
279 if (next_levels
== cache
->chain_levels
- 1)
280 addr
= cache
->prev_sp
;
282 addr
= dwarf2_frame_cfa (this_frame
) - cache
->entry_cfa_sp_offset
;
287 return frame_unwind_got_address (this_frame
, regnum
, addr
);
290 /* Implementation of frame_prev_register_ftype for tail call frames. Register
291 set of virtual tail call frames is assumed to be the one of the top (caller)
292 frame - assume unchanged register value for NULL from
293 dwarf2_tailcall_prev_register_first. */
295 static struct value
*
296 tailcall_frame_prev_register (struct frame_info
*this_frame
,
297 void **this_cache
, int regnum
)
299 struct tailcall_cache
*cache
= *this_cache
;
302 gdb_assert (this_frame
!= cache
->next_bottom_frame
);
304 val
= dwarf2_tailcall_prev_register_first (this_frame
, this_cache
, regnum
);
308 return frame_unwind_got_register (this_frame
, regnum
, regnum
);
311 /* Implementation of frame_sniffer_ftype. It will never find a new chain, use
312 dwarf2_tailcall_sniffer_first for the bottom (callee) frame. It will find
313 all the predecessing virtual tail call frames, it will return false when
314 there exist no more tail call frames in this chain. */
317 tailcall_frame_sniffer (const struct frame_unwind
*self
,
318 struct frame_info
*this_frame
, void **this_cache
)
320 struct frame_info
*next_frame
;
322 struct tailcall_cache
*cache
;
324 /* Inner tail call element does not make sense for a sentinel frame. */
325 next_frame
= get_next_frame (this_frame
);
326 if (next_frame
== NULL
)
329 cache
= cache_find (next_frame
);
335 next_levels
= existing_next_levels (this_frame
, cache
);
337 /* NEXT_LEVELS is -1 only in dwarf2_tailcall_sniffer_first. */
338 gdb_assert (next_levels
>= 0);
339 gdb_assert (next_levels
<= cache
->chain_levels
);
341 if (next_levels
== cache
->chain_levels
)
351 /* The initial "sniffer" whether THIS_FRAME is a bottom (callee) frame of a new
352 chain to create. Keep TAILCALL_CACHEP NULL if it did not find any chain,
353 initialize it otherwise. No tail call chain is created if there are no
354 unambiguous virtual tail call frames to report.
356 ENTRY_CFA_SP_OFFSETP is NULL if no special SP handling is possible,
357 otherwise *ENTRY_CFA_SP_OFFSETP is the number of bytes to subtract from tail
358 call frames frame base to get the SP value there - to simulate return
359 address pushed on the stack. */
362 dwarf2_tailcall_sniffer_first (struct frame_info
*this_frame
,
363 void **tailcall_cachep
,
364 const LONGEST
*entry_cfa_sp_offsetp
)
366 CORE_ADDR prev_pc
= 0, prev_sp
= 0; /* GCC warning. */
369 struct gdbarch
*prev_gdbarch
;
370 struct call_site_chain
*chain
= NULL
;
371 struct tailcall_cache
*cache
;
372 volatile struct gdb_exception except
;
374 gdb_assert (*tailcall_cachep
== NULL
);
376 /* PC may be after the function if THIS_FRAME calls noreturn function,
377 get_frame_address_in_block will decrease it by 1 in such case. */
378 this_pc
= get_frame_address_in_block (this_frame
);
380 /* Catch any unwinding errors. */
381 TRY_CATCH (except
, RETURN_MASK_ERROR
)
385 prev_gdbarch
= frame_unwind_arch (this_frame
);
387 /* Simulate frame_unwind_pc without setting this_frame->prev_pc.p. */
388 prev_pc
= gdbarch_unwind_pc (prev_gdbarch
, this_frame
);
390 /* call_site_find_chain can throw an exception. */
391 chain
= call_site_find_chain (prev_gdbarch
, prev_pc
, this_pc
);
393 if (entry_cfa_sp_offsetp
== NULL
)
395 sp_regnum
= gdbarch_sp_regnum (prev_gdbarch
);
398 prev_sp
= frame_unwind_register_unsigned (this_frame
, sp_regnum
);
401 if (except
.reason
< 0)
403 if (entry_values_debug
)
404 exception_print (gdb_stdout
, except
);
408 /* Ambiguous unwind or unambiguous unwind verified as matching. */
409 if (chain
== NULL
|| chain
->length
== 0)
415 cache
= cache_new_ref1 (this_frame
);
416 *tailcall_cachep
= cache
;
417 cache
->chain
= chain
;
418 cache
->prev_pc
= prev_pc
;
419 cache
->chain_levels
= pretended_chain_levels (chain
);
420 cache
->prev_sp_p
= prev_sp_p
;
421 if (cache
->prev_sp_p
)
423 cache
->prev_sp
= prev_sp
;
424 cache
->entry_cfa_sp_offset
= *entry_cfa_sp_offsetp
;
426 gdb_assert (cache
->chain_levels
> 0);
429 /* Implementation of frame_dealloc_cache_ftype. It can be called even for the
430 bottom chain frame from dwarf2_frame_dealloc_cache which is not a real
434 tailcall_frame_dealloc_cache (struct frame_info
*self
, void *this_cache
)
436 struct tailcall_cache
*cache
= this_cache
;
441 /* Implementation of frame_prev_arch_ftype. We assume all the virtual tail
442 call frames have gdbarch of the bottom (callee) frame. */
444 static struct gdbarch
*
445 tailcall_frame_prev_arch (struct frame_info
*this_frame
,
446 void **this_prologue_cache
)
448 struct tailcall_cache
*cache
= *this_prologue_cache
;
450 return get_frame_arch (cache
->next_bottom_frame
);
453 /* Virtual tail call frame unwinder if dwarf2_tailcall_sniffer_first finds
454 a chain to create. */
456 const struct frame_unwind dwarf2_tailcall_frame_unwind
=
459 default_frame_unwind_stop_reason
,
460 tailcall_frame_this_id
,
461 tailcall_frame_prev_register
,
463 tailcall_frame_sniffer
,
464 tailcall_frame_dealloc_cache
,
465 tailcall_frame_prev_arch
468 /* Provide a prototype to silence -Wmissing-prototypes. */
469 extern initialize_file_ftype _initialize_tailcall_frame
;
472 _initialize_tailcall_frame (void)
474 cache_htab
= htab_create_alloc (50, cache_hash
, cache_eq
, NULL
, xcalloc
,