| 1 | /* Virtual tail call frames unwinder for GDB. |
| 2 | |
| 3 | Copyright (C) 2010-2017 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 "frame.h" |
| 22 | #include "dwarf2-frame-tailcall.h" |
| 23 | #include "dwarf2loc.h" |
| 24 | #include "frame-unwind.h" |
| 25 | #include "block.h" |
| 26 | #include "hashtab.h" |
| 27 | #include "gdbtypes.h" |
| 28 | #include "regcache.h" |
| 29 | #include "value.h" |
| 30 | #include "dwarf2-frame.h" |
| 31 | |
| 32 | /* Contains struct tailcall_cache indexed by next_bottom_frame. */ |
| 33 | static htab_t cache_htab; |
| 34 | |
| 35 | /* Associate structure of the unwinder to call_site_chain. Lifetime of this |
| 36 | structure is maintained by REFC decremented by dealloc_cache, all of them |
| 37 | get deleted during reinit_frame_cache. */ |
| 38 | struct tailcall_cache |
| 39 | { |
| 40 | /* It must be the first one of this struct. It is the furthest callee. */ |
| 41 | struct frame_info *next_bottom_frame; |
| 42 | |
| 43 | /* Reference count. The whole chain of virtual tail call frames shares one |
| 44 | tailcall_cache. */ |
| 45 | int refc; |
| 46 | |
| 47 | /* Associated found virtual taill call frames chain, it is never NULL. */ |
| 48 | struct call_site_chain *chain; |
| 49 | |
| 50 | /* Cached pretended_chain_levels result. */ |
| 51 | int chain_levels; |
| 52 | |
| 53 | /* Unwound PC from the top (caller) frame, as it is not contained |
| 54 | in CHAIN. */ |
| 55 | CORE_ADDR prev_pc; |
| 56 | |
| 57 | /* Compensate SP in caller frames appropriately. prev_sp and |
| 58 | entry_cfa_sp_offset are valid only if PREV_SP_P. PREV_SP is SP at the top |
| 59 | (caller) frame. ENTRY_CFA_SP_OFFSET is shift of SP in tail call frames |
| 60 | against next_bottom_frame SP. */ |
| 61 | unsigned prev_sp_p : 1; |
| 62 | CORE_ADDR prev_sp; |
| 63 | LONGEST entry_cfa_sp_offset; |
| 64 | }; |
| 65 | |
| 66 | /* hash_f for htab_create_alloc of cache_htab. */ |
| 67 | |
| 68 | static hashval_t |
| 69 | cache_hash (const void *arg) |
| 70 | { |
| 71 | const struct tailcall_cache *cache = (const struct tailcall_cache *) arg; |
| 72 | |
| 73 | return htab_hash_pointer (cache->next_bottom_frame); |
| 74 | } |
| 75 | |
| 76 | /* eq_f for htab_create_alloc of cache_htab. */ |
| 77 | |
| 78 | static int |
| 79 | cache_eq (const void *arg1, const void *arg2) |
| 80 | { |
| 81 | const struct tailcall_cache *cache1 = (const struct tailcall_cache *) arg1; |
| 82 | const struct tailcall_cache *cache2 = (const struct tailcall_cache *) arg2; |
| 83 | |
| 84 | return cache1->next_bottom_frame == cache2->next_bottom_frame; |
| 85 | } |
| 86 | |
| 87 | /* Create new tailcall_cache for NEXT_BOTTOM_FRAME, NEXT_BOTTOM_FRAME must not |
| 88 | yet have been indexed by cache_htab. Caller holds one reference of the new |
| 89 | tailcall_cache. */ |
| 90 | |
| 91 | static struct tailcall_cache * |
| 92 | cache_new_ref1 (struct frame_info *next_bottom_frame) |
| 93 | { |
| 94 | struct tailcall_cache *cache = XCNEW (struct tailcall_cache); |
| 95 | void **slot; |
| 96 | |
| 97 | cache->next_bottom_frame = next_bottom_frame; |
| 98 | cache->refc = 1; |
| 99 | |
| 100 | slot = htab_find_slot (cache_htab, cache, INSERT); |
| 101 | gdb_assert (*slot == NULL); |
| 102 | *slot = cache; |
| 103 | |
| 104 | return cache; |
| 105 | } |
| 106 | |
| 107 | /* Create new reference to CACHE. */ |
| 108 | |
| 109 | static void |
| 110 | cache_ref (struct tailcall_cache *cache) |
| 111 | { |
| 112 | gdb_assert (cache->refc > 0); |
| 113 | |
| 114 | cache->refc++; |
| 115 | } |
| 116 | |
| 117 | /* Drop reference to CACHE, possibly fully freeing it and unregistering it from |
| 118 | cache_htab. */ |
| 119 | |
| 120 | static void |
| 121 | cache_unref (struct tailcall_cache *cache) |
| 122 | { |
| 123 | gdb_assert (cache->refc > 0); |
| 124 | |
| 125 | if (!--cache->refc) |
| 126 | { |
| 127 | gdb_assert (htab_find_slot (cache_htab, cache, NO_INSERT) != NULL); |
| 128 | htab_remove_elt (cache_htab, cache); |
| 129 | |
| 130 | xfree (cache->chain); |
| 131 | xfree (cache); |
| 132 | } |
| 133 | } |
| 134 | |
| 135 | /* Return 1 if FI is a non-bottom (not the callee) tail call frame. Otherwise |
| 136 | return 0. */ |
| 137 | |
| 138 | static int |
| 139 | frame_is_tailcall (struct frame_info *fi) |
| 140 | { |
| 141 | return frame_unwinder_is (fi, &dwarf2_tailcall_frame_unwind); |
| 142 | } |
| 143 | |
| 144 | /* Try to find tailcall_cache in cache_htab if FI is a part of its virtual tail |
| 145 | call chain. Otherwise return NULL. No new reference is created. */ |
| 146 | |
| 147 | static struct tailcall_cache * |
| 148 | cache_find (struct frame_info *fi) |
| 149 | { |
| 150 | struct tailcall_cache *cache; |
| 151 | void **slot; |
| 152 | |
| 153 | while (frame_is_tailcall (fi)) |
| 154 | { |
| 155 | fi = get_next_frame (fi); |
| 156 | gdb_assert (fi != NULL); |
| 157 | } |
| 158 | |
| 159 | slot = htab_find_slot (cache_htab, &fi, NO_INSERT); |
| 160 | if (slot == NULL) |
| 161 | return NULL; |
| 162 | |
| 163 | cache = (struct tailcall_cache *) *slot; |
| 164 | gdb_assert (cache != NULL); |
| 165 | return cache; |
| 166 | } |
| 167 | |
| 168 | /* Number of virtual frames between THIS_FRAME and CACHE->NEXT_BOTTOM_FRAME. |
| 169 | If THIS_FRAME is CACHE-> NEXT_BOTTOM_FRAME return -1. */ |
| 170 | |
| 171 | static int |
| 172 | existing_next_levels (struct frame_info *this_frame, |
| 173 | struct tailcall_cache *cache) |
| 174 | { |
| 175 | int retval = (frame_relative_level (this_frame) |
| 176 | - frame_relative_level (cache->next_bottom_frame) - 1); |
| 177 | |
| 178 | gdb_assert (retval >= -1); |
| 179 | |
| 180 | return retval; |
| 181 | } |
| 182 | |
| 183 | /* The number of virtual tail call frames in CHAIN. With no virtual tail call |
| 184 | frames the function would return 0 (but CHAIN does not exist in such |
| 185 | case). */ |
| 186 | |
| 187 | static int |
| 188 | pretended_chain_levels (struct call_site_chain *chain) |
| 189 | { |
| 190 | int chain_levels; |
| 191 | |
| 192 | gdb_assert (chain != NULL); |
| 193 | |
| 194 | if (chain->callers == chain->length && chain->callees == chain->length) |
| 195 | return chain->length; |
| 196 | |
| 197 | chain_levels = chain->callers + chain->callees; |
| 198 | gdb_assert (chain_levels <= chain->length); |
| 199 | |
| 200 | return chain_levels; |
| 201 | } |
| 202 | |
| 203 | /* Implementation of frame_this_id_ftype. THIS_CACHE must be already |
| 204 | initialized with tailcall_cache, THIS_FRAME must be a part of THIS_CACHE. |
| 205 | |
| 206 | Specific virtual tail call frames are tracked by INLINE_DEPTH. */ |
| 207 | |
| 208 | static void |
| 209 | tailcall_frame_this_id (struct frame_info *this_frame, void **this_cache, |
| 210 | struct frame_id *this_id) |
| 211 | { |
| 212 | struct tailcall_cache *cache = (struct tailcall_cache *) *this_cache; |
| 213 | struct frame_info *next_frame; |
| 214 | |
| 215 | /* Tail call does not make sense for a sentinel frame. */ |
| 216 | next_frame = get_next_frame (this_frame); |
| 217 | gdb_assert (next_frame != NULL); |
| 218 | |
| 219 | *this_id = get_frame_id (next_frame); |
| 220 | (*this_id).code_addr = get_frame_pc (this_frame); |
| 221 | (*this_id).code_addr_p = 1; |
| 222 | (*this_id).artificial_depth = (cache->chain_levels |
| 223 | - existing_next_levels (this_frame, cache)); |
| 224 | gdb_assert ((*this_id).artificial_depth > 0); |
| 225 | } |
| 226 | |
| 227 | /* Find PC to be unwound from THIS_FRAME. THIS_FRAME must be a part of |
| 228 | CACHE. */ |
| 229 | |
| 230 | static CORE_ADDR |
| 231 | pretend_pc (struct frame_info *this_frame, struct tailcall_cache *cache) |
| 232 | { |
| 233 | int next_levels = existing_next_levels (this_frame, cache); |
| 234 | struct call_site_chain *chain = cache->chain; |
| 235 | |
| 236 | gdb_assert (chain != NULL); |
| 237 | |
| 238 | next_levels++; |
| 239 | gdb_assert (next_levels >= 0); |
| 240 | |
| 241 | if (next_levels < chain->callees) |
| 242 | return chain->call_site[chain->length - next_levels - 1]->pc; |
| 243 | next_levels -= chain->callees; |
| 244 | |
| 245 | /* Otherwise CHAIN->CALLEES are already covered by CHAIN->CALLERS. */ |
| 246 | if (chain->callees != chain->length) |
| 247 | { |
| 248 | if (next_levels < chain->callers) |
| 249 | return chain->call_site[chain->callers - next_levels - 1]->pc; |
| 250 | next_levels -= chain->callers; |
| 251 | } |
| 252 | |
| 253 | gdb_assert (next_levels == 0); |
| 254 | return cache->prev_pc; |
| 255 | } |
| 256 | |
| 257 | /* Implementation of frame_prev_register_ftype. If no specific register |
| 258 | override is supplied NULL is returned (this is incompatible with |
| 259 | frame_prev_register_ftype semantics). next_bottom_frame and tail call |
| 260 | frames unwind the NULL case differently. */ |
| 261 | |
| 262 | struct value * |
| 263 | dwarf2_tailcall_prev_register_first (struct frame_info *this_frame, |
| 264 | void **tailcall_cachep, int regnum) |
| 265 | { |
| 266 | struct gdbarch *this_gdbarch = get_frame_arch (this_frame); |
| 267 | struct tailcall_cache *cache = (struct tailcall_cache *) *tailcall_cachep; |
| 268 | CORE_ADDR addr; |
| 269 | |
| 270 | if (regnum == gdbarch_pc_regnum (this_gdbarch)) |
| 271 | addr = pretend_pc (this_frame, cache); |
| 272 | else if (cache->prev_sp_p && regnum == gdbarch_sp_regnum (this_gdbarch)) |
| 273 | { |
| 274 | int next_levels = existing_next_levels (this_frame, cache); |
| 275 | |
| 276 | if (next_levels == cache->chain_levels - 1) |
| 277 | addr = cache->prev_sp; |
| 278 | else |
| 279 | addr = dwarf2_frame_cfa (this_frame) - cache->entry_cfa_sp_offset; |
| 280 | } |
| 281 | else |
| 282 | return NULL; |
| 283 | |
| 284 | return frame_unwind_got_address (this_frame, regnum, addr); |
| 285 | } |
| 286 | |
| 287 | /* Implementation of frame_prev_register_ftype for tail call frames. Register |
| 288 | set of virtual tail call frames is assumed to be the one of the top (caller) |
| 289 | frame - assume unchanged register value for NULL from |
| 290 | dwarf2_tailcall_prev_register_first. */ |
| 291 | |
| 292 | static struct value * |
| 293 | tailcall_frame_prev_register (struct frame_info *this_frame, |
| 294 | void **this_cache, int regnum) |
| 295 | { |
| 296 | struct tailcall_cache *cache = (struct tailcall_cache *) *this_cache; |
| 297 | struct value *val; |
| 298 | |
| 299 | gdb_assert (this_frame != cache->next_bottom_frame); |
| 300 | |
| 301 | val = dwarf2_tailcall_prev_register_first (this_frame, this_cache, regnum); |
| 302 | if (val) |
| 303 | return val; |
| 304 | |
| 305 | return frame_unwind_got_register (this_frame, regnum, regnum); |
| 306 | } |
| 307 | |
| 308 | /* Implementation of frame_sniffer_ftype. It will never find a new chain, use |
| 309 | dwarf2_tailcall_sniffer_first for the bottom (callee) frame. It will find |
| 310 | all the predecessing virtual tail call frames, it will return false when |
| 311 | there exist no more tail call frames in this chain. */ |
| 312 | |
| 313 | static int |
| 314 | tailcall_frame_sniffer (const struct frame_unwind *self, |
| 315 | struct frame_info *this_frame, void **this_cache) |
| 316 | { |
| 317 | struct frame_info *next_frame; |
| 318 | int next_levels; |
| 319 | struct tailcall_cache *cache; |
| 320 | |
| 321 | /* Inner tail call element does not make sense for a sentinel frame. */ |
| 322 | next_frame = get_next_frame (this_frame); |
| 323 | if (next_frame == NULL) |
| 324 | return 0; |
| 325 | |
| 326 | cache = cache_find (next_frame); |
| 327 | if (cache == NULL) |
| 328 | return 0; |
| 329 | |
| 330 | cache_ref (cache); |
| 331 | |
| 332 | next_levels = existing_next_levels (this_frame, cache); |
| 333 | |
| 334 | /* NEXT_LEVELS is -1 only in dwarf2_tailcall_sniffer_first. */ |
| 335 | gdb_assert (next_levels >= 0); |
| 336 | gdb_assert (next_levels <= cache->chain_levels); |
| 337 | |
| 338 | if (next_levels == cache->chain_levels) |
| 339 | { |
| 340 | cache_unref (cache); |
| 341 | return 0; |
| 342 | } |
| 343 | |
| 344 | *this_cache = cache; |
| 345 | return 1; |
| 346 | } |
| 347 | |
| 348 | /* The initial "sniffer" whether THIS_FRAME is a bottom (callee) frame of a new |
| 349 | chain to create. Keep TAILCALL_CACHEP NULL if it did not find any chain, |
| 350 | initialize it otherwise. No tail call chain is created if there are no |
| 351 | unambiguous virtual tail call frames to report. |
| 352 | |
| 353 | ENTRY_CFA_SP_OFFSETP is NULL if no special SP handling is possible, |
| 354 | otherwise *ENTRY_CFA_SP_OFFSETP is the number of bytes to subtract from tail |
| 355 | call frames frame base to get the SP value there - to simulate return |
| 356 | address pushed on the stack. */ |
| 357 | |
| 358 | void |
| 359 | dwarf2_tailcall_sniffer_first (struct frame_info *this_frame, |
| 360 | void **tailcall_cachep, |
| 361 | const LONGEST *entry_cfa_sp_offsetp) |
| 362 | { |
| 363 | CORE_ADDR prev_pc = 0, prev_sp = 0; /* GCC warning. */ |
| 364 | int prev_sp_p = 0; |
| 365 | CORE_ADDR this_pc; |
| 366 | struct gdbarch *prev_gdbarch; |
| 367 | struct call_site_chain *chain = NULL; |
| 368 | struct tailcall_cache *cache; |
| 369 | |
| 370 | gdb_assert (*tailcall_cachep == NULL); |
| 371 | |
| 372 | /* PC may be after the function if THIS_FRAME calls noreturn function, |
| 373 | get_frame_address_in_block will decrease it by 1 in such case. */ |
| 374 | this_pc = get_frame_address_in_block (this_frame); |
| 375 | |
| 376 | /* Catch any unwinding errors. */ |
| 377 | TRY |
| 378 | { |
| 379 | int sp_regnum; |
| 380 | |
| 381 | prev_gdbarch = frame_unwind_arch (this_frame); |
| 382 | |
| 383 | /* Simulate frame_unwind_pc without setting this_frame->prev_pc.p. */ |
| 384 | prev_pc = gdbarch_unwind_pc (prev_gdbarch, this_frame); |
| 385 | |
| 386 | /* call_site_find_chain can throw an exception. */ |
| 387 | chain = call_site_find_chain (prev_gdbarch, prev_pc, this_pc); |
| 388 | |
| 389 | if (entry_cfa_sp_offsetp != NULL) |
| 390 | { |
| 391 | sp_regnum = gdbarch_sp_regnum (prev_gdbarch); |
| 392 | if (sp_regnum != -1) |
| 393 | { |
| 394 | prev_sp = frame_unwind_register_unsigned (this_frame, sp_regnum); |
| 395 | prev_sp_p = 1; |
| 396 | } |
| 397 | } |
| 398 | } |
| 399 | CATCH (except, RETURN_MASK_ERROR) |
| 400 | { |
| 401 | if (entry_values_debug) |
| 402 | exception_print (gdb_stdout, except); |
| 403 | return; |
| 404 | } |
| 405 | END_CATCH |
| 406 | |
| 407 | /* Ambiguous unwind or unambiguous unwind verified as matching. */ |
| 408 | if (chain == NULL || chain->length == 0) |
| 409 | { |
| 410 | xfree (chain); |
| 411 | return; |
| 412 | } |
| 413 | |
| 414 | cache = cache_new_ref1 (this_frame); |
| 415 | *tailcall_cachep = cache; |
| 416 | cache->chain = chain; |
| 417 | cache->prev_pc = prev_pc; |
| 418 | cache->chain_levels = pretended_chain_levels (chain); |
| 419 | cache->prev_sp_p = prev_sp_p; |
| 420 | if (cache->prev_sp_p) |
| 421 | { |
| 422 | cache->prev_sp = prev_sp; |
| 423 | cache->entry_cfa_sp_offset = *entry_cfa_sp_offsetp; |
| 424 | } |
| 425 | gdb_assert (cache->chain_levels > 0); |
| 426 | } |
| 427 | |
| 428 | /* Implementation of frame_dealloc_cache_ftype. It can be called even for the |
| 429 | bottom chain frame from dwarf2_frame_dealloc_cache which is not a real |
| 430 | TAILCALL_FRAME. */ |
| 431 | |
| 432 | static void |
| 433 | tailcall_frame_dealloc_cache (struct frame_info *self, void *this_cache) |
| 434 | { |
| 435 | struct tailcall_cache *cache = (struct tailcall_cache *) this_cache; |
| 436 | |
| 437 | cache_unref (cache); |
| 438 | } |
| 439 | |
| 440 | /* Implementation of frame_prev_arch_ftype. We assume all the virtual tail |
| 441 | call frames have gdbarch of the bottom (callee) frame. */ |
| 442 | |
| 443 | static struct gdbarch * |
| 444 | tailcall_frame_prev_arch (struct frame_info *this_frame, |
| 445 | void **this_prologue_cache) |
| 446 | { |
| 447 | struct tailcall_cache *cache = (struct tailcall_cache *) *this_prologue_cache; |
| 448 | |
| 449 | return get_frame_arch (cache->next_bottom_frame); |
| 450 | } |
| 451 | |
| 452 | /* Virtual tail call frame unwinder if dwarf2_tailcall_sniffer_first finds |
| 453 | a chain to create. */ |
| 454 | |
| 455 | const struct frame_unwind dwarf2_tailcall_frame_unwind = |
| 456 | { |
| 457 | TAILCALL_FRAME, |
| 458 | default_frame_unwind_stop_reason, |
| 459 | tailcall_frame_this_id, |
| 460 | tailcall_frame_prev_register, |
| 461 | NULL, |
| 462 | tailcall_frame_sniffer, |
| 463 | tailcall_frame_dealloc_cache, |
| 464 | tailcall_frame_prev_arch |
| 465 | }; |
| 466 | |
| 467 | void |
| 468 | _initialize_tailcall_frame (void) |
| 469 | { |
| 470 | cache_htab = htab_create_alloc (50, cache_hash, cache_eq, NULL, xcalloc, |
| 471 | xfree); |
| 472 | } |