| 1 | /* Virtual tail call frames unwinder for GDB. |
| 2 | |
| 3 | Copyright (C) 2010-2019 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 | #include "gdbarch.h" |
| 32 | |
| 33 | /* Contains struct tailcall_cache indexed by next_bottom_frame. */ |
| 34 | static htab_t cache_htab; |
| 35 | |
| 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. */ |
| 39 | struct tailcall_cache |
| 40 | { |
| 41 | /* It must be the first one of this struct. It is the furthest callee. */ |
| 42 | struct frame_info *next_bottom_frame; |
| 43 | |
| 44 | /* Reference count. The whole chain of virtual tail call frames shares one |
| 45 | tailcall_cache. */ |
| 46 | int refc; |
| 47 | |
| 48 | /* Associated found virtual tail call frames chain, it is never NULL. */ |
| 49 | struct call_site_chain *chain; |
| 50 | |
| 51 | /* Cached pretended_chain_levels result. */ |
| 52 | int chain_levels; |
| 53 | |
| 54 | /* Unwound PC from the top (caller) frame, as it is not contained |
| 55 | in CHAIN. */ |
| 56 | CORE_ADDR prev_pc; |
| 57 | |
| 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; |
| 63 | CORE_ADDR prev_sp; |
| 64 | LONGEST entry_cfa_sp_offset; |
| 65 | }; |
| 66 | |
| 67 | /* hash_f for htab_create_alloc of cache_htab. */ |
| 68 | |
| 69 | static hashval_t |
| 70 | cache_hash (const void *arg) |
| 71 | { |
| 72 | const struct tailcall_cache *cache = (const struct tailcall_cache *) arg; |
| 73 | |
| 74 | return htab_hash_pointer (cache->next_bottom_frame); |
| 75 | } |
| 76 | |
| 77 | /* eq_f for htab_create_alloc of cache_htab. */ |
| 78 | |
| 79 | static int |
| 80 | cache_eq (const void *arg1, const void *arg2) |
| 81 | { |
| 82 | const struct tailcall_cache *cache1 = (const struct tailcall_cache *) arg1; |
| 83 | const struct tailcall_cache *cache2 = (const struct tailcall_cache *) arg2; |
| 84 | |
| 85 | return cache1->next_bottom_frame == cache2->next_bottom_frame; |
| 86 | } |
| 87 | |
| 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 |
| 90 | tailcall_cache. */ |
| 91 | |
| 92 | static struct tailcall_cache * |
| 93 | cache_new_ref1 (struct frame_info *next_bottom_frame) |
| 94 | { |
| 95 | struct tailcall_cache *cache = XCNEW (struct tailcall_cache); |
| 96 | void **slot; |
| 97 | |
| 98 | cache->next_bottom_frame = next_bottom_frame; |
| 99 | cache->refc = 1; |
| 100 | |
| 101 | slot = htab_find_slot (cache_htab, cache, INSERT); |
| 102 | gdb_assert (*slot == NULL); |
| 103 | *slot = cache; |
| 104 | |
| 105 | return cache; |
| 106 | } |
| 107 | |
| 108 | /* Create new reference to CACHE. */ |
| 109 | |
| 110 | static void |
| 111 | cache_ref (struct tailcall_cache *cache) |
| 112 | { |
| 113 | gdb_assert (cache->refc > 0); |
| 114 | |
| 115 | cache->refc++; |
| 116 | } |
| 117 | |
| 118 | /* Drop reference to CACHE, possibly fully freeing it and unregistering it from |
| 119 | cache_htab. */ |
| 120 | |
| 121 | static void |
| 122 | cache_unref (struct tailcall_cache *cache) |
| 123 | { |
| 124 | gdb_assert (cache->refc > 0); |
| 125 | |
| 126 | if (!--cache->refc) |
| 127 | { |
| 128 | gdb_assert (htab_find_slot (cache_htab, cache, NO_INSERT) != NULL); |
| 129 | htab_remove_elt (cache_htab, cache); |
| 130 | |
| 131 | xfree (cache->chain); |
| 132 | xfree (cache); |
| 133 | } |
| 134 | } |
| 135 | |
| 136 | /* Return 1 if FI is a non-bottom (not the callee) tail call frame. Otherwise |
| 137 | return 0. */ |
| 138 | |
| 139 | static int |
| 140 | frame_is_tailcall (struct frame_info *fi) |
| 141 | { |
| 142 | return frame_unwinder_is (fi, &dwarf2_tailcall_frame_unwind); |
| 143 | } |
| 144 | |
| 145 | /* Try to find tailcall_cache in cache_htab if FI is a part of its virtual tail |
| 146 | call chain. Otherwise return NULL. No new reference is created. */ |
| 147 | |
| 148 | static struct tailcall_cache * |
| 149 | cache_find (struct frame_info *fi) |
| 150 | { |
| 151 | struct tailcall_cache *cache; |
| 152 | void **slot; |
| 153 | |
| 154 | while (frame_is_tailcall (fi)) |
| 155 | { |
| 156 | fi = get_next_frame (fi); |
| 157 | gdb_assert (fi != NULL); |
| 158 | } |
| 159 | |
| 160 | slot = htab_find_slot (cache_htab, &fi, NO_INSERT); |
| 161 | if (slot == NULL) |
| 162 | return NULL; |
| 163 | |
| 164 | cache = (struct tailcall_cache *) *slot; |
| 165 | gdb_assert (cache != NULL); |
| 166 | return cache; |
| 167 | } |
| 168 | |
| 169 | /* Number of virtual frames between THIS_FRAME and CACHE->NEXT_BOTTOM_FRAME. |
| 170 | If THIS_FRAME is CACHE-> NEXT_BOTTOM_FRAME return -1. */ |
| 171 | |
| 172 | static int |
| 173 | existing_next_levels (struct frame_info *this_frame, |
| 174 | struct tailcall_cache *cache) |
| 175 | { |
| 176 | int retval = (frame_relative_level (this_frame) |
| 177 | - frame_relative_level (cache->next_bottom_frame) - 1); |
| 178 | |
| 179 | gdb_assert (retval >= -1); |
| 180 | |
| 181 | return retval; |
| 182 | } |
| 183 | |
| 184 | /* The number of virtual tail call frames in CHAIN. With no virtual tail call |
| 185 | frames the function would return 0 (but CHAIN does not exist in such |
| 186 | case). */ |
| 187 | |
| 188 | static int |
| 189 | pretended_chain_levels (struct call_site_chain *chain) |
| 190 | { |
| 191 | int chain_levels; |
| 192 | |
| 193 | gdb_assert (chain != NULL); |
| 194 | |
| 195 | if (chain->callers == chain->length && chain->callees == chain->length) |
| 196 | return chain->length; |
| 197 | |
| 198 | chain_levels = chain->callers + chain->callees; |
| 199 | gdb_assert (chain_levels <= chain->length); |
| 200 | |
| 201 | return chain_levels; |
| 202 | } |
| 203 | |
| 204 | /* Implementation of frame_this_id_ftype. THIS_CACHE must be already |
| 205 | initialized with tailcall_cache, THIS_FRAME must be a part of THIS_CACHE. |
| 206 | |
| 207 | Specific virtual tail call frames are tracked by INLINE_DEPTH. */ |
| 208 | |
| 209 | static void |
| 210 | tailcall_frame_this_id (struct frame_info *this_frame, void **this_cache, |
| 211 | struct frame_id *this_id) |
| 212 | { |
| 213 | struct tailcall_cache *cache = (struct tailcall_cache *) *this_cache; |
| 214 | struct frame_info *next_frame; |
| 215 | |
| 216 | /* Tail call does not make sense for a sentinel frame. */ |
| 217 | next_frame = get_next_frame (this_frame); |
| 218 | gdb_assert (next_frame != NULL); |
| 219 | |
| 220 | *this_id = get_frame_id (next_frame); |
| 221 | (*this_id).code_addr = get_frame_pc (this_frame); |
| 222 | (*this_id).code_addr_p = 1; |
| 223 | (*this_id).artificial_depth = (cache->chain_levels |
| 224 | - existing_next_levels (this_frame, cache)); |
| 225 | gdb_assert ((*this_id).artificial_depth > 0); |
| 226 | } |
| 227 | |
| 228 | /* Find PC to be unwound from THIS_FRAME. THIS_FRAME must be a part of |
| 229 | CACHE. */ |
| 230 | |
| 231 | static CORE_ADDR |
| 232 | pretend_pc (struct frame_info *this_frame, struct tailcall_cache *cache) |
| 233 | { |
| 234 | int next_levels = existing_next_levels (this_frame, cache); |
| 235 | struct call_site_chain *chain = cache->chain; |
| 236 | |
| 237 | gdb_assert (chain != NULL); |
| 238 | |
| 239 | next_levels++; |
| 240 | gdb_assert (next_levels >= 0); |
| 241 | |
| 242 | if (next_levels < chain->callees) |
| 243 | return chain->call_site[chain->length - next_levels - 1]->pc; |
| 244 | next_levels -= chain->callees; |
| 245 | |
| 246 | /* Otherwise CHAIN->CALLEES are already covered by CHAIN->CALLERS. */ |
| 247 | if (chain->callees != chain->length) |
| 248 | { |
| 249 | if (next_levels < chain->callers) |
| 250 | return chain->call_site[chain->callers - next_levels - 1]->pc; |
| 251 | next_levels -= chain->callers; |
| 252 | } |
| 253 | |
| 254 | gdb_assert (next_levels == 0); |
| 255 | return cache->prev_pc; |
| 256 | } |
| 257 | |
| 258 | /* Implementation of frame_prev_register_ftype. If no specific register |
| 259 | override is supplied NULL is returned (this is incompatible with |
| 260 | frame_prev_register_ftype semantics). next_bottom_frame and tail call |
| 261 | frames unwind the NULL case differently. */ |
| 262 | |
| 263 | struct value * |
| 264 | dwarf2_tailcall_prev_register_first (struct frame_info *this_frame, |
| 265 | void **tailcall_cachep, int regnum) |
| 266 | { |
| 267 | struct gdbarch *this_gdbarch = get_frame_arch (this_frame); |
| 268 | struct tailcall_cache *cache = (struct tailcall_cache *) *tailcall_cachep; |
| 269 | CORE_ADDR addr; |
| 270 | |
| 271 | if (regnum == gdbarch_pc_regnum (this_gdbarch)) |
| 272 | addr = pretend_pc (this_frame, cache); |
| 273 | else if (cache->prev_sp_p && regnum == gdbarch_sp_regnum (this_gdbarch)) |
| 274 | { |
| 275 | int next_levels = existing_next_levels (this_frame, cache); |
| 276 | |
| 277 | if (next_levels == cache->chain_levels - 1) |
| 278 | addr = cache->prev_sp; |
| 279 | else |
| 280 | addr = dwarf2_frame_cfa (this_frame) - cache->entry_cfa_sp_offset; |
| 281 | } |
| 282 | else |
| 283 | return NULL; |
| 284 | |
| 285 | return frame_unwind_got_address (this_frame, regnum, addr); |
| 286 | } |
| 287 | |
| 288 | /* Implementation of frame_prev_register_ftype for tail call frames. Register |
| 289 | set of virtual tail call frames is assumed to be the one of the top (caller) |
| 290 | frame - assume unchanged register value for NULL from |
| 291 | dwarf2_tailcall_prev_register_first. */ |
| 292 | |
| 293 | static struct value * |
| 294 | tailcall_frame_prev_register (struct frame_info *this_frame, |
| 295 | void **this_cache, int regnum) |
| 296 | { |
| 297 | struct tailcall_cache *cache = (struct tailcall_cache *) *this_cache; |
| 298 | struct value *val; |
| 299 | |
| 300 | gdb_assert (this_frame != cache->next_bottom_frame); |
| 301 | |
| 302 | val = dwarf2_tailcall_prev_register_first (this_frame, this_cache, regnum); |
| 303 | if (val) |
| 304 | return val; |
| 305 | |
| 306 | return frame_unwind_got_register (this_frame, regnum, regnum); |
| 307 | } |
| 308 | |
| 309 | /* Implementation of frame_sniffer_ftype. It will never find a new chain, use |
| 310 | dwarf2_tailcall_sniffer_first for the bottom (callee) frame. It will find |
| 311 | all the predecessing virtual tail call frames, it will return false when |
| 312 | there exist no more tail call frames in this chain. */ |
| 313 | |
| 314 | static int |
| 315 | tailcall_frame_sniffer (const struct frame_unwind *self, |
| 316 | struct frame_info *this_frame, void **this_cache) |
| 317 | { |
| 318 | struct frame_info *next_frame; |
| 319 | int next_levels; |
| 320 | struct tailcall_cache *cache; |
| 321 | |
| 322 | if (!dwarf2_frame_unwinders_enabled_p) |
| 323 | return 0; |
| 324 | |
| 325 | /* Inner tail call element does not make sense for a sentinel frame. */ |
| 326 | next_frame = get_next_frame (this_frame); |
| 327 | if (next_frame == NULL) |
| 328 | return 0; |
| 329 | |
| 330 | cache = cache_find (next_frame); |
| 331 | if (cache == NULL) |
| 332 | return 0; |
| 333 | |
| 334 | cache_ref (cache); |
| 335 | |
| 336 | next_levels = existing_next_levels (this_frame, cache); |
| 337 | |
| 338 | /* NEXT_LEVELS is -1 only in dwarf2_tailcall_sniffer_first. */ |
| 339 | gdb_assert (next_levels >= 0); |
| 340 | gdb_assert (next_levels <= cache->chain_levels); |
| 341 | |
| 342 | if (next_levels == cache->chain_levels) |
| 343 | { |
| 344 | cache_unref (cache); |
| 345 | return 0; |
| 346 | } |
| 347 | |
| 348 | *this_cache = cache; |
| 349 | return 1; |
| 350 | } |
| 351 | |
| 352 | /* The initial "sniffer" whether THIS_FRAME is a bottom (callee) frame of a new |
| 353 | chain to create. Keep TAILCALL_CACHEP NULL if it did not find any chain, |
| 354 | initialize it otherwise. No tail call chain is created if there are no |
| 355 | unambiguous virtual tail call frames to report. |
| 356 | |
| 357 | ENTRY_CFA_SP_OFFSETP is NULL if no special SP handling is possible, |
| 358 | otherwise *ENTRY_CFA_SP_OFFSETP is the number of bytes to subtract from tail |
| 359 | call frames frame base to get the SP value there - to simulate return |
| 360 | address pushed on the stack. */ |
| 361 | |
| 362 | void |
| 363 | dwarf2_tailcall_sniffer_first (struct frame_info *this_frame, |
| 364 | void **tailcall_cachep, |
| 365 | const LONGEST *entry_cfa_sp_offsetp) |
| 366 | { |
| 367 | CORE_ADDR prev_pc = 0, prev_sp = 0; /* GCC warning. */ |
| 368 | int prev_sp_p = 0; |
| 369 | CORE_ADDR this_pc; |
| 370 | struct gdbarch *prev_gdbarch; |
| 371 | struct call_site_chain *chain = NULL; |
| 372 | struct tailcall_cache *cache; |
| 373 | |
| 374 | gdb_assert (*tailcall_cachep == NULL); |
| 375 | |
| 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); |
| 379 | |
| 380 | /* Catch any unwinding errors. */ |
| 381 | try |
| 382 | { |
| 383 | int sp_regnum; |
| 384 | |
| 385 | prev_gdbarch = frame_unwind_arch (this_frame); |
| 386 | |
| 387 | /* Simulate frame_unwind_pc without setting this_frame->prev_pc.p. */ |
| 388 | prev_pc = gdbarch_unwind_pc (prev_gdbarch, this_frame); |
| 389 | |
| 390 | /* call_site_find_chain can throw an exception. */ |
| 391 | chain = call_site_find_chain (prev_gdbarch, prev_pc, this_pc); |
| 392 | |
| 393 | if (entry_cfa_sp_offsetp != NULL) |
| 394 | { |
| 395 | sp_regnum = gdbarch_sp_regnum (prev_gdbarch); |
| 396 | if (sp_regnum != -1) |
| 397 | { |
| 398 | prev_sp = frame_unwind_register_unsigned (this_frame, sp_regnum); |
| 399 | prev_sp_p = 1; |
| 400 | } |
| 401 | } |
| 402 | } |
| 403 | catch (const gdb_exception_error &except) |
| 404 | { |
| 405 | if (entry_values_debug) |
| 406 | exception_print (gdb_stdout, except); |
| 407 | return; |
| 408 | } |
| 409 | |
| 410 | /* Ambiguous unwind or unambiguous unwind verified as matching. */ |
| 411 | if (chain == NULL || chain->length == 0) |
| 412 | { |
| 413 | xfree (chain); |
| 414 | return; |
| 415 | } |
| 416 | |
| 417 | cache = cache_new_ref1 (this_frame); |
| 418 | *tailcall_cachep = cache; |
| 419 | cache->chain = chain; |
| 420 | cache->prev_pc = prev_pc; |
| 421 | cache->chain_levels = pretended_chain_levels (chain); |
| 422 | cache->prev_sp_p = prev_sp_p; |
| 423 | if (cache->prev_sp_p) |
| 424 | { |
| 425 | cache->prev_sp = prev_sp; |
| 426 | cache->entry_cfa_sp_offset = *entry_cfa_sp_offsetp; |
| 427 | } |
| 428 | gdb_assert (cache->chain_levels > 0); |
| 429 | } |
| 430 | |
| 431 | /* Implementation of frame_dealloc_cache_ftype. It can be called even for the |
| 432 | bottom chain frame from dwarf2_frame_dealloc_cache which is not a real |
| 433 | TAILCALL_FRAME. */ |
| 434 | |
| 435 | static void |
| 436 | tailcall_frame_dealloc_cache (struct frame_info *self, void *this_cache) |
| 437 | { |
| 438 | struct tailcall_cache *cache = (struct tailcall_cache *) this_cache; |
| 439 | |
| 440 | cache_unref (cache); |
| 441 | } |
| 442 | |
| 443 | /* Implementation of frame_prev_arch_ftype. We assume all the virtual tail |
| 444 | call frames have gdbarch of the bottom (callee) frame. */ |
| 445 | |
| 446 | static struct gdbarch * |
| 447 | tailcall_frame_prev_arch (struct frame_info *this_frame, |
| 448 | void **this_prologue_cache) |
| 449 | { |
| 450 | struct tailcall_cache *cache = (struct tailcall_cache *) *this_prologue_cache; |
| 451 | |
| 452 | return get_frame_arch (cache->next_bottom_frame); |
| 453 | } |
| 454 | |
| 455 | /* Virtual tail call frame unwinder if dwarf2_tailcall_sniffer_first finds |
| 456 | a chain to create. */ |
| 457 | |
| 458 | const struct frame_unwind dwarf2_tailcall_frame_unwind = |
| 459 | { |
| 460 | TAILCALL_FRAME, |
| 461 | default_frame_unwind_stop_reason, |
| 462 | tailcall_frame_this_id, |
| 463 | tailcall_frame_prev_register, |
| 464 | NULL, |
| 465 | tailcall_frame_sniffer, |
| 466 | tailcall_frame_dealloc_cache, |
| 467 | tailcall_frame_prev_arch |
| 468 | }; |
| 469 | |
| 470 | void |
| 471 | _initialize_tailcall_frame (void) |
| 472 | { |
| 473 | cache_htab = htab_create_alloc (50, cache_hash, cache_eq, NULL, xcalloc, |
| 474 | xfree); |
| 475 | } |