1 // SPDX-License-Identifier: GPL-2.0 2 #include <assert.h> 3 #include <linux/compiler.h> 4 #include <elfutils/libdw.h> 5 #include <elfutils/libdwfl.h> 6 #include <inttypes.h> 7 #include <errno.h> 8 #include "debug.h" 9 #include "dso.h" 10 #include <dwarf-regs.h> 11 #include "unwind.h" 12 #include "unwind-libdw.h" 13 #include "machine.h" 14 #include "map.h" 15 #include "symbol.h" 16 #include "thread.h" 17 #include <linux/types.h> 18 #include <linux/zalloc.h> 19 #include "event.h" 20 #include "perf_regs.h" 21 #include "callchain.h" 22 #include "util/env.h" 23 24 /* 25 * The dwfl thread argument passed to functions like memory_read. Memory has to 26 * be allocated to persist of multiple uses of the dwfl. 27 */ 28 struct dwfl_ui_thread_info { 29 /* Back link to the dwfl. */ 30 Dwfl *dwfl; 31 /* The current unwind info, only 1 is supported. */ 32 struct unwind_info *ui; 33 }; 34 35 static char *debuginfo_path; 36 37 static int __find_debuginfo(Dwfl_Module *mod __maybe_unused, void **userdata, 38 const char *modname __maybe_unused, Dwarf_Addr base __maybe_unused, 39 const char *file_name, const char *debuglink_file __maybe_unused, 40 GElf_Word debuglink_crc __maybe_unused, char **debuginfo_file_name) 41 { 42 const struct dso *dso = *userdata; 43 44 assert(dso); 45 if (dso__symsrc_filename(dso) && strcmp(file_name, dso__symsrc_filename(dso))) 46 *debuginfo_file_name = strdup(dso__symsrc_filename(dso)); 47 return -1; 48 } 49 50 void libdw__invalidate_dwfl(struct maps *maps, void *arg) 51 { 52 struct dwfl_ui_thread_info *dwfl_ui_ti = arg; 53 54 if (!dwfl_ui_ti) 55 return; 56 57 assert(dwfl_ui_ti->ui == NULL); 58 maps__set_libdw_addr_space_dwfl(maps, NULL); 59 dwfl_end(dwfl_ui_ti->dwfl); 60 free(dwfl_ui_ti); 61 } 62 63 static const Dwfl_Callbacks offline_callbacks = { 64 .find_debuginfo = __find_debuginfo, 65 .debuginfo_path = &debuginfo_path, 66 .section_address = dwfl_offline_section_address, 67 // .find_elf is not set as we use dwfl_report_elf() instead. 68 }; 69 70 static int __report_module(struct addr_location *al, u64 ip, 71 struct unwind_info *ui) 72 { 73 Dwfl_Module *mod; 74 struct dso *dso = NULL; 75 Dwarf_Addr base; 76 /* 77 * Some callers will use al->sym, so we can't just use the 78 * cheaper thread__find_map() here. 79 */ 80 thread__find_symbol(ui->thread, PERF_RECORD_MISC_USER, ip, al); 81 82 if (al->map) 83 dso = map__dso(al->map); 84 85 if (!dso) 86 return 0; 87 88 /* 89 * The generated JIT DSO files only map the code segment without 90 * ELF headers. Since JIT codes used to be packed in a memory 91 * segment, calculating the base address using pgoff falls into 92 * a different code in another DSO. So just use the map->start 93 * directly to pick the correct one. 94 */ 95 if (!strncmp(dso__long_name(dso), "/tmp/jitted-", 12)) 96 base = map__start(al->map); 97 else 98 base = map__start(al->map) - map__pgoff(al->map); 99 100 mod = dwfl_addrmodule(ui->dwfl, ip); 101 if (mod) { 102 Dwarf_Addr s; 103 104 dwfl_module_info(mod, NULL, &s, NULL, NULL, NULL, NULL, NULL); 105 if (s != base) 106 mod = NULL; 107 } 108 109 if (!mod) { 110 char filename[PATH_MAX]; 111 112 __symbol__join_symfs(filename, sizeof(filename), dso__long_name(dso)); 113 /* Don't hang up on device files like /dev/dri/renderD128. */ 114 if (is_regular_file(filename)) { 115 mod = dwfl_report_elf(ui->dwfl, dso__short_name(dso), filename, -1, 116 base, false); 117 } 118 } 119 if (!mod) { 120 char filename[PATH_MAX]; 121 122 if (dso__build_id_filename(dso, filename, sizeof(filename), false)) 123 mod = dwfl_report_elf(ui->dwfl, dso__short_name(dso), filename, -1, 124 base, false); 125 } 126 127 if (mod) { 128 void **userdatap; 129 130 dwfl_module_info(mod, &userdatap, NULL, NULL, NULL, NULL, NULL, NULL); 131 *userdatap = dso; 132 } 133 134 return mod && dwfl_addrmodule(ui->dwfl, ip) == mod ? 0 : -1; 135 } 136 137 static int report_module(u64 ip, struct unwind_info *ui) 138 { 139 struct addr_location al; 140 int res; 141 142 addr_location__init(&al); 143 res = __report_module(&al, ip, ui); 144 addr_location__exit(&al); 145 return res; 146 } 147 148 /* 149 * Store all entries within entries array, 150 * we will process it after we finish unwind. 151 */ 152 static int entry(u64 ip, struct unwind_info *ui) 153 154 { 155 struct unwind_entry *e = &ui->entries[ui->idx++]; 156 struct addr_location al; 157 158 addr_location__init(&al); 159 if (__report_module(&al, ip, ui)) { 160 addr_location__exit(&al); 161 return -1; 162 } 163 164 e->ip = ip; 165 e->ms.thread = thread__get(al.thread); 166 e->ms.map = map__get(al.map); 167 e->ms.sym = al.sym; 168 169 pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n", 170 al.sym ? al.sym->name : "''", 171 ip, 172 al.map ? map__map_ip(al.map, ip) : (u64) 0); 173 addr_location__exit(&al); 174 return 0; 175 } 176 177 static pid_t next_thread(Dwfl *dwfl __maybe_unused, void *arg, void **thread_argp) 178 { 179 struct dwfl_ui_thread_info *dwfl_ui_ti = arg; 180 181 /* We want only single thread to be processed. */ 182 if (*thread_argp != NULL) 183 return 0; 184 185 assert(dwfl_ui_ti->ui != NULL); 186 *thread_argp = arg; 187 return thread__tid(dwfl_ui_ti->ui->thread); 188 } 189 190 static bool get_thread(Dwfl *dwfl __maybe_unused, pid_t tid, void *arg, 191 void **thread_argp) 192 { 193 struct dwfl_ui_thread_info *dwfl_ui_ti = arg; 194 195 assert(dwfl_ui_ti->ui != NULL); 196 if (tid != thread__tid(dwfl_ui_ti->ui->thread)) 197 return false; 198 199 *thread_argp = arg; 200 return true; 201 } 202 203 static int access_dso_mem(struct unwind_info *ui, Dwarf_Addr addr, 204 Dwarf_Word *data) 205 { 206 struct addr_location al; 207 ssize_t size; 208 struct dso *dso; 209 210 addr_location__init(&al); 211 if (!thread__find_map(ui->thread, PERF_RECORD_MISC_USER, addr, &al)) { 212 pr_debug("unwind: no map for %lx\n", (unsigned long)addr); 213 goto out_fail; 214 } 215 dso = map__dso(al.map); 216 if (!dso) 217 goto out_fail; 218 219 size = dso__data_read_addr(dso, al.map, ui->machine, addr, (u8 *) data, sizeof(*data)); 220 221 addr_location__exit(&al); 222 return !(size == sizeof(*data)); 223 out_fail: 224 addr_location__exit(&al); 225 return -1; 226 } 227 228 static bool memory_read(Dwfl *dwfl __maybe_unused, Dwarf_Addr addr, Dwarf_Word *result, 229 void *arg) 230 { 231 struct dwfl_ui_thread_info *dwfl_ui_ti = arg; 232 struct unwind_info *ui = dwfl_ui_ti->ui; 233 struct stack_dump *stack = &ui->sample->user_stack; 234 u64 start, end; 235 int offset; 236 int ret; 237 238 if (!ui->sample->user_regs) 239 return false; 240 241 ret = perf_reg_value(&start, ui->sample->user_regs, 242 perf_arch_reg_sp(ui->e_machine)); 243 if (ret) 244 return false; 245 246 end = start + stack->size; 247 248 /* Check overflow. */ 249 if (addr + sizeof(Dwarf_Word) < addr) 250 return false; 251 252 if (addr < start || addr + sizeof(Dwarf_Word) > end) { 253 ret = access_dso_mem(ui, addr, result); 254 if (ret) { 255 pr_debug("unwind: access_mem 0x%" PRIx64 " not inside range" 256 " 0x%" PRIx64 "-0x%" PRIx64 "\n", 257 addr, start, end); 258 return false; 259 } 260 return true; 261 } 262 263 offset = addr - start; 264 *result = *(Dwarf_Word *)&stack->data[offset]; 265 pr_debug("unwind: access_mem addr 0x%" PRIx64 ", val %lx, offset %d\n", 266 addr, (unsigned long)*result, offset); 267 return true; 268 } 269 270 static bool libdw_set_initial_registers(Dwfl_Thread *thread, void *arg) 271 { 272 struct dwfl_ui_thread_info *dwfl_ui_ti = arg; 273 struct unwind_info *ui = dwfl_ui_ti->ui; 274 struct regs_dump *user_regs = perf_sample__user_regs(ui->sample); 275 Dwarf_Word *dwarf_regs; 276 int max_dwarf_reg = 0; 277 bool ret; 278 uint16_t e_machine = ui->e_machine; 279 int e_flags = ui->e_flags; 280 uint64_t ip_perf_reg = perf_arch_reg_ip(e_machine); 281 Dwarf_Word val = 0; 282 283 284 /* 285 * For every possible perf register in the bitmap determine the dwarf 286 * register and use to compute the max. 287 */ 288 for (int perf_reg = 0; perf_reg < 64; perf_reg++) { 289 if (user_regs->mask & (1ULL << perf_reg)) { 290 int dwarf_reg = 291 get_dwarf_regnum_for_perf_regnum(perf_reg, e_machine, 292 e_flags, 293 /*only_libdw_supported=*/true); 294 if (dwarf_reg > max_dwarf_reg) 295 max_dwarf_reg = dwarf_reg; 296 } 297 } 298 299 dwarf_regs = calloc(max_dwarf_reg + 1, sizeof(*dwarf_regs)); 300 if (!dwarf_regs) 301 return false; 302 303 for (int perf_reg = 0; perf_reg < 64; perf_reg++) { 304 if (user_regs->mask & (1ULL << perf_reg)) { 305 int dwarf_reg = 306 get_dwarf_regnum_for_perf_regnum(perf_reg, e_machine, 307 e_flags, 308 /*only_libdw_supported=*/true); 309 if (dwarf_reg >= 0) { 310 val = 0; 311 if (perf_reg_value(&val, user_regs, perf_reg) == 0) 312 dwarf_regs[dwarf_reg] = val; 313 } 314 } 315 } 316 if (perf_reg_value(&val, user_regs, ip_perf_reg) == 0) 317 dwfl_thread_state_register_pc(thread, val); 318 319 ret = dwfl_thread_state_registers(thread, 0, max_dwarf_reg + 1, dwarf_regs); 320 free(dwarf_regs); 321 return ret; 322 } 323 324 static const Dwfl_Thread_Callbacks callbacks = { 325 .next_thread = next_thread, 326 .get_thread = get_thread, 327 .memory_read = memory_read, 328 .set_initial_registers = libdw_set_initial_registers, 329 }; 330 331 static int 332 frame_callback(Dwfl_Frame *state, void *arg) 333 { 334 struct unwind_info *ui = arg; 335 Dwarf_Addr pc; 336 bool isactivation; 337 338 if (!dwfl_frame_pc(state, &pc, NULL)) { 339 if (!ui->best_effort) 340 pr_err("%s", dwfl_errmsg(-1)); 341 return DWARF_CB_ABORT; 342 } 343 344 // report the module before we query for isactivation 345 report_module(pc, ui); 346 347 if (!dwfl_frame_pc(state, &pc, &isactivation)) { 348 if (!ui->best_effort) 349 pr_err("%s", dwfl_errmsg(-1)); 350 return DWARF_CB_ABORT; 351 } 352 353 if (!isactivation) 354 --pc; 355 356 return entry(pc, ui) || !(--ui->max_stack) ? 357 DWARF_CB_ABORT : DWARF_CB_OK; 358 } 359 360 int libdw__get_entries(unwind_entry_cb_t cb, void *arg, 361 struct thread *thread, 362 struct perf_sample *data, 363 int max_stack, 364 bool best_effort) 365 { 366 struct maps *maps = thread__maps(thread); 367 struct machine *machine = maps__machine(maps); 368 uint32_t e_flags = 0; 369 uint16_t e_machine = thread__e_machine(thread, machine, &e_flags); 370 struct dwfl_ui_thread_info *dwfl_ui_ti; 371 static struct unwind_info *ui; 372 Dwfl *dwfl; 373 Dwarf_Word ip; 374 int err = -EINVAL, i, entries; 375 376 if (!data->user_regs || !data->user_regs->regs) 377 return 0; 378 379 ui = zalloc(sizeof(*ui) + sizeof(ui->entries[0]) * max_stack); 380 if (!ui) 381 return -ENOMEM; 382 383 *ui = (struct unwind_info){ 384 .sample = data, 385 .thread = thread, 386 .machine = machine, 387 .cb = cb, 388 .arg = arg, 389 .max_stack = max_stack, 390 .e_machine = e_machine, 391 .e_flags = e_flags, 392 .best_effort = best_effort 393 }; 394 395 dwfl_ui_ti = maps__libdw_addr_space_dwfl(maps); 396 if (dwfl_ui_ti) { 397 dwfl = dwfl_ui_ti->dwfl; 398 } else { 399 dwfl_ui_ti = zalloc(sizeof(*dwfl_ui_ti)); 400 dwfl = dwfl_begin(&offline_callbacks); 401 if (!dwfl) 402 goto out; 403 404 dwfl_ui_ti->dwfl = dwfl; 405 maps__set_libdw_addr_space_dwfl(maps, dwfl_ui_ti); 406 } 407 assert(dwfl_ui_ti->ui == NULL); 408 assert(dwfl_ui_ti->dwfl == dwfl); 409 assert(dwfl_ui_ti == maps__libdw_addr_space_dwfl(maps)); 410 dwfl_ui_ti->ui = ui; 411 ui->dwfl = dwfl; 412 413 err = perf_reg_value(&ip, data->user_regs, perf_arch_reg_ip(e_machine)); 414 if (err) 415 goto out; 416 417 err = report_module(ip, ui); 418 if (err) 419 goto out; 420 421 dwfl_attach_state(dwfl, /*elf=*/NULL, thread__pid(thread), &callbacks, 422 /* Dwfl thread function argument*/dwfl_ui_ti); 423 // Ignore thread already attached error. 424 425 err = dwfl_getthread_frames(dwfl, thread__tid(thread), frame_callback, 426 /* Dwfl frame function argument*/ui); 427 428 if (err && ui->max_stack != max_stack) 429 err = 0; 430 431 /* 432 * Display what we got based on the order setup. 433 */ 434 for (i = 0; i < ui->idx && !err; i++) { 435 int j = i; 436 437 if (callchain_param.order == ORDER_CALLER) 438 j = ui->idx - i - 1; 439 440 err = ui->entries[j].ip ? ui->cb(&ui->entries[j], ui->arg) : 0; 441 } 442 443 out: 444 if (err) 445 pr_debug("unwind: failed with '%s'\n", dwfl_errmsg(-1)); 446 447 for (i = 0; i < ui->idx; i++) 448 map_symbol__exit(&ui->entries[i].ms); 449 450 dwfl_ui_ti->ui = NULL; 451 entries = (int)ui->idx; 452 free(ui); 453 /* 454 * Unwinder return contract: 455 * > 0 : unwinding succeeded (stops fallback). If we found frames but hit an error 456 * (e.g. truncated stack), report success to preserve existing frames. 457 * 0 : unwinding failed without yielding frames. Ignore non-fatal errors 458 * (e.g. missing debug info, DWARF corruption) to allow fallback unwinder or 459 * kernel callchain resolution to proceed. 460 * < 0 : fatal error (e.g. -ENOMEM). Aborts unwinding entirely. 461 */ 462 if (err) 463 return (err == -ENOMEM) ? -ENOMEM : (entries > 0 ? 1 : 0); 464 return entries; 465 } 466