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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 | // SPDX-License-Identifier: GPL-2.0-only #include <linux/module.h> #include <linux/sort.h> #include <asm/ptrace.h> #include <asm/stacktrace.h> #include <asm/unwind.h> #include <asm/orc_types.h> #include <asm/orc_lookup.h> #define orc_warn(fmt, ...) \ printk_deferred_once(KERN_WARNING pr_fmt("WARNING: " fmt), ##__VA_ARGS__) extern int __start_orc_unwind_ip[]; extern int __stop_orc_unwind_ip[]; extern struct orc_entry __start_orc_unwind[]; extern struct orc_entry __stop_orc_unwind[]; static DEFINE_MUTEX(sort_mutex); int *cur_orc_ip_table = __start_orc_unwind_ip; struct orc_entry *cur_orc_table = __start_orc_unwind; unsigned int lookup_num_blocks; bool orc_init; static inline unsigned long orc_ip(const int *ip) { return (unsigned long)ip + *ip; } static struct orc_entry *__orc_find(int *ip_table, struct orc_entry *u_table, unsigned int num_entries, unsigned long ip) { int *first = ip_table; int *last = ip_table + num_entries - 1; int *mid = first, *found = first; if (!num_entries) return NULL; /* * Do a binary range search to find the rightmost duplicate of a given * starting address. Some entries are section terminators which are * "weak" entries for ensuring there are no gaps. They should be * ignored when they conflict with a real entry. */ while (first <= last) { mid = first + ((last - first) / 2); if (orc_ip(mid) <= ip) { found = mid; first = mid + 1; } else last = mid - 1; } return u_table + (found - ip_table); } #ifdef CONFIG_MODULES static struct orc_entry *orc_module_find(unsigned long ip) { struct module *mod; mod = __module_address(ip); if (!mod || !mod->arch.orc_unwind || !mod->arch.orc_unwind_ip) return NULL; return __orc_find(mod->arch.orc_unwind_ip, mod->arch.orc_unwind, mod->arch.num_orcs, ip); } #else static struct orc_entry *orc_module_find(unsigned long ip) { return NULL; } #endif #ifdef CONFIG_DYNAMIC_FTRACE static struct orc_entry *orc_find(unsigned long ip); /* * Ftrace dynamic trampolines do not have orc entries of their own. * But they are copies of the ftrace entries that are static and * defined in ftrace_*.S, which do have orc entries. * * If the unwinder comes across a ftrace trampoline, then find the * ftrace function that was used to create it, and use that ftrace * function's orc entry, as the placement of the return code in * the stack will be identical. */ static struct orc_entry *orc_ftrace_find(unsigned long ip) { struct ftrace_ops *ops; unsigned long caller; ops = ftrace_ops_trampoline(ip); if (!ops) return NULL; if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) caller = (unsigned long)ftrace_regs_call; else caller = (unsigned long)ftrace_call; /* Prevent unlikely recursion */ if (ip == caller) return NULL; return orc_find(caller); } #else static struct orc_entry *orc_ftrace_find(unsigned long ip) { return NULL; } #endif /* * If we crash with IP==0, the last successfully executed instruction * was probably an indirect function call with a NULL function pointer, * and we don't have unwind information for NULL. * This hardcoded ORC entry for IP==0 allows us to unwind from a NULL function * pointer into its parent and then continue normally from there. */ static struct orc_entry null_orc_entry = { .sp_offset = sizeof(long), .sp_reg = ORC_REG_SP, .bp_reg = ORC_REG_UNDEFINED, .type = ORC_TYPE_CALL }; /* Fake frame pointer entry -- used as a fallback for generated code */ static struct orc_entry orc_fp_entry = { .type = ORC_TYPE_CALL, .sp_reg = ORC_REG_BP, .sp_offset = 16, .bp_reg = ORC_REG_PREV_SP, .bp_offset = -16, .end = 0, }; static struct orc_entry *orc_find(unsigned long ip) { static struct orc_entry *orc; if (!orc_init) return NULL; if (ip == 0) return &null_orc_entry; /* For non-init vmlinux addresses, use the fast lookup table: */ if (ip >= LOOKUP_START_IP && ip < LOOKUP_STOP_IP) { unsigned int idx, start, stop; idx = (ip - LOOKUP_START_IP) / LOOKUP_BLOCK_SIZE; if (unlikely((idx >= lookup_num_blocks-1))) { orc_warn("WARNING: bad lookup idx: idx=%u num=%u ip=%pB\n", idx, lookup_num_blocks, (void *)ip); return NULL; } start = orc_lookup[idx]; stop = orc_lookup[idx + 1] + 1; if (unlikely((__start_orc_unwind + start >= __stop_orc_unwind) || (__start_orc_unwind + stop > __stop_orc_unwind))) { orc_warn("WARNING: bad lookup value: idx=%u num=%u start=%u stop=%u ip=%pB\n", idx, lookup_num_blocks, start, stop, (void *)ip); return NULL; } return __orc_find(__start_orc_unwind_ip + start, __start_orc_unwind + start, stop - start, ip); } /* vmlinux .init slow lookup: */ if (init_kernel_text(ip)) return __orc_find(__start_orc_unwind_ip, __start_orc_unwind, __stop_orc_unwind_ip - __start_orc_unwind_ip, ip); /* Module lookup: */ orc = orc_module_find(ip); if (orc) return orc; return orc_ftrace_find(ip); } static void orc_sort_swap(void *_a, void *_b, int size) { struct orc_entry *orc_a, *orc_b; struct orc_entry orc_tmp; int *a = _a, *b = _b, tmp; int delta = _b - _a; /* Swap the .orc_unwind_ip entries: */ tmp = *a; *a = *b + delta; *b = tmp - delta; /* Swap the corresponding .orc_unwind entries: */ orc_a = cur_orc_table + (a - cur_orc_ip_table); orc_b = cur_orc_table + (b - cur_orc_ip_table); orc_tmp = *orc_a; *orc_a = *orc_b; *orc_b = orc_tmp; } static int orc_sort_cmp(const void *_a, const void *_b) { struct orc_entry *orc_a; const int *a = _a, *b = _b; unsigned long a_val = orc_ip(a); unsigned long b_val = orc_ip(b); if (a_val > b_val) return 1; if (a_val < b_val) return -1; /* * The "weak" section terminator entries need to always be on the left * to ensure the lookup code skips them in favor of real entries. * These terminator entries exist to handle any gaps created by * whitelisted .o files which didn't get objtool generation. */ orc_a = cur_orc_table + (a - cur_orc_ip_table); return orc_a->sp_reg == ORC_REG_UNDEFINED && !orc_a->end ? -1 : 1; } #ifdef CONFIG_MODULES void unwind_module_init(struct module *mod, void *_orc_ip, size_t orc_ip_size, void *_orc, size_t orc_size) { int *orc_ip = _orc_ip; struct orc_entry *orc = _orc; unsigned int num_entries = orc_ip_size / sizeof(int); WARN_ON_ONCE(orc_ip_size % sizeof(int) != 0 || orc_size % sizeof(*orc) != 0 || num_entries != orc_size / sizeof(*orc)); /* * The 'cur_orc_*' globals allow the orc_sort_swap() callback to * associate an .orc_unwind_ip table entry with its corresponding * .orc_unwind entry so they can both be swapped. */ mutex_lock(&sort_mutex); cur_orc_ip_table = orc_ip; cur_orc_table = orc; sort(orc_ip, num_entries, sizeof(int), orc_sort_cmp, orc_sort_swap); mutex_unlock(&sort_mutex); mod->arch.orc_unwind_ip = orc_ip; mod->arch.orc_unwind = orc; mod->arch.num_orcs = num_entries; } #endif void __init unwind_init(void) { size_t orc_ip_size = (void *)__stop_orc_unwind_ip - (void *)__start_orc_unwind_ip; size_t orc_size = (void *)__stop_orc_unwind - (void *)__start_orc_unwind; size_t num_entries = orc_ip_size / sizeof(int); struct orc_entry *orc; int i; if (!num_entries || orc_ip_size % sizeof(int) != 0 || orc_size % sizeof(struct orc_entry) != 0 || num_entries != orc_size / sizeof(struct orc_entry)) { orc_warn("WARNING: Bad or missing .orc_unwind table. Disabling unwinder.\n"); return; } /* Sort the .orc_unwind and .orc_unwind_ip tables: */ sort(__start_orc_unwind_ip, num_entries, sizeof(int), orc_sort_cmp, orc_sort_swap); /* Initialize the fast lookup table: */ lookup_num_blocks = orc_lookup_end - orc_lookup; for (i = 0; i < lookup_num_blocks-1; i++) { orc = __orc_find(__start_orc_unwind_ip, __start_orc_unwind, num_entries, LOOKUP_START_IP + (LOOKUP_BLOCK_SIZE * i)); if (!orc) { orc_warn("WARNING: Corrupt .orc_unwind table. Disabling unwinder.\n"); return; } orc_lookup[i] = orc - __start_orc_unwind; } /* Initialize the ending block: */ orc = __orc_find(__start_orc_unwind_ip, __start_orc_unwind, num_entries, LOOKUP_STOP_IP); if (!orc) { orc_warn("WARNING: Corrupt .orc_unwind table. Disabling unwinder.\n"); return; } orc_lookup[lookup_num_blocks-1] = orc - __start_orc_unwind; orc_init = true; } unsigned long unwind_get_return_address(struct unwind_state *state) { if (unwind_done(state)) return 0; return __kernel_text_address(state->ip) ? state->ip : 0; } EXPORT_SYMBOL_GPL(unwind_get_return_address); unsigned long *unwind_get_return_address_ptr(struct unwind_state *state) { if (unwind_done(state)) return NULL; if (state->regs) return &state->regs->ip; if (state->sp) return (unsigned long *)state->sp - 1; return NULL; } static bool stack_access_ok(struct unwind_state *state, unsigned long _addr, size_t len) { struct stack_info *info = &state->stack_info; void *addr = (void *)_addr; if (!on_stack(info, addr, len) && (get_stack_info(addr, state->task, info, &state->stack_mask))) return false; return true; } static bool deref_stack_reg(struct unwind_state *state, unsigned long addr, unsigned long *val) { if (!stack_access_ok(state, addr, sizeof(long))) return false; *val = READ_ONCE_NOCHECK(*(unsigned long *)addr); return true; } static bool deref_stack_regs(struct unwind_state *state, unsigned long addr, unsigned long *ip, unsigned long *sp) { struct pt_regs *regs = (struct pt_regs *)addr; /* x86-32 support will be more complicated due to the ®s->sp hack */ BUILD_BUG_ON(IS_ENABLED(CONFIG_X86_32)); if (!stack_access_ok(state, addr, sizeof(struct pt_regs))) return false; *ip = regs->ip; *sp = regs->sp; return true; } static bool deref_stack_iret_regs(struct unwind_state *state, unsigned long addr, unsigned long *ip, unsigned long *sp) { struct pt_regs *regs = (void *)addr - IRET_FRAME_OFFSET; if (!stack_access_ok(state, addr, IRET_FRAME_SIZE)) return false; *ip = regs->ip; *sp = regs->sp; return true; } bool unwind_next_frame(struct unwind_state *state) { unsigned long ip_p, sp, orig_ip = state->ip, prev_sp = state->sp; enum stack_type prev_type = state->stack_info.type; struct orc_entry *orc; bool indirect = false; if (unwind_done(state)) return false; /* Don't let modules unload while we're reading their ORC data. */ preempt_disable(); /* End-of-stack check for user tasks: */ if (state->regs && user_mode(state->regs)) goto the_end; /* * Find the orc_entry associated with the text address. * * Decrement call return addresses by one so they work for sibling * calls and calls to noreturn functions. */ orc = orc_find(state->signal ? state->ip : state->ip - 1); if (!orc) { /* * As a fallback, try to assume this code uses a frame pointer. * This is useful for generated code, like BPF, which ORC * doesn't know about. This is just a guess, so the rest of * the unwind is no longer considered reliable. */ orc = &orc_fp_entry; state->error = true; } /* End-of-stack check for kernel threads: */ if (orc->sp_reg == ORC_REG_UNDEFINED) { if (!orc->end) goto err; goto the_end; } /* Find the previous frame's stack: */ switch (orc->sp_reg) { case ORC_REG_SP: sp = state->sp + orc->sp_offset; break; case ORC_REG_BP: sp = state->bp + orc->sp_offset; break; case ORC_REG_SP_INDIRECT: sp = state->sp + orc->sp_offset; indirect = true; break; case ORC_REG_BP_INDIRECT: sp = state->bp + orc->sp_offset; indirect = true; break; case ORC_REG_R10: if (!state->regs || !state->full_regs) { orc_warn("missing regs for base reg R10 at ip %pB\n", (void *)state->ip); goto err; } sp = state->regs->r10; break; case ORC_REG_R13: if (!state->regs || !state->full_regs) { orc_warn("missing regs for base reg R13 at ip %pB\n", (void *)state->ip); goto err; } sp = state->regs->r13; break; case ORC_REG_DI: if (!state->regs || !state->full_regs) { orc_warn("missing regs for base reg DI at ip %pB\n", (void *)state->ip); goto err; } sp = state->regs->di; break; case ORC_REG_DX: if (!state->regs || !state->full_regs) { orc_warn("missing regs for base reg DX at ip %pB\n", (void *)state->ip); goto err; } sp = state->regs->dx; break; default: orc_warn("unknown SP base reg %d for ip %pB\n", orc->sp_reg, (void *)state->ip); goto err; } if (indirect) { if (!deref_stack_reg(state, sp, &sp)) goto err; } /* Find IP, SP and possibly regs: */ switch (orc->type) { case ORC_TYPE_CALL: ip_p = sp - sizeof(long); if (!deref_stack_reg(state, ip_p, &state->ip)) goto err; state->ip = ftrace_graph_ret_addr(state->task, &state->graph_idx, state->ip, (void *)ip_p); state->sp = sp; state->regs = NULL; state->signal = false; break; case ORC_TYPE_REGS: if (!deref_stack_regs(state, sp, &state->ip, &state->sp)) { orc_warn("can't dereference registers at %p for ip %pB\n", (void *)sp, (void *)orig_ip); goto err; } state->regs = (struct pt_regs *)sp; state->full_regs = true; state->signal = true; break; case ORC_TYPE_REGS_IRET: if (!deref_stack_iret_regs(state, sp, &state->ip, &state->sp)) { orc_warn("can't dereference iret registers at %p for ip %pB\n", (void *)sp, (void *)orig_ip); goto err; } state->regs = (void *)sp - IRET_FRAME_OFFSET; state->full_regs = false; state->signal = true; break; default: orc_warn("unknown .orc_unwind entry type %d for ip %pB\n", orc->type, (void *)orig_ip); break; } /* Find BP: */ switch (orc->bp_reg) { case ORC_REG_UNDEFINED: if (state->regs && state->full_regs) state->bp = state->regs->bp; break; case ORC_REG_PREV_SP: if (!deref_stack_reg(state, sp + orc->bp_offset, &state->bp)) goto err; break; case ORC_REG_BP: if (!deref_stack_reg(state, state->bp + orc->bp_offset, &state->bp)) goto err; break; default: orc_warn("unknown BP base reg %d for ip %pB\n", orc->bp_reg, (void *)orig_ip); goto err; } /* Prevent a recursive loop due to bad ORC data: */ if (state->stack_info.type == prev_type && on_stack(&state->stack_info, (void *)state->sp, sizeof(long)) && state->sp <= prev_sp) { orc_warn("stack going in the wrong direction? ip=%pB\n", (void *)orig_ip); goto err; } preempt_enable(); return true; err: state->error = true; the_end: preempt_enable(); state->stack_info.type = STACK_TYPE_UNKNOWN; return false; } EXPORT_SYMBOL_GPL(unwind_next_frame); void __unwind_start(struct unwind_state *state, struct task_struct *task, struct pt_regs *regs, unsigned long *first_frame) { memset(state, 0, sizeof(*state)); state->task = task; /* * Refuse to unwind the stack of a task while it's executing on another * CPU. This check is racy, but that's ok: the unwinder has other * checks to prevent it from going off the rails. */ if (task_on_another_cpu(task)) goto done; if (regs) { if (user_mode(regs)) goto done; state->ip = regs->ip; state->sp = kernel_stack_pointer(regs); state->bp = regs->bp; state->regs = regs; state->full_regs = true; state->signal = true; } else if (task == current) { asm volatile("lea (%%rip), %0\n\t" "mov %%rsp, %1\n\t" "mov %%rbp, %2\n\t" : "=r" (state->ip), "=r" (state->sp), "=r" (state->bp)); } else { struct inactive_task_frame *frame = (void *)task->thread.sp; state->sp = task->thread.sp; state->bp = READ_ONCE_NOCHECK(frame->bp); state->ip = READ_ONCE_NOCHECK(frame->ret_addr); } if (get_stack_info((unsigned long *)state->sp, state->task, &state->stack_info, &state->stack_mask)) { /* * We weren't on a valid stack. It's possible that * we overflowed a valid stack into a guard page. * See if the next page up is valid so that we can * generate some kind of backtrace if this happens. */ void *next_page = (void *)PAGE_ALIGN((unsigned long)state->sp); if (get_stack_info(next_page, state->task, &state->stack_info, &state->stack_mask)) return; } /* * The caller can provide the address of the first frame directly * (first_frame) or indirectly (regs->sp) to indicate which stack frame * to start unwinding at. Skip ahead until we reach it. */ /* When starting from regs, skip the regs frame: */ if (regs) { unwind_next_frame(state); return; } /* Otherwise, skip ahead to the user-specified starting frame: */ while (!unwind_done(state) && (!on_stack(&state->stack_info, first_frame, sizeof(long)) || state->sp <= (unsigned long)first_frame)) unwind_next_frame(state); return; done: state->stack_info.type = STACK_TYPE_UNKNOWN; return; } EXPORT_SYMBOL_GPL(__unwind_start); |