1 /* 2 * os-posix-lib.c 3 * 4 * Copyright (c) 2003-2008 Fabrice Bellard 5 * Copyright (c) 2010 Red Hat, Inc. 6 * 7 * QEMU library functions on POSIX which are shared between QEMU and 8 * the QEMU tools. 9 * 10 * Permission is hereby granted, free of charge, to any person obtaining a copy 11 * of this software and associated documentation files (the "Software"), to deal 12 * in the Software without restriction, including without limitation the rights 13 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 14 * copies of the Software, and to permit persons to whom the Software is 15 * furnished to do so, subject to the following conditions: 16 * 17 * The above copyright notice and this permission notice shall be included in 18 * all copies or substantial portions of the Software. 19 * 20 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 21 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 22 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL 23 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 24 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 25 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN 26 * THE SOFTWARE. 27 */ 28 29 #include "qemu/osdep.h" 30 #include <termios.h> 31 32 #include <glib/gprintf.h> 33 34 #include "qemu-common.h" 35 #include "sysemu/sysemu.h" 36 #include "trace.h" 37 #include "qapi/error.h" 38 #include "qemu/error-report.h" 39 #include "qemu/madvise.h" 40 #include "qemu/sockets.h" 41 #include "qemu/thread.h" 42 #include <libgen.h> 43 #include "qemu/cutils.h" 44 #include "qemu/compiler.h" 45 #include "qemu/units.h" 46 47 #ifdef CONFIG_LINUX 48 #include <sys/syscall.h> 49 #endif 50 51 #ifdef __FreeBSD__ 52 #include <sys/sysctl.h> 53 #include <sys/user.h> 54 #include <sys/thr.h> 55 #include <libutil.h> 56 #endif 57 58 #ifdef __NetBSD__ 59 #include <sys/sysctl.h> 60 #include <lwp.h> 61 #endif 62 63 #ifdef __APPLE__ 64 #include <mach-o/dyld.h> 65 #endif 66 67 #ifdef __HAIKU__ 68 #include <kernel/image.h> 69 #endif 70 71 #include "qemu/mmap-alloc.h" 72 73 #ifdef CONFIG_DEBUG_STACK_USAGE 74 #include "qemu/error-report.h" 75 #endif 76 77 #define MAX_MEM_PREALLOC_THREAD_COUNT 16 78 79 struct MemsetThread; 80 81 typedef struct MemsetContext { 82 bool all_threads_created; 83 bool any_thread_failed; 84 struct MemsetThread *threads; 85 int num_threads; 86 } MemsetContext; 87 88 struct MemsetThread { 89 char *addr; 90 size_t numpages; 91 size_t hpagesize; 92 QemuThread pgthread; 93 sigjmp_buf env; 94 MemsetContext *context; 95 }; 96 typedef struct MemsetThread MemsetThread; 97 98 /* used by sigbus_handler() */ 99 static MemsetContext *sigbus_memset_context; 100 struct sigaction sigbus_oldact; 101 static QemuMutex sigbus_mutex; 102 103 static QemuMutex page_mutex; 104 static QemuCond page_cond; 105 106 int qemu_get_thread_id(void) 107 { 108 #if defined(__linux__) 109 return syscall(SYS_gettid); 110 #elif defined(__FreeBSD__) 111 /* thread id is up to INT_MAX */ 112 long tid; 113 thr_self(&tid); 114 return (int)tid; 115 #elif defined(__NetBSD__) 116 return _lwp_self(); 117 #elif defined(__OpenBSD__) 118 return getthrid(); 119 #else 120 return getpid(); 121 #endif 122 } 123 124 int qemu_daemon(int nochdir, int noclose) 125 { 126 return daemon(nochdir, noclose); 127 } 128 129 bool qemu_write_pidfile(const char *path, Error **errp) 130 { 131 int fd; 132 char pidstr[32]; 133 134 while (1) { 135 struct stat a, b; 136 struct flock lock = { 137 .l_type = F_WRLCK, 138 .l_whence = SEEK_SET, 139 .l_len = 0, 140 }; 141 142 fd = qemu_open_old(path, O_CREAT | O_WRONLY, S_IRUSR | S_IWUSR); 143 if (fd == -1) { 144 error_setg_errno(errp, errno, "Cannot open pid file"); 145 return false; 146 } 147 148 if (fstat(fd, &b) < 0) { 149 error_setg_errno(errp, errno, "Cannot stat file"); 150 goto fail_close; 151 } 152 153 if (fcntl(fd, F_SETLK, &lock)) { 154 error_setg_errno(errp, errno, "Cannot lock pid file"); 155 goto fail_close; 156 } 157 158 /* 159 * Now make sure the path we locked is the same one that now 160 * exists on the filesystem. 161 */ 162 if (stat(path, &a) < 0) { 163 /* 164 * PID file disappeared, someone else must be racing with 165 * us, so try again. 166 */ 167 close(fd); 168 continue; 169 } 170 171 if (a.st_ino == b.st_ino) { 172 break; 173 } 174 175 /* 176 * PID file was recreated, someone else must be racing with 177 * us, so try again. 178 */ 179 close(fd); 180 } 181 182 if (ftruncate(fd, 0) < 0) { 183 error_setg_errno(errp, errno, "Failed to truncate pid file"); 184 goto fail_unlink; 185 } 186 187 snprintf(pidstr, sizeof(pidstr), FMT_pid "\n", getpid()); 188 if (write(fd, pidstr, strlen(pidstr)) != strlen(pidstr)) { 189 error_setg(errp, "Failed to write pid file"); 190 goto fail_unlink; 191 } 192 193 return true; 194 195 fail_unlink: 196 unlink(path); 197 fail_close: 198 close(fd); 199 return false; 200 } 201 202 /* alloc shared memory pages */ 203 void *qemu_anon_ram_alloc(size_t size, uint64_t *alignment, bool shared, 204 bool noreserve) 205 { 206 const uint32_t qemu_map_flags = (shared ? QEMU_MAP_SHARED : 0) | 207 (noreserve ? QEMU_MAP_NORESERVE : 0); 208 size_t align = QEMU_VMALLOC_ALIGN; 209 void *ptr = qemu_ram_mmap(-1, size, align, qemu_map_flags, 0); 210 211 if (ptr == MAP_FAILED) { 212 return NULL; 213 } 214 215 if (alignment) { 216 *alignment = align; 217 } 218 219 trace_qemu_anon_ram_alloc(size, ptr); 220 return ptr; 221 } 222 223 void qemu_anon_ram_free(void *ptr, size_t size) 224 { 225 trace_qemu_anon_ram_free(ptr, size); 226 qemu_ram_munmap(-1, ptr, size); 227 } 228 229 void qemu_set_block(int fd) 230 { 231 int f; 232 f = fcntl(fd, F_GETFL); 233 assert(f != -1); 234 f = fcntl(fd, F_SETFL, f & ~O_NONBLOCK); 235 assert(f != -1); 236 } 237 238 int qemu_try_set_nonblock(int fd) 239 { 240 int f; 241 f = fcntl(fd, F_GETFL); 242 if (f == -1) { 243 return -errno; 244 } 245 if (fcntl(fd, F_SETFL, f | O_NONBLOCK) == -1) { 246 return -errno; 247 } 248 return 0; 249 } 250 251 void qemu_set_nonblock(int fd) 252 { 253 int f; 254 f = qemu_try_set_nonblock(fd); 255 assert(f == 0); 256 } 257 258 int socket_set_fast_reuse(int fd) 259 { 260 int val = 1, ret; 261 262 ret = setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, 263 (const char *)&val, sizeof(val)); 264 265 assert(ret == 0); 266 267 return ret; 268 } 269 270 void qemu_set_cloexec(int fd) 271 { 272 int f; 273 f = fcntl(fd, F_GETFD); 274 assert(f != -1); 275 f = fcntl(fd, F_SETFD, f | FD_CLOEXEC); 276 assert(f != -1); 277 } 278 279 /* 280 * Creates a pipe with FD_CLOEXEC set on both file descriptors 281 */ 282 int qemu_pipe(int pipefd[2]) 283 { 284 int ret; 285 286 #ifdef CONFIG_PIPE2 287 ret = pipe2(pipefd, O_CLOEXEC); 288 if (ret != -1 || errno != ENOSYS) { 289 return ret; 290 } 291 #endif 292 ret = pipe(pipefd); 293 if (ret == 0) { 294 qemu_set_cloexec(pipefd[0]); 295 qemu_set_cloexec(pipefd[1]); 296 } 297 298 return ret; 299 } 300 301 char * 302 qemu_get_local_state_pathname(const char *relative_pathname) 303 { 304 g_autofree char *dir = g_strdup_printf("%s/%s", 305 CONFIG_QEMU_LOCALSTATEDIR, 306 relative_pathname); 307 return get_relocated_path(dir); 308 } 309 310 void qemu_set_tty_echo(int fd, bool echo) 311 { 312 struct termios tty; 313 314 tcgetattr(fd, &tty); 315 316 if (echo) { 317 tty.c_lflag |= ECHO | ECHONL | ICANON | IEXTEN; 318 } else { 319 tty.c_lflag &= ~(ECHO | ECHONL | ICANON | IEXTEN); 320 } 321 322 tcsetattr(fd, TCSANOW, &tty); 323 } 324 325 static const char *exec_dir; 326 327 void qemu_init_exec_dir(const char *argv0) 328 { 329 char *p = NULL; 330 char buf[PATH_MAX]; 331 332 if (exec_dir) { 333 return; 334 } 335 336 #if defined(__linux__) 337 { 338 int len; 339 len = readlink("/proc/self/exe", buf, sizeof(buf) - 1); 340 if (len > 0) { 341 buf[len] = 0; 342 p = buf; 343 } 344 } 345 #elif defined(__FreeBSD__) \ 346 || (defined(__NetBSD__) && defined(KERN_PROC_PATHNAME)) 347 { 348 #if defined(__FreeBSD__) 349 static int mib[4] = {CTL_KERN, KERN_PROC, KERN_PROC_PATHNAME, -1}; 350 #else 351 static int mib[4] = {CTL_KERN, KERN_PROC_ARGS, -1, KERN_PROC_PATHNAME}; 352 #endif 353 size_t len = sizeof(buf) - 1; 354 355 *buf = '\0'; 356 if (!sysctl(mib, ARRAY_SIZE(mib), buf, &len, NULL, 0) && 357 *buf) { 358 buf[sizeof(buf) - 1] = '\0'; 359 p = buf; 360 } 361 } 362 #elif defined(__APPLE__) 363 { 364 char fpath[PATH_MAX]; 365 uint32_t len = sizeof(fpath); 366 if (_NSGetExecutablePath(fpath, &len) == 0) { 367 p = realpath(fpath, buf); 368 if (!p) { 369 return; 370 } 371 } 372 } 373 #elif defined(__HAIKU__) 374 { 375 image_info ii; 376 int32_t c = 0; 377 378 *buf = '\0'; 379 while (get_next_image_info(0, &c, &ii) == B_OK) { 380 if (ii.type == B_APP_IMAGE) { 381 strncpy(buf, ii.name, sizeof(buf)); 382 buf[sizeof(buf) - 1] = 0; 383 p = buf; 384 break; 385 } 386 } 387 } 388 #endif 389 /* If we don't have any way of figuring out the actual executable 390 location then try argv[0]. */ 391 if (!p && argv0) { 392 p = realpath(argv0, buf); 393 } 394 if (p) { 395 exec_dir = g_path_get_dirname(p); 396 } else { 397 exec_dir = CONFIG_BINDIR; 398 } 399 } 400 401 const char *qemu_get_exec_dir(void) 402 { 403 return exec_dir; 404 } 405 406 #ifdef CONFIG_LINUX 407 static void sigbus_handler(int signal, siginfo_t *siginfo, void *ctx) 408 #else /* CONFIG_LINUX */ 409 static void sigbus_handler(int signal) 410 #endif /* CONFIG_LINUX */ 411 { 412 int i; 413 414 if (sigbus_memset_context) { 415 for (i = 0; i < sigbus_memset_context->num_threads; i++) { 416 MemsetThread *thread = &sigbus_memset_context->threads[i]; 417 418 if (qemu_thread_is_self(&thread->pgthread)) { 419 siglongjmp(thread->env, 1); 420 } 421 } 422 } 423 424 #ifdef CONFIG_LINUX 425 /* 426 * We assume that the MCE SIGBUS handler could have been registered. We 427 * should never receive BUS_MCEERR_AO on any of our threads, but only on 428 * the main thread registered for PR_MCE_KILL_EARLY. Further, we should not 429 * receive BUS_MCEERR_AR triggered by action of other threads on one of 430 * our threads. So, no need to check for unrelated SIGBUS when seeing one 431 * for our threads. 432 * 433 * We will forward to the MCE handler, which will either handle the SIGBUS 434 * or reinstall the default SIGBUS handler and reraise the SIGBUS. The 435 * default SIGBUS handler will crash the process, so we don't care. 436 */ 437 if (sigbus_oldact.sa_flags & SA_SIGINFO) { 438 sigbus_oldact.sa_sigaction(signal, siginfo, ctx); 439 return; 440 } 441 #endif /* CONFIG_LINUX */ 442 warn_report("os_mem_prealloc: unrelated SIGBUS detected and ignored"); 443 } 444 445 static void *do_touch_pages(void *arg) 446 { 447 MemsetThread *memset_args = (MemsetThread *)arg; 448 sigset_t set, oldset; 449 int ret = 0; 450 451 /* 452 * On Linux, the page faults from the loop below can cause mmap_sem 453 * contention with allocation of the thread stacks. Do not start 454 * clearing until all threads have been created. 455 */ 456 qemu_mutex_lock(&page_mutex); 457 while (!memset_args->context->all_threads_created) { 458 qemu_cond_wait(&page_cond, &page_mutex); 459 } 460 qemu_mutex_unlock(&page_mutex); 461 462 /* unblock SIGBUS */ 463 sigemptyset(&set); 464 sigaddset(&set, SIGBUS); 465 pthread_sigmask(SIG_UNBLOCK, &set, &oldset); 466 467 if (sigsetjmp(memset_args->env, 1)) { 468 ret = -EFAULT; 469 } else { 470 char *addr = memset_args->addr; 471 size_t numpages = memset_args->numpages; 472 size_t hpagesize = memset_args->hpagesize; 473 size_t i; 474 for (i = 0; i < numpages; i++) { 475 /* 476 * Read & write back the same value, so we don't 477 * corrupt existing user/app data that might be 478 * stored. 479 * 480 * 'volatile' to stop compiler optimizing this away 481 * to a no-op 482 */ 483 *(volatile char *)addr = *addr; 484 addr += hpagesize; 485 } 486 } 487 pthread_sigmask(SIG_SETMASK, &oldset, NULL); 488 return (void *)(uintptr_t)ret; 489 } 490 491 static void *do_madv_populate_write_pages(void *arg) 492 { 493 MemsetThread *memset_args = (MemsetThread *)arg; 494 const size_t size = memset_args->numpages * memset_args->hpagesize; 495 char * const addr = memset_args->addr; 496 int ret = 0; 497 498 /* See do_touch_pages(). */ 499 qemu_mutex_lock(&page_mutex); 500 while (!memset_args->context->all_threads_created) { 501 qemu_cond_wait(&page_cond, &page_mutex); 502 } 503 qemu_mutex_unlock(&page_mutex); 504 505 if (size && qemu_madvise(addr, size, QEMU_MADV_POPULATE_WRITE)) { 506 ret = -errno; 507 } 508 return (void *)(uintptr_t)ret; 509 } 510 511 static inline int get_memset_num_threads(size_t hpagesize, size_t numpages, 512 int smp_cpus) 513 { 514 long host_procs = sysconf(_SC_NPROCESSORS_ONLN); 515 int ret = 1; 516 517 if (host_procs > 0) { 518 ret = MIN(MIN(host_procs, MAX_MEM_PREALLOC_THREAD_COUNT), smp_cpus); 519 } 520 521 /* Especially with gigantic pages, don't create more threads than pages. */ 522 ret = MIN(ret, numpages); 523 /* Don't start threads to prealloc comparatively little memory. */ 524 ret = MIN(ret, MAX(1, hpagesize * numpages / (64 * MiB))); 525 526 /* In case sysconf() fails, we fall back to single threaded */ 527 return ret; 528 } 529 530 static int touch_all_pages(char *area, size_t hpagesize, size_t numpages, 531 int smp_cpus, bool use_madv_populate_write) 532 { 533 static gsize initialized = 0; 534 MemsetContext context = { 535 .num_threads = get_memset_num_threads(hpagesize, numpages, smp_cpus), 536 }; 537 size_t numpages_per_thread, leftover; 538 void *(*touch_fn)(void *); 539 int ret = 0, i = 0; 540 char *addr = area; 541 542 if (g_once_init_enter(&initialized)) { 543 qemu_mutex_init(&page_mutex); 544 qemu_cond_init(&page_cond); 545 g_once_init_leave(&initialized, 1); 546 } 547 548 if (use_madv_populate_write) { 549 /* Avoid creating a single thread for MADV_POPULATE_WRITE */ 550 if (context.num_threads == 1) { 551 if (qemu_madvise(area, hpagesize * numpages, 552 QEMU_MADV_POPULATE_WRITE)) { 553 return -errno; 554 } 555 return 0; 556 } 557 touch_fn = do_madv_populate_write_pages; 558 } else { 559 touch_fn = do_touch_pages; 560 } 561 562 context.threads = g_new0(MemsetThread, context.num_threads); 563 numpages_per_thread = numpages / context.num_threads; 564 leftover = numpages % context.num_threads; 565 for (i = 0; i < context.num_threads; i++) { 566 context.threads[i].addr = addr; 567 context.threads[i].numpages = numpages_per_thread + (i < leftover); 568 context.threads[i].hpagesize = hpagesize; 569 context.threads[i].context = &context; 570 qemu_thread_create(&context.threads[i].pgthread, "touch_pages", 571 touch_fn, &context.threads[i], 572 QEMU_THREAD_JOINABLE); 573 addr += context.threads[i].numpages * hpagesize; 574 } 575 576 if (!use_madv_populate_write) { 577 sigbus_memset_context = &context; 578 } 579 580 qemu_mutex_lock(&page_mutex); 581 context.all_threads_created = true; 582 qemu_cond_broadcast(&page_cond); 583 qemu_mutex_unlock(&page_mutex); 584 585 for (i = 0; i < context.num_threads; i++) { 586 int tmp = (uintptr_t)qemu_thread_join(&context.threads[i].pgthread); 587 588 if (tmp) { 589 ret = tmp; 590 } 591 } 592 593 if (!use_madv_populate_write) { 594 sigbus_memset_context = NULL; 595 } 596 g_free(context.threads); 597 598 return ret; 599 } 600 601 static bool madv_populate_write_possible(char *area, size_t pagesize) 602 { 603 return !qemu_madvise(area, pagesize, QEMU_MADV_POPULATE_WRITE) || 604 errno != EINVAL; 605 } 606 607 void os_mem_prealloc(int fd, char *area, size_t memory, int smp_cpus, 608 Error **errp) 609 { 610 static gsize initialized; 611 int ret; 612 size_t hpagesize = qemu_fd_getpagesize(fd); 613 size_t numpages = DIV_ROUND_UP(memory, hpagesize); 614 bool use_madv_populate_write; 615 struct sigaction act; 616 617 /* 618 * Sense on every invocation, as MADV_POPULATE_WRITE cannot be used for 619 * some special mappings, such as mapping /dev/mem. 620 */ 621 use_madv_populate_write = madv_populate_write_possible(area, hpagesize); 622 623 if (!use_madv_populate_write) { 624 if (g_once_init_enter(&initialized)) { 625 qemu_mutex_init(&sigbus_mutex); 626 g_once_init_leave(&initialized, 1); 627 } 628 629 qemu_mutex_lock(&sigbus_mutex); 630 memset(&act, 0, sizeof(act)); 631 #ifdef CONFIG_LINUX 632 act.sa_sigaction = &sigbus_handler; 633 act.sa_flags = SA_SIGINFO; 634 #else /* CONFIG_LINUX */ 635 act.sa_handler = &sigbus_handler; 636 act.sa_flags = 0; 637 #endif /* CONFIG_LINUX */ 638 639 ret = sigaction(SIGBUS, &act, &sigbus_oldact); 640 if (ret) { 641 qemu_mutex_unlock(&sigbus_mutex); 642 error_setg_errno(errp, errno, 643 "os_mem_prealloc: failed to install signal handler"); 644 return; 645 } 646 } 647 648 /* touch pages simultaneously */ 649 ret = touch_all_pages(area, hpagesize, numpages, smp_cpus, 650 use_madv_populate_write); 651 if (ret) { 652 error_setg_errno(errp, -ret, 653 "os_mem_prealloc: preallocating memory failed"); 654 } 655 656 if (!use_madv_populate_write) { 657 ret = sigaction(SIGBUS, &sigbus_oldact, NULL); 658 if (ret) { 659 /* Terminate QEMU since it can't recover from error */ 660 perror("os_mem_prealloc: failed to reinstall signal handler"); 661 exit(1); 662 } 663 qemu_mutex_unlock(&sigbus_mutex); 664 } 665 } 666 667 char *qemu_get_pid_name(pid_t pid) 668 { 669 char *name = NULL; 670 671 #if defined(__FreeBSD__) 672 /* BSDs don't have /proc, but they provide a nice substitute */ 673 struct kinfo_proc *proc = kinfo_getproc(pid); 674 675 if (proc) { 676 name = g_strdup(proc->ki_comm); 677 free(proc); 678 } 679 #else 680 /* Assume a system with reasonable procfs */ 681 char *pid_path; 682 size_t len; 683 684 pid_path = g_strdup_printf("/proc/%d/cmdline", pid); 685 g_file_get_contents(pid_path, &name, &len, NULL); 686 g_free(pid_path); 687 #endif 688 689 return name; 690 } 691 692 693 pid_t qemu_fork(Error **errp) 694 { 695 sigset_t oldmask, newmask; 696 struct sigaction sig_action; 697 int saved_errno; 698 pid_t pid; 699 700 /* 701 * Need to block signals now, so that child process can safely 702 * kill off caller's signal handlers without a race. 703 */ 704 sigfillset(&newmask); 705 if (pthread_sigmask(SIG_SETMASK, &newmask, &oldmask) != 0) { 706 error_setg_errno(errp, errno, 707 "cannot block signals"); 708 return -1; 709 } 710 711 pid = fork(); 712 saved_errno = errno; 713 714 if (pid < 0) { 715 /* attempt to restore signal mask, but ignore failure, to 716 * avoid obscuring the fork failure */ 717 (void)pthread_sigmask(SIG_SETMASK, &oldmask, NULL); 718 error_setg_errno(errp, saved_errno, 719 "cannot fork child process"); 720 errno = saved_errno; 721 return -1; 722 } else if (pid) { 723 /* parent process */ 724 725 /* Restore our original signal mask now that the child is 726 * safely running. Only documented failures are EFAULT (not 727 * possible, since we are using just-grabbed mask) or EINVAL 728 * (not possible, since we are using correct arguments). */ 729 (void)pthread_sigmask(SIG_SETMASK, &oldmask, NULL); 730 } else { 731 /* child process */ 732 size_t i; 733 734 /* Clear out all signal handlers from parent so nothing 735 * unexpected can happen in our child once we unblock 736 * signals */ 737 sig_action.sa_handler = SIG_DFL; 738 sig_action.sa_flags = 0; 739 sigemptyset(&sig_action.sa_mask); 740 741 for (i = 1; i < NSIG; i++) { 742 /* Only possible errors are EFAULT or EINVAL The former 743 * won't happen, the latter we expect, so no need to check 744 * return value */ 745 (void)sigaction(i, &sig_action, NULL); 746 } 747 748 /* Unmask all signals in child, since we've no idea what the 749 * caller's done with their signal mask and don't want to 750 * propagate that to children */ 751 sigemptyset(&newmask); 752 if (pthread_sigmask(SIG_SETMASK, &newmask, NULL) != 0) { 753 Error *local_err = NULL; 754 error_setg_errno(&local_err, errno, 755 "cannot unblock signals"); 756 error_report_err(local_err); 757 _exit(1); 758 } 759 } 760 return pid; 761 } 762 763 void *qemu_alloc_stack(size_t *sz) 764 { 765 void *ptr, *guardpage; 766 int flags; 767 #ifdef CONFIG_DEBUG_STACK_USAGE 768 void *ptr2; 769 #endif 770 size_t pagesz = qemu_real_host_page_size(); 771 #ifdef _SC_THREAD_STACK_MIN 772 /* avoid stacks smaller than _SC_THREAD_STACK_MIN */ 773 long min_stack_sz = sysconf(_SC_THREAD_STACK_MIN); 774 *sz = MAX(MAX(min_stack_sz, 0), *sz); 775 #endif 776 /* adjust stack size to a multiple of the page size */ 777 *sz = ROUND_UP(*sz, pagesz); 778 /* allocate one extra page for the guard page */ 779 *sz += pagesz; 780 781 flags = MAP_PRIVATE | MAP_ANONYMOUS; 782 #if defined(MAP_STACK) && defined(__OpenBSD__) 783 /* Only enable MAP_STACK on OpenBSD. Other OS's such as 784 * Linux/FreeBSD/NetBSD have a flag with the same name 785 * but have differing functionality. OpenBSD will SEGV 786 * if it spots execution with a stack pointer pointing 787 * at memory that was not allocated with MAP_STACK. 788 */ 789 flags |= MAP_STACK; 790 #endif 791 792 ptr = mmap(NULL, *sz, PROT_READ | PROT_WRITE, flags, -1, 0); 793 if (ptr == MAP_FAILED) { 794 perror("failed to allocate memory for stack"); 795 abort(); 796 } 797 798 #if defined(HOST_IA64) 799 /* separate register stack */ 800 guardpage = ptr + (((*sz - pagesz) / 2) & ~pagesz); 801 #elif defined(HOST_HPPA) 802 /* stack grows up */ 803 guardpage = ptr + *sz - pagesz; 804 #else 805 /* stack grows down */ 806 guardpage = ptr; 807 #endif 808 if (mprotect(guardpage, pagesz, PROT_NONE) != 0) { 809 perror("failed to set up stack guard page"); 810 abort(); 811 } 812 813 #ifdef CONFIG_DEBUG_STACK_USAGE 814 for (ptr2 = ptr + pagesz; ptr2 < ptr + *sz; ptr2 += sizeof(uint32_t)) { 815 *(uint32_t *)ptr2 = 0xdeadbeaf; 816 } 817 #endif 818 819 return ptr; 820 } 821 822 #ifdef CONFIG_DEBUG_STACK_USAGE 823 static __thread unsigned int max_stack_usage; 824 #endif 825 826 void qemu_free_stack(void *stack, size_t sz) 827 { 828 #ifdef CONFIG_DEBUG_STACK_USAGE 829 unsigned int usage; 830 void *ptr; 831 832 for (ptr = stack + qemu_real_host_page_size(); ptr < stack + sz; 833 ptr += sizeof(uint32_t)) { 834 if (*(uint32_t *)ptr != 0xdeadbeaf) { 835 break; 836 } 837 } 838 usage = sz - (uintptr_t) (ptr - stack); 839 if (usage > max_stack_usage) { 840 error_report("thread %d max stack usage increased from %u to %u", 841 qemu_get_thread_id(), max_stack_usage, usage); 842 max_stack_usage = usage; 843 } 844 #endif 845 846 munmap(stack, sz); 847 } 848 849 /* 850 * Disable CFI checks. 851 * We are going to call a signal hander directly. Such handler may or may not 852 * have been defined in our binary, so there's no guarantee that the pointer 853 * used to set the handler is a cfi-valid pointer. Since the handlers are 854 * stored in kernel memory, changing the handler to an attacker-defined 855 * function requires being able to call a sigaction() syscall, 856 * which is not as easy as overwriting a pointer in memory. 857 */ 858 QEMU_DISABLE_CFI 859 void sigaction_invoke(struct sigaction *action, 860 struct qemu_signalfd_siginfo *info) 861 { 862 siginfo_t si = {}; 863 si.si_signo = info->ssi_signo; 864 si.si_errno = info->ssi_errno; 865 si.si_code = info->ssi_code; 866 867 /* Convert the minimal set of fields defined by POSIX. 868 * Positive si_code values are reserved for kernel-generated 869 * signals, where the valid siginfo fields are determined by 870 * the signal number. But according to POSIX, it is unspecified 871 * whether SI_USER and SI_QUEUE have values less than or equal to 872 * zero. 873 */ 874 if (info->ssi_code == SI_USER || info->ssi_code == SI_QUEUE || 875 info->ssi_code <= 0) { 876 /* SIGTERM, etc. */ 877 si.si_pid = info->ssi_pid; 878 si.si_uid = info->ssi_uid; 879 } else if (info->ssi_signo == SIGILL || info->ssi_signo == SIGFPE || 880 info->ssi_signo == SIGSEGV || info->ssi_signo == SIGBUS) { 881 si.si_addr = (void *)(uintptr_t)info->ssi_addr; 882 } else if (info->ssi_signo == SIGCHLD) { 883 si.si_pid = info->ssi_pid; 884 si.si_status = info->ssi_status; 885 si.si_uid = info->ssi_uid; 886 } 887 action->sa_sigaction(info->ssi_signo, &si, NULL); 888 } 889 890 #ifndef HOST_NAME_MAX 891 # ifdef _POSIX_HOST_NAME_MAX 892 # define HOST_NAME_MAX _POSIX_HOST_NAME_MAX 893 # else 894 # define HOST_NAME_MAX 255 895 # endif 896 #endif 897 898 char *qemu_get_host_name(Error **errp) 899 { 900 long len = -1; 901 g_autofree char *hostname = NULL; 902 903 #ifdef _SC_HOST_NAME_MAX 904 len = sysconf(_SC_HOST_NAME_MAX); 905 #endif /* _SC_HOST_NAME_MAX */ 906 907 if (len < 0) { 908 len = HOST_NAME_MAX; 909 } 910 911 /* Unfortunately, gethostname() below does not guarantee a 912 * NULL terminated string. Therefore, allocate one byte more 913 * to be sure. */ 914 hostname = g_new0(char, len + 1); 915 916 if (gethostname(hostname, len) < 0) { 917 error_setg_errno(errp, errno, 918 "cannot get hostname"); 919 return NULL; 920 } 921 922 return g_steal_pointer(&hostname); 923 } 924 925 size_t qemu_get_host_physmem(void) 926 { 927 #ifdef _SC_PHYS_PAGES 928 long pages = sysconf(_SC_PHYS_PAGES); 929 if (pages > 0) { 930 if (pages > SIZE_MAX / qemu_real_host_page_size()) { 931 return SIZE_MAX; 932 } else { 933 return pages * qemu_real_host_page_size(); 934 } 935 } 936 #endif 937 return 0; 938 } 939