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/sockets.h" 39 #include "qemu/thread.h" 40 #include <libgen.h> 41 #include "qemu/cutils.h" 42 #include "qemu/compiler.h" 43 44 #ifdef CONFIG_LINUX 45 #include <sys/syscall.h> 46 #endif 47 48 #ifdef __FreeBSD__ 49 #include <sys/sysctl.h> 50 #include <sys/user.h> 51 #include <sys/thr.h> 52 #include <libutil.h> 53 #endif 54 55 #ifdef __NetBSD__ 56 #include <sys/sysctl.h> 57 #include <lwp.h> 58 #endif 59 60 #ifdef __APPLE__ 61 #include <mach-o/dyld.h> 62 #endif 63 64 #ifdef __HAIKU__ 65 #include <kernel/image.h> 66 #endif 67 68 #include "qemu/mmap-alloc.h" 69 70 #ifdef CONFIG_DEBUG_STACK_USAGE 71 #include "qemu/error-report.h" 72 #endif 73 74 #define MAX_MEM_PREALLOC_THREAD_COUNT 16 75 76 struct MemsetThread { 77 char *addr; 78 size_t numpages; 79 size_t hpagesize; 80 QemuThread pgthread; 81 sigjmp_buf env; 82 }; 83 typedef struct MemsetThread MemsetThread; 84 85 static MemsetThread *memset_thread; 86 static int memset_num_threads; 87 static bool memset_thread_failed; 88 89 static QemuMutex page_mutex; 90 static QemuCond page_cond; 91 static bool threads_created_flag; 92 93 int qemu_get_thread_id(void) 94 { 95 #if defined(__linux__) 96 return syscall(SYS_gettid); 97 #elif defined(__FreeBSD__) 98 /* thread id is up to INT_MAX */ 99 long tid; 100 thr_self(&tid); 101 return (int)tid; 102 #elif defined(__NetBSD__) 103 return _lwp_self(); 104 #elif defined(__OpenBSD__) 105 return getthrid(); 106 #else 107 return getpid(); 108 #endif 109 } 110 111 int qemu_daemon(int nochdir, int noclose) 112 { 113 return daemon(nochdir, noclose); 114 } 115 116 bool qemu_write_pidfile(const char *path, Error **errp) 117 { 118 int fd; 119 char pidstr[32]; 120 121 while (1) { 122 struct stat a, b; 123 struct flock lock = { 124 .l_type = F_WRLCK, 125 .l_whence = SEEK_SET, 126 .l_len = 0, 127 }; 128 129 fd = qemu_open_old(path, O_CREAT | O_WRONLY, S_IRUSR | S_IWUSR); 130 if (fd == -1) { 131 error_setg_errno(errp, errno, "Cannot open pid file"); 132 return false; 133 } 134 135 if (fstat(fd, &b) < 0) { 136 error_setg_errno(errp, errno, "Cannot stat file"); 137 goto fail_close; 138 } 139 140 if (fcntl(fd, F_SETLK, &lock)) { 141 error_setg_errno(errp, errno, "Cannot lock pid file"); 142 goto fail_close; 143 } 144 145 /* 146 * Now make sure the path we locked is the same one that now 147 * exists on the filesystem. 148 */ 149 if (stat(path, &a) < 0) { 150 /* 151 * PID file disappeared, someone else must be racing with 152 * us, so try again. 153 */ 154 close(fd); 155 continue; 156 } 157 158 if (a.st_ino == b.st_ino) { 159 break; 160 } 161 162 /* 163 * PID file was recreated, someone else must be racing with 164 * us, so try again. 165 */ 166 close(fd); 167 } 168 169 if (ftruncate(fd, 0) < 0) { 170 error_setg_errno(errp, errno, "Failed to truncate pid file"); 171 goto fail_unlink; 172 } 173 174 snprintf(pidstr, sizeof(pidstr), FMT_pid "\n", getpid()); 175 if (write(fd, pidstr, strlen(pidstr)) != strlen(pidstr)) { 176 error_setg(errp, "Failed to write pid file"); 177 goto fail_unlink; 178 } 179 180 return true; 181 182 fail_unlink: 183 unlink(path); 184 fail_close: 185 close(fd); 186 return false; 187 } 188 189 void *qemu_oom_check(void *ptr) 190 { 191 if (ptr == NULL) { 192 fprintf(stderr, "Failed to allocate memory: %s\n", strerror(errno)); 193 abort(); 194 } 195 return ptr; 196 } 197 198 void *qemu_try_memalign(size_t alignment, size_t size) 199 { 200 void *ptr; 201 202 if (alignment < sizeof(void*)) { 203 alignment = sizeof(void*); 204 } else { 205 g_assert(is_power_of_2(alignment)); 206 } 207 208 #if defined(CONFIG_POSIX_MEMALIGN) 209 int ret; 210 ret = posix_memalign(&ptr, alignment, size); 211 if (ret != 0) { 212 errno = ret; 213 ptr = NULL; 214 } 215 #elif defined(CONFIG_BSD) 216 ptr = valloc(size); 217 #else 218 ptr = memalign(alignment, size); 219 #endif 220 trace_qemu_memalign(alignment, size, ptr); 221 return ptr; 222 } 223 224 void *qemu_memalign(size_t alignment, size_t size) 225 { 226 return qemu_oom_check(qemu_try_memalign(alignment, size)); 227 } 228 229 /* alloc shared memory pages */ 230 void *qemu_anon_ram_alloc(size_t size, uint64_t *alignment, bool shared) 231 { 232 size_t align = QEMU_VMALLOC_ALIGN; 233 void *ptr = qemu_ram_mmap(-1, size, align, shared, false); 234 235 if (ptr == MAP_FAILED) { 236 return NULL; 237 } 238 239 if (alignment) { 240 *alignment = align; 241 } 242 243 trace_qemu_anon_ram_alloc(size, ptr); 244 return ptr; 245 } 246 247 void qemu_vfree(void *ptr) 248 { 249 trace_qemu_vfree(ptr); 250 free(ptr); 251 } 252 253 void qemu_anon_ram_free(void *ptr, size_t size) 254 { 255 trace_qemu_anon_ram_free(ptr, size); 256 qemu_ram_munmap(-1, ptr, size); 257 } 258 259 void qemu_set_block(int fd) 260 { 261 int f; 262 f = fcntl(fd, F_GETFL); 263 assert(f != -1); 264 f = fcntl(fd, F_SETFL, f & ~O_NONBLOCK); 265 assert(f != -1); 266 } 267 268 int qemu_try_set_nonblock(int fd) 269 { 270 int f; 271 f = fcntl(fd, F_GETFL); 272 if (f == -1) { 273 return -errno; 274 } 275 if (fcntl(fd, F_SETFL, f | O_NONBLOCK) == -1) { 276 #ifdef __OpenBSD__ 277 /* 278 * Previous to OpenBSD 6.3, fcntl(F_SETFL) is not permitted on 279 * memory devices and sets errno to ENODEV. 280 * It's OK if we fail to set O_NONBLOCK on devices like /dev/null, 281 * because they will never block anyway. 282 */ 283 if (errno == ENODEV) { 284 return 0; 285 } 286 #endif 287 return -errno; 288 } 289 return 0; 290 } 291 292 void qemu_set_nonblock(int fd) 293 { 294 int f; 295 f = qemu_try_set_nonblock(fd); 296 assert(f == 0); 297 } 298 299 int socket_set_fast_reuse(int fd) 300 { 301 int val = 1, ret; 302 303 ret = setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, 304 (const char *)&val, sizeof(val)); 305 306 assert(ret == 0); 307 308 return ret; 309 } 310 311 void qemu_set_cloexec(int fd) 312 { 313 int f; 314 f = fcntl(fd, F_GETFD); 315 assert(f != -1); 316 f = fcntl(fd, F_SETFD, f | FD_CLOEXEC); 317 assert(f != -1); 318 } 319 320 /* 321 * Creates a pipe with FD_CLOEXEC set on both file descriptors 322 */ 323 int qemu_pipe(int pipefd[2]) 324 { 325 int ret; 326 327 #ifdef CONFIG_PIPE2 328 ret = pipe2(pipefd, O_CLOEXEC); 329 if (ret != -1 || errno != ENOSYS) { 330 return ret; 331 } 332 #endif 333 ret = pipe(pipefd); 334 if (ret == 0) { 335 qemu_set_cloexec(pipefd[0]); 336 qemu_set_cloexec(pipefd[1]); 337 } 338 339 return ret; 340 } 341 342 char * 343 qemu_get_local_state_pathname(const char *relative_pathname) 344 { 345 g_autofree char *dir = g_strdup_printf("%s/%s", 346 CONFIG_QEMU_LOCALSTATEDIR, 347 relative_pathname); 348 return get_relocated_path(dir); 349 } 350 351 void qemu_set_tty_echo(int fd, bool echo) 352 { 353 struct termios tty; 354 355 tcgetattr(fd, &tty); 356 357 if (echo) { 358 tty.c_lflag |= ECHO | ECHONL | ICANON | IEXTEN; 359 } else { 360 tty.c_lflag &= ~(ECHO | ECHONL | ICANON | IEXTEN); 361 } 362 363 tcsetattr(fd, TCSANOW, &tty); 364 } 365 366 static const char *exec_dir; 367 368 void qemu_init_exec_dir(const char *argv0) 369 { 370 char *p = NULL; 371 char buf[PATH_MAX]; 372 373 if (exec_dir) { 374 return; 375 } 376 377 #if defined(__linux__) 378 { 379 int len; 380 len = readlink("/proc/self/exe", buf, sizeof(buf) - 1); 381 if (len > 0) { 382 buf[len] = 0; 383 p = buf; 384 } 385 } 386 #elif defined(__FreeBSD__) \ 387 || (defined(__NetBSD__) && defined(KERN_PROC_PATHNAME)) 388 { 389 #if defined(__FreeBSD__) 390 static int mib[4] = {CTL_KERN, KERN_PROC, KERN_PROC_PATHNAME, -1}; 391 #else 392 static int mib[4] = {CTL_KERN, KERN_PROC_ARGS, -1, KERN_PROC_PATHNAME}; 393 #endif 394 size_t len = sizeof(buf) - 1; 395 396 *buf = '\0'; 397 if (!sysctl(mib, ARRAY_SIZE(mib), buf, &len, NULL, 0) && 398 *buf) { 399 buf[sizeof(buf) - 1] = '\0'; 400 p = buf; 401 } 402 } 403 #elif defined(__APPLE__) 404 { 405 char fpath[PATH_MAX]; 406 uint32_t len = sizeof(fpath); 407 if (_NSGetExecutablePath(fpath, &len) == 0) { 408 p = realpath(fpath, buf); 409 if (!p) { 410 return; 411 } 412 } 413 } 414 #elif defined(__HAIKU__) 415 { 416 image_info ii; 417 int32_t c = 0; 418 419 *buf = '\0'; 420 while (get_next_image_info(0, &c, &ii) == B_OK) { 421 if (ii.type == B_APP_IMAGE) { 422 strncpy(buf, ii.name, sizeof(buf)); 423 buf[sizeof(buf) - 1] = 0; 424 p = buf; 425 break; 426 } 427 } 428 } 429 #endif 430 /* If we don't have any way of figuring out the actual executable 431 location then try argv[0]. */ 432 if (!p && argv0) { 433 p = realpath(argv0, buf); 434 } 435 if (p) { 436 exec_dir = g_path_get_dirname(p); 437 } else { 438 exec_dir = CONFIG_BINDIR; 439 } 440 } 441 442 const char *qemu_get_exec_dir(void) 443 { 444 return exec_dir; 445 } 446 447 static void sigbus_handler(int signal) 448 { 449 int i; 450 if (memset_thread) { 451 for (i = 0; i < memset_num_threads; i++) { 452 if (qemu_thread_is_self(&memset_thread[i].pgthread)) { 453 siglongjmp(memset_thread[i].env, 1); 454 } 455 } 456 } 457 } 458 459 static void *do_touch_pages(void *arg) 460 { 461 MemsetThread *memset_args = (MemsetThread *)arg; 462 sigset_t set, oldset; 463 464 /* 465 * On Linux, the page faults from the loop below can cause mmap_sem 466 * contention with allocation of the thread stacks. Do not start 467 * clearing until all threads have been created. 468 */ 469 qemu_mutex_lock(&page_mutex); 470 while(!threads_created_flag){ 471 qemu_cond_wait(&page_cond, &page_mutex); 472 } 473 qemu_mutex_unlock(&page_mutex); 474 475 /* unblock SIGBUS */ 476 sigemptyset(&set); 477 sigaddset(&set, SIGBUS); 478 pthread_sigmask(SIG_UNBLOCK, &set, &oldset); 479 480 if (sigsetjmp(memset_args->env, 1)) { 481 memset_thread_failed = true; 482 } else { 483 char *addr = memset_args->addr; 484 size_t numpages = memset_args->numpages; 485 size_t hpagesize = memset_args->hpagesize; 486 size_t i; 487 for (i = 0; i < numpages; i++) { 488 /* 489 * Read & write back the same value, so we don't 490 * corrupt existing user/app data that might be 491 * stored. 492 * 493 * 'volatile' to stop compiler optimizing this away 494 * to a no-op 495 * 496 * TODO: get a better solution from kernel so we 497 * don't need to write at all so we don't cause 498 * wear on the storage backing the region... 499 */ 500 *(volatile char *)addr = *addr; 501 addr += hpagesize; 502 } 503 } 504 pthread_sigmask(SIG_SETMASK, &oldset, NULL); 505 return NULL; 506 } 507 508 static inline int get_memset_num_threads(int smp_cpus) 509 { 510 long host_procs = sysconf(_SC_NPROCESSORS_ONLN); 511 int ret = 1; 512 513 if (host_procs > 0) { 514 ret = MIN(MIN(host_procs, MAX_MEM_PREALLOC_THREAD_COUNT), smp_cpus); 515 } 516 /* In case sysconf() fails, we fall back to single threaded */ 517 return ret; 518 } 519 520 static bool touch_all_pages(char *area, size_t hpagesize, size_t numpages, 521 int smp_cpus) 522 { 523 static gsize initialized = 0; 524 size_t numpages_per_thread, leftover; 525 char *addr = area; 526 int i = 0; 527 528 if (g_once_init_enter(&initialized)) { 529 qemu_mutex_init(&page_mutex); 530 qemu_cond_init(&page_cond); 531 g_once_init_leave(&initialized, 1); 532 } 533 534 memset_thread_failed = false; 535 threads_created_flag = false; 536 memset_num_threads = get_memset_num_threads(smp_cpus); 537 memset_thread = g_new0(MemsetThread, memset_num_threads); 538 numpages_per_thread = numpages / memset_num_threads; 539 leftover = numpages % memset_num_threads; 540 for (i = 0; i < memset_num_threads; i++) { 541 memset_thread[i].addr = addr; 542 memset_thread[i].numpages = numpages_per_thread + (i < leftover); 543 memset_thread[i].hpagesize = hpagesize; 544 qemu_thread_create(&memset_thread[i].pgthread, "touch_pages", 545 do_touch_pages, &memset_thread[i], 546 QEMU_THREAD_JOINABLE); 547 addr += memset_thread[i].numpages * hpagesize; 548 } 549 550 qemu_mutex_lock(&page_mutex); 551 threads_created_flag = true; 552 qemu_cond_broadcast(&page_cond); 553 qemu_mutex_unlock(&page_mutex); 554 555 for (i = 0; i < memset_num_threads; i++) { 556 qemu_thread_join(&memset_thread[i].pgthread); 557 } 558 g_free(memset_thread); 559 memset_thread = NULL; 560 561 return memset_thread_failed; 562 } 563 564 void os_mem_prealloc(int fd, char *area, size_t memory, int smp_cpus, 565 Error **errp) 566 { 567 int ret; 568 struct sigaction act, oldact; 569 size_t hpagesize = qemu_fd_getpagesize(fd); 570 size_t numpages = DIV_ROUND_UP(memory, hpagesize); 571 572 memset(&act, 0, sizeof(act)); 573 act.sa_handler = &sigbus_handler; 574 act.sa_flags = 0; 575 576 ret = sigaction(SIGBUS, &act, &oldact); 577 if (ret) { 578 error_setg_errno(errp, errno, 579 "os_mem_prealloc: failed to install signal handler"); 580 return; 581 } 582 583 /* touch pages simultaneously */ 584 if (touch_all_pages(area, hpagesize, numpages, smp_cpus)) { 585 error_setg(errp, "os_mem_prealloc: Insufficient free host memory " 586 "pages available to allocate guest RAM"); 587 } 588 589 ret = sigaction(SIGBUS, &oldact, NULL); 590 if (ret) { 591 /* Terminate QEMU since it can't recover from error */ 592 perror("os_mem_prealloc: failed to reinstall signal handler"); 593 exit(1); 594 } 595 } 596 597 char *qemu_get_pid_name(pid_t pid) 598 { 599 char *name = NULL; 600 601 #if defined(__FreeBSD__) 602 /* BSDs don't have /proc, but they provide a nice substitute */ 603 struct kinfo_proc *proc = kinfo_getproc(pid); 604 605 if (proc) { 606 name = g_strdup(proc->ki_comm); 607 free(proc); 608 } 609 #else 610 /* Assume a system with reasonable procfs */ 611 char *pid_path; 612 size_t len; 613 614 pid_path = g_strdup_printf("/proc/%d/cmdline", pid); 615 g_file_get_contents(pid_path, &name, &len, NULL); 616 g_free(pid_path); 617 #endif 618 619 return name; 620 } 621 622 623 pid_t qemu_fork(Error **errp) 624 { 625 sigset_t oldmask, newmask; 626 struct sigaction sig_action; 627 int saved_errno; 628 pid_t pid; 629 630 /* 631 * Need to block signals now, so that child process can safely 632 * kill off caller's signal handlers without a race. 633 */ 634 sigfillset(&newmask); 635 if (pthread_sigmask(SIG_SETMASK, &newmask, &oldmask) != 0) { 636 error_setg_errno(errp, errno, 637 "cannot block signals"); 638 return -1; 639 } 640 641 pid = fork(); 642 saved_errno = errno; 643 644 if (pid < 0) { 645 /* attempt to restore signal mask, but ignore failure, to 646 * avoid obscuring the fork failure */ 647 (void)pthread_sigmask(SIG_SETMASK, &oldmask, NULL); 648 error_setg_errno(errp, saved_errno, 649 "cannot fork child process"); 650 errno = saved_errno; 651 return -1; 652 } else if (pid) { 653 /* parent process */ 654 655 /* Restore our original signal mask now that the child is 656 * safely running. Only documented failures are EFAULT (not 657 * possible, since we are using just-grabbed mask) or EINVAL 658 * (not possible, since we are using correct arguments). */ 659 (void)pthread_sigmask(SIG_SETMASK, &oldmask, NULL); 660 } else { 661 /* child process */ 662 size_t i; 663 664 /* Clear out all signal handlers from parent so nothing 665 * unexpected can happen in our child once we unblock 666 * signals */ 667 sig_action.sa_handler = SIG_DFL; 668 sig_action.sa_flags = 0; 669 sigemptyset(&sig_action.sa_mask); 670 671 for (i = 1; i < NSIG; i++) { 672 /* Only possible errors are EFAULT or EINVAL The former 673 * won't happen, the latter we expect, so no need to check 674 * return value */ 675 (void)sigaction(i, &sig_action, NULL); 676 } 677 678 /* Unmask all signals in child, since we've no idea what the 679 * caller's done with their signal mask and don't want to 680 * propagate that to children */ 681 sigemptyset(&newmask); 682 if (pthread_sigmask(SIG_SETMASK, &newmask, NULL) != 0) { 683 Error *local_err = NULL; 684 error_setg_errno(&local_err, errno, 685 "cannot unblock signals"); 686 error_report_err(local_err); 687 _exit(1); 688 } 689 } 690 return pid; 691 } 692 693 void *qemu_alloc_stack(size_t *sz) 694 { 695 void *ptr, *guardpage; 696 int flags; 697 #ifdef CONFIG_DEBUG_STACK_USAGE 698 void *ptr2; 699 #endif 700 size_t pagesz = qemu_real_host_page_size; 701 #ifdef _SC_THREAD_STACK_MIN 702 /* avoid stacks smaller than _SC_THREAD_STACK_MIN */ 703 long min_stack_sz = sysconf(_SC_THREAD_STACK_MIN); 704 *sz = MAX(MAX(min_stack_sz, 0), *sz); 705 #endif 706 /* adjust stack size to a multiple of the page size */ 707 *sz = ROUND_UP(*sz, pagesz); 708 /* allocate one extra page for the guard page */ 709 *sz += pagesz; 710 711 flags = MAP_PRIVATE | MAP_ANONYMOUS; 712 #if defined(MAP_STACK) && defined(__OpenBSD__) 713 /* Only enable MAP_STACK on OpenBSD. Other OS's such as 714 * Linux/FreeBSD/NetBSD have a flag with the same name 715 * but have differing functionality. OpenBSD will SEGV 716 * if it spots execution with a stack pointer pointing 717 * at memory that was not allocated with MAP_STACK. 718 */ 719 flags |= MAP_STACK; 720 #endif 721 722 ptr = mmap(NULL, *sz, PROT_READ | PROT_WRITE, flags, -1, 0); 723 if (ptr == MAP_FAILED) { 724 perror("failed to allocate memory for stack"); 725 abort(); 726 } 727 728 #if defined(HOST_IA64) 729 /* separate register stack */ 730 guardpage = ptr + (((*sz - pagesz) / 2) & ~pagesz); 731 #elif defined(HOST_HPPA) 732 /* stack grows up */ 733 guardpage = ptr + *sz - pagesz; 734 #else 735 /* stack grows down */ 736 guardpage = ptr; 737 #endif 738 if (mprotect(guardpage, pagesz, PROT_NONE) != 0) { 739 perror("failed to set up stack guard page"); 740 abort(); 741 } 742 743 #ifdef CONFIG_DEBUG_STACK_USAGE 744 for (ptr2 = ptr + pagesz; ptr2 < ptr + *sz; ptr2 += sizeof(uint32_t)) { 745 *(uint32_t *)ptr2 = 0xdeadbeaf; 746 } 747 #endif 748 749 return ptr; 750 } 751 752 #ifdef CONFIG_DEBUG_STACK_USAGE 753 static __thread unsigned int max_stack_usage; 754 #endif 755 756 void qemu_free_stack(void *stack, size_t sz) 757 { 758 #ifdef CONFIG_DEBUG_STACK_USAGE 759 unsigned int usage; 760 void *ptr; 761 762 for (ptr = stack + qemu_real_host_page_size; ptr < stack + sz; 763 ptr += sizeof(uint32_t)) { 764 if (*(uint32_t *)ptr != 0xdeadbeaf) { 765 break; 766 } 767 } 768 usage = sz - (uintptr_t) (ptr - stack); 769 if (usage > max_stack_usage) { 770 error_report("thread %d max stack usage increased from %u to %u", 771 qemu_get_thread_id(), max_stack_usage, usage); 772 max_stack_usage = usage; 773 } 774 #endif 775 776 munmap(stack, sz); 777 } 778 779 /* 780 * Disable CFI checks. 781 * We are going to call a signal hander directly. Such handler may or may not 782 * have been defined in our binary, so there's no guarantee that the pointer 783 * used to set the handler is a cfi-valid pointer. Since the handlers are 784 * stored in kernel memory, changing the handler to an attacker-defined 785 * function requires being able to call a sigaction() syscall, 786 * which is not as easy as overwriting a pointer in memory. 787 */ 788 QEMU_DISABLE_CFI 789 void sigaction_invoke(struct sigaction *action, 790 struct qemu_signalfd_siginfo *info) 791 { 792 siginfo_t si = {}; 793 si.si_signo = info->ssi_signo; 794 si.si_errno = info->ssi_errno; 795 si.si_code = info->ssi_code; 796 797 /* Convert the minimal set of fields defined by POSIX. 798 * Positive si_code values are reserved for kernel-generated 799 * signals, where the valid siginfo fields are determined by 800 * the signal number. But according to POSIX, it is unspecified 801 * whether SI_USER and SI_QUEUE have values less than or equal to 802 * zero. 803 */ 804 if (info->ssi_code == SI_USER || info->ssi_code == SI_QUEUE || 805 info->ssi_code <= 0) { 806 /* SIGTERM, etc. */ 807 si.si_pid = info->ssi_pid; 808 si.si_uid = info->ssi_uid; 809 } else if (info->ssi_signo == SIGILL || info->ssi_signo == SIGFPE || 810 info->ssi_signo == SIGSEGV || info->ssi_signo == SIGBUS) { 811 si.si_addr = (void *)(uintptr_t)info->ssi_addr; 812 } else if (info->ssi_signo == SIGCHLD) { 813 si.si_pid = info->ssi_pid; 814 si.si_status = info->ssi_status; 815 si.si_uid = info->ssi_uid; 816 } 817 action->sa_sigaction(info->ssi_signo, &si, NULL); 818 } 819 820 #ifndef HOST_NAME_MAX 821 # ifdef _POSIX_HOST_NAME_MAX 822 # define HOST_NAME_MAX _POSIX_HOST_NAME_MAX 823 # else 824 # define HOST_NAME_MAX 255 825 # endif 826 #endif 827 828 char *qemu_get_host_name(Error **errp) 829 { 830 long len = -1; 831 g_autofree char *hostname = NULL; 832 833 #ifdef _SC_HOST_NAME_MAX 834 len = sysconf(_SC_HOST_NAME_MAX); 835 #endif /* _SC_HOST_NAME_MAX */ 836 837 if (len < 0) { 838 len = HOST_NAME_MAX; 839 } 840 841 /* Unfortunately, gethostname() below does not guarantee a 842 * NULL terminated string. Therefore, allocate one byte more 843 * to be sure. */ 844 hostname = g_new0(char, len + 1); 845 846 if (gethostname(hostname, len) < 0) { 847 error_setg_errno(errp, errno, 848 "cannot get hostname"); 849 return NULL; 850 } 851 852 return g_steal_pointer(&hostname); 853 } 854 855 size_t qemu_get_host_physmem(void) 856 { 857 #ifdef _SC_PHYS_PAGES 858 long pages = sysconf(_SC_PHYS_PAGES); 859 if (pages > 0) { 860 if (pages > SIZE_MAX / qemu_real_host_page_size) { 861 return SIZE_MAX; 862 } else { 863 return pages * qemu_real_host_page_size; 864 } 865 } 866 #endif 867 return 0; 868 } 869