util/oslib-posix.c

   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
  88 static QemuMutex page_mutex;
  89 static QemuCond page_cond;
  90 static bool threads_created_flag;
  91
  92 int qemu_get_thread_id(void)
  93 {
  94 #if defined(__linux__)
  95     return syscall(SYS_gettid);
  96 #elif defined(__FreeBSD__)
  97     /* thread id is up to INT_MAX */
  98     long tid;
  99     thr_self(&tid);
 100     return (int)tid;
 101 #elif defined(__NetBSD__)
 102     return _lwp_self();
 103 #elif defined(__OpenBSD__)
 104     return getthrid();
 105 #else
 106     return getpid();
 107 #endif
 108 }
 109
 110 int qemu_daemon(int nochdir, int noclose)
 111 {
 112     return daemon(nochdir, noclose);
 113 }
 114
 115 bool qemu_write_pidfile(const char *path, Error **errp)
 116 {
 117     int fd;
 118     char pidstr[32];
 119
 120     while (1) {
 121         struct stat a, b;
 122         struct flock lock = {
 123             .l_type = F_WRLCK,
 124             .l_whence = SEEK_SET,
 125             .l_len = 0,
 126         };
 127
 128         fd = qemu_open_old(path, O_CREAT | O_WRONLY, S_IRUSR | S_IWUSR);
 129         if (fd == -1) {
 130             error_setg_errno(errp, errno, "Cannot open pid file");
 131             return false;
 132         }
 133
 134         if (fstat(fd, &b) < 0) {
 135             error_setg_errno(errp, errno, "Cannot stat file");
 136             goto fail_close;
 137         }
 138
 139         if (fcntl(fd, F_SETLK, &lock)) {
 140             error_setg_errno(errp, errno, "Cannot lock pid file");
 141             goto fail_close;
 142         }
 143
 144         /*
 145          * Now make sure the path we locked is the same one that now
 146          * exists on the filesystem.
 147          */
 148         if (stat(path, &a) < 0) {
 149             /*
 150              * PID file disappeared, someone else must be racing with
 151              * us, so try again.
 152              */
 153             close(fd);
 154             continue;
 155         }
 156
 157         if (a.st_ino == b.st_ino) {
 158             break;
 159         }
 160
 161         /*
 162          * PID file was recreated, someone else must be racing with
 163          * us, so try again.
 164          */
 165         close(fd);
 166     }
 167
 168     if (ftruncate(fd, 0) < 0) {
 169         error_setg_errno(errp, errno, "Failed to truncate pid file");
 170         goto fail_unlink;
 171     }
 172
 173     snprintf(pidstr, sizeof(pidstr), FMT_pid "\n", getpid());
 174     if (write(fd, pidstr, strlen(pidstr)) != strlen(pidstr)) {
 175         error_setg(errp, "Failed to write pid file");
 176         goto fail_unlink;
 177     }
 178
 179     return true;
 180
 181 fail_unlink:
 182     unlink(path);
 183 fail_close:
 184     close(fd);
 185     return false;
 186 }
 187
 188 void *qemu_oom_check(void *ptr)
 189 {
 190     if (ptr == NULL) {
 191         fprintf(stderr, "Failed to allocate memory: %s\n", strerror(errno));
 192         abort();
 193     }
 194     return ptr;
 195 }
 196
 197 void *qemu_try_memalign(size_t alignment, size_t size)
 198 {
 199     void *ptr;
 200
 201     if (alignment < sizeof(void*)) {
 202         alignment = sizeof(void*);
 203     } else {
 204         g_assert(is_power_of_2(alignment));
 205     }
 206
 207 #if defined(CONFIG_POSIX_MEMALIGN)
 208     int ret;
 209     ret = posix_memalign(&ptr, alignment, size);
 210     if (ret != 0) {
 211         errno = ret;
 212         ptr = NULL;
 213     }
 214 #elif defined(CONFIG_BSD)
 215     ptr = valloc(size);
 216 #else
 217     ptr = memalign(alignment, size);
 218 #endif
 219     trace_qemu_memalign(alignment, size, ptr);
 220     return ptr;
 221 }
 222
 223 void *qemu_memalign(size_t alignment, size_t size)
 224 {
 225     return qemu_oom_check(qemu_try_memalign(alignment, size));
 226 }
 227
 228 /* alloc shared memory pages */
 229 void *qemu_anon_ram_alloc(size_t size, uint64_t *alignment, bool shared,
 230                           bool noreserve)
 231 {
 232     const uint32_t qemu_map_flags = (shared ? QEMU_MAP_SHARED : 0) |
 233                                     (noreserve ? QEMU_MAP_NORESERVE : 0);
 234     size_t align = QEMU_VMALLOC_ALIGN;
 235     void *ptr = qemu_ram_mmap(-1, size, align, qemu_map_flags, 0);
 236
 237     if (ptr == MAP_FAILED) {
 238         return NULL;
 239     }
 240
 241     if (alignment) {
 242         *alignment = align;
 243     }
 244
 245     trace_qemu_anon_ram_alloc(size, ptr);
 246     return ptr;
 247 }
 248
 249 void qemu_vfree(void *ptr)
 250 {
 251     trace_qemu_vfree(ptr);
 252     free(ptr);
 253 }
 254
 255 void qemu_anon_ram_free(void *ptr, size_t size)
 256 {
 257     trace_qemu_anon_ram_free(ptr, size);
 258     qemu_ram_munmap(-1, ptr, size);
 259 }
 260
 261 void qemu_set_block(int fd)
 262 {
 263     int f;
 264     f = fcntl(fd, F_GETFL);
 265     assert(f != -1);
 266     f = fcntl(fd, F_SETFL, f & ~O_NONBLOCK);
 267     assert(f != -1);
 268 }
 269
 270 int qemu_try_set_nonblock(int fd)
 271 {
 272     int f;
 273     f = fcntl(fd, F_GETFL);
 274     if (f == -1) {
 275         return -errno;
 276     }
 277     if (fcntl(fd, F_SETFL, f | O_NONBLOCK) == -1) {
 278         return -errno;
 279     }
 280     return 0;
 281 }
 282
 283 void qemu_set_nonblock(int fd)
 284 {
 285     int f;
 286     f = qemu_try_set_nonblock(fd);
 287     assert(f == 0);
 288 }
 289
 290 int socket_set_fast_reuse(int fd)
 291 {
 292     int val = 1, ret;
 293
 294     ret = setsockopt(fd, SOL_SOCKET, SO_REUSEADDR,
 295                      (const char *)&val, sizeof(val));
 296
 297     assert(ret == 0);
 298
 299     return ret;
 300 }
 301
 302 void qemu_set_cloexec(int fd)
 303 {
 304     int f;
 305     f = fcntl(fd, F_GETFD);
 306     assert(f != -1);
 307     f = fcntl(fd, F_SETFD, f | FD_CLOEXEC);
 308     assert(f != -1);
 309 }
 310
 311 /*
 312  * Creates a pipe with FD_CLOEXEC set on both file descriptors
 313  */
 314 int qemu_pipe(int pipefd[2])
 315 {
 316     int ret;
 317
 318 #ifdef CONFIG_PIPE2
 319     ret = pipe2(pipefd, O_CLOEXEC);
 320     if (ret != -1 || errno != ENOSYS) {
 321         return ret;
 322     }
 323 #endif
 324     ret = pipe(pipefd);
 325     if (ret == 0) {
 326         qemu_set_cloexec(pipefd[0]);
 327         qemu_set_cloexec(pipefd[1]);
 328     }
 329
 330     return ret;
 331 }
 332
 333 char *
 334 qemu_get_local_state_pathname(const char *relative_pathname)
 335 {
 336     g_autofree char *dir = g_strdup_printf("%s/%s",
 337                                            CONFIG_QEMU_LOCALSTATEDIR,
 338                                            relative_pathname);
 339     return get_relocated_path(dir);
 340 }
 341
 342 void qemu_set_tty_echo(int fd, bool echo)
 343 {
 344     struct termios tty;
 345
 346     tcgetattr(fd, &tty);
 347
 348     if (echo) {
 349         tty.c_lflag |= ECHO | ECHONL | ICANON | IEXTEN;
 350     } else {
 351         tty.c_lflag &= ~(ECHO | ECHONL | ICANON | IEXTEN);
 352     }
 353
 354     tcsetattr(fd, TCSANOW, &tty);
 355 }
 356
 357 static const char *exec_dir;
 358
 359 void qemu_init_exec_dir(const char *argv0)
 360 {
 361     char *p = NULL;
 362     char buf[PATH_MAX];
 363
 364     if (exec_dir) {
 365         return;
 366     }
 367
 368 #if defined(__linux__)
 369     {
 370         int len;
 371         len = readlink("/proc/self/exe", buf, sizeof(buf) - 1);
 372         if (len > 0) {
 373             buf[len] = 0;
 374             p = buf;
 375         }
 376     }
 377 #elif defined(__FreeBSD__) \
 378       || (defined(__NetBSD__) && defined(KERN_PROC_PATHNAME))
 379     {
 380 #if defined(__FreeBSD__)
 381         static int mib[4] = {CTL_KERN, KERN_PROC, KERN_PROC_PATHNAME, -1};
 382 #else
 383         static int mib[4] = {CTL_KERN, KERN_PROC_ARGS, -1, KERN_PROC_PATHNAME};
 384 #endif
 385         size_t len = sizeof(buf) - 1;
 386
 387         *buf = '\0';
 388         if (!sysctl(mib, ARRAY_SIZE(mib), buf, &len, NULL, 0) &&
 389             *buf) {
 390             buf[sizeof(buf) - 1] = '\0';
 391             p = buf;
 392         }
 393     }
 394 #elif defined(__APPLE__)
 395     {
 396         char fpath[PATH_MAX];
 397         uint32_t len = sizeof(fpath);
 398         if (_NSGetExecutablePath(fpath, &len) == 0) {
 399             p = realpath(fpath, buf);
 400             if (!p) {
 401                 return;
 402             }
 403         }
 404     }
 405 #elif defined(__HAIKU__)
 406     {
 407         image_info ii;
 408         int32_t c = 0;
 409
 410         *buf = '\0';
 411         while (get_next_image_info(0, &c, &ii) == B_OK) {
 412             if (ii.type == B_APP_IMAGE) {
 413                 strncpy(buf, ii.name, sizeof(buf));
 414                 buf[sizeof(buf) - 1] = 0;
 415                 p = buf;
 416                 break;
 417             }
 418         }
 419     }
 420 #endif
 421     /* If we don't have any way of figuring out the actual executable
 422        location then try argv[0].  */
 423     if (!p && argv0) {
 424         p = realpath(argv0, buf);
 425     }
 426     if (p) {
 427         exec_dir = g_path_get_dirname(p);
 428     } else {
 429         exec_dir = CONFIG_BINDIR;
 430     }
 431 }
 432
 433 const char *qemu_get_exec_dir(void)
 434 {
 435     return exec_dir;
 436 }
 437
 438 static void sigbus_handler(int signal)
 439 {
 440     int i;
 441     if (memset_thread) {
 442         for (i = 0; i < memset_num_threads; i++) {
 443             if (qemu_thread_is_self(&memset_thread[i].pgthread)) {
 444                 siglongjmp(memset_thread[i].env, 1);
 445             }
 446         }
 447     }
 448 }
 449
 450 static void *do_touch_pages(void *arg)
 451 {
 452     MemsetThread *memset_args = (MemsetThread *)arg;
 453     sigset_t set, oldset;
 454     int ret = 0;
 455
 456     /*
 457      * On Linux, the page faults from the loop below can cause mmap_sem
 458      * contention with allocation of the thread stacks.  Do not start
 459      * clearing until all threads have been created.
 460      */
 461     qemu_mutex_lock(&page_mutex);
 462     while(!threads_created_flag){
 463         qemu_cond_wait(&page_cond, &page_mutex);
 464     }
 465     qemu_mutex_unlock(&page_mutex);
 466
 467     /* unblock SIGBUS */
 468     sigemptyset(&set);
 469     sigaddset(&set, SIGBUS);
 470     pthread_sigmask(SIG_UNBLOCK, &set, &oldset);
 471
 472     if (sigsetjmp(memset_args->env, 1)) {
 473         ret = -EFAULT;
 474     } else {
 475         char *addr = memset_args->addr;
 476         size_t numpages = memset_args->numpages;
 477         size_t hpagesize = memset_args->hpagesize;
 478         size_t i;
 479         for (i = 0; i < numpages; i++) {
 480             /*
 481              * Read & write back the same value, so we don't
 482              * corrupt existing user/app data that might be
 483              * stored.
 484              *
 485              * 'volatile' to stop compiler optimizing this away
 486              * to a no-op
 487              */
 488             *(volatile char *)addr = *addr;
 489             addr += hpagesize;
 490         }
 491     }
 492     pthread_sigmask(SIG_SETMASK, &oldset, NULL);
 493     return (void *)(uintptr_t)ret;
 494 }
 495
 496 static void *do_madv_populate_write_pages(void *arg)
 497 {
 498     MemsetThread *memset_args = (MemsetThread *)arg;
 499     const size_t size = memset_args->numpages * memset_args->hpagesize;
 500     char * const addr = memset_args->addr;
 501     int ret = 0;
 502
 503     /* See do_touch_pages(). */
 504     qemu_mutex_lock(&page_mutex);
 505     while (!threads_created_flag) {
 506         qemu_cond_wait(&page_cond, &page_mutex);
 507     }
 508     qemu_mutex_unlock(&page_mutex);
 509
 510     if (size && qemu_madvise(addr, size, QEMU_MADV_POPULATE_WRITE)) {
 511         ret = -errno;
 512     }
 513     return (void *)(uintptr_t)ret;
 514 }
 515
 516 static inline int get_memset_num_threads(int smp_cpus)
 517 {
 518     long host_procs = sysconf(_SC_NPROCESSORS_ONLN);
 519     int ret = 1;
 520
 521     if (host_procs > 0) {
 522         ret = MIN(MIN(host_procs, MAX_MEM_PREALLOC_THREAD_COUNT), smp_cpus);
 523     }
 524     /* In case sysconf() fails, we fall back to single threaded */
 525     return ret;
 526 }
 527
 528 static int touch_all_pages(char *area, size_t hpagesize, size_t numpages,
 529                            int smp_cpus, bool use_madv_populate_write)
 530 {
 531     static gsize initialized = 0;
 532     size_t numpages_per_thread, leftover;
 533     void *(*touch_fn)(void *);
 534     int ret = 0, i = 0;
 535     char *addr = area;
 536
 537     if (g_once_init_enter(&initialized)) {
 538         qemu_mutex_init(&page_mutex);
 539         qemu_cond_init(&page_cond);
 540         g_once_init_leave(&initialized, 1);
 541     }
 542
 543     if (use_madv_populate_write) {
 544         touch_fn = do_madv_populate_write_pages;
 545     } else {
 546         touch_fn = do_touch_pages;
 547     }
 548
 549     threads_created_flag = false;
 550     memset_num_threads = get_memset_num_threads(smp_cpus);
 551     memset_thread = g_new0(MemsetThread, memset_num_threads);
 552     numpages_per_thread = numpages / memset_num_threads;
 553     leftover = numpages % memset_num_threads;
 554     for (i = 0; i < memset_num_threads; i++) {
 555         memset_thread[i].addr = addr;
 556         memset_thread[i].numpages = numpages_per_thread + (i < leftover);
 557         memset_thread[i].hpagesize = hpagesize;
 558         qemu_thread_create(&memset_thread[i].pgthread, "touch_pages",
 559                            touch_fn, &memset_thread[i],
 560                            QEMU_THREAD_JOINABLE);
 561         addr += memset_thread[i].numpages * hpagesize;
 562     }
 563
 564     qemu_mutex_lock(&page_mutex);
 565     threads_created_flag = true;
 566     qemu_cond_broadcast(&page_cond);
 567     qemu_mutex_unlock(&page_mutex);
 568
 569     for (i = 0; i < memset_num_threads; i++) {
 570         int tmp = (uintptr_t)qemu_thread_join(&memset_thread[i].pgthread);
 571
 572         if (tmp) {
 573             ret = tmp;
 574         }
 575     }
 576     g_free(memset_thread);
 577     memset_thread = NULL;
 578
 579     return ret;
 580 }
 581
 582 static bool madv_populate_write_possible(char *area, size_t pagesize)
 583 {
 584     return !qemu_madvise(area, pagesize, QEMU_MADV_POPULATE_WRITE) ||
 585            errno != EINVAL;
 586 }
 587
 588 void os_mem_prealloc(int fd, char *area, size_t memory, int smp_cpus,
 589                      Error **errp)
 590 {
 591     int ret;
 592     struct sigaction act, oldact;
 593     size_t hpagesize = qemu_fd_getpagesize(fd);
 594     size_t numpages = DIV_ROUND_UP(memory, hpagesize);
 595     bool use_madv_populate_write;
 596
 597     /*
 598      * Sense on every invocation, as MADV_POPULATE_WRITE cannot be used for
 599      * some special mappings, such as mapping /dev/mem.
 600      */
 601     use_madv_populate_write = madv_populate_write_possible(area, hpagesize);
 602
 603     if (!use_madv_populate_write) {
 604         memset(&act, 0, sizeof(act));
 605         act.sa_handler = &sigbus_handler;
 606         act.sa_flags = 0;
 607
 608         ret = sigaction(SIGBUS, &act, &oldact);
 609         if (ret) {
 610             error_setg_errno(errp, errno,
 611                 "os_mem_prealloc: failed to install signal handler");
 612             return;
 613         }
 614     }
 615
 616     /* touch pages simultaneously */
 617     ret = touch_all_pages(area, hpagesize, numpages, smp_cpus,
 618                           use_madv_populate_write);
 619     if (ret) {
 620         error_setg_errno(errp, -ret,
 621                          "os_mem_prealloc: preallocating memory failed");
 622     }
 623
 624     if (!use_madv_populate_write) {
 625         ret = sigaction(SIGBUS, &oldact, NULL);
 626         if (ret) {
 627             /* Terminate QEMU since it can't recover from error */
 628             perror("os_mem_prealloc: failed to reinstall signal handler");
 629             exit(1);
 630         }
 631     }
 632 }
 633
 634 char *qemu_get_pid_name(pid_t pid)
 635 {
 636     char *name = NULL;
 637
 638 #if defined(__FreeBSD__)
 639     /* BSDs don't have /proc, but they provide a nice substitute */
 640     struct kinfo_proc *proc = kinfo_getproc(pid);
 641
 642     if (proc) {
 643         name = g_strdup(proc->ki_comm);
 644         free(proc);
 645     }
 646 #else
 647     /* Assume a system with reasonable procfs */
 648     char *pid_path;
 649     size_t len;
 650
 651     pid_path = g_strdup_printf("/proc/%d/cmdline", pid);
 652     g_file_get_contents(pid_path, &name, &len, NULL);
 653     g_free(pid_path);
 654 #endif
 655
 656     return name;
 657 }
 658
 659
 660 pid_t qemu_fork(Error **errp)
 661 {
 662     sigset_t oldmask, newmask;
 663     struct sigaction sig_action;
 664     int saved_errno;
 665     pid_t pid;
 666
 667     /*
 668      * Need to block signals now, so that child process can safely
 669      * kill off caller's signal handlers without a race.
 670      */
 671     sigfillset(&newmask);
 672     if (pthread_sigmask(SIG_SETMASK, &newmask, &oldmask) != 0) {
 673         error_setg_errno(errp, errno,
 674                          "cannot block signals");
 675         return -1;
 676     }
 677
 678     pid = fork();
 679     saved_errno = errno;
 680
 681     if (pid < 0) {
 682         /* attempt to restore signal mask, but ignore failure, to
 683          * avoid obscuring the fork failure */
 684         (void)pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
 685         error_setg_errno(errp, saved_errno,
 686                          "cannot fork child process");
 687         errno = saved_errno;
 688         return -1;
 689     } else if (pid) {
 690         /* parent process */
 691
 692         /* Restore our original signal mask now that the child is
 693          * safely running. Only documented failures are EFAULT (not
 694          * possible, since we are using just-grabbed mask) or EINVAL
 695          * (not possible, since we are using correct arguments).  */
 696         (void)pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
 697     } else {
 698         /* child process */
 699         size_t i;
 700
 701         /* Clear out all signal handlers from parent so nothing
 702          * unexpected can happen in our child once we unblock
 703          * signals */
 704         sig_action.sa_handler = SIG_DFL;
 705         sig_action.sa_flags = 0;
 706         sigemptyset(&sig_action.sa_mask);
 707
 708         for (i = 1; i < NSIG; i++) {
 709             /* Only possible errors are EFAULT or EINVAL The former
 710              * won't happen, the latter we expect, so no need to check
 711              * return value */
 712             (void)sigaction(i, &sig_action, NULL);
 713         }
 714
 715         /* Unmask all signals in child, since we've no idea what the
 716          * caller's done with their signal mask and don't want to
 717          * propagate that to children */
 718         sigemptyset(&newmask);
 719         if (pthread_sigmask(SIG_SETMASK, &newmask, NULL) != 0) {
 720             Error *local_err = NULL;
 721             error_setg_errno(&local_err, errno,
 722                              "cannot unblock signals");
 723             error_report_err(local_err);
 724             _exit(1);
 725         }
 726     }
 727     return pid;
 728 }
 729
 730 void *qemu_alloc_stack(size_t *sz)
 731 {
 732     void *ptr, *guardpage;
 733     int flags;
 734 #ifdef CONFIG_DEBUG_STACK_USAGE
 735     void *ptr2;
 736 #endif
 737     size_t pagesz = qemu_real_host_page_size;
 738 #ifdef _SC_THREAD_STACK_MIN
 739     /* avoid stacks smaller than _SC_THREAD_STACK_MIN */
 740     long min_stack_sz = sysconf(_SC_THREAD_STACK_MIN);
 741     *sz = MAX(MAX(min_stack_sz, 0), *sz);
 742 #endif
 743     /* adjust stack size to a multiple of the page size */
 744     *sz = ROUND_UP(*sz, pagesz);
 745     /* allocate one extra page for the guard page */
 746     *sz += pagesz;
 747
 748     flags = MAP_PRIVATE | MAP_ANONYMOUS;
 749 #if defined(MAP_STACK) && defined(__OpenBSD__)
 750     /* Only enable MAP_STACK on OpenBSD. Other OS's such as
 751      * Linux/FreeBSD/NetBSD have a flag with the same name
 752      * but have differing functionality. OpenBSD will SEGV
 753      * if it spots execution with a stack pointer pointing
 754      * at memory that was not allocated with MAP_STACK.
 755      */
 756     flags |= MAP_STACK;
 757 #endif
 758
 759     ptr = mmap(NULL, *sz, PROT_READ | PROT_WRITE, flags, -1, 0);
 760     if (ptr == MAP_FAILED) {
 761         perror("failed to allocate memory for stack");
 762         abort();
 763     }
 764
 765 #if defined(HOST_IA64)
 766     /* separate register stack */
 767     guardpage = ptr + (((*sz - pagesz) / 2) & ~pagesz);
 768 #elif defined(HOST_HPPA)
 769     /* stack grows up */
 770     guardpage = ptr + *sz - pagesz;
 771 #else
 772     /* stack grows down */
 773     guardpage = ptr;
 774 #endif
 775     if (mprotect(guardpage, pagesz, PROT_NONE) != 0) {
 776         perror("failed to set up stack guard page");
 777         abort();
 778     }
 779
 780 #ifdef CONFIG_DEBUG_STACK_USAGE
 781     for (ptr2 = ptr + pagesz; ptr2 < ptr + *sz; ptr2 += sizeof(uint32_t)) {
 782         *(uint32_t *)ptr2 = 0xdeadbeaf;
 783     }
 784 #endif
 785
 786     return ptr;
 787 }
 788
 789 #ifdef CONFIG_DEBUG_STACK_USAGE
 790 static __thread unsigned int max_stack_usage;
 791 #endif
 792
 793 void qemu_free_stack(void *stack, size_t sz)
 794 {
 795 #ifdef CONFIG_DEBUG_STACK_USAGE
 796     unsigned int usage;
 797     void *ptr;
 798
 799     for (ptr = stack + qemu_real_host_page_size; ptr < stack + sz;
 800          ptr += sizeof(uint32_t)) {
 801         if (*(uint32_t *)ptr != 0xdeadbeaf) {
 802             break;
 803         }
 804     }
 805     usage = sz - (uintptr_t) (ptr - stack);
 806     if (usage > max_stack_usage) {
 807         error_report("thread %d max stack usage increased from %u to %u",
 808                      qemu_get_thread_id(), max_stack_usage, usage);
 809         max_stack_usage = usage;
 810     }
 811 #endif
 812
 813     munmap(stack, sz);
 814 }
 815
 816 /*
 817  * Disable CFI checks.
 818  * We are going to call a signal hander directly. Such handler may or may not
 819  * have been defined in our binary, so there's no guarantee that the pointer
 820  * used to set the handler is a cfi-valid pointer. Since the handlers are
 821  * stored in kernel memory, changing the handler to an attacker-defined
 822  * function requires being able to call a sigaction() syscall,
 823  * which is not as easy as overwriting a pointer in memory.
 824  */
 825 QEMU_DISABLE_CFI
 826 void sigaction_invoke(struct sigaction *action,
 827                       struct qemu_signalfd_siginfo *info)
 828 {
 829     siginfo_t si = {};
 830     si.si_signo = info->ssi_signo;
 831     si.si_errno = info->ssi_errno;
 832     si.si_code = info->ssi_code;
 833
 834     /* Convert the minimal set of fields defined by POSIX.
 835      * Positive si_code values are reserved for kernel-generated
 836      * signals, where the valid siginfo fields are determined by
 837      * the signal number.  But according to POSIX, it is unspecified
 838      * whether SI_USER and SI_QUEUE have values less than or equal to
 839      * zero.
 840      */
 841     if (info->ssi_code == SI_USER || info->ssi_code == SI_QUEUE ||
 842         info->ssi_code <= 0) {
 843         /* SIGTERM, etc.  */
 844         si.si_pid = info->ssi_pid;
 845         si.si_uid = info->ssi_uid;
 846     } else if (info->ssi_signo == SIGILL || info->ssi_signo == SIGFPE ||
 847                info->ssi_signo == SIGSEGV || info->ssi_signo == SIGBUS) {
 848         si.si_addr = (void *)(uintptr_t)info->ssi_addr;
 849     } else if (info->ssi_signo == SIGCHLD) {
 850         si.si_pid = info->ssi_pid;
 851         si.si_status = info->ssi_status;
 852         si.si_uid = info->ssi_uid;
 853     }
 854     action->sa_sigaction(info->ssi_signo, &si, NULL);
 855 }
 856
 857 #ifndef HOST_NAME_MAX
 858 # ifdef _POSIX_HOST_NAME_MAX
 859 #  define HOST_NAME_MAX _POSIX_HOST_NAME_MAX
 860 # else
 861 #  define HOST_NAME_MAX 255
 862 # endif
 863 #endif
 864
 865 char *qemu_get_host_name(Error **errp)
 866 {
 867     long len = -1;
 868     g_autofree char *hostname = NULL;
 869
 870 #ifdef _SC_HOST_NAME_MAX
 871     len = sysconf(_SC_HOST_NAME_MAX);
 872 #endif /* _SC_HOST_NAME_MAX */
 873
 874     if (len < 0) {
 875         len = HOST_NAME_MAX;
 876     }
 877
 878     /* Unfortunately, gethostname() below does not guarantee a
 879      * NULL terminated string. Therefore, allocate one byte more
 880      * to be sure. */
 881     hostname = g_new0(char, len + 1);
 882
 883     if (gethostname(hostname, len) < 0) {
 884         error_setg_errno(errp, errno,
 885                          "cannot get hostname");
 886         return NULL;
 887     }
 888
 889     return g_steal_pointer(&hostname);
 890 }
 891
 892 size_t qemu_get_host_physmem(void)
 893 {
 894 #ifdef _SC_PHYS_PAGES
 895     long pages = sysconf(_SC_PHYS_PAGES);
 896     if (pages > 0) {
 897         if (pages > SIZE_MAX / qemu_real_host_page_size) {
 898             return SIZE_MAX;
 899         } else {
 900             return pages * qemu_real_host_page_size;
 901         }
 902     }
 903 #endif
 904     return 0;
 905 }