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 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 }