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/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 void *qemu_oom_check(void *ptr)
 203 {
 204     if (ptr == NULL) {
 205         fprintf(stderr, "Failed to allocate memory: %s\n", strerror(errno));
 206         abort();
 207     }
 208     return ptr;
 209 }
 210
 211 void *qemu_try_memalign(size_t alignment, size_t size)
 212 {
 213     void *ptr;
 214
 215     if (alignment < sizeof(void*)) {
 216         alignment = sizeof(void*);
 217     } else {
 218         g_assert(is_power_of_2(alignment));
 219     }
 220
 221 #if defined(CONFIG_POSIX_MEMALIGN)
 222     int ret;
 223     ret = posix_memalign(&ptr, alignment, size);
 224     if (ret != 0) {
 225         errno = ret;
 226         ptr = NULL;
 227     }
 228 #elif defined(CONFIG_BSD)
 229     ptr = valloc(size);
 230 #else
 231     ptr = memalign(alignment, size);
 232 #endif
 233     trace_qemu_memalign(alignment, size, ptr);
 234     return ptr;
 235 }
 236
 237 void *qemu_memalign(size_t alignment, size_t size)
 238 {
 239     return qemu_oom_check(qemu_try_memalign(alignment, size));
 240 }
 241
 242 /* alloc shared memory pages */
 243 void *qemu_anon_ram_alloc(size_t size, uint64_t *alignment, bool shared,
 244                           bool noreserve)
 245 {
 246     const uint32_t qemu_map_flags = (shared ? QEMU_MAP_SHARED : 0) |
 247                                     (noreserve ? QEMU_MAP_NORESERVE : 0);
 248     size_t align = QEMU_VMALLOC_ALIGN;
 249     void *ptr = qemu_ram_mmap(-1, size, align, qemu_map_flags, 0);
 250
 251     if (ptr == MAP_FAILED) {
 252         return NULL;
 253     }
 254
 255     if (alignment) {
 256         *alignment = align;
 257     }
 258
 259     trace_qemu_anon_ram_alloc(size, ptr);
 260     return ptr;
 261 }
 262
 263 void qemu_vfree(void *ptr)
 264 {
 265     trace_qemu_vfree(ptr);
 266     free(ptr);
 267 }
 268
 269 void qemu_anon_ram_free(void *ptr, size_t size)
 270 {
 271     trace_qemu_anon_ram_free(ptr, size);
 272     qemu_ram_munmap(-1, ptr, size);
 273 }
 274
 275 void qemu_set_block(int fd)
 276 {
 277     int f;
 278     f = fcntl(fd, F_GETFL);
 279     assert(f != -1);
 280     f = fcntl(fd, F_SETFL, f & ~O_NONBLOCK);
 281     assert(f != -1);
 282 }
 283
 284 int qemu_try_set_nonblock(int fd)
 285 {
 286     int f;
 287     f = fcntl(fd, F_GETFL);
 288     if (f == -1) {
 289         return -errno;
 290     }
 291     if (fcntl(fd, F_SETFL, f | O_NONBLOCK) == -1) {
 292         return -errno;
 293     }
 294     return 0;
 295 }
 296
 297 void qemu_set_nonblock(int fd)
 298 {
 299     int f;
 300     f = qemu_try_set_nonblock(fd);
 301     assert(f == 0);
 302 }
 303
 304 int socket_set_fast_reuse(int fd)
 305 {
 306     int val = 1, ret;
 307
 308     ret = setsockopt(fd, SOL_SOCKET, SO_REUSEADDR,
 309                      (const char *)&val, sizeof(val));
 310
 311     assert(ret == 0);
 312
 313     return ret;
 314 }
 315
 316 void qemu_set_cloexec(int fd)
 317 {
 318     int f;
 319     f = fcntl(fd, F_GETFD);
 320     assert(f != -1);
 321     f = fcntl(fd, F_SETFD, f | FD_CLOEXEC);
 322     assert(f != -1);
 323 }
 324
 325 /*
 326  * Creates a pipe with FD_CLOEXEC set on both file descriptors
 327  */
 328 int qemu_pipe(int pipefd[2])
 329 {
 330     int ret;
 331
 332 #ifdef CONFIG_PIPE2
 333     ret = pipe2(pipefd, O_CLOEXEC);
 334     if (ret != -1 || errno != ENOSYS) {
 335         return ret;
 336     }
 337 #endif
 338     ret = pipe(pipefd);
 339     if (ret == 0) {
 340         qemu_set_cloexec(pipefd[0]);
 341         qemu_set_cloexec(pipefd[1]);
 342     }
 343
 344     return ret;
 345 }
 346
 347 char *
 348 qemu_get_local_state_pathname(const char *relative_pathname)
 349 {
 350     g_autofree char *dir = g_strdup_printf("%s/%s",
 351                                            CONFIG_QEMU_LOCALSTATEDIR,
 352                                            relative_pathname);
 353     return get_relocated_path(dir);
 354 }
 355
 356 void qemu_set_tty_echo(int fd, bool echo)
 357 {
 358     struct termios tty;
 359
 360     tcgetattr(fd, &tty);
 361
 362     if (echo) {
 363         tty.c_lflag |= ECHO | ECHONL | ICANON | IEXTEN;
 364     } else {
 365         tty.c_lflag &= ~(ECHO | ECHONL | ICANON | IEXTEN);
 366     }
 367
 368     tcsetattr(fd, TCSANOW, &tty);
 369 }
 370
 371 static const char *exec_dir;
 372
 373 void qemu_init_exec_dir(const char *argv0)
 374 {
 375     char *p = NULL;
 376     char buf[PATH_MAX];
 377
 378     if (exec_dir) {
 379         return;
 380     }
 381
 382 #if defined(__linux__)
 383     {
 384         int len;
 385         len = readlink("/proc/self/exe", buf, sizeof(buf) - 1);
 386         if (len > 0) {
 387             buf[len] = 0;
 388             p = buf;
 389         }
 390     }
 391 #elif defined(__FreeBSD__) \
 392       || (defined(__NetBSD__) && defined(KERN_PROC_PATHNAME))
 393     {
 394 #if defined(__FreeBSD__)
 395         static int mib[4] = {CTL_KERN, KERN_PROC, KERN_PROC_PATHNAME, -1};
 396 #else
 397         static int mib[4] = {CTL_KERN, KERN_PROC_ARGS, -1, KERN_PROC_PATHNAME};
 398 #endif
 399         size_t len = sizeof(buf) - 1;
 400
 401         *buf = '\0';
 402         if (!sysctl(mib, ARRAY_SIZE(mib), buf, &len, NULL, 0) &&
 403             *buf) {
 404             buf[sizeof(buf) - 1] = '\0';
 405             p = buf;
 406         }
 407     }
 408 #elif defined(__APPLE__)
 409     {
 410         char fpath[PATH_MAX];
 411         uint32_t len = sizeof(fpath);
 412         if (_NSGetExecutablePath(fpath, &len) == 0) {
 413             p = realpath(fpath, buf);
 414             if (!p) {
 415                 return;
 416             }
 417         }
 418     }
 419 #elif defined(__HAIKU__)
 420     {
 421         image_info ii;
 422         int32_t c = 0;
 423
 424         *buf = '\0';
 425         while (get_next_image_info(0, &c, &ii) == B_OK) {
 426             if (ii.type == B_APP_IMAGE) {
 427                 strncpy(buf, ii.name, sizeof(buf));
 428                 buf[sizeof(buf) - 1] = 0;
 429                 p = buf;
 430                 break;
 431             }
 432         }
 433     }
 434 #endif
 435     /* If we don't have any way of figuring out the actual executable
 436        location then try argv[0].  */
 437     if (!p && argv0) {
 438         p = realpath(argv0, buf);
 439     }
 440     if (p) {
 441         exec_dir = g_path_get_dirname(p);
 442     } else {
 443         exec_dir = CONFIG_BINDIR;
 444     }
 445 }
 446
 447 const char *qemu_get_exec_dir(void)
 448 {
 449     return exec_dir;
 450 }
 451
 452 #ifdef CONFIG_LINUX
 453 static void sigbus_handler(int signal, siginfo_t *siginfo, void *ctx)
 454 #else /* CONFIG_LINUX */
 455 static void sigbus_handler(int signal)
 456 #endif /* CONFIG_LINUX */
 457 {
 458     int i;
 459
 460     if (sigbus_memset_context) {
 461         for (i = 0; i < sigbus_memset_context->num_threads; i++) {
 462             MemsetThread *thread = &sigbus_memset_context->threads[i];
 463
 464             if (qemu_thread_is_self(&thread->pgthread)) {
 465                 siglongjmp(thread->env, 1);
 466             }
 467         }
 468     }
 469
 470 #ifdef CONFIG_LINUX
 471     /*
 472      * We assume that the MCE SIGBUS handler could have been registered. We
 473      * should never receive BUS_MCEERR_AO on any of our threads, but only on
 474      * the main thread registered for PR_MCE_KILL_EARLY. Further, we should not
 475      * receive BUS_MCEERR_AR triggered by action of other threads on one of
 476      * our threads. So, no need to check for unrelated SIGBUS when seeing one
 477      * for our threads.
 478      *
 479      * We will forward to the MCE handler, which will either handle the SIGBUS
 480      * or reinstall the default SIGBUS handler and reraise the SIGBUS. The
 481      * default SIGBUS handler will crash the process, so we don't care.
 482      */
 483     if (sigbus_oldact.sa_flags & SA_SIGINFO) {
 484         sigbus_oldact.sa_sigaction(signal, siginfo, ctx);
 485         return;
 486     }
 487 #endif /* CONFIG_LINUX */
 488     warn_report("os_mem_prealloc: unrelated SIGBUS detected and ignored");
 489 }
 490
 491 static void *do_touch_pages(void *arg)
 492 {
 493     MemsetThread *memset_args = (MemsetThread *)arg;
 494     sigset_t set, oldset;
 495     int ret = 0;
 496
 497     /*
 498      * On Linux, the page faults from the loop below can cause mmap_sem
 499      * contention with allocation of the thread stacks.  Do not start
 500      * clearing until all threads have been created.
 501      */
 502     qemu_mutex_lock(&page_mutex);
 503     while (!memset_args->context->all_threads_created) {
 504         qemu_cond_wait(&page_cond, &page_mutex);
 505     }
 506     qemu_mutex_unlock(&page_mutex);
 507
 508     /* unblock SIGBUS */
 509     sigemptyset(&set);
 510     sigaddset(&set, SIGBUS);
 511     pthread_sigmask(SIG_UNBLOCK, &set, &oldset);
 512
 513     if (sigsetjmp(memset_args->env, 1)) {
 514         ret = -EFAULT;
 515     } else {
 516         char *addr = memset_args->addr;
 517         size_t numpages = memset_args->numpages;
 518         size_t hpagesize = memset_args->hpagesize;
 519         size_t i;
 520         for (i = 0; i < numpages; i++) {
 521             /*
 522              * Read & write back the same value, so we don't
 523              * corrupt existing user/app data that might be
 524              * stored.
 525              *
 526              * 'volatile' to stop compiler optimizing this away
 527              * to a no-op
 528              */
 529             *(volatile char *)addr = *addr;
 530             addr += hpagesize;
 531         }
 532     }
 533     pthread_sigmask(SIG_SETMASK, &oldset, NULL);
 534     return (void *)(uintptr_t)ret;
 535 }
 536
 537 static void *do_madv_populate_write_pages(void *arg)
 538 {
 539     MemsetThread *memset_args = (MemsetThread *)arg;
 540     const size_t size = memset_args->numpages * memset_args->hpagesize;
 541     char * const addr = memset_args->addr;
 542     int ret = 0;
 543
 544     /* See do_touch_pages(). */
 545     qemu_mutex_lock(&page_mutex);
 546     while (!memset_args->context->all_threads_created) {
 547         qemu_cond_wait(&page_cond, &page_mutex);
 548     }
 549     qemu_mutex_unlock(&page_mutex);
 550
 551     if (size && qemu_madvise(addr, size, QEMU_MADV_POPULATE_WRITE)) {
 552         ret = -errno;
 553     }
 554     return (void *)(uintptr_t)ret;
 555 }
 556
 557 static inline int get_memset_num_threads(size_t hpagesize, size_t numpages,
 558                                          int smp_cpus)
 559 {
 560     long host_procs = sysconf(_SC_NPROCESSORS_ONLN);
 561     int ret = 1;
 562
 563     if (host_procs > 0) {
 564         ret = MIN(MIN(host_procs, MAX_MEM_PREALLOC_THREAD_COUNT), smp_cpus);
 565     }
 566
 567     /* Especially with gigantic pages, don't create more threads than pages. */
 568     ret = MIN(ret, numpages);
 569     /* Don't start threads to prealloc comparatively little memory. */
 570     ret = MIN(ret, MAX(1, hpagesize * numpages / (64 * MiB)));
 571
 572     /* In case sysconf() fails, we fall back to single threaded */
 573     return ret;
 574 }
 575
 576 static int touch_all_pages(char *area, size_t hpagesize, size_t numpages,
 577                            int smp_cpus, bool use_madv_populate_write)
 578 {
 579     static gsize initialized = 0;
 580     MemsetContext context = {
 581         .num_threads = get_memset_num_threads(hpagesize, numpages, smp_cpus),
 582     };
 583     size_t numpages_per_thread, leftover;
 584     void *(*touch_fn)(void *);
 585     int ret = 0, i = 0;
 586     char *addr = area;
 587
 588     if (g_once_init_enter(&initialized)) {
 589         qemu_mutex_init(&page_mutex);
 590         qemu_cond_init(&page_cond);
 591         g_once_init_leave(&initialized, 1);
 592     }
 593
 594     if (use_madv_populate_write) {
 595         /* Avoid creating a single thread for MADV_POPULATE_WRITE */
 596         if (context.num_threads == 1) {
 597             if (qemu_madvise(area, hpagesize * numpages,
 598                              QEMU_MADV_POPULATE_WRITE)) {
 599                 return -errno;
 600             }
 601             return 0;
 602         }
 603         touch_fn = do_madv_populate_write_pages;
 604     } else {
 605         touch_fn = do_touch_pages;
 606     }
 607
 608     context.threads = g_new0(MemsetThread, context.num_threads);
 609     numpages_per_thread = numpages / context.num_threads;
 610     leftover = numpages % context.num_threads;
 611     for (i = 0; i < context.num_threads; i++) {
 612         context.threads[i].addr = addr;
 613         context.threads[i].numpages = numpages_per_thread + (i < leftover);
 614         context.threads[i].hpagesize = hpagesize;
 615         context.threads[i].context = &context;
 616         qemu_thread_create(&context.threads[i].pgthread, "touch_pages",
 617                            touch_fn, &context.threads[i],
 618                            QEMU_THREAD_JOINABLE);
 619         addr += context.threads[i].numpages * hpagesize;
 620     }
 621
 622     if (!use_madv_populate_write) {
 623         sigbus_memset_context = &context;
 624     }
 625
 626     qemu_mutex_lock(&page_mutex);
 627     context.all_threads_created = true;
 628     qemu_cond_broadcast(&page_cond);
 629     qemu_mutex_unlock(&page_mutex);
 630
 631     for (i = 0; i < context.num_threads; i++) {
 632         int tmp = (uintptr_t)qemu_thread_join(&context.threads[i].pgthread);
 633
 634         if (tmp) {
 635             ret = tmp;
 636         }
 637     }
 638
 639     if (!use_madv_populate_write) {
 640         sigbus_memset_context = NULL;
 641     }
 642     g_free(context.threads);
 643
 644     return ret;
 645 }
 646
 647 static bool madv_populate_write_possible(char *area, size_t pagesize)
 648 {
 649     return !qemu_madvise(area, pagesize, QEMU_MADV_POPULATE_WRITE) ||
 650            errno != EINVAL;
 651 }
 652
 653 void os_mem_prealloc(int fd, char *area, size_t memory, int smp_cpus,
 654                      Error **errp)
 655 {
 656     static gsize initialized;
 657     int ret;
 658     size_t hpagesize = qemu_fd_getpagesize(fd);
 659     size_t numpages = DIV_ROUND_UP(memory, hpagesize);
 660     bool use_madv_populate_write;
 661     struct sigaction act;
 662
 663     /*
 664      * Sense on every invocation, as MADV_POPULATE_WRITE cannot be used for
 665      * some special mappings, such as mapping /dev/mem.
 666      */
 667     use_madv_populate_write = madv_populate_write_possible(area, hpagesize);
 668
 669     if (!use_madv_populate_write) {
 670         if (g_once_init_enter(&initialized)) {
 671             qemu_mutex_init(&sigbus_mutex);
 672             g_once_init_leave(&initialized, 1);
 673         }
 674
 675         qemu_mutex_lock(&sigbus_mutex);
 676         memset(&act, 0, sizeof(act));
 677 #ifdef CONFIG_LINUX
 678         act.sa_sigaction = &sigbus_handler;
 679         act.sa_flags = SA_SIGINFO;
 680 #else /* CONFIG_LINUX */
 681         act.sa_handler = &sigbus_handler;
 682         act.sa_flags = 0;
 683 #endif /* CONFIG_LINUX */
 684
 685         ret = sigaction(SIGBUS, &act, &sigbus_oldact);
 686         if (ret) {
 687             qemu_mutex_unlock(&sigbus_mutex);
 688             error_setg_errno(errp, errno,
 689                 "os_mem_prealloc: failed to install signal handler");
 690             return;
 691         }
 692     }
 693
 694     /* touch pages simultaneously */
 695     ret = touch_all_pages(area, hpagesize, numpages, smp_cpus,
 696                           use_madv_populate_write);
 697     if (ret) {
 698         error_setg_errno(errp, -ret,
 699                          "os_mem_prealloc: preallocating memory failed");
 700     }
 701
 702     if (!use_madv_populate_write) {
 703         ret = sigaction(SIGBUS, &sigbus_oldact, NULL);
 704         if (ret) {
 705             /* Terminate QEMU since it can't recover from error */
 706             perror("os_mem_prealloc: failed to reinstall signal handler");
 707             exit(1);
 708         }
 709         qemu_mutex_unlock(&sigbus_mutex);
 710     }
 711 }
 712
 713 char *qemu_get_pid_name(pid_t pid)
 714 {
 715     char *name = NULL;
 716
 717 #if defined(__FreeBSD__)
 718     /* BSDs don't have /proc, but they provide a nice substitute */
 719     struct kinfo_proc *proc = kinfo_getproc(pid);
 720
 721     if (proc) {
 722         name = g_strdup(proc->ki_comm);
 723         free(proc);
 724     }
 725 #else
 726     /* Assume a system with reasonable procfs */
 727     char *pid_path;
 728     size_t len;
 729
 730     pid_path = g_strdup_printf("/proc/%d/cmdline", pid);
 731     g_file_get_contents(pid_path, &name, &len, NULL);
 732     g_free(pid_path);
 733 #endif
 734
 735     return name;
 736 }
 737
 738
 739 pid_t qemu_fork(Error **errp)
 740 {
 741     sigset_t oldmask, newmask;
 742     struct sigaction sig_action;
 743     int saved_errno;
 744     pid_t pid;
 745
 746     /*
 747      * Need to block signals now, so that child process can safely
 748      * kill off caller's signal handlers without a race.
 749      */
 750     sigfillset(&newmask);
 751     if (pthread_sigmask(SIG_SETMASK, &newmask, &oldmask) != 0) {
 752         error_setg_errno(errp, errno,
 753                          "cannot block signals");
 754         return -1;
 755     }
 756
 757     pid = fork();
 758     saved_errno = errno;
 759
 760     if (pid < 0) {
 761         /* attempt to restore signal mask, but ignore failure, to
 762          * avoid obscuring the fork failure */
 763         (void)pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
 764         error_setg_errno(errp, saved_errno,
 765                          "cannot fork child process");
 766         errno = saved_errno;
 767         return -1;
 768     } else if (pid) {
 769         /* parent process */
 770
 771         /* Restore our original signal mask now that the child is
 772          * safely running. Only documented failures are EFAULT (not
 773          * possible, since we are using just-grabbed mask) or EINVAL
 774          * (not possible, since we are using correct arguments).  */
 775         (void)pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
 776     } else {
 777         /* child process */
 778         size_t i;
 779
 780         /* Clear out all signal handlers from parent so nothing
 781          * unexpected can happen in our child once we unblock
 782          * signals */
 783         sig_action.sa_handler = SIG_DFL;
 784         sig_action.sa_flags = 0;
 785         sigemptyset(&sig_action.sa_mask);
 786
 787         for (i = 1; i < NSIG; i++) {
 788             /* Only possible errors are EFAULT or EINVAL The former
 789              * won't happen, the latter we expect, so no need to check
 790              * return value */
 791             (void)sigaction(i, &sig_action, NULL);
 792         }
 793
 794         /* Unmask all signals in child, since we've no idea what the
 795          * caller's done with their signal mask and don't want to
 796          * propagate that to children */
 797         sigemptyset(&newmask);
 798         if (pthread_sigmask(SIG_SETMASK, &newmask, NULL) != 0) {
 799             Error *local_err = NULL;
 800             error_setg_errno(&local_err, errno,
 801                              "cannot unblock signals");
 802             error_report_err(local_err);
 803             _exit(1);
 804         }
 805     }
 806     return pid;
 807 }
 808
 809 void *qemu_alloc_stack(size_t *sz)
 810 {
 811     void *ptr, *guardpage;
 812     int flags;
 813 #ifdef CONFIG_DEBUG_STACK_USAGE
 814     void *ptr2;
 815 #endif
 816     size_t pagesz = qemu_real_host_page_size;
 817 #ifdef _SC_THREAD_STACK_MIN
 818     /* avoid stacks smaller than _SC_THREAD_STACK_MIN */
 819     long min_stack_sz = sysconf(_SC_THREAD_STACK_MIN);
 820     *sz = MAX(MAX(min_stack_sz, 0), *sz);
 821 #endif
 822     /* adjust stack size to a multiple of the page size */
 823     *sz = ROUND_UP(*sz, pagesz);
 824     /* allocate one extra page for the guard page */
 825     *sz += pagesz;
 826
 827     flags = MAP_PRIVATE | MAP_ANONYMOUS;
 828 #if defined(MAP_STACK) && defined(__OpenBSD__)
 829     /* Only enable MAP_STACK on OpenBSD. Other OS's such as
 830      * Linux/FreeBSD/NetBSD have a flag with the same name
 831      * but have differing functionality. OpenBSD will SEGV
 832      * if it spots execution with a stack pointer pointing
 833      * at memory that was not allocated with MAP_STACK.
 834      */
 835     flags |= MAP_STACK;
 836 #endif
 837
 838     ptr = mmap(NULL, *sz, PROT_READ | PROT_WRITE, flags, -1, 0);
 839     if (ptr == MAP_FAILED) {
 840         perror("failed to allocate memory for stack");
 841         abort();
 842     }
 843
 844 #if defined(HOST_IA64)
 845     /* separate register stack */
 846     guardpage = ptr + (((*sz - pagesz) / 2) & ~pagesz);
 847 #elif defined(HOST_HPPA)
 848     /* stack grows up */
 849     guardpage = ptr + *sz - pagesz;
 850 #else
 851     /* stack grows down */
 852     guardpage = ptr;
 853 #endif
 854     if (mprotect(guardpage, pagesz, PROT_NONE) != 0) {
 855         perror("failed to set up stack guard page");
 856         abort();
 857     }
 858
 859 #ifdef CONFIG_DEBUG_STACK_USAGE
 860     for (ptr2 = ptr + pagesz; ptr2 < ptr + *sz; ptr2 += sizeof(uint32_t)) {
 861         *(uint32_t *)ptr2 = 0xdeadbeaf;
 862     }
 863 #endif
 864
 865     return ptr;
 866 }
 867
 868 #ifdef CONFIG_DEBUG_STACK_USAGE
 869 static __thread unsigned int max_stack_usage;
 870 #endif
 871
 872 void qemu_free_stack(void *stack, size_t sz)
 873 {
 874 #ifdef CONFIG_DEBUG_STACK_USAGE
 875     unsigned int usage;
 876     void *ptr;
 877
 878     for (ptr = stack + qemu_real_host_page_size; ptr < stack + sz;
 879          ptr += sizeof(uint32_t)) {
 880         if (*(uint32_t *)ptr != 0xdeadbeaf) {
 881             break;
 882         }
 883     }
 884     usage = sz - (uintptr_t) (ptr - stack);
 885     if (usage > max_stack_usage) {
 886         error_report("thread %d max stack usage increased from %u to %u",
 887                      qemu_get_thread_id(), max_stack_usage, usage);
 888         max_stack_usage = usage;
 889     }
 890 #endif
 891
 892     munmap(stack, sz);
 893 }
 894
 895 /*
 896  * Disable CFI checks.
 897  * We are going to call a signal hander directly. Such handler may or may not
 898  * have been defined in our binary, so there's no guarantee that the pointer
 899  * used to set the handler is a cfi-valid pointer. Since the handlers are
 900  * stored in kernel memory, changing the handler to an attacker-defined
 901  * function requires being able to call a sigaction() syscall,
 902  * which is not as easy as overwriting a pointer in memory.
 903  */
 904 QEMU_DISABLE_CFI
 905 void sigaction_invoke(struct sigaction *action,
 906                       struct qemu_signalfd_siginfo *info)
 907 {
 908     siginfo_t si = {};
 909     si.si_signo = info->ssi_signo;
 910     si.si_errno = info->ssi_errno;
 911     si.si_code = info->ssi_code;
 912
 913     /* Convert the minimal set of fields defined by POSIX.
 914      * Positive si_code values are reserved for kernel-generated
 915      * signals, where the valid siginfo fields are determined by
 916      * the signal number.  But according to POSIX, it is unspecified
 917      * whether SI_USER and SI_QUEUE have values less than or equal to
 918      * zero.
 919      */
 920     if (info->ssi_code == SI_USER || info->ssi_code == SI_QUEUE ||
 921         info->ssi_code <= 0) {
 922         /* SIGTERM, etc.  */
 923         si.si_pid = info->ssi_pid;
 924         si.si_uid = info->ssi_uid;
 925     } else if (info->ssi_signo == SIGILL || info->ssi_signo == SIGFPE ||
 926                info->ssi_signo == SIGSEGV || info->ssi_signo == SIGBUS) {
 927         si.si_addr = (void *)(uintptr_t)info->ssi_addr;
 928     } else if (info->ssi_signo == SIGCHLD) {
 929         si.si_pid = info->ssi_pid;
 930         si.si_status = info->ssi_status;
 931         si.si_uid = info->ssi_uid;
 932     }
 933     action->sa_sigaction(info->ssi_signo, &si, NULL);
 934 }
 935
 936 #ifndef HOST_NAME_MAX
 937 # ifdef _POSIX_HOST_NAME_MAX
 938 #  define HOST_NAME_MAX _POSIX_HOST_NAME_MAX
 939 # else
 940 #  define HOST_NAME_MAX 255
 941 # endif
 942 #endif
 943
 944 char *qemu_get_host_name(Error **errp)
 945 {
 946     long len = -1;
 947     g_autofree char *hostname = NULL;
 948
 949 #ifdef _SC_HOST_NAME_MAX
 950     len = sysconf(_SC_HOST_NAME_MAX);
 951 #endif /* _SC_HOST_NAME_MAX */
 952
 953     if (len < 0) {
 954         len = HOST_NAME_MAX;
 955     }
 956
 957     /* Unfortunately, gethostname() below does not guarantee a
 958      * NULL terminated string. Therefore, allocate one byte more
 959      * to be sure. */
 960     hostname = g_new0(char, len + 1);
 961
 962     if (gethostname(hostname, len) < 0) {
 963         error_setg_errno(errp, errno,
 964                          "cannot get hostname");
 965         return NULL;
 966     }
 967
 968     return g_steal_pointer(&hostname);
 969 }
 970
 971 size_t qemu_get_host_physmem(void)
 972 {
 973 #ifdef _SC_PHYS_PAGES
 974     long pages = sysconf(_SC_PHYS_PAGES);
 975     if (pages > 0) {
 976         if (pages > SIZE_MAX / qemu_real_host_page_size) {
 977             return SIZE_MAX;
 978         } else {
 979             return pages * qemu_real_host_page_size;
 980         }
 981     }
 982 #endif
 983     return 0;
 984 }