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