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