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