qemu

oslib-posix.c (23508B)

---

 /*
  * os-posix-lib.c
  *
  * Copyright (c) 2003-2008 Fabrice Bellard
  * Copyright (c) 2010 Red Hat, Inc.
  *
  * QEMU library functions on POSIX which are shared between QEMU and
  * the QEMU tools.
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
  * in the Software without restriction, including without limitation the rights
  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  * copies of the Software, and to permit persons to whom the Software is
  * furnished to do so, subject to the following conditions:
  *
  * The above copyright notice and this permission notice shall be included in
  * all copies or substantial portions of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */
 
 #include "qemu/osdep.h"
 #include <termios.h>
 
 #include <glib/gprintf.h>
 
 #include "sysemu/sysemu.h"
 #include "trace.h"
 #include "qapi/error.h"
 #include "qemu/error-report.h"
 #include "qemu/madvise.h"
 #include "qemu/sockets.h"
 #include "qemu/thread.h"
 #include <libgen.h>
 #include "qemu/cutils.h"
 #include "qemu/compiler.h"
 #include "qemu/units.h"
 #include "qemu/thread-context.h"
 
 #ifdef CONFIG_LINUX
 #include <sys/syscall.h>
 #endif
 
 #ifdef __FreeBSD__
 #include <sys/thr.h>
 #include <sys/types.h>
 #include <sys/user.h>
 #include <libutil.h>
 #endif
 
 #ifdef __NetBSD__
 #include <lwp.h>
 #endif
 
 #include "qemu/mmap-alloc.h"
 
 #ifdef CONFIG_DEBUG_STACK_USAGE
 #include "qemu/error-report.h"
 #endif
 
 #define MAX_MEM_PREALLOC_THREAD_COUNT 16
 
 struct MemsetThread;
 
 typedef struct MemsetContext {
     bool all_threads_created;
     bool any_thread_failed;
     struct MemsetThread *threads;
     int num_threads;
 } MemsetContext;
 
 struct MemsetThread {
     char *addr;
     size_t numpages;
     size_t hpagesize;
     QemuThread pgthread;
     sigjmp_buf env;
     MemsetContext *context;
 };
 typedef struct MemsetThread MemsetThread;
 
 /* used by sigbus_handler() */
 static MemsetContext *sigbus_memset_context;
 struct sigaction sigbus_oldact;
 static QemuMutex sigbus_mutex;
 
 static QemuMutex page_mutex;
 static QemuCond page_cond;
 
 int qemu_get_thread_id(void)
 {
 #if defined(__linux__)
     return syscall(SYS_gettid);
 #elif defined(__FreeBSD__)
     /* thread id is up to INT_MAX */
     long tid;
     thr_self(&tid);
     return (int)tid;
 #elif defined(__NetBSD__)
     return _lwp_self();
 #elif defined(__OpenBSD__)
     return getthrid();
 #else
     return getpid();
 #endif
 }
 
 int qemu_daemon(int nochdir, int noclose)
 {
     return daemon(nochdir, noclose);
 }
 
 bool qemu_write_pidfile(const char *path, Error **errp)
 {
     int fd;
     char pidstr[32];
 
     while (1) {
         struct stat a, b;
         struct flock lock = {
             .l_type = F_WRLCK,
             .l_whence = SEEK_SET,
             .l_len = 0,
         };
 
         fd = qemu_create(path, O_WRONLY, S_IRUSR | S_IWUSR, errp);
         if (fd == -1) {
             return false;
         }
 
         if (fstat(fd, &b) < 0) {
             error_setg_errno(errp, errno, "Cannot stat file");
             goto fail_close;
         }
 
         if (fcntl(fd, F_SETLK, &lock)) {
             error_setg_errno(errp, errno, "Cannot lock pid file");
             goto fail_close;
         }
 
         /*
          * Now make sure the path we locked is the same one that now
          * exists on the filesystem.
          */
         if (stat(path, &a) < 0) {
             /*
              * PID file disappeared, someone else must be racing with
              * us, so try again.
              */
             close(fd);
             continue;
         }
 
         if (a.st_ino == b.st_ino) {
             break;
         }
 
         /*
          * PID file was recreated, someone else must be racing with
          * us, so try again.
          */
         close(fd);
     }
 
     if (ftruncate(fd, 0) < 0) {
         error_setg_errno(errp, errno, "Failed to truncate pid file");
         goto fail_unlink;
     }
 
     snprintf(pidstr, sizeof(pidstr), FMT_pid "\n", getpid());
     if (qemu_write_full(fd, pidstr, strlen(pidstr)) != strlen(pidstr)) {
         error_setg(errp, "Failed to write pid file");
         goto fail_unlink;
     }
 
     return true;
 
 fail_unlink:
     unlink(path);
 fail_close:
     close(fd);
     return false;
 }
 
 /* alloc shared memory pages */
 void *qemu_anon_ram_alloc(size_t size, uint64_t *alignment, bool shared,
                           bool noreserve)
 {
     const uint32_t qemu_map_flags = (shared ? QEMU_MAP_SHARED : 0) |
                                     (noreserve ? QEMU_MAP_NORESERVE : 0);
     size_t align = QEMU_VMALLOC_ALIGN;
     void *ptr = qemu_ram_mmap(-1, size, align, qemu_map_flags, 0);
 
     if (ptr == MAP_FAILED) {
         return NULL;
     }
 
     if (alignment) {
         *alignment = align;
     }
 
     trace_qemu_anon_ram_alloc(size, ptr);
     return ptr;
 }
 
 void qemu_anon_ram_free(void *ptr, size_t size)
 {
     trace_qemu_anon_ram_free(ptr, size);
     qemu_ram_munmap(-1, ptr, size);
 }
 
 void qemu_socket_set_block(int fd)
 {
     g_unix_set_fd_nonblocking(fd, false, NULL);
 }
 
 int qemu_socket_try_set_nonblock(int fd)
 {
     return g_unix_set_fd_nonblocking(fd, true, NULL) ? 0 : -errno;
 }
 
 void qemu_socket_set_nonblock(int fd)
 {
     int f;
     f = qemu_socket_try_set_nonblock(fd);
     assert(f == 0);
 }
 
 int socket_set_fast_reuse(int fd)
 {
     int val = 1, ret;
 
     ret = setsockopt(fd, SOL_SOCKET, SO_REUSEADDR,
                      (const char *)&val, sizeof(val));
 
     assert(ret == 0);
 
     return ret;
 }
 
 void qemu_set_cloexec(int fd)
 {
     int f;
     f = fcntl(fd, F_GETFD);
     assert(f != -1);
     f = fcntl(fd, F_SETFD, f | FD_CLOEXEC);
     assert(f != -1);
 }
 
 int qemu_socketpair(int domain, int type, int protocol, int sv[2])
 {
     int ret;
 
 #ifdef SOCK_CLOEXEC
     ret = socketpair(domain, type | SOCK_CLOEXEC, protocol, sv);
     if (ret != -1 || errno != EINVAL) {
         return ret;
     }
 #endif
     ret = socketpair(domain, type, protocol, sv);;
     if (ret == 0) {
         qemu_set_cloexec(sv[0]);
         qemu_set_cloexec(sv[1]);
     }
 
     return ret;
 }
 
 char *
 qemu_get_local_state_dir(void)
 {
     return get_relocated_path(CONFIG_QEMU_LOCALSTATEDIR);
 }
 
 void qemu_set_tty_echo(int fd, bool echo)
 {
     struct termios tty;
 
     tcgetattr(fd, &tty);
 
     if (echo) {
         tty.c_lflag |= ECHO | ECHONL | ICANON | IEXTEN;
     } else {
         tty.c_lflag &= ~(ECHO | ECHONL | ICANON | IEXTEN);
     }
 
     tcsetattr(fd, TCSANOW, &tty);
 }
 
 #ifdef CONFIG_LINUX
 static void sigbus_handler(int signal, siginfo_t *siginfo, void *ctx)
 #else /* CONFIG_LINUX */
 static void sigbus_handler(int signal)
 #endif /* CONFIG_LINUX */
 {
     int i;
 
     if (sigbus_memset_context) {
         for (i = 0; i < sigbus_memset_context->num_threads; i++) {
             MemsetThread *thread = &sigbus_memset_context->threads[i];
 
             if (qemu_thread_is_self(&thread->pgthread)) {
                 siglongjmp(thread->env, 1);
             }
         }
     }
 
 #ifdef CONFIG_LINUX
     /*
      * We assume that the MCE SIGBUS handler could have been registered. We
      * should never receive BUS_MCEERR_AO on any of our threads, but only on
      * the main thread registered for PR_MCE_KILL_EARLY. Further, we should not
      * receive BUS_MCEERR_AR triggered by action of other threads on one of
      * our threads. So, no need to check for unrelated SIGBUS when seeing one
      * for our threads.
      *
      * We will forward to the MCE handler, which will either handle the SIGBUS
      * or reinstall the default SIGBUS handler and reraise the SIGBUS. The
      * default SIGBUS handler will crash the process, so we don't care.
      */
     if (sigbus_oldact.sa_flags & SA_SIGINFO) {
         sigbus_oldact.sa_sigaction(signal, siginfo, ctx);
         return;
     }
 #endif /* CONFIG_LINUX */
     warn_report("qemu_prealloc_mem: unrelated SIGBUS detected and ignored");
 }
 
 static void *do_touch_pages(void *arg)
 {
     MemsetThread *memset_args = (MemsetThread *)arg;
     sigset_t set, oldset;
     int ret = 0;
 
     /*
      * On Linux, the page faults from the loop below can cause mmap_sem
      * contention with allocation of the thread stacks.  Do not start
      * clearing until all threads have been created.
      */
     qemu_mutex_lock(&page_mutex);
     while (!memset_args->context->all_threads_created) {
         qemu_cond_wait(&page_cond, &page_mutex);
     }
     qemu_mutex_unlock(&page_mutex);
 
     /* unblock SIGBUS */
     sigemptyset(&set);
     sigaddset(&set, SIGBUS);
     pthread_sigmask(SIG_UNBLOCK, &set, &oldset);
 
     if (sigsetjmp(memset_args->env, 1)) {
         ret = -EFAULT;
     } else {
         char *addr = memset_args->addr;
         size_t numpages = memset_args->numpages;
         size_t hpagesize = memset_args->hpagesize;
         size_t i;
         for (i = 0; i < numpages; i++) {
             /*
              * Read & write back the same value, so we don't
              * corrupt existing user/app data that might be
              * stored.
              *
              * 'volatile' to stop compiler optimizing this away
              * to a no-op
              */
             *(volatile char *)addr = *addr;
             addr += hpagesize;
         }
     }
     pthread_sigmask(SIG_SETMASK, &oldset, NULL);
     return (void *)(uintptr_t)ret;
 }
 
 static void *do_madv_populate_write_pages(void *arg)
 {
     MemsetThread *memset_args = (MemsetThread *)arg;
     const size_t size = memset_args->numpages * memset_args->hpagesize;
     char * const addr = memset_args->addr;
     int ret = 0;
 
     /* See do_touch_pages(). */
     qemu_mutex_lock(&page_mutex);
     while (!memset_args->context->all_threads_created) {
         qemu_cond_wait(&page_cond, &page_mutex);
     }
     qemu_mutex_unlock(&page_mutex);
 
     if (size && qemu_madvise(addr, size, QEMU_MADV_POPULATE_WRITE)) {
         ret = -errno;
     }
     return (void *)(uintptr_t)ret;
 }
 
 static inline int get_memset_num_threads(size_t hpagesize, size_t numpages,
                                          int max_threads)
 {
     long host_procs = sysconf(_SC_NPROCESSORS_ONLN);
     int ret = 1;
 
     if (host_procs > 0) {
         ret = MIN(MIN(host_procs, MAX_MEM_PREALLOC_THREAD_COUNT), max_threads);
     }
 
     /* Especially with gigantic pages, don't create more threads than pages. */
     ret = MIN(ret, numpages);
     /* Don't start threads to prealloc comparatively little memory. */
     ret = MIN(ret, MAX(1, hpagesize * numpages / (64 * MiB)));
 
     /* In case sysconf() fails, we fall back to single threaded */
     return ret;
 }
 
 static int touch_all_pages(char *area, size_t hpagesize, size_t numpages,
                            int max_threads, ThreadContext *tc,
                            bool use_madv_populate_write)
 {
     static gsize initialized = 0;
     MemsetContext context = {
         .num_threads = get_memset_num_threads(hpagesize, numpages, max_threads),
     };
     size_t numpages_per_thread, leftover;
     void *(*touch_fn)(void *);
     int ret = 0, i = 0;
     char *addr = area;
 
     if (g_once_init_enter(&initialized)) {
         qemu_mutex_init(&page_mutex);
         qemu_cond_init(&page_cond);
         g_once_init_leave(&initialized, 1);
     }
 
     if (use_madv_populate_write) {
         /* Avoid creating a single thread for MADV_POPULATE_WRITE */
         if (context.num_threads == 1) {
             if (qemu_madvise(area, hpagesize * numpages,
                              QEMU_MADV_POPULATE_WRITE)) {
                 return -errno;
             }
             return 0;
         }
         touch_fn = do_madv_populate_write_pages;
     } else {
         touch_fn = do_touch_pages;
     }
 
     context.threads = g_new0(MemsetThread, context.num_threads);
     numpages_per_thread = numpages / context.num_threads;
     leftover = numpages % context.num_threads;
     for (i = 0; i < context.num_threads; i++) {
         context.threads[i].addr = addr;
         context.threads[i].numpages = numpages_per_thread + (i < leftover);
         context.threads[i].hpagesize = hpagesize;
         context.threads[i].context = &context;
         if (tc) {
             thread_context_create_thread(tc, &context.threads[i].pgthread,
                                          "touch_pages",
                                          touch_fn, &context.threads[i],
                                          QEMU_THREAD_JOINABLE);
         } else {
             qemu_thread_create(&context.threads[i].pgthread, "touch_pages",
                                touch_fn, &context.threads[i],
                                QEMU_THREAD_JOINABLE);
         }
         addr += context.threads[i].numpages * hpagesize;
     }
 
     if (!use_madv_populate_write) {
         sigbus_memset_context = &context;
     }
 
     qemu_mutex_lock(&page_mutex);
     context.all_threads_created = true;
     qemu_cond_broadcast(&page_cond);
     qemu_mutex_unlock(&page_mutex);
 
     for (i = 0; i < context.num_threads; i++) {
         int tmp = (uintptr_t)qemu_thread_join(&context.threads[i].pgthread);
 
         if (tmp) {
             ret = tmp;
         }
     }
 
     if (!use_madv_populate_write) {
         sigbus_memset_context = NULL;
     }
     g_free(context.threads);
 
     return ret;
 }
 
 static bool madv_populate_write_possible(char *area, size_t pagesize)
 {
     return !qemu_madvise(area, pagesize, QEMU_MADV_POPULATE_WRITE) ||
            errno != EINVAL;
 }
 
 void qemu_prealloc_mem(int fd, char *area, size_t sz, int max_threads,
                        ThreadContext *tc, Error **errp)
 {
     static gsize initialized;
     int ret;
     size_t hpagesize = qemu_fd_getpagesize(fd);
     size_t numpages = DIV_ROUND_UP(sz, hpagesize);
     bool use_madv_populate_write;
     struct sigaction act;
 
     /*
      * Sense on every invocation, as MADV_POPULATE_WRITE cannot be used for
      * some special mappings, such as mapping /dev/mem.
      */
     use_madv_populate_write = madv_populate_write_possible(area, hpagesize);
 
     if (!use_madv_populate_write) {
         if (g_once_init_enter(&initialized)) {
             qemu_mutex_init(&sigbus_mutex);
             g_once_init_leave(&initialized, 1);
         }
 
         qemu_mutex_lock(&sigbus_mutex);
         memset(&act, 0, sizeof(act));
 #ifdef CONFIG_LINUX
         act.sa_sigaction = &sigbus_handler;
         act.sa_flags = SA_SIGINFO;
 #else /* CONFIG_LINUX */
         act.sa_handler = &sigbus_handler;
         act.sa_flags = 0;
 #endif /* CONFIG_LINUX */
 
         ret = sigaction(SIGBUS, &act, &sigbus_oldact);
         if (ret) {
             qemu_mutex_unlock(&sigbus_mutex);
             error_setg_errno(errp, errno,
                 "qemu_prealloc_mem: failed to install signal handler");
             return;
         }
     }
 
     /* touch pages simultaneously */
     ret = touch_all_pages(area, hpagesize, numpages, max_threads, tc,
                           use_madv_populate_write);
     if (ret) {
         error_setg_errno(errp, -ret,
                          "qemu_prealloc_mem: preallocating memory failed");
     }
 
     if (!use_madv_populate_write) {
         ret = sigaction(SIGBUS, &sigbus_oldact, NULL);
         if (ret) {
             /* Terminate QEMU since it can't recover from error */
             perror("qemu_prealloc_mem: failed to reinstall signal handler");
             exit(1);
         }
         qemu_mutex_unlock(&sigbus_mutex);
     }
 }
 
 char *qemu_get_pid_name(pid_t pid)
 {
     char *name = NULL;
 
 #if defined(__FreeBSD__)
     /* BSDs don't have /proc, but they provide a nice substitute */
     struct kinfo_proc *proc = kinfo_getproc(pid);
 
     if (proc) {
         name = g_strdup(proc->ki_comm);
         free(proc);
     }
 #else
     /* Assume a system with reasonable procfs */
     char *pid_path;
     size_t len;
 
     pid_path = g_strdup_printf("/proc/%d/cmdline", pid);
     g_file_get_contents(pid_path, &name, &len, NULL);
     g_free(pid_path);
 #endif
 
     return name;
 }
 
 
 pid_t qemu_fork(Error **errp)
 {
     sigset_t oldmask, newmask;
     struct sigaction sig_action;
     int saved_errno;
     pid_t pid;
 
     /*
      * Need to block signals now, so that child process can safely
      * kill off caller's signal handlers without a race.
      */
     sigfillset(&newmask);
     if (pthread_sigmask(SIG_SETMASK, &newmask, &oldmask) != 0) {
         error_setg_errno(errp, errno,
                          "cannot block signals");
         return -1;
     }
 
     pid = fork();
     saved_errno = errno;
 
     if (pid < 0) {
         /* attempt to restore signal mask, but ignore failure, to
          * avoid obscuring the fork failure */
         (void)pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
         error_setg_errno(errp, saved_errno,
                          "cannot fork child process");
         errno = saved_errno;
         return -1;
     } else if (pid) {
         /* parent process */
 
         /* Restore our original signal mask now that the child is
          * safely running. Only documented failures are EFAULT (not
          * possible, since we are using just-grabbed mask) or EINVAL
          * (not possible, since we are using correct arguments).  */
         (void)pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
     } else {
         /* child process */
         size_t i;
 
         /* Clear out all signal handlers from parent so nothing
          * unexpected can happen in our child once we unblock
          * signals */
         sig_action.sa_handler = SIG_DFL;
         sig_action.sa_flags = 0;
         sigemptyset(&sig_action.sa_mask);
 
         for (i = 1; i < NSIG; i++) {
             /* Only possible errors are EFAULT or EINVAL The former
              * won't happen, the latter we expect, so no need to check
              * return value */
             (void)sigaction(i, &sig_action, NULL);
         }
 
         /* Unmask all signals in child, since we've no idea what the
          * caller's done with their signal mask and don't want to
          * propagate that to children */
         sigemptyset(&newmask);
         if (pthread_sigmask(SIG_SETMASK, &newmask, NULL) != 0) {
             Error *local_err = NULL;
             error_setg_errno(&local_err, errno,
                              "cannot unblock signals");
             error_report_err(local_err);
             _exit(1);
         }
     }
     return pid;
 }
 
 void *qemu_alloc_stack(size_t *sz)
 {
     void *ptr, *guardpage;
     int flags;
 #ifdef CONFIG_DEBUG_STACK_USAGE
     void *ptr2;
 #endif
     size_t pagesz = qemu_real_host_page_size();
 #ifdef _SC_THREAD_STACK_MIN
     /* avoid stacks smaller than _SC_THREAD_STACK_MIN */
     long min_stack_sz = sysconf(_SC_THREAD_STACK_MIN);
     *sz = MAX(MAX(min_stack_sz, 0), *sz);
 #endif
     /* adjust stack size to a multiple of the page size */
     *sz = ROUND_UP(*sz, pagesz);
     /* allocate one extra page for the guard page */
     *sz += pagesz;
 
     flags = MAP_PRIVATE | MAP_ANONYMOUS;
 #if defined(MAP_STACK) && defined(__OpenBSD__)
     /* Only enable MAP_STACK on OpenBSD. Other OS's such as
      * Linux/FreeBSD/NetBSD have a flag with the same name
      * but have differing functionality. OpenBSD will SEGV
      * if it spots execution with a stack pointer pointing
      * at memory that was not allocated with MAP_STACK.
      */
     flags |= MAP_STACK;
 #endif
 
     ptr = mmap(NULL, *sz, PROT_READ | PROT_WRITE, flags, -1, 0);
     if (ptr == MAP_FAILED) {
         perror("failed to allocate memory for stack");
         abort();
     }
 
 #if defined(HOST_IA64)
     /* separate register stack */
     guardpage = ptr + (((*sz - pagesz) / 2) & ~pagesz);
 #elif defined(HOST_HPPA)
     /* stack grows up */
     guardpage = ptr + *sz - pagesz;
 #else
     /* stack grows down */
     guardpage = ptr;
 #endif
     if (mprotect(guardpage, pagesz, PROT_NONE) != 0) {
         perror("failed to set up stack guard page");
         abort();
     }
 
 #ifdef CONFIG_DEBUG_STACK_USAGE
     for (ptr2 = ptr + pagesz; ptr2 < ptr + *sz; ptr2 += sizeof(uint32_t)) {
         *(uint32_t *)ptr2 = 0xdeadbeaf;
     }
 #endif
 
     return ptr;
 }
 
 #ifdef CONFIG_DEBUG_STACK_USAGE
 static __thread unsigned int max_stack_usage;
 #endif
 
 void qemu_free_stack(void *stack, size_t sz)
 {
 #ifdef CONFIG_DEBUG_STACK_USAGE
     unsigned int usage;
     void *ptr;
 
     for (ptr = stack + qemu_real_host_page_size(); ptr < stack + sz;
          ptr += sizeof(uint32_t)) {
         if (*(uint32_t *)ptr != 0xdeadbeaf) {
             break;
         }
     }
     usage = sz - (uintptr_t) (ptr - stack);
     if (usage > max_stack_usage) {
         error_report("thread %d max stack usage increased from %u to %u",
                      qemu_get_thread_id(), max_stack_usage, usage);
         max_stack_usage = usage;
     }
 #endif
 
     munmap(stack, sz);
 }
 
 /*
  * Disable CFI checks.
  * We are going to call a signal hander directly. Such handler may or may not
  * have been defined in our binary, so there's no guarantee that the pointer
  * used to set the handler is a cfi-valid pointer. Since the handlers are
  * stored in kernel memory, changing the handler to an attacker-defined
  * function requires being able to call a sigaction() syscall,
  * which is not as easy as overwriting a pointer in memory.
  */
 QEMU_DISABLE_CFI
 void sigaction_invoke(struct sigaction *action,
                       struct qemu_signalfd_siginfo *info)
 {
     siginfo_t si = {};
     si.si_signo = info->ssi_signo;
     si.si_errno = info->ssi_errno;
     si.si_code = info->ssi_code;
 
     /* Convert the minimal set of fields defined by POSIX.
      * Positive si_code values are reserved for kernel-generated
      * signals, where the valid siginfo fields are determined by
      * the signal number.  But according to POSIX, it is unspecified
      * whether SI_USER and SI_QUEUE have values less than or equal to
      * zero.
      */
     if (info->ssi_code == SI_USER || info->ssi_code == SI_QUEUE ||
         info->ssi_code <= 0) {
         /* SIGTERM, etc.  */
         si.si_pid = info->ssi_pid;
         si.si_uid = info->ssi_uid;
     } else if (info->ssi_signo == SIGILL || info->ssi_signo == SIGFPE ||
                info->ssi_signo == SIGSEGV || info->ssi_signo == SIGBUS) {
         si.si_addr = (void *)(uintptr_t)info->ssi_addr;
     } else if (info->ssi_signo == SIGCHLD) {
         si.si_pid = info->ssi_pid;
         si.si_status = info->ssi_status;
         si.si_uid = info->ssi_uid;
     }
     action->sa_sigaction(info->ssi_signo, &si, NULL);
 }
 
 size_t qemu_get_host_physmem(void)
 {
 #ifdef _SC_PHYS_PAGES
     long pages = sysconf(_SC_PHYS_PAGES);
     if (pages > 0) {
         if (pages > SIZE_MAX / qemu_real_host_page_size()) {
             return SIZE_MAX;
         } else {
             return pages * qemu_real_host_page_size();
         }
     }
 #endif
     return 0;
 }
 
 int qemu_msync(void *addr, size_t length, int fd)
 {
     size_t align_mask = ~(qemu_real_host_page_size() - 1);
 
     /**
      * There are no strict reqs as per the length of mapping
      * to be synced. Still the length needs to follow the address
      * alignment changes. Additionally - round the size to the multiple
      * of PAGE_SIZE
      */
     length += ((uintptr_t)addr & (qemu_real_host_page_size() - 1));
     length = (length + ~align_mask) & align_mask;
 
     addr = (void *)((uintptr_t)addr & align_mask);
 
     return msync(addr, length, MS_SYNC);
 }