aboutsummaryrefslogtreecommitdiff
path: root/util/oslib-posix.c
blob: 760390b31e5f160933563b59af521531d8b95ad4 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
/*
 * 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/units.h"
#include "qemu/thread-context.h"

#ifdef CONFIG_LINUX
#include <sys/syscall.h>
#endif

#ifdef __FreeBSD__
#include <sys/thr.h>
#include <sys/user.h>
#include <libutil.h>
#endif

#ifdef __NetBSD__
#include <lwp.h>
#endif

#include "qemu/mmap-alloc.h"

#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;
}


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);
}