// SPDX-License-Identifier: GPL-2.0-only
/*
 * Stress userfaultfd syscall.
 *
 *  Copyright (C) 2015  Red Hat, Inc.
 *
 * This test allocates two virtual areas and bounces the physical
 * memory across the two virtual areas (from area_src to area_dst)
 * using userfaultfd.
 *
 * There are three threads running per CPU:
 *
 * 1) one per-CPU thread takes a per-page pthread_mutex in a random
 *    page of the area_dst (while the physical page may still be in
 *    area_src), and increments a per-page counter in the same page,
 *    and checks its value against a verification region.
 *
 * 2) another per-CPU thread handles the userfaults generated by
 *    thread 1 above. userfaultfd blocking reads or poll() modes are
 *    exercised interleaved.
 *
 * 3) one last per-CPU thread transfers the memory in the background
 *    at maximum bandwidth (if not already transferred by thread
 *    2). Each cpu thread takes cares of transferring a portion of the
 *    area.
 *
 * When all threads of type 3 completed the transfer, one bounce is
 * complete. area_src and area_dst are then swapped. All threads are
 * respawned and so the bounce is immediately restarted in the
 * opposite direction.
 *
 * per-CPU threads 1 by triggering userfaults inside
 * pthread_mutex_lock will also verify the atomicity of the memory
 * transfer (UFFDIO_COPY).
 */

#define _GNU_SOURCE
#include <stdio.h>
#include <errno.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <time.h>
#include <signal.h>
#include <poll.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/syscall.h>
#include <sys/ioctl.h>
#include <sys/wait.h>
#include <pthread.h>
#include <linux/userfaultfd.h>
#include <setjmp.h>
#include <stdbool.h>
#include <assert.h>
#include <inttypes.h>
#include <stdint.h>

#include "../kselftest.h"

#ifdef __NR_userfaultfd

static unsigned long nr_cpus, nr_pages, nr_pages_per_cpu, page_size;

#define BOUNCE_RANDOM           (1<<0)
#define BOUNCE_RACINGFAULTS     (1<<1)
#define BOUNCE_VERIFY           (1<<2)
#define BOUNCE_POLL             (1<<3)
static int bounces;

#define TEST_ANON       1
#define TEST_HUGETLB    2
#define TEST_SHMEM      3
static int test_type;

/* exercise the test_uffdio_*_eexist every ALARM_INTERVAL_SECS */
#define ALARM_INTERVAL_SECS 10
static volatile bool test_uffdio_copy_eexist = true;
static volatile bool test_uffdio_zeropage_eexist = true;
/* Whether to test uffd write-protection */
static bool test_uffdio_wp = false;
/* Whether to test uffd minor faults */
static bool test_uffdio_minor = false;

static bool map_shared;
static int shm_fd;
static int huge_fd;
static char *huge_fd_off0;
static unsigned long long *count_verify;
static int uffd = -1;
static int uffd_flags, finished, *pipefd;
static char *area_src, *area_src_alias, *area_dst, *area_dst_alias;
static char *zeropage;
pthread_attr_t attr;

/* Userfaultfd test statistics */
struct uffd_stats {
        int cpu;
        unsigned long missing_faults;
        unsigned long wp_faults;
        unsigned long minor_faults;
};

/* pthread_mutex_t starts at page offset 0 */
#define area_mutex(___area, ___nr)                                      \
        ((pthread_mutex_t *) ((___area) + (___nr)*page_size))
/*
 * count is placed in the page after pthread_mutex_t naturally aligned
 * to avoid non alignment faults on non-x86 archs.
 */
#define area_count(___area, ___nr)                                      \
        ((volatile unsigned long long *) ((unsigned long)               \
                                 ((___area) + (___nr)*page_size +       \
                                  sizeof(pthread_mutex_t) +             \
                                  sizeof(unsigned long long) - 1) &     \
                                 ~(unsigned long)(sizeof(unsigned long long) \
                                                  -  1)))

const char *examples =
    "# Run anonymous memory test on 100MiB region with 99999 bounces:\n"
    "./userfaultfd anon 100 99999\n\n"
    "# Run share memory test on 1GiB region with 99 bounces:\n"
    "./userfaultfd shmem 1000 99\n\n"
    "# Run hugetlb memory test on 256MiB region with 50 bounces (using /dev/hugepages/hugefile):\n"
    "./userfaultfd hugetlb 256 50 /dev/hugepages/hugefile\n\n"
    "# Run the same hugetlb test but using shmem:\n"
    "./userfaultfd hugetlb_shared 256 50 /dev/hugepages/hugefile\n\n"
    "# 10MiB-~6GiB 999 bounces anonymous test, "
    "continue forever unless an error triggers\n"
    "while ./userfaultfd anon $[RANDOM % 6000 + 10] 999; do true; done\n\n";

static void usage(void)
{
        fprintf(stderr, "\nUsage: ./userfaultfd <test type> <MiB> <bounces> "
                "[hugetlbfs_file]\n\n");
        fprintf(stderr, "Supported <test type>: anon, hugetlb, "
                "hugetlb_shared, shmem\n\n");
        fprintf(stderr, "Examples:\n\n");
        fprintf(stderr, "%s", examples);
        exit(1);
}

#define _err(fmt, ...)                                          \
        do {                                                    \
                int ret = errno;                                \
                fprintf(stderr, "ERROR: " fmt, ##__VA_ARGS__);  \
                fprintf(stderr, " (errno=%d, line=%d)\n",       \
                        ret, __LINE__);                         \
        } while (0)

#define err(fmt, ...)                           \
        do {                                    \
                _err(fmt, ##__VA_ARGS__);       \
                exit(1);                        \
        } while (0)

static void uffd_stats_reset(struct uffd_stats *uffd_stats,
                             unsigned long n_cpus)
{
        int i;

        for (i = 0; i < n_cpus; i++) {
                uffd_stats[i].cpu = i;
                uffd_stats[i].missing_faults = 0;
                uffd_stats[i].wp_faults = 0;
                uffd_stats[i].minor_faults = 0;
        }
}

static void uffd_stats_report(struct uffd_stats *stats, int n_cpus)
{
        int i;
        unsigned long long miss_total = 0, wp_total = 0, minor_total = 0;

        for (i = 0; i < n_cpus; i++) {
                miss_total += stats[i].missing_faults;
                wp_total += stats[i].wp_faults;
                minor_total += stats[i].minor_faults;
        }

        printf("userfaults: ");
        if (miss_total) {
                printf("%llu missing (", miss_total);
                for (i = 0; i < n_cpus; i++)
                        printf("%lu+", stats[i].missing_faults);
                printf("\b) ");
        }
        if (wp_total) {
                printf("%llu wp (", wp_total);
                for (i = 0; i < n_cpus; i++)
                        printf("%lu+", stats[i].wp_faults);
                printf("\b) ");
        }
        if (minor_total) {
                printf("%llu minor (", minor_total);
                for (i = 0; i < n_cpus; i++)
                        printf("%lu+", stats[i].minor_faults);
                printf("\b)");
        }
        printf("\n");
}

static void anon_release_pages(char *rel_area)
{
        if (madvise(rel_area, nr_pages * page_size, MADV_DONTNEED))
                err("madvise(MADV_DONTNEED) failed");
}

static void anon_allocate_area(void **alloc_area)
{
        *alloc_area = mmap(NULL, nr_pages * page_size, PROT_READ | PROT_WRITE,
                           MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
        if (*alloc_area == MAP_FAILED)
                err("mmap of anonymous memory failed");
}

static void noop_alias_mapping(__u64 *start, size_t len, unsigned long offset)
{
}

static void hugetlb_release_pages(char *rel_area)
{
        if (fallocate(huge_fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
                      rel_area == huge_fd_off0 ? 0 : nr_pages * page_size,
                      nr_pages * page_size))
                err("fallocate() failed");
}

static void hugetlb_allocate_area(void **alloc_area)
{
        void *area_alias = NULL;
        char **alloc_area_alias;

        *alloc_area = mmap(NULL, nr_pages * page_size, PROT_READ | PROT_WRITE,
                           (map_shared ? MAP_SHARED : MAP_PRIVATE) |
                           MAP_HUGETLB,
                           huge_fd, *alloc_area == area_src ? 0 :
                           nr_pages * page_size);
        if (*alloc_area == MAP_FAILED)
                err("mmap of hugetlbfs file failed");

        if (map_shared) {
                area_alias = mmap(NULL, nr_pages * page_size, PROT_READ | PROT_WRITE,
                                  MAP_SHARED | MAP_HUGETLB,
                                  huge_fd, *alloc_area == area_src ? 0 :
                                  nr_pages * page_size);
                if (area_alias == MAP_FAILED)
                        err("mmap of hugetlb file alias failed");
        }

        if (*alloc_area == area_src) {
                huge_fd_off0 = *alloc_area;
                alloc_area_alias = &area_src_alias;
        } else {
                alloc_area_alias = &area_dst_alias;
        }
        if (area_alias)
                *alloc_area_alias = area_alias;
}

static void hugetlb_alias_mapping(__u64 *start, size_t len, unsigned long offset)
{
        if (!map_shared)
                return;
        /*
         * We can't zap just the pagetable with hugetlbfs because
         * MADV_DONTEED won't work. So exercise -EEXIST on a alias
         * mapping where the pagetables are not established initially,
         * this way we'll exercise the -EEXEC at the fs level.
         */
        *start = (unsigned long) area_dst_alias + offset;
}

static void shmem_release_pages(char *rel_area)
{
        if (madvise(rel_area, nr_pages * page_size, MADV_REMOVE))
                err("madvise(MADV_REMOVE) failed");
}

static void shmem_allocate_area(void **alloc_area)
{
        void *area_alias = NULL;
        bool is_src = alloc_area == (void **)&area_src;
        unsigned long offset = is_src ? 0 : nr_pages * page_size;

        *alloc_area = mmap(NULL, nr_pages * page_size, PROT_READ | PROT_WRITE,
                           MAP_SHARED, shm_fd, offset);
        if (*alloc_area == MAP_FAILED)
                err("mmap of memfd failed");

        area_alias = mmap(NULL, nr_pages * page_size, PROT_READ | PROT_WRITE,
                          MAP_SHARED, shm_fd, offset);
        if (area_alias == MAP_FAILED)
                err("mmap of memfd alias failed");

        if (is_src)
                area_src_alias = area_alias;
        else
                area_dst_alias = area_alias;
}

static void shmem_alias_mapping(__u64 *start, size_t len, unsigned long offset)
{
        *start = (unsigned long)area_dst_alias + offset;
}

struct uffd_test_ops {
        unsigned long expected_ioctls;
        void (*allocate_area)(void **alloc_area);
        void (*release_pages)(char *rel_area);
        void (*alias_mapping)(__u64 *start, size_t len, unsigned long offset);
};

#define SHMEM_EXPECTED_IOCTLS           ((1 << _UFFDIO_WAKE) | \
                                         (1 << _UFFDIO_COPY) | \
                                         (1 << _UFFDIO_ZEROPAGE))

#define ANON_EXPECTED_IOCTLS            ((1 << _UFFDIO_WAKE) | \
                                         (1 << _UFFDIO_COPY) | \
                                         (1 << _UFFDIO_ZEROPAGE) | \
                                         (1 << _UFFDIO_WRITEPROTECT))

static struct uffd_test_ops anon_uffd_test_ops = {
        .expected_ioctls = ANON_EXPECTED_IOCTLS,
        .allocate_area  = anon_allocate_area,
        .release_pages  = anon_release_pages,
        .alias_mapping = noop_alias_mapping,
};

static struct uffd_test_ops shmem_uffd_test_ops = {
        .expected_ioctls = SHMEM_EXPECTED_IOCTLS,
        .allocate_area  = shmem_allocate_area,
        .release_pages  = shmem_release_pages,
        .alias_mapping = shmem_alias_mapping,
};

static struct uffd_test_ops hugetlb_uffd_test_ops = {
        .expected_ioctls = UFFD_API_RANGE_IOCTLS_BASIC & ~(1 << _UFFDIO_CONTINUE),
        .allocate_area  = hugetlb_allocate_area,
        .release_pages  = hugetlb_release_pages,
        .alias_mapping = hugetlb_alias_mapping,
};

static struct uffd_test_ops *uffd_test_ops;

static void userfaultfd_open(uint64_t *features)
{
        struct uffdio_api uffdio_api;

        uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK | UFFD_USER_MODE_ONLY);
        if (uffd < 0)
                err("userfaultfd syscall not available in this kernel");
        uffd_flags = fcntl(uffd, F_GETFD, NULL);

        uffdio_api.api = UFFD_API;
        uffdio_api.features = *features;
        if (ioctl(uffd, UFFDIO_API, &uffdio_api))
                err("UFFDIO_API failed.\nPlease make sure to "
                    "run with either root or ptrace capability.");
        if (uffdio_api.api != UFFD_API)
                err("UFFDIO_API error: %" PRIu64, (uint64_t)uffdio_api.api);

        *features = uffdio_api.features;
}

static inline void munmap_area(void **area)
{
        if (*area)
                if (munmap(*area, nr_pages * page_size))
                        err("munmap");

        *area = NULL;
}

static void uffd_test_ctx_clear(void)
{
        size_t i;

        if (pipefd) {
                for (i = 0; i < nr_cpus * 2; ++i) {
                        if (close(pipefd[i]))
                                err("close pipefd");
                }
                free(pipefd);
                pipefd = NULL;
        }

        if (count_verify) {
                free(count_verify);
                count_verify = NULL;
        }

        if (uffd != -1) {
                if (close(uffd))
                        err("close uffd");
                uffd = -1;
        }

        huge_fd_off0 = NULL;
        munmap_area((void **)&area_src);
        munmap_area((void **)&area_src_alias);
        munmap_area((void **)&area_dst);
        munmap_area((void **)&area_dst_alias);
}

static void uffd_test_ctx_init_ext(uint64_t *features)
{
        unsigned long nr, cpu;

        uffd_test_ctx_clear();

        uffd_test_ops->allocate_area((void **)&area_src);
        uffd_test_ops->allocate_area((void **)&area_dst);

        uffd_test_ops->release_pages(area_src);
        uffd_test_ops->release_pages(area_dst);

        userfaultfd_open(features);

        count_verify = malloc(nr_pages * sizeof(unsigned long long));
        if (!count_verify)
                err("count_verify");

        for (nr = 0; nr < nr_pages; nr++) {
                *area_mutex(area_src, nr) =
                        (pthread_mutex_t)PTHREAD_MUTEX_INITIALIZER;
                count_verify[nr] = *area_count(area_src, nr) = 1;
                /*
                 * In the transition between 255 to 256, powerpc will
                 * read out of order in my_bcmp and see both bytes as
                 * zero, so leave a placeholder below always non-zero
                 * after the count, to avoid my_bcmp to trigger false
                 * positives.
                 */
                *(area_count(area_src, nr) + 1) = 1;
        }

        pipefd = malloc(sizeof(int) * nr_cpus * 2);
        if (!pipefd)
                err("pipefd");
        for (cpu = 0; cpu < nr_cpus; cpu++)
                if (pipe2(&pipefd[cpu * 2], O_CLOEXEC | O_NONBLOCK))
                        err("pipe");
}

static inline void uffd_test_ctx_init(uint64_t features)
{
        uffd_test_ctx_init_ext(&features);
}

static int my_bcmp(char *str1, char *str2, size_t n)
{
        unsigned long i;
        for (i = 0; i < n; i++)
                if (str1[i] != str2[i])
                        return 1;
        return 0;
}

static void wp_range(int ufd, __u64 start, __u64 len, bool wp)
{
        struct uffdio_writeprotect prms;

        /* Write protection page faults */
        prms.range.start = start;
        prms.range.len = len;
        /* Undo write-protect, do wakeup after that */
        prms.mode = wp ? UFFDIO_WRITEPROTECT_MODE_WP : 0;

        if (ioctl(ufd, UFFDIO_WRITEPROTECT, &prms))
                err("clear WP failed: address=0x%"PRIx64, (uint64_t)start);
}

static void continue_range(int ufd, __u64 start, __u64 len)
{
        struct uffdio_continue req;
        int ret;

        req.range.start = start;
        req.range.len = len;
        req.mode = 0;

        if (ioctl(ufd, UFFDIO_CONTINUE, &req))
                err("UFFDIO_CONTINUE failed for address 0x%" PRIx64,
                    (uint64_t)start);

        /*
         * Error handling within the kernel for continue is subtly different
         * from copy or zeropage, so it may be a source of bugs. Trigger an
         * error (-EEXIST) on purpose, to verify doing so doesn't cause a BUG.
         */
        req.mapped = 0;
        ret = ioctl(ufd, UFFDIO_CONTINUE, &req);
        if (ret >= 0 || req.mapped != -EEXIST)
                err("failed to exercise UFFDIO_CONTINUE error handling, ret=%d, mapped=%" PRId64,
                    ret, (int64_t) req.mapped);
}

static void *locking_thread(void *arg)
{
        unsigned long cpu = (unsigned long) arg;
        struct random_data rand;
        unsigned long page_nr = *(&(page_nr)); /* uninitialized warning */
        int32_t rand_nr;
        unsigned long long count;
        char randstate[64];
        unsigned int seed;

        if (bounces & BOUNCE_RANDOM) {
                seed = (unsigned int) time(NULL) - bounces;
                if (!(bounces & BOUNCE_RACINGFAULTS))
                        seed += cpu;
                bzero(&rand, sizeof(rand));
                bzero(&randstate, sizeof(randstate));
                if (initstate_r(seed, randstate, sizeof(randstate), &rand))
                        err("initstate_r failed");
        } else {
                page_nr = -bounces;
                if (!(bounces & BOUNCE_RACINGFAULTS))
                        page_nr += cpu * nr_pages_per_cpu;
        }

        while (!finished) {
                if (bounces & BOUNCE_RANDOM) {
                        if (random_r(&rand, &rand_nr))
                                err("random_r failed");
                        page_nr = rand_nr;
                        if (sizeof(page_nr) > sizeof(rand_nr)) {
                                if (random_r(&rand, &rand_nr))
                                        err("random_r failed");
                                page_nr |= (((unsigned long) rand_nr) << 16) <<
                                           16;
                        }
                } else
                        page_nr += 1;
                page_nr %= nr_pages;
                pthread_mutex_lock(area_mutex(area_dst, page_nr));
                count = *area_count(area_dst, page_nr);
                if (count != count_verify[page_nr])
                        err("page_nr %lu memory corruption %llu %llu",
                            page_nr, count, count_verify[page_nr]);
                count++;
                *area_count(area_dst, page_nr) = count_verify[page_nr] = count;
                pthread_mutex_unlock(area_mutex(area_dst, page_nr));
        }

        return NULL;
}

static void retry_copy_page(int ufd, struct uffdio_copy *uffdio_copy,
                            unsigned long offset)
{
        uffd_test_ops->alias_mapping(&uffdio_copy->dst,
                                     uffdio_copy->len,
                                     offset);
        if (ioctl(ufd, UFFDIO_COPY, uffdio_copy)) {
                /* real retval in ufdio_copy.copy */
                if (uffdio_copy->copy != -EEXIST)
                        err("UFFDIO_COPY retry error: %"PRId64,
                            (int64_t)uffdio_copy->copy);
        } else {
                err("UFFDIO_COPY retry unexpected: %"PRId64,
                    (int64_t)uffdio_copy->copy);
        }
}

static int __copy_page(int ufd, unsigned long offset, bool retry)
{
        struct uffdio_copy uffdio_copy;

        if (offset >= nr_pages * page_size)
                err("unexpected offset %lu\n", offset);
        uffdio_copy.dst = (unsigned long) area_dst + offset;
        uffdio_copy.src = (unsigned long) area_src + offset;
        uffdio_copy.len = page_size;
        if (test_uffdio_wp)
                uffdio_copy.mode = UFFDIO_COPY_MODE_WP;
        else
                uffdio_copy.mode = 0;
        uffdio_copy.copy = 0;
        if (ioctl(ufd, UFFDIO_COPY, &uffdio_copy)) {
                /* real retval in ufdio_copy.copy */
                if (uffdio_copy.copy != -EEXIST)
                        err("UFFDIO_COPY error: %"PRId64,
                            (int64_t)uffdio_copy.copy);
        } else if (uffdio_copy.copy != page_size) {
                err("UFFDIO_COPY error: %"PRId64, (int64_t)uffdio_copy.copy);
        } else {
                if (test_uffdio_copy_eexist && retry) {
                        test_uffdio_copy_eexist = false;
                        retry_copy_page(ufd, &uffdio_copy, offset);
                }
                return 1;
        }
        return 0;
}

static int copy_page_retry(int ufd, unsigned long offset)
{
        return __copy_page(ufd, offset, true);
}

static int copy_page(int ufd, unsigned long offset)
{
        return __copy_page(ufd, offset, false);
}

static int uffd_read_msg(int ufd, struct uffd_msg *msg)
{
        int ret = read(uffd, msg, sizeof(*msg));

        if (ret != sizeof(*msg)) {
                if (ret < 0) {
                        if (errno == EAGAIN)
                                return 1;
                        err("blocking read error");
                } else {
                        err("short read");
                }
        }

        return 0;
}

static void uffd_handle_page_fault(struct uffd_msg *msg,
                                   struct uffd_stats *stats)
{
        unsigned long offset;

        if (msg->event != UFFD_EVENT_PAGEFAULT)
                err("unexpected msg event %u", msg->event);

        if (msg->arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_WP) {
                /* Write protect page faults */
                wp_range(uffd, msg->arg.pagefault.address, page_size, false);
                stats->wp_faults++;
        } else if (msg->arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_MINOR) {
                uint8_t *area;
                int b;

                /*
                 * Minor page faults
                 *
                 * To prove we can modify the original range for testing
                 * purposes, we're going to bit flip this range before
                 * continuing.
                 *
                 * Note that this requires all minor page fault tests operate on
                 * area_dst (non-UFFD-registered) and area_dst_alias
                 * (UFFD-registered).
                 */

                area = (uint8_t *)(area_dst +
                                   ((char *)msg->arg.pagefault.address -
                                    area_dst_alias));
                for (b = 0; b < page_size; ++b)
                        area[b] = ~area[b];
                continue_range(uffd, msg->arg.pagefault.address, page_size);
                stats->minor_faults++;
        } else {
                /* Missing page faults */
                if (msg->arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_WRITE)
                        err("unexpected write fault");

                offset = (char *)(unsigned long)msg->arg.pagefault.address - area_dst;
                offset &= ~(page_size-1);

                if (copy_page(uffd, offset))
                        stats->missing_faults++;
        }
}

static void *uffd_poll_thread(void *arg)
{
        struct uffd_stats *stats = (struct uffd_stats *)arg;
        unsigned long cpu = stats->cpu;
        struct pollfd pollfd[2];
        struct uffd_msg msg;
        struct uffdio_register uffd_reg;
        int ret;
        char tmp_chr;

        pollfd[0].fd = uffd;
        pollfd[0].events = POLLIN;
        pollfd[1].fd = pipefd[cpu*2];
        pollfd[1].events = POLLIN;

        for (;;) {
                ret = poll(pollfd, 2, -1);
                if (ret <= 0)
                        err("poll error: %d", ret);
                if (pollfd[1].revents & POLLIN) {
                        if (read(pollfd[1].fd, &tmp_chr, 1) != 1)
                                err("read pipefd error");
                        break;
                }
                if (!(pollfd[0].revents & POLLIN))
                        err("pollfd[0].revents %d", pollfd[0].revents);
                if (uffd_read_msg(uffd, &msg))
                        continue;
                switch (msg.event) {
                default:
                        err("unexpected msg event %u\n", msg.event);
                        break;
                case UFFD_EVENT_PAGEFAULT:
                        uffd_handle_page_fault(&msg, stats);
                        break;
                case UFFD_EVENT_FORK:
                        close(uffd);
                        uffd = msg.arg.fork.ufd;
                        pollfd[0].fd = uffd;
                        break;
                case UFFD_EVENT_REMOVE:
                        uffd_reg.range.start = msg.arg.remove.start;
                        uffd_reg.range.len = msg.arg.remove.end -
                                msg.arg.remove.start;
                        if (ioctl(uffd, UFFDIO_UNREGISTER, &uffd_reg.range))
                                err("remove failure");
                        break;
                case UFFD_EVENT_REMAP:
                        area_dst = (char *)(unsigned long)msg.arg.remap.to;
                        break;
                }
        }

        return NULL;
}

pthread_mutex_t uffd_read_mutex = PTHREAD_MUTEX_INITIALIZER;

static void *uffd_read_thread(void *arg)
{
        struct uffd_stats *stats = (struct uffd_stats *)arg;
        struct uffd_msg msg;

        pthread_mutex_unlock(&uffd_read_mutex);
        /* from here cancellation is ok */

        for (;;) {
                if (uffd_read_msg(uffd, &msg))
                        continue;
                uffd_handle_page_fault(&msg, stats);
        }

        return NULL;
}

static void *background_thread(void *arg)
{
        unsigned long cpu = (unsigned long) arg;
        unsigned long page_nr, start_nr, mid_nr, end_nr;

        start_nr = cpu * nr_pages_per_cpu;
        end_nr = (cpu+1) * nr_pages_per_cpu;
        mid_nr = (start_nr + end_nr) / 2;

        /* Copy the first half of the pages */
        for (page_nr = start_nr; page_nr < mid_nr; page_nr++)
                copy_page_retry(uffd, page_nr * page_size);

        /*
         * If we need to test uffd-wp, set it up now.  Then we'll have
         * at least the first half of the pages mapped already which
         * can be write-protected for testing
         */
        if (test_uffdio_wp)
                wp_range(uffd, (unsigned long)area_dst + start_nr * page_size,
                        nr_pages_per_cpu * page_size, true);

        /*
         * Continue the 2nd half of the page copying, handling write
         * protection faults if any
         */
        for (page_nr = mid_nr; page_nr < end_nr; page_nr++)
                copy_page_retry(uffd, page_nr * page_size);

        return NULL;
}

static int stress(struct uffd_stats *uffd_stats)
{
        unsigned long cpu;
        pthread_t locking_threads[nr_cpus];
        pthread_t uffd_threads[nr_cpus];
        pthread_t background_threads[nr_cpus];

        finished = 0;
        for (cpu = 0; cpu < nr_cpus; cpu++) {
                if (pthread_create(&locking_threads[cpu], &attr,
                                   locking_thread, (void *)cpu))
                        return 1;
                if (bounces & BOUNCE_POLL) {
                        if (pthread_create(&uffd_threads[cpu], &attr,
                                           uffd_poll_thread,
                                           (void *)&uffd_stats[cpu]))
                                return 1;
                } else {
                        if (pthread_create(&uffd_threads[cpu], &attr,
                                           uffd_read_thread,
                                           (void *)&uffd_stats[cpu]))
                                return 1;
                        pthread_mutex_lock(&uffd_read_mutex);
                }
                if (pthread_create(&background_threads[cpu], &attr,
                                   background_thread, (void *)cpu))
                        return 1;
        }
        for (cpu = 0; cpu < nr_cpus; cpu++)
                if (pthread_join(background_threads[cpu], NULL))
                        return 1;

        /*
         * Be strict and immediately zap area_src, the whole area has
         * been transferred already by the background treads. The
         * area_src could then be faulted in in a racy way by still
         * running uffdio_threads reading zeropages after we zapped
         * area_src (but they're guaranteed to get -EEXIST from
         * UFFDIO_COPY without writing zero pages into area_dst
         * because the background threads already completed).
         */
        uffd_test_ops->release_pages(area_src);

        finished = 1;
        for (cpu = 0; cpu < nr_cpus; cpu++)
                if (pthread_join(locking_threads[cpu], NULL))
                        return 1;

        for (cpu = 0; cpu < nr_cpus; cpu++) {
                char c;
                if (bounces & BOUNCE_POLL) {
                        if (write(pipefd[cpu*2+1], &c, 1) != 1)
                                err("pipefd write error");
                        if (pthread_join(uffd_threads[cpu],
                                         (void *)&uffd_stats[cpu]))
                                return 1;
                } else {
                        if (pthread_cancel(uffd_threads[cpu]))
                                return 1;
                        if (pthread_join(uffd_threads[cpu], NULL))
                                return 1;
                }
        }

        return 0;
}

sigjmp_buf jbuf, *sigbuf;

static void sighndl(int sig, siginfo_t *siginfo, void *ptr)
{
        if (sig == SIGBUS) {
                if (sigbuf)
                        siglongjmp(*sigbuf, 1);
                abort();
        }
}

/*
 * For non-cooperative userfaultfd test we fork() a process that will
 * generate pagefaults, will mremap the area monitored by the
 * userfaultfd and at last this process will release the monitored
 * area.
 * For the anonymous and shared memory the area is divided into two
 * parts, the first part is accessed before mremap, and the second
 * part is accessed after mremap. Since hugetlbfs does not support
 * mremap, the entire monitored area is accessed in a single pass for
 * HUGETLB_TEST.
 * The release of the pages currently generates event for shmem and
 * anonymous memory (UFFD_EVENT_REMOVE), hence it is not checked
 * for hugetlb.
 * For signal test(UFFD_FEATURE_SIGBUS), signal_test = 1, we register
 * monitored area, generate pagefaults and test that signal is delivered.
 * Use UFFDIO_COPY to allocate missing page and retry. For signal_test = 2
 * test robustness use case - we release monitored area, fork a process
 * that will generate pagefaults and verify signal is generated.
 * This also tests UFFD_FEATURE_EVENT_FORK event along with the signal
 * feature. Using monitor thread, verify no userfault events are generated.
 */
static int faulting_process(int signal_test)
{
        unsigned long nr;
        unsigned long long count;
        unsigned long split_nr_pages;
        unsigned long lastnr;
        struct sigaction act;
        unsigned long signalled = 0;

        if (test_type != TEST_HUGETLB)
                split_nr_pages = (nr_pages + 1) / 2;
        else
                split_nr_pages = nr_pages;

        if (signal_test) {
                sigbuf = &jbuf;
                memset(&act, 0, sizeof(act));
                act.sa_sigaction = sighndl;
                act.sa_flags = SA_SIGINFO;
                if (sigaction(SIGBUS, &act, 0))
                        err("sigaction");
                lastnr = (unsigned long)-1;
        }

        for (nr = 0; nr < split_nr_pages; nr++) {
                int steps = 1;
                unsigned long offset = nr * page_size;

                if (signal_test) {
                        if (sigsetjmp(*sigbuf, 1) != 0) {
                                if (steps == 1 && nr == lastnr)
                                        err("Signal repeated");

                                lastnr = nr;
                                if (signal_test == 1) {
                                        if (steps == 1) {
                                                /* This is a MISSING request */
                                                steps++;
                                                if (copy_page(uffd, offset))
                                                        signalled++;
                                        } else {
                                                /* This is a WP request */
                                                assert(steps == 2);
                                                wp_range(uffd,
                                                         (__u64)area_dst +
                                                         offset,
                                                         page_size, false);
                                        }
                                } else {
                                        signalled++;
                                        continue;
                                }
                        }
                }

                count = *area_count(area_dst, nr);
                if (count != count_verify[nr])
                        err("nr %lu memory corruption %llu %llu\n",
                            nr, count, count_verify[nr]);
                /*
                 * Trigger write protection if there is by writing
                 * the same value back.
                 */
                *area_count(area_dst, nr) = count;
        }

        if (signal_test)
                return signalled != split_nr_pages;

        if (test_type == TEST_HUGETLB)
                return 0;

        area_dst = mremap(area_dst, nr_pages * page_size,  nr_pages * page_size,
                          MREMAP_MAYMOVE | MREMAP_FIXED, area_src);
        if (area_dst == MAP_FAILED)
                err("mremap");
        /* Reset area_src since we just clobbered it */
        area_src = NULL;

        for (; nr < nr_pages; nr++) {
                count = *area_count(area_dst, nr);
                if (count != count_verify[nr]) {
                        err("nr %lu memory corruption %llu %llu\n",
                            nr, count, count_verify[nr]);
                }
                /*
                 * Trigger write protection if there is by writing
                 * the same value back.
                 */
                *area_count(area_dst, nr) = count;
        }

        uffd_test_ops->release_pages(area_dst);

        for (nr = 0; nr < nr_pages; nr++)
                if (my_bcmp(area_dst + nr * page_size, zeropage, page_size))
                        err("nr %lu is not zero", nr);

        return 0;
}

static void retry_uffdio_zeropage(int ufd,
                                  struct uffdio_zeropage *uffdio_zeropage,
                                  unsigned long offset)
{
        uffd_test_ops->alias_mapping(&uffdio_zeropage->range.start,
                                     uffdio_zeropage->range.len,
                                     offset);
        if (ioctl(ufd, UFFDIO_ZEROPAGE, uffdio_zeropage)) {
                if (uffdio_zeropage->zeropage != -EEXIST)
                        err("UFFDIO_ZEROPAGE error: %"PRId64,
                            (int64_t)uffdio_zeropage->zeropage);
        } else {
                err("UFFDIO_ZEROPAGE error: %"PRId64,
                    (int64_t)uffdio_zeropage->zeropage);
        }
}

static int __uffdio_zeropage(int ufd, unsigned long offset, bool retry)
{

        struct uffdio_zeropage uffdio_zeropage;
        int ret;
        unsigned long has_zeropage;
        __s64 res;

        has_zeropage = uffd_test_ops->expected_ioctls & (1 << _UFFDIO_ZEROPAGE);

        if (offset >= nr_pages * page_size)
                err("unexpected offset %lu", offset);
        uffdio_zeropage.range.start = (unsigned long) area_dst + offset;
        uffdio_zeropage.range.len = page_size;
        uffdio_zeropage.mode = 0;
        ret = ioctl(ufd, UFFDIO_ZEROPAGE, &uffdio_zeropage);
        res = uffdio_zeropage.zeropage;
        if (ret) {
                /* real retval in ufdio_zeropage.zeropage */
                if (has_zeropage)
                        err("UFFDIO_ZEROPAGE error: %"PRId64, (int64_t)res);
                else if (res != -EINVAL)
                        err("UFFDIO_ZEROPAGE not -EINVAL");
        } else if (has_zeropage) {
                if (res != page_size) {
                        err("UFFDIO_ZEROPAGE unexpected size");
                } else {
                        if (test_uffdio_zeropage_eexist && retry) {
                                test_uffdio_zeropage_eexist = false;
                                retry_uffdio_zeropage(ufd, &uffdio_zeropage,
                                                      offset);
                        }
                        return 1;
                }
        } else
                err("UFFDIO_ZEROPAGE succeeded");

        return 0;
}

static int uffdio_zeropage(int ufd, unsigned long offset)
{
        return __uffdio_zeropage(ufd, offset, false);
}

/* exercise UFFDIO_ZEROPAGE */
static int userfaultfd_zeropage_test(void)
{
        struct uffdio_register uffdio_register;
        unsigned long expected_ioctls;

        printf("testing UFFDIO_ZEROPAGE: ");
        fflush(stdout);

        uffd_test_ctx_init(0);

        uffdio_register.range.start = (unsigned long) area_dst;
        uffdio_register.range.len = nr_pages * page_size;
        uffdio_register.mode = UFFDIO_REGISTER_MODE_MISSING;
        if (test_uffdio_wp)
                uffdio_register.mode |= UFFDIO_REGISTER_MODE_WP;
        if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register))
                err("register failure");

        expected_ioctls = uffd_test_ops->expected_ioctls;
        if ((uffdio_register.ioctls & expected_ioctls) != expected_ioctls)
                err("unexpected missing ioctl for anon memory");

        if (uffdio_zeropage(uffd, 0))
                if (my_bcmp(area_dst, zeropage, page_size))
                        err("zeropage is not zero");

        printf("done.\n");
        return 0;
}

static int userfaultfd_events_test(void)
{
        struct uffdio_register uffdio_register;
        unsigned long expected_ioctls;
        pthread_t uffd_mon;
        int err, features;
        pid_t pid;
        char c;
        struct uffd_stats stats = { 0 };

        printf("testing events (fork, remap, remove): ");
        fflush(stdout);

        features = UFFD_FEATURE_EVENT_FORK | UFFD_FEATURE_EVENT_REMAP |
                UFFD_FEATURE_EVENT_REMOVE;
        uffd_test_ctx_init(features);

        fcntl(uffd, F_SETFL, uffd_flags | O_NONBLOCK);

        uffdio_register.range.start = (unsigned long) area_dst;
        uffdio_register.range.len = nr_pages * page_size;
        uffdio_register.mode = UFFDIO_REGISTER_MODE_MISSING;
        if (test_uffdio_wp)
                uffdio_register.mode |= UFFDIO_REGISTER_MODE_WP;
        if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register))
                err("register failure");

        expected_ioctls = uffd_test_ops->expected_ioctls;
        if ((uffdio_register.ioctls & expected_ioctls) != expected_ioctls)
                err("unexpected missing ioctl for anon memory");

        if (pthread_create(&uffd_mon, &attr, uffd_poll_thread, &stats))
                err("uffd_poll_thread create");

        pid = fork();
        if (pid < 0)
                err("fork");

        if (!pid)
                exit(faulting_process(0));

        waitpid(pid, &err, 0);
        if (err)
                err("faulting process failed");
        if (write(pipefd[1], &c, sizeof(c)) != sizeof(c))
                err("pipe write");
        if (pthread_join(uffd_mon, NULL))
                return 1;

        uffd_stats_report(&stats, 1);

        return stats.missing_faults != nr_pages;
}

static int userfaultfd_sig_test(void)
{
        struct uffdio_register uffdio_register;
        unsigned long expected_ioctls;
        unsigned long userfaults;
        pthread_t uffd_mon;
        int err, features;
        pid_t pid;
        char c;
        struct uffd_stats stats = { 0 };

        printf("testing signal delivery: ");
        fflush(stdout);

        features = UFFD_FEATURE_EVENT_FORK|UFFD_FEATURE_SIGBUS;
        uffd_test_ctx_init(features);

        fcntl(uffd, F_SETFL, uffd_flags | O_NONBLOCK);

        uffdio_register.range.start = (unsigned long) area_dst;
        uffdio_register.range.len = nr_pages * page_size;
        uffdio_register.mode = UFFDIO_REGISTER_MODE_MISSING;
        if (test_uffdio_wp)
                uffdio_register.mode |= UFFDIO_REGISTER_MODE_WP;
        if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register))
                err("register failure");

        expected_ioctls = uffd_test_ops->expected_ioctls;
        if ((uffdio_register.ioctls & expected_ioctls) != expected_ioctls)
                err("unexpected missing ioctl for anon memory");

        if (faulting_process(1))
                err("faulting process failed");

        uffd_test_ops->release_pages(area_dst);

        if (pthread_create(&uffd_mon, &attr, uffd_poll_thread, &stats))
                err("uffd_poll_thread create");

        pid = fork();
        if (pid < 0)
                err("fork");

        if (!pid)
                exit(faulting_process(2));

        waitpid(pid, &err, 0);
        if (err)
                err("faulting process failed");
        if (write(pipefd[1], &c, sizeof(c)) != sizeof(c))
                err("pipe write");
        if (pthread_join(uffd_mon, (void **)&userfaults))
                return 1;

        printf("done.\n");
        if (userfaults)
                err("Signal test failed, userfaults: %ld", userfaults);

        return userfaults != 0;
}

static int userfaultfd_minor_test(void)
{
        struct uffdio_register uffdio_register;
        unsigned long expected_ioctls;
        unsigned long p;
        pthread_t uffd_mon;
        uint8_t expected_byte;
        void *expected_page;
        char c;
        struct uffd_stats stats = { 0 };
        uint64_t req_features, features_out;

        if (!test_uffdio_minor)
                return 0;

        printf("testing minor faults: ");
        fflush(stdout);

        if (test_type == TEST_HUGETLB)
                req_features = UFFD_FEATURE_MINOR_HUGETLBFS;
        else if (test_type == TEST_SHMEM)
                req_features = UFFD_FEATURE_MINOR_SHMEM;
        else
                return 1;

        features_out = req_features;
        uffd_test_ctx_init_ext(&features_out);
        /* If kernel reports required features aren't supported, skip test. */
        if ((features_out & req_features) != req_features) {
                printf("skipping test due to lack of feature support\n");
                fflush(stdout);
                return 0;
        }

        uffdio_register.range.start = (unsigned long)area_dst_alias;
        uffdio_register.range.len = nr_pages * page_size;
        uffdio_register.mode = UFFDIO_REGISTER_MODE_MINOR;
        if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register))
                err("register failure");

        expected_ioctls = uffd_test_ops->expected_ioctls;
        expected_ioctls |= 1 << _UFFDIO_CONTINUE;
        if ((uffdio_register.ioctls & expected_ioctls) != expected_ioctls)
                err("unexpected missing ioctl(s)");

        /*
         * After registering with UFFD, populate the non-UFFD-registered side of
         * the shared mapping. This should *not* trigger any UFFD minor faults.
         */
        for (p = 0; p < nr_pages; ++p) {
                memset(area_dst + (p * page_size), p % ((uint8_t)-1),
                       page_size);
        }

        if (pthread_create(&uffd_mon, &attr, uffd_poll_thread, &stats))
                err("uffd_poll_thread create");

        /*
         * Read each of the pages back using the UFFD-registered mapping. We
         * expect that the first time we touch a page, it will result in a minor
         * fault. uffd_poll_thread will resolve the fault by bit-flipping the
         * page's contents, and then issuing a CONTINUE ioctl.
         */

        if (posix_memalign(&expected_page, page_size, page_size))
                err("out of memory");

        for (p = 0; p < nr_pages; ++p) {
                expected_byte = ~((uint8_t)(p % ((uint8_t)-1)));
                memset(expected_page, expected_byte, page_size);
                if (my_bcmp(expected_page, area_dst_alias + (p * page_size),
                            page_size))
                        err("unexpected page contents after minor fault");
        }

        if (write(pipefd[1], &c, sizeof(c)) != sizeof(c))
                err("pipe write");
        if (pthread_join(uffd_mon, NULL))
                return 1;

        uffd_stats_report(&stats, 1);

        return stats.missing_faults != 0 || stats.minor_faults != nr_pages;
}

#define BIT_ULL(nr)                   (1ULL << (nr))
#define PM_SOFT_DIRTY                 BIT_ULL(55)
#define PM_MMAP_EXCLUSIVE             BIT_ULL(56)
#define PM_UFFD_WP                    BIT_ULL(57)
#define PM_FILE                       BIT_ULL(61)
#define PM_SWAP                       BIT_ULL(62)
#define PM_PRESENT                    BIT_ULL(63)

static int pagemap_open(void)
{
        int fd = open("/proc/self/pagemap", O_RDONLY);

        if (fd < 0)
                err("open pagemap");

        return fd;
}

static uint64_t pagemap_read_vaddr(int fd, void *vaddr)
{
        uint64_t value;
        int ret;

        ret = pread(fd, &value, sizeof(uint64_t),
                    ((uint64_t)vaddr >> 12) * sizeof(uint64_t));
        if (ret != sizeof(uint64_t))
                err("pread() on pagemap failed");

        return value;
}

/* This macro let __LINE__ works in err() */
#define  pagemap_check_wp(value, wp) do {                               \
                if (!!(value & PM_UFFD_WP) != wp)                       \
                        err("pagemap uffd-wp bit error: 0x%"PRIx64, value); \
        } while (0)

static int pagemap_test_fork(bool present)
{
        pid_t child = fork();
        uint64_t value;
        int fd, result;

        if (!child) {
                /* Open the pagemap fd of the child itself */
                fd = pagemap_open();
                value = pagemap_read_vaddr(fd, area_dst);
                /*
                 * After fork() uffd-wp bit should be gone as long as we're
                 * without UFFD_FEATURE_EVENT_FORK
                 */
                pagemap_check_wp(value, false);
                /* Succeed */
                exit(0);
        }
        waitpid(child, &result, 0);
        return result;
}

static void userfaultfd_pagemap_test(unsigned int test_pgsize)
{
        struct uffdio_register uffdio_register;
        int pagemap_fd;
        uint64_t value;

        /* Pagemap tests uffd-wp only */
        if (!test_uffdio_wp)
                return;

        /* Not enough memory to test this page size */
        if (test_pgsize > nr_pages * page_size)
                return;

        printf("testing uffd-wp with pagemap (pgsize=%u): ", test_pgsize);
        /* Flush so it doesn't flush twice in parent/child later */
        fflush(stdout);

        uffd_test_ctx_init(0);

        if (test_pgsize > page_size) {
                /* This is a thp test */
                if (madvise(area_dst, nr_pages * page_size, MADV_HUGEPAGE))
                        err("madvise(MADV_HUGEPAGE) failed");
        } else if (test_pgsize == page_size) {
                /* This is normal page test; force no thp */
                if (madvise(area_dst, nr_pages * page_size, MADV_NOHUGEPAGE))
                        err("madvise(MADV_NOHUGEPAGE) failed");
        }

        uffdio_register.range.start = (unsigned long) area_dst;
        uffdio_register.range.len = nr_pages * page_size;
        uffdio_register.mode = UFFDIO_REGISTER_MODE_WP;
        if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register))
                err("register failed");

        pagemap_fd = pagemap_open();

        /* Touch the page */
        *area_dst = 1;
        wp_range(uffd, (uint64_t)area_dst, test_pgsize, true);
        value = pagemap_read_vaddr(pagemap_fd, area_dst);
        pagemap_check_wp(value, true);
        /* Make sure uffd-wp bit dropped when fork */
        if (pagemap_test_fork(true))
                err("Detected stall uffd-wp bit in child");

        /* Exclusive required or PAGEOUT won't work */
        if (!(value & PM_MMAP_EXCLUSIVE))
                err("multiple mapping detected: 0x%"PRIx64, value);

        if (madvise(area_dst, test_pgsize, MADV_PAGEOUT))
                err("madvise(MADV_PAGEOUT) failed");

        /* Uffd-wp should persist even swapped out */
        value = pagemap_read_vaddr(pagemap_fd, area_dst);
        pagemap_check_wp(value, true);
        /* Make sure uffd-wp bit dropped when fork */
        if (pagemap_test_fork(false))
                err("Detected stall uffd-wp bit in child");

        /* Unprotect; this tests swap pte modifications */
        wp_range(uffd, (uint64_t)area_dst, page_size, false);
        value = pagemap_read_vaddr(pagemap_fd, area_dst);
        pagemap_check_wp(value, false);

        /* Fault in the page from disk */
        *area_dst = 2;
        value = pagemap_read_vaddr(pagemap_fd, area_dst);
        pagemap_check_wp(value, false);

        close(pagemap_fd);
        printf("done\n");
}

static int userfaultfd_stress(void)
{
        void *area;
        char *tmp_area;
        unsigned long nr;
        struct uffdio_register uffdio_register;
        struct uffd_stats uffd_stats[nr_cpus];

        uffd_test_ctx_init(0);

        if (posix_memalign(&area, page_size, page_size))
                err("out of memory");
        zeropage = area;
        bzero(zeropage, page_size);

        pthread_mutex_lock(&uffd_read_mutex);

        pthread_attr_init(&attr);
        pthread_attr_setstacksize(&attr, 16*1024*1024);

        while (bounces--) {
                unsigned long expected_ioctls;

                printf("bounces: %d, mode:", bounces);
                if (bounces & BOUNCE_RANDOM)
                        printf(" rnd");
                if (bounces & BOUNCE_RACINGFAULTS)
                        printf(" racing");
                if (bounces & BOUNCE_VERIFY)
                        printf(" ver");
                if (bounces & BOUNCE_POLL)
                        printf(" poll");
                else
                        printf(" read");
                printf(", ");
                fflush(stdout);

                if (bounces & BOUNCE_POLL)
                        fcntl(uffd, F_SETFL, uffd_flags | O_NONBLOCK);
                else
                        fcntl(uffd, F_SETFL, uffd_flags & ~O_NONBLOCK);

                /* register */
                uffdio_register.range.start = (unsigned long) area_dst;
                uffdio_register.range.len = nr_pages * page_size;
                uffdio_register.mode = UFFDIO_REGISTER_MODE_MISSING;
                if (test_uffdio_wp)
                        uffdio_register.mode |= UFFDIO_REGISTER_MODE_WP;
                if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register))
                        err("register failure");
                expected_ioctls = uffd_test_ops->expected_ioctls;
                if ((uffdio_register.ioctls & expected_ioctls) !=
                    expected_ioctls)
                        err("unexpected missing ioctl for anon memory");

                if (area_dst_alias) {
                        uffdio_register.range.start = (unsigned long)
                                area_dst_alias;
                        if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register))
                                err("register failure alias");
                }

                /*
                 * The madvise done previously isn't enough: some
                 * uffd_thread could have read userfaults (one of
                 * those already resolved by the background thread)
                 * and it may be in the process of calling
                 * UFFDIO_COPY. UFFDIO_COPY will read the zapped
                 * area_src and it would map a zero page in it (of
                 * course such a UFFDIO_COPY is perfectly safe as it'd
                 * return -EEXIST). The problem comes at the next
                 * bounce though: that racing UFFDIO_COPY would
                 * generate zeropages in the area_src, so invalidating
                 * the previous MADV_DONTNEED. Without this additional
                 * MADV_DONTNEED those zeropages leftovers in the
                 * area_src would lead to -EEXIST failure during the
                 * next bounce, effectively leaving a zeropage in the
                 * area_dst.
                 *
                 * Try to comment this out madvise to see the memory
                 * corruption being caught pretty quick.
                 *
                 * khugepaged is also inhibited to collapse THP after
                 * MADV_DONTNEED only after the UFFDIO_REGISTER, so it's
                 * required to MADV_DONTNEED here.
                 */
                uffd_test_ops->release_pages(area_dst);

                uffd_stats_reset(uffd_stats, nr_cpus);

                /* bounce pass */
                if (stress(uffd_stats))
                        return 1;

                /* Clear all the write protections if there is any */
                if (test_uffdio_wp)
                        wp_range(uffd, (unsigned long)area_dst,
                                 nr_pages * page_size, false);

                /* unregister */
                if (ioctl(uffd, UFFDIO_UNREGISTER, &uffdio_register.range))
                        err("unregister failure");
                if (area_dst_alias) {
                        uffdio_register.range.start = (unsigned long) area_dst;
                        if (ioctl(uffd, UFFDIO_UNREGISTER,
                                  &uffdio_register.range))
                                err("unregister failure alias");
                }

                /* verification */
                if (bounces & BOUNCE_VERIFY)
                        for (nr = 0; nr < nr_pages; nr++)
                                if (*area_count(area_dst, nr) != count_verify[nr])
                                        err("error area_count %llu %llu %lu\n",
                                            *area_count(area_src, nr),
                                            count_verify[nr], nr);

                /* prepare next bounce */
                tmp_area = area_src;
                area_src = area_dst;
                area_dst = tmp_area;

                tmp_area = area_src_alias;
                area_src_alias = area_dst_alias;
                area_dst_alias = tmp_area;

                uffd_stats_report(uffd_stats, nr_cpus);
        }

        if (test_type == TEST_ANON) {
                /*
                 * shmem/hugetlb won't be able to run since they have different
                 * behavior on fork() (file-backed memory normally drops ptes
                 * directly when fork), meanwhile the pagemap test will verify
                 * pgtable entry of fork()ed child.
                 */
                userfaultfd_pagemap_test(page_size);
                /*
                 * Hard-code for x86_64 for now for 2M THP, as x86_64 is
                 * currently the only one that supports uffd-wp
                 */
                userfaultfd_pagemap_test(page_size * 512);
        }

        return userfaultfd_zeropage_test() || userfaultfd_sig_test()
                || userfaultfd_events_test() || userfaultfd_minor_test();
}

/*
 * Copied from mlock2-tests.c
 */
unsigned long default_huge_page_size(void)
{
        unsigned long hps = 0;
        char *line = NULL;
        size_t linelen = 0;
        FILE *f = fopen("/proc/meminfo", "r");

        if (!f)
                return 0;
        while (getline(&line, &linelen, f) > 0) {
                if (sscanf(line, "Hugepagesize:       %lu kB", &hps) == 1) {
                        hps <<= 10;
                        break;
                }
        }

        free(line);
        fclose(f);
        return hps;
}

static void set_test_type(const char *type)
{
        if (!strcmp(type, "anon")) {
                test_type = TEST_ANON;
                uffd_test_ops = &anon_uffd_test_ops;
                /* Only enable write-protect test for anonymous test */
                test_uffdio_wp = true;
        } else if (!strcmp(type, "hugetlb")) {
                test_type = TEST_HUGETLB;
                uffd_test_ops = &hugetlb_uffd_test_ops;
        } else if (!strcmp(type, "hugetlb_shared")) {
                map_shared = true;
                test_type = TEST_HUGETLB;
                uffd_test_ops = &hugetlb_uffd_test_ops;
                /* Minor faults require shared hugetlb; only enable here. */
                test_uffdio_minor = true;
        } else if (!strcmp(type, "shmem")) {
                map_shared = true;
                test_type = TEST_SHMEM;
                uffd_test_ops = &shmem_uffd_test_ops;
                test_uffdio_minor = true;
        } else {
                err("Unknown test type: %s", type);
        }

        if (test_type == TEST_HUGETLB)
                page_size = default_huge_page_size();
        else
                page_size = sysconf(_SC_PAGE_SIZE);

        if (!page_size)
                err("Unable to determine page size");
        if ((unsigned long) area_count(NULL, 0) + sizeof(unsigned long long) * 2
            > page_size)
                err("Impossible to run this test");
}

static void sigalrm(int sig)
{
        if (sig != SIGALRM)
                abort();
        test_uffdio_copy_eexist = true;
        test_uffdio_zeropage_eexist = true;
        alarm(ALARM_INTERVAL_SECS);
}

int main(int argc, char **argv)
{
        if (argc < 4)
                usage();

        if (signal(SIGALRM, sigalrm) == SIG_ERR)
                err("failed to arm SIGALRM");
        alarm(ALARM_INTERVAL_SECS);

        set_test_type(argv[1]);

        nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
        nr_pages_per_cpu = atol(argv[2]) * 1024*1024 / page_size /
                nr_cpus;
        if (!nr_pages_per_cpu) {
                _err("invalid MiB");
                usage();
        }

        bounces = atoi(argv[3]);
        if (bounces <= 0) {
                _err("invalid bounces");
                usage();
        }
        nr_pages = nr_pages_per_cpu * nr_cpus;

        if (test_type == TEST_HUGETLB) {
                if (argc < 5)
                        usage();
                huge_fd = open(argv[4], O_CREAT | O_RDWR, 0755);
                if (huge_fd < 0)
                        err("Open of %s failed", argv[4]);
                if (ftruncate(huge_fd, 0))
                        err("ftruncate %s to size 0 failed", argv[4]);
        } else if (test_type == TEST_SHMEM) {
                shm_fd = memfd_create(argv[0], 0);
                if (shm_fd < 0)
                        err("memfd_create");
                if (ftruncate(shm_fd, nr_pages * page_size * 2))
                        err("ftruncate");
                if (fallocate(shm_fd,
                              FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, 0,
                              nr_pages * page_size * 2))
                        err("fallocate");
        }
        printf("nr_pages: %lu, nr_pages_per_cpu: %lu\n",
               nr_pages, nr_pages_per_cpu);
        return userfaultfd_stress();
}

#else /* __NR_userfaultfd */

#warning "missing __NR_userfaultfd definition"

int main(void)
{
        printf("skip: Skipping userfaultfd test (missing __NR_userfaultfd)\n");
        return KSFT_SKIP;
}

#endif /* __NR_userfaultfd */