/*
 * Stress userfaultfd syscall.
 *
 *  Copyright (C) 2015  Red Hat, Inc.
 *
 *  This work is licensed under the terms of the GNU GPL, version 2. See
 *  the COPYING file in the top-level directory.
 *
 * 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).
 *
 * The program takes two parameters: the amounts of physical memory in
 * megabytes (MiB) of the area and the number of bounces to execute.
 *
 * # 100MiB 99999 bounces
 * ./userfaultfd 100 99999
 *
 * # 1GiB 99 bounces
 * ./userfaultfd 1000 99
 *
 * # 10MiB-~6GiB 999 bounces, continue forever unless an error triggers
 * while ./userfaultfd $[RANDOM % 6000 + 10] 999; do true; done
 */

#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 <pthread.h>
#include <linux/userfaultfd.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;

static unsigned long long *count_verify;
static int uffd, finished, *pipefd;
static char *area_src, *area_dst;
static char *zeropage;
pthread_attr_t attr;

/* 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)))

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 *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;
        time_t start;

        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))
                        fprintf(stderr, "srandom_r error\n"), exit(1);
        } 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))
                                fprintf(stderr, "random_r 1 error\n"), exit(1);
                        page_nr = rand_nr;
                        if (sizeof(page_nr) > sizeof(rand_nr)) {
                                if (random_r(&rand, &rand_nr))
                                        fprintf(stderr, "random_r 2 error\n"), exit(1);
                                page_nr |= (((unsigned long) rand_nr) << 16) <<
                                           16;
                        }
                } else
                        page_nr += 1;
                page_nr %= nr_pages;

                start = time(NULL);
                if (bounces & BOUNCE_VERIFY) {
                        count = *area_count(area_dst, page_nr);
                        if (!count)
                                fprintf(stderr,
                                        "page_nr %lu wrong count %Lu %Lu\n",
                                        page_nr, count,
                                        count_verify[page_nr]), exit(1);


                        /*
                         * We can't use bcmp (or memcmp) because that
                         * returns 0 erroneously if the memory is
                         * changing under it (even if the end of the
                         * page is never changing and always
                         * different).
                         */
#if 1
                        if (!my_bcmp(area_dst + page_nr * page_size, zeropage,
                                     page_size))
                                fprintf(stderr,
                                        "my_bcmp page_nr %lu wrong count %Lu %Lu\n",
                                        page_nr, count,
                                        count_verify[page_nr]), exit(1);
#else
                        unsigned long loops;

                        loops = 0;
                        /* uncomment the below line to test with mutex */
                        /* pthread_mutex_lock(area_mutex(area_dst, page_nr)); */
                        while (!bcmp(area_dst + page_nr * page_size, zeropage,
                                     page_size)) {
                                loops += 1;
                                if (loops > 10)
                                        break;
                        }
                        /* uncomment below line to test with mutex */
                        /* pthread_mutex_unlock(area_mutex(area_dst, page_nr)); */
                        if (loops) {
                                fprintf(stderr,
                                        "page_nr %lu all zero thread %lu %p %lu\n",
                                        page_nr, cpu, area_dst + page_nr * page_size,
                                        loops);
                                if (loops > 10)
                                        exit(1);
                        }
#endif
                }

                pthread_mutex_lock(area_mutex(area_dst, page_nr));
                count = *area_count(area_dst, page_nr);
                if (count != count_verify[page_nr]) {
                        fprintf(stderr,
                                "page_nr %lu memory corruption %Lu %Lu\n",
                                page_nr, count,
                                count_verify[page_nr]), exit(1);
                }
                count++;
                *area_count(area_dst, page_nr) = count_verify[page_nr] = count;
                pthread_mutex_unlock(area_mutex(area_dst, page_nr));

                if (time(NULL) - start > 1)
                        fprintf(stderr,
                                "userfault too slow %ld "
                                "possible false positive with overcommit\n",
                                time(NULL) - start);
        }

        return NULL;
}

static int copy_page(unsigned long offset)
{
        struct uffdio_copy uffdio_copy;

        if (offset >= nr_pages * page_size)
                fprintf(stderr, "unexpected offset %lu\n",
                        offset), exit(1);
        uffdio_copy.dst = (unsigned long) area_dst + offset;
        uffdio_copy.src = (unsigned long) area_src + offset;
        uffdio_copy.len = page_size;
        uffdio_copy.mode = 0;
        uffdio_copy.copy = 0;
        if (ioctl(uffd, UFFDIO_COPY, &uffdio_copy)) {
                /* real retval in ufdio_copy.copy */
                if (uffdio_copy.copy != -EEXIST)
                        fprintf(stderr, "UFFDIO_COPY error %Ld\n",
                                uffdio_copy.copy), exit(1);
        } else if (uffdio_copy.copy != page_size) {
                fprintf(stderr, "UFFDIO_COPY unexpected copy %Ld\n",
                        uffdio_copy.copy), exit(1);
        } else
                return 1;
        return 0;
}

static void *uffd_poll_thread(void *arg)
{
        unsigned long cpu = (unsigned long) arg;
        struct pollfd pollfd[2];
        struct uffd_msg msg;
        int ret;
        unsigned long offset;
        char tmp_chr;
        unsigned long userfaults = 0;

        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)
                        fprintf(stderr, "poll error %d\n", ret), exit(1);
                if (ret < 0)
                        perror("poll"), exit(1);
                if (pollfd[1].revents & POLLIN) {
                        if (read(pollfd[1].fd, &tmp_chr, 1) != 1)
                                fprintf(stderr, "read pipefd error\n"),
                                        exit(1);
                        break;
                }
                if (!(pollfd[0].revents & POLLIN))
                        fprintf(stderr, "pollfd[0].revents %d\n",
                                pollfd[0].revents), exit(1);
                ret = read(uffd, &msg, sizeof(msg));
                if (ret < 0) {
                        if (errno == EAGAIN)
                                continue;
                        perror("nonblocking read error"), exit(1);
                }
                if (msg.event != UFFD_EVENT_PAGEFAULT)
                        fprintf(stderr, "unexpected msg event %u\n",
                                msg.event), exit(1);
                if (msg.arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_WRITE)
                        fprintf(stderr, "unexpected write fault\n"), exit(1);
                offset = (char *)(unsigned long)msg.arg.pagefault.address -
                         area_dst;
                offset &= ~(page_size-1);
                if (copy_page(offset))
                        userfaults++;
        }
        return (void *)userfaults;
}

pthread_mutex_t uffd_read_mutex = PTHREAD_MUTEX_INITIALIZER;

static void *uffd_read_thread(void *arg)
{
        unsigned long *this_cpu_userfaults;
        struct uffd_msg msg;
        unsigned long offset;
        int ret;

        this_cpu_userfaults = (unsigned long *) arg;
        *this_cpu_userfaults = 0;

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

        for (;;) {
                ret = read(uffd, &msg, sizeof(msg));
                if (ret != sizeof(msg)) {
                        if (ret < 0)
                                perror("blocking read error"), exit(1);
                        else
                                fprintf(stderr, "short read\n"), exit(1);
                }
                if (msg.event != UFFD_EVENT_PAGEFAULT)
                        fprintf(stderr, "unexpected msg event %u\n",
                                msg.event), exit(1);
                if (bounces & BOUNCE_VERIFY &&
                    msg.arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_WRITE)
                        fprintf(stderr, "unexpected write fault\n"), exit(1);
                offset = (char *)(unsigned long)msg.arg.pagefault.address -
                         area_dst;
                offset &= ~(page_size-1);
                if (copy_page(offset))
                        (*this_cpu_userfaults)++;
        }
        return (void *)NULL;
}

static void *background_thread(void *arg)
{
        unsigned long cpu = (unsigned long) arg;
        unsigned long page_nr;

        for (page_nr = cpu * nr_pages_per_cpu;
             page_nr < (cpu+1) * nr_pages_per_cpu;
             page_nr++)
                copy_page(page_nr * page_size);

        return NULL;
}

static int stress(unsigned long *userfaults)
{
        unsigned long cpu;
        pthread_t locking_threads[nr_cpus];
        pthread_t uffd_threads[nr_cpus];
        pthread_t background_threads[nr_cpus];
        void **_userfaults = (void **) userfaults;

        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 *)cpu))
                                return 1;
                } else {
                        if (pthread_create(&uffd_threads[cpu], &attr,
                                           uffd_read_thread,
                                           &_userfaults[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).
         */
        if (madvise(area_src, nr_pages * page_size, MADV_DONTNEED)) {
                perror("madvise");
                return 1;
        }

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

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

        return 0;
}

static int userfaultfd_stress(void)
{
        void *area;
        char *tmp_area;
        unsigned long nr;
        struct uffdio_register uffdio_register;
        struct uffdio_api uffdio_api;
        unsigned long cpu;
        int uffd_flags, err;
        unsigned long userfaults[nr_cpus];

        if (posix_memalign(&area, page_size, nr_pages * page_size)) {
                fprintf(stderr, "out of memory\n");
                return 1;
        }
        area_src = area;
        if (posix_memalign(&area, page_size, nr_pages * page_size)) {
                fprintf(stderr, "out of memory\n");
                return 1;
        }
        area_dst = area;

        uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
        if (uffd < 0) {
                fprintf(stderr,
                        "userfaultfd syscall not available in this kernel\n");
                return 1;
        }
        uffd_flags = fcntl(uffd, F_GETFD, NULL);

        uffdio_api.api = UFFD_API;
        uffdio_api.features = 0;
        if (ioctl(uffd, UFFDIO_API, &uffdio_api)) {
                fprintf(stderr, "UFFDIO_API\n");
                return 1;
        }
        if (uffdio_api.api != UFFD_API) {
                fprintf(stderr, "UFFDIO_API error %Lu\n", uffdio_api.api);
                return 1;
        }

        count_verify = malloc(nr_pages * sizeof(unsigned long long));
        if (!count_verify) {
                perror("count_verify");
                return 1;
        }

        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) {
                perror("pipefd");
                return 1;
        }
        for (cpu = 0; cpu < nr_cpus; cpu++) {
                if (pipe2(&pipefd[cpu*2], O_CLOEXEC | O_NONBLOCK)) {
                        perror("pipe");
                        return 1;
                }
        }

        if (posix_memalign(&area, page_size, page_size)) {
                fprintf(stderr, "out of memory\n");
                return 1;
        }
        zeropage = area;
        bzero(zeropage, page_size);

        pthread_mutex_lock(&uffd_read_mutex);

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

        err = 0;
        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");
                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 (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register)) {
                        fprintf(stderr, "register failure\n");
                        return 1;
                }
                expected_ioctls = (1 << _UFFDIO_WAKE) |
                                  (1 << _UFFDIO_COPY) |
                                  (1 << _UFFDIO_ZEROPAGE);
                if ((uffdio_register.ioctls & expected_ioctls) !=
                    expected_ioctls) {
                        fprintf(stderr,
                                "unexpected missing ioctl for anon memory\n");
                        return 1;
                }

                /*
                 * 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.
                 */
                if (madvise(area_dst, nr_pages * page_size, MADV_DONTNEED)) {
                        perror("madvise 2");
                        return 1;
                }

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

                /* unregister */
                if (ioctl(uffd, UFFDIO_UNREGISTER, &uffdio_register.range)) {
                        fprintf(stderr, "register failure\n");
                        return 1;
                }

                /* verification */
                if (bounces & BOUNCE_VERIFY) {
                        for (nr = 0; nr < nr_pages; nr++) {
                                if (*area_count(area_dst, nr) != count_verify[nr]) {
                                        fprintf(stderr,
                                                "error area_count %Lu %Lu %lu\n",
                                                *area_count(area_src, nr),
                                                count_verify[nr],
                                                nr);
                                        err = 1;
                                        bounces = 0;
                                }
                        }
                }

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

                printf("userfaults:");
                for (cpu = 0; cpu < nr_cpus; cpu++)
                        printf(" %lu", userfaults[cpu]);
                printf("\n");
        }

        return err;
}

int main(int argc, char **argv)
{
        if (argc < 3)
                fprintf(stderr, "Usage: <MiB> <bounces>\n"), exit(1);
        nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
        page_size = sysconf(_SC_PAGE_SIZE);
        if ((unsigned long) area_count(NULL, 0) + sizeof(unsigned long long) * 2
            > page_size)
                fprintf(stderr, "Impossible to run this test\n"), exit(2);
        nr_pages_per_cpu = atol(argv[1]) * 1024*1024 / page_size /
                nr_cpus;
        if (!nr_pages_per_cpu) {
                fprintf(stderr, "invalid MiB\n");
                fprintf(stderr, "Usage: <MiB> <bounces>\n"), exit(1);
        }
        bounces = atoi(argv[2]);
        if (bounces <= 0) {
                fprintf(stderr, "invalid bounces\n");
                fprintf(stderr, "Usage: <MiB> <bounces>\n"), exit(1);
        }
        nr_pages = nr_pages_per_cpu * nr_cpus;
        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 0;
}

#endif /* __NR_userfaultfd */