// SPDX-License-Identifier: GPL-2.0
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <unistd.h>
#include <setjmp.h>
#include <signal.h>

#include "vm_util.h"
#include "kselftest.h"

#define INLOOP_ITER 100

static char *huge_ptr;
static size_t huge_page_size;

static sigjmp_buf sigbuf;
static bool sigbus_triggered;

static void signal_handler(int signal)
{
        if (signal == SIGBUS) {
                sigbus_triggered = true;
                siglongjmp(sigbuf, 1);
        }
}

/* Touch the memory while it is being madvised() */
void *touch(void *unused)
{
        char *ptr = (char *)huge_ptr;

        if (sigsetjmp(sigbuf, 1))
                return NULL;

        for (int i = 0; i < INLOOP_ITER; i++)
                ptr[0] = '.';

        return NULL;
}

void *madv(void *unused)
{
        usleep(rand() % 10);

        for (int i = 0; i < INLOOP_ITER; i++)
                madvise(huge_ptr, huge_page_size, MADV_DONTNEED);

        return NULL;
}

int main(void)
{
        unsigned long free_hugepages;
        pthread_t thread1, thread2;
        /*
         * On kernel 6.4, we are able to reproduce the problem with ~1000
         * interactions
         */
        int max = 10000;
        int err;

        ksft_print_header();
        ksft_set_plan(1);

        srand(getpid());

        if (signal(SIGBUS, signal_handler) == SIG_ERR)
                ksft_exit_skip("Could not register signal handler.");

        huge_page_size = default_huge_page_size();
        if (!huge_page_size)
                ksft_exit_skip("Could not detect default hugetlb page size.");

        ksft_print_msg("[INFO] detected default hugetlb page size: %zu KiB\n",
                       huge_page_size / 1024);

        free_hugepages = get_free_hugepages();
        if (free_hugepages != 1) {
                ksft_exit_skip("This test needs one and only one page to execute. Got %lu\n",
                               free_hugepages);
        }

        while (max--) {
                huge_ptr = mmap(NULL, huge_page_size, PROT_READ | PROT_WRITE,
                                MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB,
                                -1, 0);

                if ((unsigned long)huge_ptr == -1)
                        ksft_exit_skip("Failed to allocated huge page\n");

                pthread_create(&thread1, NULL, madv, NULL);
                pthread_create(&thread2, NULL, touch, NULL);

                pthread_join(thread1, NULL);
                pthread_join(thread2, NULL);
                munmap(huge_ptr, huge_page_size);
        }

        ksft_test_result(!sigbus_triggered, "SIGBUS behavior\n");

        err = ksft_get_fail_cnt();
        if (err)
                ksft_exit_fail_msg("%d out of %d tests failed\n",
                                   err, ksft_test_num());
        ksft_exit_pass();
}