// SPDX-License-Identifier: GPL-2.0
#include <stdio.h>
#include <sys/mman.h>
#include <unistd.h>

#include "utils.h"

/* This must match the huge page & THP size */
#define SIZE    (16 * 1024 * 1024)

static int test_body(void)
{
        void *addr;
        char *p;

        addr = (void *)0xa0000000;

        p = mmap(addr, SIZE, PROT_READ | PROT_WRITE,
                 MAP_HUGETLB | MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
        if (p != MAP_FAILED) {
                /*
                 * Typically the mmap will fail because no huge pages are
                 * allocated on the system. But if there are huge pages
                 * allocated the mmap will succeed. That's fine too, we just
                 * munmap here before continuing.  munmap() length of
                 * MAP_HUGETLB memory must be hugepage aligned.
                 */
                if (munmap(addr, SIZE)) {
                        perror("munmap");
                        return 1;
                }
        }

        p = mmap(addr, SIZE, PROT_READ | PROT_WRITE,
                 MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
        if (p == MAP_FAILED) {
                printf("Mapping failed @ %p\n", addr);
                perror("mmap");
                return 1;
        }

        /*
         * Either a user or kernel access is sufficient to trigger the bug.
         * A kernel access is easier to spot & debug, as it will trigger the
         * softlockup or RCU stall detectors, and when the system is kicked
         * into xmon we get a backtrace in the kernel.
         *
         * A good option is:
         *  getcwd(p, SIZE);
         *
         * For the purposes of this testcase it's preferable to spin in
         * userspace, so the harness can kill us if we get stuck. That way we
         * see a test failure rather than a dead system.
         */
        *p = 0xf;

        munmap(addr, SIZE);

        return 0;
}

static int test_main(void)
{
        int i;

        /* 10,000 because it's a "bunch", and completes reasonably quickly */
        for (i = 0; i < 10000; i++)
                if (test_body())
                        return 1;

        return 0;
}

int main(void)
{
        return test_harness(test_main, "hugetlb_vs_thp");
}