// SPDX-License-Identifier: GPL-2.0+
//
// Copyright 2019, Michael Ellerman, IBM Corp.
//
// Test that allocating memory beyond the memory limit and then forking is
// handled correctly, ie. the child is able to access the mappings beyond the
// memory limit and the child's writes are not visible to the parent.

#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>

#include "utils.h"


#ifndef MAP_FIXED_NOREPLACE
#define MAP_FIXED_NOREPLACE     MAP_FIXED       // "Should be safe" above 512TB
#endif


static int test(void)
{
        int p2c[2], c2p[2], rc, status, c, *p;
        unsigned long page_size;
        pid_t pid;

        page_size = sysconf(_SC_PAGESIZE);
        SKIP_IF(page_size != 65536);

        // Create a mapping at 512TB to allocate an extended_id
        p = mmap((void *)(512ul << 40), page_size, PROT_READ | PROT_WRITE,
                MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED_NOREPLACE, -1, 0);
        if (p == MAP_FAILED) {
                perror("mmap");
                printf("Error: couldn't mmap(), confirm kernel has 4TB support?\n");
                return 1;
        }

        printf("parent writing %p = 1\n", p);
        *p = 1;

        FAIL_IF(pipe(p2c) == -1 || pipe(c2p) == -1);

        pid = fork();
        if (pid == 0) {
                FAIL_IF(read(p2c[0], &c, 1) != 1);

                pid = getpid();
                printf("child writing  %p = %d\n", p, pid);
                *p = pid;

                FAIL_IF(write(c2p[1], &c, 1) != 1);
                FAIL_IF(read(p2c[0], &c, 1) != 1);
                exit(0);
        }

        c = 0;
        FAIL_IF(write(p2c[1], &c, 1) != 1);
        FAIL_IF(read(c2p[0], &c, 1) != 1);

        // Prevent compiler optimisation
        barrier();

        rc = 0;
        printf("parent reading %p = %d\n", p, *p);
        if (*p != 1) {
                printf("Error: BUG! parent saw child's write! *p = %d\n", *p);
                rc = 1;
        }

        FAIL_IF(write(p2c[1], &c, 1) != 1);
        FAIL_IF(waitpid(pid, &status, 0) == -1);
        FAIL_IF(!WIFEXITED(status) || WEXITSTATUS(status));

        if (rc == 0)
                printf("success: test completed OK\n");

        return rc;
}

int main(void)
{
        return test_harness(test, "large_vm_fork_separation");
}