LXR linux/tools/testing/selftests/powerpc/mm/large_vm_fork

   1// SPDX-License-Identifier: GPL-2.0+
   2//
   3// Copyright 2019, Michael Ellerman, IBM Corp.
   4//
   5// Test that allocating memory beyond the memory limit and then forking is
   6// handled correctly, ie. the child is able to access the mappings beyond the
   7// memory limit and the child's writes are not visible to the parent.
   8
   9#include <stdio.h>
  10#include <stdlib.h>
  11#include <sys/mman.h>
  12#include <sys/types.h>
  13#include <sys/wait.h>
  14#include <unistd.h>
  15
  16#include "utils.h"
  17
  18
  19#ifndef MAP_FIXED_NOREPLACE
  20#define MAP_FIXED_NOREPLACE     MAP_FIXED       // "Should be safe" above 512TB
  21#endif
  22
  23
  24static int test(void)
  25{
  26        int p2c[2], c2p[2], rc, status, c, *p;
  27        unsigned long page_size;
  28        pid_t pid;
  29
  30        page_size = sysconf(_SC_PAGESIZE);
  31        SKIP_IF(page_size != 65536);
  32
  33        // Create a mapping at 512TB to allocate an extended_id
  34        p = mmap((void *)(512ul << 40), page_size, PROT_READ | PROT_WRITE,
  35                MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED_NOREPLACE, -1, 0);
  36        if (p == MAP_FAILED) {
  37                perror("mmap");
  38                printf("Error: couldn't mmap(), confirm kernel has 4TB support?\n");
  39                return 1;
  40        }
  41
  42        printf("parent writing %p = 1\n", p);
  43        *p = 1;
  44
  45        FAIL_IF(pipe(p2c) == -1 || pipe(c2p) == -1);
  46
  47        pid = fork();
  48        if (pid == 0) {
  49                FAIL_IF(read(p2c[0], &c, 1) != 1);
  50
  51                pid = getpid();
  52                printf("child writing  %p = %d\n", p, pid);
  53                *p = pid;
  54
  55                FAIL_IF(write(c2p[1], &c, 1) != 1);
  56                FAIL_IF(read(p2c[0], &c, 1) != 1);
  57                exit(0);
  58        }
  59
  60        c = 0;
  61        FAIL_IF(write(p2c[1], &c, 1) != 1);
  62        FAIL_IF(read(c2p[0], &c, 1) != 1);
  63
  64        // Prevent compiler optimisation
  65        barrier();
  66
  67        rc = 0;
  68        printf("parent reading %p = %d\n", p, *p);
  69        if (*p != 1) {
  70                printf("Error: BUG! parent saw child's write! *p = %d\n", *p);
  71                rc = 1;
  72        }
  73
  74        FAIL_IF(write(p2c[1], &c, 1) != 1);
  75        FAIL_IF(waitpid(pid, &status, 0) == -1);
  76        FAIL_IF(!WIFEXITED(status) || WEXITSTATUS(status));
  77
  78        if (rc == 0)
  79                printf("success: test completed OK\n");
  80
  81        return rc;
  82}
  83
  84int main(void)
  85{
  86        return test_harness(test, "large_vm_fork_separation");
  87}
  88