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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 is6// handled correctly, ie. the child is able to access the mappings beyond the7// 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_NOREPLACE20#define MAP_FIXED_NOREPLACE MAP_FIXED // "Should be safe" above 512TB21#endif22 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_id34 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 optimisation65 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