1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * hugepage-mremap: 4 * 5 * Example of remapping huge page memory in a user application using the 6 * mremap system call. The path to a file in a hugetlbfs filesystem must 7 * be passed as the last argument to this test. The amount of memory used 8 * by this test in MBs can optionally be passed as an argument. If no memory 9 * amount is passed, the default amount is 10MB. 10 * 11 * To make sure the test triggers pmd sharing and goes through the 'unshare' 12 * path in the mremap code use 1GB (1024) or more. 13 */ 14 15 #define _GNU_SOURCE 16 #include <stdlib.h> 17 #include <stdio.h> 18 #include <asm-generic/unistd.h> 19 #include <sys/mman.h> 20 #include <errno.h> 21 #include <fcntl.h> /* Definition of O_* constants */ 22 #include <sys/syscall.h> /* Definition of SYS_* constants */ 23 #include <linux/userfaultfd.h> 24 #include <sys/ioctl.h> 25 #include <string.h> 26 #include <stdbool.h> 27 #include "../kselftest.h" 28 #include "vm_util.h" 29 30 #define DEFAULT_LENGTH_MB 10UL 31 #define MB_TO_BYTES(x) (x * 1024 * 1024) 32 33 #define PROTECTION (PROT_READ | PROT_WRITE | PROT_EXEC) 34 #define FLAGS (MAP_SHARED | MAP_ANONYMOUS) 35 36 static void check_bytes(char *addr) 37 { 38 ksft_print_msg("First hex is %x\n", *((unsigned int *)addr)); 39 } 40 41 static void write_bytes(char *addr, size_t len) 42 { 43 unsigned long i; 44 45 for (i = 0; i < len; i++) 46 *(addr + i) = (char)i; 47 } 48 49 static int read_bytes(char *addr, size_t len) 50 { 51 unsigned long i; 52 53 check_bytes(addr); 54 for (i = 0; i < len; i++) 55 if (*(addr + i) != (char)i) { 56 ksft_print_msg("Mismatch at %lu\n", i); 57 return 1; 58 } 59 return 0; 60 } 61 62 static void register_region_with_uffd(char *addr, size_t len) 63 { 64 long uffd; /* userfaultfd file descriptor */ 65 struct uffdio_api uffdio_api; 66 67 /* Create and enable userfaultfd object. */ 68 69 uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK); 70 if (uffd == -1) 71 ksft_exit_fail_msg("userfaultfd: %s\n", strerror(errno)); 72 73 uffdio_api.api = UFFD_API; 74 uffdio_api.features = 0; 75 if (ioctl(uffd, UFFDIO_API, &uffdio_api) == -1) 76 ksft_exit_fail_msg("ioctl-UFFDIO_API: %s\n", strerror(errno)); 77 78 /* Create a private anonymous mapping. The memory will be 79 * demand-zero paged--that is, not yet allocated. When we 80 * actually touch the memory, it will be allocated via 81 * the userfaultfd. 82 */ 83 84 addr = mmap(NULL, len, PROT_READ | PROT_WRITE, 85 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); 86 if (addr == MAP_FAILED) 87 ksft_exit_fail_msg("mmap: %s\n", strerror(errno)); 88 89 ksft_print_msg("Address returned by mmap() = %p\n", addr); 90 91 /* Register the memory range of the mapping we just created for 92 * handling by the userfaultfd object. In mode, we request to track 93 * missing pages (i.e., pages that have not yet been faulted in). 94 */ 95 if (uffd_register(uffd, addr, len, true, false, false)) 96 ksft_exit_fail_msg("ioctl-UFFDIO_REGISTER: %s\n", strerror(errno)); 97 } 98 99 int main(int argc, char *argv[]) 100 { 101 size_t length = 0; 102 int ret = 0, fd; 103 104 ksft_print_header(); 105 ksft_set_plan(1); 106 107 if (argc >= 2 && !strcmp(argv[1], "-h")) 108 ksft_exit_fail_msg("Usage: %s [length_in_MB]\n", argv[0]); 109 110 /* Read memory length as the first arg if valid, otherwise fallback to 111 * the default length. 112 */ 113 if (argc >= 2) 114 length = (size_t)atoi(argv[1]); 115 else 116 length = DEFAULT_LENGTH_MB; 117 118 length = MB_TO_BYTES(length); 119 fd = memfd_create(argv[0], MFD_HUGETLB); 120 if (fd < 0) 121 ksft_exit_fail_msg("Open failed: %s\n", strerror(errno)); 122 123 /* mmap to a PUD aligned address to hopefully trigger pmd sharing. */ 124 unsigned long suggested_addr = 0x7eaa40000000; 125 void *haddr = mmap((void *)suggested_addr, length, PROTECTION, 126 MAP_HUGETLB | MAP_SHARED | MAP_POPULATE, fd, 0); 127 ksft_print_msg("Map haddr: Returned address is %p\n", haddr); 128 if (haddr == MAP_FAILED) 129 ksft_exit_fail_msg("mmap1: %s\n", strerror(errno)); 130 131 /* mmap again to a dummy address to hopefully trigger pmd sharing. */ 132 suggested_addr = 0x7daa40000000; 133 void *daddr = mmap((void *)suggested_addr, length, PROTECTION, 134 MAP_HUGETLB | MAP_SHARED | MAP_POPULATE, fd, 0); 135 ksft_print_msg("Map daddr: Returned address is %p\n", daddr); 136 if (daddr == MAP_FAILED) 137 ksft_exit_fail_msg("mmap3: %s\n", strerror(errno)); 138 139 suggested_addr = 0x7faa40000000; 140 void *vaddr = 141 mmap((void *)suggested_addr, length, PROTECTION, FLAGS, -1, 0); 142 ksft_print_msg("Map vaddr: Returned address is %p\n", vaddr); 143 if (vaddr == MAP_FAILED) 144 ksft_exit_fail_msg("mmap2: %s\n", strerror(errno)); 145 146 register_region_with_uffd(haddr, length); 147 148 void *addr = mremap(haddr, length, length, 149 MREMAP_MAYMOVE | MREMAP_FIXED, vaddr); 150 if (addr == MAP_FAILED) 151 ksft_exit_fail_msg("mremap: %s\n", strerror(errno)); 152 153 ksft_print_msg("Mremap: Returned address is %p\n", addr); 154 check_bytes(addr); 155 write_bytes(addr, length); 156 ret = read_bytes(addr, length); 157 158 munmap(addr, length); 159 160 addr = mremap(addr, length, length, 0); 161 if (addr != MAP_FAILED) 162 ksft_exit_fail_msg("mremap: Expected failure, but call succeeded\n"); 163 164 close(fd); 165 166 ksft_test_result(!ret, "Read same data\n"); 167 ksft_exit(!ret); 168 } 169