1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * hugetlb-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 <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 #include "hugepage_settings.h" 30 31 #define DEFAULT_LENGTH_MB 10UL 32 #define MB_TO_BYTES(x) (x * 1024 * 1024) 33 34 #define PROTECTION (PROT_READ | PROT_WRITE | PROT_EXEC) 35 #define FLAGS (MAP_HUGETLB | MAP_SHARED) 36 37 static void check_bytes(char *addr) 38 { 39 ksft_print_msg("First hex is %x\n", *((unsigned int *)addr)); 40 } 41 42 static void write_bytes(char *addr, size_t len) 43 { 44 unsigned long i; 45 46 for (i = 0; i < len; i++) 47 *(addr + i) = (char)i; 48 } 49 50 static int read_bytes(char *addr, size_t len) 51 { 52 unsigned long i; 53 54 check_bytes(addr); 55 for (i = 0; i < len; i++) 56 if (*(addr + i) != (char)i) { 57 ksft_print_msg("Mismatch at %lu\n", i); 58 return 1; 59 } 60 return 0; 61 } 62 63 static void register_region_with_uffd(char *addr, size_t len) 64 { 65 long uffd; /* userfaultfd file descriptor */ 66 struct uffdio_api uffdio_api; 67 68 /* Create and enable userfaultfd object. */ 69 uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK); 70 if (uffd == -1) { 71 switch (errno) { 72 case EPERM: 73 ksft_exit_skip("Insufficient permissions, try running as root.\n"); 74 break; 75 case ENOSYS: 76 ksft_exit_skip("userfaultfd is not supported/not enabled.\n"); 77 break; 78 default: 79 ksft_exit_fail_msg("userfaultfd failed with %s\n", strerror(errno)); 80 break; 81 } 82 } 83 84 uffdio_api.api = UFFD_API; 85 uffdio_api.features = 0; 86 if (ioctl(uffd, UFFDIO_API, &uffdio_api) == -1) 87 ksft_exit_fail_msg("ioctl-UFFDIO_API: %s\n", strerror(errno)); 88 89 /* Register the passed memory range for handling by the userfaultfd object. 90 * In mode, we request to track missing pages 91 * (i.e., pages that have not yet been faulted in). 92 */ 93 if (uffd_register(uffd, addr, len, true, false, false)) 94 ksft_exit_fail_msg("ioctl-UFFDIO_REGISTER: %s\n", strerror(errno)); 95 96 ksft_print_msg("Registered memory at address %p with userfaultfd\n", addr); 97 } 98 99 int main(int argc, char *argv[]) 100 { 101 unsigned long hugepage_size; 102 int ret = 0, fd, nr; 103 size_t length = 0; 104 105 ksft_print_header(); 106 ksft_set_plan(1); 107 108 if (argc >= 2 && !strcmp(argv[1], "-h")) 109 ksft_exit_fail_msg("Usage: %s [length_in_MB]\n", argv[0]); 110 111 /* Read memory length as the first arg if valid, otherwise fallback to 112 * the default length. 113 */ 114 if (argc >= 2) 115 length = (size_t)atoi(argv[1]); 116 else 117 length = DEFAULT_LENGTH_MB; 118 119 hugepage_size = default_huge_page_size(); 120 if (!hugepage_size) 121 ksft_exit_skip("Could not detect default hugetlb page size\n"); 122 length = MB_TO_BYTES(length); 123 length = (length + hugepage_size - 1) & ~(hugepage_size - 1); 124 nr = length / hugepage_size; 125 126 if (!hugetlb_setup_default(nr)) 127 ksft_exit_skip("Not enough huge pages\n"); 128 129 fd = memfd_create(argv[0], MFD_HUGETLB); 130 if (fd < 0) 131 ksft_exit_fail_msg("Open failed: %s\n", strerror(errno)); 132 133 /* mmap to a PUD aligned address to hopefully trigger pmd sharing. */ 134 unsigned long suggested_addr = 0x7eaa40000000; 135 void *haddr = mmap((void *)suggested_addr, length, PROTECTION, FLAGS, fd, 0); 136 ksft_print_msg("Map haddr: Returned address is %p\n", haddr); 137 if (haddr == MAP_FAILED) 138 ksft_exit_fail_msg("mmap1: %s\n", strerror(errno)); 139 140 /* mmap again to a dummy address to hopefully trigger pmd sharing. */ 141 suggested_addr = 0x7daa40000000; 142 void *daddr = mmap((void *)suggested_addr, length, PROTECTION, FLAGS, fd, 0); 143 ksft_print_msg("Map daddr: Returned address is %p\n", daddr); 144 if (daddr == MAP_FAILED) 145 ksft_exit_fail_msg("mmap3: %s\n", strerror(errno)); 146 147 suggested_addr = 0x7faa40000000; 148 void *vaddr = mmap((void *)suggested_addr, length, PROTECTION, FLAGS, fd, 0); 149 ksft_print_msg("Map vaddr: Returned address is %p\n", vaddr); 150 if (vaddr == MAP_FAILED) 151 ksft_exit_fail_msg("mmap2: %s\n", strerror(errno)); 152 153 register_region_with_uffd(haddr, length); 154 155 void *addr = mremap(haddr, length, length, 156 MREMAP_MAYMOVE | MREMAP_FIXED, vaddr); 157 if (addr == MAP_FAILED) 158 ksft_exit_fail_msg("mremap: %s\n", strerror(errno)); 159 160 ksft_print_msg("Mremap: Returned address is %p\n", addr); 161 check_bytes(addr); 162 write_bytes(addr, length); 163 ret = read_bytes(addr, length); 164 165 munmap(addr, length); 166 167 addr = mremap(addr, length, length, 0); 168 if (addr != MAP_FAILED) 169 ksft_exit_fail_msg("mremap: Expected failure, but call succeeded\n"); 170 171 close(fd); 172 173 ksft_test_result(!ret, "Read same data\n"); 174 ksft_exit(!ret); 175 } 176