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1// SPDX-License-Identifier: GPL-2.02/*3 * hugepage-mremap:4 *5 * Example of remapping huge page memory in a user application using the6 * mremap system call. The path to a file in a hugetlbfs filesystem must7 * be passed as the last argument to this test. The amount of memory used8 * by this test in MBs can optionally be passed as an argument. If no memory9 * 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_SOURCE16#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 10UL31#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 36static void check_bytes(char *addr)37{38 ksft_print_msg("First hex is %x\n", *((unsigned int *)addr));39}40 41static 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 49static 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 62static 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 be79 * demand-zero paged--that is, not yet allocated. When we80 * actually touch the memory, it will be allocated via81 * 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 for92 * handling by the userfaultfd object. In mode, we request to track93 * 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 99int 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 to111 * the default length.112 */113 if (argc >= 2)114 length = (size_t)atoi(argv[1]);115 else116 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