tools/testing/selftests/mm/hugepage-mremap.c

   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 }