1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * hugepage-mmap: 4 * 5 * Example of using huge page memory in a user application using the mmap 6 * system call. Before running this application, make sure that the 7 * administrator has mounted the hugetlbfs filesystem (on some directory 8 * like /mnt) using the command mount -t hugetlbfs nodev /mnt. In this 9 * example, the app is requesting memory of size 256MB that is backed by 10 * huge pages. 11 * 12 * For the ia64 architecture, the Linux kernel reserves Region number 4 for 13 * huge pages. That means that if one requires a fixed address, a huge page 14 * aligned address starting with 0x800000... will be required. If a fixed 15 * address is not required, the kernel will select an address in the proper 16 * range. 17 * Other architectures, such as ppc64, i386 or x86_64 are not so constrained. 18 */ 19 #define _GNU_SOURCE 20 #include <stdlib.h> 21 #include <stdio.h> 22 #include <unistd.h> 23 #include <sys/mman.h> 24 #include <fcntl.h> 25 #include "../kselftest.h" 26 27 #define LENGTH (256UL*1024*1024) 28 #define PROTECTION (PROT_READ | PROT_WRITE) 29 30 /* Only ia64 requires this */ 31 #ifdef __ia64__ 32 #define ADDR (void *)(0x8000000000000000UL) 33 #define FLAGS (MAP_SHARED | MAP_FIXED) 34 #else 35 #define ADDR (void *)(0x0UL) 36 #define FLAGS (MAP_SHARED) 37 #endif 38 39 static void check_bytes(char *addr) 40 { 41 ksft_print_msg("First hex is %x\n", *((unsigned int *)addr)); 42 } 43 44 static void write_bytes(char *addr) 45 { 46 unsigned long i; 47 48 for (i = 0; i < LENGTH; i++) 49 *(addr + i) = (char)i; 50 } 51 52 static int read_bytes(char *addr) 53 { 54 unsigned long i; 55 56 check_bytes(addr); 57 for (i = 0; i < LENGTH; i++) 58 if (*(addr + i) != (char)i) { 59 ksft_print_msg("Error: Mismatch at %lu\n", i); 60 return 1; 61 } 62 return 0; 63 } 64 65 int main(void) 66 { 67 void *addr; 68 int fd, ret; 69 70 ksft_print_header(); 71 ksft_set_plan(1); 72 73 fd = memfd_create("hugepage-mmap", MFD_HUGETLB); 74 if (fd < 0) 75 ksft_exit_fail_msg("memfd_create() failed: %s\n", strerror(errno)); 76 77 addr = mmap(ADDR, LENGTH, PROTECTION, FLAGS, fd, 0); 78 if (addr == MAP_FAILED) { 79 close(fd); 80 ksft_exit_fail_msg("mmap(): %s\n", strerror(errno)); 81 } 82 83 ksft_print_msg("Returned address is %p\n", addr); 84 check_bytes(addr); 85 write_bytes(addr); 86 ret = read_bytes(addr); 87 88 munmap(addr, LENGTH); 89 close(fd); 90 91 ksft_test_result(!ret, "Read same data\n"); 92 93 ksft_exit(!ret); 94 } 95