1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Example of using hugepage memory in a user application using the mmap 4 * system call with MAP_HUGETLB flag. Before running this program make 5 * sure the administrator has allocated enough default sized huge pages 6 * to cover the 256 MB allocation. 7 * 8 * For ia64 architecture, Linux kernel reserves Region number 4 for hugepages. 9 * That means the addresses starting with 0x800000... will need to be 10 * specified. Specifying a fixed address is not required on ppc64, i386 11 * or x86_64. 12 */ 13 #include <stdlib.h> 14 #include <stdio.h> 15 #include <unistd.h> 16 #include <sys/mman.h> 17 #include <fcntl.h> 18 #include "vm_util.h" 19 20 #define LENGTH (256UL*1024*1024) 21 #define PROTECTION (PROT_READ | PROT_WRITE) 22 23 /* Only ia64 requires this */ 24 #ifdef __ia64__ 25 #define ADDR (void *)(0x8000000000000000UL) 26 #define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB | MAP_FIXED) 27 #else 28 #define ADDR (void *)(0x0UL) 29 #define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB) 30 #endif 31 32 static void check_bytes(char *addr) 33 { 34 printf("First hex is %x\n", *((unsigned int *)addr)); 35 } 36 37 static void write_bytes(char *addr, size_t length) 38 { 39 unsigned long i; 40 41 for (i = 0; i < length; i++) 42 *(addr + i) = (char)i; 43 } 44 45 static int read_bytes(char *addr, size_t length) 46 { 47 unsigned long i; 48 49 check_bytes(addr); 50 for (i = 0; i < length; i++) 51 if (*(addr + i) != (char)i) { 52 printf("Mismatch at %lu\n", i); 53 return 1; 54 } 55 return 0; 56 } 57 58 int main(int argc, char **argv) 59 { 60 void *addr; 61 int ret; 62 size_t hugepage_size; 63 size_t length = LENGTH; 64 int flags = FLAGS; 65 int shift = 0; 66 67 hugepage_size = default_huge_page_size(); 68 /* munmap with fail if the length is not page aligned */ 69 if (hugepage_size > length) 70 length = hugepage_size; 71 72 if (argc > 1) 73 length = atol(argv[1]) << 20; 74 if (argc > 2) { 75 shift = atoi(argv[2]); 76 if (shift) 77 flags |= (shift & MAP_HUGE_MASK) << MAP_HUGE_SHIFT; 78 } 79 80 if (shift) 81 printf("%u kB hugepages\n", 1 << (shift - 10)); 82 else 83 printf("Default size hugepages\n"); 84 printf("Mapping %lu Mbytes\n", (unsigned long)length >> 20); 85 86 addr = mmap(ADDR, length, PROTECTION, flags, -1, 0); 87 if (addr == MAP_FAILED) { 88 perror("mmap"); 89 exit(1); 90 } 91 92 printf("Returned address is %p\n", addr); 93 check_bytes(addr); 94 write_bytes(addr, length); 95 ret = read_bytes(addr, length); 96 97 /* munmap() length of MAP_HUGETLB memory must be hugepage aligned */ 98 if (munmap(addr, length)) { 99 perror("munmap"); 100 exit(1); 101 } 102 103 return ret; 104 } 105