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 19 #define LENGTH (256UL*1024*1024) 20 #define PROTECTION (PROT_READ | PROT_WRITE) 21 22 #ifndef MAP_HUGETLB 23 #define MAP_HUGETLB 0x40000 /* arch specific */ 24 #endif 25 26 /* Only ia64 requires this */ 27 #ifdef __ia64__ 28 #define ADDR (void *)(0x8000000000000000UL) 29 #define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB | MAP_FIXED) 30 #else 31 #define ADDR (void *)(0x0UL) 32 #define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB) 33 #endif 34 35 static void check_bytes(char *addr) 36 { 37 printf("First hex is %x\n", *((unsigned int *)addr)); 38 } 39 40 static void write_bytes(char *addr) 41 { 42 unsigned long i; 43 44 for (i = 0; i < LENGTH; i++) 45 *(addr + i) = (char)i; 46 } 47 48 static int read_bytes(char *addr) 49 { 50 unsigned long i; 51 52 check_bytes(addr); 53 for (i = 0; i < LENGTH; i++) 54 if (*(addr + i) != (char)i) { 55 printf("Mismatch at %lu\n", i); 56 return 1; 57 } 58 return 0; 59 } 60 61 int main(void) 62 { 63 void *addr; 64 int ret; 65 66 addr = mmap(ADDR, LENGTH, PROTECTION, FLAGS, -1, 0); 67 if (addr == MAP_FAILED) { 68 perror("mmap"); 69 exit(1); 70 } 71 72 printf("Returned address is %p\n", addr); 73 check_bytes(addr); 74 write_bytes(addr); 75 ret = read_bytes(addr); 76 77 /* munmap() length of MAP_HUGETLB memory must be hugepage aligned */ 78 if (munmap(addr, LENGTH)) { 79 perror("munmap"); 80 exit(1); 81 } 82 83 return ret; 84 } 85
