1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * A test case of using hugepage memory in a user application using the 4 * mmap system call with MAP_HUGETLB flag. Before running this program 5 * make sure the administrator has allocated enough default sized huge 6 * pages to cover the 2 MB allocation. 7 */ 8 #include <stdlib.h> 9 #include <stdio.h> 10 #include <unistd.h> 11 #include <sys/mman.h> 12 #include <fcntl.h> 13 #include "vm_util.h" 14 15 #define PAGE_COMPOUND_HEAD (1UL << 15) 16 #define PAGE_COMPOUND_TAIL (1UL << 16) 17 #define PAGE_HUGE (1UL << 17) 18 19 #define HEAD_PAGE_FLAGS (PAGE_COMPOUND_HEAD | PAGE_HUGE) 20 #define TAIL_PAGE_FLAGS (PAGE_COMPOUND_TAIL | PAGE_HUGE) 21 22 #define PM_PFRAME_BITS 55 23 #define PM_PFRAME_MASK ~((1UL << PM_PFRAME_BITS) - 1) 24 25 static size_t pagesize; 26 static size_t maplength; 27 28 static void write_bytes(char *addr, size_t length) 29 { 30 unsigned long i; 31 32 for (i = 0; i < length; i++) 33 *(addr + i) = (char)i; 34 } 35 36 static unsigned long virt_to_pfn(void *addr) 37 { 38 int fd; 39 unsigned long pagemap; 40 41 fd = open("/proc/self/pagemap", O_RDONLY); 42 if (fd < 0) 43 return -1UL; 44 45 lseek(fd, (unsigned long)addr / pagesize * sizeof(pagemap), SEEK_SET); 46 read(fd, &pagemap, sizeof(pagemap)); 47 close(fd); 48 49 return pagemap & ~PM_PFRAME_MASK; 50 } 51 52 static int check_page_flags(unsigned long pfn) 53 { 54 int fd, i; 55 unsigned long pageflags; 56 57 fd = open("/proc/kpageflags", O_RDONLY); 58 if (fd < 0) 59 return -1; 60 61 lseek(fd, pfn * sizeof(pageflags), SEEK_SET); 62 63 read(fd, &pageflags, sizeof(pageflags)); 64 if ((pageflags & HEAD_PAGE_FLAGS) != HEAD_PAGE_FLAGS) { 65 close(fd); 66 printf("Head page flags (%lx) is invalid\n", pageflags); 67 return -1; 68 } 69 70 /* 71 * pages other than the first page must be tail and shouldn't be head; 72 * this also verifies kernel has correctly set the fake page_head to tail 73 * while hugetlb_free_vmemmap is enabled. 74 */ 75 for (i = 1; i < maplength / pagesize; i++) { 76 read(fd, &pageflags, sizeof(pageflags)); 77 if ((pageflags & TAIL_PAGE_FLAGS) != TAIL_PAGE_FLAGS || 78 (pageflags & HEAD_PAGE_FLAGS) == HEAD_PAGE_FLAGS) { 79 close(fd); 80 printf("Tail page flags (%lx) is invalid\n", pageflags); 81 return -1; 82 } 83 } 84 85 close(fd); 86 87 return 0; 88 } 89 90 int main(int argc, char **argv) 91 { 92 void *addr; 93 unsigned long pfn; 94 95 pagesize = psize(); 96 maplength = default_huge_page_size(); 97 if (!maplength) { 98 printf("Unable to determine huge page size\n"); 99 exit(1); 100 } 101 102 addr = mmap(NULL, maplength, PROT_READ | PROT_WRITE, 103 MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB, -1, 0); 104 if (addr == MAP_FAILED) { 105 perror("mmap"); 106 exit(1); 107 } 108 109 /* Trigger allocation of HugeTLB page. */ 110 write_bytes(addr, maplength); 111 112 pfn = virt_to_pfn(addr); 113 if (pfn == -1UL) { 114 munmap(addr, maplength); 115 perror("virt_to_pfn"); 116 exit(1); 117 } 118 119 printf("Returned address is %p whose pfn is %lx\n", addr, pfn); 120 121 if (check_page_flags(pfn) < 0) { 122 munmap(addr, maplength); 123 perror("check_page_flags"); 124 exit(1); 125 } 126 127 /* munmap() length of MAP_HUGETLB memory must be hugepage aligned */ 128 if (munmap(addr, maplength)) { 129 perror("munmap"); 130 exit(1); 131 } 132 133 return 0; 134 } 135