selftests/vm/hugepage-vmemmap.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * A test case of using hugepage memory in a user application using the
0004  * mmap system call with MAP_HUGETLB flag.  Before running this program
0005  * make sure the administrator has allocated enough default sized huge
0006  * pages to cover the 2 MB allocation.
0007  */
0008 #include <stdlib.h>
0009 #include <stdio.h>
0010 #include <unistd.h>
0011 #include <sys/mman.h>
0012 #include <fcntl.h>
0013
0014 #define MAP_LENGTH      (2UL * 1024 * 1024)
0015
0016 #ifndef MAP_HUGETLB
0017 #define MAP_HUGETLB     0x40000 /* arch specific */
0018 #endif
0019
0020 #define PAGE_SIZE       4096
0021
0022 #define PAGE_COMPOUND_HEAD  (1UL << 15)
0023 #define PAGE_COMPOUND_TAIL  (1UL << 16)
0024 #define PAGE_HUGE       (1UL << 17)
0025
0026 #define HEAD_PAGE_FLAGS     (PAGE_COMPOUND_HEAD | PAGE_HUGE)
0027 #define TAIL_PAGE_FLAGS     (PAGE_COMPOUND_TAIL | PAGE_HUGE)
0028
0029 #define PM_PFRAME_BITS      55
0030 #define PM_PFRAME_MASK      ~((1UL << PM_PFRAME_BITS) - 1)
0031
0032 /*
0033  * For ia64 architecture, Linux kernel reserves Region number 4 for hugepages.
0034  * That means the addresses starting with 0x800000... will need to be
0035  * specified.  Specifying a fixed address is not required on ppc64, i386
0036  * or x86_64.
0037  */
0038 #ifdef __ia64__
0039 #define MAP_ADDR        (void *)(0x8000000000000000UL)
0040 #define MAP_FLAGS       (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB | MAP_FIXED)
0041 #else
0042 #define MAP_ADDR        NULL
0043 #define MAP_FLAGS       (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB)
0044 #endif
0045
0046 static void write_bytes(char *addr, size_t length)
0047 {
0048     unsigned long i;
0049
0050     for (i = 0; i < length; i++)
0051         *(addr + i) = (char)i;
0052 }
0053
0054 static unsigned long virt_to_pfn(void *addr)
0055 {
0056     int fd;
0057     unsigned long pagemap;
0058
0059     fd = open("/proc/self/pagemap", O_RDONLY);
0060     if (fd < 0)
0061         return -1UL;
0062
0063     lseek(fd, (unsigned long)addr / PAGE_SIZE * sizeof(pagemap), SEEK_SET);
0064     read(fd, &pagemap, sizeof(pagemap));
0065     close(fd);
0066
0067     return pagemap & ~PM_PFRAME_MASK;
0068 }
0069
0070 static int check_page_flags(unsigned long pfn)
0071 {
0072     int fd, i;
0073     unsigned long pageflags;
0074
0075     fd = open("/proc/kpageflags", O_RDONLY);
0076     if (fd < 0)
0077         return -1;
0078
0079     lseek(fd, pfn * sizeof(pageflags), SEEK_SET);
0080
0081     read(fd, &pageflags, sizeof(pageflags));
0082     if ((pageflags & HEAD_PAGE_FLAGS) != HEAD_PAGE_FLAGS) {
0083         close(fd);
0084         printf("Head page flags (%lx) is invalid\n", pageflags);
0085         return -1;
0086     }
0087
0088     /*
0089      * pages other than the first page must be tail and shouldn't be head;
0090      * this also verifies kernel has correctly set the fake page_head to tail
0091      * while hugetlb_free_vmemmap is enabled.
0092      */
0093     for (i = 1; i < MAP_LENGTH / PAGE_SIZE; i++) {
0094         read(fd, &pageflags, sizeof(pageflags));
0095         if ((pageflags & TAIL_PAGE_FLAGS) != TAIL_PAGE_FLAGS ||
0096             (pageflags & HEAD_PAGE_FLAGS) == HEAD_PAGE_FLAGS) {
0097             close(fd);
0098             printf("Tail page flags (%lx) is invalid\n", pageflags);
0099             return -1;
0100         }
0101     }
0102
0103     close(fd);
0104
0105     return 0;
0106 }
0107
0108 int main(int argc, char **argv)
0109 {
0110     void *addr;
0111     unsigned long pfn;
0112
0113     addr = mmap(MAP_ADDR, MAP_LENGTH, PROT_READ | PROT_WRITE, MAP_FLAGS, -1, 0);
0114     if (addr == MAP_FAILED) {
0115         perror("mmap");
0116         exit(1);
0117     }
0118
0119     /* Trigger allocation of HugeTLB page. */
0120     write_bytes(addr, MAP_LENGTH);
0121
0122     pfn = virt_to_pfn(addr);
0123     if (pfn == -1UL) {
0124         munmap(addr, MAP_LENGTH);
0125         perror("virt_to_pfn");
0126         exit(1);
0127     }
0128
0129     printf("Returned address is %p whose pfn is %lx\n", addr, pfn);
0130
0131     if (check_page_flags(pfn) < 0) {
0132         munmap(addr, MAP_LENGTH);
0133         perror("check_page_flags");
0134         exit(1);
0135     }
0136
0137     /* munmap() length of MAP_HUGETLB memory must be hugepage aligned */
0138     if (munmap(addr, MAP_LENGTH)) {
0139         perror("munmap");
0140         exit(1);
0141     }
0142
0143     return 0;
0144 }