tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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
25static size_t pagesize;
26static size_t maplength;
27
28static 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
36static 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
52static 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
90int 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}