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 * 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#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#include "../kselftest.h"
15
16#define LENGTH (256UL*1024*1024)
17#define PROTECTION (PROT_READ | PROT_WRITE)
18
19static void check_bytes(char *addr)
20{
21 ksft_print_msg("First hex is %x\n", *((unsigned int *)addr));
22}
23
24static void write_bytes(char *addr, size_t length)
25{
26 unsigned long i;
27
28 for (i = 0; i < length; i++)
29 *(addr + i) = (char)i;
30}
31
32static void read_bytes(char *addr, size_t length)
33{
34 unsigned long i;
35
36 check_bytes(addr);
37 for (i = 0; i < length; i++)
38 if (*(addr + i) != (char)i)
39 ksft_exit_fail_msg("Mismatch at %lu\n", i);
40
41 ksft_test_result_pass("Read correct data\n");
42}
43
44int main(int argc, char **argv)
45{
46 void *addr;
47 size_t hugepage_size;
48 size_t length = LENGTH;
49 int flags = MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB;
50 int shift = 0;
51
52 hugepage_size = default_huge_page_size();
53 /* munmap with fail if the length is not page aligned */
54 if (hugepage_size > length)
55 length = hugepage_size;
56
57 ksft_print_header();
58 ksft_set_plan(1);
59
60 if (argc > 1)
61 length = atol(argv[1]) << 20;
62 if (argc > 2) {
63 shift = atoi(argv[2]);
64 if (shift)
65 flags |= (shift & MAP_HUGE_MASK) << MAP_HUGE_SHIFT;
66 }
67
68 if (shift)
69 ksft_print_msg("%u kB hugepages\n", 1 << (shift - 10));
70 else
71 ksft_print_msg("Default size hugepages\n");
72 ksft_print_msg("Mapping %lu Mbytes\n", (unsigned long)length >> 20);
73
74 addr = mmap(NULL, length, PROTECTION, flags, -1, 0);
75 if (addr == MAP_FAILED)
76 ksft_exit_fail_msg("mmap: %s\n", strerror(errno));
77
78 ksft_print_msg("Returned address is %p\n", addr);
79 check_bytes(addr);
80 write_bytes(addr, length);
81 read_bytes(addr, length);
82
83 /* munmap() length of MAP_HUGETLB memory must be hugepage aligned */
84 if (munmap(addr, length))
85 ksft_exit_fail_msg("munmap: %s\n", strerror(errno));
86
87 ksft_finished();
88}