tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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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 * 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
35static void check_bytes(char *addr)
36{
37 printf("First hex is %x\n", *((unsigned int *)addr));
38}
39
40static 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
48static 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
61int 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}