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// SPDX-License-Identifier: GPL-2.0
/*
* Example of using hugepage memory in a user application using the mmap
* system call with MAP_HUGETLB flag. Before running this program make
* sure the administrator has allocated enough default sized huge pages
* to cover the 256 MB allocation.
*
* For ia64 architecture, Linux kernel reserves Region number 4 for hugepages.
* That means the addresses starting with 0x800000... will need to be
* specified. Specifying a fixed address is not required on ppc64, i386
* or x86_64.
*/
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/mman.h>
#include <fcntl.h>
#define LENGTH (256UL*1024*1024)
#define PROTECTION (PROT_READ | PROT_WRITE)
#ifndef MAP_HUGETLB
#define MAP_HUGETLB 0x40000 /* arch specific */
#endif
#ifndef MAP_HUGE_SHIFT
#define MAP_HUGE_SHIFT 26
#endif
#ifndef MAP_HUGE_MASK
#define MAP_HUGE_MASK 0x3f
#endif
/* Only ia64 requires this */
#ifdef __ia64__
#define ADDR (void *)(0x8000000000000000UL)
#define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB | MAP_FIXED)
#else
#define ADDR (void *)(0x0UL)
#define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB)
#endif
static void check_bytes(char *addr)
{
printf("First hex is %x\n", *((unsigned int *)addr));
}
static void write_bytes(char *addr, size_t length)
{
unsigned long i;
for (i = 0; i < length; i++)
*(addr + i) = (char)i;
}
static int read_bytes(char *addr, size_t length)
{
unsigned long i;
check_bytes(addr);
for (i = 0; i < length; i++)
if (*(addr + i) != (char)i) {
printf("Mismatch at %lu\n", i);
return 1;
}
return 0;
}
int main(int argc, char **argv)
{
void *addr;
int ret;
size_t length = LENGTH;
int flags = FLAGS;
int shift = 0;
if (argc > 1)
length = atol(argv[1]) << 20;
if (argc > 2) {
shift = atoi(argv[2]);
if (shift)
flags |= (shift & MAP_HUGE_MASK) << MAP_HUGE_SHIFT;
}
if (shift)
printf("%u kB hugepages\n", 1 << (shift - 10));
else
printf("Default size hugepages\n");
printf("Mapping %lu Mbytes\n", (unsigned long)length >> 20);
addr = mmap(ADDR, length, PROTECTION, flags, -1, 0);
if (addr == MAP_FAILED) {
perror("mmap");
exit(1);
}
printf("Returned address is %p\n", addr);
check_bytes(addr);
write_bytes(addr, length);
ret = read_bytes(addr, length);
/* munmap() length of MAP_HUGETLB memory must be hugepage aligned */
if (munmap(addr, length)) {
perror("munmap");
exit(1);
}
return ret;
}
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