/*
 * hugepage-mmap:
 *
 * Example of using huge page memory in a user application using the mmap
 * system call.  Before running this application, make sure that the
 * administrator has mounted the hugetlbfs filesystem (on some directory
 * like /mnt) using the command mount -t hugetlbfs nodev /mnt. In this
 * example, the app is requesting memory of size 256MB that is backed by
 * huge pages.
 *
 * For the ia64 architecture, the Linux kernel reserves Region number 4 for
 * huge pages.  That means that if one requires a fixed address, a huge page
 * aligned address starting with 0x800000... will be required.  If a fixed
 * address is not required, the kernel will select an address in the proper
 * range.
 * Other architectures, such as ppc64, i386 or x86_64 are not so constrained.
 */

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/mman.h>
#include <fcntl.h>

#define FILE_NAME "huge/hugepagefile"
#define LENGTH (256UL*1024*1024)
#define PROTECTION (PROT_READ | PROT_WRITE)

/* Only ia64 requires this */
#ifdef __ia64__
#define ADDR (void *)(0x8000000000000000UL)
#define FLAGS (MAP_SHARED | MAP_FIXED)
#else
#define ADDR (void *)(0x0UL)
#define FLAGS (MAP_SHARED)
#endif

static void check_bytes(char *addr)
{
	printf("First hex is %x\n", *((unsigned int *)addr));
}

static void write_bytes(char *addr)
{
	unsigned long i;

	for (i = 0; i < LENGTH; i++)
		*(addr + i) = (char)i;
}

static int read_bytes(char *addr)
{
	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(void)
{
	void *addr;
	int fd, ret;

	fd = open(FILE_NAME, O_CREAT | O_RDWR, 0755);
	if (fd < 0) {
		perror("Open failed");
		exit(1);
	}

	addr = mmap(ADDR, LENGTH, PROTECTION, FLAGS, fd, 0);
	if (addr == MAP_FAILED) {
		perror("mmap");
		unlink(FILE_NAME);
		exit(1);
	}

	printf("Returned address is %p\n", addr);
	check_bytes(addr);
	write_bytes(addr);
	ret = read_bytes(addr);

	munmap(addr, LENGTH);
	close(fd);
	unlink(FILE_NAME);

	return ret;
}
='get' action='/cgit.cgi/linux/net-next.git/log/sound/oss/bin2hex.c'>
<input type='hidden' name='id' value='926af6273fc683cd98cd0ce7bf0d04a02eed6742'/><select name='qt'>
<option value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/cgit.cgi/linux/net-next.git/log/?id=926af6273fc683cd98cd0ce7bf0d04a02eed6742'>root</a>/<a href='/cgit.cgi/linux/net-next.git/log/sound?id=926af6273fc683cd98cd0ce7bf0d04a02eed6742'>sound</a>/<a href='/cgit.cgi/linux/net-next.git/log/sound/oss?id=926af6273fc683cd98cd0ce7bf0d04a02eed6742'>oss</a>/<a href='/cgit.cgi/linux/net-next.git/log/sound/oss/bin2hex.c?id=926af6273fc683cd98cd0ce7bf0d04a02eed6742'>bin2hex.c</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/cgit.cgi/linux/net-next.git/log/sound/oss/bin2hex.c?id=926af6273fc683cd98cd0ce7bf0d04a02eed6742&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th><th class='left'>Files</th><th class='left'>Lines</th></tr>