cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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hugepage-mmap.c (2127B)

      1// SPDX-License-Identifier: GPL-2.0
      2/*
      3 * hugepage-mmap:
      4 *
      5 * Example of using huge page memory in a user application using the mmap
      6 * system call.  Before running this application, make sure that the
      7 * administrator has mounted the hugetlbfs filesystem (on some directory
      8 * like /mnt) using the command mount -t hugetlbfs nodev /mnt. In this
      9 * example, the app is requesting memory of size 256MB that is backed by
     10 * huge pages.
     11 *
     12 * For the ia64 architecture, the Linux kernel reserves Region number 4 for
     13 * huge pages.  That means that if one requires a fixed address, a huge page
     14 * aligned address starting with 0x800000... will be required.  If a fixed
     15 * address is not required, the kernel will select an address in the proper
     16 * range.
     17 * Other architectures, such as ppc64, i386 or x86_64 are not so constrained.
     18 */
     19
     20#include <stdlib.h>
     21#include <stdio.h>
     22#include <unistd.h>
     23#include <sys/mman.h>
     24#include <fcntl.h>
     25
     26#define FILE_NAME "huge/hugepagefile"
     27#define LENGTH (256UL*1024*1024)
     28#define PROTECTION (PROT_READ | PROT_WRITE)
     29
     30/* Only ia64 requires this */
     31#ifdef __ia64__
     32#define ADDR (void *)(0x8000000000000000UL)
     33#define FLAGS (MAP_SHARED | MAP_FIXED)
     34#else
     35#define ADDR (void *)(0x0UL)
     36#define FLAGS (MAP_SHARED)
     37#endif
     38
     39static void check_bytes(char *addr)
     40{
     41	printf("First hex is %x\n", *((unsigned int *)addr));
     42}
     43
     44static void write_bytes(char *addr)
     45{
     46	unsigned long i;
     47
     48	for (i = 0; i < LENGTH; i++)
     49		*(addr + i) = (char)i;
     50}
     51
     52static int read_bytes(char *addr)
     53{
     54	unsigned long i;
     55
     56	check_bytes(addr);
     57	for (i = 0; i < LENGTH; i++)
     58		if (*(addr + i) != (char)i) {
     59			printf("Mismatch at %lu\n", i);
     60			return 1;
     61		}
     62	return 0;
     63}
     64
     65int main(void)
     66{
     67	void *addr;
     68	int fd, ret;
     69
     70	fd = open(FILE_NAME, O_CREAT | O_RDWR, 0755);
     71	if (fd < 0) {
     72		perror("Open failed");
     73		exit(1);
     74	}
     75
     76	addr = mmap(ADDR, LENGTH, PROTECTION, FLAGS, fd, 0);
     77	if (addr == MAP_FAILED) {
     78		perror("mmap");
     79		unlink(FILE_NAME);
     80		exit(1);
     81	}
     82
     83	printf("Returned address is %p\n", addr);
     84	check_bytes(addr);
     85	write_bytes(addr);
     86	ret = read_bytes(addr);
     87
     88	munmap(addr, LENGTH);
     89	close(fd);
     90	unlink(FILE_NAME);
     91
     92	return ret;
     93}