mmap /dev/mmem0.0c test

mtest.c

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

int
main(int argc, char **argv)
{
	int fd;
	unsigned char *data;

	printf("fopen %s\n", argv[1]);

	fd = open(argv[1], O_RDONLY);
	if (fd == -1) {
		fprintf(stderr, "error:\n open %s: %s\n",
			argv[1], strerror(errno));
		exit(1);
	}

	data = mmap(0, 1, PROT_READ, MAP_PRIVATE, fd, 0);
	if (data == MAP_FAILED) {
		fprintf(stderr, "error:\n mmap %d: \n",
			argv[1], strerror(errno));
		exit(1);
	}

	if (argc > 2)
		printf("data[0] = '%c'\n", data[0]);
}

out.txt

# echo X > test.txt
# ./mtest test.txt Y
fopen test.txt
data[0] = 'X'
# ./mtest /dev/mmem0.0c
fopen /dev/mmem0.0c
# echo $?
0
# ./mtest /dev/mmem0.0c Y
fopen /dev/mmem0.0c 
panic: tlb_exception: invalid user-space access from kernel mode
... (didn't copy this) ...
cpu0: Begin traceback
trace by frame address is not supported
cpu0: End traceback...
rebooting...