Nguyen Ho Huu Nghia 1751013 - 17APCS2
Dao Hieu 1751005 - 17APCS1
Nguyen Truong Vinh Thuyen 1751042 - 17APCS1
cd ./random-number-char-dev-driver
make all
sudo rmmod random_number_driver
sudo insmod random_number_driver.ko
dmesg # see if the module is loaded
sudo chmod 666 /dev/random_number_char_dev
The string returned has 11 characters, if the random number does not take up 11 characters, space is padded at the front
- An example way to run is through
cat
sudo cat /dev/random_number_char_dev
Random function random a signed integer and convert it to a char array and return it.
char *random(void)
{
const int MAX_LENGTH = 11;
int i;
// generate random number as integer
get_random_bytes(&i, sizeof(i));
printk("%d", i);
// count the number of digits (including '-')
int t = i, c = 0;
if (t < 0) {
t = -t;
c = 1;
}
while (t > 0) {
t = t / 10;
++c;
}
// allocate string
char *str = kzalloc(MAX_LENGTH, GFP_KERNEL);
int index = 0;
// pad space at the start
int remaining = MAX_LENGTH - c, j = 0;
while (j++ < remaining) {
str[index++] = ' ';
}
// add '-' (if applicable)
if (i < 0) {
str[index] = '-';
i = i * -1;
++index;
}
// extract the rest of the digits (these digits are in the wrong direction)
char *temp = kzalloc(c + 1, GFP_KERNEL);
int temp_index = 0;
while (i > 0) {
temp[temp_index] = (char)(i % 10 + '0');
i = i / 10;
++temp_index;
}
// revert the digits to the right direction
int k = temp_index - 1;
while(k >= 0) {
str[index++] = temp[k--];
}
printk("Final random number: %s", str);
return str;
}The source code is in ./random-number-char-dev-driver
Kbuild+Makefile: keep the instructions to compilerandom_number_driver.candrandom_number_driver.hinto loadable object filesrandom_number_driver.h: contains configuration for the character device. More details can be found in the comments in the source code.random_number_driver.c: the main code for the driver. The overall structure of the file is going to be presented below. However, for more detailed view of the operations inside each funciton, please refer to the comments in the source code.- Structs:
- vchar_dev: containing the registers as char arrays for the character device.
- vchar_driver: containing the data structures used for the driver
- Device specific block: codes instructing the CPU to interact with the character device
- OS specific block: codes interacting with the OS to allocate resources and register the driver's entry point to the OS.
- Structs: