Created
June 23, 2020 17:37
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obj-m += memory.o | |
all: | |
make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules | |
clean: | |
make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean | |
install: | |
sudo insmod memory.ko | |
uninstall: | |
sudo rmmod memory | |
mknod: | |
sudo mknod /dev/memory c 60 0 | |
sudo chmod 666 /dev/memory |
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/* Necessary includes for device drivers */ | |
#include <linux/init.h> | |
#include <linux/module.h> | |
#include <linux/kernel.h> /* printk() */ | |
#include <linux/slab.h> /* kmalloc() */ | |
#include <linux/fs.h> /* everything... */ | |
#include <linux/errno.h> /* error codes */ | |
#include <linux/types.h> /* size_t */ | |
#include <linux/proc_fs.h> | |
#include <linux/fcntl.h> /* O_ACCMODE */ | |
#include <asm/uaccess.h> /* copy_from/to_user */ | |
#include <linux/sched.h> | |
MODULE_LICENSE("Dual BSD/GPL"); | |
void memory_exit(void); | |
int memory_init(void); | |
/* Structure that declares the usual file */ | |
/* access functions */ | |
ssize_t memory_write(struct file *filp, const char *buf, size_t count, loff_t *f_pos); | |
ssize_t memory_read(struct file *filp, char *buf, size_t count, loff_t *f_pos); | |
int memory_open(struct inode *inode, struct file *filp); | |
int memory_release(struct inode *inode, struct file *filp); | |
struct file_operations memory_fops = { | |
.read = memory_read, | |
.write = memory_write, | |
.open = memory_open, | |
.release = memory_release | |
}; | |
/* Declaration of the init and exit functions */ | |
module_init(memory_init); | |
module_exit(memory_exit); | |
/* Global variables of the driver */ | |
/* Major number */ | |
int memory_major = 60; | |
/* Buffer to store data */ | |
char *memory_buffer; | |
int memory_init(void) { | |
int result; | |
/* Registering device */ | |
result = register_chrdev(memory_major, "memory", &memory_fops); | |
if (result < 0) { | |
printk( | |
"<1>memory: cannot obtain major number %d\n", memory_major); | |
return result; | |
} | |
/* Allocating memory for the buffer */ | |
memory_buffer = kmalloc(1, GFP_KERNEL); | |
if (!memory_buffer) { | |
result = -ENOMEM; | |
goto fail; | |
} | |
memset(memory_buffer, 0, 1); | |
printk("<1>Inserting memory module\n"); | |
return 0; | |
fail: | |
memory_exit(); | |
return result; | |
} | |
void memory_exit(void) { | |
/* Freeing the major number */ | |
unregister_chrdev(memory_major, "memory"); | |
/* Freeing buffer memory */ | |
if (memory_buffer) { | |
kfree(memory_buffer); | |
} | |
printk("<1>Removing memory module\n"); | |
} | |
int memory_open(struct inode *inode, struct file *filp) { | |
/* Success */ | |
return 0; | |
} | |
int memory_release(struct inode *inode, struct file *filp) { | |
/* Success */ | |
return 0; | |
} | |
static DECLARE_WAIT_QUEUE_HEAD(wq); | |
static volatile int flag = 0; | |
ssize_t memory_read(struct file *filp, char *buf, | |
size_t count, loff_t *f_pos) { | |
printk("<1>going to sleep\n"); | |
flag = 0; | |
//wait_event_interruptible(wq, flag != 0); | |
wait_event(wq, flag != 0); | |
printk("<1>Reading from memory module\n"); | |
/* Transfering data to user space */ | |
raw_copy_to_user(buf,memory_buffer,1); | |
/* Changing reading position as best suits */ | |
if (*f_pos == 0) { | |
*f_pos+=1; | |
return 1; | |
} else { | |
return 0; | |
} | |
} | |
ssize_t memory_write( struct file *filp, const char *buf, | |
size_t count, loff_t *f_pos) { | |
char *tmp; | |
printk("<1>wake someone up\n"); | |
flag = 1; | |
//wake_up_interruptible(&wq); | |
wake_up(&wq); | |
printk("<1>Writting to memory module\n"); | |
tmp=buf+count-1; | |
raw_copy_from_user(memory_buffer,tmp,1); | |
return 1; | |
} |
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