Checkpoint4

// cpuinfo.c
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <asm/uaccess.h>

/*
static inline void native_cpuid(unsigned int *eax, unsigned int *ebx, unsigned int *ecx, unsigned int *edx) {
// ecx is often an input as well as an output.
asm volatile("cpuid"
	: "=a" (*eax),
		"=b" (*ebx),
		"=c" (*ecx),
		"=d" (*edx)
	: "0" (*eax), "2" (*ecx)
	: "memory");
}
*/

MODULE_LICENSE("GPL");
MODULE_AUTHOR("EIEI");
MODULE_DESCRIPTION("\"cpuinfo\" Character Device");

#define DEVICENAME "cpuinfo"
static int dev_major;
static int dev_open =0;
static char *f_ptr;

static int device_open(struct inode *, struct file *);
static int device_release(struct inode *inode, struct file *file);
static ssize_t device_read(struct file *, char *, size_t, loff_t *);
// File operations structor
// Only implement those that will be used.
static struct file_operations dev_fops = {
	.read = device_read,
	.open = device_open,
	.release = device_release
};

int init_module(void) {
	printk(KERN_INFO "CPCHAR: dev osinfo init\n");
	dev_major=register_chrdev(0, DEVICENAME, &dev_fops);
	if (dev_major < 0) {
		printk(KERN_ALERT "Fail register_chrdev osinfo with %d\n",dev_major);
		return dev_major;
	}
	printk(KERN_INFO "Device MajorNumber %d.\n", dev_major);
	printk(KERN_INFO "To create a device file:\n");
	printk(KERN_INFO "\t'mknod /dev/%s c %d 0'.\n", DEVICENAME, dev_major);
	printk(KERN_INFO "Try varying minor numbers.\n");
	printk(KERN_INFO "Please remove the device file and module when done.\n");
	/* * non 0 - means init_module failed */
	return 0;
}

void cleanup_module(void) {
	printk(KERN_INFO "CPCHAR: dev osinfo cleanup\n");
	unregister_chrdev(dev_major, DEVICENAME);
}

static int device_open(struct inode *inode, struct file *file) {
	if (dev_open)
		return -EBUSY; dev_open++;
	printk(KERN_INFO "dev minor %d\n", MINOR(inode->i_rdev));

	// Code snippet
	unsigned eax, ebx, ecx, edx;
	// for obtaining the features
	eax = 0; /* processor info and feature bits */
	native_cpuid(&eax, &ebx, &ecx, &edx);

	char str1[100], f_data0[1000];
	snprintf(str1, 100, "Vendor ID ");
	strncat (f_data0, str1, 1000);
	snprintf(str1, 100, "%c%c%c%c", (ebx) & 0xFF, (ebx>>8) & 0xFF, (ebx>>16) & 0xFF, (ebx>>24) & 0xFF);
	strncat (f_data0, str1, 1000);
	snprintf(str1, 100, "%c%c%c%c", (edx) & 0xFF, (edx>>8) & 0xFF, (edx>>16) & 0xFF, (edx>>24) & 0xFF);
	strncat (f_data0, str1, 1000);
	snprintf(str1, 100, "%c%c%c%c\n", (ecx) & 0xFF, (ecx>>8) & 0xFF, (ecx>>16) & 0xFF, (ecx>>24) & 0xFF);
	strncat (f_data0, str1, 1000);

	eax = 1;
	native_cpuid(&eax, &ebx, &ecx, &edx);
	snprintf(str1, 100, "Stepping %d\n", eax & 0xF);
	strncat (f_data0, str1, 1000);
	snprintf(str1, 100, "Model %d\n", (eax >> 4) & 0xF);
	strncat (f_data0, str1, 1000);
	snprintf(str1, 100, "Family %d\n", (eax >> 8) & 0xF);
	strncat (f_data0, str1, 1000);
	snprintf(str1, 100, "Processor %d\n", (eax >> 12) & 0x3);
	strncat (f_data0, str1, 1000);
	snprintf(str1, 100, "Extended Model %d\n", (eax >> 16) & 0xF);
	strncat (f_data0, str1, 1000);
	snprintf(str1, 100, "Extended Family %d\n", (eax >> 20) & 0xFF);
	strncat (f_data0, str1, 1000);

	eax = 3;
	native_cpuid(&eax, &ebx, &ecx, &edx);
	snprintf(str1, 100, "Serial Number 0x%08x%08x\n", edx, ecx);
	strncat (f_data0, str1, 1000);


	f_ptr=(char * )f_data0;

	// lock module
	try_module_get(THIS_MODULE);
	return 0;
}

static int device_release(struct inode *inode, struct file *file) {
	dev_open--; /* We're now ready for our next caller */
	// release module
	module_put(THIS_MODULE);
	return 0;
}

static ssize_t device_read(struct file *filp,
	char *buffer,
	/* see include/linux/fs.h */
	/* buffer to fill with data */
	/* length of the buffer     */
	size_t length,
	loff_t * offset) {
	int bytes_read=0;
	if (*f_ptr ==0) {
		return 0;
	}
	while (length && *f_ptr) {
		put_user(*(f_ptr++), buffer++); length--;
	bytes_read++;
	}
	return bytes_read;
}