#include <linux/module.h>	// Needed by all modules
#include <linux/kernel.h>	// KERN_INFO
#include <linux/sched/signal.h>	// for_each_process, pr_info
#include <linux/init.h>
#include <linux/vt.h>
#include <linux/proc_fs.h>	// For proc filesystem
#include <linux/slab.h>

#define MAX_REPORTLEN 4196
char* report;
size_t report_place = 0;

ssize_t return_report(struct file *filp, char *buf, size_t count, loff_t *offp ) 
{
	char* readspot = report + *offp;
	size_t readlen = report_place > count? count:report_place;
	if(*offp >= strlen(report))
			return 0;
	strncpy(buf, readspot, readlen);
	*offp += readlen;
	return readlen;
}

void add_to_report(const char* fmt, ...){
	va_list args;
	va_start(args, fmt);
	report_place += vsnprintf(report + report_place, MAX_REPORTLEN - report_place, fmt, args); 
}

void get_process_info(pid_t target_pid)
{
	struct task_struct* task_list;
	report_place = 0;
	add_to_report("Looking for info on process with pid %d\n", target_pid);
	for_each_process(task_list) 
		if(task_list->pid == target_pid) {
			add_to_report("Found our process, comm = %s\n", task_list->comm);
			add_to_report("recent_used_cpu = %d\n", task_list->recent_used_cpu);
		}
}

// Code 1 indicates a process info lookup
// Argument for code 1 is the pid
long handle_ioctl(struct file*, unsigned int a, unsigned long b)
{
	if(a == 10)
		get_process_info(b);
	else
		printk("Invalid ioctl %d\n", a);
	return 0;
}

struct proc_ops proc_fops = {
	proc_read: return_report,
	proc_ioctl: handle_ioctl
};

int init_module(void)
{
	report = kmalloc(MAX_REPORTLEN, GFP_KERNEL);
	proc_create("process_info", 0, NULL, &proc_fops);
	return 0;
}

void cleanup_module(void)
{
	kfree(report);
	remove_proc_entry("process_info", NULL);
}

MODULE_LICENSE("MIT");