linux kernel project 1

/*
 *Introuduction:
 *  This system call will take a pid as parameter, and get the process virtual address,
 *and physical address which match the pid.
 */
#ifndef __LINUX_PROJECT
#define __LINUX_PROJECT

#include <linux/linkage.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <asm-i386/page.h>
#include <asm-i386/pgtable.h>


asmlinkage long sys_project(unsigned long pid1, unsigned long pid2){
    struct vm_area_struct *vm;  /* loop counter to loop through all vm section */
    struct page *page;
    unsigned long vm_address;   /* the virtual address */
    struct task_struct *p;      /* the process descriptor */
    unsigned long pfn;
    unsigned short flag = 0;
    /*the total page frame is the current system. Do not modified this value. */
    extern unsigned long max_low_pfn;
    printk("total page frame : %lx \n", max_low_pfn);
    printk("host memory size is about\t%lu MB\n", pages_to_mb(max_low_pfn));
    /*
     * loop through the whole process list.
     * I think it is the same as the find_task_by_pid().
     */
    for_each_process(p){
        if (p->pid == pid1){
            flag =1;
            break;
        }
    }
    /* it's time to get the virtual address and physical address of the process */
    if (flag){
        /* check if NULL pointer */
        if(p->mm == NULL || p->mm->pgd == NULL || p->mm->mmap == NULL){
            printk("ptr is NULL\n");
            goto out;
        }
        printk("vm section for process1 pid:%u:\n",pid1);
        /* loop through vm interval */
        for ( vm = p->mm->mmap; vm != NULL; vm = vm->vm_next){
            /* print vm section start and end */
            printk("from 0x%08lx~0x%08lx\n",vm->vm_start,vm->vm_end);
            printk("page frame of the interval : \n");
            for (   vm_address = vm->vm_start;
                vm_address < vm->vm_end;
                vm_address += 0x1000)
            {
                page = follow_page(vm, vm_address, 0);
                if ( page == NULL) continue;
                pfn = page_to_pfn(page);
                printk("0x%x ",pfn);
            }
            printk("\n");
        }
    }
/*if some error happened just jumps to here*/
out:
    return 0;

}

#endif