Dump the virtual address and the physical Frame Number of the virtual address in linux kernel

PFNDump.c

#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;

}