从虚拟地址转为物理地址

/* 
mtest_dump_vma_list（）：打印出当前进程的各个VMA，这个功能我们简称”listvma” 
mtest_find_vma()： 找出某个虚地址所在的VMA，这个功能我们简称“findvma” 
my_follow_page( )：根据页表，求出某个虚地址所在的物理页面，这个功能我们简称”findpage” 
mtest_write_val(), 在某个地址写上具体数据，这个功能我们简称“writeval”. 
*/ 


#include <linux/module.h> 
#include <linux/kernel.h> 
#include <linux/proc_fs.h> 
#include <linux/string.h> 
#include <linux/vmalloc.h> 
#include <asm/uaccess.h> 
#include <linux/init.h> 
#include <linux/slab.h> 
#include <linux/mm.h> 
#include <linux/vmalloc.h> 
MODULE_LICENSE("GPL"); 
/* 
@如何编写代码查看自己的进程到底有哪些虚拟区？ 
*/ 
static void mtest_dump_vma_list(void) 
{ 
struct mm_struct *mm = current->mm; 
struct vm_area_struct *vma; 
printk("The current process is %s\n",current->comm); 
printk("mtest_dump_vma_list\n"); 
down_read(&mm->mmap_sem); 
for (vma = mm->mmap;vma; vma = vma->vm_next)
{ 
printk("VMA 0x%lx-0x%lx ", vma->vm_start, vma->vm_end); 
if (vma->vm_flags & VM_WRITE) 
printk("WRITE "); 
if (vma->vm_flags & VM_READ) 
printk("READ "); 
if (vma->vm_flags & VM_EXEC) 
printk("EXEC "); 
printk("\n"); 
} 
up_read(&mm->mmap_sem); 
} 
/* 
@如果知道某个虚地址，比如，0×8049000, 
又如何找到这个地址所在VMA是哪个？ 
*/ 

static void  mtest_find_vma(unsigned long addr) 
{ 
struct vm_area_struct *vma; 
struct mm_struct *mm = current->mm; 


printk("mtest_find_vma\n"); 


down_read(&mm->mmap_sem); 
vma = find_vma(mm, addr); 
if (vma && addr >= vma->vm_start) 
{ 
printk("found vma 0x%lx-0x%lx flag %lx for addr 0x%lx\n", 
vma->vm_start, vma->vm_end, vma->vm_flags, addr); 
} 
else 
{ 
printk("no vma found for %lx\n", addr); 
} 
up_read(&mm->mmap_sem); 
} 
/* 
@一个物理页在内核中用struct page来描述。 
给定一个虚存区VMA和一个虚地址addr， 
找出这个地址所在的物理页面page. 
*/ 
static struct page *my_follow_page(struct vm_area_struct *vma, unsigned long addr) 
{ 
pud_t *pud; 
pmd_t *pmd; 
pgd_t *pgd; 
pte_t *pte; 
spinlock_t *ptl; 
struct page *page = NULL; 
struct mm_struct *mm = vma->vm_mm; 
pgd = pgd_offset(mm, addr); 
if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
{ 
goto out; 
} 
pud = pud_offset(pgd, addr); 
if (pud_none(*pud) || unlikely(pud_bad(*pud))) 
goto out; 
pmd = pmd_offset(pud, addr); 
if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
{ 
goto out; 
} 
pte = pte_offset_map_lock(mm, pmd, addr, &ptl); 
if (!pte) 
goto out; 
if (!pte_present(*pte)) 
goto unlock; 
page = pfn_to_page(pte_pfn(*pte)); 
if (!page) 
goto unlock; 
get_page(page); 
unlock: 
pte_unmap_unlock(pte, ptl); 
out: 
return page; 
} 
/* 
@ 根据页表，求出某个虚地址所在的物理页面， 
这个功能我们简称”findpage”.
*/ 
static void   mtest_find_page(unsigned long addr) 
{ 
struct vm_area_struct *vma; 
struct mm_struct *mm = current->mm; 
unsigned long kernel_addr; 
struct page *page; 
printk("mtest_write_val\n"); 
down_read(&mm->mmap_sem); 
vma = find_vma(mm, addr); 
page = my_follow_page(vma, addr); 


if (!page) 
{ 
printk("page not found  for 0x%lx\n", addr); 
goto out; 
} 
printk("page  found  for 0x%lx\n", addr); 
kernel_addr = (unsigned long)page_address(page); 


kernel_addr += (addr&~PAGE_MASK); 
printk("find  0x%lx to kernel address 0x%lx\n", addr, kernel_addr); 


out: 
up_read(&mm->mmap_sem); 
} 
/* 
@你是否有这样的想法， 
给某个地址写入自己所想写的数据？ 
*/ 
static void mtest_write_val(unsigned long addr, unsigned long val) 
{ 
struct vm_area_struct *vma; 
struct mm_struct *mm = current->mm; 
struct page *page; 
unsigned long kernel_addr; 
printk("mtest_write_val\n"); 
down_read(&mm->mmap_sem); 
vma = find_vma(mm, addr); 
if (vma && addr >= vma->vm_start && (addr + sizeof(val)) < vma->vm_end)
{ 
if (!(vma->vm_flags & VM_WRITE))
{ 
printk("vma is not writable for 0x%lx\n", addr); 
goto out; 
}  
page = my_follow_page(vma, addr); 
if (!page)
{ 
printk("page not found  for 0x%lx\n", addr); 
goto out; 
}  


kernel_addr = (unsigned long)page_address(page); 
kernel_addr += (addr&~PAGE_MASK); 
printk("write 0x%lx to address 0x%lx\n", val, kernel_addr); 
*(unsigned long *)kernel_addr = val; 
put_page(page); 
} 
else 
{ 
printk("no vma found for %lx\n", addr); 
} 
out: 
up_read(&mm->mmap_sem); 
} 


static ssize_t mtest_write(struct file *file, const char __user * buffer, size_t count, loff_t * data) 
{  
char buf[128]; 
unsigned long val, val2;
printk("mtest_write  ………..  \n"); 
if (count > sizeof(buf)) 
return -EINVAL; 


if (copy_from_user(buf, buffer, count)) 
return -EINVAL; 


if (memcmp(buf, "listvma", 7) == 0)
{
mtest_dump_vma_list(); 
}
else if (memcmp(buf, "findvma", 7) == 0) 
{ 
if (sscanf(buf + 7, "%lx", &val) == 1)
{ 
mtest_find_vma(val); 
} 
} 
else if (memcmp(buf, "findpage", 8) == 0)
{ 
if (sscanf(buf + 8, "%lx", &val) == 1) 
{ 
mtest_find_page(val); 
}
//my_follow_page(vma, addr); 
} 
else  if (memcmp(buf, "writeval", 8) == 0) 
{ 
if (sscanf(buf + 8, "%lx %lx", &val, &val2) == 2)
{ 
mtest_write_val(val, val2); 
} 
} 
return count; 
} 


static struct file_operations proc_mtest_operations =
{ 
.write        = mtest_write 
}; 
static struct proc_dir_entry *mtest_proc_entry; 

//整个操作我们以模块的形式实现，因此，模块的初始化和退出函数如下： 
static int __init mtest_init(void) 
{ 
mtest_proc_entry = create_proc_entry("mtest", 0777, NULL); 
if (mtest_proc_entry == NULL)
{ 
printk("Error creating proc entry\n"); 
return -1; 
} 
printk("create the filename mtest mtest_init sucess\n"); 
mtest_proc_entry->proc_fops = &proc_mtest_operations; 
return 0; 
} 

static void __exit mtest_exit(void) 
{ 
printk("exit the module……mtest_exit \n"); 
remove_proc_entry("mtest", NULL); 
} 
MODULE_LICENSE("GPL"); 
MODULE_DESCRIPTION("mtest"); 
MODULE_AUTHOR("Zou Nan hai"); 

module_init(mtest_init); 
module_exit(mtest_exit);