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电梯直达

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发表于 2009-02-13 08:17 |只看该作者 |倒序浏览

需求：实现用mmap访问内核中的一个结构体。
请问怎么做？2.4内核。
内核中结构体的地址是属于内核虚拟地址？还是？

这是我模仿ldd2写的，但是没有效果：（试图访问buff）

#ifndef __KERNEL__
#  define __KERNEL__
#endif
#ifndef MODULE
#  define MODULE
#endif

#include <linux/config.h>
#include <linux/module.h>

#include <linux/kernel.h> /* printk() */
#include <linux/slab.h> /* kmalloc() */
#include <linux/fs.h>    /* everything... */
#include <linux/errno.h> /* error codes */
#include <linux/types.h> /* size_t */
#include <asm/page.h>

#define VMA_OFFSET(vma)  ((vma)->vm_pgoff << PAGE_SHIFT)

static int simple_major = 0;

/*
* Forwards for our methods.
*/
int simple_open (struct inode *inode, struct file *filp);
int simple_release(struct inode *inode, struct file *filp);
int simple_nopage_mmap(struct file *filp, struct vm_area_struct *vma);

/*
* Our various sub-devices.
*/

/* Device 1 uses nopage */
struct file_operations simple_nopage_ops = {
open: simple_open,
release: simple_release,
mmap: simple_nopage_mmap,
};

#define MAX_SIMPLE_DEV 1

struct file_operations *simple_fops[MAX_SIMPLE_DEV] = {
&simple_nopage_ops,
};

/*
* Open the device; all we have to do here is to up the usage count and
* set the right fops.
*/
int simple_open (struct inode *inode, struct file *filp)
{
unsigned int dev = MINOR(inode->i_rdev);

if (dev >= MAX_SIMPLE_DEV)
      return -ENODEV;
filp->f_op = simple_fops[dev];
MOD_INC_USE_COUNT;
return 0;
}

/*
* Closing is even simpler.
*/
int simple_release(struct inode *inode, struct file *filp)
{
MOD_DEC_USE_COUNT;
return 0;
}

/*
* Common VMA ops.
*/

void simple_vma_open(struct vm_area_struct *vma)
{ MOD_INC_USE_COUNT; }

void simple_vma_close(struct vm_area_struct *vma)
{ MOD_DEC_USE_COUNT; }

char buff[4096 * 2];
/*
* The nopage version.
*/
struct page *simple_vma_nopage(struct vm_area_struct *vma,
            unsigned long address, int write_access)
{
struct page *pageptr;
printk("betwen 0x%lx pgoff 0x%lx ", address - vma->vm_start, vma->vm_pgoff);
unsigned long physaddr = (((unsigned long)buff >> PAGE_SHIFT) << PAGE_SHIFT) + address - vma->vm_start
+ (vma->vm_pgoff << PAGE_SHIFT);
printk("address: 0x%lx buff: 0x%lx physaddr: 0x%lx\n", address, buff, physaddr);

/*char *tmp = (char *)physaddr + 0x8a0;
int i = 0;
for(; i < 5; i++)
printk("mmap %c", tmp);*/
pageptr = virt_to_page(physaddr);
get_page(pageptr);
return pageptr;
}

static struct vm_operations_struct simple_nopage_vm_ops = {
open: simple_vma_open,
close: simple_vma_close,
nopage:  simple_vma_nopage,
};

int simple_nopage_mmap(struct file *filp, struct vm_area_struct *vma)
{
/*unsigned long offset = VMA_OFFSET(vma);

if (offset >= __pa(high_memory) || (filp->f_flags & O_SYNC))
      vma->vm_flags |= VM_IO;*/
vma->vm_flags |= VM_RESERVED;

vma->vm_ops = &simple_nopage_vm_ops;
simple_vma_open(vma);
printk("mmap\n");
return 0;
}

/*
* Module housekeeping.
*/
static int simple_init(void)
{
int result;

SET_MODULE_OWNER(&simple_nopage_ops);

result = register_chrdev(simple_major, "simple", &simple_nopage_ops);
if (result < 0)
{
      printk(KERN_WARNING "simple: unable to get major %d\n", simple_major);
      return result;
}
int index = 0;
for(; index < 4096 * 2; index++)
buff[index] = 'a' + index % 26;
if (simple_major == 0)
      simple_major = result;
return 0;
}

static void simple_cleanup(void)
{
unregister_chrdev(simple_major, "simple");
}

module_init(simple_init);
module_exit(simple_cleanup);

[ 本帖最后由 hongchunhua 于 2009-2-13 08:58 编辑 ]