截获linux系统调用

#include <linux/sched.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/file.h>

MODULE_LICENSE("GPL");

char *root_fs="/";

typedef int (*readdir_t)(struct file *,void *,filldir_t);
readdir_t orig_root_readdir=NULL;

int myreaddir(struct file *fp,void *buf,filldir_t filldir)
{
       int r;
       printk("<1>You got me partner!\n");
       r=orig_root_readdir(fp,buf,filldir);
       return r;
}

int patch_vfs(const char *p,readdir_t *orig_readdir,readdir_t new_readdir)
{
       struct file *filep;
       filep=filp_open(p,O_RDONLY,0);
       if(IS_ERR(filep))
            return -1;
       if(orig_readdir)
            *orig_readdir=filep->f_op->readdir;

       filep->f_op->readdir=new_readdir;
       struct file_operations *fop = filep->f_op;
       fop->readdir = new_readdir;
       filep->f_op = fop;
       filp_close(filep,0);
       return 0;
}

int unpatch_vfs(const char *p,readdir_t orig_readdir)
{
       struct file *filep;
       filep=filp_open(p,O_RDONLY,0);
       if(IS_ERR(filep))
            return -1;
       filep->f_op->readdir=orig_readdir;
       struct file_operations *fop = filep->f_op;
       fop->readdir = orig_readdir;
       filep->f_op = fop;
       filp_close(filep,0);
       return 0;
}

static int patch_init(void)
{
       patch_vfs(root_fs,&orig_root_readdir,myreaddir);
       printk("<1>VFS is patched!\n");
       return 0;
}
static void patch_cleanup(void)
{
       unpatch_vfs(root_fs,orig_root_readdir);
       printk("<1>VFS is unpatched!\n");
}
module_init(patch_init);
module_exit(patch_cleanup);