打印super_block结构中的一些域的值

#include<linux/module.h>

#include<linux/fs.h>

#include<linux/init.h>

#include<linux/list.h>

#include<linux/spinlock.h>

#include<linux/kdev_t.h>

#define SUPER_BLOCKS_ADDRESS 0xffffffff81c77670

#define SB_LOCK_ADDRESS 0xffffffff820137b0

static int __init my_init(void)

{

struct super_block *sb;

struct list_head *pos;

struct list_head *linode;

struct inode *pinode;

unsigned long long count = 0;

printk("\nPrint some fields of super_blocks:\n");

spin_lock((spinlock_t *)SB_LOCK_ADDRESS);

list_for_each(pos, (struct list_head *)SUPER_BLOCKS_ADDRESS) {

sb = list_entry(pos, struct super_block, s_list);

printk("dev_t: %d : %d", MAJOR(sb->s_dev), MINOR(sb->s_dev));

printk(" file_type name: %s\n",sb->s_type->name);

list_for_each(linode, &sb->s_inodes) {

pinode=list_entry(linode,struct inode,i_sb_list);

count++;

printk(" %lu\t",pinode->i_ino);

}

}

spin_unlock((spinlock_t *)SB_LOCK_ADDRESS);

printk("The number of inodes: %llu\n",sizeof(struct inode) *count);

return 0;

}

static void __exit my_exit(void)

{

printk("unloading...\n");

}

module_init(my_init);

module_exit(my_exit);

MODULE_LICENSE("GPL");

在写代码之前需要先找到super_blocks和sb_lock的地址，操作如下：

$ cat /proc/kallsyms | grep super_blocks

ffffffff81c77670 d super_blocks

$ cat /proc/kallsyms | grep sb_lock

ffffffff820137b0 b sb_lock

实际上super_blocks和sb_lock在fs.h和spinlock.h头文件中对此已经定义。但是，在linux内核中，并不是每个变量和函数都可以在其他子系统和模块中被引用，只有导出后才能被引用，所以才需要上述的操作导出其地址。