Linux C 内核编程 /proc 编程例子

直接上代码

• proc_demo.c
• 内核版本： 5.4.0-150-generic

#include <linux/module.h>
#include <linux/sched.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/uaccess.h>
#include <linux/slab.h>struct proc_head
{struct list_head lhead;int item_count;int str_count;
};struct proc_item
{struct list_head litem;char *buf;int num;
};struct proc_head *gp_head;// linux/seq_file.h
// void * (*start) (struct seq_file *m, loff_t *pos);
// void (*stop) (struct seq_file *m, void *v);
// void * (*next) (struct seq_file *m, void *v, loff_t *pos);
// int (*show) (struct seq_file *m, void *v);/**
* author:  aran
* fuction: seq_operations -> start
*/
static void *my_seq_start(struct seq_file *m, loff_t *pos)
{struct proc_item *entry;if (0 == *pos){seq_printf(m, "List has %d items, total %d bytes\n", gp_head->item_count, gp_head->str_count);}// get first item++*pos;list_for_each_entry(entry, &gp_head->lhead, litem){if (*pos == entry->num){return entry;}}return NULL;
}/**
* author:  aran
* fuction: seq_operations -> next
*/
static void *my_seq_next(struct seq_file *m, void *v, loff_t *pos)
{struct proc_item *entry;// get next item++*pos;list_for_each_entry(entry, &gp_head->lhead, litem){if (*pos == entry->num){return entry;}}return NULL;
}/**
* author:  aran
* fuction: seq_operations -> stop
*/
static void my_seq_stop(struct seq_file *m, void *v)
{// clean sth.// nothing to do
}/**
* author:  aran
* fuction: seq_operations -> show
*/
static int my_seq_show(struct seq_file *m, void *v)
{struct proc_item *tmp = v;seq_printf(m, "%s", tmp->buf);return 0;
}// global var
static struct seq_operations my_seq_fops = 
{.start	= my_seq_start,.next	= my_seq_next,.stop	= my_seq_stop,.show	= my_seq_show,
};// file_operations
// int (*open) (struct inode *, struct file *)
// ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *)/**
* author:  aran
* fuction: file_operations -> open
*/
static int proc_seq_open(struct inode *inode, struct file *file)
{return seq_open(file, &my_seq_fops);
}/**
* author:  aran
* fuction: file_operations -> write
*/
static ssize_t proc_seq_write(struct file *file, const char __user *buffer, size_t count, loff_t *f_pos)
{struct proc_item *tmp;int ret;// allocate proc_itemtmp = (struct proc_item *)kzalloc(sizeof(*tmp), GFP_KERNEL);if (NULL == tmp){ret = -ENOMEM;goto err_kzalloc1;}INIT_LIST_HEAD(&tmp->litem);// allocate str buftmp->buf = (char *)kzalloc(count, GFP_KERNEL);if (NULL == tmp->buf){ret = -ENOMEM;goto err_kzalloc2;}// 从用户空间获取数据 buffer if (0 != copy_from_user(tmp->buf, buffer, count)){ret = -1;goto err_copy;}list_add(&tmp->litem, &gp_head->lhead);gp_head->item_count++;gp_head->str_count += count;tmp->num = gp_head->item_count; return count;err_copy:kfree(tmp->buf);
err_kzalloc2:kfree(tmp);
err_kzalloc1:return ret;
}// global var
static struct file_operations proc_seq_fops = 
{.owner		= THIS_MODULE,.open		= proc_seq_open,.read		= seq_read,.write		= proc_seq_write,.llseek		= seq_lseek,.release	= seq_release,
};static int __init my_init(void)
{struct proc_dir_entry *file;int ret;// allocate & init proc_headgp_head = (struct proc_head *)kzalloc(sizeof(*gp_head), GFP_KERNEL);if (NULL == gp_head){ret = -ENOMEM;goto err_kzalloc;}gp_head->item_count = 0;gp_head->str_count = 0;INIT_LIST_HEAD(&gp_head->lhead);// create "/proc/proc_seq" filefile = proc_create_data("proc_seq",	// name0666,		// modeNULL,		// parent dir_entry&proc_seq_fops,	// file_operationsNULL		// data);if (NULL == file){printk("Count not create /proc/proc_seq file!\n");ret = -1;goto err_proc_create_data;}printk("init success.\n");return 0;err_proc_create_data:kfree(gp_head);
err_kzalloc:return ret;
}static void __exit my_exit(void)
{struct proc_item *tmp1, *tmp2;remove_proc_entry("proc_seq", NULL);list_for_each_entry_safe(tmp1, tmp2, &gp_head->lhead,litem){list_del(&tmp1->litem);kfree(tmp1->buf);kfree(tmp1);}kfree(gp_head);printk("exit success.\n");
}module_init(my_init);
module_exit(my_exit);MODULE_AUTHOR("yong");
MODULE_LICENSE("GPL");

• Makefile

obj-m:=proc_demo.o      CURRENT_PATH:=$(shell pwd)    
LINUX_KERNEL:=$(shell uname -r)  
LINUX_KERNEL_PATH:=/usr/src/linux-headers-$(LINUX_KERNEL)  all:make -C $(LINUX_KERNEL_PATH) M=$(CURRENT_PATH) modules  #编译模块clean:make -C $(LINUX_KERNEL_PATH) M=$(CURRENT_PATH) clean   #清理

输入 make

执行 insmod proc_demo.ko 即可

end

这个代码例子涉及的东西比较多，不适合入门。但是，如果平时有写这个内核文件 /proc 的话，应该比较容易看懂。至于具体解释以后有时间再写。