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测试代码代码分析
variable是全局变量，如何在proc操作间传递？总结
测试代码
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/version.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <asm/uaccess.h>
static unsigned int variable;
static struct proc_dir_entry *test_dir, *test_entry;
#if LINUX_VERSION_CODE < KERNEL_VERSION(3, 10, 0)
static int test_proc_read(char *buf, char **start, off_t off, int count,
int *eof, void *data)
{
unsigned int *ptr_var = data;
return sprintf(buf, "test_rw = %u\n", *ptr_var);
}
static int test_proc_write(struct file *file, const char *buffer,
unsigned long count, void *data)
{
unsigned int *ptr_var = data;
*ptr_var = simple_strtoul(buffer, NULL, 10);
return count;
}
#else
static int test_proc_show(struct seq_file *seq, void *v)
{
unsigned int *ptr_var = seq->private;
seq_printf(seq, "%u\n", *ptr_var);
return 0;
}
static ssize_t test_proc_write(struct file *file, const char __user *buffer,
size_t count, loff_t *ppos)
{
struct seq_file *seq = file->private_data;
unsigned int *ptr_var = seq->private;
int err;
char *kbuffer;
if (!buffer || count > PAGE_SIZE - 1)
return -EINVAL;
kbuffer = (char *)__get_free_page(GFP_KERNEL);
if (!kbuffer)
return -ENOMEM;
err = -EFAULT;
if (copy_from_user(kbuffer, buffer, count))
goto out;
kbuffer[count] = '\0';
*ptr_var = simple_strtoul(kbuffer, NULL, 10);
return count;
out:
free_page((unsigned long)buffer);
return err;
}
static int test_proc_open(struct inode *inode, struct file *file)
{
return single_open(file, test_proc_show, PDE_DATA(inode));
}
static const struct file_operations test_proc_fops =
{
.owner = THIS_MODULE,
.open = test_proc_open,
.read = seq_read,
.write = test_proc_write,
.llseek = seq_lseek,
.release = single_release,
};
#endif
static __init int test_proc_init(void)
{
test_dir = proc_mkdir("test_dir", NULL);
if (test_dir) {
#if LINUX_VERSION_CODE < KERNEL_VERSION(3, 10, 0)
test_entry = create_proc_entry("test_rw", 0666, test_dir);
if (test_entry) {
test_entry->nlink = 1;
test_entry->data = &variable;
test_entry->read_proc = test_proc_read;
test_entry->write_proc = test_proc_write;
return 0;
}
#else
test_entry = proc_create_data("test_rw",0666, test_dir, &test_proc_fops, &variable);
if (test_entry)
return 0;
#endif
}
return -ENOMEM;
}
module_init(test_proc_init);
static __exit void test_proc_cleanup(void)
{
remove_proc_entry("test_rw", test_dir);
remove_proc_entry("test_dir", NULL);
}
module_exit(test_proc_cleanup);
MODULE_AUTHOR("Barry Song <baohua@kernel.org>");
MODULE_DESCRIPTION("proc exmaple");
MODULE_LICENSE("GPL v2");
代码分析
variable是全局变量，如何在proc操作间传递？
创建节点 proc_create_data
会生成一个proc_dir_entry，->date 用于保存&variable
static unsigned int variable;
static __init int test_proc_init(void)
test_entry = proc_create_data("test_rw",0666, test_dir, &test_proc_fops, &variable);
pde = __proc_create(&parent, name, mode, 1);
pde->proc_fops = proc_fops;
pde->data = data;
proc_register(parent, pde)
return pde;
结论1：
test_entry->date == &variable
open阶段
PDE_DATA(inode)得到文件对应的proc_dir_entry，保存在：file->private_data->private。
file 与 seq_file
static const struct file_operations test_proc_fops =
{
...
.open = test_proc_open,
...
};
static int test_proc_open(struct inode *inode, struct file *file)
single_open(file, test_proc_show, PDE_DATA(inode));
res = seq_open(file, op);
p = kmem_cache_zalloc(seq_file_cache, GFP_KERNEL);
file->private_data = p;
p->op = op;
((struct seq_file *)file->private_data)->private = data;
所以 file->private_date 的值为一个 struct seq_file *p; p->private = PDE_DATA(inode) 最终， file->private_date->private = PDE_DATA(inode);
PDE_DATA(inode)是什么
struct proc_inode {
struct pid *pid;
int fd;
union proc_op op;
struct proc_dir_entry *pde;
struct ctl_table_header *sysctl;
struct ctl_table *sysctl_entry;
struct proc_ns ns;
struct inode vfs_inode;
};
struct proc_inode {
...
struct proc_dir_entry *pde;
...
}
/*
* General functions
*/
static inline struct proc_inode *PROC_I(const struct inode *inode)
{
return container_of(inode, struct proc_inode, vfs_inode);
}
static inline struct proc_dir_entry *PDE(const struct inode *inode)
{
return PROC_I(inode)->pde;
}
static inline void *__PDE_DATA(const struct inode *inode)
{
return PDE(inode)->data;
}
void *PDE_DATA(const struct inode *inode)
{
return __PDE_DATA(inode);
}
EXPORT_SYMBOL(PDE_DATA);
所以 PDE_DATA(inode)即是 container_of(inode, struct proc_inode, vfs_inode)->pde->data 其中，container_of(inode, struct proc_inode, vfs_inode)->pde 值即为 &test_entry； 那么，container_of(inode, struct proc_inode, vfs_inode)->pde->data 值即为 &test_entry->data； 根据 结论1，可知结论2
PDE_DATA(inode) = &variable
show/write 阶段，
传参为struct seq_file *seq
static int test_proc_show(struct seq_file *seq, void *v)
{
unsigned int *ptr_var = seq->private;
传参为struct file *file
static ssize_t test_proc_write(struct file *file, const char __user *buffer,
size_t count, loff_t *ppos)
{
struct seq_file *seq = file->private_data;
unsigned int *ptr_var = seq->private;
总结
proc_create_data(XXX,XXX,XXX,XXX, void data); single_open(XXX, XXX, void data);
如果需要传递参数, single_open的最后一个传参必须为proc_dir_entry->data, 表示方式有：PDE_DATA(inode)、inode->datat等; 如果不需要传递数据, proc_create_data或single_open其中一个void *data为NULL；
转载于:https://www.cnblogs.com/gaoyang3513/p/10989700.html
