Creating directory under /proc in kernel 3.10 and above

In the post Creating a read write proc entry in kernel versions above 3.10 we saw the creation of read write proc entry. In the post we will see how to create folder under /proc and then create a entry under it.

To create a directory under /proc we can make use of the function

struct proc_dir_entry *proc_mkdir(const char *name, struct proc_dir_entry *parent);

Where

name: is the name of the directory to be created. parent: parent is the name of directory under which the new directory has to be created.

To create a directory named "newparent" under /proc we will first declare a string having the name of the new folder

char *dirname="newparent" struct proc_dir_entry *parent

newparent=proc_mkdir(dirname,NULL)

The NULL is passed for parent as we are creating the folder under /proc.

Once the new folder has been created we need to pass the pointer to struct proc_dir_entry to proc_create. The use of proc_create can be seen in the post

proc_create("hello",0,newparent,&proc_fops,NULL)

The full code for the module along with proc creation will be as shown below. Please refer to the post Creating a read write proc entry in kernel versions above 3.10 for more details

proc_dir.c

#include <linux/module.h>#include <linux/kernel.h>#include <linux/proc_fs.h>#include<linux/sched.h>#include <asm/uaccess.h>#include <linux/slab.h> int len,temp; char *msg; char *dirname="newparent"; struct proc_dir_entry *parent; int read_proc(struct file *filp,char *buf,size_t count,loff_t *offp ) { if(count>temp) { count=temp; } temp=temp-count; copy_to_user(buf,msg, count); if(count==0) temp=len; return count; } int write_proc(struct file *filp,const char *buf,size_t count,loff_t *offp) { copy_from_user(msg,buf,count); len=count; temp=len; return count; } struct file_operations proc_fops = { read: read_proc, write: write_proc }; void create_new_proc_entry() { parent=proc_mkdir(dirname,NULL); proc_create("hello",0,parent,&proc_fops); msg=kmalloc(GFP_KERNEL,10*sizeof(char)); } int proc_init (void) { create_new_proc_entry(); return 0; } void proc_cleanup(void) { remove_proc_entry("temp1",NULL); } MODULE_LICENSE("GPL"); module_init(proc_init); module_exit(proc_cleanup);

The makefile for the same

ifneq ($(KERNELRELEASE),) obj-m := proc_rw_3_10.o else KERNELDIR ?= /lib/modules/$(shell uname -r)/build PWD := $(shell pwd) default: $(MAKE) -C $(KERNELDIR) M=$(PWD) modules endif clean: $(MAKE) -C $(KERNELDIR) M=$(PWD) clean

Compile and load the module using

$ make $ insmod proc_dir.ko

If there are no errors then we can find the new proc entry under /proc

$ ls /proc/newparent hello

Thus we can see that under /proc a new folder called newparent has been created in which the proc entry hello has been created. We can read write to this proc entry like other proc entries

$ echo "hi" > /proc/newparent/hello $ cat /proc/newparent/hello hi

Related posts

Creating a read write proc entry in kernel versions above 3.10

Creating read only proc entry in kernel versions above 3.10.

Creating a proc entry - 1