TASK07: Implement kmodule with interface to procfs

07_procfs/Makefile

@@ -0,0 +1,9 @@
+KERNELDIR ?= ../../buildroot/buildroot-2021.02.7/output/build/linux-5.10.10/ #WARNING relative path
+
+obj-m := kmodule_proc_fs.o
+
+all:
+	$(MAKE) -C $(KERNELDIR) M=$(PWD) modules
+
+clean:
+	$(MAKE) -C $(KERNELDIR) M=$(PWD) clean

07_procfs/README.md

@@ -0,0 +1,10 @@
+## Lesson 07 - ProcFS interface and orange pi bootup
+
+* Update your existing sysfs kernel module with procfs API:
+* Create folder in procfs file system;
+* Create entry that returns module author name;
+* Create entry that returns amount of "store" callback calls;
+* Create entry that returns amount of "show" callback calls.
+* Build image for orange pi zero
+* Attach console output from your development board
+

07_procfs/console.txt

@@ -0,0 +1,21 @@
+# insmod  /tmp/kmodule_proc_fs.ko 
+# echo "store1" > /sys/kernel/MyObject/list 
+# echo "store2" > /sys/kernel/MyObject/list 
+# echo "store3" > /sys/kernel/MyObject/list 
+# cat /sys/kernel/MyObject/list 
+store3
+
+store2
+
+store1
+
+# cat /proc/MyObject/author 
+Nazarii Kurylko <[email protected]># 
+# cat /proc/MyObject/storecount 
+storecount = 3
+# cat /proc/MyObject/s
+showcount   storecount
+# cat /proc/MyObject/showcount 
+showcount = 1
+# 
+

07_procfs/kmodule_proc_fs.c

@@ -0,0 +1,255 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *Module implements the following task:
+ *Update your existing sysfs kernel module with procfs API:
+ *Create folder in procfs file system;
+ *Create entry that returns module author name;
+ *Create entry that returns amount of "store" callback calls;
+ *Create entry that returns amount of "show" callback calls.
+ *Build image for orange pi zero
+ *Attach console output from your development board
+ */
+
+#include <linux/module.h>
+#include <linux/kobject.h>
+#include <linux/err.h>
+#include <linux/string.h>
+#include <linux/sysfs.h>
+#include <linux/list.h>
+#include <linux/slab.h>
+#include <linux/proc_fs.h>
+
+#define MODULEAUTHOR "Nazarii Kurylko <[email protected]>"
+
+MODULE_AUTHOR(MODULEAUTHOR);
+MODULE_DESCRIPTION("Basic data structures module");
+MODULE_LICENSE("GPL");
+MODULE_VERSION("0.1");
+
+#define MODULE_NAME "MyObject"
+#define FILE_AUTHOR "author"
+#define FILE_SHOWCOUNT "showcount"
+#define FILE_STORECOUNT "storecount"
+#define MAX_NODESS_IN_LIST (100)
+
+static unsigned int nodes_in_list;
+static unsigned int showcount;
+static unsigned int storecount;
+
+LIST_HEAD(list_head);
+
+struct str_node {
+	struct list_head list;
+	char *str_ptr;
+};
+
+static ssize_t myobject_show(struct kobject *kobj, struct kobj_attribute *attr,
+			     char *buf)
+{
+	int bytes = 0;
+	int res = 0;
+	struct str_node *node = NULL;
+	struct str_node *node_temp = NULL;
+
+	// print all string to output
+	list_for_each_entry_safe(node, node_temp, &list_head, list) {
+		res = scnprintf(&buf[bytes], (PAGE_SIZE - bytes), "%s\n",
+				node->str_ptr);
+		if (res <= 0) {
+			pr_debug("myobject: %s->scnprintf returned %d\n",
+				 __func__, res);
+			return -EIO;
+		}
+		bytes += res;
+	}
+
+	showcount++;
+	return bytes + 1; //  +1 - for 0 termination
+}
+
+static ssize_t myobject_store(struct kobject *kobj, struct kobj_attribute *attr,
+			      const char *buf, size_t count)
+{
+	//allocate memory for the struct.
+	struct str_node *new = NULL;
+
+	if (nodes_in_list > MAX_NODESS_IN_LIST) {
+		pr_debug("myobject: maximum number of strings reached %u\n",
+			 nodes_in_list);
+		return -ECANCELED;
+	}
+
+	// if no string return;
+	if (count < 1)
+		return count;
+
+	//alocate the link list node
+	new = kmalloc(sizeof(struct str_node), GFP_KERNEL);
+	if (new == NULL)
+		return -ENOMEM;
+
+	new->str_ptr = NULL; //initialize pointer
+
+	//allocate the memory for string.
+	new->str_ptr = kzalloc(count + 1, GFP_KERNEL);
+	if (new->str_ptr == NULL) {
+		kfree(new);
+		pr_debug("myobject: kzalloc returned error\n");
+		return -ENOMEM;
+	}
+
+	//copy string to allocated buffer
+	memcpy(new->str_ptr, buf, count + 1);
+
+	//next prev pointer initalisation
+	INIT_LIST_HEAD(&new->list);
+
+	//add new node between head and previous node
+	list_add(&(new->list), &list_head);
+
+	nodes_in_list += 1;
+
+	storecount++;
+
+	return count;
+}
+
+static struct kobj_attribute list_attribute =
+	__ATTR(list, 0664, myobject_show, myobject_store);
+
+static struct kobject *myobject_kobj;
+
+static struct proc_dir_entry *proc_dir, *author_file, *showcount_file,
+	*storecount_file;
+
+static ssize_t read_author(struct file *file, char __user *pbuf, size_t count,
+			   loff_t *ppos)
+{
+	int not_copied = copy_to_user(pbuf, MODULEAUTHOR, sizeof(MODULEAUTHOR));
+	*ppos += sizeof(MODULEAUTHOR) - not_copied;
+
+	if (*ppos > sizeof(MODULEAUTHOR))
+		return 0;
+	else
+		return sizeof(MODULEAUTHOR);
+}
+
+static ssize_t read_showcount(struct file *file, char __user *pbuf,
+			      size_t count, loff_t *ppos)
+{
+	char tmp_buff[255];
+	int bytes = scnprintf(tmp_buff, sizeof(tmp_buff), "showcount = %u\n",
+			      showcount);
+
+	int not_copied = copy_to_user(pbuf, tmp_buff, bytes);
+	*ppos += bytes - not_copied;
+
+	if (*ppos > bytes)
+		return 0;
+	else
+		return bytes;
+}
+
+static ssize_t read_storecount(struct file *file, char __user *pbuf,
+			       size_t count, loff_t *ppos)
+{
+	char tmp_buff[255];
+	int bytes = scnprintf(tmp_buff, sizeof(tmp_buff), "storecount = %u\n",
+			      storecount);
+
+	int not_copied = copy_to_user(pbuf, tmp_buff, bytes);
+	*ppos += bytes - not_copied;
+
+	if (*ppos > bytes)
+		return 0;
+	else
+		return bytes;
+}
+
+static struct proc_ops proc_ops_author = {
+	.proc_read = read_author,
+};
+
+static struct proc_ops proc_ops_showcount = {
+	.proc_read = read_showcount,
+};
+
+static struct proc_ops proc_ops_storecount = {
+	.proc_read = read_storecount,
+};
+
+static int myobject_init(void)
+{
+	int res = 0;
+
+	myobject_kobj = kobject_create_and_add(MODULE_NAME, kernel_kobj);
+	if (!myobject_kobj) {
+		pr_debug("myobject: kobject_create_and_add returned error\n");
+		return -ENOMEM;
+	}
+	res = sysfs_create_file(myobject_kobj, &list_attribute.attr);
+	if (res) {
+		pr_debug("myobject: sysfs_create_file returned error\n");
+		kobject_put(myobject_kobj);
+		return -ENOMEM;
+	}
+
+	/* create directory */
+	proc_dir = proc_mkdir(MODULE_NAME, NULL);
+	if (proc_dir == NULL) {
+		pr_debug("myobject: proc_mkdir returned error\n");
+		kobject_put(myobject_kobj);
+		return -ENOMEM;
+	}
+
+	/* create author file */
+	author_file =
+		proc_create(FILE_AUTHOR, 0444, proc_dir, &proc_ops_author);
+	if (author_file == NULL) {
+		pr_debug("myobject: proc_create1 returned error\n");
+		kobject_put(myobject_kobj);
+		return -ENOMEM;
+	}
+
+	/* create showcount file */
+	showcount_file = proc_create(FILE_SHOWCOUNT, 0444, proc_dir,
+				     &proc_ops_showcount);
+	if (showcount_file == NULL) {
+		pr_debug("myobject: proc_create2 returned error\n");
+		kobject_put(myobject_kobj);
+		return -ENOMEM;
+	}
+
+	/* create storecount file */
+	storecount_file = proc_create(FILE_STORECOUNT, 0444, proc_dir,
+				      &proc_ops_storecount);
+	if (storecount_file == NULL) {
+		pr_debug("myobject: proc_create3 returned error\n");
+		kobject_put(myobject_kobj);
+		return -ENOMEM;
+	}
+	return res;
+}
+
+static void myobject_exit(void)
+{
+	struct str_node *node = NULL;
+	struct str_node *node_temp = NULL;
+
+	kobject_put(myobject_kobj);
+
+	//free resources
+	list_for_each_entry_safe(node, node_temp, &list_head, list) {
+		list_del(&node->list);
+		kfree(node->str_ptr);
+		kfree(node);
+	}
+
+	proc_remove(proc_dir);
+	proc_remove(author_file);
+	proc_remove(showcount_file);
+	proc_remove(storecount_file);
+}
+
+module_init(myobject_init);
+module_exit(myobject_exit);