# HG changeset patch
# User Eleni Maria Stea <eleni@mutantstargoat.com>
# Date 1494411091 -10800
# Node ID dbbd63da261fcd4f10c5d39a80a8db3e8c04583f

helloworld kernel module and program that reads the /dev/ktest

diff -r 000000000000 -r dbbd63da261f .hgignore
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/.hgignore	Wed May 10 13:11:31 2017 +0300
@@ -0,0 +1,9 @@
+syntax:glob
+*.swp
+*.o
+*.cmd
+*.ko
+*.symvers
+*.order
+*.mod
+*.mod.c
diff -r 000000000000 -r dbbd63da261f ktestmodule/Makefile
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/ktestmodule/Makefile	Wed May 10 13:11:31 2017 +0300
@@ -0,0 +1,9 @@
+obj-m += ktest.o
+
+.PHONY: all
+all:
+	make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules
+
+.PHONY: clean
+clean:
+	make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean
diff -r 000000000000 -r dbbd63da261f ktestmodule/ktest.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/ktestmodule/ktest.c	Wed May 10 13:11:31 2017 +0300
@@ -0,0 +1,91 @@
+#include <asm/uaccess.h>
+#include <linux/fs.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+
+#define DEV_NAME "ktest"
+
+static int ktest_init(void);
+static void ktest_fini(void);
+
+static int ktest_open(struct inode *inode, struct file *file);
+static int ktest_release(struct inode *inode, struct file *file);
+static ssize_t ktest_read(struct file *file, char *buf, size_t buf_size,
+		loff_t *offset);
+
+static int dev_num;
+static struct file_operations ops = {
+	.open = ktest_open,
+	.release = ktest_release,
+	.read = ktest_read
+};
+static int hello_counter;
+
+/* macros */
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("hikiko");
+MODULE_DESCRIPTION("my kernel helloworld");
+
+module_init(ktest_init);
+module_exit(ktest_fini);
+
+static int ktest_init(void)
+{
+	hello_counter = 0;
+
+	/* register character device */
+	if((dev_num = register_chrdev(0, DEV_NAME, &ops)) < 0) {
+		printk(KERN_ALERT "Failed to register character device.\n");
+		return -1;
+	}
+	printk(KERN_INFO "Registered character device. Name: %s number: %d.\n", DEV_NAME, dev_num);
+	return 0;
+}
+
+static void ktest_fini(void)
+{
+	unregister_chrdev(dev_num, DEV_NAME);
+	printk(KERN_INFO "Unregistered character device. Name: %s number: %d.\n", DEV_NAME, dev_num);
+}
+
+static int ktest_open(struct inode *inode, struct file *file)
+{
+	/* 1 device file only => we ignore the params ^ */
+	try_module_get(THIS_MODULE);
+	return 0;
+}
+
+static int ktest_release(struct inode *inode, struct file *file)
+{
+	module_put(THIS_MODULE);
+	return 0;
+}
+
+static ssize_t ktest_read(struct file *file, char *buf, size_t buf_size,
+		loff_t *offset)
+{
+	/* buf = userspace buffer,
+	 * kbuf = kernel buffer */
+
+	char *kbuf;
+	int bytes;
+
+	if(!(kbuf = kmalloc(buf_size, GFP_KERNEL))) {
+		printk(KERN_ALERT "Failed to allocate memory.\n");
+		return -ENOMEM;
+	}
+
+	/* fill kbuf and copy to userspace buf */
+	bytes = snprintf(kbuf, buf_size, "Hello world, num: %d.\n", ++hello_counter);
+
+	if(copy_to_user(buf, kbuf, bytes))
+	{
+		kfree(kbuf);
+		return -EFAULT;
+	}
+
+	kfree(kbuf);
+	return bytes;
+}
diff -r 000000000000 -r dbbd63da261f ktestprogram/Makefile
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/ktestprogram/Makefile	Wed May 10 13:11:31 2017 +0300
@@ -0,0 +1,9 @@
+obj = kprog.o
+CFLAGS = -pedantic -Wall -g
+
+kprog: $(obj)
+	$(CC) -o $@ $^ $(LDFLAGS)
+
+.PHONY: clean
+clean:
+	rm -f $(obj) kprog
diff -r 000000000000 -r dbbd63da261f ktestprogram/kprog.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/ktestprogram/kprog.c	Wed May 10 13:11:31 2017 +0300
@@ -0,0 +1,28 @@
+#include <fcntl.h>
+#include <stdio.h>
+#include <unistd.h>
+
+int main(void)
+{
+	char buf[512];
+	size_t size;
+	int fd;
+
+	if((fd = open("/dev/ktest", O_RDONLY)) == -1) {
+		fprintf(stderr, "Failed to open device ktest.\n");
+		return 1;
+	}
+
+	if((size = read(fd, buf, sizeof buf)) == -1) {
+		fprintf(stderr, "Failed to read from device ktest.\n");
+
+		close(fd);
+		return 1;
+	}
+	printf("num char: %d\n", (int)size);
+
+	buf[size] = 0;
+	printf("quoting kernel: %s", buf);
+	close(fd);
+	return 0;
+}