Vorbereitende Notizen und Beispiele 4.5.2020

20200427/bs-20200427.txt

 27.04.2020, 14:57:44
 ~~~~~~~~~~~~~~~~~~~~
- * am Anfang der Lehrveranstaltung:
+:) am Anfang der Lehrveranstaltung:
    Mikrocontroller, PC früher (DOS): Hardware direkt ansprechen
 
- * letzte Woche: Unix-Shell, einschließlich Shell-Skripte
+:) letzte Woche: Unix-Shell, einschließlich Shell-Skripte
 
  * vom "Mikrocontoller" zur Shell: Bootvorgang
     - Rechner einschalten

20200504/Makefile

+Makefile-2
\ No newline at end of file

20200504/Makefile-0

+TARGET = blink-1
+
+$(TARGET).elf: $(TARGET).c
+	avr-gcc -Wall -Os -c -mmcu=atmega328p $(TARGET).c -o $(TARGET).elf
+
+$(TARGET).hex: $(TARGET).elf
+	avr-objcopy -O ihex $(TARGET).elf $(TARGET).hex
+
+upload: $(TARGET).hex
+	avrdude -P /dev/ttyACM0 -c arduino -p m328p -U flash:w:$(TARGET).hex

20200504/Makefile-1

+hello-1: hello-1.c
+	gcc -Wall -O hello-1.c -o hello-1

20200504/Makefile-2

+obj-m += hellomod-1.o
+obj-m += hellomod-2.o
+obj-m += chardev-1.o
+
+all:
+	make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules
+
+clean:
+	make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

20200504/bs-20200504.txt

+03.05.2020, 33:58:40
+~~~~~~~~~~~~~~~~~~~~
+:) letzte Woche: Bootvorgang
+
+:) letzte Woche: Hardware ansprechen: Kernel-Module
+    - Gerätedateien: Verzeichnis /dev
+       - /dev/null = "virtueller Mülleimer"
+         (Immer leer; was man hineinschreibt, ist weg.)
+       - /dev/pts/24 = Ausgabedatei für ein Bildschirmfenster
+       - /dev/pts/35 = Ausgabedatei für ein anderes Bildschirmfenster
+       - Das "c" in "ls -l" steht für "Character Device"
+         (zeichenorientierte Gerätedatei).
+       - selbst erzeugen: Kernel-Modul schreiben
+    - Struktur eines Kernel-Moduls
+       - "zwei Hauptprogramme": init_module(), cleanup_module()
+       - printk() (in den Kernel-Speicher schreiben)
+         statt printf() (zur Standardausgabe schreiben)
+    - Kernel-Modul compilieren
+       - make: siehe:
+         https://gitlab.cvh-server.de/pgerwinski/hp/raw/master/20191212/hp-20191212.pdf
+       - standardisiertes Makefile: Makefile-2
+       - benötigte Werkzeuge: siehe Skript, Seite 10
+       - Modul laden: sudo insmod ./hellomod-1.ko
+       - Modul entladen:  sudo rmmod ./hellomod-1.ko
+       - Output des Moduls: sudo tail /var/log/kern.log
+       - Lizenz des Moduls angeben. Wenn nicht GPL-kompatibel: Fehlermeldungen.
+
+ * Ergänzung: Das Kernel-Modul legt die Gerätedatei selbst an.
+
+ * Die Software-Schichten dazwischen: Kernel, System-Bibliothek
+   von der Shell bis zur Hardware

20200504/chardev-1.c

+/*
+ *  chardev.c: Creates a read-only char device that says how many times
+ *  you've read from the dev file
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <asm/uaccess.h>	/* for put_user */
+
+/*  
+ *  Prototypes - this would normally go in a .h file
+ */
+int init_module(void);
+void cleanup_module(void);
+static int device_open(struct inode *, struct file *);
+static int device_release(struct inode *, struct file *);
+static ssize_t device_read(struct file *, char *, size_t, loff_t *);
+static ssize_t device_write(struct file *, const char *, size_t, loff_t *);
+
+#define SUCCESS 0
+#define DEVICE_NAME "chardev"	/* Dev name as it appears in /proc/devices   */
+#define BUF_LEN 80		/* Max length of the message from the device */
+
+/* 
+ * Global variables are declared as static, so are global within the file. 
+ */
+
+static int Major;		/* Major number assigned to our device driver */
+static int Device_Open = 0;	/* Is device open?  
+				 * Used to prevent multiple access to device */
+static char msg[BUF_LEN];	/* The msg the device will give when asked */
+static char *msg_Ptr;
+
+static struct file_operations fops = {
+	.read = device_read,
+	.write = device_write,
+	.open = device_open,
+	.release = device_release
+};
+
+/*
+ * This function is called when the module is loaded
+ */
+int init_module(void)
+{
+        Major = register_chrdev(0, DEVICE_NAME, &fops);
+
+	if (Major < 0) {
+	  printk(KERN_ALERT "Registering char device failed with %d\n", Major);
+	  return Major;
+	}
+
+	printk(KERN_INFO "I was assigned major number %d. To talk to\n", Major);
+	printk(KERN_INFO "the driver, create a dev file with\n");
+	printk(KERN_INFO "'mknod /dev/%s c %d 0'.\n", DEVICE_NAME, Major);
+	printk(KERN_INFO "Try various minor numbers. Try to cat and echo to\n");
+	printk(KERN_INFO "the device file.\n");
+	printk(KERN_INFO "Remove the device file and module when done.\n");
+
+	return SUCCESS;
+}
+
+/*
+ * This function is called when the module is unloaded
+ */
+void cleanup_module(void)
+{
+	/* 
+	 * Unregister the device 
+	 */
+	unregister_chrdev(Major, DEVICE_NAME);
+}
+
+/*
+ * Methods
+ */
+
+/* 
+ * Called when a process tries to open the device file, like
+ * "cat /dev/mycharfile"
+ */
+static int device_open(struct inode *inode, struct file *file)
+{
+	static int counter = 0;
+
+	if (Device_Open)
+		return -EBUSY;
+
+	Device_Open++;
+	sprintf(msg, "I already told you %d times Hello world!\n", counter++);
+	msg_Ptr = msg;
+	try_module_get(THIS_MODULE);
+
+	return SUCCESS;
+}
+
+/* 
+ * Called when a process closes the device file.
+ */
+static int device_release(struct inode *inode, struct file *file)
+{
+	Device_Open--;		/* We're now ready for our next caller */
+
+	/* 
+	 * Decrement the usage count, or else once you opened the file, you'll
+	 * never get get rid of the module. 
+	 */
+	module_put(THIS_MODULE);
+
+	return 0;
+}
+
+/* 
+ * Called when a process, which already opened the dev file, attempts to
+ * read from it.
+ */
+static ssize_t device_read(struct file *filp,	/* see include/linux/fs.h   */
+			   char *buffer,	/* buffer to fill with data */
+			   size_t length,	/* length of the buffer     */
+			   loff_t * offset)
+{
+	/*
+	 * Number of bytes actually written to the buffer 
+	 */
+	int bytes_read = 0;
+
+	/*
+	 * If we're at the end of the message, 
+	 * return 0 signifying end of file 
+	 */
+	if (*msg_Ptr == 0)
+		return 0;
+
+	/* 
+	 * Actually put the data into the buffer 
+	 */
+	while (length && *msg_Ptr) {
+
+		/* 
+		 * The buffer is in the user data segment, not the kernel 
+		 * segment so "*" assignment won't work.  We have to use 
+		 * put_user which copies data from the kernel data segment to
+		 * the user data segment. 
+		 */
+		put_user(*(msg_Ptr++), buffer++);
+
+		length--;
+		bytes_read++;
+	}
+
+	/* 
+	 * Most read functions return the number of bytes put into the buffer
+	 */
+	return bytes_read;
+}
+
+/*  
+ * Called when a process writes to dev file: echo "hi" > /dev/hello 
+ */
+static ssize_t
+device_write(struct file *filp, const char *buff, size_t len, loff_t * off)
+{
+	printk(KERN_ALERT "Sorry, this operation isn't supported.\n");
+	return -EINVAL;
+}

20200504/chardev-2.c

+/*
+ *  chardev.c: Creates a read-only char device that says how many times
+ *  you've read from the dev file
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/fs.h>
+#include <asm/uaccess.h>	/* for put_user */
+
+/*  
+ *  Prototypes - this would normally go in a .h file
+ */
+int init_module(void);
+void cleanup_module(void);
+static int device_open(struct inode *, struct file *);
+static int device_release(struct inode *, struct file *);
+static ssize_t device_read(struct file *, char *, size_t, loff_t *);
+static ssize_t device_write(struct file *, const char *, size_t, loff_t *);
+
+struct class *dev_Class;
+struct device *chr_dev;
+
+#define SUCCESS 0
+#define DEVICE_NAME "chardev"	/* Dev name as it appears in /proc/devices   */
+#define BUF_LEN 80		/* Max length of the message from the device */
+
+/* 
+ * Global variables are declared as static, so are global within the file. 
+ */
+
+static int Major;		/* Major number assigned to our device driver */
+static int Device_Open = 0;	/* Is device open?  
+				 * Used to prevent multiple access to device */
+static char msg[BUF_LEN];	/* The msg the device will give when asked */
+static char *msg_Ptr;
+
+static struct file_operations fops = {
+	.read = device_read,
+	.write = device_write,
+	.open = device_open,
+	.release = device_release
+};
+
+/*
+ * This function is called when the module is loaded
+ */
+int init_module(void)
+{
+        Major = register_chrdev(0, DEVICE_NAME, &fops);
+
+	if (Major < 0) {
+	  printk(KERN_ALERT "Registering char device failed with %d\n", Major);
+	  return Major;
+	}
+
+        // Create module class
+        printk(KERN_INFO "Creating device class LCD...\n");
+        dev_Class = class_create(THIS_MODULE,DEVICE_NAME);
+        if( dev_Class == NULL)
+        {
+            printk( KERN_ALERT "Error! Class couldn't be created!\n" );
+            return 1 ;
+        }
+        printk( KERN_INFO "Class created!\n" );
+        // Create device in /dev/...
+        printk(KERN_INFO "Creating device\n");
+        chr_dev = device_create(dev_Class, NULL, MKDEV(Major,0), NULL, DEVICE_NAME);
+
+	printk(KERN_INFO "I was assigned major number %d. To talk to\n", Major);
+	printk(KERN_INFO "the driver, create a dev file with\n");
+	printk(KERN_INFO "'mknod /dev/%s c %d 0'.\n", DEVICE_NAME, Major);
+	printk(KERN_INFO "Try various minor numbers. Try to cat and echo to\n");
+	printk(KERN_INFO "the device file.\n");
+	printk(KERN_INFO "Remove the device file and module when done.\n");
+
+	return SUCCESS;
+}
+
+/*
+ * This function is called when the module is unloaded
+ */
+void cleanup_module(void)
+{
+	/* 
+	 * Unregister the device 
+	 */
+	unregister_chrdev(Major, DEVICE_NAME);
+}
+
+/*
+ * Methods
+ */
+
+/* 
+ * Called when a process tries to open the device file, like
+ * "cat /dev/mycharfile"
+ */
+static int device_open(struct inode *inode, struct file *file)
+{
+	static int counter = 0;
+
+	if (Device_Open)
+		return -EBUSY;
+
+	Device_Open++;
+	sprintf(msg, "I already told you %d times Hello world!\n", counter++);
+	msg_Ptr = msg;
+	try_module_get(THIS_MODULE);
+
+	return SUCCESS;
+}
+
+/* 
+ * Called when a process closes the device file.
+ */
+static int device_release(struct inode *inode, struct file *file)
+{
+	Device_Open--;		/* We're now ready for our next caller */
+
+	/* 
+	 * Decrement the usage count, or else once you opened the file, you'll
+	 * never get get rid of the module. 
+	 */
+	module_put(THIS_MODULE);
+
+	return 0;
+}
+
+/* 
+ * Called when a process, which already opened the dev file, attempts to
+ * read from it.
+ */
+static ssize_t device_read(struct file *filp,	/* see include/linux/fs.h   */
+			   char *buffer,	/* buffer to fill with data */
+			   size_t length,	/* length of the buffer     */
+			   loff_t * offset)
+{
+	/*
+	 * Number of bytes actually written to the buffer 
+	 */
+	int bytes_read = 0;
+
+	/*
+	 * If we're at the end of the message, 
+	 * return 0 signifying end of file 
+	 */
+	if (*msg_Ptr == 0)
+		return 0;
+
+	/* 
+	 * Actually put the data into the buffer 
+	 */
+	while (length && *msg_Ptr) {
+
+		/* 
+		 * The buffer is in the user data segment, not the kernel 
+		 * segment so "*" assignment won't work.  We have to use 
+		 * put_user which copies data from the kernel data segment to
+		 * the user data segment. 
+		 */
+		put_user(*(msg_Ptr++), buffer++);
+
+		length--;
+		bytes_read++;
+	}
+
+	/* 
+	 * Most read functions return the number of bytes put into the buffer
+	 */
+	return bytes_read;
+}
+
+/*  
+ * Called when a process writes to dev file: echo "hi" > /dev/hello 
+ */
+static ssize_t
+device_write(struct file *filp, const char *buff, size_t len, loff_t * off)
+{
+	printk(KERN_ALERT "Sorry, this operation isn't supported.\n");
+	return -EINVAL;
+}

20200504/chardev-3.c

+/*
+ *  chardev.c: Creates a read-only char device that says how many times
+ *  you've read from the dev file
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/fs.h>
+#include <asm/uaccess.h>	/* for put_user */
+
+MODULE_LICENSE("GPL");
+
+/*  
+ *  Prototypes - this would normally go in a .h file
+ */
+int init_module(void);
+void cleanup_module(void);
+static int device_open(struct inode *, struct file *);
+static int device_release(struct inode *, struct file *);
+static ssize_t device_read(struct file *, char *, size_t, loff_t *);
+static ssize_t device_write(struct file *, const char *, size_t, loff_t *);
+
+struct class *dev_Class;
+struct device *chr_dev;
+
+#define SUCCESS 0
+#define DEVICE_NAME "chardev"	/* Dev name as it appears in /proc/devices   */
+#define BUF_LEN 80		/* Max length of the message from the device */
+
+/* 
+ * Global variables are declared as static, so are global within the file. 
+ */
+
+static int Major;		/* Major number assigned to our device driver */
+static int Device_Open = 0;	/* Is device open?  
+				 * Used to prevent multiple access to device */
+static char msg[BUF_LEN];	/* The msg the device will give when asked */
+static char *msg_Ptr;
+
+static struct file_operations fops = {
+	.read = device_read,
+	.write = device_write,
+	.open = device_open,
+	.release = device_release
+};
+
+/*
+ * This function is called when the module is loaded
+ */
+int init_module(void)
+{
+        Major = register_chrdev(0, DEVICE_NAME, &fops);
+
+	if (Major < 0) {
+	  printk(KERN_ALERT "Registering char device failed with %d\n", Major);
+	  return Major;
+	}
+
+        // Create module class
+        printk (KERN_INFO "Creating device class \"chardev\" ...\n");
+        dev_Class = class_create (THIS_MODULE,DEVICE_NAME);
+        if( dev_Class == NULL)
+        {
+            printk (KERN_ALERT "Error! Class couldn't be created!\n");
+            return 1;
+        }
+        printk (KERN_INFO "Class created!\n");
+        // Create device in /dev/...
+        printk (KERN_INFO "Creating device\n");
+        chr_dev = device_create (dev_Class, NULL, MKDEV (Major,0), NULL, DEVICE_NAME);
+        if (chr_dev == NULL)
+        {
+            printk( KERN_ALERT "Error! Device couldn't be created!\n" );
+            return 1 ;
+        }
+
+	return SUCCESS;
+}
+
+/*
+ * This function is called when the module is unloaded
+ */
+void cleanup_module(void)
+{
+        printk(KERN_INFO "module chardev-4 cleanup\n");
+        //Unregister the device
+        if (chr_dev)
+          {
+            printk(KERN_INFO "Unregister device ...\n");
+            device_unregister(chr_dev);
+            printk(KERN_INFO "OK\n");
+          }
+
+        if (dev_Class)
+          {
+            printk(KERN_INFO "Unregister class ...\n");
+            class_unregister(dev_Class);
+            printk(KERN_INFO "OK\n");
+          }
+
+        printk(KERN_INFO "Unregister Chardev ...\n");
+        unregister_chrdev(Major, DEVICE_NAME);
+        printk(KERN_INFO "Device %s unregistered!\n", DEVICE_NAME);
+}
+
+/*
+ * Methods
+ */
+
+/* 
+ * Called when a process tries to open the device file, like
+ * "cat /dev/mycharfile"
+ */
+static int device_open(struct inode *inode, struct file *file)
+{
+	static int counter = 0;
+
+	if (Device_Open)
+		return -EBUSY;
+
+	Device_Open++;
+	sprintf(msg, "I already told you %d times Hello world!\n", counter++);
+	msg_Ptr = msg;
+	try_module_get(THIS_MODULE);
+
+	return SUCCESS;
+}
+
+/* 
+ * Called when a process closes the device file.
+ */
+static int device_release(struct inode *inode, struct file *file)
+{
+	Device_Open--;		/* We're now ready for our next caller */
+
+	/* 
+	 * Decrement the usage count, or else once you opened the file, you'll
+	 * never get get rid of the module. 
+	 */
+	module_put(THIS_MODULE);
+
+	return 0;
+}
+
+/* 
+ * Called when a process, which already opened the dev file, attempts to
+ * read from it.
+ */
+static ssize_t device_read(struct file *filp,	/* see include/linux/fs.h   */
+			   char *buffer,	/* buffer to fill with data */
+			   size_t length,	/* length of the buffer     */
+			   loff_t * offset)
+{
+	/*
+	 * Number of bytes actually written to the buffer 
+	 */
+	int bytes_read = 0;
+
+	/*
+	 * If we're at the end of the message, 
+	 * return 0 signifying end of file 
+	 */
+	if (*msg_Ptr == 0)
+		return 0;
+
+	/* 
+	 * Actually put the data into the buffer 
+	 */
+	while (length && *msg_Ptr) {
+
+		/* 
+		 * The buffer is in the user data segment, not the kernel 
+		 * segment so "*" assignment won't work.  We have to use 
+		 * put_user which copies data from the kernel data segment to
+		 * the user data segment. 
+		 */
+		put_user(*(msg_Ptr++), buffer++);
+
+		length--;
+		bytes_read++;
+	}
+
+	/* 
+	 * Most read functions return the number of bytes put into the buffer
+	 */
+	return bytes_read;
+}
+
+/*  
+ * Called when a process writes to dev file: echo "hi" > /dev/hello 
+ */
+static ssize_t
+device_write(struct file *filp, const char *buff, size_t len, loff_t * off)
+{
+	printk(KERN_ALERT "Sorry, this operation isn't supported.\n");
+	return -EINVAL;
+}

20200504/hello--1.c

+#include <stdio.h>
+
+int main (void)
+{
+  char msg[10];
+  static int counter = 0;
+  sprintf (msg, "I already told you %d times Hello world!\n", counter++);
+  printf ("%s", msg);
+  return 0;
+}

20200504/hello-0.c

+#include <stdio.h>
+
+int main (void)
+{
+  printf ("Hello, world!\n");
+  return 0;
+}

20200504/hello-1.c

+#include <stdio.h>
+
+int main (void)
+{
+  puts ("Hello, world!");
+  return 0;
+}

20200504/hello-2.c

+#include <unistd.h>
+
+int main (void)
+{
+  write (1, "Hello, world!\n", 14);
+  return 0;
+}

20200504/hellomod-1.c

+/*  
+ *  hello-1.c - The simplest kernel module.
+ */
+#include <linux/module.h>	/* Needed by all modules */
+#include <linux/kernel.h>	/* Needed for KERN_INFO */
+
+int init_module(void)
+{
+	printk(KERN_INFO "Hello world 1.\n");
+
+	/* 
+	 * A non 0 return means init_module failed; module can't be loaded. 
+	 */
+	return 0;
+}
+
+void cleanup_module(void)
+{
+	printk(KERN_INFO "Goodbye world 1.\n");
+}

20200504/hellomod-2.c

+/*  
+ *  hello-2.c - The simplest kernel module.
+ */
+#include <linux/module.h>	/* Needed by all modules */
+#include <linux/kernel.h>	/* Needed for KERN_INFO */
+
+MODULE_LICENSE("GPL");
+
+int init_module(void)
+{
+	printk(KERN_INFO "Hello world 2.\n");
+
+	/* 
+	 * A non 0 return means init_module failed; module can't be loaded. 
+	 */
+	return 0;
+}
+
+void cleanup_module(void)
+{
+	printk(KERN_INFO "Goodbye world 2.\n");
+}

20200504/os-layers-1.jpg

+../common/os-layers-1.jpg
\ No newline at end of file

20200504/os-layers-2.jpg

+../common/os-layers-2.jpg
\ No newline at end of file

20200504/os-layers-3.jpg

+../common/os-layers-3.jpg
\ No newline at end of file

20200504/os-layers-4.jpg

+../common/os-layers-4.jpg
\ No newline at end of file