Vortragsfolien, Beispiele, Tafelbilder und Notizen 29.4.2024

20240429/Makefile

+obj-m += chardev-5.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

20240429/bs-20240429.tex

+% bs-20240429.pdf - Lecture Slides on Operating Systems
+% Copyright (C) 2014, 2015, 2016, 2017, 2018, 2019, 2020, 2021, 2022, 2023, 2024  Peter Gerwinski
+%
+% This document is free software: you can redistribute it and/or
+% modify it either under the terms of the Creative Commons
+% Attribution-ShareAlike 3.0 License, or under the terms of the
+% GNU General Public License as published by the Free Software
+% Foundation, either version 3 of the License, or (at your option)
+% any later version.
+%
+% This document is distributed in the hope that it will be useful,
+% but WITHOUT ANY WARRANTY; without even the implied warranty of
+% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+% GNU General Public License for more details.
+%
+% You should have received a copy of the GNU General Public License
+% along with this document.  If not, see <http://www.gnu.org/licenses/>.
+%
+% You should have received a copy of the Creative Commons
+% Attribution-ShareAlike 3.0 Unported License along with this
+% document.  If not, see <http://creativecommons.org/licenses/>.
+
+\documentclass[10pt,t]{beamer}
+
+\usepackage{pgslides}
+\usepackage{tikz}
+
+\title{Treiberentwicklung,\\[\medskipamount]Echtzeit- und Betriebssysteme}
+\author{Prof.\ Dr.\ rer.\ nat.\ Peter Gerwinski}
+\date{29.\ April 2024}
+
+\begin{document}
+
+\maketitleframe
+
+%\nosectionnonumber{\inserttitle}
+\nosectionnonumber{Treiberentwicklung, Echtzeit- und Betriebssysteme}
+
+\begin{frame}
+
+  \shownosectionnonumber
+
+  \begin{itemize}
+    \item[\textbf{1}] \textbf{Einführung}
+    \item[\textbf{2}] \textbf{Unix}
+    \item[\textbf{3}] \textbf{Treiberentwicklung}
+      \begin{itemize}
+        \color{medgreen}
+        \item[3.1] Mikrocontroller
+        \item[3.2] Betriebssysteme ohne Speicherschutz
+        \item[3.3] Linux-Kernel-Module
+        \color{red}
+        \item[3.4] Die glibc-Systembibliothek
+        \item[3.5] Der Linux-Kernel
+      \end{itemize}
+    \vspace{-\smallskipamount}
+    \item[\textbf{\dots}]
+  \end{itemize}
+
+\end{frame}
+
+\setcounter{section}{2}
+\section{Treiberentwicklung}
+
+\begin{frame}[fragile]
+
+  \showsection
+
+  \subsection{Mikrocontroller}
+  \showsubsection
+  \vspace{-\medskipamount}
+
+  \begin{itemize}
+    \item
+      Direkter Zugriff auf Speicher, I/O-Ports und Interrupts
+  \end{itemize}
+
+  \bigskip
+
+  \subsection{Betriebssysteme ohne Speicherschutz}
+  \showsubsection
+  \vspace{-\medskipamount}
+
+  \begin{itemize}
+    \item
+      FreeDOS (früher: PC-DOS, MS-DOS, DR-DOS, Novell-DOS,\\
+      aber auch Apple-DOS, Commodore-Kernal, \dots):\\[\smallskipamount]
+      Direkter Zugriff auf Speicher, I/O-Ports und Interrupts
+%    \pause
+    \medskip
+    \item
+      Bildschirm (Textmodus): ab Speicherzelle \lstinline{B800:0000}\\
+      abwechselnd Zeichen (CP\,437) und Attribut (Farbe, Hintergrund)
+%    \pause
+    \medskip
+    \item
+      Bildschirm (Grafikmodus): später
+  \end{itemize}
+
+\end{frame}
+
+\subsection{Linux-Kernel-Module}
+
+\begin{frame}[fragile]
+%  \showsection
+  \showsubsection
+  \begin{itemize}
+    \item
+      Kommunikation mit Betriebssystem über Gerätedateien,\\
+      z.\,B.\ \newterm{char devices}
+    \medskip
+    \item
+      \lstinline{#include <linux/module.h>}\\
+      \lstinline{#include <linux/kernel.h>}
+    \item
+      Zwei "`Hauptprogramme"': \lstinline{init_module()}, \lstinline{cleanup_module()}
+    \item
+      \lstinline{printk()} statt \lstinline{printf()}
+    \item
+      Compilieren mit speziellem \file{Makefile}
+%    \pause
+    \item
+      Angabe der Lizenz ist wichtig: \lstinline{MODULE_LICENSE()}
+    \medskip
+    \item
+      Kernel-Module können (via \newterm{udev\/})
+      Gerätedateien beim Laden anlegen\\
+      und beim Entladen wieder entfernen.
+  \end{itemize}
+\end{frame}
+
+\end{document}

20240429/bs-20240429.txt

+https://www.kernel.org/doc/html/latest/driver-api/infrastructure.html?highlight=device_create
+
+  device_create() liefert im Fehlerfall nicht NULL zurück, sondern einen ERR_PTR.
+
+https://www.kernel.org/doc/html/latest/core-api/kernel-api.html#c.ERR_PTR
+
+  Auswertung mit:
+
+    bool IS_ERR_OR_NULL(__force const void *ptr)
+
+        Detect an error pointer or a null pointer.
+
+    Parameters
+
+    __force const void *ptr
+
+        The pointer to check.
+
+    Description
+
+    Like IS_ERR(), but also returns true for a null pointer.
+

20240429/chardev-5.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 (IS_ERR_OR_NULL (chr_dev))
+        {
+            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-3 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;
+}

20240429/hello-01.c

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

20240429/hello-02.c

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

20240429/io-ports-and-interrupts.pdf

+../common/io-ports-and-interrupts.pdf
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20240429/logo-hochschule-bochum-cvh-text.pdf

+../common/logo-hochschule-bochum-cvh-text.pdf
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20240429/logo-hochschule-bochum.pdf

+../common/logo-hochschule-bochum.pdf
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20240429/os-layers-0-planet.jpg

+../common/os-layers-0-planet.jpg
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20240429/os-layers-1-model.jpg

+../common/os-layers-1-model.jpg
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20240429/os-layers-2-module.jpg

+../common/os-layers-2-module.jpg
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20240429/os-layers-3-glibc.jpg

+../common/os-layers-3-glibc.jpg
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20240429/os-layers-5-kernel.jpg

+../common/os-layers-5-kernel.jpg
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20240429/pgslides.sty

+../common/pgslides.sty
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