Treiberenwicklung in C HW 4

Question 1

What is the file format of compiled Kernel modules?

Answer 1

.ko files are now used instead of .o files. They contain an additional .modinfo section that holds additional information about the module.

Question 2

In the VM, load the module using either modprobe (requires previous depmod) or insmod

What is the difference between the two?

Answer 2

insmod is a simple program to insert a module into the kernel. It can not handle module dependencies and will report only the most general errors.

On the other hand modprobe is a more advanced tool that intelligently adds or removes modules. It automatically looks at the /lib/modules/uname -r directory.

Question 3

What does depmod do?

Answer 3

It generates a modules.dep file which handles the dependencies between modules easily. It checks the /lib/modules/uname -r directory for each module and handles their symbols.

Question 4

Welche Tools muss Busybox bereitstellen um mit Modulen umzugehen?

Answer 4

modprobe
modinfo
rmmod
lsmod
insmod
dmesg: Das dmesg (display message) Kommando zeigt unter Linux den Inhalt des Kernel Ring Buffers. Die darin enthaltenen Meldungen werden typischerweise von Gerätetreibern erzeug
depmod

Question 5

Welche Makros werden für die grundsätzliche Entwicklung von Modulen verwendet?

Answer 5

MODULE_LICENSE(“GPL”);
MODULE_AUTHOR(AUTHOR);
MODULE_DESCRIPTION(“Simple Hello World example”);

Question 6

Wie sehen die Bodys von ModInit und ModExit aus?

Answer 6

static int __init ModInit(void)

static void __exit ModExit(void)

Question 7

Was ist die Major Number?

Answer 7

The major number identifies the driver associated with the device. For example, /dev/null and /dev/zero are both managed by driver 1, whereas virtual consoles and serial terminals are managed by driver 4; similarly, both vcs1 and vcsa1 devices are managed by driver 7. The kernel uses the major number at open time to dispatch execution to the appropriate driver.

Question 8

Was ist die Minor Number?

Answer 8

The minor number is used only by the driver specified by the major number; other parts of the kernel don’t use it, and merely pass it along to the driver. It is common for a driver to control several devices (as shown in the listing); the minor number provides a way for the driver to differentiate among them.

Question 9

Wie initialisiert man einen Buffer in Modulen?

Answer 9

buffer = (char*)kmalloc(sizeof(char) * buffersize, GFP_KERNEL);

Question 10

Was ist beim ModExit zusätzlich zu beachten?

Answer 10

Offene Ressourcen schließen.

Question 11

Was machen die Devices null & zero

Answer 11

/dev/zero bezeichnet eine virtuelle Gerätedatei auf Unix-artigen Betriebssystemen, die beim Lesezugriff die angeforderte Anzahl an Null-Bytes (Nullzeichen) zurückliefert.

Wird /dev/null bei der Ausgabe adressiert, wird ein auszugebener Datenstrom verworfen. Beim Lesezugriff darauf (Eingabe) wird ein einzelnes End-of-File-Zeichen (EOF) ausgegeben.