OS Project 0 & 1

National Taiwan University

OS Project 0 & 1

Advisor: Dr. Chih-Wen Hsueh

Student: Tang-Hsun Tu

台灣大學網媒所 / 資工所

Wireless Networking and Embedded Systems Laboratory Real-Time System Software Group

April 21, 2023

/602National Taiwan University

Tang-Hsun Tu

Linux Installation Linux Kernel Compilation System Call Project Hints

Outline


Linux Installation


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Including shells, libraries, tools, compiler, servers, applications.

Ubuntu, Redhat, Fedora, Mandrake, SuSE, Debian, Ubuntu, Gentoo …

This slides are based on Ubuntu 10.04 LTS. 11.04 11.10 Beta Linux 3.0

http://www.ubuntu-tw.org/modules/tinyd0/

Linux Distribution


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Windows can be also installed together. Modify the boot sequence to boot your

computer from CD-ROM. Make sure your hardware and device. A clear head and relaxed mind. Some drinks and food.

Before Installation


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/dev/hda, /dev/hdb, /dev/hdc, … /dev/hda1, /dev/hda2, …

/dev/sda, /dev/scd0, … Mount Points

/ /swap …

Disks and Partitions


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Swap partition is usually twice as RAM when it is less than 1GB.

No more than 4 primary partitions including / partition and swap partition.

If the primary partitions are not enough, you can use logical partitions.

Make sure all your mount points are correct.

Partition Division


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After dividing partitions, you only need to click your mouse.

After installation, reboot and enjoy your Linux!

Installation by text mode is similar to graphic mode.

End of Installation


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Install packages in Ubuntu. apt-cache search xxxx apt-get install xxxx

GNU Compiler Collection. gcc –o test test.c ./test

Makefile. make

Command-line editor. vim

SSH server and client. ssh –oPort=port accout@ip

Some Useful Commands


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Install ssh server. apt-get install ssh

A ssh client on Windows. http://ntu.csie.org/~piaip/pietty/

Some Useful Tools


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鳥哥的私房菜 http://linux.vbird.org/

Ubuntu 正體中文站 http://www.ubuntu-tw.org/

Ubuntu Homepage http://www.ubuntu.com/

Reference


Linux Kernel Compilation


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Kernel is the core of an operating system. Process management Memory management Scheduler Filesystem Virtualization …

What is Linux Kernel?


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You can configure your Linux by compiling a new kernel. Add new features, eg. patch kernel. Support new hardware. Disable functions you don’t need. Develop your own kernel. ...

When Should We Compile Kernel?


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Kernel Website, http://www.kernel.org

You also can download the source codes patched by Ubuntu.

Where to D/L Linux Kernel?


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You need to be root to compile kernel. /usr/src/… sudo -i

Download the necessary tools. apt-get update apt-get install kernel-package gcc libncurses5-dev

automake gcc libc6-dev build-essential Go to System/Administration/synaptic

package Manager or http://www.kernel.org/. Get the kernel source codes e.g. 3.0.1

Prepare Your Kernel Source Code


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Unzip kernel source code. cd /usr/src tar jxvf linux-source-3.X.tar.bz2

You may have many versions of Linux source codes.

Prepare Your Kernel Source Code (Cont)


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There are many ways to configure. make config make menuconfig make xconfig ...

If you do not know how to configure, you can copy the old config file from /boot. make mrproper cp /boot/config-`uname -r` .config make oldconfig make menuconfig

Configure your Kernel


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Configure your Kernel (Cont)


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If you meet some problems (SATA). Device Drivers --->

SCSI device support ---> <*> SCSI device support <*> SCSI disk support

Device Drivers ---> SCSI device support --->

SCSI low-level drivers ---> [*] Serial ATA (SATA) support

Configure your Kernel (Cont)


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The first compilation (about 30min ~ 1.5hr): #make clean #make bzImage #make modules (long time) #make install #make modules_install #mkinitramfs –o /boot/initrd.img-3.x 3.x

do this only if you reinstall modules then reboot!

The second compilation (about 5~10min in our project): #make bzImage #make install then reboot!

Kernel Compilation


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See how many cores or hyper-threading on your machine. cat /proc/cpuinfo | grep processor | wc –l e.g. 4

Compile with the number of jobs (threads). make –j4 bzImage make –j4 modules ...

Speed up Kernel Compilation


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Setup your boot manager. vim /boot/grub/menu.lst

Add the following section (Grub1): title Ubuntu 10.04 LTS, kernel 3.0.1 uuid xxxx kernel /boot/vmlinuz-3.0.1 root=UUID=xxxx ro

splash initrd /boot/initrd.img-3.0.1

Configure your Boot Menu


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Setup your boot manager. vim /boot/grub/grub.cfg

Add the following section (Grub2):

Configure your Boot Menu (Cont)


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鳥哥的私房菜 http://linux.vbird.org/

Google http://www.google.com/

Reference


System Call


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System call is the mechanism used by an application program to request service from the OS.

Users can use it to communicate with kernel. Here are two approaches developing our own

system calls. Using kernel module Modify the source codes of Linux directly

Introduction


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Building system calls in kernel module is more flexible than modifying kernel.

When we want to use our system call, just install our kernel modules. Also, if we don’t need it right away, just remove modules. Modifying kernel is not necessary. (But you still

need to modify your kernel for OS project 1.)

Using Kernel Module


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For sys_call_table, your should extern it in a file such as <top directory to the kernel sources>/arch/x86/kernel/i386_ksyms_32.c.

Export sys_call_table

extern void* sys_call_table[];/*variable should be exported. */ EXPORT_SYMBOL(sys_call_table);

010203


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sys_call_table is read-only after kernel version 2.6.23.

If you want to try this method using kernel version which is higher than 2.6.23, you have to modify your current kernel source codes and recompile it.

Export sys_call_table (Cont)


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Firstly, check your compiled kernel version. uname –a

In x86 32bit vim /usr/src/linux-3.x/arch/x86/kernel/entry_32.S .section .rodata, “a” .section .data, “aw”



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In x86 64bit vim /usr/src/linux-3.x/arch/x86/kernel/syscall_64.c line 22: delete the “const”



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Add to export symbol. vim /usr/src/linux-3.x/kernel/kallsyms.c extern void *sys_call_table; EXPORT_SYMBOL(sys_call_table);



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vim makefile vim myservice.c

Write Your Makefile


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Include and Define.

Extern the “sys_call_table”.

Write your own system call.

Write Kernel Module

#include <linux/kernel.h> /* We're doing kernel work */ #include <linux/module.h> #define __NR_mysyscall 200 /* define the number of our system call */

010203

typedef void (*sys_call_ptr_t)(void);extern sys_call_ptr_t sys_call_table[];sys_call_ptr_t orig_sys_call;

010203

/* Our system call */ asmlinkage int mysyscall(int arg1) { printk("enter mysyscall()\n"); return arg1 * 10; }

0102030405


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Initialize the kernel module.

Extern the “sys_call_table”.

Write Kernel Module (Cont)

/* Initialize the module - replace the system call */ int init_module() { printk("Insert mysyscall module\n"); orig_sys_call = sys_call_table[__NR_mysyscall]; sys_call_table[__NR_mysyscall] = mysyscall; return 0; }

01020304050607

/* Cleanup - unregister the appropriate file from /proc */void cleanup_module() { printk("Remove mysyscall module\n"); sys_call_table[__NR_mysyscall] = orig_sys_call; }

0102030405


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Compile. make

Insert the module to kernel. insmod ./myservice.ko

Remove the module from kernel. rmmod myservice

List the modules in kernel. lsmod

Use Kernel Module


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Write an application to use your system call. vim ap.c

Compile and execute. gcc ap.c –o ap ./ap 10

User Application

#include <stdlib.h>#include <stdio.h>#define _GNU_SOURCE #include <unistd.h>#include <sys/syscall.h>

#define __NR_mysyscall 200

int main(int argc,char *argv[]){ printf("%d\n", syscall(__NR_mysyscall, atoi(argv[1]))); return 0;}

01020304050607080910111213


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Here are two approaches developing our own system calls. Using kernel module Modify the source codes of Linux directly

Build Your Own System Calls


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Create a new file in /usr/src/linux-3.x/kernel/. vim myservice.c

Add your system call.

Write Your System Call

#include <linux/linkage.h>#include <linux/kernel.h>

asmlinkage int sys_myservice(int arg1){ printk("my service is invoked!\n"); return arg1 * 10;}

0102030405060708


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In x86 32bit /usr/src/linux-3.x/arch/x86/include/asm/unistd_32.h

The index must be the last in the list. e.g. #define __NR_myservice 347

Write Your System Call (Cont) - x86_32


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Create an entry (function name) in system call table. /usr/src/linux-3.x/arch/x86/kernel/syscall_table_32.S .long sys_myservice



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In x86 64bit /usr/src/linux-3.x/arch/x86/include/asm/unistd_64.h

The index must be the last in the list. #define __NR_myservice 309 __SYSCALL(__NR_myservice, sys_myservice)



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Define the prototype. /usr/src/linux-3.x/include/linux/syscalls.h asmlinkage int sys_myservice(int arg1);

Write Your System Call (Cont)


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Add to makefile to compile. vim /usr/linux-3.x/kernel/Makefile obj-y += myservice.o

Now, you can recompile your kernel.

Write Your System Call (Cont)


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Write an application to use your system call. vim ap.c

Compile and execute. gcc ap.c –o ap ./ap 10

User Application

#include <stdlib.h>#include <stdio.h>#define _GNU_SOURCE#include <unistd.h>#include <sys/syscall.h>

#define __NR_myservice 309

int main(int argc,char *argv[]){ printf("%d\n", syscall(__NR_myservice, atoi(argv[1]))); return 0;}

01020304050607080910111213


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Socket programming server: socket/bind/listen/accept client: socket/connect

New system calls sendmsg() recvmsg() sendmmsg(), 3.0↑ recvmmsg(), 2.6.33↑

Hints (1/4)


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Since we want measure the number of invoking time of sendmsg()/recvmsg() in sendmmsg()/recvmmsg(), we might need to add counters in /usr/src/Linux-3.x/net/socket.c. e.g. int nr_called_sendmsg;

If you want to use this variable in your system call or kernel module, you have to export it. EXPORT_SYMBOL(nr_called_sendmsg);

printk can print messages in kernel, use dmesg to check.

Hints (2/4)


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Hints (3/4) A generic interface: syscall(int no, ...)

__NR_sendmmsg and __NR_recvmmsg

syscall()

sendmmsg()/recvmmsg()


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Results

Hints (4/4)

server

client

1. syscall number of “recvmmsg()”2. received messages

3. the invoking times of “recvmsg()” in the kernel4. time of invoking recvmmsg()

1. typed message2. syscall number of “sendmmsg()”3. the invoking times of “sendmsg()” in the kernel4. time of invoking sendmmsg()


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LXR, http://rswiki.csie.org/lxr/http/source

Some Useful Tool


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Manpages apt-get install manpages-dev

Some Useful Tool (Cont)


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Kernel Website http://www.kernel.org

Socket Programming http://www.tenouk.com/Module41b.html

LXR http://rswiki.csie.org/lxr/http/source http://lxr.linux.no/linux/

Google http://www.google.com/

Recvmmsg() http://lwn.net/Articles/334532/

Sendmmsg() http://lwn.net/Articles/441169/

Reference


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We set up a desktop PC with virtualization in Lab202. cd /home/lab202/os_cfg Start Xen: ./runxen.sh Start Ubuntu VM: ./runubu.sh or ./runubu2.sh Start WinXP VM: ./runxp.sh Start VGA pass-through WinXP VM:

sudo ./runvgaxp.sh &

You can compile your kernels on the VMs! Create your own VM disk.

dd or qemu-img-xen create vmdisk.img 8G Backups are in /home/lab202/backup. Account and password.

Announced in the courses or send a mail to TA.

Resource in Lab202


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Q & A

Documents

OS Project 0 & 1