CS356 Operating System Projects Spring 2018 Project 1: Android Process Tree
Objectives:
Install and use Android Virtual Devices.
Install NDK, cross compile the program and run it on AVD.
Effectively use Linux system calls for process control and management. Familiarize task_struct
Concurrent execution of processes.
Make sure your system is 64-bits Linux system.
Problem Statement:
1. Install Android Virtual Device (AVD), and create a new AVD.
The links of necessary files are given in [1].
The location of JDK and SDK is up to you. Finally, create the AVD named as “OsPrj-StudentID”, make target as “Android 6.0-API Level 23”. If your system is 64-bit Linux, [2] should to be considered.
2. Install Android NDK, run HelloWorld in your AVD.
The link of NDK is given in [1]. You should download it, and extract it to a proper location.
Add the location of NDK to Environment Variables [4] so that we can use “ndk-build” in
other directory.
Make a directory for HelloWorld project and write a “HelloWorld!” program. The files structure should be:
-Helloworld -JNI
-HelloWorld.c -HelloWorld.h -Android.mk
The content of Android.mk is like this:
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_SRC_FILES := hello.c LOCAL_MODULE := helloARM LOCAL_CFLAGS += -pie -fPIE LOCAL_LDFLAGS += -pie -fPIE LOCAL_FORCE_STATIC_EXECUTABLE := true include $(BUILD_EXECUTABLE)
More information about Android.mk is in [3].
If you do not familiar with the Android.mk, please do not change everything but project name in the Android.mk
Finally, use adb to debug the HelloWorld on AVD.
3. Write a new system call in Linux
In android system, we can use ps to see the information of all process, but we cannot use pstree to see the relationship of those process intuitively like what we can do in Linux. So we need a new system call. The system call you write should take two arguments and return the process tree information in a depth-first-search (DFS) order. The prototype for your system call will be:
int ptree(struct prinfo *buf, int *nr);
You should define struct prinfo as:
struct prinfo {
pid_t parent_pid;
pid_t pid;
pid_t first_child_pid; pid_t next_sibling_pid; long state;
/* process id of parent, set 0 if it has no parent*/ /* process id */
/* pid of youngest child, set 0 if it has no child */
/* pid of older sibling, set 0 if it has no sibling*/ /* current state of process */
long uid; /* user id of process owner */
char comm[64]; /* name of program executed */ };
The argument buf points to a buffer for the process data, and nr points to the size of this buffer (number of entries). The system call copies as many entries of the process tree data to the buffer as possible, and stores the number of entries actually copied in nr.
The original Android kernel does not support module. Therefore, you should use the kernel we supported online [6]. You can learn how to start AVD with a new kernel in [7].
Your system call should return the total number of entries on success (this may be bigger than the actual number of entries copied).
4. Test your new system call
Write a simple C program which calls ptree. Your program should print the entire process tree (in DFS order) using tabs to indent children with respect to their parents. The output format should be:
printf(/* correct number of \t */);
printf(“%s,%d,%ld,%d,%d,%d,%d\n”, p.comm, p.pid, p.state, p.parent_pid, p.first_child_pid, p.next_sibling_pid, p.uid);
5. Test ptree
Generate a new process, output (“StudentIDParent is %d”, pid).
Then generates its child process, output (“StudentIDChild is %d”, pid).
Use execl to execute ptree in the child process，show the relationship between above two process.
6. Caesar Encryption Sever
Caesar cipher is one of the simplest and most widely known encryption techniques. During encryption, each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet. In this problem, we set the number=3.
For example,
Plain: Cipher: Plain: Cipher:
ABCDEFGHIJKLMNOPQRSTUVWXYZ
DEFGHIJKLMNOPQRSTUVWXYZABC
abcdefghijklmnopqrstuvwxyz
defghijklmnopqrstuvwxyzabc
Please develop a Caesar Encryption Server, which receives plaintext from clients and sends the corresponding ciphertext to clients.
Implementation Details:
1. Only the letters need to be encrypted, e.g. How are you? → Krz duh brx?
2. The Server can serve at most 2 clients concurrently, more clients coming have to
wait.
3. The server-side program must be concurrent multi-threaded. Pay attention, not
multi-process!
4. Client inputs :q to end the service.
5. For simplicity, you can execute one server and multiple clients in one host.
6. Before you start this problem, I highly recommend you to read these two pages:
http://www.yolinux.com/TUTORIALS/LinuxTutorialPosixThreads.html
http://www.linuxhowtos.org/C_C++/socket.htm
All you need about multi-thread and network programming in Linux can be found in the pages above.
7. We provide the code framework of Server-side and Client-side for you (See PPT).
8. Only 2 source files are needed: client.c and server.c.
9. For your test, please start server-side program first, then start client-side program!
Material to be submitted:
1. Compress the source code of the programs into Prj1+StudentID.tar file. It contains all
*.c, *.h and Android.mk files. Use meaningful names for the file so that the contents of the file are obvious. Enclose a README file that lists the files you have submitted along with a one sentence explanation. Call it Prj1README.
2. Only internal documentation is needed. Please state clearly the purpose of each program at the start of the program. Add comments to explain your program. (-5 points, if insufficient.)
3. Test runs: It is very important that you show that your program works for all possible inputs. Submit online a single typescript file clearly showing the working of all the programs for correct input as well as graceful exit on error input.
4. Send your Prj1+StudentID.tar file to sjtuldy@sjtu.edu.cn and liyig1114@qq.com.
5. Due date: Apr. 18, 2018, submit on-line before midnight.
Appendix
[1] Official Download
JDK: www.oracle.com/technetwork/java/javase/downloads/index.html
SDK: http://developer.android.com/sdk/index.html#Other
NDK: http://developer.android.com/ndk/downloads/index.html#download
The complete version (no need to download anything from Google) we supply: SDK:http://www.cs.sjtu.edu.cn/~fwu/teaching/res/android-sdk-linux.tar.gz NDK:http://www.cs.sjtu.edu.cn/~fwu/teaching/res/android-ndk-r11-linux-x86_64.zip
[2] If your Linux is 64-bits, execute the following command before setting up your AVD
sudo apt-get install libc6:i386 libgcc1:i386 gcc-4.6-base:i386 libstdc++5:i386 libstdc++6:i386
[3] http://developer.android.com/ndk/guides/android_mk.html [4] How to add location to Environment Variables.
Add following sentence in ~/.bashrc(for common user) or /etc/profile(for root user): export PATH=#l absolute path you want#:$PATH
Then type source ~/.bashrc or source /etc/profile in terminal.
DO NOT change any other value in Environment Variables
[5] Some useful adb command:
To check the AVD status:
adb devices
To move a file to the emulator:
adb push #source path ~/hello/hello.o# #target path on device /data/misc#
To use shell on Android:
adb shell
Then you can use shell command like linux. To pull a file out of the emulator:
adb pull #source path in device# #target path#
More commands about adb:
adb help
[6] kernel: http://www.cs.sjtu.edu.cn/~fwu/teaching/res/android-kernel.tar.gz
[7] Start AVD with customized kernel:
emulator –avd YourAvdName –kernel KernelLocation –show-kernel YourAvdName could be OsPrj
KernelLocation could be ~/kernel/goldfish/arch/arm/boot/zImage -show-kernel makes kernel information shown in your shell.
[8] A fast pass to download necessary resources for this project: URL: http://pan.baidu.com/s/1nuSvYh7
Password:ned2