Operating Systems I
Homework II
Readme
1st October 2012
About
============================
We added a new system call to Android Linux
Kernel. This system call is called ptree and it returns
into the given buffer a depth first pre-order list of
processes running on the system. The return value of the system call
is total actual number of process running.
Code Changed
==============
The main relevant files added are:
include/linux/prinfo.h -> Includes a structure that defines the information about a process that is returned.
This structure is defined as follows:
struct prinfo {
long state; /* current state of process */
pid_t pid; /* process id */
pid_t parent_pid; /* process id of parent */
pid_t first_child_pid; /* pid of youngest child */
pid_t next_sibling_pid; /* pid of older sibling */
long uid; /* user id of process owner */
char comm[64]; /* name of program executed */
};
kernel/ptree.c -> System call implementation
kernel/ptree.h -> Header file
How to Compile Kernel
=====================
The first time you type:
Change directory to the kernel root folder. Then execute:
make ARCH=arm goldfish_armv7_defconfig
make ARCH=arm CROSS_COMPILE=arm-none-linux-gnueabi-
On Subsequent recompiles, it is easier to make a short cut by doing:
alias armmake="make -j2 ARCH=arm CROSS_COMPILE=arm-none-linux-gnueabi-"
Then you can run the re-compile by just doing: "armmake"
How to Compile Test Program
===========================
Change directory into the 'test-program' folder. Then execute:
make
How to Run Test Program
==================
I'm assuming you have Android SDK tools in your Path.
1) Compile Test Program
2) Compile Kernel
3) Start an Android emulator with the modified kernel image by doing:
emulator -avd OS_W41118 -kernel arch\arm\boot\zImage -show-kernel -no-snapshot-load
4) Push the new binary to the Running Emulator:
adb push test-program\ptree_test /data/misc
5) Open a shell into the emulator:
adb shell
6) Execute the test program
/data/misc/ptree_test
NB: If you get an execution error and you're on Windows, then run this command first.
cd /data/misc
chmod 751 *
Then try running the test program again.
Error Handling
=================
We did our best to handle error conditions gracefully in both the kernel code and the test user program.
Testing
=================
We tested our system call by running the test-program on the emulator. An example output of the test
output is given below:
./ptree_test 5
init,1,1,0,29,2,0
ueventd,29,1,1,0,30,0
servicemanager,30,1,1,0,31,1000
vold,31,1,1,0,33,0
netd,33,1,1,0,34,0
You will notice that the ptree_test program takes in an optional parameter that determines how many processes should
be returned. (This is the nr value)
Running ptree_test with no arguments defaults the number to 100. You should an output like this:
# ./ptree_test
./ptree_test
init,1,1,0,29,2,0
ueventd,29,1,1,0,30,0
servicemanager,30,1,1,0,31,1000
vold,31,1,1,0,33,0
netd,33,1,1,0,34,0
debuggerd,34,1,1,0,35,0
rild,35,1,1,0,36,1001
surfaceflinger,36,1,1,0,37,1000
zygote,37,1,1,148,38,0
system_server,148,1,37,0,149,1000
ndroid.systemui,203,1,37,0,207,10022
m.android.phone,233,1,37,0,234,1001
ndroid.launcher,246,1,37,0,248,10009
ndroid.settings,270,1,37,0,273,1000
ndroid.contacts,297,1,37,0,299,10001
d.process.acore,318,1,37,0,320,10001
com.android.mms,353,1,37,0,356,10002
d.process.media,369,1,37,0,371,10010
putmethod.latin,386,1,37,0,389,10000
m.android.email,415,1,37,0,417,10005
ndroid.exchange,432,1,37,0,434,10031
droid.deskclock,451,1,37,0,454,10030
viders.calendar,474,1,37,0,476,10036
ndroid.calendar,504,1,37,0,506,10019
drmserver,38,1,1,0,39,1019
mediaserver,39,1,1,0,40,1013
installd,40,1,1,0,41,0
keystore,41,1,1,0,42,1017
qemud,42,1,1,0,45,0
sh,45,1,1,0,46,2000
adbd,46,1,1,554,49,0
sh,554,1,46,564,0,0
ptree_test,564,0,554,0,0,0
kthreadd,2,1,0,3,0,0
ksoftirqd/0,3,1,2,0,4,0
events/0,4,1,2,0,5,0
khelper,5,1,2,0,6,0
suspend,6,1,2,0,7,0
kblockd/0,7,1,2,0,8,0
cqueue,8,1,2,0,9,0
kseriod,9,1,2,0,10,0
kmmcd,10,1,2,0,11,0
pdflush,11,1,2,0,12,0
pdflush,12,1,2,0,13,0
kswapd0,13,1,2,0,14,0
aio/0,14,1,2,0,24,0
mtdblockd,24,1,2,0,25,0
kstriped,25,1,2,0,26,0
hid_compat,26,1,2,0,27,0
rpciod/0,27,1,2,0,28,0
mmcqd,28,1,2,0,0,0
Total entries: 51
Coding Style
=============
The code style used is consistent with that of the linux kernel coding style.
You can run the checkpatch.pl[1] with the arguments --no-tree -f [FILE_NAME]
to validate that the style was followed.
Example:
./checkpatch.pl --no-tree -f ptree.c
[1] - You can download checkpath script from: https://github.com/mirrors/linux-2.6/blob/master/scripts/checkpatch.pl