Hi Iker Pedrosa,

Please look at how to write the Kconfig files. We need to write a new
Kconfig file for our own implementation.

Regards,
Srinivas G.


On Tue, Jul 23, 2013 at 3:15 PM, Iker Pedrosa [off-list ref]wrote:

Hi Srinivas Ganji,

I've already done it. It wasn't very difficult as I have already worked
with makefiles. Have you got any other suggestion of an exercise I can do?

Thanks you very much again

On Tue, 23 Jul 2013 11:11:16 +0530
Srinivas Ganji [off-list ref] wrote:

quoted

Hi Iker Pedrosa,

Have you completed with your own directory implementation? If you see any
issues, please let me know.

Regards,
Srinivas.


On Sat, Jul 20, 2013 at 4:13 PM, Iker Pedrosa <ikerpedrosam@gmail.com
wrote:

quoted

Thank you very much to everybody. I've tried Sudip Mukherjee's approach
and it has worked (the table is in arch/x86/syscalls/syscall_32.tbl).

Now,

quoted

quoted

I'm going to try to create my own directory in kernel source which

contains

quoted

quoted

my system call implementation files as Srinivas Ganji has proposed.

On Fri, 19 Jul 2013 12:15:44 +0530
Srinivas Ganji [off-list ref] wrote:

quoted

Hi Iker Pedrosa,

In old versions of Linux kernels like 2.6.xx, the approach was

different

quoted

quoted

quoted

from Linux version 3.3 on wards.

There are two different approaches to implement own system call. Each
approach involves several steps. The difference between two

approaches

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quoted

is,

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in one approach, we implement our system call in already existing

file of

quoted

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kernel sources. In another approach, we created our own directory in

kernel

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source which contains our system call implementation files. Ans in

this

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quoted

quoted

second approach, we need to modify the Kernel Makefiles and

Configuration

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files to include our newly created directory and its contents. First

let

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us

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implement using the first approach.

The following approach was successfully tested in Linux kernel 3.5.7
version sources for x86 32-bit architecture.

Here are the steps to create our own system call in the existing

kernel

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sources. The paths given below are relative paths from

/usr/src/linux.

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1. Generally, add the function (system call) definition in

kernel/sys.c

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file.

/* this is the implementation of our system call */
asmlinkage long sys_helloworld(void) {
       printk(KERN_EMERG "Hello, world!\n");
return 0;
}

2. Add the function prototype in the header file

include/linux/syscalls.h

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quoted

quoted

asmlinkage long sys_helloworld(void);

3. Create an entry in system call table in the
file arch/x86/syscalls/syscall_32.tbl

350     i386    helloworld             sys_helloworld

Note: In my case already table had 349 offsets, so I added it as 350.

4. If we want to create our own kernel images, then change the

EXTRAVERSION

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in the main Makefile available at /usr/src/linux

EXTRAVERSION = .ownsyscall

5. Then, build the modules from the main directory with the

following.

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make menuconfig  --- Just save and exit.
make modules
make modules_install
make install

6. Now, reboot with our own image.

7. Write a simple C application for calling the our own system call.

#include <stdio.h>

/* sys_helloworld 350 */
int main ()
{
syscall(350); /* 350 is our system calls offset number */
return 0;
}

I hope, you understand it clearly and it helps you. Based on this,

you

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quoted

can

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practice the second approach. It needs of creating our own directory

and

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files (C, Makefile, Kconfig) and modifications required in

architecture

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specific Kconfig.

Regards,
Srinivas.


On Thu, Jul 18, 2013 at 2:34 PM, Iker Pedrosa <

ikerpedrosam at gmail.com

quoted

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quoted

wrote:

quoted

Hi Guys,

I am a newbie to linux kernel and I am trying to do some of the
exercises/examples of the Linux Kernel Development book by Robert

Love. For

quoted

quoted

the moment I'm trying to create a system call (Chapter 5) but I am

unable

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to do the first step which states the following:
"Add an entry to the end of the system call table.This needs to be

done

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quoted

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for each architecture that supports the system call (which, for

most

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calls,

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is all the architectures).The position of the syscall in the table,
starting at zero, is its system call number. For example, the tenth

entry

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in the list is assigned syscall number nine."

My problem is that I am unable to find the file that holds the

table.

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quoted

In

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the book the file that needs to be changed is the entry.S but it no

longers

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exists in v3.9. In an example that I have found on the internet,

which

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is

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done using v3.0, the file to change is syscall_table_32.S. But I've

got the

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same problem, it doesn't exist. So anybody can help me to find the

table? I

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know that I should be using v2.6 of the kernel but I don't know if

that

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version will work with the distribution that I'm using.

The question is also in stackoverflow so if someone wants to answer

there

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I won't have any problem. The link to the page is the following:

http://stackoverflow.com/questions/17652555/where-is-the-system-call-table-in-linux-kernel-v3-9

quoted

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quoted

--
Iker Pedrosa [off-list ref]

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--
Iker Pedrosa [off-list ref]

--
Iker Pedrosa [off-list ref]

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