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, I'm going to try to create my own directory in kernel source which contains my system call implementation files as Srinivas Ganji has proposed.
On Fri, 19 Jul 2013 12:15:44 +0530
Srinivas Ganji <srinivasganji.kernel@xxxxxxxxx> wrote:
> Hi Iker Pedrosa,
>
> In old versions of Linux kernels like 2.6.xx, the approach was different
> 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 is,
> in one approach, we implement our system call in already existing file of
> kernel sources. In another approach, we created our own directory in kernel
> source which contains our system call implementation files. Ans in this
> second approach, we need to modify the Kernel Makefiles and Configuration
> files to include our newly created directory and its contents. First let us
> 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
> sources. The paths given below are relative paths from /usr/src/linux.
>
> 1. Generally, add the function (system call) definition in kernel/sys.c
> 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
>
> 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
> in the main Makefile available at /usr/src/linux
>
> EXTRAVERSION = .ownsyscall
>
> 5. Then, build the modules from the main directory with the following.
>
> 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 can
> practice the second approach. It needs of creating our own directory and
> files (C, Makefile, Kconfig) and modifications required in architecture
> specific Kconfig.
>
> Regards,
> Srinivas.
>
>
> On Thu, Jul 18, 2013 at 2:34 PM, Iker Pedrosa <ikerpedrosam@xxxxxxxxx>wrote:
>
> > 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
> > the moment I'm trying to create a system call (Chapter 5) but I am unable
> > 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
> > for each architecture that supports the system call (which, for most calls,
> > 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
> > in the list is assigned syscall number nine."
> >
> > My problem is that I am unable to find the file that holds the table. In
> > the book the file that needs to be changed is the entry.S but it no longers
> > exists in v3.9. In an example that I have found on the internet, which is
> > done using v3.0, the file to change is syscall_table_32.S. But I've got the
> > same problem, it doesn't exist. So anybody can help me to find the table? I
> > know that I should be using v2.6 of the kernel but I don't know if that
> > version will work with the distribution that I'm using.
> >
> > The question is also in stackoverflow so if someone wants to answer there
> > 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
> >
> > --
> > Iker Pedrosa <ikerpedrosam@xxxxxxxxx>
> >
> > _______________________________________________
> > Kernelnewbies mailing list
> > Kernelnewbies@xxxxxxxxxxxxxxxxx
> > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
> >
--
Iker Pedrosa <ikerpedrosam@xxxxxxxxx>
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