Date: Tue, 26 Sep 2000 15:24:52 -0500 From: "Yonny Cardenas B." <ycardena@yahoo.com> To: questions@freebsd.org Subject: Add a system call Message-ID: <39D10614.9ECD8635@yahoo.com>
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Hi,
I have been trying to insert a new system call (very simple),
I have used the steps in the bottom without problems,
but I don't understand the behavior of the program:
::::::::::::::
mysyscall.c
::::::::::::::
int mysyscall( int *n ) {
printf("In the kernel!\n");
*n = ( *n + 1000);
return 0;
}
::::::::::::::
myprog.c
::::::::::::::
int mysyscall (int * );
int main (void){
int x = 500;
mysyscall(&x);
printf("x= %i\n",x);
}
The kernel syscall apparently run but it doesn't modify the variable.
$cc -o miprog miprog.c
$ ./miprog
x= 500
In the kernel! <--- is showed in the console.
If I compile with the function (syscall), it works apparently correctly.
$cc -o miprog miprog.c mysyscall.c
$ ./miprog
In the kernel!
x= 1500
Thanks for your help.
Yonny Cardenas B.
--------------------------------------------------------------------------
In Mon, 17 May 1999 Zhihui Zhang <zzhang@cs.binghamton.edu> wrote:
I have used the following steps to add system calls to FreeBSD 3.1
several
times. Suppose you want to add a system call:
int mysys(int a, int b, int c). You can do the following steps:
(1) # cd /usr/src/sys/kern
(2) # vi syscalls.master to add your system call into the file:
172 STD BSD { int mysys(int a, int b, int c); }
(3) # sh makesyscalls.sh syscalls.master
This creates three files: syscall.h, syscall-hide.h, and sysproto.h.
(4) # vi mysys.c
Edit your file to implement your mysys(). You can follow the file
kern/vfs_syscalls.c.
(6) # vi /sys/conf/files to add you file mysys.c into it.
(7) Make a new kernel and install it (see FreeBSD handbook)
The following steps update the libc library:
(8) copy syscall.h, syscall-hide.h, and sysproto.h to /usr/include/sys
(9) # cd /usr/src/lib/libc
(10) # make obj
(11) # make depend
(12) # make all
(13) # make insall
Now you can reboot your machine and write a program that uses your
mysys().
--------------------------------------------------------------------------
+-------------------------------------------------------------------------+
| YONNY CARDENAS B. | Tels: +57 1 3451543, 3451554 |
| | 3451565, 2176251 ext. 16 |
| Opus Ingenieria | Fax : +57 1 3458343 |
| Calle 61 # 5-44 Piso 3 | E-mail: y-carden@uniandes.edu.co |
| Santafe de Bogota D.C.,Colombia | ycardena@yahoo.com |
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