Re: Implement new system call in 2.6

[Richard B. Johnson]

On Wed, 25 Feb 2004, Randy.Dunlap wrote:

> On Wed, 25 Feb 2004 11:07:41 +0100 (CET) Kristian Sørensen wrote:
>
> | Hi all!
> |
> | How do I invoke a newly created system call in the 2.6.3 kernel from
> | userspace?
> |
> | The call is added it arch/i386/kernel/entry.S and include/asm/unistd.h
> | and the call is implemented in a security module called Umbrella(*).
> |
> | The kernel compiles and boots nicely.
> |
> | The main problem is now to compile a userspace program that invokes this
> | call. The guide for implementing the systemcall at
> | http://fossil.wpi.edu/docs/howto_add_systemcall.html
> | has been followed, which yields the following userspace program:
> |
> | // test.h
> | #include "/home/snc/linux-2.6.3-umbrella/include/linux/unistd.h"
> | _syscall1(int, umbrella_scr, int, arg1);
> |
> | // test.c
> | #include "test.h"
> | main() {
> |   int test = umbrella_scr(1);
> |   printf ("%i\n", test);
> | }
> |
> | When compiling:
> |
> | gcc -I/home/snc/linux-2.6.3/include test.c
> |
> | /tmp/ccYYs1zB.o(.text+0x20): In function `umbrella_scr':
> | : undefined reference to `errno'
> | collect2: ld returned 1 exit status
> |

#include <errno.h>

Some versions of 'C' define errno as *__errno_location().


Cheers,
Dick Johnson
Penguin : Linux version 2.4.24 on an i686 machine (797.90 BogoMips).
            Note 96.31% of all statistics are fiction.


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