Message-ID: <20030218134315.91052.qmail@web21206.mail.yahoo.com>
Date: Tue, 18 Feb 2003 05:43:15 -0800 (PST)
From: Srinivas Chinta <chintasrinivas_tech@yahoo.com>
Subject: Re: Help !! calling function in module from a user program 
To: Sudharsan Vijayaraghavan <svijayar@cisco.com>
In-Reply-To: <4.3.2.7.2.20030218181634.01fb5428@desh>
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Hi,
One way of doing this is , by hooking up your function
inside the module as a system call.
Here i'm sending two files, module.c and user_space.c.
first do "insmod module.o" and then run
"./user_space".
As i'm also a newbee, i'm not aware of the
disadvantages of this approach.

thanks,
Srinivasu Chinta.

--- Sudharsan Vijayaraghavan <svijayar@cisco.com>
wrote:
> Hi,
> 
> Am a new bee to linux internals.
> I am trying to make a simple program witch will call
> a function from a 
> module. I made a module compiled it and INSMOD-it
> into kernel, that works 
> fine. I would like to call from my user program a
> function defined in my 
> kernel module.
> 
> Please suggest any method thro' which this could be
> accomplished.
> The only way i did it was by running my new module
> as insmod mymodule.o and 
> get my job done.
> 
> Thanks,
> Sudharsan.
> 
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--0-1132932921-1045575795=:90960
Content-Type: text/plain; name="module.c"
Content-Description: module.c
Content-Disposition: inline; filename="module.c"

#define MODULE
#define __KERNEL__
#include <linux/module.h>
#include <linux/kernel.h>

extern void *sys_call_table[];
void * org_func;

static void my_func()
{
        printk("Executing my_func...!");
}
int init_module(void)
{
        printk("init_module ...!");
        org_func = sys_call_table[250];
        sys_call_table[250] = my_func;
        return 0;
}
void cleanup_module()
{
        sys_call_table[250] = org_func;
        printk("cleaning up...!");
}

--0-1132932921-1045575795=:90960
Content-Type: text/plain; name="user_space.c"
Content-Description: user_space.c
Content-Disposition: inline; filename="user_space.c"

#include <stdio.h>
#include <errno.h>
#include <asm/unistd.h>
#define __NR_my_func 250

_syscall0(void, my_func);

main()
{
        my_func();
}

--0-1132932921-1045575795=:90960--
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