RE: questions about sysctl

["Jonathan Khoo" <jonath-k@is.aist-nara.ac.jp>]

Title: Message

Hi guys,

 

I tried a testing on sysctl. In my module, I defined the structure for ctl_table and everything works fine. I can see my variable when I do a sysctl -a.

Next, I tried to call sysctl from a program but I can only get 4 bytes even though in the ctl_handler I tried to return a string with more than 4 bytes.

 

 

in the module,
static int handler(ctl_table *table, int *name, int nlen, void *oldval, size_t *oldlenp, void *newval, size_t newlen, void **context)

{

    char *s = "you called handler";

    copy_to_user(oldval, s, sizeof(s));

    return 0;

}

 

 

program output:

you

 

Does anyone knows where I did wrong?

 

Many Thanks!

Jon.

-----Original Message-----
From: owner-kernelnewbies@nl.linux.org [mailto:owner-kernelnewbies@nl.linux.org] On Behalf Of Jonathan Khoo
Sent: Wednesday, October 31, 2001 1:27 PM
To: kernelnewbies@nl.linux.org
Subject: questions about sysctl

Hi guys,

 

Can anyone please explain to me the significance of proc_handler and ctl_handler in sysctl?

Am I right to say that, if proc_handler is defined, the user will find an entry in /proc/sys for runtime manipulation. ctl_handler on the other hand is called upon, when the user calls sysctl(....) from a program.

Another question I have is that can I used a user-defined structure (other than int) for the data to be used in proc_handler?

 

 

Thanks for any advices!

Jon.