Re: [PATCH] coredump - as root not only if euid switched

[Andrew Morton <akpm@osdl.org>]

Peter Waechtler <pwaechtler@mac.com> wrote:
>
>  >Is it not possible to call sys_unlink() directly from there?  Something like
>  >
>  >long kernel_unlink(const char *name)
>  >{
>  >	mm_segment_t old_fs = get_fs();
>  >	long ret;
>  >
>  >	set_fs(KERNEL_DS);
>  >	ret = sys_unlink(name);
>  >	set_fs(old_fs);
>  >	return ret;
>  >}	
> 
>  And you're asking me? ;)

Well someone has to know ;)

>  While getname() has a check for user/kernelspace - do you really
>  care about "the overhead" for a function call level with 1 argument?
>  Uhm, probably if you even care to write this..

It's very small, but heck, we unlink a lot more often than we dump core. 
Most of us, that is.

>  What is the cost for switching the segments?

Teeny.

>  But I agree that sys_unlink should be the fast call and dumping core
>  is the exception :)
> 
>  would fastcall do_unlink() help? I guess the arg is then passed in a
>  register

I've never been able to measure any size or space benefit for fastcall, and
we do it via compiler options kernel-wide nowadays.

The above will work fine.  You can probably just open-code it at the place
where you're unlinking the file.

(why are you trying to unlink the old file anyway?)