Re: Two fixes for 2.4.19-pre5-ac3

[ebiederm@xmission.com (Eric W. Biederman)]

"Philippe Elie" <phil.el@wanadoo.fr> writes:

> From: "Bill Davidsen" <davidsen@tmr.com>
> Sent: Monday, April 08, 2002 4:48 PM
> 

> >   For legitimate use, if any, a compile-time optional system call could be
> > added requiring a capability to use, and programs which are currently
> > doing that (AFS?) can be converted to use another f/s interface. I have
> > seen a few mentions of software which DO use that capability, I'm not sure
> > I've seen one which can be done no other way.
> 
> As stated oprofile needs it, there is no other efficient way to track exec,
> mmap and other sys call needed for profiler. I hope a consensus can
> be reach : explain than unloading module wich patch the sys call table
> are unsafe on SMP, discourage the use of sys call table patch, but do
> not forbid that.

In times past when people were working on the vm86 system call you needed
a modified version of insmod, that could read System.map.

If you are going to be doing strange things I don't see why that shouldn't
still be required.

Though I am wondering if the sane approach for a profiler might not to be
have a kernel conditional compilation directive that simply patches
the syscall path.  The overhead is probably less as well.

Eric