Re: [PATCH 2/2] x86: Allow disabling of sys_iopl, sys_ioperm

H. Peter Anvin
2011-07-14T20:37:37Z

On 07/14/2011 01:34 PM, Mike Waychison wrote:
> In some build environments, it is useful to allow disabling of IO
> accesses to hardware, without having to rely on CAP_SYS_RAWIO (which is
> already overloaded to mean many other things). One way that userland
> has access to IO accesses is via the iopl(2) and ioperm(2) system calls.
>
> Allow disabling of these system calls from ever being available via a
> configuration option, X86_SYS_IOPL. This is implemented by simply
> stubbing out the system calls and having them return ENOSYS when their
> functionality is disabled.
>
> Note that we default this option to 'y', so that existing kernel configs
> will continue to support sys_iopl and sys_ioperm as before.
>

Wouldn't it be more useful for this to be a sysctl? In particular, like
many similar things it probably should be a lockable sysctl (three
states: enabled, disabled, and locked-disabled).

Making it a compile-time option I'm very skeptical to.

-hpa