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

Mike Waychison
2011-07-14T20:38:59Z

On Thu, Jul 14, 2011 at 1:37 PM, H. Peter Anvin <hpa@zytor.com> wrote:
> 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.

Are there existing examples of this already in the tree?