On Wed, Jul 12, 2017 at 08:08:56AM +1000, Benjamin Herrenschmidt wrote: > On Tue, 2017-07-11 at 14:51 -0700, Ram Pai wrote: > > On Wed, Jul 12, 2017 at 07:29:37AM +1000, Benjamin Herrenschmidt wrote: > > > On Tue, 2017-07-11 at 11:11 -0700, Dave Hansen wrote: > > > > On 07/05/2017 02:21 PM, Ram Pai wrote: > > > > > Currently sys_pkey_create() provides the ability to disable read > > > > > and write permission on the key, at creation. powerpc has the > > > > > hardware support to disable execute on a pkey as well.This patch > > > > > enhances the interface to let disable execute at key creation > > > > > time. x86 does not allow this. Hence the next patch will add > > > > > ability in x86 to return error if PKEY_DISABLE_EXECUTE is > > > > > specified. > > > > > > That leads to the question... How do you tell userspace. > > > > > > (apologies if I missed that in an existing patch in the series) > > > > > > How do we inform userspace of the key capabilities ? There are at least > > > two things userspace may want to know already: > > > > > > - What protection bits are supported for a key > > > > the userspace is the one which allocates the keys and enables/disables the > > protection bits on the key. the kernel is just a facilitator. Now if the > > use space wants to know the current permissions on a given key, it can > > just read the AMR/PKRU register on powerpc/intel respectively. > > You misunderstand. How does userspace knows on a given system whether > execute permission control is supported for keys ? Ah..sorry. did not catch that part. Yes the current patch set does not make that information available. The indirect way of find this out is, to try to allocate a key with execute-disable permission and decide based on the pass/fail status. we can expose that information through a procfs/sysfs interface. RP -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
