On 03/14/2018 10:14 AM, Ram Pai wrote: > I look at key-0 as 'the key'. It has special status. > (a) It always exist. Do you mean "is always allocated"? > (b) it cannot be freed. This is the one I'm questioning. > (c) it is assigned by default. I agree on this totally. :) > (d) its permissions cannot be modified. Why not? You could pretty easily get a thread going that had its stack covered with another pkey and that was being very careful what it accesses. It could pretty easily set pkey-0's access or write-disable bits. > (e) it bypasses key-permission checks when assigned. I don't think this is necessary. I think the only rule we *need* is: pkey-0 is allocated implicitly at execve() time. You do not need to call pkey_alloc() to allocate it. > An arch need not necessarily map 'the key-0' to its key-0. It could > internally map it to any of its internal key of its choice, transparent > to the application. I don't understand what you are saying here.
