On 10/03/2015 12:27 AM, Ingo Molnar wrote: > - Along similar considerations, also add a sys_pkey_query() system call to query > the mapping of a specific pkey. (returns -EBADF or so if the key is not mapped > at the moment.) This too could be vDSO accelerated in the future. > > I.e. something like: > > unsigned long sys_pkey_alloc (unsigned long flags, unsigned long init_val) > unsigned long sys_pkey_set (int pkey, unsigned long new_val) > unsigned long sys_pkey_get (int pkey) > unsigned long sys_pkey_free (int pkey) The pkey_set() operation is going to get a wee bit interesting with signals. pkey_set() will modify the _current_ context's PKRU which includes the register itself and the kernel XSAVE buffer (if active). But, since the PKRU state is saved/restored with the XSAVE state, we will blow away any state set during the signal. I _think_ the right move here is to either keep a 'shadow' version of PKRU inside the kernel (for each thread) and always update the task's XSAVE PKRU state when returning from a signal handler. Or, _copy_ the signal's PKRU state in to the main process's PKRU state when returning from a signal. -- 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>