From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f54.google.com (mail-pa0-f54.google.com [209.85.220.54]) by kanga.kvack.org (Postfix) with ESMTP id 27E8582F64 for ; Fri, 16 Oct 2015 11:12:57 -0400 (EDT) Received: by pacfv9 with SMTP id fv9so25411939pac.3 for ; Fri, 16 Oct 2015 08:12:56 -0700 (PDT) Received: from blackbird.sr71.net ([2001:19d0:2:6:209:6bff:fe9a:902]) by mx.google.com with ESMTP id lp10si30167608pab.101.2015.10.16.08.12.50 for ; Fri, 16 Oct 2015 08:12:50 -0700 (PDT) Subject: Re: [PATCH 26/26] x86, pkeys: Documentation References: <20150916174913.AF5FEA6D@viggo.jf.intel.com> <20150920085554.GA21906@gmail.com> <55FF88BA.6080006@sr71.net> <20150924094956.GA30349@gmail.com> <56044A88.7030203@sr71.net> <20151001111718.GA25333@gmail.com> <20151002062340.GB30051@gmail.com> <560EC3EC.2080803@sr71.net> <20151003072755.GA23524@gmail.com> From: Dave Hansen Message-ID: <562113F0.6060307@sr71.net> Date: Fri, 16 Oct 2015 08:12:48 -0700 MIME-Version: 1.0 In-Reply-To: <20151003072755.GA23524@gmail.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Ingo Molnar Cc: Andy Lutomirski , Kees Cook , "x86@kernel.org" , LKML , Linux-MM , Linus Torvalds , Andrew Morton , Peter Zijlstra , Andy Lutomirski , Borislav Petkov 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@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org