From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f41.google.com (mail-pa0-f41.google.com [209.85.220.41]) by kanga.kvack.org (Postfix) with ESMTP id D73F96B0253 for ; Tue, 22 Sep 2015 16:21:04 -0400 (EDT) Received: by padhy16 with SMTP id hy16so18610296pad.1 for ; Tue, 22 Sep 2015 13:21:04 -0700 (PDT) Received: from blackbird.sr71.net (www.sr71.net. [198.145.64.142]) by mx.google.com with ESMTP id fm3si4970422pbb.185.2015.09.22.13.21.04 for ; Tue, 22 Sep 2015 13:21:04 -0700 (PDT) Subject: Re: [PATCH 10/26] x86, pkeys: notify userspace about protection key faults References: <20150916174903.E112E464@viggo.jf.intel.com> <20150916174906.51062FBC@viggo.jf.intel.com> From: Dave Hansen Message-ID: <5601B82F.6070601@sr71.net> Date: Tue, 22 Sep 2015 13:21:03 -0700 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Thomas Gleixner Cc: x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org On 09/22/2015 01:03 PM, Thomas Gleixner wrote: > On Wed, 16 Sep 2015, Dave Hansen wrote: >> >> +static inline u16 vma_pkey(struct vm_area_struct *vma) >> +{ >> + u16 pkey = 0; >> +#ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS >> + unsigned long f = vma->vm_flags; >> + pkey |= (!!(f & VM_HIGH_ARCH_0)) << 0; >> + pkey |= (!!(f & VM_HIGH_ARCH_1)) << 1; >> + pkey |= (!!(f & VM_HIGH_ARCH_2)) << 2; >> + pkey |= (!!(f & VM_HIGH_ARCH_3)) << 3; > > Eew. What's wrong with: > > pkey = (vma->vm_flags & VM_PKEY_MASK) >> VM_PKEY_SHIFT; I didn't do that only because we don't have any other need for VM_PKEY_MASK or VM_PKEY_SHIFT. We could do: #define VM_PKEY_MASK (VM_PKEY_BIT0 | VM_PKEY_BIT1 | VM_PKEY_BIT2...) static inline u16 vma_pkey(struct vm_area_struct *vma) { int vm_pkey_shift = __ffs(VM_PKEY_MASK) return (vma->vm_flags & VM_PKEY_MASK) >> vm_pkey_shift; } That's probably the same number of lines of code in the end. The compiler _probably_ ends up doing the same thing either way. >> +static u16 fetch_pkey(unsigned long address, struct task_struct *tsk) > > So here we get a u16 and assign it to si_pkey > >> + if (boot_cpu_has(X86_FEATURE_OSPKE) && si_code == SEGV_PKUERR) >> + info.si_pkey = fetch_pkey(address, tsk); > > which is int. > >> + int _pkey; /* FIXME: protection key value?? > > Inconsistent at least. So I defined all the kernel-internal types as u16 since I *know* the size of the hardware. The user-exposed ones should probably be a bit more generic. I did just realize that this is an int and my proposed syscall is a long. That I definitely need to make consistent. Does anybody care whether it's an int or a long? -- 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