Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753228AbdGXKhl (ORCPT ); Mon, 24 Jul 2017 06:37:41 -0400 Received: from foss.arm.com ([217.140.101.70]:58856 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751900AbdGXKhe (ORCPT ); Mon, 24 Jul 2017 06:37:34 -0400 Date: Mon, 24 Jul 2017 11:37:24 +0100 From: Dave Martin To: Mark Rutland Cc: linux-arm-kernel@lists.infradead.org, linux-arch@vger.kernel.org, arnd@arndb.de, jiong.wang@arm.com, marc.zyngier@arm.com, catalin.marinas@arm.com, yao.qi@arm.com, suzuki.poulose@arm.com, will.deacon@arm.com, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com, kvmarm@lists.cs.columbia.edu, christoffer.dall@linaro.org Subject: Re: [PATCH 06/11] arm64: Don't trap host pointer auth use to EL2 Message-ID: <20170724103648.GA6321@e103592.cambridge.arm.com> References: <1500480092-28480-1-git-send-email-mark.rutland@arm.com> <1500480092-28480-7-git-send-email-mark.rutland@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1500480092-28480-7-git-send-email-mark.rutland@arm.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2746 Lines: 82 On Wed, Jul 19, 2017 at 05:01:27PM +0100, Mark Rutland wrote: > To allow EL0 (and/or EL1) to use pointer authentication functionality, > we must ensure that pointer authentication instructions and accesses to > pointer authentication keys are not trapped to EL2 (where we will not be > able to handle them). > > This patch ensures that HCR_EL2 is configured appropriately when the > kernel is booted at EL2. For non-VHE kernels we set HCR_EL2.{API,APK}, > ensuring that EL1 can access keys and permit EL0 use of instructions. > For VHE kernels, EL2 access is controlled by EL3, and we need not set > anything. > > This does not enable support for KVM guests, since KVM manages HCR_EL2 > itself. > > Signed-off-by: Mark Rutland > Cc: Catalin Marinas > Cc: Christoffer Dall > Cc: Marc Zyngier > Cc: Will Deacon > Cc: kvmarm@lists.cs.columbia.edu > --- > arch/arm64/include/asm/kvm_arm.h | 2 ++ > arch/arm64/kernel/head.S | 19 +++++++++++++++++-- > 2 files changed, 19 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h > index 61d694c..c1267e8 100644 > --- a/arch/arm64/include/asm/kvm_arm.h > +++ b/arch/arm64/include/asm/kvm_arm.h > @@ -23,6 +23,8 @@ > #include > > /* Hyp Configuration Register (HCR) bits */ > +#define HCR_API (UL(1) << 41) > +#define HCR_APK (UL(1) << 40) > #define HCR_E2H (UL(1) << 34) > #define HCR_ID (UL(1) << 33) > #define HCR_CD (UL(1) << 32) > diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S > index 973df7d..8b8e8d7 100644 > --- a/arch/arm64/kernel/head.S > +++ b/arch/arm64/kernel/head.S > @@ -412,10 +412,25 @@ CPU_LE( bic x0, x0, #(1 << 25) ) // Clear the EE bit for EL2 > > /* Hyp configuration. */ > mov x0, #HCR_RW // 64-bit EL1 > - cbz x2, set_hcr > + cbz x2, 1f Can we keep the label name here? It still seems appropriate. > orr x0, x0, #HCR_TGE // Enable Host Extensions > orr x0, x0, #HCR_E2H > -set_hcr: > +1: > +#ifdef CONFIG_ARM64_POINTER_AUTHENTICATION > + /* > + * Disable pointer authentication traps to EL2. The HCR_EL2.{APK,API} > + * bits exist iff at least one authentication mechanism is implemented. > + */ > + mrs x1, id_aa64isar1_el1 > + mov_q x3, ((0xf << ID_AA64ISAR1_GPI_SHIFT) | \ > + (0xf << ID_AA64ISAR1_GPA_SHIFT) | \ > + (0xf << ID_AA64ISAR1_API_SHIFT) | \ > + (0xf << ID_AA64ISAR1_APA_SHIFT)) Redundant outer (), I think -- mov_q protects its argument. > + and x1, x1, x3 > + cbz x1, 1f tst + b.eq? > + orr x0, x0, #(HCR_APK | HCR_API) > +1: > +#endif > msr hcr_el2, x0 > isb Cheers ---Dave