From mboxrd@z Thu Jan 1 00:00:00 1970 From: Catalin Marinas Subject: Re: [PATCH v3 18/26] arm64: Introduce asm/vdso/processor.h Date: Mon, 16 Mar 2020 10:34:54 +0000 Message-ID: <20200316103437.GD3005@mbp> References: <20200313154345.56760-1-vincenzo.frascino@arm.com> <20200313154345.56760-19-vincenzo.frascino@arm.com> <20200315182950.GB32205@mbp> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from foss.arm.com ([217.140.110.172]:45780 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730582AbgCPKfE (ORCPT ); Mon, 16 Mar 2020 06:35:04 -0400 Content-Disposition: inline In-Reply-To: Sender: linux-arch-owner@vger.kernel.org List-ID: To: Vincenzo Frascino Cc: linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, clang-built-linux@googlegroups.com, x86@kernel.org, Will Deacon , Arnd Bergmann , Russell King , Paul Burton , Thomas Gleixner , Andy Lutomirski , Ingo Molnar , Borislav Petkov , Stephen Boyd , Mark Salyzyn , Kees Cook , Peter Collingbourne , Dmitry Safonov <0x7f454c46@gmail.com>, Andrei Vagin , Nick Desaulniers , Marc Zyngier Mark On Mon, Mar 16, 2020 at 09:42:32AM +0000, Vincenzo Frascino wrote: > you should not really work on Sunday ;-) I was getting bored ;). > On 3/15/20 6:30 PM, Catalin Marinas wrote: > > On Fri, Mar 13, 2020 at 03:43:37PM +0000, Vincenzo Frascino wrote: > >> --- /dev/null > >> +++ b/arch/arm64/include/asm/vdso/processor.h > >> @@ -0,0 +1,31 @@ > >> +/* SPDX-License-Identifier: GPL-2.0-only */ > >> +/* > >> + * Copyright (C) 2020 ARM Ltd. > >> + */ > >> +#ifndef __ASM_VDSO_PROCESSOR_H > >> +#define __ASM_VDSO_PROCESSOR_H > >> + > >> +#ifndef __ASSEMBLY__ > >> + > >> +#include > >> + > >> +#ifdef CONFIG_COMPAT > >> +#if defined(CONFIG_ARM64_64K_PAGES) && defined(CONFIG_KUSER_HELPERS) > >> +/* > >> + * With CONFIG_ARM64_64K_PAGES enabled, the last page is occupied > >> + * by the compat vectors page. > >> + */ > >> +#define TASK_SIZE_32 UL(0x100000000) > >> +#else > >> +#define TASK_SIZE_32 (UL(0x100000000) - PAGE_SIZE) > >> +#endif /* CONFIG_ARM64_64K_PAGES */ > >> +#endif /* CONFIG_COMPAT */ > > > > Just curious, what's TASK_SIZE_32 used for in the vDSO code? You don't > > seem to move TASK_SIZE. > > > > I tried to fine grain the headers as much as I could in order to avoid > unneeded/unwanted inclusions: > * TASK_SIZE_32 is used to verify ABI consistency on vdso32 (please refer to > arch/arm64/kernel/vdso32/vgettimeofday.c). I see. But the test is probably useless. With 4K pages, TASK_SIZE_32 is 1UL << 32, so you can't have a u32 greater than this. So I'd argue that the ABI compatibility here doesn't matter. With 16K or 64K pages, TASK_SIZE_32 is slightly smaller but arm32 never supported it. What's the side-effect of dropping this check altogether? -- Catalin From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from foss.arm.com ([217.140.110.172]:45780 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730582AbgCPKfE (ORCPT ); Mon, 16 Mar 2020 06:35:04 -0400 Date: Mon, 16 Mar 2020 10:34:54 +0000 From: Catalin Marinas Subject: Re: [PATCH v3 18/26] arm64: Introduce asm/vdso/processor.h Message-ID: <20200316103437.GD3005@mbp> References: <20200313154345.56760-1-vincenzo.frascino@arm.com> <20200313154345.56760-19-vincenzo.frascino@arm.com> <20200315182950.GB32205@mbp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-arch-owner@vger.kernel.org List-ID: To: Vincenzo Frascino Cc: linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, clang-built-linux@googlegroups.com, x86@kernel.org, Will Deacon , Arnd Bergmann , Russell King , Paul Burton , Thomas Gleixner , Andy Lutomirski , Ingo Molnar , Borislav Petkov , Stephen Boyd , Mark Salyzyn , Kees Cook , Peter Collingbourne , Dmitry Safonov <0x7f454c46@gmail.com>, Andrei Vagin , Nick Desaulniers , Marc Zyngier , Mark Rutland , Will Deacon Message-ID: <20200316103454.CbdvsVLvHR-OYCcrII9X2NlmLIJQEvD929Svq1YL6pA@z> On Mon, Mar 16, 2020 at 09:42:32AM +0000, Vincenzo Frascino wrote: > you should not really work on Sunday ;-) I was getting bored ;). > On 3/15/20 6:30 PM, Catalin Marinas wrote: > > On Fri, Mar 13, 2020 at 03:43:37PM +0000, Vincenzo Frascino wrote: > >> --- /dev/null > >> +++ b/arch/arm64/include/asm/vdso/processor.h > >> @@ -0,0 +1,31 @@ > >> +/* SPDX-License-Identifier: GPL-2.0-only */ > >> +/* > >> + * Copyright (C) 2020 ARM Ltd. > >> + */ > >> +#ifndef __ASM_VDSO_PROCESSOR_H > >> +#define __ASM_VDSO_PROCESSOR_H > >> + > >> +#ifndef __ASSEMBLY__ > >> + > >> +#include > >> + > >> +#ifdef CONFIG_COMPAT > >> +#if defined(CONFIG_ARM64_64K_PAGES) && defined(CONFIG_KUSER_HELPERS) > >> +/* > >> + * With CONFIG_ARM64_64K_PAGES enabled, the last page is occupied > >> + * by the compat vectors page. > >> + */ > >> +#define TASK_SIZE_32 UL(0x100000000) > >> +#else > >> +#define TASK_SIZE_32 (UL(0x100000000) - PAGE_SIZE) > >> +#endif /* CONFIG_ARM64_64K_PAGES */ > >> +#endif /* CONFIG_COMPAT */ > > > > Just curious, what's TASK_SIZE_32 used for in the vDSO code? You don't > > seem to move TASK_SIZE. > > > > I tried to fine grain the headers as much as I could in order to avoid > unneeded/unwanted inclusions: > * TASK_SIZE_32 is used to verify ABI consistency on vdso32 (please refer to > arch/arm64/kernel/vdso32/vgettimeofday.c). I see. But the test is probably useless. With 4K pages, TASK_SIZE_32 is 1UL << 32, so you can't have a u32 greater than this. So I'd argue that the ABI compatibility here doesn't matter. With 16K or 64K pages, TASK_SIZE_32 is slightly smaller but arm32 never supported it. What's the side-effect of dropping this check altogether? -- Catalin