linux-kernel - Re: [PATCH v3 18/26] arm64: Introduce asm/vdso/processor.h

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Date:   Mon, 16 Mar 2020 09:42:32 +0000
From:   Vincenzo Frascino <vincenzo.frascino@....com>
To:     Catalin Marinas <catalin.marinas@....com>
Cc:     linux-arch@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-mips@...r.kernel.org,
        clang-built-linux@...glegroups.com, x86@...nel.org,
        Will Deacon <will.deacon@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Russell King <linux@...linux.org.uk>,
        Paul Burton <paul.burton@...s.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Stephen Boyd <sboyd@...nel.org>,
        Mark Salyzyn <salyzyn@...roid.com>,
        Kees Cook <keescook@...omium.org>,
        Peter Collingbourne <pcc@...gle.com>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Andrei Vagin <avagin@...nvz.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Marc Zyngier <maz@...nel.org>,
        Mark Rutland <Mark.Rutland@....com>,
        Will Deacon <will@...nel.org>
Subject: Re: [PATCH v3 18/26] arm64: Introduce asm/vdso/processor.h

Hi Catalin,

you should not really work on Sunday ;-) Joking, thanks for reviewing my patches.

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 <asm/page-def.h>
>> +
>> +#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).
 * TASK_SIZE is not required by the vdso library hence it is not present in
   these headers.

-- 
Regards,
Vincenzo