linux-kernel - Re: [PATCH] arm64/vdso: Support mremap() for vDSO

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Message-ID: <20170809101341.j7qvffmkgaxtfapb@armageddon.cambridge.arm.com>
Date:   Wed, 9 Aug 2017 11:13:41 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Dmitry Safonov <dsafonov@...tuozzo.com>
Cc:     linux-kernel@...r.kernel.org, 0x7f454c46@...il.com,
        Will Deacon <will.deacon@....com>,
        Russell King <rmk+kernel@...linux.org.uk>,
        Christopher Covington <cov@...eaurora.org>,
        Cyrill Gorcunov <gorcunov@...nvz.org>,
        linux-arm-kernel@...ts.infradead.org,
        Pavel Emelyanov <xemul@...tuozzo.com>
Subject: Re: [PATCH] arm64/vdso: Support mremap() for vDSO

On Wed, Jul 26, 2017 at 08:07:37PM +0300, Dmitry Safonov wrote:
> vDSO VMA address is saved in mm_context for the purpose of using
> restorer from vDSO page to return to userspace after signal handling.
> 
> In Checkpoint Restore in Userspace (CRIU) project we place vDSO VMA
> on restore back to the place where it was on the dump.
> With the exception for x86 (where there is API to map vDSO with
> arch_prctl()), we move vDSO inherited from CRIU task to restoree
> position by mremap().
> 
> CRIU does support arm64 architecture, but kernel doesn't update
> context.vdso pointer after mremap(). Which results in translation
> fault after signal handling on restored application:
> https://github.com/xemul/criu/issues/288
> 
> Make vDSO code track the VMA address by supplying .mremap() fops
> the same way it's done for x86 and arm32 by:
> commit b059a453b1cf ("x86/vdso: Add mremap hook to vm_special_mapping")
> commit 280e87e98c09 ("ARM: 8683/1: ARM32: Support mremap() for sigpage/vDSO").
> 
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will.deacon@....com>
> Cc: Russell King <rmk+kernel@...linux.org.uk>
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: Cyrill Gorcunov <gorcunov@...nvz.org>
> Cc: Pavel Emelyanov <xemul@...tuozzo.com>
> Cc: Christopher Covington <cov@...eaurora.org>
> Signed-off-by: Dmitry Safonov <dsafonov@...tuozzo.com>

Queued for 4.14. Thanks.

-- 
Catalin