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[209.85.217.47]) by smtp.gmail.com with ESMTPSA id q193sm11875047vsd.0.2019.02.12.14.39.14 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 12 Feb 2019 14:39:14 -0800 (PST) Received: by mail-vs1-f47.google.com with SMTP id z18so221836vso.7 for ; Tue, 12 Feb 2019 14:39:14 -0800 (PST) X-Received: by 2002:a67:eb4a:: with SMTP id x10mr2523974vso.172.1550011153602; Tue, 12 Feb 2019 14:39:13 -0800 (PST) MIME-Version: 1.0 References: <25bf3c63-c54c-f7ea-bec1-996a2c05d997@gmail.com> <29cd9541-9af2-fc1c-c264-f4cb9c29349a@gmail.com> In-Reply-To: <29cd9541-9af2-fc1c-c264-f4cb9c29349a@gmail.com> From: Kees Cook Date: Tue, 12 Feb 2019 14:39:02 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [RFC PATCH v4 00/12] hardening: statically allocated protected memory To: Igor Stoppa Cc: Igor Stoppa , Ahmed Soliman , linux-integrity , Kernel Hardening , Linux-MM , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Feb 11, 2019 at 11:09 PM Igor Stoppa wrote: > wr_assign() does just that. > > However, reading again your previous mails, I realize that I might have > misinterpreted what you were suggesting. > > If the advice is to have also a default memset_user() which relies on > put_user(), but do not activate the feature by default for every > architecture, I definitely agree that it would be good to have it. > I just didn't think about it before. Yeah, I just mean you could have an arch-agnostic memset_user() implementation. > But I now realize that most likely you were just suggesting to have > full, albeit inefficient default support and then let various archs > review/enhance it. I can certainly do this. Right. > Regarding testing I have a question: how much can/should I lean on qemu? > In most cases the MMU might not need to be fully emulated, so I wonder > how well qemu-based testing can ensure that real life scenarios will work. I think qemu lets you know if it works (kvm is using the real MMU), and baremetal will give you more stable performance numbers. -- Kees Cook