From mboxrd@z Thu Jan 1 00:00:00 1970 From: Catalin Marinas Subject: Re: [PATCH v16 05/16] arm64: untag user pointers passed to memory syscalls Date: Tue, 11 Jun 2019 18:44:48 +0100 Message-ID: <20190611174448.exg2zycfqf4a2vea@mbp> References: <045a94326401693e015bf80c444a4d946a5c68ed.1559580831.git.andreyknvl@google.com> <20190610142824.GB10165@c02tf0j2hf1t.cambridge.arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Andrey Konovalov Cc: Linux ARM , Linux Memory Management List , LKML , amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-rdma@vger.kernel.org, linux-media@vger.kernel.org, kvm@vger.kernel.org, "open list:KERNEL SELFTEST FRAMEWORK" , Vincenzo Frascino , Will Deacon , Mark Rutland , Andrew Morton , Greg Kroah-Hartman , Kees Cook , Yishai Hadas , Felix Kuehling , Alexander Deucher , Christian Koenig List-Id: linux-rdma@vger.kernel.org On Tue, Jun 11, 2019 at 05:35:31PM +0200, Andrey Konovalov wrote: > On Mon, Jun 10, 2019 at 4:28 PM Catalin Marinas wrote: > > On Mon, Jun 03, 2019 at 06:55:07PM +0200, Andrey Konovalov wrote: > > > This patch is a part of a series that extends arm64 kernel ABI to allow to > > > pass tagged user pointers (with the top byte set to something else other > > > than 0x00) as syscall arguments. > > > > > > This patch allows tagged pointers to be passed to the following memory > > > syscalls: get_mempolicy, madvise, mbind, mincore, mlock, mlock2, mprotect, > > > mremap, msync, munlock. > > > > > > Signed-off-by: Andrey Konovalov > > > > I would add in the commit log (and possibly in the code with a comment) > > that mremap() and mmap() do not currently accept tagged hint addresses. > > Architectures may interpret the hint tag as a background colour for the > > corresponding vma. With this: > > I'll change the commit log. Where do you you think I should put this > comment? Before mmap and mremap definitions in mm/? On arm64 we use our own sys_mmap(). I'd say just add a comment on the generic mremap() just before the untagged_addr() along the lines that new_address is not untagged for preserving similar behaviour to mmap(). -- Catalin