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[46.139.12.213]) by smtp.gmail.com with ESMTPSA id y4sm6204645wrh.20.2019.04.24.03.38.34 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 24 Apr 2019 03:38:35 -0700 (PDT) Date: Wed, 24 Apr 2019 12:38:33 +0200 From: Ingo Molnar To: Andy Lutomirski Cc: Alexey Dobriyan , "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , Borislav Petkov , LKML , X86 ML , Peter Zijlstra , Linus Torvalds , Al Viro Subject: Re: [PATCH] x86_64: uninline TASK_SIZE Message-ID: <20190424103833.GB9642@gmail.com> References: <20190421160600.GA31092@avx2> <20190421182842.GD35603@gmail.com> <8B42CD57-9343-4234-A96D-80337BFFDF0E@zytor.com> <20190421211007.GA30444@avx2> <20190422103449.GA75723@gmail.com> <20190422220948.GB26031@avx2> <20190423111258.GA23410@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Andy Lutomirski wrote: > > Or am I missing some complication? > > Seems like a great idea to me. > > BTW, what the heck is up with get_gate_page()? I'm struggling to > understand what it's even trying to do. If there's an architecture > that allows a user program to mremap() or otherwise position its gate > VMA between TASK_SIZE and TASK_SIZE_MAX, then that code is going to > explode horribly. I believe it was an old attempt from the times when the vsyscall area *didn't* have a vma, at all, and only get_gate_page() kept the mmap allocator from overlapping it with a user vma? Should IMHO be entirely solved by the vma-ification of all things vsyscall and vdso, and we can remove this remnant. > A whole bunch of work in this direction is here: > > https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git/log/?h=x86/fixes > > It's almost entirely untested. Please post it as patches once you are somewhat confident in the outcome and general direction. Thanks, Ingo