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[217.140.110.172]) by mx.google.com with ESMTP id j42si9202556eda.80.2019.06.24.06.08.53 for ; Mon, 24 Jun 2019 06:08:54 -0700 (PDT) Received-SPF: pass (google.com: domain of vladimir.murzin@arm.com designates 217.140.110.172 as permitted sender) client-ip=217.140.110.172; Authentication-Results: mx.google.com; spf=pass (google.com: domain of vladimir.murzin@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=vladimir.murzin@arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 4D4FD344; Mon, 24 Jun 2019 06:08:53 -0700 (PDT) Received: from [10.1.32.158] (unknown [10.1.32.158]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id BB6A33F71E; Mon, 24 Jun 2019 06:08:51 -0700 (PDT) Subject: Re: RISC-V nommu support v2 To: Christoph Hellwig Cc: Palmer Dabbelt , Paul Walmsley , Damien Le Moal , linux-riscv@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20190624054311.30256-1-hch@lst.de> <28e3d823-7b78-fa2b-5ca7-79f0c62f9ecb@arm.com> <20190624115428.GA9538@lst.de> From: Vladimir Murzin Message-ID: Date: Mon, 24 Jun 2019 14:08:50 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20190624115428.GA9538@lst.de> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit 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 6/24/19 12:54 PM, Christoph Hellwig wrote: > On Mon, Jun 24, 2019 at 12:47:07PM +0100, Vladimir Murzin wrote: >> Since you are using binfmt_flat which is kind of 32-bit only I was expecting to see >> CONFIG_COMPAT (or something similar to that, like ILP32) enabled, yet I could not >> find it. > > There is no such thing in RISC-V. I don't know of any 64-bit RISC-V > cpu that can actually run 32-bit RISC-V code, although in theory that > is possible. There also is nothing like the x86 x32 or mips n32 mode > available either for now. > > But it turns out that with a few fixes to binfmt_flat it can run 64-bit > binaries just fine. I sent that series out a while ago, and IIRC you > actually commented on it. > True, yet my observation was that elf2flt utility assumes that address space cannot exceed 32-bit (for header and absolute relocations). So, from my limited point of view straightforward way to guarantee that would be to build incoming elf in 32-bit mode (it is why I mentioned COMPAT/ILP32). Also one of your patches expressed somewhat related idea "binfmt_flat isn't the right binary format for huge executables to start with" Since you said there is no support for compat/ilp32, probably I'm missing some toolchain magic? Cheers Vladimir