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Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:39410) by pandora.armlinux.org.uk with esmtpsa (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1kMulh-00006I-UJ; Mon, 28 Sep 2020 16:08:46 +0100 Received: from linux by shell.armlinux.org.uk with local (Exim 4.92) (envelope-from ) id 1kMulf-0000Bj-BN; Mon, 28 Sep 2020 16:08:43 +0100 Date: Mon, 28 Sep 2020 16:08:43 +0100 From: Russell King - ARM Linux admin To: Arnd Bergmann Subject: Re: [PATCH 4/9] ARM: syscall: always store thread_info->syscall Message-ID: <20200928150843.GB1551@shell.armlinux.org.uk> References: <20200907153701.2981205-1-arnd@arndb.de> <20200907153701.2981205-5-arnd@arndb.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200928_111155_536522_70A2F7F9 X-CRM114-Status: GOOD ( 17.35 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch , Linus Walleij , "linux-kernel@vger.kernel.org" , Oleg Nesterov , "linux-kernel@vger.kernel.org" , Alexander Viro , Christoph Hellwig , Linux ARM Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Sep 28, 2020 at 02:42:43PM +0200, Arnd Bergmann wrote: > > I need some idea how this numberspace is managed in order to > > understand the code so I can review it, I guess it all makes perfect > > sense but I need some background here. > > I also had never understood this part before, and I'm still not > sure where the 0x900000 actually comes from, though my best > guess is that this was intended as a an OS specific number space, > with '9' being assigned to Linux (similar to the way Itanium and > MIPS do with their respective offsets). By the time EABI got added, > this was apparently no longer considered helpful. It is an OS specific number space, originally designed to allow RISC OS programs to be run under Linux. There was indeed such a project, but that died and the code ripped out. EABI, by using SWI 0 - or more accurately, not reading the SWI opcode, trampled over the ability for RISC OS programs to be run under Linux. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last! _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel