From mboxrd@z Thu Jan 1 00:00:00 1970 From: Catalin Marinas Subject: Re: [Android-virt] [Embeddedxen-devel] [Xen-devel] [ANNOUNCE] Xen port to Cortex-A15 / ARMv7 with virt extensions Date: Thu, 1 Dec 2011 16:57:18 +0000 Message-ID: <20111201165718.GJ27394@arm.com> References: <201112011542.19377.arnd@arndb.de> <20111201160241.GH27394@arm.com> <201112011644.41101.arnd@arndb.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <201112011644.41101.arnd@arndb.de> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Arnd Bergmann Cc: "xen-devel@lists.xensource.com" , "linaro-dev@lists.linaro.org" , Ian Campbell , Pawel Moll , Stefano Stabellini , "linux-kernel@vger.kernel.org" , "virtualization@lists.linux-foundation.org" , "android-virt@lists.cs.columbia.edu" , "kvm@vger.kernel.org" , "embeddedxen-devel@lists.sourceforge.net" , "linux-arm-kernel@lists.infradead.org" List-Id: virtualization@lists.linuxfoundation.org On Thu, Dec 01, 2011 at 04:44:40PM +0000, Arnd Bergmann wrote: > On Thursday 01 December 2011, Catalin Marinas wrote: > > On Thu, Dec 01, 2011 at 03:42:19PM +0000, Arnd Bergmann wrote: > > > On Thursday 01 December 2011, Catalin Marinas wrote: > > > How do you deal with signed integer arguments passed into SVC or HVC from > > > a caller? If I understand the architecture correctly, the upper > > > halves of the argument register end up zero-padded, while the callee > > > expects sign-extension. > > > > If you treat it as an "int" (32-bit) and function prototype defined > > accordingly, then the generated code only accesses it as a W (rather > > than X) register and the top 32-bit part is ignored (no need for > > sign-extension). If it is defined as a "long" in the 32-bit world, then > > it indeed needs explicit conversion given the different sizes for long > > (for example sys_lseek, the second argument is a 'long' and we do > > explicit sign extension in the wrapper). ... > What about unsigned long and pointer? Can we always rely on the upper > half of the register to be zero-filled when we get an exception from 32 > bit into 64 bit state, or do we also have to zero-extend those? They are also fine, no need for zero-extension. -- Catalin