From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [PATCH v2 16/31] arm64: ELF definitions Date: Tue, 21 Aug 2012 20:17:07 +0000 Message-ID: <201208212017.08110.arnd@arndb.de> References: <1344966752-16102-1-git-send-email-catalin.marinas@arm.com> <201208161237.53594.arnd@arndb.de> <20120821160653.GH12708@arm.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: Received: from moutng.kundenserver.de ([212.227.126.187]:65234 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752412Ab2HUURL (ORCPT ); Tue, 21 Aug 2012 16:17:11 -0400 In-Reply-To: <20120821160653.GH12708@arm.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Catalin Marinas Cc: Will Deacon , "linux-arch@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" On Tuesday 21 August 2012, Catalin Marinas wrote: > On Thu, Aug 16, 2012 at 01:37:53PM +0100, Arnd Bergmann wrote: > > On Thursday 16 August 2012, Will Deacon wrote: > > > > This looks wrong: PER_LINUX/PER_LINUX32 decides over the output of the > > > > uname system call, while TIF_32BIT decides over the instruction set > > > > when returning to user space. You definitely should not set the personality > > > > to the value you pass from the elf loader. Instead, just do > > > > > > > > #define SET_PERSONALITY(ex) clear_thread_flag(TIF_32BIT); > > > > #defined COMPAT_SET_PERSONALITY(ex) set_thread_flag(TIF_32BIT); > > > > > > In this case, won't uname be incorrect (aarch64l) for aarch32 tasks (which > > > expect something like armv8l)? > > > > No, the uname output is meant to tell you about the system, not the > > instruction set that you are using (you already know that in compiled > > code). > > OK, so we assumed that compat tasks should get a uname as close as > possible to a 32-bit system, i.e. armv8l, for full compatibility. This > would allow us to run something like 32-bit Debian on an AArch64 kernel > without worrying about any scripts failing. You can still do that, just boot with init="/sbin/setarch armv7 /sbin/init". > But I can see on x86 that it always reports x86_64 even if the task is > x86_32. Not just x86, the same behavior is used on powerpc, s390, mips, sparc and parisc. Not sure about tile though. Arnd From mboxrd@z Thu Jan 1 00:00:00 1970 From: arnd@arndb.de (Arnd Bergmann) Date: Tue, 21 Aug 2012 20:17:07 +0000 Subject: [PATCH v2 16/31] arm64: ELF definitions In-Reply-To: <20120821160653.GH12708@arm.com> References: <1344966752-16102-1-git-send-email-catalin.marinas@arm.com> <201208161237.53594.arnd@arndb.de> <20120821160653.GH12708@arm.com> Message-ID: <201208212017.08110.arnd@arndb.de> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tuesday 21 August 2012, Catalin Marinas wrote: > On Thu, Aug 16, 2012 at 01:37:53PM +0100, Arnd Bergmann wrote: > > On Thursday 16 August 2012, Will Deacon wrote: > > > > This looks wrong: PER_LINUX/PER_LINUX32 decides over the output of the > > > > uname system call, while TIF_32BIT decides over the instruction set > > > > when returning to user space. You definitely should not set the personality > > > > to the value you pass from the elf loader. Instead, just do > > > > > > > > #define SET_PERSONALITY(ex) clear_thread_flag(TIF_32BIT); > > > > #defined COMPAT_SET_PERSONALITY(ex) set_thread_flag(TIF_32BIT); > > > > > > In this case, won't uname be incorrect (aarch64l) for aarch32 tasks (which > > > expect something like armv8l)? > > > > No, the uname output is meant to tell you about the system, not the > > instruction set that you are using (you already know that in compiled > > code). > > OK, so we assumed that compat tasks should get a uname as close as > possible to a 32-bit system, i.e. armv8l, for full compatibility. This > would allow us to run something like 32-bit Debian on an AArch64 kernel > without worrying about any scripts failing. You can still do that, just boot with init="/sbin/setarch armv7 /sbin/init". > But I can see on x86 that it always reports x86_64 even if the task is > x86_32. Not just x86, the same behavior is used on powerpc, s390, mips, sparc and parisc. Not sure about tile though. Arnd