From mboxrd@z Thu Jan 1 00:00:00 1970 From: Catalin Marinas Subject: Re: [PATCH 20/25] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it Date: Thu, 12 May 2016 10:17:58 +0100 Message-ID: <20160512091758.GB11226@e104818-lin.cambridge.arm.com> References: <1459894127-17698-1-git-send-email-ynorov@caviumnetworks.com> <5842999.Zgpfq4gkVz@wuerfel> <20160511165900.GM3051@e104818-lin.cambridge.arm.com> <4989778.Fs81NJurjH@wuerfel> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <4989778.Fs81NJurjH@wuerfel> Sender: linux-doc-owner@vger.kernel.org To: Arnd Bergmann Cc: linux-doc@vger.kernel.org, Andrew Pinski , heiko.carstens@de.ibm.com, Yury Norov , Hanjun Guo , joseph@codesourcery.com, linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, "jijun (D)" , Prasun.Kapoor@caviumnetworks.com, schwab@suse.de, agraf@suse.de, pinskia@gmail.com, klimov.linux@gmail.com, broonie@kernel.org, "Zhangjian (Bamvor)" , linux-arm-kernel@lists.infradead.org, Nathan_Lynch@mentor.com, linux-kernel@vger.kernel.org, Andrew Pinski , schwidefsky@de.ibm.com, christoph.muellner@theobroma-systems.com List-Id: linux-arch.vger.kernel.org On Wed, May 11, 2016 at 09:30:07PM +0200, Arnd Bergmann wrote: > On Wednesday 11 May 2016 17:59:01 Catalin Marinas wrote: > > On Wed, May 11, 2016 at 12:55:01PM +0200, Arnd Bergmann wrote: > > > On Wednesday 11 May 2016 11:04:38 Yury Norov wrote: > > > > On Wed, May 11, 2016 at 10:04:16AM +0800, Zhangjian (Bamvor) wrote: > > > > [...] > > > > > > > > > >>Ok, I will test the ltp syscall test. > > > > > >>With this changes, the issue I mentioned should be fixed. But we still > > > > > >>use mmap2 syscall for ILP32 application when we pass the offset instead > > > > > >>of page offset. Is it correct? > > > > > > > > > > > >I don't remember. It's probably not important whether we have the shift > > > > > >in there, as long as it's independent of the actual kernel page size and > > > > > >user space and kernel agree on the calling conventions. > > > > > Well. I am ok with where to shift the pages size because we get the same > > > > > result. I was just thinking if we should get rid of the name of mmap2 in our > > > > > ILP32 porting. Actually, it is mmap but we name it as mmap2. User may confused > > > > > if they do not know the implementations. > > > > > > > > > > > > > This is what generic unistd.h does. If you want to change it, you'd > > > > change each arch that uses generic unistd.h. > > > > > > Generic unistd.h has this: > > > > > > #ifdef __SYSCALL_COMPAT > > > #define __SC_COMP_3264(_nr, _32, _64, _comp) __SYSCALL(_nr, _comp) > > > #else > > > #define __SC_COMP_3264(_nr, _32, _64, _comp) __SC_3264(_nr, _32, _64) > > > #endif > > > > > > #define __NR3264_mmap 222 > > > __SC_3264(__NR3264_mmap, sys_mmap2, sys_mmap) > > > > > > > > > #if __BITS_PER_LONG == 64 && !defined(__SYSCALL_COMPAT) > > > #define __NR_mmap __NR3264_mmap > > > #else > > > #define __NR_mmap2 __NR3264_mmap > > > #endif > > > > > > So by default we get __NR_mmap2 and sys_mmap2 on 32-bit ABIs, but > > > __NR_mmap and sys_mmap on 64-bit ABIs, as it should be. > > > > > > The problem is that arch/arm64/kernel/sys_ilp32.c now overrides > > > this to use __NR_mmap2 with sys_mmap, so we have a mismatch. I think > > > we should either override both the implementation and the number, > > > or neither of them. > > > > I would vote for "neither of them" (so we use __NR_mmap2 and sys_mmap2) > > to keep it close to new 32-bit architectures, even though we would have > > some shifts by 12 in both glibc and kernel. > > I don't think the shifts are a problem, the main downside would be > the limit to 44 bits of file offsets (16TB files), but it's also > unclear if that is a practical problem at all. If it is, we run > into the same problem on all other 32-bit architectures too. I hope people are seriously thinking of moving to an LP64 ABI if they have such large file offset needs. -- Catalin From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from foss.arm.com ([217.140.101.70]:57009 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752606AbcELJSG (ORCPT ); Thu, 12 May 2016 05:18:06 -0400 Date: Thu, 12 May 2016 10:17:58 +0100 From: Catalin Marinas Subject: Re: [PATCH 20/25] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it Message-ID: <20160512091758.GB11226@e104818-lin.cambridge.arm.com> References: <1459894127-17698-1-git-send-email-ynorov@caviumnetworks.com> <5842999.Zgpfq4gkVz@wuerfel> <20160511165900.GM3051@e104818-lin.cambridge.arm.com> <4989778.Fs81NJurjH@wuerfel> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4989778.Fs81NJurjH@wuerfel> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Arnd Bergmann Cc: linux-doc@vger.kernel.org, Andrew Pinski , heiko.carstens@de.ibm.com, Yury Norov , Hanjun Guo , joseph@codesourcery.com, linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, "jijun (D)" , Prasun.Kapoor@caviumnetworks.com, schwab@suse.de, agraf@suse.de, pinskia@gmail.com, klimov.linux@gmail.com, broonie@kernel.org, "Zhangjian (Bamvor)" , linux-arm-kernel@lists.infradead.org, Nathan_Lynch@mentor.com, linux-kernel@vger.kernel.org, Andrew Pinski , schwidefsky@de.ibm.com, christoph.muellner@theobroma-systems.com Message-ID: <20160512091758.FwGrARcjvCWAGICFSCHKlOrYvQaV7TFTXi-StfJXWuk@z> On Wed, May 11, 2016 at 09:30:07PM +0200, Arnd Bergmann wrote: > On Wednesday 11 May 2016 17:59:01 Catalin Marinas wrote: > > On Wed, May 11, 2016 at 12:55:01PM +0200, Arnd Bergmann wrote: > > > On Wednesday 11 May 2016 11:04:38 Yury Norov wrote: > > > > On Wed, May 11, 2016 at 10:04:16AM +0800, Zhangjian (Bamvor) wrote: > > > > [...] > > > > > > > > > >>Ok, I will test the ltp syscall test. > > > > > >>With this changes, the issue I mentioned should be fixed. But we still > > > > > >>use mmap2 syscall for ILP32 application when we pass the offset instead > > > > > >>of page offset. Is it correct? > > > > > > > > > > > >I don't remember. It's probably not important whether we have the shift > > > > > >in there, as long as it's independent of the actual kernel page size and > > > > > >user space and kernel agree on the calling conventions. > > > > > Well. I am ok with where to shift the pages size because we get the same > > > > > result. I was just thinking if we should get rid of the name of mmap2 in our > > > > > ILP32 porting. Actually, it is mmap but we name it as mmap2. User may confused > > > > > if they do not know the implementations. > > > > > > > > > > > > > This is what generic unistd.h does. If you want to change it, you'd > > > > change each arch that uses generic unistd.h. > > > > > > Generic unistd.h has this: > > > > > > #ifdef __SYSCALL_COMPAT > > > #define __SC_COMP_3264(_nr, _32, _64, _comp) __SYSCALL(_nr, _comp) > > > #else > > > #define __SC_COMP_3264(_nr, _32, _64, _comp) __SC_3264(_nr, _32, _64) > > > #endif > > > > > > #define __NR3264_mmap 222 > > > __SC_3264(__NR3264_mmap, sys_mmap2, sys_mmap) > > > > > > > > > #if __BITS_PER_LONG == 64 && !defined(__SYSCALL_COMPAT) > > > #define __NR_mmap __NR3264_mmap > > > #else > > > #define __NR_mmap2 __NR3264_mmap > > > #endif > > > > > > So by default we get __NR_mmap2 and sys_mmap2 on 32-bit ABIs, but > > > __NR_mmap and sys_mmap on 64-bit ABIs, as it should be. > > > > > > The problem is that arch/arm64/kernel/sys_ilp32.c now overrides > > > this to use __NR_mmap2 with sys_mmap, so we have a mismatch. I think > > > we should either override both the implementation and the number, > > > or neither of them. > > > > I would vote for "neither of them" (so we use __NR_mmap2 and sys_mmap2) > > to keep it close to new 32-bit architectures, even though we would have > > some shifts by 12 in both glibc and kernel. > > I don't think the shifts are a problem, the main downside would be > the limit to 44 bits of file offsets (16TB files), but it's also > unclear if that is a practical problem at all. If it is, we run > into the same problem on all other 32-bit architectures too. I hope people are seriously thinking of moving to an LP64 ABI if they have such large file offset needs. -- Catalin