Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755406AbbDTP4H (ORCPT ); Mon, 20 Apr 2015 11:56:07 -0400 Received: from foss.arm.com ([217.140.101.70]:44807 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751024AbbDTP4F (ORCPT ); Mon, 20 Apr 2015 11:56:05 -0400 Date: Mon, 20 Apr 2015 16:56:00 +0100 From: Catalin Marinas To: Arnd Bergmann Cc: Andreas Kraschitzer , Benedikt Huber , "Pinski, Andrew" , Andreas Schwab , "linux-kernel@vger.kernel.org" , "agraf@suse.de" , Andrew Pinski , "ksankaran@apm.com" , "philipp.tomsich@theobroma-systems.com" , "linux-arm-kernel@lists.infradead.org" , Christoph Muellner Subject: Re: [PATCH v4 00/24] ILP32 for ARM64 Message-ID: <20150420155600.GF24715@e104818-lin.cambridge.arm.com> References: <025BB233-8D14-457A-B3B2-C6BD6C3B32EF@theobroma-systems.com> <3365190.ZbiKjUlDk2@wuerfel> <20150417144656.GQ819@e104818-lin.cambridge.arm.com> <2522717.YOvNMEL4TJ@wuerfel> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2522717.YOvNMEL4TJ@wuerfel> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3705 Lines: 87 On Fri, Apr 17, 2015 at 05:49:44PM +0200, Arnd Bergmann wrote: > On Friday 17 April 2015 15:46:57 Catalin Marinas wrote: > > On Fri, Apr 17, 2015 at 02:17:32PM +0100, Arnd Bergmann wrote: > > > g) create a new ABI that does things in exactly the way that we > > > would use as the native syscall interface if we had an ilp32 > > > kernel running on aarch64 with the asm-generic/unistd.h. > > > This would mean a 32-bit __kernel_long_t and time_t, but extending > > > time_t in the long run, together with aarch32 and i386. > > > This one is particularly interesting for people that are interested > > > in maximum posix compliance and in having a "nice" ABI, in particular > > > if there is a slight chance that within the next decade we have > > > reason to support building an arch/arm64 kernel itself in > > > aarch64-ilp32 mode. > > > > I don't think there is a much difference between g) and e). The reason > > we re-define many structures in asm/compat.h is because we don't have a > > generic compat_* definition (e.g. compat_timespec, compat_timeval, > > compat_flock, compat_flock64; anyway, I think some of these may not even > > be needed with the canonical set of syscalls). The signal related > > structures need to be handled differently for AArch32 and AArch64-ILP32 > > anyway because of the difference in the register set. > > Interesting observation, I had not guessed this. > > Let's list the differences, this is what I could find: > > | #define FIOQSIZE 0x545E > > probably broken on arm64 already, should be investigated Yes, it seems broken. arm64 uses the generic FIOQSIZE which doesn't match the compat one. > | typedef unsigned short __kernel_mode_t; > | typedef unsigned short __kernel_ipc_pid_t; > > Both of these affect all sysvipc, but very little else > > | typedef unsigned short __kernel_uid_t; > | typedef unsigned short __kernel_gid_t; > > sysvipc, ncpfs, and core dumps (probably fine since they are separate > anyway), Not all ipc functions are affected AFAICT. msgsnd, msgrcv, msgctl look to me like we can just use the compat variants with the generic definitions for the types above (unless I missed something). Similarly for shmat, compat_sys_shmat just does some compat_ptr casting. > | typedef unsigned short __kernel_old_dev_t; /* compat gets this wrong */ > > old-style loopdev ioctl > > | struct stat { ... } /* possibly not needed */ > > - lustre ioctls (needs to be fixed anyway) > - old stat syscalls (won't be used with asm-generic/unistd.h) > > | struct stat64 { ... } > > - lustre ioctls > - new style stat syscalls For stat64 the wrappers don't look complicated, so we could add arm64 ILP32-specific ones. I'm not sure about the ioctls affected, I haven't checked. > So, in essence the difference comes down to the syscalls for stat > and ipc. If we use the aarch32 data types, we can share the > fstatat64, fstat64, semctl, msgsnd, msgrcv, msgctl, shmat, > and shmctl compat system calls between aarch32-compat and > aarch64-ilp32-compat. Otherwise we have to duplicate or extend > them to cover both cases at runtime. That would be rather ugly > but entirely doable. The ioctls are hardly affected, the few > ones that differ once __kernel_long_t matches could easily be > fixed up as you say. I'd prefer a cleaner ABI even if we are to write some specific wrappers. -- Catalin -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/