Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756200AbbBLQaO (ORCPT ); Thu, 12 Feb 2015 11:30:14 -0500 Received: from mail-oi0-f46.google.com ([209.85.218.46]:50175 "EHLO mail-oi0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755768AbbBLQaM (ORCPT ); Thu, 12 Feb 2015 11:30:12 -0500 MIME-Version: 1.0 In-Reply-To: <20150212155023.GA25491@e104818-lin.cambridge.arm.com> References: <20141002155217.GH32147@e104818-lin.cambridge.arm.com> <20150210181302.GA23886@brightrain.aerifal.cx> <20150211190252.GB23507@brightrain.aerifal.cx> <20150211192558.GE23507@brightrain.aerifal.cx> <20150211194741.GI23507@brightrain.aerifal.cx> <54DBB87C.5060901@amacapital.net> <20150212155023.GA25491@e104818-lin.cambridge.arm.com> Date: Thu, 12 Feb 2015 08:30:10 -0800 Message-ID: Subject: Re: [PATCHv3 00/24] ILP32 support in ARM64 From: "H.J. Lu" To: Catalin Marinas Cc: Andy Lutomirski , Rich Felker , GNU C Library , Andrew Pinski , musl@lists.openwall.com, LKML , Andrew Pinski , "linux-arm-kernel@lists.infradead.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2674 Lines: 58 On Thu, Feb 12, 2015 at 7:50 AM, Catalin Marinas wrote: > On Wed, Feb 11, 2015 at 12:15:56PM -0800, Andy Lutomirski wrote: >> On 02/11/2015 11:57 AM, H.J. Lu wrote: >> >>>>trivially satisfied if you consider x32 and x86_64 separate >> >>>>compilation environments, but it's not related to the core issue: that >> >>>>the definition of timespec violates core (not obscure) requirements of >> >>>>both POSIX and C11. At the time you were probably unaware of the C11 >> >>>>requirement. Note that it's a LOT harder to effect change in the C >> >>>>standard, so even if the Austin Group would be amenable to changing >> >>>>the requirement for timespec to allow something like nseconds_t, >> >>>>getting WG14 to make this change to work around a Linux/glibc mistake >> >>>>does not sound practical. >> >>> >> >>>That is very unfortunate. I consider it is too late for x32 to change. >> >> >> >>Why? It's hardly an incompatible ABI change, as long as the >> >>kernel/libc fills the upper bits (for old programs that read them >> >>based on the old headers) when structs are read from the kernel to the >> >>application, and ignores the upper bits (potentially set or left >> >>uninitialized by the application) when strings are passed from >> >>userspace to the kernel. Newly built apps using the struct definition >> >>with 32-bit tv_nsec would need new libc to ensure that the high bits >> >>aren't interpreted, but this could be handled by symbol versioning. >> >> >> > >> >We have considered this option. But since kernel wouldn't change >> >tv_nsec/tv_usec handling just for x32, it wasn't selected. >> >> Did anyone *ask* the kernel people (e.g. hpa)? > > It seems so: > > https://lkml.org/lkml/2011/8/31/244 > > Couple of more replies from hpa: > > https://lkml.org/lkml/2011/8/31/261 > https://lkml.org/lkml/2012/2/8/408 > > It looks like hpa was going to talk the POSIX committee but I don't know > what the conclusion was and didn't follow the thread (at the time I > wasn't interested in ARM ILP32). Just for the record, tv_nsec/tv_usec can be changed to long as long as kernel always read them as 32 bits and write them as 64 bits for both LP64 and ILP32 in 64-bit imespec amd timeval. In glibc, they can be changed to long without breaking existing binaries. For x86-32, 64-bit __time_t must be 64-bit aligned. Otherwise, there will be no padding in 64-bit timespec nor timeval. -- H.J. -- 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/