From: Rich Felker <dalias@libc.org>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: Andy Lutomirski <luto@amacapital.net>,
"H.J. Lu" <hjl.tools@gmail.com>,
GNU C Library <libc-alpha@sourceware.org>,
Andrew Pinski <pinskia@gmail.com>,
musl@lists.openwall.com, LKML <linux-kernel@vger.kernel.org>,
Andrew Pinski <apinski@cavium.com>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCHv3 00/24] ILP32 support in ARM64
Date: Thu, 12 Feb 2015 11:13:54 -0500 [thread overview]
Message-ID: <20150212161354.GT23507@brightrain.aerifal.cx> (raw)
In-Reply-To: <20150212155023.GA25491@e104818-lin.cambridge.arm.com>
On Thu, Feb 12, 2015 at 03:50:24PM +0000, 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).
At this point POSIX committee is not sufficient. ISO C specifies
timespec now, and as Jens Gustedt mentioned (I don't think his reply
made it to the whole CC list; see the musl list archive here:
http://www.openwall.com/lists/musl/2015/02/11/21 ), it seems unlikely
that one could pose a convincing argument for this requirement to be
changed in the C language.
Rich
next prev parent reply other threads:[~2015-02-12 16:13 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20141002155217.GH32147@e104818-lin.cambridge.arm.com>
2015-02-10 18:13 ` Rich Felker
2015-02-11 17:39 ` Catalin Marinas
2015-02-11 19:05 ` Szabolcs Nagy
2015-02-11 19:22 ` [musl] " H.J. Lu
2015-02-11 19:50 ` arnd
2015-02-11 20:12 ` Rich Felker
2015-02-11 20:47 ` Jens Gustedt
2015-02-11 21:02 ` arnd
2015-02-11 21:09 ` arnd
2015-02-11 21:37 ` [musl] " Rich Felker
2015-02-16 17:20 ` Arnd Bergmann
2015-02-16 17:51 ` [musl] " Rich Felker
2015-02-16 19:38 ` Arnd Bergmann
2015-02-12 8:12 ` Szabolcs Nagy
2015-02-12 17:07 ` Catalin Marinas
2015-02-11 19:21 ` Rich Felker
2015-02-12 18:17 ` Catalin Marinas
2015-02-12 18:59 ` arnd
2015-02-13 13:33 ` Catalin Marinas
2015-02-13 16:30 ` Rich Felker
2015-02-13 17:33 ` Catalin Marinas
2015-02-13 18:37 ` Rich Felker
2015-02-16 14:40 ` Arnd Bergmann
2015-02-16 15:38 ` Rich Felker
2015-02-16 16:54 ` Arnd Bergmann
2015-02-11 18:33 ` H.J. Lu
2015-02-11 19:02 ` Rich Felker
2015-02-11 19:16 ` H.J. Lu
2015-02-11 19:25 ` Rich Felker
2015-02-11 19:34 ` H.J. Lu
2015-02-11 19:47 ` Rich Felker
2015-02-11 19:57 ` H.J. Lu
2015-02-11 20:15 ` Andy Lutomirski
2015-02-12 15:50 ` Catalin Marinas
2015-02-12 16:13 ` Rich Felker [this message]
2015-02-12 16:30 ` H.J. Lu
2015-02-12 17:00 ` Rich Felker
2015-02-11 21:41 ` Joseph Myers
2015-02-11 19:04 ` Josiah Worcester
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