[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20150212161354.GT23507@brightrain.aerifal.cx>
Date: Thu, 12 Feb 2015 11:13:54 -0500
From: Rich Felker <dalias@...c.org>
To: Catalin Marinas <catalin.marinas@....com>
Cc: Andy Lutomirski <luto@...capital.net>, "H.J. Lu" <hjl.tools@...il.com>,
GNU C Library <libc-alpha@...rceware.org>,
Andrew Pinski <pinskia@...il.com>, musl@...ts.openwall.com,
LKML <linux-kernel@...r.kernel.org>,
Andrew Pinski <apinski@...ium.com>,
"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCHv3 00/24] ILP32 support in ARM64
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
Powered by blists - more mailing lists
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
