Date: Thu, 12 Feb 2015 15:50:24 +0000 From: Catalin Marinas <catalin.marinas@....com> To: Andy Lutomirski <luto@...capital.net> Cc: "H.J. Lu" <hjl.tools@...il.com>, Rich Felker <dalias@...c.org>, 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 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). -- Catalin
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