From: Joseph Myers <joseph@codesourcery.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: <libc-alpha@sourceware.org>, Albert ARIBAUD <albert.aribaud@3adev.fr>
Subject: Re: Second draft of the Y2038 design document
Date: Fri, 29 Jan 2016 15:40:00 -0000 [thread overview]
Message-ID: <alpine.DEB.2.10.1601291534150.29026@digraph.polyomino.org.uk> (raw)
In-Reply-To: <12761061.sGnHL6NOhT@wuerfel>
On Fri, 29 Jan 2016, Arnd Bergmann wrote:
> Should the kernel rely on the glibc-specific "_TIME_BITS" for this,
> or do we define some other macro that the kernel can test for?
Note that _TIME_BITS would not be tested directly in most glibc headers;
it would be tested in features.h and used there to define __USE_* macros.
(This is an observation, not an answer to your question.)
> __kernel_time_t, ...) and avoids namespace conflicts. In all the above
> examples, the new structure is identical between 32-bit and 64-bit
> architectures. [background: this lets us have a common syscall
> implementation for 64-bit and new 32-bit interfaces, while the
To reiterate on identical structures: where nanoseconds are involved in
struct timespec or anything else where POSIX requires "long" to be the
type, it's a pain for glibc if the kernel treats them as a 64-bit value
when coming from a 32-bit process, as opposed to a 32-bit value with 32
bits of padding, because then glibc needs to copy user-provided structures
and sign-extend the nanoseconds value before passing it to the kernel.
(But for 64-bit processes, correct error checking requires that the value
be treated as 64-bit.) (This doesn't apply to timeval because that uses
suseconds_t for microseconds. But I'd also suppose that syscalls
involving timeval would generally be considered deprecated and the 64-bit
replacements would be using timespec.)
--
Joseph S. Myers
joseph@codesourcery.com
next prev parent reply other threads:[~2016-01-29 15:40 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-28 19:41 Albert ARIBAUD
2016-01-28 21:13 ` Paul Eggert
2016-01-28 23:21 ` Arnd Bergmann
2016-01-29 0:12 ` Paul Eggert
2016-01-29 8:58 ` Arnd Bergmann
2016-03-20 8:07 ` Albert ARIBAUD
2016-03-21 12:15 ` Albert ARIBAUD
2016-03-21 13:07 ` Arnd Bergmann
2016-03-21 18:19 ` Paul Eggert
2016-03-25 12:24 ` Albert ARIBAUD
2016-01-28 21:14 ` Joseph Myers
2016-01-28 23:30 ` Arnd Bergmann
2016-01-28 23:36 ` Joseph Myers
2016-01-28 23:55 ` Arnd Bergmann
2016-01-29 15:40 ` Joseph Myers [this message]
2016-01-29 16:27 ` Arnd Bergmann
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