From: Lukasz Majewski <lukma@denx.de>
To: Joseph Myers <joseph@codesourcery.com>
Cc: Florian Weimer <fweimer@redhat.com>,
GNU C Library <libc-alpha@sourceware.org>,
Andreas Schwab <schwab@suse.de>,
Stepan Golosunov <stepan@golosunov.pp.ru>,
Alistair Francis <alistair.francis@wdc.com>
Subject: Re: [PATCH 1/2] y2038: Adjust struct __stat64_t64 to be usable by redirected {f}stat{at} calls
Date: Wed, 14 Oct 2020 10:47:50 +0200 [thread overview]
Message-ID: <20201014104750.230023bc@jawa> (raw)
In-Reply-To: <alpine.DEB.2.21.2010132208570.4206@digraph.polyomino.org.uk>
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Hi Joseph,
> On Tue, 13 Oct 2020, Lukasz Majewski wrote:
>
> > When glibc port with __WORDSIZE==32 and __TIMESIZE!=64 (e.g. armv7)
> > will use redirected calls to {f}stat{at}64_time64 functions, it
> > will accept the struct __stat64_t64 as its argument.
> >
> > To avoid errors related to proper data placement after casting from
> > struct __stat64_t64 to struct stat{64} it is necessary to add some
> > missing padding and update type of {__}st_ino member.
>
> When redirecting to those functions, the definitions of struct stat /
> struct stat64 should automatically change as a result of the
> _TIME_BITS=64 definition so that they match the definitions of the
> __stat64_t64 type - just as _FILE_OFFSET_BITS=64 results in changes
> to the content of struct stat.
Thanks for the explanation. I will adjust exported struct stat{64]
accordingly.
>
> I believe the design is that __stat64_t64 has an
> architecture-independent layout that is never required to match any
> particular kernel layout because translation (typically from statx)
> will always occur in userspace.
>
> Note that struct_stat_time64.h is currently an *uninstalled* header,
> despite the name of the multiple-include guard in the header, and
> despite the testing of feature test macros within the header (which
> only makes sense for installed headers); it's not a bits/ header at
> present.
The only change, that I'm going to do is to mode __ino64_t st_ino
member of struct __stat64_t64
(@ sysdeps/unix/sysv/linux/struct_stat_time64.h) to the end of this
structure (as it is in the exported struct stat{64} placed).
This would allow less #ifndef __USE_TIME_BITS64 in the exported struct
stat{64}.
>
> Maybe there should be some indirection so that the installed version
> of struct_stat_time64.h defines a macro with all the contents of
> __stat64_t64, so that all the many architecture-specific
> bits/struct_stat.h headers can just use that macro to get the right
> contents when _TIME_BITS=64 rather than needing to duplicate the
> structure contents (at least twice per header, for both stat and
> stat64). But I don't think any change to the layout of __stat64_t64
> is indicated, because there should always be explicit conversions
> between different layouts.
>
Best regards,
Lukasz Majewski
--
DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma@denx.de
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next prev parent reply other threads:[~2020-10-14 8:48 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-13 13:16 [PATCH 1/2] y2038: Adjust struct __stat64_t64 to be usable by redirected {f}stat{at} calls Lukasz Majewski
2020-10-13 13:16 ` [PATCH 2/2] y2038: Remove not used __fstatat_time64 define Lukasz Majewski
2020-10-13 13:31 ` Andreas Schwab
2020-10-13 22:17 ` [PATCH 1/2] y2038: Adjust struct __stat64_t64 to be usable by redirected {f}stat{at} calls Joseph Myers
2020-10-14 8:47 ` Lukasz Majewski [this message]
2020-10-14 13:09 ` Joseph Myers
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