From: Lukasz Majewski <lukma@denx.de>
To: Stepan Golosunov <stepan@golosunov.pp.ru>
Cc: Joseph Myers <joseph@codesourcery.com>,
libc-alpha@sourceware.org, Arnd Bergmann <arnd@arndb.de>,
Paul Eggert <eggert@cs.ucla.edu>
Subject: Re: [PATCH v2 2/7] y2038: Introduce __ASSUME_64BIT_TIME define
Date: Mon, 6 May 2019 16:26:59 +0200 [thread overview]
Message-ID: <20190506162659.6d7e4a59@jawa> (raw)
In-Reply-To: <20190506153844.77cad546@jawa>
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Hi Stepan,
> Hi Stepan,
>
> > Hi Stepan,
> >
> > > 02.05.2019 в 10:51:08 +0200 Lukasz Majewski написал:
> > > > Hi Stepan,
> > > >
> > > > > 30.04.2019 в 11:05:05 +0200 Lukasz Majewski написал:
> > > > > > IMHO, the abstraction would be:
> > > > > >
> > > > > > 1. The __ASSUME_64BIT_TIME is _never_ defined for 64 bit
> > > > > > native systems
> > > > > >
> > > > > > 2. It is defined by default in:
> > > > > > sysdeps/unix/sysv/linux/kernel-features.h for 32 bit systems
> > > > > > (and the actual presence of the syscall is decided upon
> > > > > > definitions of __NR_xxx* (i.e. # ifdef
> > > > > > __NR_clock_settime64).
> > > > >
> > > > > I think that __NR_clock_settime64 should be used
> > > > > unconditionally when __ASSUME_64BIT_TIME is defined.
> > > >
> > > > Could you clarify it a bit?
> > >
> > > I meant something like this:
> > >
> > > int
> > > __clock_settime64 (clockid_t clock_id, const struct __timespec64
> > > *tp) {
> > > #ifdef __ASSUME_64BIT_TIME
> > > return INLINE_SYSCALL_CALL (clock_settime64, clock_id, tp);
> > > #else
> > > …
> > >
> > > But I see now that most of the existing code would just miscompile
> > > in cases where __ASSUME_* is defined while corresponding __NR_* is
> > > not.
> > > > In the code as proposed in:
> > > > https://patchwork.ozlabs.org/patch/1092583/
> > > >
> > > > The call to clock_settime64 is protected with # ifdef
> > > > __NR_clock_settime64 - otherwise we do a fallback to (32 bit)
> > > > clock_settime.
> > > >
> > > > Moreover, the # ifdef __ASSUME_64BIT_TIME provides a fallback
> > > > path if kernel version is older than 5.1.
> > >
> > > The fallback would be wrong in cases where __NR_clock_settime is
> > > not defined or is not 32-bit.
> > >
> > > > > > As those syscalls are provided on almost every 32 bit system
> > > > > > now (5.1-rc6):
> > > > > > git grep -n "clock_settime64"
> > > > > >
> > > > > > gives support for: arm, arm64 (compat mode), m68k,
> > > > > > microblaze, mips, parisc, powerpc, s390, sh, sparc, x86,
> > > > > > xtensa
> > > > > >
> > > > > > So it would be reasonable to just add this __ASSUME
> > > > > > definition code to
> > > > > > sysdeps/unix/sysv/linux/kernel-features.h and #undef it for
> > > > > > architectures not supporting it (i.e. c-sky and
> > > > > > riscv).
> > > > >
> > > > > I believe that the only 32-bit architecture without
> > > > > __NR_clock_settime64 is x32.
> > > >
> > > > Ok, I see.
> > > >
> > > > Please correct me - would it be feasible to just #undef
> > > > __ASSYME_TIME64_SYSCALLS for x32 ?
> > >
> > > You'll need to know whether to use __NR_clock_settime64 or
> > > __NR_clock_settime in cases where __TIMESIZE == 64 and
> > > __WORDSIZE == 32.
>
> Please correct me, but I do have some doubts here.
>
> As x32 now uses 64 bit time (and has TIMESIZE==64) - it uses the
> clock_settime call (with in-kernel broken tv_nsec padding clearing -
> but for this the fix is in its way to upstream).
>
> Why does it need to also support clock_settime64 ?
I was too eager to send the mail.
It is connected with your proposition to use __WORDSIZE for #ifdef on
__ASSUME_TIME64_SYSCALLS.
As x32 has __WORDSIZE=32 (but __TIMESIZE=64), it would fall into
"category" of archs using explicit 64 bit calls (i.e. clock_settime64).
However, for it - those shall be replaced with syscalls used up till now
(i.e. clock_settime).
Am I right here ?
>
> > >
> > > One way would be by defining __ASSUME_TIME64_SYSCALLS
> > > unconditionally on x32 and then defining __NR_clock_settime64 to
> > > __NR_clock_settime when __ASSUME_TIME64_SYSCALLS is defined while
> > > __NR_clock_settime64 isn't.
> > >
> >
> > I see. Thanks for the hint.
> >
> > > > > While newer 32-bit architectures like
> > > > > riscv do not have __NR_clock_settime:
> > > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=d4c08b9776b392e20efc6198ebe1bc8ec1911d9b
> > > >
> > > > Then it shall use clock_settime64 from the outset if support
> > > > added.
> > >
> > > It probably should have __TIMESIZE == 64 though.
> >
> >
> > 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
>
>
>
>
> 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
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:[~2019-05-06 14:27 UTC|newest]
Thread overview: 111+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-14 22:08 [PATCH 0/6] y2038: Linux: Provide __clock_* functions supporting 64 bit time Lukasz Majewski
2019-04-14 22:08 ` [PATCH 1/6] y2038: Introduce internal for glibc struct __timespec64 Lukasz Majewski
2019-04-14 22:08 ` [PATCH 2/6] y2038: Provide conversion helpers for " Lukasz Majewski
2019-04-14 22:08 ` [PATCH 3/6] y2038: linux: Provide __clock_settime64 implementation Lukasz Majewski
2019-04-17 22:08 ` Joseph Myers
2019-04-18 6:46 ` Lukasz Majewski
2019-04-20 0:20 ` Stepan Golosunov
2019-04-20 11:21 ` Lukasz Majewski
2019-04-22 9:07 ` Stepan Golosunov
2019-04-22 21:45 ` Arnd Bergmann
2019-04-23 15:45 ` Lukasz Majewski
2019-04-14 22:08 ` [PATCH 4/6] y2038: linux: Provide __clock_getres64 implementation Lukasz Majewski
2019-04-14 22:08 ` [PATCH 5/6] y2038: linux: Provide __clock_gettime64 implementation Lukasz Majewski
2019-04-14 22:08 ` [PATCH 6/6] y2038: linux: Provide __clock_nanosleep64 implementation Lukasz Majewski
2019-04-17 22:11 ` Joseph Myers
2019-04-18 5:54 ` Lukasz Majewski
2019-04-29 10:46 ` [PATCH v2 0/7] y2038: Linux: Provide __clock_* functions supporting 64 bit time Lukasz Majewski
2019-04-29 10:46 ` [PATCH v2 1/7] y2038: Introduce internal for glibc struct __timespec64 Lukasz Majewski
2019-04-29 10:46 ` [PATCH v2 2/7] y2038: Introduce __ASSUME_64BIT_TIME define Lukasz Majewski
2019-04-29 21:50 ` Joseph Myers
2019-04-30 9:05 ` Lukasz Majewski
2019-04-30 21:47 ` Stepan Golosunov
2019-05-02 8:51 ` Lukasz Majewski
2019-05-02 11:54 ` Stepan Golosunov
2019-05-02 13:55 ` Lukasz Majewski
2019-05-06 13:38 ` Lukasz Majewski
2019-05-06 14:26 ` Lukasz Majewski [this message]
2019-05-06 19:36 ` Stepan Golosunov
2019-05-06 21:14 ` Lukasz Majewski
2019-05-07 20:03 ` Stepan Golosunov
2019-05-07 20:44 ` Joseph Myers
2019-05-08 7:51 ` Lukasz Majewski
2019-05-08 19:48 ` Stepan Golosunov
2019-05-09 16:12 ` Joseph Myers
2019-05-16 4:00 ` Arnd Bergmann
2019-05-16 19:54 ` Stepan Golosunov
2019-05-16 19:59 ` Joseph Myers
2019-05-17 7:23 ` Florian Weimer
2019-05-17 8:34 ` Arnd Bergmann
2019-05-07 15:43 ` Joseph Myers
2019-05-02 15:04 ` Joseph Myers
2019-05-05 14:10 ` Stepan Golosunov
2019-05-05 20:46 ` Lukasz Majewski
2019-05-06 14:56 ` Lukasz Majewski
2019-05-07 15:35 ` Joseph Myers
2019-05-08 10:18 ` Lukasz Majewski
2019-05-09 15:46 ` Joseph Myers
2019-05-15 15:39 ` Lukasz Majewski
2019-05-16 3:57 ` Arnd Bergmann
2019-05-16 6:58 ` Lukasz Majewski
2019-05-31 11:37 ` Stepan Golosunov
2019-06-05 16:35 ` Lukasz Majewski
2019-06-06 6:50 ` Stepan Golosunov
2019-04-29 10:46 ` [PATCH v2 3/7] y2038: Provide conversion helpers for struct __timespec64 Lukasz Majewski
2019-05-02 11:56 ` Stepan Golosunov
2019-05-02 14:17 ` Lukasz Majewski
2019-05-02 15:59 ` Joseph Myers
2019-05-02 16:19 ` Lukasz Majewski
2019-04-29 10:46 ` [PATCH v2 4/7] y2038: linux: Provide __clock_settime64 implementation Lukasz Majewski
2019-04-29 10:46 ` [PATCH v2 5/7] y2038: linux: Provide __clock_getres64 implementation Lukasz Majewski
2019-04-29 10:46 ` [PATCH v2 6/7] y2038: linux: Provide __clock_gettime64 implementation Lukasz Majewski
2019-04-29 10:46 ` [PATCH v2 7/7] y2038: linux: Provide __clock_nanosleep64 implementation Lukasz Majewski
2019-05-07 13:18 ` [PATCH v3 0/5] y2038: Linux: Provide __clock_settime function supporting 64 bit time Lukasz Majewski
2019-05-07 13:18 ` [PATCH v3 1/5] y2038: Introduce __ASSUME_TIME64_SYSCALLS define Lukasz Majewski
2019-05-07 16:04 ` Joseph Myers
2019-05-07 13:18 ` [PATCH v3 2/5] y2038: Introduce internal for glibc struct __timespec64 Lukasz Majewski
2019-05-07 13:30 ` Andreas Schwab
2019-05-07 14:07 ` Lukasz Majewski
2019-05-07 14:13 ` Andreas Schwab
2019-05-08 8:32 ` Lukasz Majewski
2019-05-08 8:38 ` Andreas Schwab
2019-05-08 9:10 ` Lukasz Majewski
2019-05-08 9:12 ` Andreas Schwab
2019-05-08 9:37 ` Lukasz Majewski
2019-05-07 13:18 ` [PATCH v3 3/5] y2038: Provide conversion helpers for " Lukasz Majewski
2019-05-07 13:18 ` [PATCH v3 4/5] y2038: linux: Provide __clock_settime64 implementation Lukasz Majewski
2019-05-07 16:40 ` Joseph Myers
2019-05-07 13:18 ` [PATCH v3 5/5] y2038: Support for Y2038 safe time on 32 bit systems Lukasz Majewski
2019-05-07 16:37 ` Joseph Myers
2019-05-08 10:27 ` Lukasz Majewski
2019-05-07 13:18 ` [PATCH v3 0/5] y2038: Linux: Provide __clock_settime function supporting 64 bit time Lukasz Majewski
2019-05-07 13:18 ` [PATCH v3 1/5] y2038: Introduce __ASSUME_TIME64_SYSCALLS define Lukasz Majewski
2019-05-07 13:18 ` [PATCH v3 2/5] y2038: Introduce internal for glibc struct __timespec64 Lukasz Majewski
2019-05-07 13:18 ` [PATCH v3 3/5] y2038: Provide conversion helpers for " Lukasz Majewski
2019-05-07 13:18 ` [PATCH v3 4/5] y2038: linux: Provide __clock_settime64 implementation Lukasz Majewski
2019-05-07 13:18 ` [PATCH v3 5/5] y2038: Support for Y2038 safe time on 32 bit systems Lukasz Majewski
2019-05-07 13:34 ` Andreas Schwab
2019-05-08 15:56 ` [PATCH] y2038: Introduce __ASSUME_TIME64_SYSCALLS define Lukasz Majewski
2019-05-09 15:58 ` Joseph Myers
2019-05-09 16:18 ` Stepan Golosunov
2019-05-15 14:27 ` [PATCH v5] " Lukasz Majewski
2019-05-21 15:15 ` Lukasz Majewski
2019-05-23 7:34 ` Stepan Golosunov
2019-05-23 9:35 ` Lukasz Majewski
2019-05-25 16:19 ` Lukasz Majewski
2019-05-25 19:45 ` Stepan Golosunov
2019-05-26 12:39 ` Lukasz Majewski
2019-05-28 16:00 ` Lukasz Majewski
2019-05-28 19:53 ` Joseph Myers
2019-05-28 22:46 ` Lukasz Majewski
2019-05-28 22:50 ` Joseph Myers
2019-05-28 19:47 ` Joseph Myers
2019-05-28 22:09 ` Lukasz Majewski
2019-05-28 22:43 ` Joseph Myers
2019-05-23 21:17 ` Joseph Myers
2019-05-20 10:27 ` [PATCH v4 0/3] y2038: Linux: Provide __clock_settime64 function supporting 64 bit time Lukasz Majewski
2019-05-20 10:27 ` [PATCH v4 1/3] y2038: Introduce internal for glibc struct __timespec64 Lukasz Majewski
2019-05-20 10:27 ` [PATCH v4 2/3] y2038: Provide conversion helpers for " Lukasz Majewski
2019-05-20 10:27 ` [PATCH v4 3/3] y2038: linux: Provide __clock_settime64 implementation Lukasz Majewski
2019-05-23 7:08 ` Stepan Golosunov
2019-05-23 9:28 ` Lukasz Majewski
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