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From: Lukasz Majewski <lukma@denx.de>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Florian Weimer <fweimer@redhat.com>,
	Helmut Grohne <helmutg@debian.org>,
	GNU C Library <libc-alpha@sourceware.org>,
	Viresh Kumar <vireshk@kernel.org>,
	Vineet Gupta <Vineet.Gupta1@synopsys.com>,
	Palmer Dabbelt <palmerdabbelt@google.com>,
	Zong Li <zongbox@gmail.com>,
	debian-arm@lists.debian.org,
	Alistair Francis <alistair.francis@wdc.com>,
	Adhemerval Zanella <adhemerval.zanella@linaro.org>,
	"Maciej W. Rozycki" <macro@wdc.com>,
	Alistair Francis <alistair23@gmail.com>,
	arcml <linux-snps-arc@lists.infradead.org>,
	Joseph Myers <joseph@codesourcery.com>
Subject: Re: switching ARC to 64-bit time_t (Re: [RFC v6 07/23] RISC-V: Use 64-bit time_t and off_t for RV32 and RV64)
Date: Thu, 20 Feb 2020 16:42:45 +0100
Message-ID: <20200220164245.035e09b1@jawa> (raw)
In-Reply-To: <CAK8P3a2qLZBAuP-YT2=KZoP+V23TAKvw5W1_2t7rEr2RobLsWw@mail.gmail.com>

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Hi Arnd,

> On Thu, Feb 20, 2020 at 2:15 PM Lukasz Majewski <lukma@denx.de> wrote:
> > > On Thu, Feb 20, 2020 at 10:37 AM Lukasz Majewski <lukma@denx.de>
> > > wrote:  
> > > > > On Thu, Feb 20, 2020 at 12:11 AM Lukasz Majewski
> > > > > <lukma@denx.de> Are there any glibc issues that prevent it
> > > > > from working correctly,  
> > > >
> > > > I think that the glibc wrappers for most important syscalls are
> > > > now converted.
> > > >
> > > > What is missing:
> > > >
> > > > - NTPL (threads)
> > > > - stat  
> > >
> > > Do you mean that code using these will fail to work correctly with
> > > -D_TIME_BITS=64 at the moment, or that the interfaces are there
> > > but they are not y2038 safe?  
> >
> > For ARM32 (branch [2]):
> >
> > - Without -D_TIME_BITS=64 defined during compilation (as we do have
> >   now) the glibc is fully functional, but when you set date after
> >   03:14:08 UTC on 19.01.2038 you will see the date reset (to 1901)
> > in the user space programs (after calling e.g. 'date').  
> 
> I'd actually consider intentionally breaking this for a Debian
> bootstrap, at least initially, so that any application that
> accidentally gets built without -D_TIME_BITS=64 runs into a build or
> link failure.

I do see two approaches here:

1. In glibc:

When -D_TIME_BITS=64 is set - redirections are enabled for syscall
wrappers; for example __clock_settime64 is used instead of
__clock_settime (e.g. sysdeps/unix/sysv/linux/clock_settime).

The latter is guarded by #ifdef __TIMESIZE != 64 so we could change
mechanically that __clock_settime returns -1 and sets errno to -ENOTSUPP


2. In kernel - return -ENOTSUPP when clock_settime syscall instead of
clock_settime64 is invoked.

> 
> > - With -D_TIME_BITS=64 set during compilation - and using branch
> > [2] - syscalls listed in [1] will provide correct date after Y2038
> > 32 bit overflow. Other (i.e. not converted ones) will use overflow
> > date (1901 year). The glibc will also be fully functional up till
> > Y2038 overflow.  
> 
> Ok.
> 
> > > > - In-glibc test coverage when -D_TIME_BITS=64 is used. I do have
> > > >   some basic tests [4], but this may be not enough.  
> > >
> > > This is probably something where debian-rebootstrap could help,
> > > as building and testing more user space packages will excercise
> > > additional code paths in glibc as well.  
> >
> > Yes this _could_ help. Do you have any tutorial/howto similar to one
> > from [4]?  
> 
> Not sure, maybe Helmut has some references.
> 
> > > There is also some work
> > > in Linaro to ensure that LTP tests the low-level syscall
> > > interfaces in both the time32 and time64 variants.  
> >
> > Interesting. Is this work now publicly available?  
> 
> I think this is currently in the planning stage, but once patches
> are available, they would be posted to the ltp mailing list. Viresh
> should have more details on this.
> 
>        Arnd




Best regards,

Lukasz Majewski

--

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Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <cover.1578824547.git.alistair.francis@wdc.com>
     [not found] ` <4e95f95966d8d7c6a8339160dc62d81c1f6a1bfb.1578824547.git.alistair.francis@wdc.com>
2020-02-12  0:14   ` [RFC v6 07/23] RISC-V: Use 64-bit time_t and off_t for RV32 and RV64 Vineet Gupta
2020-02-12  0:14     ` Alistair Francis
2020-02-12  1:30       ` Joseph Myers
2020-02-14 22:39         ` Alistair Francis
2020-02-18 23:05           ` switching ARC to 64-bit time_t (Re: [RFC v6 07/23] RISC-V: Use 64-bit time_t and off_t for RV32 and RV64) Vineet Gupta
2020-02-18 23:13             ` Joseph Myers
2020-02-19 23:09               ` Lukasz Majewski
2020-02-19 23:11             ` Lukasz Majewski
2020-02-20  8:31               ` Arnd Bergmann
2020-02-20  9:37                 ` Lukasz Majewski
2020-02-20 12:37                   ` Arnd Bergmann
2020-02-20 13:14                     ` Lukasz Majewski
2020-02-20 14:44                       ` Arnd Bergmann
2020-02-20 15:42                         ` Lukasz Majewski [this message]
2020-02-20 16:08                           ` Arnd Bergmann
2020-02-20 16:31                             ` Lukasz Majewski
2020-02-24  2:48                         ` Viresh Kumar
2020-02-21 19:56                     ` Alistair Francis
2020-02-22  8:42                   ` Arnd Bergmann
2020-02-24  9:00                     ` Lukasz Majewski
2020-02-24  9:46                       ` Andreas Schwab
2020-02-24 10:14                         ` Lukasz Majewski
2020-02-24 10:23                           ` Andreas Schwab
2020-02-24 10:36                             ` Lukasz Majewski
2020-02-24 10:42                               ` Andreas Schwab
2020-02-24 11:13                                 ` Lukasz Majewski
2020-02-24 12:41                                   ` Lukasz Majewski
2020-02-25  0:03                               ` Joseph Myers
2020-02-25 11:39                                 ` Lukasz Majewski
2020-02-25 14:36                                   ` Joseph Myers
2020-02-26 13:18                                     ` Lukasz Majewski
2020-02-26 14:48                                       ` Joseph Myers
2020-02-26 16:28                                         ` Lukasz Majewski
2020-02-25  9:03                       ` Arnd Bergmann
2020-02-20 16:27                 ` Helmut Grohne
2020-03-26  0:25                   ` ARC rebootstrap prereq (was Re: switching ARC to 64-bit time_t ) Vineet Gupta
2020-03-26  5:54                     ` Helmut Grohne
2020-03-26 11:51                       ` Alexey Brodkin
2020-03-26 12:24                         ` Helmut Grohne
2020-03-26 12:53                           ` Alexey Brodkin
2020-03-26 14:28                             ` Helmut Grohne
2020-03-26 19:04                               ` Lennart Sorensen
2020-02-12  1:42       ` [RFC v6 07/23] RISC-V: Use 64-bit time_t and off_t for RV32 and RV64 Vineet Gupta
2020-02-12 12:58         ` Arnd Bergmann
2020-02-19  0:56   ` Vineet Gupta
2020-02-19  1:03     ` Alistair Francis
2020-02-19  1:31       ` Vineet Gupta
2020-02-19  8:30         ` Andreas Schwab
2020-02-19 18:42           ` Vineet Gupta
2020-02-19 23:18             ` Lukasz Majewski
2020-02-20  0:26               ` Vineet Gupta
2020-02-20  0:46                 ` Joseph Myers
2020-02-20  8:24                   ` Arnd Bergmann
2020-02-20 10:28                     ` Lukasz Majewski
2020-02-20 14:14                     ` Joseph Myers

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