y2038: linux: Provide __time64 implementation

  In the glibc the time function can use vDSO (on power and x86 the
USE_IFUNC_TIME is defined), time syscall or 'default' time() from
./time/time.c (as a fallback).

In this patch the last function (time) has been refactored and moved
to ./sysdeps/unix/sysv/linux/time.c to be Linux specific.

The new __time64 explicit 64 bit function for providing 64 bit value of
seconds after epoch (by internally calling __clock_gettime64) has been
introduced.

Moreover, a 32 bit version - __time has been refactored to internally
use __time64.

The __time is now supposed to be used on systems still supporting 32 bit
time (__TIMESIZE != 64) - hence the necessary check for time_t potential
overflow.

Build tests:
./src/scripts/build-many-glibcs.py glibcs

Run-time tests:
- Run specific tests on ARM/x86 32bit systems (qemu):
https://github.com/lmajewski/meta-y2038 and run tests:
https://github.com/lmajewski/y2038-tests/commits/master

Above tests were performed with Y2038 redirection applied as well as without
to test proper usage of both __time64 and __time.
---
 include/time.h                 |  7 ++++++
 sysdeps/unix/sysv/linux/time.c | 39 +++++++++++++++++++++++++++++++++-
 2 files changed, 45 insertions(+), 1 deletion(-)
  

On 15/10/2020 09:34, Lukasz Majewski wrote:
> In the glibc the time function can use vDSO (on power and x86 the
> USE_IFUNC_TIME is defined), time syscall or 'default' time() from
> ./time/time.c (as a fallback).
> 
> In this patch the last function (time) has been refactored and moved
> to ./sysdeps/unix/sysv/linux/time.c to be Linux specific.
> 
> The new __time64 explicit 64 bit function for providing 64 bit value of
> seconds after epoch (by internally calling __clock_gettime64) has been
> introduced.
> 
> Moreover, a 32 bit version - __time has been refactored to internally
> use __time64.
> 
> The __time is now supposed to be used on systems still supporting 32 bit
> time (__TIMESIZE != 64) - hence the necessary check for time_t potential
> overflow.
> 
> Build tests:
> ./src/scripts/build-many-glibcs.py glibcs
> 
> Run-time tests:
> - Run specific tests on ARM/x86 32bit systems (qemu):
> https://github.com/lmajewski/meta-y2038 and run tests:
> https://github.com/lmajewski/y2038-tests/commits/master
> 
> Above tests were performed with Y2038 redirection applied as well as without
> to test proper usage of both __time64 and __time.

Looks good in general, some comments below.

> ---
>  include/time.h                 |  7 ++++++
>  sysdeps/unix/sysv/linux/time.c | 39 +++++++++++++++++++++++++++++++++-
>  2 files changed, 45 insertions(+), 1 deletion(-)
> 
> diff --git a/include/time.h b/include/time.h
> index edf6cdf829..caf2af5e74 100644
> --- a/include/time.h
> +++ b/include/time.h
> @@ -317,6 +317,13 @@ extern int __timespec_get64 (struct __timespec64 *ts, int base);
>  libc_hidden_proto (__timespec_get64)
>  #endif
>  
> +#if __TIMESIZE == 64
> +# define __time64 __time
> +#else
> +extern __time64_t __time64 (__time64_t *timer);
> +libc_hidden_proto (__time64)
> +#endif
> +
>  /* Use in the clock_* functions.  Size of the field representing the
>     actual clock ID.  */
>  #define CLOCK_IDFIELD_SIZE	3

Ok.

> diff --git a/sysdeps/unix/sysv/linux/time.c b/sysdeps/unix/sysv/linux/time.c
> index 9d8e573c0a..1a9a7c0413 100644
> --- a/sysdeps/unix/sysv/linux/time.c
> +++ b/sysdeps/unix/sysv/linux/time.c
> @@ -47,5 +47,42 @@ time (time_t *t)
>  }
>  # endif /* !SHARED */
>  #else /* USE_IFUNC_TIME  */

You need to handle USE_IFUNC_TIME, which is still used for powerpc32 and
i686.  I don't think optimizing for vDSO access pay for the complexity in
these cases, so disable it with:

 20 #ifdef USE_IFUNC_TIME && __TIMESIZE == 64
 21 # include <time.h>


> -# include <time/time.c>
> +/* Conversion of time function to support 64 bit time on archs
> +   with __WORDSIZE == 32 and __TIMESIZE == 32/64  */

I think this comment is kinda unnecessary, but if would still want
to add it I would put close to '__time' implementation rather than
the '__time64'.

> +# include <time.h>
> +# include <time-clockid.h>
> +# include <errno.h>
> +/* Return the time now, and store it in *TIMER if not NULL.  */

Space after the include.

> +
> +__time64_t
> +__time64 (__time64_t *timer)
> +{
> +  struct __timespec64 ts;
> +  __clock_gettime64 (TIME_CLOCK_GETTIME_CLOCKID, &ts);
> +
> +  if (timer)

No implicit checks, use 'if (timer != NULL)'.

> +    *timer = ts.tv_sec;
> +  return ts.tv_sec;
> +}
> +
> +# if __TIMESIZE != 64
> +libc_hidden_def (__time64)

Ok.

> +
> +time_t
> +__time (time_t *timer)
> +{
> +  __time64_t t = __time64 (NULL);
> +
> +  if (! in_time_t_range (t))
> +    {
> +      __set_errno (EOVERFLOW);
> +      return -1;
> +    }
> +
> +  if (timer)

No implicit checks, use 'if (timer != NULL)'.

> +    *timer = t;
> +  return t;
> +}
> +# endif
> +weak_alias (__time, time)
>  #endif
>
  

Hi Adhemerval,

> On 15/10/2020 09:34, Lukasz Majewski wrote:
> > In the glibc the time function can use vDSO (on power and x86 the
> > USE_IFUNC_TIME is defined), time syscall or 'default' time() from
> > ./time/time.c (as a fallback).
> > 
> > In this patch the last function (time) has been refactored and moved
> > to ./sysdeps/unix/sysv/linux/time.c to be Linux specific.
> > 
> > The new __time64 explicit 64 bit function for providing 64 bit
> > value of seconds after epoch (by internally calling
> > __clock_gettime64) has been introduced.
> > 
> > Moreover, a 32 bit version - __time has been refactored to
> > internally use __time64.
> > 
> > The __time is now supposed to be used on systems still supporting
> > 32 bit time (__TIMESIZE != 64) - hence the necessary check for
> > time_t potential overflow.
> > 
> > Build tests:
> > ./src/scripts/build-many-glibcs.py glibcs
> > 
> > Run-time tests:
> > - Run specific tests on ARM/x86 32bit systems (qemu):
> > https://github.com/lmajewski/meta-y2038 and run tests:
> > https://github.com/lmajewski/y2038-tests/commits/master
> > 
> > Above tests were performed with Y2038 redirection applied as well
> > as without to test proper usage of both __time64 and __time.  
> 
> Looks good in general, some comments below.

I'm going to send v2 of this patch.

> 
> > ---
> >  include/time.h                 |  7 ++++++
> >  sysdeps/unix/sysv/linux/time.c | 39
> > +++++++++++++++++++++++++++++++++- 2 files changed, 45
> > insertions(+), 1 deletion(-)
> > 
> > diff --git a/include/time.h b/include/time.h
> > index edf6cdf829..caf2af5e74 100644
> > --- a/include/time.h
> > +++ b/include/time.h
> > @@ -317,6 +317,13 @@ extern int __timespec_get64 (struct
> > __timespec64 *ts, int base); libc_hidden_proto (__timespec_get64)
> >  #endif
> >  
> > +#if __TIMESIZE == 64
> > +# define __time64 __time
> > +#else
> > +extern __time64_t __time64 (__time64_t *timer);
> > +libc_hidden_proto (__time64)
> > +#endif
> > +
> >  /* Use in the clock_* functions.  Size of the field representing
> > the actual clock ID.  */
> >  #define CLOCK_IDFIELD_SIZE	3  
> 
> Ok.
> 
> > diff --git a/sysdeps/unix/sysv/linux/time.c
> > b/sysdeps/unix/sysv/linux/time.c index 9d8e573c0a..1a9a7c0413 100644
> > --- a/sysdeps/unix/sysv/linux/time.c
> > +++ b/sysdeps/unix/sysv/linux/time.c
> > @@ -47,5 +47,42 @@ time (time_t *t)
> >  }
> >  # endif /* !SHARED */
> >  #else /* USE_IFUNC_TIME  */  
> 
> You need to handle USE_IFUNC_TIME, which is still used for powerpc32
> and i686.  I don't think optimizing for vDSO access pay for the
> complexity in these cases, so disable it with:
> 
>  20 #ifdef USE_IFUNC_TIME && __TIMESIZE == 64
>  21 # include <time.h>
> 

In the gettimeofday() conversion patch it was enough to use 
#ifdef __x86_64__ and #ifdef __powerpc64__ in arch specific time.c so

(SHA1: 7455b700279ec8baccf8dd7b119648f8b3e34eec)

> 
> > -# include <time/time.c>
> > +/* Conversion of time function to support 64 bit time on archs
> > +   with __WORDSIZE == 32 and __TIMESIZE == 32/64  */  
> 
> I think this comment is kinda unnecessary, but if would still want
> to add it I would put close to '__time' implementation rather than
> the '__time64'.

Ok. I will remove it.

> 
> > +# include <time.h>
> > +# include <time-clockid.h>
> > +# include <errno.h>
> > +/* Return the time now, and store it in *TIMER if not NULL.  */  
> 
> Space after the include.

Those #includes are following the 
#else /* USE_IFUNC_TIME  */
and the same indentation is used in other places in this file. I've
just followed it.

> 
> > +
> > +__time64_t
> > +__time64 (__time64_t *timer)
> > +{
> > +  struct __timespec64 ts;
> > +  __clock_gettime64 (TIME_CLOCK_GETTIME_CLOCKID, &ts);
> > +
> > +  if (timer)  
> 
> No implicit checks, use 'if (timer != NULL)'.

Ok.

> 
> > +    *timer = ts.tv_sec;
> > +  return ts.tv_sec;
> > +}
> > +
> > +# if __TIMESIZE != 64
> > +libc_hidden_def (__time64)  
> 
> Ok.
> 
> > +
> > +time_t
> > +__time (time_t *timer)
> > +{
> > +  __time64_t t = __time64 (NULL);
> > +
> > +  if (! in_time_t_range (t))
> > +    {
> > +      __set_errno (EOVERFLOW);
> > +      return -1;
> > +    }
> > +
> > +  if (timer)  
> 
> No implicit checks, use 'if (timer != NULL)'.

Ok.

> 
> > +    *timer = t;
> > +  return t;
> > +}
> > +# endif
> > +weak_alias (__time, time)
> >  #endif
> >   




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