Re: [PATCH 1/3] y2038: linux: Provide __futimes64 implementation

[Lukasz Majewski <lukma@denx.de>]

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On Mon, 6 Jul 2020 22:58:27 +0000
Vineet Gupta <Vineet.Gupta1@synopsys.com> wrote:

> Hi Lukasz,
> 
> On 2/17/20 5:17 AM, Lukasz Majewski wrote:
> > This patch provides new __futimes64 explicit 64 bit function for
> > setting file's 64 bit attributes for access and modification time
> > (by specifying file descriptor number).
> > 
> > Internally, the __utimensat64_helper function is used. This patch
> > is necessary for having architectures with __WORDSIZE == 32 Y2038
> > safe.
> > 
> > Moreover, a 32 bit version - __futimes has been refactored to
> > internally use __futimes64.
> > 
> > The __futimes is now supposed to be used on systems still
> > supporting 32 bit time (__TIMESIZE != 64) - hence the necessary
> > conversion of struct timeval to 64 bit struct __timeval64.
> > 
> > The check if struct timevals' usec fields are in the range between
> > 0 and 1000000 has been removed as Linux kernel performs it
> > internally in the implementation of utimensat (the conversion
> > between struct __timeval64 and __timespec64 is not relevant for
> > this particular check).
> > 
> > Last but not least, checks for tvp{64} not being NULL have been
> > preserved from the original code as some legacy user space programs
> > may rely on it.
> > 
> > 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 the proper usage of both __futimes64 and
> > __futimes. ---
> >  include/time.h                    |  3 +++
> >  sysdeps/unix/sysv/linux/futimes.c | 42
> > +++++++++++++++++--------------  
> 
> ARC is 32-bit + TIMESIZE==64 but the new code is not getting built
> (instead generic variant is). How do I override the generic fiel to
> be built instead ?

The futimes.c from sysdeps/unix/sysv/linux/ shall be built. 

The futimes.c is defined in following locations:
y2038-glibc/misc
y2038-glibc/sysdeps/unix/sysv/linux
y2038-glibc/sysdeps/mach/hurd

The first one is a stub. The last one is for hurd.
ARC shall use the middle one as well.

When I'm in doubt (or when for example code is auto generated to wrap a
syscall) I do use
https://github.com/lmajewski/meta-y2038/blob/master/README

with gdb to check which function is called. Maybe it would help you too?

> 
> >  2 files changed, 26 insertions(+), 19 deletions(-)
> > 
> > diff --git a/include/time.h b/include/time.h
> > index b81ecd5e6e..c24066bf3a 100644
> > --- a/include/time.h
> > +++ b/include/time.h
> > @@ -210,8 +210,11 @@ extern int __utimensat64_helper (int fd, const
> > char *file, libc_hidden_proto (__utimensat64_helper);
> >  
> >  #if __TIMESIZE == 64
> > +# define __futimes64 __futimes
> >  # define __futimens64 __futimens
> >  #else
> > +extern int __futimes64 (int fd, const struct __timeval64 tvp64[2]);
> > +libc_hidden_proto (__futimes64);
> >  extern int __futimens64 (int fd, const struct __timespec64 tsp[2]);
> >  libc_hidden_proto (__futimens64);
> >  #endif
> > diff --git a/sysdeps/unix/sysv/linux/futimes.c
> > b/sysdeps/unix/sysv/linux/futimes.c index 4bea864470..21b41e4138
> > 100644 --- a/sysdeps/unix/sysv/linux/futimes.c
> > +++ b/sysdeps/unix/sysv/linux/futimes.c
> > @@ -17,35 +17,39 @@
> >     <https://www.gnu.org/licenses/>.  */
> >  
> >  #include <errno.h>
> > -#include <sysdep.h>
> > -#include <string.h>
> >  #include <time.h>
> > -#include <utime.h>
> > -#include <sys/time.h>
> > -#include <_itoa.h>
> > -#include <fcntl.h>
> > -
> >  
> >  /* Change the access time of the file associated with FD to TVP[0]
> > and
> > -   the modification time of FILE to TVP[1].
> > +   the modification time of FILE to TVP[1].  */
> > +int
> > +__futimes64 (int fd, const struct __timeval64 tvp64[2])
> > +{
> > +  /* The utimensat system call expects timespec not timeval.  */
> > +  struct __timespec64 ts64[2];
> > +  if (tvp64 != NULL)
> > +    {
> > +      ts64[0] = timeval64_to_timespec64 (tvp64[0]);
> > +      ts64[1] = timeval64_to_timespec64 (tvp64[1]);
> > +    }
> > +
> > +  return __utimensat64_helper (fd, NULL, tvp64 ? &ts64[0] : NULL,
> > 0); +}
> > +
> > +#if __TIMESIZE != 64
> > +libc_hidden_def (__futimes64)
> >  
> > -   Starting with 2.6.22 the Linux kernel has the utimensat syscall
> > which
> > -   can be used to implement futimes.  */
> >  int
> >  __futimes (int fd, const struct timeval tvp[2])
> >  {
> > -  /* The utimensat system call expects timespec not timeval.  */
> > -  struct timespec ts[2];
> > +  struct __timeval64 tv64[2];
> > +
> >    if (tvp != NULL)
> >      {
> > -      if (tvp[0].tv_usec < 0 || tvp[0].tv_usec >= 1000000
> > -          || tvp[1].tv_usec < 0 || tvp[1].tv_usec >= 1000000)
> > -	return INLINE_SYSCALL_ERROR_RETURN_VALUE (EINVAL);
> > -
> > -      TIMEVAL_TO_TIMESPEC (&tvp[0], &ts[0]);
> > -      TIMEVAL_TO_TIMESPEC (&tvp[1], &ts[1]);
> > +      tv64[0] = valid_timeval_to_timeval64 (tvp[0]);
> > +      tv64[1] = valid_timeval_to_timeval64 (tvp[1]);
> >      }
> >  
> > -  return INLINE_SYSCALL (utimensat, 4, fd, NULL, tvp ? &ts : NULL,
> > 0);
> > +  return __futimes64 (fd, tvp ? &tv64[0] : NULL);
> >  }
> > +#endif
> >  weak_alias (__futimes, futimes)
> >   
> 




Best regards,

Lukasz Majewski

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