Re: [PATCH v4 1/2] y2038: linux: Provide __timerfd_gettime64 implementation

[Lukasz Majewski <lukma@denx.de>]

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Hi Adhemerval,

> On 06/01/2020 09:17, Lukasz Majewski wrote:
> > This patch replaces auto generated wrapper (as described in
> > sysdeps/unix/sysv/linux/syscalls.list) for timerfd_gettime with one
> > which adds extra support for reading 64 bit time values on machines
> > with __TIMESIZE != 64.
> > There is no functional change for architectures already supporting
> > 64 bit time ABI.
> > 
> > This patch is conceptually identical to timer_gettime conversion
> > already done in sysdeps/unix/sysv/linux/timer_gettime.c.
> > Please refer to corresponding commit message for detailed
> > description of introduced functions and the testing procedure.
> > 
> > ---
> > Changes for v4:
> > - Update date from 2019 to 2020
> > 
> > Changes for v3:
> > - Add missing libc_hidden_def()
> > 
> > Changes for v2:
> > - Remove "Contributed by" from the file header
> > - Remove early check for (fd < 0) in __timerfd_gettime64 as the fd
> >   correctness check is already done in Linux kernel
> > - Add single descriptive comment line to provide concise explanation
> >   of the code  
> 
> LGTM when 2.32 opens, thanks.

Ok. Now we do have the "freeze" (fixing period) for 2.31.

> 
> Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
> 
> > ---
> >  include/time.h                            |  3 +
> >  sysdeps/unix/sysv/linux/Makefile          |  3 +-
> >  sysdeps/unix/sysv/linux/syscalls.list     |  1 -
> >  sysdeps/unix/sysv/linux/timerfd_gettime.c | 68
> > +++++++++++++++++++++++ 4 files changed, 73 insertions(+), 2
> > deletions(-) create mode 100644
> > sysdeps/unix/sysv/linux/timerfd_gettime.c
> > 
> > diff --git a/include/time.h b/include/time.h
> > index e5e8246eac..eb5082b4d7 100644
> > --- a/include/time.h
> > +++ b/include/time.h
> > @@ -181,9 +181,12 @@ libc_hidden_proto (__futimens64);
> >  
> >  #if __TIMESIZE == 64
> >  # define __timer_gettime64 __timer_gettime
> > +# define __timerfd_gettime64 __timerfd_gettime
> >  #else
> >  extern int __timer_gettime64 (timer_t timerid, struct
> > __itimerspec64 *value); +extern int __timerfd_gettime64 (int fd,
> > struct __itimerspec64 *value); libc_hidden_proto
> > (__timer_gettime64); +libc_hidden_proto (__timerfd_gettime64);
> >  #endif
> >  
> >  #if __TIMESIZE == 64  
> 
> Ok.
> 
> > diff --git a/sysdeps/unix/sysv/linux/Makefile
> > b/sysdeps/unix/sysv/linux/Makefile index f12b7b1a2d..74923740b9
> > 100644 --- a/sysdeps/unix/sysv/linux/Makefile
> > +++ b/sysdeps/unix/sysv/linux/Makefile
> > @@ -60,7 +60,8 @@ sysdep_routines += adjtimex clone umount umount2
> > readahead \ setfsuid setfsgid epoll_pwait signalfd \
> >  		   eventfd eventfd_read eventfd_write prlimit \
> >  		   personality epoll_wait tee vmsplice splice \
> > -		   open_by_handle_at mlock2 pkey_mprotect pkey_set
> > pkey_get
> > +		   open_by_handle_at mlock2 pkey_mprotect pkey_set
> > pkey_get \
> > +		   timerfd_gettime
> >  
> >  CFLAGS-gethostid.c = -fexceptions
> >  CFLAGS-tee.c = -fexceptions -fasynchronous-unwind-tables  
> 
> Ok.
> 
> > diff --git a/sysdeps/unix/sysv/linux/syscalls.list
> > b/sysdeps/unix/sysv/linux/syscalls.list index
> > 5f1352ad43..adb9055ce2 100644 ---
> > a/sysdeps/unix/sysv/linux/syscalls.list +++
> > b/sysdeps/unix/sysv/linux/syscalls.list @@ -94,7 +94,6 @@
> > mq_setattr	-	mq_getsetattr	i:ipp
> > mq_setattr timerfd_create	EXTRA	timerfd_create
> > i:ii	timerfd_create timerfd_settime	EXTRA
> > timerfd_settime	i:iipp	timerfd_settime
> > -timerfd_gettime	EXTRA	timerfd_gettime
> > i:ip	timerfd_gettime fanotify_init	EXTRA
> > fanotify_init	i:ii	fanotify_init 
> 
> Ok.
> 
> > diff --git a/sysdeps/unix/sysv/linux/timerfd_gettime.c
> > b/sysdeps/unix/sysv/linux/timerfd_gettime.c new file mode 100644
> > index 0000000000..7d09eeb11a
> > --- /dev/null
> > +++ b/sysdeps/unix/sysv/linux/timerfd_gettime.c
> > @@ -0,0 +1,68 @@
> > +/* timerfd_gettime -- get the timer setting referred to by file
> > descriptor.
> > +   Copyright (C) 2020 Free Software Foundation, Inc.
> > +   This file is part of the GNU C Library.
> > +
> > +   The GNU C Library is free software; you can redistribute it
> > and/or
> > +   modify it under the terms of the GNU Lesser General Public
> > License as
> > +   published by the Free Software Foundation; either version 2.1
> > of the
> > +   License, or (at your option) any later version.
> > +
> > +   The GNU C Library is distributed in the hope that it will be
> > useful,
> > +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> > +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > GNU
> > +   Lesser General Public License for more details.
> > +
> > +   You should have received a copy of the GNU Lesser General Public
> > +   License along with the GNU C Library; see the file COPYING.LIB.
> >  If
> > +   not, see <https://www.gnu.org/licenses/>.  */
> > +
> > +#include <errno.h>
> > +#include <stdlib.h>
> > +#include <time.h>
> > +#include <sysdep.h>
> > +#include <kernel-features.h>
> > +
> > +int
> > +__timerfd_gettime64 (int fd, struct __itimerspec64 *value)
> > +{
> > +#ifdef __ASSUME_TIME64_SYSCALLS
> > +# ifndef __NR_timerfd_gettime64
> > +#  define __NR_timerfd_gettime64 __NR_timerfd_gettime
> > +# endif
> > +  return INLINE_SYSCALL_CALL (timerfd_gettime64, fd, value);
> > +#else
> > +# ifdef __NR_timerfd_gettime64
> > +  int ret = INLINE_SYSCALL_CALL (timerfd_gettime64, fd, value);
> > +  if (ret == 0 || errno != ENOSYS)
> > +    return ret;
> > +# endif  
> 
> Ok. 
> 
> As a side note, now that arch-syscall patch is upstream should we
> assume that for !__ASSUME_TIME64_SYSCALLS the __NR_timerfd_gettime64
> should be defined (meaning that Linux supports time64 for all 32-bit
> architectures)?

Only Linux version >= 5.1 supports 64 bit time on archs with __WORDSIZE
= 32. I do guess (but I may be wrong here) that the arch-syscall is
supposed to reflect the exact syscalls provided by kernel headers used
for building (to help with validation of Y2038 patches).

> 
> > +  struct itimerspec its32;
> > +  int retval = INLINE_SYSCALL_CALL (timerfd_gettime, fd, &its32);
> > +  if (retval == 0)
> > +    {
> > +      value->it_interval = valid_timespec_to_timespec64
> > (its32.it_interval);
> > +      value->it_value = valid_timespec_to_timespec64
> > (its32.it_value);
> > +    }
> > +
> > +  return retval;
> > +#endif
> > +}  
> 
> 
> Ok.
> 
> > +
> > +#if __TIMESIZE != 64
> > +libc_hidden_def (__timerfd_gettime64)  
> 
> Ok.
> 
> As a side note, we should fix it on clock_{get,set}time to add the
> missing libc_hidden_def.

The clock_gettime already has libc_hidden_def. The difference is that we
use some compatibility code (after moving clock_gettime from librt to
libc) instead of strong_alias (as it mimics the behavior from auto
generated syscall wrapper).

> 
> > +
> > +int
> > +__timerfd_gettime (int fd, struct itimerspec *value)
> > +{
> > +  struct __itimerspec64 its64;
> > +  int retval = __timerfd_gettime64 (fd, &its64);
> > +  if (retval == 0)
> > +    {
> > +      value->it_interval = valid_timespec64_to_timespec
> > (its64.it_interval);
> > +      value->it_value = valid_timespec64_to_timespec
> > (its64.it_value);
> > +    }
> > +
> > +  return retval;
> > +}
> > +#endif
> > +strong_alias (__timerfd_gettime, timerfd_gettime)
> >   
> 
> Ok.

Thanks for the review.


Best regards,

Lukasz Majewski

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