Re: [PATCH 4/5] y2038: linux: Provide __timer_gettime64 implementation

[Adhemerval Zanella <adhemerval dot zanella at linaro dot org>]

On 11/11/2019 18:47, Lukasz Majewski wrote:
> This patch provides new __timer_gettime64 explicit 64 bit function for reading
> status of specified timer. To be more precise - the remaining time and interval
> set with timer_settime.
> Moreover, a 32 bit version - __timer_gettime has been refactored to internally
> use __timer_gettime64.
> 
> The __timer_gettime is now supposed to be used on systems still supporting 32
> bit time (__TIMESIZE != 64) - hence the necessary conversion from 64 bit struct
> __timespec64 to struct timespec.
> 
> The new __timer_gettime64 syscall available from Linux 5.1+ has been used, when
> applicable.
> 
> Build tests:
> - The code has been tested on x86_64/x86 (native compilation):
> make PARALLELMFLAGS="-j8" && make check PARALLELMFLAGS="-j8" && \\
> make xcheck PARALLELMFLAGS="-j8"
> 
> - The glibc has been build tested (make PARALLELMFLAGS="-j8") for
> x86 (i386), x86_64-x32, and armv7
> 
> 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

Does it have any additional coverage not present in glibc tests? If yes, would
be possible to enhance glibc tests?

> 
> - Use of cross-test-ssh.sh for ARM (armv7):
>   make PARALLELMFLAGS="-j8" test-wrapper='./cross-test-ssh.sh root@192.168.7.2' xcheck
> 
> Linux kernel, headers and minimal kernel version for glibc build test
> matrix:
> - Linux v5.1 (with timer_gettime64) and glibc build with v5.1 as
>   minimal kernel version (--enable-kernel="5.1.0")
>   The __ASSUME_TIME64_SYSCALLS flag defined.
> 
> - Linux v5.1 and default minimal kernel version
>   The __ASSUME_TIME64_SYSCALLS not defined, but kernel supports timer_gettime64
>   syscall.
> 
> - Linux v4.19 (no timer_gettime64 support) with default minimal kernel version
>   for contemporary glibc (3.2.0)
>   This kernel doesn't support timer_gettime64 syscall, so the fallback to
>   timer_gettime is tested.
> 
> Above tests were performed with Y2038 redirection applied as well as without
> (so the __TIMESIZE != 64 execution path is checked as well).
> 
> No regressions were observed.

LGTM with some changes below.

Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>

> ---
>  include/time.h                          |  7 ++++
>  sysdeps/unix/sysv/linux/timer_gettime.c | 44 ++++++++++++++++++++++---
>  2 files changed, 47 insertions(+), 4 deletions(-)
> 
> diff --git a/include/time.h b/include/time.h
> index 52ee213669..8b9a4b7a60 100644
> --- a/include/time.h
> +++ b/include/time.h
> @@ -179,6 +179,13 @@ extern int __futimens64 (int fd, const struct __timespec64 tsp[2]);
>  libc_hidden_proto (__futimens64);
>  #endif
>  
> +#if __TIMESIZE == 64
> +# define __timer_gettime64 __timer_gettime
> +#else
> +extern int __timer_gettime64 (timer_t timerid, struct __itimerspec64 *value);
> +libc_hidden_proto (__timer_gettime64);
> +#endif
> +
>  /* Compute the `struct tm' representation of T,
>     offset OFFSET seconds east of UTC,
>     and store year, yday, mon, mday, wday, hour, min, sec into *TP.

Ok, it follows current practice.

> diff --git a/sysdeps/unix/sysv/linux/timer_gettime.c b/sysdeps/unix/sysv/linux/timer_gettime.c
> index 8d9bef9196..31bf5ce25b 100644
> --- a/sysdeps/unix/sysv/linux/timer_gettime.c
> +++ b/sysdeps/unix/sysv/linux/timer_gettime.c
> @@ -20,15 +20,51 @@
>  #include <stdlib.h>
>  #include <time.h>
>  #include <sysdep.h>
> +#include <kernel-features.h>
>  #include "kernel-posix-timers.h"
>  
>  int
> -timer_gettime (timer_t timerid, struct itimerspec *value)
> +__timer_gettime64 (timer_t timerid, struct __itimerspec64 *value)
>  {
>    struct timer *kt = (struct timer *) timerid;
>  
> -  /* Delete the kernel timer object.  */
> -  int res = INLINE_SYSCALL (timer_gettime, 2, kt->ktimerid, value);
> +#ifdef __ASSUME_TIME64_SYSCALLS
> +# ifndef __NR_timer_gettime64
> +#  define __NR_timer_gettime64 __NR_timer_gettime
> +# endif
> +  return INLINE_SYSCALL (timer_gettime64, 2, kt->ktimerid, value);

Use INLINE_SYSCALL_CALL.

> +#else
> +# ifdef __NR_timer_gettime64
> +  int ret = INLINE_SYSCALL (timer_gettime64, 2, kt->ktimerid, value);

Ditto.

> +  if (ret == 0 || errno != ENOSYS)
> +    return ret;
> +# endif
> +  struct itimerspec its32;
> +  int retval = INLINE_SYSCALL (timer_gettime, 2, kt->ktimerid, &its32);

Ditto.

> +  if (! retval)

Please use an explicit comparison with == 0.

> +    {
> +      value->it_interval = valid_timespec_to_timespec64 (its32.it_interval);
> +      value->it_value = valid_timespec_to_timespec64 (its32.it_value);
> +    }
>  
> -  return res;
> +  return retval;
> +#endif
>  }
> +

Ok.

> +#if __TIMESIZE != 64
> +int
> +__timer_gettime (timer_t timerid, struct itimerspec *value)
> +{
> +  struct __itimerspec64 its64;
> +  int retval = __timer_gettime64 (timerid, &its64);
> +  if (! retval)

Please use an explicit comparison with == 0.

> +    {
> +      value->it_interval = valid_timespec64_to_timespec (its64.it_interval);
> +      value->it_value = valid_timespec64_to_timespec (its64.it_value);
> +    }
> +
> +  return retval;
> +}
> +#endif
> +weak_alias (__timer_gettime, timer_gettime)
> +libc_hidden_def (timer_gettime)
> 

Ok.