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List:       glibc-alpha
Subject:    Re: [PATCH v6 2/3] y2038: linux: Provide __mq_timedsend_time64 implementation
From:       Adhemerval Zanella via Libc-alpha <libc-alpha () sourceware ! org>
Date:       2020-03-31 14:51:15
Message-ID: 87d9e057-3524-1c6e-e26b-66694fe099ce () linaro ! org
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On 31/03/2020 05:35, Lukasz Majewski wrote:
> This patch provides new __mq_timedsend_time64 explicit 64 bit function for
> sending messages with absolute timeout.
> Moreover, a 32 bit version - __mq_timedsend has been refactored to internally
> use __mq_timedsend_time64.
> 
> The __mq_timedsend is now supposed to be used on systems still supporting 32
> bit time (__TIMESIZE != 64) - hence the necessary conversion to 64 bit struct
> __timespec64 from struct timespec.
> 
> The new __mq_timedsend_time64 syscall available from Linux 5.1+ has been used,
> when applicable.
> 
> As this wrapper function is also used internally in the glibc, to e.g. provide
> mq_send implementation, an explicit check for abs_timeout being NULL has been
> added due to conversions between struct timespec and struct __timespec64.
> Before this change the Linux kernel handled this NULL pointer.
> 
> 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
> 
> Linux kernel, headers and minimal kernel version for glibc build test matrix:
> - Linux v5.1 (with mq_timedsend_time64) and glibc built with v5.1 as a
>   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
>   mq_timedsend_time64 syscall.
> 
> - Linux v4.19 (no mq_timedsend_time64 support) with default minimal kernel
>   version for contemporary glibc (3.2.0)
>   This kernel doesn't support mq_timedsend_time64 syscall, so the fallback to
>   mq_timedsend is tested.
> 
> Above tests were performed with Y2038 redirection applied as well as without
> (so the __TIMESIZE != 64 execution path is checked as well).
> 
> Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

Still LGTM, thanks.

As a side note, this might be a candidate for the optimization to avoid
issuing a time64 syscall for every call on non y2038 safe kernels,
as we did for clock_gettime.

> 
> ---
> Changes for v6:
> - Replace implicit check for abs_timeout with an explicit one -
>   abs_timeout != NULL
> - Reformat the text to avoid long syscall line
> 
> Changes for v5:
> - Adjust the code for new struct___timespec64.h location
> 
> Changes for v4:
> - Include <bits/types/struct___timespec64.h> unconditionally, to keep
>   consistency across different ports
> 
> Changes for v3:
> - None
> 
> Changes for v2:
> - Fix indentation for __mq_timedsend
> - #include <bits/types/struct___timespec64.h> instead of <include/time.h>
> ---
>  include/mqueue.h                       |  9 +++++
>  sysdeps/unix/sysv/linux/mq_timedsend.c | 49 ++++++++++++++++++++++++--
>  2 files changed, 55 insertions(+), 3 deletions(-)
> 
> diff --git a/include/mqueue.h b/include/mqueue.h
> index 3c66f1711e..32e6570529 100644
> --- a/include/mqueue.h
> +++ b/include/mqueue.h
> @@ -10,4 +10,13 @@ extern __typeof (mq_timedreceive) __mq_timedreceive __nonnull ((2, 5));
>  hidden_proto (__mq_timedreceive)
>  hidden_proto (mq_setattr)
>  # endif
> +#include <struct___timespec64.h>
> +#if __TIMESIZE == 64
> +# define __mq_timedsend_time64 __mq_timedsend
> +#else
> +extern int __mq_timedsend_time64 (mqd_t mqdes, const char *msg_ptr,
> +                                  size_t msg_len, unsigned int msg_prio,
> +                                  const struct __timespec64 *abs_timeout);
> +librt_hidden_proto (__mq_timedsend_time64)
> +#endif
>  #endif
> diff --git a/sysdeps/unix/sysv/linux/mq_timedsend.c b/sysdeps/unix/sysv/linux/mq_timedsend.c
> index 888ec6744a..f2a43df300 100644
> --- a/sysdeps/unix/sysv/linux/mq_timedsend.c
> +++ b/sysdeps/unix/sysv/linux/mq_timedsend.c
> @@ -22,12 +22,55 @@
>  /* Add message pointed by MSG_PTR to message queue MQDES, stop blocking
>     on full message queue if ABS_TIMEOUT expires.  */
>  int
> -__mq_timedsend (mqd_t mqdes, const char *msg_ptr, size_t msg_len,
> -		unsigned int msg_prio, const struct timespec *abs_timeout)
> +__mq_timedsend_time64 (mqd_t mqdes, const char *msg_ptr, size_t msg_len,
> +                       unsigned int msg_prio,
> +                       const struct __timespec64 *abs_timeout)
>  {
> +#ifdef __ASSUME_TIME64_SYSCALLS
> +# ifndef __NR_mq_timedsend_time64
> +#  define __NR_mq_timedsend_time64 __NR_mq_timedsend
> +# endif
> +  return SYSCALL_CANCEL (mq_timedsend_time64, mqdes, msg_ptr, msg_len,
> +                         msg_prio, abs_timeout);
> +#else
> +  int ret = SYSCALL_CANCEL (mq_timedsend_time64, mqdes, msg_ptr, msg_len,
> +                            msg_prio, abs_timeout);
> +  if (ret == 0 || errno != ENOSYS)
> +    return ret;
> +
> +  struct timespec ts32;
> +  if (abs_timeout != NULL)
> +    {
> +      if (! in_time_t_range (abs_timeout->tv_sec))
> +        {
> +          __set_errno (EOVERFLOW);
> +          return -1;
> +        }
> +
> +      ts32 = valid_timespec64_to_timespec (*abs_timeout);
> +    }
> +
>    return SYSCALL_CANCEL (mq_timedsend, mqdes, msg_ptr, msg_len, msg_prio,
> -			 abs_timeout);
> +                         abs_timeout != NULL ? &ts32 : NULL);
> +#endif
> +}
> +
> +#if __TIMESIZE != 64
> +librt_hidden_def (__mq_timedsend_time64)
> +
> +int
> +__mq_timedsend (mqd_t mqdes, const char *msg_ptr, size_t msg_len,
> +                unsigned int msg_prio, const struct timespec *abs_timeout)
> +{
> +  struct __timespec64 ts64;
> +  if (abs_timeout != NULL)
> +    ts64 = valid_timespec_to_timespec64 (*abs_timeout);
> +
> +  return __mq_timedsend_time64 (mqdes, msg_ptr, msg_len, msg_prio,
> +                                abs_timeout != NULL ? &ts64 : NULL);
>  }
> +#endif
> +
>  hidden_def (__mq_timedsend)
>  weak_alias (__mq_timedsend, mq_timedsend)
>  hidden_weak (mq_timedsend)
> 
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