Re: [PATCH v5] y2038: Introduce __ASSUME_TIME64_SYSCALLS define

[Lukasz Majewski <lukma at denx dot de>]

Dear All,

> This define indicates if the Linux kernel (5.1+) provides syscalls
> supporting 64 bit versions of struct timespec and timeval.
> 
> For architectures with __WORDSIZE==64 and __TIMESIZE==64 (e.g.
> x86_64, aarch64) this flag is never defined (as those already use 64
> bit versions of struct timespec and timeval).
> 
> The __ASSUME_TIME64_SYSCALLS shall be only defined on systems with
> __WORDSIZE==32.
> 
> For x32 this flag is explicitly undefined as this architecture has
> __WORDSIZE==32 with __TIMESIZE==64. Despite having __WORDSIZE==32 the
> x32 has support for 64 bit time values and hence needs to undefine
> __ASSUME_TIME64_SYSCALLS flag.
> 
> 
> * sysdeps/unix/sysv/linux/kernel-features.h:
> (__ASSUME_TIME64_SYSCALLS): [__LINUX_KERNEL_VERSION >= 0x050100]:
> Define.
> * sysdeps/unix/sysv/linux/x86_64/kernel-features.h
> (__ASSUME_TIME64_SYSCALLS): #undef the __ASSUME_TIME64_SYSCALLS for
> x32 architecture

Gentle ping on this patch. Do you have any more comments?

> 
> ---
> Changes for v5:
> - Rewrite the in-code comment (x32 description more precise)
> - Change patch description (for x32)
> 
> Changes for v4:
> - Exclude this patch from the clock_settime64 patch series
> - Rewrite the in-code comment
> - Change patch description
> 
> Changes for v3:
> - Provide more detailed and verbose description
> - Change name to __ASSUME_TIME64_SYSCALLS
> - Undefine __ASSUME_TIME64_SYSCALLS on x32
> 
> Changes for v2:
> - New patch
> ---
>  sysdeps/unix/sysv/linux/kernel-features.h        | 38
> ++++++++++++++++++++++++
> sysdeps/unix/sysv/linux/x86_64/kernel-features.h |  7 +++++ 2 files
> changed, 45 insertions(+)
> 
> diff --git a/sysdeps/unix/sysv/linux/kernel-features.h
> b/sysdeps/unix/sysv/linux/kernel-features.h index
> bc5c959f58..30e77dd213 100644 ---
> a/sysdeps/unix/sysv/linux/kernel-features.h +++
> b/sysdeps/unix/sysv/linux/kernel-features.h @@ -143,3 +143,41 @@
>     */
>  
>  #define __ASSUME_CLONE_DEFAULT 1
> +
> +#include <bits/wordsize.h>
> +#if __WORDSIZE != 64
> +/* Support for Linux kernel syscalls, which are able to handle 64 bit
> +   time on 32 bit systems (with 'long' and __WORDSIZE equal to 32
> bits). +
> +   Linux kernel, as of version 5.1, provides following set of
> syscalls,
> +   which accept data based on struct timespec and timeval with 64 bit
> +   tv_sec:
> +
> +   clock_gettime64
> +   clock_settime64
> +   clock_adjtime64
> +   clock_getres_time64
> +   clock_nanosleep_time64
> +   timer_gettime64
> +   timer_settime64
> +   timerfd_gettime64
> +   timerfd_settime64
> +   utimensat_time64
> +   pselect6_time64
> +   ppoll_time64
> +   io_pgetevents_time64
> +   recvmmsg_time64
> +   mq_timedsend_time64
> +   mq_timedreceive_time64
> +   semtimedop_time64
> +   rt_sigtimedwait_time64
> +   futex_time64
> +   sched_rr_get_interval_time64
> +
> +   Above syscalls are supposed to replace legacy ones, which handle
> 32
> +   bit version of struct timespec and timeval (i.e. without the '64'
> +   suffix).  */
> +# if __LINUX_KERNEL_VERSION >= 0x050100
> +#  define __ASSUME_TIME64_SYSCALLS 1
> +# endif
> +#endif
> diff --git a/sysdeps/unix/sysv/linux/x86_64/kernel-features.h
> b/sysdeps/unix/sysv/linux/x86_64/kernel-features.h index
> 26280f57ec..179a9ae932 100644 ---
> a/sysdeps/unix/sysv/linux/x86_64/kernel-features.h +++
> b/sysdeps/unix/sysv/linux/x86_64/kernel-features.h @@ -24,3 +24,10 @@
>  #endif
>  
>  #include_next <kernel-features.h>
> +
> +/* For x32, which is a special case in respect to 64 bit time support
> +   (it has __WORDSIZE==32 but __TIMESIZE==64), the
> +   __ASSUME_TIME64_SYSCALLS flag needs to be explicitly undefined.
> */ +#ifdef __ILP32__
> +# undef __ASSUME_TIME64_SYSCALLS
> +#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

Attachment: pgpK9i1BPTdV6.pgp
Description: OpenPGP digital signature