[v9] y2038: Introduce the __ASSUME_TIME64_SYSCALLS define
Commit Message
OK, how does this look?
From dc644211be404aea73b6bd218777c6f06472d9f1 Mon Sep 17 00:00:00 2001
From: Lukasz Majewski <lukma@denx.de>
Date: Wed, 28 Aug 2019 14:27:03 -0400
Subject: [PATCH] y2038: Introduce the __ASSUME_TIME64_SYSCALLS define
Add a macro to linux/kernel-features.h, __ASSUME_TIME64_SYSCALLS, to
indicate whether the kernel can be assumed to provide a set of system
calls that process 64-bit time_t.
__ASSUME_TIME64_SYSCALLS does not indicate whether time_t is actually
64 bits (that's __TIMEBITS) and also does not indicate whether the
64-bit time_t system calls have "time64" suffixes on their names.
Code that uses __ASSUME_TIME64_SYSCALLS will be added in subsequent
patches.
* sysdeps/unix/sysv/linux/kernel-features.h
(__ASSUME_TIME64_SYSCALLS): New macro.
---
sysdeps/unix/sysv/linux/kernel-features.h | 59 +++++++++++++++++++++++
1 file changed, 59 insertions(+)
Comments
Hi Zack,
> OK, how does this look?
>
> From dc644211be404aea73b6bd218777c6f06472d9f1 Mon Sep 17 00:00:00 2001
> From: Lukasz Majewski <lukma@denx.de>
> Date: Wed, 28 Aug 2019 14:27:03 -0400
> Subject: [PATCH] y2038: Introduce the __ASSUME_TIME64_SYSCALLS define
>
> Add a macro to linux/kernel-features.h, __ASSUME_TIME64_SYSCALLS, to
> indicate whether the kernel can be assumed to provide a set of system
> calls that process 64-bit time_t.
>
> __ASSUME_TIME64_SYSCALLS does not indicate whether time_t is actually
> 64 bits (that's __TIMEBITS) and also does not indicate whether the
> 64-bit time_t system calls have "time64" suffixes on their names.
>
> Code that uses __ASSUME_TIME64_SYSCALLS will be added in subsequent
> patches.
>
> * sysdeps/unix/sysv/linux/kernel-features.h
> (__ASSUME_TIME64_SYSCALLS): New macro.
> ---
> sysdeps/unix/sysv/linux/kernel-features.h | 59
> +++++++++++++++++++++++ 1 file changed, 59 insertions(+)
>
> diff --git a/sysdeps/unix/sysv/linux/kernel-features.h
> b/sysdeps/unix/sysv/linux/kernel-features.h
> index 1518bb5228..179df79433 100644
> --- a/sysdeps/unix/sysv/linux/kernel-features.h
> +++ b/sysdeps/unix/sysv/linux/kernel-features.h
> @@ -20,6 +20,11 @@
> /* This file must not contain any C code. At least it must be
> protected to allow using the file also in assembler files. */
>
> +#ifndef _LINUX_KERNEL_FEATURES_H
> +#define _LINUX_KERNEL_FEATURES_H 1
I assume that the above is just plain "guard" define (without any extra
meaning for glibc or other library)?
> +
> +#include <bits/wordsize.h>
> +
> #ifndef __LINUX_KERNEL_VERSION
> /* We assume the worst; all kernels should be supported. */
> # define __LINUX_KERNEL_VERSION 0
> @@ -139,3 +144,57 @@
> */
>
> #define __ASSUME_CLONE_DEFAULT 1
> +
> +/* Support for 64-bit time_t in the system call interface. When this
> + flag is set, the kernel provides a version of each of these system
> + calls that accepts 64-bit time_t:
> +
> + clock_adjtime(64)
> + clock_gettime(64)
> + clock_settime(64)
> + clock_getres(_time64)
> + clock_nanosleep(_time64)
> + futex(_time64)
> + mq_timedreceive(_time64)
> + mq_timedsend(_time64)
> + ppoll(_time64)
> + pselect6(_time64)
> + rt_sigtimedwait(_time64)
> + sched_rr_get_interval(_time64)
> + timer_gettime(64)
> + timer_settime(64)
> + timerfd_gettime(64)
> + timerfd_settime(64)
> + utimensat(_time64)
> +
> + On architectures where time_t has historically been 64 bits,
> + only the 64-bit version of each system call exists, and there
> + are no suffixes on the __NR_ constants.
> +
> + On architectures where time_t has historically been 32 bits,
> + both 32-bit and 64-bit versions of each system call may exist,
> + depending on the kernel version. When the 64-bit version exists,
> + there is a '64' or '_time64' suffix on the name of its __NR_
> + constant, as shown above.
> +
> + This flag is always set for Linux 5.1 and later. Prior to that
> + version, it is set only for some CPU architectures and ABIs:
> +
> + - __WORDSIZE == 64 - all supported architectures where pointers
> + are 64 bits also have always had 64-bit time_t.
> +
> + - __WORDSIZE == 32 && __SYSCALL_WORDSIZE == 64 - this describes
> + only one supported configuration, x86's 'x32' subarchitecture,
> + where pointers are 32 bits but time_t has always been 64 bits.
> +
> + __ASSUME_TIME64_SYSCALLS being set does not mean __TIMESIZE is 64,
> + and __TIMESIZE equal to 64 does not mean __ASSUME_TIME64_SYSCALLS
> + is set. All four cases are possible. */
> +
> +#if __LINUX_KERNEL_VERSION >= 0x050100 \
> + || __WORDSIZE == 64 \
> + || (defined __SYSCALL_WORDSIZE && __SYSCALL_WORDSIZE == 64)
> +# define __ASSUME_TIME64_SYSCALLS 1
> +#endif
> +
> +#endif /* kernel-features.h */
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
On Wed, 28 Aug 2019, Zack Weinberg wrote:
> OK, how does this look?
>
> >From dc644211be404aea73b6bd218777c6f06472d9f1 Mon Sep 17 00:00:00 2001
> From: Lukasz Majewski <lukma@denx.de>
> Date: Wed, 28 Aug 2019 14:27:03 -0400
> Subject: [PATCH] y2038: Introduce the __ASSUME_TIME64_SYSCALLS define
>
> Add a macro to linux/kernel-features.h, __ASSUME_TIME64_SYSCALLS, to
> indicate whether the kernel can be assumed to provide a set of system
> calls that process 64-bit time_t.
>
> __ASSUME_TIME64_SYSCALLS does not indicate whether time_t is actually
> 64 bits (that's __TIMEBITS) and also does not indicate whether the
> 64-bit time_t system calls have "time64" suffixes on their names.
>
> Code that uses __ASSUME_TIME64_SYSCALLS will be added in subsequent
> patches.
This version is OK.
On Thu, Aug 29, 2019 at 1:24 PM Joseph Myers <joseph@codesourcery.com> wrote:
>
> On Wed, 28 Aug 2019, Zack Weinberg wrote:
>
> > OK, how does this look?
> >
> > >From dc644211be404aea73b6bd218777c6f06472d9f1 Mon Sep 17 00:00:00 2001
> > From: Lukasz Majewski <lukma@denx.de>
> > Date: Wed, 28 Aug 2019 14:27:03 -0400
> > Subject: [PATCH] y2038: Introduce the __ASSUME_TIME64_SYSCALLS define
> >
> > Add a macro to linux/kernel-features.h, __ASSUME_TIME64_SYSCALLS, to
> > indicate whether the kernel can be assumed to provide a set of system
> > calls that process 64-bit time_t.
> >
> > __ASSUME_TIME64_SYSCALLS does not indicate whether time_t is actually
> > 64 bits (that's __TIMEBITS) and also does not indicate whether the
> > 64-bit time_t system calls have "time64" suffixes on their names.
> >
> > Code that uses __ASSUME_TIME64_SYSCALLS will be added in subsequent
> > patches.
>
> This version is OK.
Great! Thanks for your help Zack.
Do you want to send this out as a patch?
Alistair
>
> --
> Joseph S. Myers
> joseph@codesourcery.com
b/sysdeps/unix/sysv/linux/kernel-features.h
@@ -20,6 +20,11 @@
/* This file must not contain any C code. At least it must be protected
to allow using the file also in assembler files. */
+#ifndef _LINUX_KERNEL_FEATURES_H
+#define _LINUX_KERNEL_FEATURES_H 1
+
+#include <bits/wordsize.h>
+
#ifndef __LINUX_KERNEL_VERSION
/* We assume the worst; all kernels should be supported. */
# define __LINUX_KERNEL_VERSION 0
@@ -139,3 +144,57 @@
*/
#define __ASSUME_CLONE_DEFAULT 1
+
+/* Support for 64-bit time_t in the system call interface. When this
+ flag is set, the kernel provides a version of each of these system
+ calls that accepts 64-bit time_t:
+
+ clock_adjtime(64)
+ clock_gettime(64)
+ clock_settime(64)
+ clock_getres(_time64)
+ clock_nanosleep(_time64)
+ futex(_time64)
+ mq_timedreceive(_time64)
+ mq_timedsend(_time64)
+ ppoll(_time64)
+ pselect6(_time64)
+ rt_sigtimedwait(_time64)
+ sched_rr_get_interval(_time64)
+ timer_gettime(64)
+ timer_settime(64)
+ timerfd_gettime(64)
+ timerfd_settime(64)
+ utimensat(_time64)
+
+ On architectures where time_t has historically been 64 bits,
+ only the 64-bit version of each system call exists, and there
+ are no suffixes on the __NR_ constants.
+
+ On architectures where time_t has historically been 32 bits,
+ both 32-bit and 64-bit versions of each system call may exist,
+ depending on the kernel version. When the 64-bit version exists,
+ there is a '64' or '_time64' suffix on the name of its __NR_
+ constant, as shown above.
+
+ This flag is always set for Linux 5.1 and later. Prior to that
+ version, it is set only for some CPU architectures and ABIs:
+
+ - __WORDSIZE == 64 - all supported architectures where pointers
+ are 64 bits also have always had 64-bit time_t.
+
+ - __WORDSIZE == 32 && __SYSCALL_WORDSIZE == 64 - this describes
+ only one supported configuration, x86's 'x32' subarchitecture,
+ where pointers are 32 bits but time_t has always been 64 bits.
+
+ __ASSUME_TIME64_SYSCALLS being set does not mean __TIMESIZE is 64,
+ and __TIMESIZE equal to 64 does not mean __ASSUME_TIME64_SYSCALLS
+ is set. All four cases are possible. */
+
+#if __LINUX_KERNEL_VERSION >= 0x050100 \
+ || __WORDSIZE == 64 \
+ || (defined __SYSCALL_WORDSIZE && __SYSCALL_WORDSIZE == 64)
+# define __ASSUME_TIME64_SYSCALLS 1
+#endif
+
+#endif /* kernel-features.h */