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authorAdhemerval Zanella <adhemerval.zanella@linaro.org>2021-02-17 13:35:19 -0300
committerAdhemerval Zanella <adhemerval.zanella@linaro.org>2021-06-15 10:42:11 -0300
commit47f24c21ee38701ae275aa9e451f70fa3e77478c (patch)
treeb4cc52206173fb2ed427a1e797769d12369a89ad /manual
parent8af344feb5ae3e6e3374a6cf2175b44cc904a94e (diff)
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y2038: Add support for 64-bit time on legacy ABIs
A new build flag, _TIME_BITS, enables the usage of the newer 64-bit time symbols for legacy ABI (where 32-bit time_t is default). The 64 bit time support is only enabled if LFS (_FILE_OFFSET_BITS=64) is also used. Different than LFS support, the y2038 symbols are added only for the required ABIs (armhf, csky, hppa, i386, m68k, microblaze, mips32, mips64-n32, nios2, powerpc32, sparc32, s390-32, and sh). The ABIs with 64-bit time support are unchanged, both for symbol and types redirection. On Linux the full 64-bit time support requires a minimum of kernel version v5.1. Otherwise, the 32-bit fallbacks are used and might results in error with overflow return code (EOVERFLOW). The i686-gnu does not yet support 64-bit time. This patch exports following rediretions to support 64-bit time: * libc: adjtime adjtimex clock_adjtime clock_getres clock_gettime clock_nanosleep clock_settime cnd_timedwait ctime ctime_r difftime fstat fstatat futimens futimes futimesat getitimer getrusage gettimeofday gmtime gmtime_r localtime localtime_r lstat_time lutimes mktime msgctl mtx_timedlock nanosleep nanosleep ntp_gettime ntp_gettimex ppoll pselec pselect pthread_clockjoin_np pthread_cond_clockwait pthread_cond_timedwait pthread_mutex_clocklock pthread_mutex_timedlock pthread_rwlock_clockrdlock pthread_rwlock_clockwrlock pthread_rwlock_timedrdlock pthread_rwlock_timedwrlock pthread_timedjoin_np recvmmsg sched_rr_get_interval select sem_clockwait semctl semtimedop sem_timedwait setitimer settimeofday shmctl sigtimedwait stat thrd_sleep time timegm timerfd_gettime timerfd_settime timespec_get utime utimensat utimes utimes wait3 wait4 * librt: aio_suspend mq_timedreceive mq_timedsend timer_gettime timer_settime * libanl: gai_suspend Reviewed-by: Lukasz Majewski <lukma@denx.de> Reviewed-by: Carlos O'Donell <carlos@redhat.com> Tested-by: Carlos O'Donell <carlos@redhat.com>
Diffstat (limited to 'manual')
-rw-r--r--manual/creature.texi44
1 files changed, 44 insertions, 0 deletions
diff --git a/manual/creature.texi b/manual/creature.texi
index 705a949..9fa658e 100644
--- a/manual/creature.texi
+++ b/manual/creature.texi
@@ -165,6 +165,50 @@ This macro was introduced as part of the Large File Support extension
(LFS).
@end defvr
+@defvr Macro _TIME_BITS
+This macro determines the bit size of @code{time_t} (and therefore the
+bit size of all @code{time_t} derived types and the prototypes of all
+related functions). If @code{_TIME_BITS} is undefined, the bit size of
+@code{time_t} is architecture dependent.
+
+Possible values of @code{_TIME_BITS}:
+@enumerate
+@item
+@code{_TIME_BITS=64} and port from the outset uses 64-bit
+@code{time_t} and word size equals to @w{64 bits} (e.g. x86_64) - no
+action
+
+@item
+@code{_TIME_BITS=32} and port from the outset uses 32-bit
+@code{time_t} and word size equals to @w{64 bits} (e.g. ARM) - no
+action
+
+@item
+@code{_TIME_BITS=64} and port from the outset uses 64-bit
+@code{time_t} and word size equals to @w{32 bits} (e.g. ARC, RV32)
+- no action
+
+@item
+@code{_TIME_BITS=64} and port from the outset uses 32-bit
+@code{time_t} and word size equals to @w{32 bits} (e.g. ARM)
+- the @code{time_t} is modified to be able to hold 64-bit time.
+
+@item
+For any other use case the compile-time error is emitted.
+@end enumerate
+
+The @code{_TIME_BITS} can be only used when @code{_FILE_OFFSET_BITS=64}
+is also defined.
+
+For the point @b{4} above, calls to proper syscalls depend on the
+Linux kernel version on which the system is running. For Linux kernel
+version above @b{5.1} syscalls supporting 64-bit time are used. Otherwise,
+a fallback code is used with legacy (i.e. 32-bit) syscalls.
+
+By using this macro certain ports gain support for 64-bit time and as
+a result become immune to Y2038 problem.
+@end defvr
+
@defvr Macro _ISOC99_SOURCE
@standards{GNU, (none)}
If this macro is defined, features from ISO C99 are included. Since