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>

1 files changed, 44 insertions, 0 deletions

diff --git a/manual/creature.texi b/manual/creature.texi
index 705a949089..9fa658e9a7 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