[v3,5/5] y2038: Support for Y2038 safe time on 32 bit systems
Commit Message
The time_t type is now Y2038 safe, which means that it is aliased to
__time64_t when __USE_TIME_BITS64 is defined or __time_t otherwise.
On the contrary the __time_t for 32 bit systems is only 32 bit, so for
Y2038 safe system it must be 64 bit (as is time_t)
This patch introduces the Y2038 specific code to make clock_settime/
__clock_settime64 Y2038 safe on 32 bit systems.
This goal is achieved by using aliasing to clock_settime names when
__USE_TIME_BITS64 is defined.
As a result user programs call 64 bit versions of functions (i.e.
__clock_settime64 instead of __clock_settime), which must have been
globally visible for this purpose - for non Y2038 safe code those are
hidden in glibc.
* include/features.h:
Add logic to set __USE_TIME_BITS64 according to passed (when building
userspace Y2038 safe program on 32 bit system) _TIME_BITS and
_FILE_OFFSET_BITS
* manual/creature.texi: Add description of _TIME_BITS
* time/bits/types/time_t.h:
Use __time64_t as time_t when __USE_TIME_BITS64 is defined
* time/bits/types/struct_timespec.h:
Replace tv_sec's __time_t type to Y2038 safe time_t
* include/time.h:
Remove libc_hidden_proto (__clock_settime64) - make the __clock_settime64
publicly available for Y2038 safe system
* time/time.h: Redirect clock_settime call to __clock_settime64 on 32 bit
Y2038 safe systems
* time/Versions (GLIBC_PRIVATE):
Export __clock_settime64 function as glibc private one, to be accessible from
user programs when y2038 support is enabled
* time/bits/types/struct_timespec.h:
Add unnamed padding around tv_nsec when __USE_TIME_BITS64 is defined
---
Changes for v3:
- Only support clock_settime conversion to be Y2038 (use it as an example
conversion code)
Changes for v2:
- Introduce unnamed padding in the struct timespec exported by glibc
(to the /usr/include)
---
include/features.h | 19 +++++++++++++++++++
include/time.h | 3 ++-
manual/creature.texi | 28 ++++++++++++++++++++++++++++
time/Versions | 3 +++
time/bits/types/struct_timespec.h | 15 +++++++++++++--
time/bits/types/time_t.h | 4 ++++
time/time.h | 9 +++++++++
7 files changed, 78 insertions(+), 3 deletions(-)
Comments
On Mai 07 2019, Lukasz Majewski <lukma@denx.de> wrote:
> diff --git a/include/features.h b/include/features.h
> index e016b3e5c7..153c6320f0 100644
> --- a/include/features.h
> +++ b/include/features.h
> @@ -365,6 +365,25 @@
> # define __USE_FILE_OFFSET64 1
> #endif
>
> +/* We need to know the word size in order to check the time size. */
> +#include <bits/wordsize.h>
> +
> +#if defined _TIME_BITS
> +# if _TIME_BITS == 64
> +# if ! defined (_FILE_OFFSET_BITS) || _FILE_OFFSET_BITS != 64
> +# error _TIME_BITS==64 is allowed only when _FILE_OFFSET_BITS==64
Perhaps:
# error _TIME_BITS=64 is allowed only with _FILE_OFFSET_BITS=64
Andreas.
@@ -365,6 +365,25 @@
# define __USE_FILE_OFFSET64 1
#endif
+/* We need to know the word size in order to check the time size. */
+#include <bits/wordsize.h>
+
+#if defined _TIME_BITS
+# if _TIME_BITS == 64
+# if ! defined (_FILE_OFFSET_BITS) || _FILE_OFFSET_BITS != 64
+# error _TIME_BITS==64 is allowed only when _FILE_OFFSET_BITS==64
+# elif __WORDSIZE == 32
+# define __USE_TIME_BITS64 1
+# endif
+# elif _TIME_BITS == 32
+# if __WORDSIZE > 32
+# error _TIME_BITS=32 is not compatible with __WORDSIZE > 32
+# endif
+# else
+# error Invalid _TIME_BITS value (can only be 32 or 64)
+# endif
+#endif
+
#if defined _DEFAULT_SOURCE
# define __USE_MISC 1
#endif
@@ -132,7 +132,8 @@ libc_hidden_proto (__timegm64)
#else
extern int __clock_settime64 (clockid_t clock_id,
const struct __timespec64 *tp);
-libc_hidden_proto (__clock_settime64)
+/* For Y2038 safe system the __clock_settime64 needs to be a visible
+ symbol as a replacement for Y2038 unsafe clock_settime. */
#endif
/* Compute the `struct tm' representation of T,
@@ -165,6 +165,34 @@ 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
+time_t equals the bit size of the architecture.
+
+If @code{_TIME_BITS} is undefined, or if @code{_TIME_BITS} is defined
+to the value @code{32} and @code{__WORDSIZE} is defined to the value
+@code{32}, or or if @code{_TIME_BITS} is defined to the value @code{64}
+and @code{__WORDSIZE} is defined to the value @code{64}, nothing changes.
+
+If @code{_TIME_BITS} is defined to the value @code{64} and if
+@code{__WORDSIZE} is defined to the value @code{32}, then the @w{64 bit}
+time API and implementation are used even though the architecture word
+size is @code{32}. Also, if the kernel provides @w{64 bit} time support,
+it is used; otherwise, the @w{32 bit} kernel time support is used (with
+no provision to address kernel Y2038 shortcomings).
+
+If @code{_TIME_BITS} is defined to the value @code{32} and if
+@code{__WORDSIZE} is defined to the value @code{64}, then a compile-time
+error is emitted.
+
+If @code{_TIME_BITS} is defined to a value different from both @code{32}
+and @code{64}, then a compile-time error is emitted.
+
+This macro was introduced as part of the Y2038 support.
+@end defvr
+
@defvr Macro _ISOC99_SOURCE
@standards{GNU, (none)}
If this macro is defined, features from ISO C99 are included. Since
@@ -1,4 +1,7 @@
libc {
+ GLIBC_PRIVATE {
+ __clock_settime64;
+ }
GLIBC_2.0 {
# global variables
__daylight; __timezone; __tzname;
@@ -3,13 +3,24 @@
#define _STRUCT_TIMESPEC 1
#include <bits/types.h>
+#include <bits/types/time_t.h>
/* POSIX.1b structure for a time value. This is like a `struct timeval' but
has nanoseconds instead of microseconds. */
struct timespec
{
- __time_t tv_sec; /* Seconds. */
- __syscall_slong_t tv_nsec; /* Nanoseconds. */
+ time_t tv_sec; /* Seconds. */
+# ifdef __USE_TIME_BITS64
+# if __BYTE_ORDER == __BIG_ENDIAN
+ int : 32;
+ __syscall_slong_t tv_nsec; /* Nanoseconds. */
+# else
+ __syscall_slong_t tv_nsec; /* Nanoseconds. */
+ int : 32;
+# endif
+# else
+ __syscall_slong_t tv_nsec; /* Nanoseconds. */
+# endif
};
#endif
@@ -4,6 +4,10 @@
#include <bits/types.h>
/* Returned by `time'. */
+#ifdef __USE_TIME_BITS64
+typedef __time64_t time_t;
+#else
typedef __time_t time_t;
+#endif
#endif
@@ -222,6 +222,15 @@ extern int clock_gettime (clockid_t __clock_id, struct timespec *__tp) __THROW;
extern int clock_settime (clockid_t __clock_id, const struct timespec *__tp)
__THROW;
+#ifdef __USE_TIME_BITS64
+# if defined(__REDIRECT)
+extern int __REDIRECT (clock_settime, (clockid_t __clock_id, const struct
+ timespec *__tp), __clock_settime64) __THROW;
+# else
+# define clock_settime __clock_settime64
+# endif
+#endif
+
# ifdef __USE_XOPEN2K
/* High-resolution sleep with the specified clock.