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[PATCH v7 1/3] y2038: Introduce internal for glibc struct __timespec64

This type is a glibc's type similar to struct timespec but whose tv_sec
field is a __time64_t rather than a time_t, which makes it Y2038-proof and
usable to pass syscalls between user code and Y2038-proof kernel.

To support passing this structure to the kernel - the tv_pad, 32 bit int,
has been introduced. The placement of it depends on endianness of the SoC.

Tested on x86_64 and ARM.

* include/time.h: Add struct __timespec64 definition

Changes for v7:
- None

Changes for v6:
- None

Changes for v5:
- Reword commit message
- Add missing preprocessor condition for x32 (to use timespec instead of

Changes for v4:
- Change tv_pad's type from named bitfield to 32 bit int

Changes for v3:
- Replace __TIMESIZE with __WORDSIZE (as architectures with __TIMESIZE==64
  will need to use this struct with 32 bit tv_nsec field).
- Update in-code comment

Changes for v2:
- None
 include/time.h | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/include/time.h b/include/time.h
index dcf91855ad..862d29b8f7 100644
--- a/include/time.h
+++ b/include/time.h
@@ -5,6 +5,7 @@
 # include <bits/types/locale_t.h>
 # include <stdbool.h>
 # include <time/mktime-internal.h>
+# include <endian.h>
 extern __typeof (strftime_l) __strftime_l;
 libc_hidden_proto (__strftime_l)
@@ -49,6 +50,30 @@ extern void __tzset_parse_tz (const char *tz) attribute_hidden;
 extern void __tz_compute (__time64_t timer, struct tm *tm, int use_localtime)
   __THROW attribute_hidden;
+#if __WORDSIZE == 64 \
+  || (defined __SYSCALL_WORDSIZE && __SYSCALL_WORDSIZE == 64)
+# define __timespec64 timespec
+/* The glibc Y2038-proof struct __timespec64 structure for a time value.
+   To keep things Posix-ish, we keep the nanoseconds field a 32-bit
+   signed long, but since the Linux field is a 64-bit signed int, we
+   pad our tv_nsec with a 32-bit int.
+   As a general rule the Linux kernel is ignoring upper 32 bits of
+   tv_nsec field.  */
+struct __timespec64
+  __time64_t tv_sec;         /* Seconds */
+  __int32_t tv_pad;          /* Padding */
+  __int32_t tv_nsec;         /* Nanoseconds */
+# else
+  __int32_t tv_nsec;         /* Nanoseconds */
+  __int32_t tv_pad;          /* Padding */
+# endif
 #if __TIMESIZE == 64
 # define __ctime64 ctime

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