[v4,1/3] y2038: Introduce internal for glibc struct __timespec64
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Message ID 20190520102723.5380-2-lukma@denx.de
State New
Headers show
  • y2038: Linux: Provide __clock_settime64 function supporting 64 bit time
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Commit Message

Lukasz Majewski May 20, 2019, 10:27 a.m. UTC
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 between user
code and Y2038-proof kernel syscalls (e.g. clock_gettime()).

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 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 mbox series

diff --git a/include/time.h b/include/time.h
index ac3163c2a5..7dabb7a568 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)
@@ -51,6 +52,30 @@  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
+# 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. However, there are architectures with potential need
+   for clearing the padding (i.e. 'x32').  */
+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