Patchwork [v9] y2038: Introduce struct __timespec64 - new internal glibc type

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Submitter Lukasz Majewski
Date Sept. 26, 2019, 1:32 p.m.
Message ID <20190926133223.5814-1-lukma@denx.de>
Download mbox | patch
Permalink /patch/34681/
State New
Headers show

Comments

Lukasz Majewski - Sept. 26, 2019, 1:32 p.m.
This type is a glibc's "internal" 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 unnamed 32 bit
padding bit-field has been introduced. The placement of it depends on
the endianness of the SoC.

Tested on x86_64 and ARM.

* include/time.h: Add struct __timespec64 definition

---
Changes for v9:
- Adjust the subject line for the patch
- Use unnamed bit-field padding instead of explicit tv_pad

Changes for v8:
- Replace #if __WORDSIZE == 64 \
           || (defined __SYSCALL_WORDSIZE && __SYSCALL_WORDSIZE == 64)
  condition with #if __TIMESIZE == 64
  to allow usage of struct __timespec64 aliased to timespec on ports
  supporting 64 bit time API from the outset.

  Architectures with __TIMESIZE == 32 will use struct __timespec64 with
  __time64_t tv_sec and __int32_t tv_pad and tv_nsec.

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
  __timespec64).

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 | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)
Joseph Myers - Sept. 26, 2019, 4:01 p.m.
On Thu, 26 Sep 2019, Lukasz Majewski wrote:

> This type is a glibc's "internal" 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 unnamed 32 bit
> padding bit-field has been introduced. The placement of it depends on
> the endianness of the SoC.
> 
> Tested on x86_64 and ARM.
> 
> * include/time.h: Add struct __timespec64 definition

This patch is OK, please commit.

Patch

diff --git a/include/time.h b/include/time.h
index dcf91855ad..9727786634 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 +50,29 @@  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 __TIMESIZE == 64
+# define __timespec64 timespec
+#else
+/* 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 unnamed bit-field padding.
+
+   As a general rule the Linux kernel is ignoring upper 32 bits of
+   tv_nsec field.  */
+struct __timespec64
+{
+  __time64_t tv_sec;         /* Seconds */
+# if BYTE_ORDER == BIG_ENDIAN
+  __int32_t :32;             /* Padding */
+  __int32_t tv_nsec;         /* Nanoseconds */
+# else
+  __int32_t tv_nsec;         /* Nanoseconds */
+  __int32_t :32;             /* Padding */
+# endif
+};
+#endif
+
 #if __TIMESIZE == 64
 # define __ctime64 ctime
 #else