[v3,1/5] y2038: Introduce __ASSUME_TIME64_SYSCALLS define
Commit Message
This define indicates if the Linux kernel (5.1+) provides 64 bit versions
of time related syscalls (e.g. clock_settime64).
Those syscalls are now (starting from Linux 5.1) available on actively
supported Linux architectures: arm, arm64 (compat mode), m68k, microblaze,
mips, parisc, powerpc, s390, sh, sparc, x86, xtensa.
For x32 this flag is explicitly undefined as this architecture uses time
related syscalls from x86_64 (as if it were __WORDSIZE==64 && __TIMESIZE==64).
* sysdeps/unix/sysv/linux/kernel-features.h: (__ASSUME_TIME64_SYSCALLS):
[__LINUX_KERNEL_VERSION >= 0x050100]: Define.
* sysdeps/unix/sysv/linux/x86_64/kernel-features.h (__ASSUME_TIME64_SYSCALLS):
#undef the __ASSUME_TIME64_SYSCALLS for x32 architecture
---
Changes for v3:
- Provide more detailed and verbose description
- Change name to __ASSUME_TIME64_SYSCALLS
- Undefine __ASSUME_TIME64_SYSCALLS on x32
Changes for v2:
- New patch
---
sysdeps/unix/sysv/linux/kernel-features.h | 38 ++++++++++++++++++++++++
sysdeps/unix/sysv/linux/x86_64/kernel-features.h | 9 ++++++
2 files changed, 47 insertions(+)
@@ -143,3 +143,41 @@
*/
#define __ASSUME_CLONE_DEFAULT 1
+
+#include <bits/wordsize.h>
+#if __WORDSIZE != 64
+/* Support for 64 bit version of time related Linux syscalls.
+
+ 1. Architectures with __WORDSIZE==64 && __TIMESIZE==64 (e.g. x86_64,
+ aarch64) - this flag is never defined (as those already use 64 bit
+ syscalls to handle time).
+
+ 2. Architectures with __WORDSIZE==32 && __TIMESIZE==32 (e.g. arm, x86)
+ 2a. With Y2038 support - userspace must be compiled with
+ -D_TIME_BITS == 64 and as a result __USE_TIME_BITS64 defined
+ (time_t is an alias to time64_t in glibc's exported headers)
+
+ Those systems would use 64 bit Linux system calls to provide 64 bit
+ time support.
+
+ 2b. Without Y2038 support (-D_TIME_BITS not defined or not equal to 64)
+ Such systems would use internally (in glibc) calls to 64 bit syscalls
+ with returning overflow errors after Y2038.
+
+ 3. Architectures with __WORDSIZE==32 && __TIMESIZE==64
+ 3a. __TIMESIZE==64 due to architecture design (for now it is only 'x32')
+ This is a special case as 'x32' architecture has 64 bit size of
+ registers but longs and pointers are 32 bit.
+ It shall use the same time related syscalls as x86_64, so the flag
+ shall be explicitly undefined.
+ 3b. __TIMESIZE==64 imposed by software development (in both cases discussed
+ below the __USE_TIME_BITS64 is defined by default):
+ - For new 32 bit architectures glibc support with 64 bit time support
+ from the outset (which beforehand requires proper syscalls from
+ kernel)
+ - After the 64 bit time support conversion is finished (i.e. arm with
+ Y2038 support). */
+# if __LINUX_KERNEL_VERSION >= 0x050100
+# define __ASSUME_TIME64_SYSCALLS 1
+# endif
+#endif
@@ -24,3 +24,12 @@
#endif
#include_next <kernel-features.h>
+
+/* For x32, which is a special case in respect to 64 bit time support,
+ the __ASSUME_TIME64_SYSCALLS define needs to be explicitly undefined.
+
+ It uses Linux time related syscalls for x86_64 (in compatibility
+ mode). */
+#ifdef __ILP32__
+# undef __ASSUME_TIME64_SYSCALLS
+#endif