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authorDeepa Dinamani <deepa.kernel@gmail.com>2018-07-03 08:44:20 +0300
committerArnd Bergmann <arnd@arndb.de>2019-02-07 02:13:27 +0300
commit2c620ff93d9fbd5d644760d4c21d389078ec1080 (patch)
tree7551f4b90d06464a3d95e3f2995b52e8dde711b9 /include/linux/timex.h
parent4d5f007eedb74d71a7bde2bff69b6a31ad8ab427 (diff)
downloadlinux-2c620ff93d9fbd5d644760d4c21d389078ec1080.tar.xz
time: Add struct __kernel_timex
struct timex uses struct timeval internally. struct timeval is not y2038 safe. Introduce a new UAPI type struct __kernel_timex that is y2038 safe. struct __kernel_timex uses a timeval type that is similar to struct __kernel_timespec which preserves the same structure size across 32 bit and 64 bit ABIs. struct __kernel_timex also restructures other members of the structure to make the structure the same on 64 bit and 32 bit architectures. Note that struct __kernel_timex is the same as struct timex on a 64 bit architecture. The above solution is similar to other new y2038 syscalls that are being introduced: both 32 bit and 64 bit ABIs have a common entry, and the compat entry supports the old 32 bit syscall interface. Alternatives considered were: 1. Add new time type to struct timex that makes use of padded bits. This time type could be based on the struct __kernel_timespec. modes will use a flag to notify which time structure should be used internally. This needs some application level changes on both 64 bit and 32 bit architectures. Although 64 bit machines could continue to use the older timeval structure without any changes. 2. Add a new u8 type to struct timex that makes use of padded bits. This can be used to save higher order tv_sec bits. modes will use a flag to notify presence of such a type. This will need some application level changes on 32 bit architectures. 3. Add a new compat_timex structure that differs in only the size of the time type; keep rest of struct timex the same. This requires extra syscalls to manage all 3 cases on 64 bit architectures. This will not need any application level changes but will add more complexity from kernel side. Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Diffstat (limited to 'include/linux/timex.h')
-rw-r--r--include/linux/timex.h7
1 files changed, 7 insertions, 0 deletions
diff --git a/include/linux/timex.h b/include/linux/timex.h
index 39c25dbebfe8..7f40e9e42ecc 100644
--- a/include/linux/timex.h
+++ b/include/linux/timex.h
@@ -53,6 +53,13 @@
#ifndef _LINUX_TIMEX_H
#define _LINUX_TIMEX_H
+/* CONFIG_64BIT_TIME enables new 64 bit time_t syscalls in the compat path
+ * and 32-bit emulation.
+ */
+#ifndef CONFIG_64BIT_TIME
+#define __kernel_timex timex
+#endif
+
#include <uapi/linux/timex.h>
#define ADJ_ADJTIME 0x8000 /* switch between adjtime/adjtimex modes */