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authorAndy Lutomirski <luto@MIT.EDU>2011-05-23 17:31:30 +0400
committerThomas Gleixner <tglx@linutronix.de>2011-05-24 16:51:29 +0400
commitf144a6b4d1688675d88990e29567b2335b48205e (patch)
tree80001b7e1c1fd3b4877febd416d3d0c949edd6c3 /arch/x86/vdso
parent6447facba36e3fff77ab4c68f46297a5dab024c8 (diff)
downloadlinux-f144a6b4d1688675d88990e29567b2335b48205e.tar.xz
x86-64: Add time to vDSO
The only fast implementation of time(2) we expose is through the vsyscall page and we want to get userspace to stop using the vsyscall page. So make it available through the vDSO as well. This is essentially a cut-n-paste job. Signed-off-by: Andy Lutomirski <luto@mit.edu> Cc: Andi Kleen <andi@firstfloor.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: "David S. Miller" <davem@davemloft.net> Cc: Eric Dumazet <eric.dumazet@gmail.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Borislav Petkov <bp@amd64.org> Link: http://lkml.kernel.org/r/%3Cbf963bac5207de4b29613f27c42705e4371812a8.1306156808.git.luto%40mit.edu%3E Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'arch/x86/vdso')
-rw-r--r--arch/x86/vdso/vclock_gettime.c35
-rw-r--r--arch/x86/vdso/vdso.lds.S2
2 files changed, 36 insertions, 1 deletions
diff --git a/arch/x86/vdso/vclock_gettime.c b/arch/x86/vdso/vclock_gettime.c
index 28b2c00bd1be..e6e9f90a8cd7 100644
--- a/arch/x86/vdso/vclock_gettime.c
+++ b/arch/x86/vdso/vclock_gettime.c
@@ -2,7 +2,7 @@
* Copyright 2006 Andi Kleen, SUSE Labs.
* Subject to the GNU Public License, v.2
*
- * Fast user context implementation of clock_gettime and gettimeofday.
+ * Fast user context implementation of clock_gettime, gettimeofday, and time.
*
* The code should have no internal unresolved relocations.
* Check with readelf after changing.
@@ -160,3 +160,36 @@ notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
}
int gettimeofday(struct timeval *, struct timezone *)
__attribute__((weak, alias("__vdso_gettimeofday")));
+
+/* This will break when the xtime seconds get inaccurate, but that is
+ * unlikely */
+
+static __always_inline long time_syscall(long *t)
+{
+ long secs;
+ asm volatile("syscall"
+ : "=a" (secs)
+ : "0" (__NR_time), "D" (t) : "cc", "r11", "cx", "memory");
+ return secs;
+}
+
+notrace time_t __vdso_time(time_t *t)
+{
+ unsigned seq;
+ time_t result;
+ if (unlikely(!VVAR(vsyscall_gtod_data).sysctl_enabled))
+ return time_syscall(t);
+
+ do {
+ seq = read_seqbegin(&VVAR(vsyscall_gtod_data).lock);
+
+ result = VVAR(vsyscall_gtod_data).wall_time_sec;
+
+ } while (read_seqretry(&VVAR(vsyscall_gtod_data).lock, seq));
+
+ if (t)
+ *t = result;
+ return result;
+}
+int time(time_t *t)
+ __attribute__((weak, alias("__vdso_time")));
diff --git a/arch/x86/vdso/vdso.lds.S b/arch/x86/vdso/vdso.lds.S
index 81f250011f71..b96b2677cad8 100644
--- a/arch/x86/vdso/vdso.lds.S
+++ b/arch/x86/vdso/vdso.lds.S
@@ -23,6 +23,8 @@ VERSION {
__vdso_gettimeofday;
getcpu;
__vdso_getcpu;
+ time;
+ __vdso_time;
local: *;
};
}