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Subject[PATCH 03/12] x86/vsyscall: use common implementation for vgettimeofday
Date
There are two implementations of vgettimeofday; one as a vsyscall
and one in the vdso. The are functionally identical, but the code
is duplicated in two more-or-less equivalent forms.

The vdso implementation is also shared with the vdso vclock_gettime.

To unify the two implementations, the vdso code is hoisted into vgtod.h
as inline functions, and the callers modified accordingly. Because
vdso and vsyscall have different ways to access struct vsyscall_gtod_data,
it is passed into each function.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: John Wright <john.wright@hp.com>
Cc: Ingo Molnar <mingo@elte.hu>
---
arch/x86/include/asm/vgtod.h | 64 +++++++++++++++++++++++++++++++++++++++-
arch/x86/kernel/vsyscall_64.c | 61 +-------------------------------------
arch/x86/vdso/vclock_gettime.c | 46 ++---------------------------
3 files changed, 67 insertions(+), 104 deletions(-)

diff --git a/arch/x86/include/asm/vgtod.h b/arch/x86/include/asm/vgtod.h
index dc27a69..9045ea4 100644
--- a/arch/x86/include/asm/vgtod.h
+++ b/arch/x86/include/asm/vgtod.h
@@ -1,9 +1,11 @@
#ifndef _ASM_X86_VGTOD_H
#define _ASM_X86_VGTOD_H

-#include <asm/vsyscall.h>
#include <linux/clocksource.h>

+#include <asm/vsyscall.h>
+#include <asm/unistd.h>
+
struct vsyscall_gtod_data {
seqlock_t lock;

@@ -26,4 +28,64 @@ extern struct vsyscall_gtod_data __vsyscall_gtod_data
__section_vsyscall_gtod_data;
extern struct vsyscall_gtod_data vsyscall_gtod_data;

+/*
+ * Common implementation of vdso/vsyscall time functions. This code
+ * is used in usermode, exported via either vdso or vsyscall. Because
+ * of this, it must be inlined rather than linked, hence implemented
+ * in a .h as inline functions.
+ */
+notrace static __always_inline
+long vgetns(const struct vsyscall_gtod_data *gtod)
+{
+ long v;
+ cycles_t (*vread)(void);
+
+ vread = gtod->clock.vread;
+ v = (vread() - gtod->clock.cycle_last) & gtod->clock.mask;
+ return (v * gtod->clock.mult) >> gtod->clock.shift;
+}
+
+notrace static __always_inline
+int __do_realtime(const struct vsyscall_gtod_data *gtod,
+ struct timespec *ts)
+{
+ unsigned long seq, ns;
+ do {
+ seq = read_seqbegin(&gtod->lock);
+ ts->tv_sec = gtod->wall_time_sec;
+ ts->tv_nsec = gtod->wall_time_nsec;
+ ns = vgetns(gtod);
+ } while (unlikely(read_seqretry(&gtod->lock, seq)));
+ timespec_add_ns(ts, ns);
+ return 0;
+}
+
+notrace static __always_inline
+int __do_vgettimeofday(const struct vsyscall_gtod_data *gtod,
+ struct timeval *tv, struct timezone *tz)
+{
+ long ret;
+
+ if (likely(gtod->sysctl_enabled && gtod->clock.vread)) {
+ if (likely(tv != NULL)) {
+ BUILD_BUG_ON(offsetof(struct timeval, tv_usec) !=
+ offsetof(struct timespec, tv_nsec) ||
+ sizeof(*tv) != sizeof(struct timespec));
+ __do_realtime(gtod, (struct timespec *)tv);
+ tv->tv_usec /= 1000;
+ }
+
+ if (unlikely(tz != NULL)) {
+ /* Avoid memcpy. Some old compilers fail to inline it */
+ tz->tz_minuteswest = gtod->sys_tz.tz_minuteswest;
+ tz->tz_dsttime = gtod->sys_tz.tz_dsttime;
+ }
+ return 0;
+ }
+
+ asm("syscall" : "=a" (ret) :
+ "0" (__NR_gettimeofday), "D" (tv), "S" (tz) : "memory");
+ return ret;
+}
+
#endif /* _ASM_X86_VGTOD_H */
diff --git a/arch/x86/kernel/vsyscall_64.c b/arch/x86/kernel/vsyscall_64.c
index f71dda9..e19a60e 100644
--- a/arch/x86/kernel/vsyscall_64.c
+++ b/arch/x86/kernel/vsyscall_64.c
@@ -90,24 +90,6 @@ void update_vsyscall(struct timespec *wall_time, struct clocksource *clock)
write_sequnlock_irqrestore(&vsyscall_gtod_data.lock, flags);
}

-/* RED-PEN may want to readd seq locking, but then the variable should be
- * write-once.
- */
-static __always_inline void do_get_tz(struct timezone * tz)
-{
- *tz = __vsyscall_gtod_data.sys_tz;
-}
-
-static __always_inline int gettimeofday(struct timeval *tv, struct timezone *tz)
-{
- int ret;
- asm volatile("syscall"
- : "=a" (ret)
- : "0" (__NR_gettimeofday),"D" (tv),"S" (tz)
- : __syscall_clobber );
- return ret;
-}
-
static __always_inline long time_syscall(long *t)
{
long secs;
@@ -117,50 +99,9 @@ static __always_inline long time_syscall(long *t)
return secs;
}

-static __always_inline void do_vgettimeofday(struct timeval * tv)
-{
- cycle_t now, base, mask, cycle_delta;
- unsigned seq;
- unsigned long mult, shift, nsec;
- cycle_t (*vread)(void);
- do {
- seq = read_seqbegin(&__vsyscall_gtod_data.lock);
-
- vread = __vsyscall_gtod_data.clock.vread;
- if (unlikely(!__vsyscall_gtod_data.sysctl_enabled || !vread)) {
- gettimeofday(tv,NULL);
- return;
- }
-
- now = vread();
- base = __vsyscall_gtod_data.clock.cycle_last;
- mask = __vsyscall_gtod_data.clock.mask;
- mult = __vsyscall_gtod_data.clock.mult;
- shift = __vsyscall_gtod_data.clock.shift;
-
- tv->tv_sec = __vsyscall_gtod_data.wall_time_sec;
- nsec = __vsyscall_gtod_data.wall_time_nsec;
- } while (read_seqretry(&__vsyscall_gtod_data.lock, seq));
-
- /* calculate interval: */
- cycle_delta = (now - base) & mask;
- /* convert to nsecs: */
- nsec += (cycle_delta * mult) >> shift;
-
- while (nsec >= NSEC_PER_SEC) {
- tv->tv_sec += 1;
- nsec -= NSEC_PER_SEC;
- }
- tv->tv_usec = nsec / NSEC_PER_USEC;
-}
-
int __vsyscall(0) vgettimeofday(struct timeval * tv, struct timezone * tz)
{
- if (tv)
- do_vgettimeofday(tv);
- if (tz)
- do_get_tz(tz);
- return 0;
+ return __do_vgettimeofday(&__vsyscall_gtod_data, tv, tz);
}

/* This will break when the xtime seconds get inaccurate, but that is
diff --git a/arch/x86/vdso/vclock_gettime.c b/arch/x86/vdso/vclock_gettime.c
index 6a40b78..723a84f 100644
--- a/arch/x86/vdso/vclock_gettime.c
+++ b/arch/x86/vdso/vclock_gettime.c
@@ -34,28 +34,6 @@ notrace static long vdso_fallback_gettime(long clock, struct timespec *ts)
return ret;
}

-notrace static inline long vgetns(void)
-{
- long v;
- cycles_t (*vread)(void);
- vread = gtod->clock.vread;
- v = (vread() - gtod->clock.cycle_last) & gtod->clock.mask;
- return (v * gtod->clock.mult) >> gtod->clock.shift;
-}
-
-notrace static noinline int do_realtime(struct timespec *ts)
-{
- unsigned long seq, ns;
- do {
- seq = read_seqbegin(&gtod->lock);
- ts->tv_sec = gtod->wall_time_sec;
- ts->tv_nsec = gtod->wall_time_nsec;
- ns = vgetns();
- } while (unlikely(read_seqretry(&gtod->lock, seq)));
- timespec_add_ns(ts, ns);
- return 0;
-}
-
/* Copy of the version in kernel/time.c which we cannot directly access */
notrace static void
vset_normalized_timespec(struct timespec *ts, long sec, long nsec)
@@ -78,7 +56,7 @@ notrace static noinline int do_monotonic(struct timespec *ts)
do {
seq = read_seqbegin(&gtod->lock);
secs = gtod->wall_time_sec;
- ns = gtod->wall_time_nsec + vgetns();
+ ns = gtod->wall_time_nsec + vgetns(gtod);
secs += gtod->wall_to_monotonic.tv_sec;
ns += gtod->wall_to_monotonic.tv_nsec;
} while (unlikely(read_seqretry(&gtod->lock, seq)));
@@ -91,7 +69,7 @@ notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
if (likely(gtod->sysctl_enabled && gtod->clock.vread))
switch (clock) {
case CLOCK_REALTIME:
- return do_realtime(ts);
+ return __do_realtime(gtod, ts);
case CLOCK_MONOTONIC:
return do_monotonic(ts);
}
@@ -102,25 +80,7 @@ int clock_gettime(clockid_t, struct timespec *)

notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
{
- long ret;
- if (likely(gtod->sysctl_enabled && gtod->clock.vread)) {
- if (likely(tv != NULL)) {
- BUILD_BUG_ON(offsetof(struct timeval, tv_usec) !=
- offsetof(struct timespec, tv_nsec) ||
- sizeof(*tv) != sizeof(struct timespec));
- do_realtime((struct timespec *)tv);
- tv->tv_usec /= 1000;
- }
- if (unlikely(tz != NULL)) {
- /* Avoid memcpy. Some old compilers fail to inline it */
- tz->tz_minuteswest = gtod->sys_tz.tz_minuteswest;
- tz->tz_dsttime = gtod->sys_tz.tz_dsttime;
- }
- return 0;
- }
- asm("syscall" : "=a" (ret) :
- "0" (__NR_gettimeofday), "D" (tv), "S" (tz) : "memory");
- return ret;
+ return __do_vgettimeofday(gtod, tv, tz);
}
int gettimeofday(struct timeval *, struct timezone *)
__attribute__((weak, alias("__vdso_gettimeofday")));
--
1.6.2.5


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