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Subject[RFC 2/2] x86-64: Add __vdso_clock_gettime_ns vsyscall
Date
This is just for the ABI.  An optimized implementation will come later.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
---
arch/x86/vdso/vclock_gettime.c | 70 ++++++++++++++++++++++++++++++---------
arch/x86/vdso/vdso.lds.S | 7 ++++
2 files changed, 61 insertions(+), 16 deletions(-)
diff --git a/arch/x86/vdso/vclock_gettime.c b/arch/x86/vdso/vclock_gettime.c
index 6bc0e72..79d6919 100644
--- a/arch/x86/vdso/vclock_gettime.c
+++ b/arch/x86/vdso/vclock_gettime.c
@@ -82,7 +82,7 @@ notrace static inline long vgetns(void)
return (v * gtod->clock.mult) >> gtod->clock.shift;
}

-notrace static noinline int do_realtime(struct timespec *ts)
+notrace static noinline void do_realtime(struct timespec *ts)
{
unsigned long seq, ns;
do {
@@ -92,10 +92,9 @@ notrace static noinline int do_realtime(struct timespec *ts)
ns = vgetns();
} while (unlikely(read_seqretry(&gtod->lock, seq)));
timespec_add_ns(ts, ns);
- return 0;
}

-notrace static noinline int do_monotonic(struct timespec *ts)
+notrace static noinline void do_monotonic(struct timespec *ts)
{
unsigned long seq, ns, secs;
do {
@@ -115,11 +114,9 @@ notrace static noinline int do_monotonic(struct timespec *ts)
}
ts->tv_sec = secs;
ts->tv_nsec = ns;
-
- return 0;
}

-notrace static noinline int do_realtime_coarse(struct timespec *ts)
+notrace static noinline void do_realtime_coarse(struct timespec *ts)
{
unsigned long seq;
do {
@@ -127,10 +124,9 @@ notrace static noinline int do_realtime_coarse(struct timespec *ts)
ts->tv_sec = gtod->wall_time_coarse.tv_sec;
ts->tv_nsec = gtod->wall_time_coarse.tv_nsec;
} while (unlikely(read_seqretry(&gtod->lock, seq)));
- return 0;
}

-notrace static noinline int do_monotonic_coarse(struct timespec *ts)
+notrace static noinline void do_monotonic_coarse(struct timespec *ts)
{
unsigned long seq, ns, secs;
do {
@@ -150,25 +146,29 @@ notrace static noinline int do_monotonic_coarse(struct timespec *ts)
}
ts->tv_sec = secs;
ts->tv_nsec = ns;
-
- return 0;
}

notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
{
switch (clock) {
case CLOCK_REALTIME:
- if (likely(gtod->clock.vclock_mode != VCLOCK_NONE))
- return do_realtime(ts);
+ if (likely(gtod->clock.vclock_mode != VCLOCK_NONE)) {
+ do_realtime(ts);
+ return 0;
+ }
break;
case CLOCK_MONOTONIC:
- if (likely(gtod->clock.vclock_mode != VCLOCK_NONE))
- return do_monotonic(ts);
+ if (likely(gtod->clock.vclock_mode != VCLOCK_NONE)) {
+ do_monotonic(ts);
+ return 0;
+ }
break;
case CLOCK_REALTIME_COARSE:
- return do_realtime_coarse(ts);
+ do_realtime_coarse(ts);
+ return 0;
case CLOCK_MONOTONIC_COARSE:
- return do_monotonic_coarse(ts);
+ do_monotonic_coarse(ts);
+ return 0;
}

return vdso_fallback_gettime(clock, ts);
@@ -176,6 +176,44 @@ notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
int clock_gettime(clockid_t, struct timespec *)
__attribute__((weak, alias("__vdso_clock_gettime")));

+notrace int __vdso_clock_gettime_ns(clockid_t clock, u64 *t)
+{
+ /* This implementation is slow. It will be improved later. */
+
+ struct timespec ts;
+ int error;
+
+ switch (clock) {
+ case CLOCK_REALTIME:
+ if (likely(gtod->clock.vclock_mode != VCLOCK_NONE)) {
+ do_realtime(&ts);
+ *t = ts.tv_sec * NSEC_PER_SEC + ts.tv_nsec;
+ return 0;
+ }
+ break;
+ case CLOCK_MONOTONIC:
+ if (likely(gtod->clock.vclock_mode != VCLOCK_NONE)) {
+ do_monotonic(&ts);
+ *t = ts.tv_sec * NSEC_PER_SEC + ts.tv_nsec;
+ return 0;
+ }
+ break;
+ case CLOCK_REALTIME_COARSE:
+ do_realtime_coarse(&ts);
+ *t = ts.tv_sec * NSEC_PER_SEC + ts.tv_nsec;
+ return 0;
+ case CLOCK_MONOTONIC_COARSE:
+ do_monotonic_coarse(&ts);
+ *t = ts.tv_sec * NSEC_PER_SEC + ts.tv_nsec;
+ return 0;
+ }
+
+ error = vdso_fallback_gettime(clock, &ts);
+ if (!error)
+ *t = ts.tv_sec * NSEC_PER_SEC + ts.tv_nsec;
+ return error;
+}
+
notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
{
long ret;
diff --git a/arch/x86/vdso/vdso.lds.S b/arch/x86/vdso/vdso.lds.S
index b96b267..238f500 100644
--- a/arch/x86/vdso/vdso.lds.S
+++ b/arch/x86/vdso/vdso.lds.S
@@ -17,6 +17,10 @@
VERSION {
LINUX_2.6 {
global:
+ /*
+ * These are the original vsyscalls. They have weak symbols
+ * without the __vdso_ prefix for ABI compatibility.
+ */
clock_gettime;
__vdso_clock_gettime;
gettimeofday;
@@ -25,6 +29,9 @@ VERSION {
__vdso_getcpu;
time;
__vdso_time;
+
+ /* New vsyscalls are just plain functions. */
+ __vdso_clock_gettime_ns;
local: *;
};
}
--
1.7.7.4


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