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Subject[RFC 05/20] timerfd/timens: Take into account ns clock offsets
Date
From: Andrei Vagin <avagin@gmail.com>

Make timerfd respect timens offsets.
Provide two helpers timens_clock_to_host() timens_clock_from_host() that
are useful to wire up timens to different kernel subsystems.
Following patches will use timens_clock_from_host(), added here for
completeness.

Signed-off-by: Andrei Vagin <avagin@openvz.org>
Co-developed-by: Dmitry Safonov <dima@arista.com>
Signed-off-by: Dmitry Safonov <dima@arista.com>
---
fs/timerfd.c | 16 +++++++++++-----
include/linux/time_namespace.h | 11 +++++++++++
kernel/time_namespace.c | 39 +++++++++++++++++++++++++++++++++++++++
3 files changed, 61 insertions(+), 5 deletions(-)

diff --git a/fs/timerfd.c b/fs/timerfd.c
index d69ad801eb80..001ab7a0fd8b 100644
--- a/fs/timerfd.c
+++ b/fs/timerfd.c
@@ -26,6 +26,7 @@
#include <linux/syscalls.h>
#include <linux/compat.h>
#include <linux/rcupdate.h>
+#include <linux/time_namespace.h>

struct timerfd_ctx {
union {
@@ -433,22 +434,27 @@ SYSCALL_DEFINE2(timerfd_create, int, clockid, int, flags)
}

static int do_timerfd_settime(int ufd, int flags,
- const struct itimerspec64 *new,
+ struct itimerspec64 *new,
struct itimerspec64 *old)
{
struct fd f;
struct timerfd_ctx *ctx;
int ret;

- if ((flags & ~TFD_SETTIME_FLAGS) ||
- !itimerspec64_valid(new))
- return -EINVAL;
-
ret = timerfd_fget(ufd, &f);
if (ret)
return ret;
ctx = f.file->private_data;

+ if (flags & TFD_TIMER_ABSTIME)
+ timens_clock_to_host(ctx->clockid, &new->it_value);
+
+ if ((flags & ~TFD_SETTIME_FLAGS) ||
+ !itimerspec64_valid(new)) {
+ fdput(f);
+ return -EINVAL;
+ }
+
if (isalarm(ctx) && !capable(CAP_WAKE_ALARM)) {
fdput(f);
return -EPERM;
diff --git a/include/linux/time_namespace.h b/include/linux/time_namespace.h
index 4960c54f1b33..910711d1c39d 100644
--- a/include/linux/time_namespace.h
+++ b/include/linux/time_namespace.h
@@ -38,6 +38,9 @@ static inline void put_time_ns(struct time_namespace *ns)
kref_put(&ns->kref, free_time_ns);
}

+void timens_clock_to_host(int clockid, struct timespec64 *val);
+void timens_clock_from_host(int clockid, struct timespec64 *val);
+
#else
static inline void get_time_ns(struct time_namespace *ns)
{
@@ -56,6 +59,14 @@ static inline struct time_namespace *copy_time_ns(unsigned long flags,
return old_ns;
}

+static inline void timens_clock_to_host(int clockid, struct timespec64 *val)
+{
+}
+
+static inline void timens_clock_from_host(int clockid, struct timespec64 *val)
+{
+}
+
#endif

#endif /* _LINUX_TIMENS_H */
diff --git a/kernel/time_namespace.c b/kernel/time_namespace.c
index a985529754b4..f96871cb8124 100644
--- a/kernel/time_namespace.c
+++ b/kernel/time_namespace.c
@@ -154,6 +154,45 @@ static struct user_namespace *timens_owner(struct ns_common *ns)
return to_time_ns(ns)->user_ns;
}

+static void clock_timens_fixup(int clockid, struct timespec64 *val, bool to_ns)
+{
+ struct timens_offsets *ns_offsets = current->nsproxy->time_ns->offsets;
+ struct timespec64 *offsets = NULL;
+
+ if (!ns_offsets)
+ return;
+
+ if (val->tv_sec == 0 && val->tv_nsec == 0)
+ return;
+
+ switch (clockid) {
+ case CLOCK_MONOTONIC:
+ offsets = &ns_offsets->monotonic_time_offset;
+ break;
+ case CLOCK_BOOTTIME:
+ offsets = &ns_offsets->monotonic_boottime_offset;
+ break;
+ }
+
+ if (!offsets)
+ return;
+
+ if (to_ns)
+ *val = timespec64_add(*val, *offsets);
+ else
+ *val = timespec64_sub(*val, *offsets);
+}
+
+void timens_clock_to_host(int clockid, struct timespec64 *val)
+{
+ clock_timens_fixup(clockid, val, false);
+}
+
+void timens_clock_from_host(int clockid, struct timespec64 *val)
+{
+ clock_timens_fixup(clockid, val, true);
+}
+
const struct proc_ns_operations timens_operations = {
.name = "time",
.type = CLONE_NEWTIME,
--
2.13.6
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