From: Jesper Dangaard Brouer <brouer@xxxxxxxxxx>
Commit 3dc6ffae2da2 ("timekeeping: Introduce fast accessor to clock tai")
introduced a fast and NMI-safe accessor for CLOCK_TAI. Especially in time
sensitive networks (TSN), where all nodes are synchronized by Precision Time
Protocol (PTP), it's helpful to have the possibility to generate timestamps
based on CLOCK_TAI instead of CLOCK_MONOTONIC. With a BPF helper for TAI in
place, it becomes very convenient to correlate activity across different
machines in the network.
Signed-off-by: Jesper Dangaard Brouer <brouer@xxxxxxxxxx>
[Kurt: Wrote changelog and renamed helper]
Signed-off-by: Kurt Kanzenbach <kurt@xxxxxxxxxxxxx>
---
include/uapi/linux/bpf.h | 13 +++++++++++++
kernel/bpf/core.c | 1 +
kernel/bpf/helpers.c | 14 ++++++++++++++
tools/include/uapi/linux/bpf.h | 13 +++++++++++++
4 files changed, 41 insertions(+)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index f4009dbdf62d..5f240d5d30f6 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -5249,6 +5249,18 @@ union bpf_attr {
* Pointer to the underlying dynptr data, NULL if the dynptr is
* read-only, if the dynptr is invalid, or if the offset and length
* is out of bounds.
+ *
+ * u64 bpf_ktime_get_tai_ns(void)
+ * Description
+ * A nonsettable system-wide clock derived from wall-clock time but
+ * ignoring leap seconds. This clock does not experience
+ * discontinuities and backwards jumps caused by NTP inserting leap
+ * seconds as CLOCK_REALTIME does.
+ *
+ * See: **clock_gettime**\ (**CLOCK_TAI**)
+ * Return
+ * Current *ktime*.
+ *
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -5455,6 +5467,7 @@ union bpf_attr {
FN(dynptr_read), \
FN(dynptr_write), \
FN(dynptr_data), \
+ FN(ktime_get_tai_ns), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index e78cc5eea4a5..edfa716c3528 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -2641,6 +2641,7 @@ const struct bpf_func_proto bpf_get_numa_node_id_proto __weak;
const struct bpf_func_proto bpf_ktime_get_ns_proto __weak;
const struct bpf_func_proto bpf_ktime_get_boot_ns_proto __weak;
const struct bpf_func_proto bpf_ktime_get_coarse_ns_proto __weak;
+const struct bpf_func_proto bpf_ktime_get_tai_ns_proto __weak;
const struct bpf_func_proto bpf_get_current_pid_tgid_proto __weak;
const struct bpf_func_proto bpf_get_current_uid_gid_proto __weak;
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 225806a02efb..981b34d1e551 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -198,6 +198,18 @@ const struct bpf_func_proto bpf_ktime_get_coarse_ns_proto = {
.ret_type = RET_INTEGER,
};
+BPF_CALL_0(bpf_ktime_get_tai_ns)
+{
+ /* NMI safe access to clock tai */
+ return ktime_get_tai_fast_ns();
+}
+
+const struct bpf_func_proto bpf_ktime_get_tai_ns_proto = {
+ .func = bpf_ktime_get_tai_ns,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+};
+
BPF_CALL_0(bpf_get_current_pid_tgid)
{
struct task_struct *task = current;
@@ -1613,6 +1625,8 @@ bpf_base_func_proto(enum bpf_func_id func_id)
return &bpf_ktime_get_ns_proto;
case BPF_FUNC_ktime_get_boot_ns:
return &bpf_ktime_get_boot_ns_proto;
+ case BPF_FUNC_ktime_get_tai_ns:
+ return &bpf_ktime_get_tai_ns_proto;
case BPF_FUNC_ringbuf_output:
return &bpf_ringbuf_output_proto;
case BPF_FUNC_ringbuf_reserve:
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index f4009dbdf62d..5f240d5d30f6 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -5249,6 +5249,18 @@ union bpf_attr {
* Pointer to the underlying dynptr data, NULL if the dynptr is
* read-only, if the dynptr is invalid, or if the offset and length
* is out of bounds.
+ *
+ * u64 bpf_ktime_get_tai_ns(void)
+ * Description
+ * A nonsettable system-wide clock derived from wall-clock time but
+ * ignoring leap seconds. This clock does not experience
+ * discontinuities and backwards jumps caused by NTP inserting leap
+ * seconds as CLOCK_REALTIME does.
+ *
+ * See: **clock_gettime**\ (**CLOCK_TAI**)
+ * Return
+ * Current *ktime*.
+ *
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -5455,6 +5467,7 @@ union bpf_attr {
FN(dynptr_read), \
FN(dynptr_write), \
FN(dynptr_data), \
+ FN(ktime_get_tai_ns), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
--
2.30.2
