From c8996c98f703b09afe77a1d247dae691c9849dc1 Mon Sep 17 00:00:00 2001 From: Jesper Dangaard Brouer Date: Tue, 9 Aug 2022 08:08:02 +0200 Subject: bpf: Add BPF-helper for accessing CLOCK_TAI 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. Use cases for such a BPF helper include functionalities such as Tx launch time (e.g. ETF and TAPRIO Qdiscs) and timestamping. Note: CLOCK_TAI is nothing new per se, only the NMI-safe variant of it is. Signed-off-by: Jesper Dangaard Brouer [Kurt: Wrote changelog and renamed helper] Signed-off-by: Kurt Kanzenbach Link: https://lore.kernel.org/r/20220809060803.5773-2-kurt@linutronix.de Signed-off-by: Alexei Starovoitov --- include/uapi/linux/bpf.h | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'include/uapi/linux') diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 534e33fb1029..7d1e2794d83e 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -5341,6 +5341,18 @@ union bpf_attr { * **-EACCES** if the SYN cookie is not valid. * * **-EPROTONOSUPPORT** if CONFIG_IPV6 is not builtin. + * + * 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), \ @@ -5551,6 +5563,7 @@ union bpf_attr { FN(tcp_raw_gen_syncookie_ipv6), \ FN(tcp_raw_check_syncookie_ipv4), \ FN(tcp_raw_check_syncookie_ipv6), \ + FN(ktime_get_tai_ns), \ /* */ /* integer value in 'imm' field of BPF_CALL instruction selects which helper -- cgit v1.2.3-59-g8ed1b