bpf: Add BPF-helper for accessing CLOCK_TAI
Commit 3dc6ffae2d
("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 <brouer@redhat.com>
[Kurt: Wrote changelog and renamed helper]
Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>
Link: https://lore.kernel.org/r/20220809060803.5773-2-kurt@linutronix.de
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
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@ -2349,6 +2349,7 @@ extern const struct bpf_func_proto bpf_get_numa_node_id_proto;
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extern const struct bpf_func_proto bpf_tail_call_proto;
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extern const struct bpf_func_proto bpf_ktime_get_ns_proto;
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extern const struct bpf_func_proto bpf_ktime_get_boot_ns_proto;
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extern const struct bpf_func_proto bpf_ktime_get_tai_ns_proto;
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extern const struct bpf_func_proto bpf_get_current_pid_tgid_proto;
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extern const struct bpf_func_proto bpf_get_current_uid_gid_proto;
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extern const struct bpf_func_proto bpf_get_current_comm_proto;
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@ -5341,6 +5341,18 @@ union bpf_attr {
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* **-EACCES** if the SYN cookie is not valid.
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*
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* **-EPROTONOSUPPORT** if CONFIG_IPV6 is not builtin.
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*
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* u64 bpf_ktime_get_tai_ns(void)
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* Description
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* A nonsettable system-wide clock derived from wall-clock time but
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* ignoring leap seconds. This clock does not experience
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* discontinuities and backwards jumps caused by NTP inserting leap
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* seconds as CLOCK_REALTIME does.
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*
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* See: **clock_gettime**\ (**CLOCK_TAI**)
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* Return
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* Current *ktime*.
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*
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*/
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#define __BPF_FUNC_MAPPER(FN) \
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FN(unspec), \
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@ -5551,6 +5563,7 @@ union bpf_attr {
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FN(tcp_raw_gen_syncookie_ipv6), \
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FN(tcp_raw_check_syncookie_ipv4), \
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FN(tcp_raw_check_syncookie_ipv6), \
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FN(ktime_get_tai_ns), \
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/* */
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/* integer value in 'imm' field of BPF_CALL instruction selects which helper
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@ -2623,6 +2623,7 @@ const struct bpf_func_proto bpf_get_numa_node_id_proto __weak;
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const struct bpf_func_proto bpf_ktime_get_ns_proto __weak;
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const struct bpf_func_proto bpf_ktime_get_boot_ns_proto __weak;
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const struct bpf_func_proto bpf_ktime_get_coarse_ns_proto __weak;
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const struct bpf_func_proto bpf_ktime_get_tai_ns_proto __weak;
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const struct bpf_func_proto bpf_get_current_pid_tgid_proto __weak;
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const struct bpf_func_proto bpf_get_current_uid_gid_proto __weak;
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@ -198,6 +198,18 @@ const struct bpf_func_proto bpf_ktime_get_coarse_ns_proto = {
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.ret_type = RET_INTEGER,
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};
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BPF_CALL_0(bpf_ktime_get_tai_ns)
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{
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/* NMI safe access to clock tai */
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return ktime_get_tai_fast_ns();
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}
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const struct bpf_func_proto bpf_ktime_get_tai_ns_proto = {
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.func = bpf_ktime_get_tai_ns,
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.gpl_only = false,
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.ret_type = RET_INTEGER,
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};
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BPF_CALL_0(bpf_get_current_pid_tgid)
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{
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struct task_struct *task = current;
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@ -1617,6 +1629,8 @@ bpf_base_func_proto(enum bpf_func_id func_id)
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return &bpf_ktime_get_ns_proto;
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case BPF_FUNC_ktime_get_boot_ns:
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return &bpf_ktime_get_boot_ns_proto;
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case BPF_FUNC_ktime_get_tai_ns:
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return &bpf_ktime_get_tai_ns_proto;
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case BPF_FUNC_ringbuf_output:
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return &bpf_ringbuf_output_proto;
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case BPF_FUNC_ringbuf_reserve:
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@ -5341,6 +5341,18 @@ union bpf_attr {
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* **-EACCES** if the SYN cookie is not valid.
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*
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* **-EPROTONOSUPPORT** if CONFIG_IPV6 is not builtin.
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*
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* u64 bpf_ktime_get_tai_ns(void)
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* Description
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* A nonsettable system-wide clock derived from wall-clock time but
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* ignoring leap seconds. This clock does not experience
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* discontinuities and backwards jumps caused by NTP inserting leap
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* seconds as CLOCK_REALTIME does.
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*
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* See: **clock_gettime**\ (**CLOCK_TAI**)
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* Return
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* Current *ktime*.
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*
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*/
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#define __BPF_FUNC_MAPPER(FN) \
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FN(unspec), \
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@ -5551,6 +5563,7 @@ union bpf_attr {
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FN(tcp_raw_gen_syncookie_ipv6), \
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FN(tcp_raw_check_syncookie_ipv4), \
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FN(tcp_raw_check_syncookie_ipv6), \
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FN(ktime_get_tai_ns), \
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/* */
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/* integer value in 'imm' field of BPF_CALL instruction selects which helper
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