perf ftrace: Add -b/--use-bpf option for latency subcommand

The -b/--use-bpf option is to use BPF to get latency info of kernel
functions.  It'd have better performance impact and I observed that
latency of same function is smaller than before when using BPF.

Committer testing:

  # strace -e bpf perf ftrace latency -b -T __handle_mm_fault -a sleep 1
  bpf(BPF_PROG_LOAD, {prog_type=BPF_PROG_TYPE_SOCKET_FILTER, insn_cnt=2, insns=0x7fff51914e00, license="GPL", log_level=0, log_size=0, log_buf=NULL, kern_version=KERNEL_VERSION(0, 0, 0), prog_flags=0, prog_name="", prog_ifindex=0, expected_attach_type=BPF_CGROUP_INET_INGRESS, prog_btf_fd=0, func_info_rec_size=0, func_info=NULL, func_info_cnt=0, line_info_rec_size=0, line_info=NULL, line_info_cnt=0, attach_btf_id=0, attach_prog_fd=0}, 128) = 3
  bpf(BPF_BTF_LOAD, {btf="\237\353\1\0\30\0\0\0\0\0\0\0\20\0\0\0\20\0\0\0\5\0\0\0\1\0\0\0\0\0\0\1"..., btf_log_buf=NULL, btf_size=45, btf_log_size=0, btf_log_level=0}, 128) = 3
  bpf(BPF_BTF_LOAD, {btf="\237\353\1\0\30\0\0\0\0\0\0\0000\0\0\0000\0\0\0\t\0\0\0\1\0\0\0\0\0\0\1"..., btf_log_buf=NULL, btf_size=81, btf_log_size=0, btf_log_level=0}, 128) = 3
  bpf(BPF_BTF_LOAD, {btf="\237\353\1\0\30\0\0\0\0\0\0\08\0\0\08\0\0\0\t\0\0\0\0\0\0\0\0\0\0\1"..., btf_log_buf=NULL, btf_size=89, btf_log_size=0, btf_log_level=0}, 128) = 3
  bpf(BPF_BTF_LOAD, {btf="\237\353\1\0\30\0\0\0\0\0\0\0\f\0\0\0\f\0\0\0\7\0\0\0\1\0\0\0\0\0\0\20"..., btf_log_buf=NULL, btf_size=43, btf_log_size=0, btf_log_level=0}, 128) = 3
  bpf(BPF_BTF_LOAD, {btf="\237\353\1\0\30\0\0\0\0\0\0\0000\0\0\0000\0\0\0\t\0\0\0\1\0\0\0\0\0\0\1"..., btf_log_buf=NULL, btf_size=81, btf_log_size=0, btf_log_level=0}, 128) = 3
  bpf(BPF_BTF_LOAD, {btf="\237\353\1\0\30\0\0\0\0\0\0\0000\0\0\0000\0\0\0\5\0\0\0\0\0\0\0\0\0\0\1"..., btf_log_buf=NULL, btf_size=77, btf_log_size=0, btf_log_level=0}, 128) = -1 EINVAL (Invalid argument)
  bpf(BPF_BTF_LOAD, {btf="\237\353\1\0\30\0\0\0\0\0\0\0\350\2\0\0\350\2\0\0\353\2\0\0\0\0\0\0\0\0\0\2"..., btf_log_buf=NULL, btf_size=1515, btf_log_size=0, btf_log_level=0}, 128) = 3
  bpf(BPF_MAP_CREATE, {map_type=BPF_MAP_TYPE_ARRAY, key_size=4, value_size=32, max_entries=1, map_flags=0, inner_map_fd=0, map_name="", map_ifindex=0, btf_fd=0, btf_key_type_id=0, btf_value_type_id=0, btf_vmlinux_value_type_id=0}, 128) = 4
  bpf(BPF_PROG_LOAD, {prog_type=BPF_PROG_TYPE_SOCKET_FILTER, insn_cnt=5, insns=0x7fff51914c30, license="GPL", log_level=0, log_size=0, log_buf=NULL, kern_version=KERNEL_VERSION(0, 0, 0), prog_flags=0, prog_name="", prog_ifindex=0, expected_attach_type=BPF_CGROUP_INET_INGRESS, prog_btf_fd=0, func_info_rec_size=0, func_info=NULL, func_info_cnt=0, line_info_rec_size=0, line_info=NULL, line_info_cnt=0, attach_btf_id=0, attach_prog_fd=0}, 128) = 5
  bpf(BPF_MAP_CREATE, {map_type=BPF_MAP_TYPE_ARRAY, key_size=4, value_size=4, max_entries=1, map_flags=BPF_F_MMAPABLE, inner_map_fd=0, map_name="", map_ifindex=0, btf_fd=0, btf_key_type_id=0, btf_value_type_id=0, btf_vmlinux_value_type_id=0}, 128) = 4
  bpf(BPF_PROG_LOAD, {prog_type=BPF_PROG_TYPE_SOCKET_FILTER, insn_cnt=2, insns=0x7fff51914a80, license="GPL", log_level=0, log_size=0, log_buf=NULL, kern_version=KERNEL_VERSION(0, 0, 0), prog_flags=0, prog_name="test", prog_ifindex=0, expected_attach_type=BPF_CGROUP_INET_INGRESS, prog_btf_fd=0, func_info_rec_size=0, func_info=NULL, func_info_cnt=0, line_info_rec_size=0, line_info=NULL, line_info_cnt=0, attach_btf_id=0, attach_prog_fd=0}, 128) = 4
  bpf(BPF_MAP_CREATE, {map_type=BPF_MAP_TYPE_HASH, key_size=8, value_size=8, max_entries=10000, map_flags=0, inner_map_fd=0, map_name="functime", map_ifindex=0, btf_fd=3, btf_key_type_id=0, btf_value_type_id=0, btf_vmlinux_value_type_id=0}, 128) = 4
  bpf(BPF_MAP_CREATE, {map_type=BPF_MAP_TYPE_HASH, key_size=4, value_size=1, max_entries=1, map_flags=0, inner_map_fd=0, map_name="cpu_filter", map_ifindex=0, btf_fd=3, btf_key_type_id=0, btf_value_type_id=0, btf_vmlinux_value_type_id=0}, 128) = 5
  bpf(BPF_MAP_CREATE, {map_type=BPF_MAP_TYPE_HASH, key_size=4, value_size=1, max_entries=1, map_flags=0, inner_map_fd=0, map_name="task_filter", map_ifindex=0, btf_fd=3, btf_key_type_id=0, btf_value_type_id=0, btf_vmlinux_value_type_id=0}, 128) = 7
  bpf(BPF_MAP_CREATE, {map_type=BPF_MAP_TYPE_PERCPU_ARRAY, key_size=4, value_size=8, max_entries=22, map_flags=0, inner_map_fd=0, map_name="latency", map_ifindex=0, btf_fd=3, btf_key_type_id=0, btf_value_type_id=0, btf_vmlinux_value_type_id=0}, 128) = 8
  bpf(BPF_MAP_CREATE, {map_type=BPF_MAP_TYPE_ARRAY, key_size=4, value_size=4, max_entries=1, map_flags=BPF_F_MMAPABLE, inner_map_fd=0, map_name="func_lat.bss", map_ifindex=0, btf_fd=3, btf_key_type_id=0, btf_value_type_id=30, btf_vmlinux_value_type_id=0}, 128) = 9
  bpf(BPF_MAP_UPDATE_ELEM, {map_fd=9, key=0x7fff51914c40, value=0x7f6e99be2000, flags=BPF_ANY}, 128) = 0
  bpf(BPF_PROG_LOAD, {prog_type=BPF_PROG_TYPE_KPROBE, insn_cnt=18, insns=0x11e4160, license="", log_level=0, log_size=0, log_buf=NULL, kern_version=KERNEL_VERSION(5, 14, 16), prog_flags=0, prog_name="func_begin", prog_ifindex=0, expected_attach_type=BPF_CGROUP_INET_INGRESS, prog_btf_fd=3, func_info_rec_size=8, func_info=0x11dfc50, func_info_cnt=1, line_info_rec_size=16, line_info=0x11e04c0, line_info_cnt=9, attach_btf_id=0, attach_prog_fd=0}, 128) = 10
  bpf(BPF_PROG_LOAD, {prog_type=BPF_PROG_TYPE_KPROBE, insn_cnt=99, insns=0x11ded70, license="", log_level=0, log_size=0, log_buf=NULL, kern_version=KERNEL_VERSION(5, 14, 16), prog_flags=0, prog_name="func_end", prog_ifindex=0, expected_attach_type=BPF_CGROUP_INET_INGRESS, prog_btf_fd=3, func_info_rec_size=8, func_info=0x11dfc70, func_info_cnt=1, line_info_rec_size=16, line_info=0x11f6e10, line_info_cnt=20, attach_btf_id=0, attach_prog_fd=0}, 128) = 11
  bpf(BPF_PROG_LOAD, {prog_type=BPF_PROG_TYPE_TRACEPOINT, insn_cnt=2, insns=0x7fff51914a80, license="GPL", log_level=0, log_size=0, log_buf=NULL, kern_version=KERNEL_VERSION(0, 0, 0), prog_flags=0, prog_name="", prog_ifindex=0, expected_attach_type=BPF_CGROUP_INET_INGRESS, prog_btf_fd=0, func_info_rec_size=0, func_info=NULL, func_info_cnt=0, line_info_rec_size=0, line_info=NULL, line_info_cnt=0, attach_btf_id=0, attach_prog_fd=0}, 128) = 13
  bpf(BPF_LINK_CREATE, {link_create={prog_fd=13, target_fd=-1, attach_type=0x29 /* BPF_??? */, flags=0}}, 128) = -1 EINVAL (Invalid argument)
  --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=1699992, si_uid=0, si_status=0, si_utime=0, si_stime=0} ---
  bpf(BPF_MAP_LOOKUP_ELEM, {map_fd=8, key=0x7fff51914f84, value=0x11f6fa0, flags=BPF_ANY}, 128) = 0
  bpf(BPF_MAP_LOOKUP_ELEM, {map_fd=8, key=0x7fff51914f84, value=0x11f6fa0, flags=BPF_ANY}, 128) = 0
  bpf(BPF_MAP_LOOKUP_ELEM, {map_fd=8, key=0x7fff51914f84, value=0x11f6fa0, flags=BPF_ANY}, 128) = 0
  bpf(BPF_MAP_LOOKUP_ELEM, {map_fd=8, key=0x7fff51914f84, value=0x11f6fa0, flags=BPF_ANY}, 128) = 0
  bpf(BPF_MAP_LOOKUP_ELEM, {map_fd=8, key=0x7fff51914f84, value=0x11f6fa0, flags=BPF_ANY}, 128) = 0
  bpf(BPF_MAP_LOOKUP_ELEM, {map_fd=8, key=0x7fff51914f84, value=0x11f6fa0, flags=BPF_ANY}, 128) = 0
  bpf(BPF_MAP_LOOKUP_ELEM, {map_fd=8, key=0x7fff51914f84, value=0x11f6fa0, flags=BPF_ANY}, 128) = 0
  bpf(BPF_MAP_LOOKUP_ELEM, {map_fd=8, key=0x7fff51914f84, value=0x11f6fa0, flags=BPF_ANY}, 128) = 0
  bpf(BPF_MAP_LOOKUP_ELEM, {map_fd=8, key=0x7fff51914f84, value=0x11f6fa0, flags=BPF_ANY}, 128) = 0
  bpf(BPF_MAP_LOOKUP_ELEM, {map_fd=8, key=0x7fff51914f84, value=0x11f6fa0, flags=BPF_ANY}, 128) = 0
  bpf(BPF_MAP_LOOKUP_ELEM, {map_fd=8, key=0x7fff51914f84, value=0x11f6fa0, flags=BPF_ANY}, 128) = 0
  bpf(BPF_MAP_LOOKUP_ELEM, {map_fd=8, key=0x7fff51914f84, value=0x11f6fa0, flags=BPF_ANY}, 128) = 0
  bpf(BPF_MAP_LOOKUP_ELEM, {map_fd=8, key=0x7fff51914f84, value=0x11f6fa0, flags=BPF_ANY}, 128) = 0
  bpf(BPF_MAP_LOOKUP_ELEM, {map_fd=8, key=0x7fff51914f84, value=0x11f6fa0, flags=BPF_ANY}, 128) = 0
  bpf(BPF_MAP_LOOKUP_ELEM, {map_fd=8, key=0x7fff51914f84, value=0x11f6fa0, flags=BPF_ANY}, 128) = 0
  bpf(BPF_MAP_LOOKUP_ELEM, {map_fd=8, key=0x7fff51914f84, value=0x11f6fa0, flags=BPF_ANY}, 128) = 0
  bpf(BPF_MAP_LOOKUP_ELEM, {map_fd=8, key=0x7fff51914f84, value=0x11f6fa0, flags=BPF_ANY}, 128) = 0
  bpf(BPF_MAP_LOOKUP_ELEM, {map_fd=8, key=0x7fff51914f84, value=0x11f6fa0, flags=BPF_ANY}, 128) = 0
  bpf(BPF_MAP_LOOKUP_ELEM, {map_fd=8, key=0x7fff51914f84, value=0x11f6fa0, flags=BPF_ANY}, 128) = 0
  bpf(BPF_MAP_LOOKUP_ELEM, {map_fd=8, key=0x7fff51914f84, value=0x11f6fa0, flags=BPF_ANY}, 128) = 0
  bpf(BPF_MAP_LOOKUP_ELEM, {map_fd=8, key=0x7fff51914f84, value=0x11f6fa0, flags=BPF_ANY}, 128) = 0
  bpf(BPF_MAP_LOOKUP_ELEM, {map_fd=8, key=0x7fff51914f84, value=0x11f6fa0, flags=BPF_ANY}, 128) = 0
  #   DURATION     |      COUNT | GRAPH                                          |
       0 - 1    us |         52 | ###################                            |
       1 - 2    us |         36 | #############                                  |
       2 - 4    us |         24 | #########                                      |
       4 - 8    us |          7 | ##                                             |
       8 - 16   us |          1 |                                                |
      16 - 32   us |          0 |                                                |
      32 - 64   us |          0 |                                                |
      64 - 128  us |          0 |                                                |
     128 - 256  us |          0 |                                                |
     256 - 512  us |          0 |                                                |
     512 - 1024 us |          0 |                                                |
       1 - 2    ms |          0 |                                                |
       2 - 4    ms |          0 |                                                |
       4 - 8    ms |          0 |                                                |
       8 - 16   ms |          0 |                                                |
      16 - 32   ms |          0 |                                                |
      32 - 64   ms |          0 |                                                |
      64 - 128  ms |          0 |                                                |
     128 - 256  ms |          0 |                                                |
     256 - 512  ms |          0 |                                                |
     512 - 1024 ms |          0 |                                                |
       1 - ...   s |          0 |                                                |
  +++ exited with 0 +++
  #

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Athira Jajeev <atrajeev@linux.vnet.ibm.com>
Cc: Changbin Du <changbin.du@gmail.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Stephane Eranian <eranian@google.com>
Link: https://lore.kernel.org/r/20211215185154.360314-5-namhyung@kernel.org
[ Add missing util/cpumap.h include and removed unused 'fd' variable ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

4 files changed, 287 insertions, 0 deletions

diff --git a/tools/perf/util/Build b/tools/perf/util/Build
index 2e5bfbb69960..294b12430d73 100644
--- a/tools/perf/util/Build
+++ b/tools/perf/util/Build
@@ -144,6 +144,7 @@ perf-$(CONFIG_LIBBPF) += bpf-loader.o
 perf-$(CONFIG_LIBBPF) += bpf_map.o
 perf-$(CONFIG_PERF_BPF_SKEL) += bpf_counter.o
 perf-$(CONFIG_PERF_BPF_SKEL) += bpf_counter_cgroup.o
+perf-$(CONFIG_PERF_BPF_SKEL) += bpf_ftrace.o
 perf-$(CONFIG_BPF_PROLOGUE) += bpf-prologue.o
 perf-$(CONFIG_LIBELF) += symbol-elf.o
 perf-$(CONFIG_LIBELF) += probe-file.o
diff --git a/tools/perf/util/bpf_ftrace.c b/tools/perf/util/bpf_ftrace.c
new file mode 100644
index 000000000000..ec4e2f5a2fc4
--- /dev/null
+++ b/tools/perf/util/bpf_ftrace.c
@@ -0,0 +1,112 @@
+#include <stdio.h>
+#include <fcntl.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+#include <linux/err.h>
+
+#include "util/ftrace.h"
+#include "util/cpumap.h"
+#include "util/debug.h"
+#include "util/bpf_counter.h"
+
+#include "util/bpf_skel/func_latency.skel.h"
+
+static struct func_latency_bpf *skel;
+
+int perf_ftrace__latency_prepare_bpf(struct perf_ftrace *ftrace)
+{
+	int err;
+	struct filter_entry *func;
+
+	if (!list_is_singular(&ftrace->filters)) {
+		pr_err("ERROR: %s target function(s).\n",
+		       list_empty(&ftrace->filters) ? "No" : "Too many");
+		return -1;
+	}
+
+	func = list_first_entry(&ftrace->filters, struct filter_entry, list);
+
+	skel = func_latency_bpf__open();
+	if (!skel) {
+		pr_err("Failed to open func latency skeleton\n");
+		return -1;
+	}
+
+	set_max_rlimit();
+
+	err = func_latency_bpf__load(skel);
+	if (err) {
+		pr_err("Failed to load func latency skeleton\n");
+		goto out;
+	}
+
+	skel->links.func_begin = bpf_program__attach_kprobe(skel->progs.func_begin,
+							    false, func->name);
+	if (IS_ERR(skel->links.func_begin)) {
+		pr_err("Failed to attach fentry program\n");
+		err = PTR_ERR(skel->links.func_begin);
+		goto out;
+	}
+
+	skel->links.func_end = bpf_program__attach_kprobe(skel->progs.func_end,
+							  true, func->name);
+	if (IS_ERR(skel->links.func_end)) {
+		pr_err("Failed to attach fexit program\n");
+		err = PTR_ERR(skel->links.func_end);
+		goto out;
+	}
+
+	/* XXX: we don't actually use this fd - just for poll() */
+	return open("/dev/null", O_RDONLY);
+
+out:
+	return err;
+}
+
+int perf_ftrace__latency_start_bpf(struct perf_ftrace *ftrace __maybe_unused)
+{
+	skel->bss->enabled = 1;
+	return 0;
+}
+
+int perf_ftrace__latency_stop_bpf(struct perf_ftrace *ftrace __maybe_unused)
+{
+	skel->bss->enabled = 0;
+	return 0;
+}
+
+int perf_ftrace__latency_read_bpf(struct perf_ftrace *ftrace __maybe_unused,
+				  int buckets[])
+{
+	int i, fd, err;
+	u32 idx;
+	u64 *hist;
+	int ncpus = cpu__max_cpu();
+
+	fd = bpf_map__fd(skel->maps.latency);
+
+	hist = calloc(ncpus, sizeof(*hist));
+	if (hist == NULL)
+		return -ENOMEM;
+
+	for (idx = 0; idx < NUM_BUCKET; idx++) {
+		err = bpf_map_lookup_elem(fd, &idx, hist);
+		if (err) {
+			buckets[idx] = 0;
+			continue;
+		}
+
+		for (i = 0; i < ncpus; i++)
+			buckets[idx] += hist[i];
+	}
+
+	free(hist);
+	return 0;
+}
+
+int perf_ftrace__latency_cleanup_bpf(struct perf_ftrace *ftrace __maybe_unused)
+{
+	func_latency_bpf__destroy(skel);
+	return 0;
+}
diff --git a/tools/perf/util/bpf_skel/func_latency.bpf.c b/tools/perf/util/bpf_skel/func_latency.bpf.c
new file mode 100644
index 000000000000..ccd96b09fc42
--- /dev/null
+++ b/tools/perf/util/bpf_skel/func_latency.bpf.c
@@ -0,0 +1,93 @@
+// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+// Copyright (c) 2021 Google
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+// This should be in sync with "util/ftrace.h"
+#define NUM_BUCKET  22
+
+struct {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__uint(key_size, sizeof(__u64));
+	__uint(value_size, sizeof(__u64));
+	__uint(max_entries, 10000);
+} functime SEC(".maps");
+
+struct {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__uint(key_size, sizeof(__u32));
+	__uint(value_size, sizeof(__u8));
+	__uint(max_entries, 1);
+} cpu_filter SEC(".maps");
+
+struct {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__uint(key_size, sizeof(__u32));
+	__uint(value_size, sizeof(__u8));
+	__uint(max_entries, 1);
+} task_filter SEC(".maps");
+
+struct {
+	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
+	__uint(key_size, sizeof(__u32));
+	__uint(value_size, sizeof(__u64));
+	__uint(max_entries, NUM_BUCKET);
+} latency SEC(".maps");
+
+
+int enabled = 0;
+
+SEC("kprobe/func")
+int BPF_PROG(func_begin)
+{
+	__u64 key, now;
+
+	if (!enabled)
+		return 0;
+
+	key = bpf_get_current_pid_tgid();
+	now = bpf_ktime_get_ns();
+
+	// overwrite timestamp for nested functions
+	bpf_map_update_elem(&functime, &key, &now, BPF_ANY);
+	return 0;
+}
+
+SEC("kretprobe/func")
+int BPF_PROG(func_end)
+{
+	__u64 tid;
+	__u64 *start;
+
+	if (!enabled)
+		return 0;
+
+	tid = bpf_get_current_pid_tgid();
+
+	start = bpf_map_lookup_elem(&functime, &tid);
+	if (start) {
+		__s64 delta = bpf_ktime_get_ns() - *start;
+		__u32 key;
+		__u64 *hist;
+
+		bpf_map_delete_elem(&functime, &tid);
+
+		if (delta < 0)
+			return 0;
+
+		// calculate index using delta in usec
+		for (key = 0; key < (NUM_BUCKET - 1); key++) {
+			if (delta < ((1000UL) << key))
+				break;
+		}
+
+		hist = bpf_map_lookup_elem(&latency, &key);
+		if (!hist)
+			return 0;
+
+		*hist += 1;
+	}
+
+	return 0;
+}
diff --git a/tools/perf/util/ftrace.h b/tools/perf/util/ftrace.h
new file mode 100644
index 000000000000..887f68a185f7
--- /dev/null
+++ b/tools/perf/util/ftrace.h
@@ -0,0 +1,81 @@
+#ifndef __PERF_FTRACE_H__
+#define __PERF_FTRACE_H__
+
+#include <linux/list.h>
+
+#include "target.h"
+
+struct evlist;
+
+struct perf_ftrace {
+	struct evlist		*evlist;
+	struct target		target;
+	const char		*tracer;
+	struct list_head	filters;
+	struct list_head	notrace;
+	struct list_head	graph_funcs;
+	struct list_head	nograph_funcs;
+	unsigned long		percpu_buffer_size;
+	bool			inherit;
+	int			graph_depth;
+	int			func_stack_trace;
+	int			func_irq_info;
+	int			graph_nosleep_time;
+	int			graph_noirqs;
+	int			graph_verbose;
+	int			graph_thresh;
+	unsigned int		initial_delay;
+};
+
+struct filter_entry {
+	struct list_head	list;
+	char			name[];
+};
+
+#define NUM_BUCKET  22  /* 20 + 2 (for outliers in both direction) */
+
+#ifdef HAVE_BPF_SKEL
+
+int perf_ftrace__latency_prepare_bpf(struct perf_ftrace *ftrace);
+int perf_ftrace__latency_start_bpf(struct perf_ftrace *ftrace);
+int perf_ftrace__latency_stop_bpf(struct perf_ftrace *ftrace);
+int perf_ftrace__latency_read_bpf(struct perf_ftrace *ftrace,
+				  int buckets[]);
+int perf_ftrace__latency_cleanup_bpf(struct perf_ftrace *ftrace);
+
+#else  /* !HAVE_BPF_SKEL */
+
+static inline int
+perf_ftrace__latency_prepare_bpf(struct perf_ftrace *ftrace __maybe_unused)
+{
+	return -1;
+}
+
+static inline int
+perf_ftrace__latency_start_bpf(struct perf_ftrace *ftrace __maybe_unused)
+{
+	return -1;
+}
+
+static inline int
+perf_ftrace__latency_stop_bpf(struct perf_ftrace *ftrace __maybe_unused)
+{
+	return -1;
+}
+
+static inline int
+perf_ftrace__latency_read_bpf(struct perf_ftrace *ftrace __maybe_unused,
+			      int buckets[] __maybe_unused)
+{
+	return -1;
+}
+
+static inline int
+perf_ftrace__latency_cleanup_bpf(struct perf_ftrace *ftrace __maybe_unused)
+{
+	return -1;
+}
+
+#endif  /* HAVE_BPF_SKEL */
+
+#endif  /* __PERF_FTRACE_H__ */