libbpf-tools: add funclatency

This is a port of BCC's funclatency.  Usage:

---------
Time functions and print latency as a histogram

Usage: funclatency [-h] [-m|-u] [-p PID] [-d DURATION] [ -i INTERVAL ]
                   [-T] FUNCTION
       Choices for FUNCTION: FUNCTION         (kprobe)
                             LIBRARY:FUNCTION (uprobe a library in -p PID)
                             :FUNCTION        (uprobe the binary of -p PID)

  -m, --milliseconds         Output in milliseconds
  -u, --microseconds         Output in microseconds
  -p, --pid=PID              Process ID to trace
  -d, --duration=DURATION    Duration to trace
  -i, --interval=INTERVAL    Summary interval in seconds
  -T, --timestamp            Print timestamp

  -?, --help                 Give this help list
      --usage                Give a short usage message
  -V, --version              Print program version

Mandatory or optional arguments to long options are also mandatory or optional
for any corresponding short options.

Examples:
  ./funclatency do_sys_open         # time the do_sys_open() kernel function
  ./funclatency -m do_nanosleep     # time do_nanosleep(), in milliseconds
  ./funclatency -u vfs_read         # time vfs_read(), in microseconds
  ./funclatency -p 181 vfs_read     # time process 181 only
  ./funclatency -p 181 c:read       # time the read() C library function
  ./funclatency -p 181 :foo         # time foo() from pid 181's userspace
  ./funclatency -i 2 -d 10 vfs_read # output every 2 seconds, for 10s
  ./funclatency -mTi 5 vfs_read     # output every 5 seconds, with timestamps

---------

It supports kprobes and has limited support for uprobes.  Currently, you
cannot uprobe a library unless you provide a PID.  It does not support
wildcard patterns.

Some of the functions for uprobes are useful for other programs, so I
put those in uprobe_helpers.{c,h}.

Signed-off-by: Barret Rhoden <[email protected]>

libbpf-tools/.gitignore

@@ -9,6 +9,7 @@
 /drsnoop
 /execsnoop
 /filelife
+/funclatency
 /hardirqs
 /llcstat
 /numamove

libbpf-tools/Makefile

@@ -26,6 +26,7 @@ APPS = \
 	drsnoop \
 	execsnoop \
 	filelife \
+	funclatency \
 	hardirqs \
 	llcstat \
 	numamove \
@@ -47,6 +48,7 @@ COMMON_OBJ = \
 	$(OUTPUT)/syscall_helpers.o \
 	$(OUTPUT)/errno_helpers.o \
 	$(OUTPUT)/map_helpers.o \
+	$(OUTPUT)/uprobe_helpers.o \
 	#
 
 .PHONY: all

libbpf-tools/funclatency.bpf.c

@@ -0,0 +1,71 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Google LLC. */
+#include "vmlinux.h"
+#include <bpf/bpf_core_read.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include "funclatency.h"
+#include "bits.bpf.h"
+
+const volatile pid_t targ_tgid;
+const volatile int units;
+
+/* key: pid.  value: start time */
+struct {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__uint(max_entries, MAX_PIDS);
+	__type(key, u32);
+	__type(value, u64);
+} starts SEC(".maps");
+
+__u32 hist[MAX_SLOTS];
+
+SEC("kprobe/dummy_kprobe")
+int BPF_KPROBE(dummy_kprobe)
+{
+	u64 id = bpf_get_current_pid_tgid();
+	u32 tgid = id >> 32;
+	u32 pid = id;
+	u64 nsec;
+
+	if (targ_tgid && targ_tgid != tgid)
+		return 0;
+	nsec = bpf_ktime_get_ns();
+	bpf_map_update_elem(&starts, &pid, &nsec, BPF_ANY);
+
+	return 0;
+}
+
+SEC("kretprobe/dummy_kretprobe")
+int BPF_KRETPROBE(dummy_kretprobe)
+{
+	u64 *start;
+	u64 nsec = bpf_ktime_get_ns();
+	u64 id = bpf_get_current_pid_tgid();
+	u32 pid = id;
+	u64 slot, delta;
+
+	start = bpf_map_lookup_elem(&starts, &pid);
+	if (!start)
+		return 0;
+
+	delta = nsec - *start;
+
+	switch (units) {
+	case USEC:
+		delta /= 1000;
+		break;
+	case MSEC:
+		delta /= 1000000;
+		break;
+	}
+
+	slot = log2l(delta);
+	if (slot >= MAX_SLOTS)
+		slot = MAX_SLOTS - 1;
+	__sync_fetch_and_add(&hist[slot], 1);
+
+	return 0;
+}
+
+char LICENSE[] SEC("license") = "GPL";