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";