Add perf exporter (#1274)

Signed-off-by: Daniel Hodges <hodges.daniel.scott@gmail.com>

vendor/github.com/hodgesds/perf-utils/fs_utils.go

@@ -0,0 +1,102 @@
+// +build linux
+
+package perf
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strings"
+)
+
+const (
+	// DebugFS is the filesystem type for debugfs.
+	DebugFS = "debugfs"
+
+	// TraceFS is the filesystem type for tracefs.
+	TraceFS = "tracefs"
+
+	// ProcMounts is the mount point for file systems in procfs.
+	ProcMounts = "/proc/mounts"
+
+	// PerfMaxStack is the mount point for the max perf event size.
+	PerfMaxStack = "/proc/sys/kernel/perf_event_max_stack"
+
+	// PerfMaxContexts is a sysfs mount that contains the max perf contexts.
+	PerfMaxContexts = "/proc/sys/kernel/perf_event_max_contexts_per_stack"
+
+	// SyscallsDir is a constant of the default tracing event syscalls directory.
+	SyscallsDir = "/sys/kernel/debug/tracing/events/syscalls/"
+
+	// TracingDir is a constant of the default tracing directory.
+	TracingDir = "/sys/kernel/debug/tracing"
+)
+
+var (
+	// ErrNoMount is when there is no such mount.
+	ErrNoMount = fmt.Errorf("no such mount")
+)
+
+// TraceFSMount returns the first found mount point of a tracefs file system.
+func TraceFSMount() (string, error) {
+	mounts, err := GetFSMount(TraceFS)
+	if err != nil {
+		return "", err
+	}
+	if len(mounts) == 0 {
+		return "", ErrNoMount
+	}
+	return mounts[0], nil
+}
+
+// DebugFSMount returns the first found mount point of a debugfs file system.
+func DebugFSMount() (string, error) {
+	mounts, err := GetFSMount(DebugFS)
+	if err != nil {
+		return "", err
+	}
+	if len(mounts) == 0 {
+		return "", ErrNoMount
+	}
+	return mounts[0], nil
+}
+
+// GetFSMount is a helper function to get a mount file system type.
+func GetFSMount(mountType string) ([]string, error) {
+	mounts := []string{}
+	file, err := os.Open(ProcMounts)
+	if err != nil {
+		return mounts, err
+	}
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		mountInfo := strings.Split(scanner.Text(), " ")
+		if len(mountInfo) > 3 && mountInfo[2] == mountType {
+			mounts = append(mounts, mountInfo[1])
+		}
+	}
+	if err := scanner.Err(); err != nil {
+		return mounts, err
+	}
+
+	return mounts, file.Close()
+}
+
+// fileToStrings is a helper method that reads a line line by line and returns
+// a slice of strings.
+func fileToStrings(path string) ([]string, error) {
+	res := []string{}
+	f, err := os.Open(path)
+	if err != nil {
+		return res, err
+	}
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		res = append(res, scanner.Text())
+	}
+	if err := scanner.Err(); err != nil {
+		return res, err
+	}
+
+	return res, nil
+}