providers/darwin/process: fix error handling (#150)

* providers/darwin/process: fix error handling

kern_procargs was not returning an error when kern.procargs2 failed.
Then meant that you didn't get an error when the process no longer exists
or when you didn't have permissions to access the process.

For process.Info(), this especially affected builds running without CGO enabled.
When running with CGO there are other calls that will fail with "no such process"
or "operation not permitted" before we get to calling kern.procargs2, but without
CGO it goes directly to calling kern.procargs2. This resulted in Info() returning
a zero value types.ProcessInfo and no error.

Fixes #148

* system_test.go: Ignore EINVAL for process.Info()

Non-CGO build will return EINVAL when a process does not exist.

CHANGELOG.md

@@ -19,6 +19,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- On darwin without CGO `process.Info()` could fail, but would not return the error. [#150](https://github.com/elastic/go-sysinfo/pull/150)
+
 ## [1.9.0]
 
 ### Added

providers/darwin/process_darwin.go

@@ -23,9 +23,11 @@ package darwin
 import (
 	"bytes"
 	"encoding/binary"
+	"errors"
 	"fmt"
 	"os"
 	"strconv"
+	"syscall"
 	"time"
 
 	"golang.org/x/sys/unix"
@@ -178,7 +180,12 @@ var nullTerminator = []byte{0}
 func kern_procargs(pid int, p *process) error {
 	data, err := unix.SysctlRaw("kern.procargs2", pid)
 	if err != nil {
-		return nil
+		if errors.Is(err, syscall.EINVAL) {
+			// sysctl returns "invalid argument" for both "no such process"
+			// and "operation not permitted" errors.
+			return fmt.Errorf("no such process or operation not permitted: %w", err)
+		}
+		return err
 	}
 	buf := bytes.NewBuffer(data)
 

providers/darwin/process_darwin_test.go

@@ -21,8 +21,10 @@
 package darwin
 
 import (
+	"errors"
 	"os"
 	"os/exec"
+	"syscall"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -97,33 +99,44 @@ func TestProcessEnvironmentInternal(t *testing.T) {
 
 func TestProcesses(t *testing.T) {
 	var s darwinSystem
-	ps, err := s.Processes()
+	processes, err := s.Processes()
 	if err != nil {
 		t.Fatal(err)
 	}
 
-	pinfo, err := ps[0].Info()
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	if pinfo.PID == 0 {
-		t.Fatal("empty pid")
+	var count int
+	for _, proc := range processes {
+		processInfo, err := proc.Info()
+		switch {
+		// Ignore processes that no longer exist or that cannot be accessed.
+		case errors.Is(err, syscall.ESRCH),
+			errors.Is(err, syscall.EPERM),
+			errors.Is(err, syscall.EINVAL):
+			continue
+		case err != nil:
+			t.Fatalf("failed to get process info for PID=%d: %v", proc.PID(), err)
+		default:
+			count++
+		}
+
+		if processInfo.PID == 0 {
+			t.Fatalf("empty pid in %#v", processInfo)
+		}
+
+		if processInfo.Exe == "" {
+			t.Fatalf("empty exec in %#v", processInfo)
+		}
+
+		u, err := proc.User()
+		require.NoError(t, err)
+
+		require.NotEmpty(t, u.UID)
+		require.NotEmpty(t, u.EUID)
+		require.NotEmpty(t, u.SUID)
+		require.NotEmpty(t, u.GID)
+		require.NotEmpty(t, u.EGID)
+		require.NotEmpty(t, u.SGID)
 	}
 
-	if pinfo.Exe == "" {
-		t.Fatal("empty exec")
-	}
-
-	u, err := ps[0].User()
-	require.NoError(t, err)
-
-	require.NotEmpty(t, u.UID)
-	require.NotEmpty(t, u.EUID)
-	require.NotEmpty(t, u.SUID)
-	require.NotEmpty(t, u.GID)
-	require.NotEmpty(t, u.EGID)
-	require.NotEmpty(t, u.SGID)
-
-	t.Log(ps[0].Info())
+	assert.NotZero(t, count, "failed to get process info for any processes")
 }

system_test.go

@@ -292,14 +292,17 @@ func TestProcesses(t *testing.T) {
 	t.Log("Found", len(procs), "processes.")
 	for _, proc := range procs {
 		info, err := proc.Info()
-		if err != nil {
-			if errors.Is(err, fs.ErrPermission) || errors.Is(err, syscall.ESRCH) {
-				// The process may no longer exist by the time we try fetching
-				// additional information so ignore ESRCH (no such process).
-				continue
-			}
-			t.Fatal(err)
+		switch {
+		// Ignore processes that no longer exist or that cannot be accessed.
+		case errors.Is(err, syscall.ESRCH),
+			errors.Is(err, syscall.EPERM),
+			errors.Is(err, syscall.EINVAL),
+			errors.Is(err, fs.ErrPermission):
+			continue
+		case err != nil:
+			t.Fatalf("failed to get process info for PID=%d: %v", proc.PID(), err)
 		}
+
 		t.Logf("pid=%v name='%s' exe='%s' args=%+v ppid=%d cwd='%s' start_time=%v",
 			info.PID, info.Name, info.Exe, info.Args, info.PPID, info.CWD,
 			info.StartTime)