linux, exec: adds capabilities detection - prints a message when runn…

…ing pyroscope exec with no proper capabilities

pkg/exec/cli.go

@@ -7,7 +7,6 @@ import (
 	"os/exec"
 	"os/user"
 	"path"
-	"runtime"
 	"strconv"
 	"strings"
 	"syscall"
@@ -37,13 +36,12 @@ func Cli(cfg *config.Config, args []string) error {
 			supportedSpies := spy.SupportedExecSpies()
 			suggestedCommand := fmt.Sprintf("pyroscope exec -spy-name %s %s", supportedSpies[0], strings.Join(args, " "))
 			return fmt.Errorf(
-				"could not automatically find a spy for program \"%s\". Pass spy name via %s argument, for example: \n  %s\n\nAvailable spies are: %s\n%s\nIf you believe this is a mistake, please submit an issue at %s",
+				"could not automatically find a spy for program \"%s\". Pass spy name via %s argument, for example: \n  %s\n\nAvailable spies are: %s\nIf you believe this is a mistake, please submit an issue at %s",
 				baseName,
 				color.YellowString("-spy-name"),
 				color.YellowString(suggestedCommand),
 				strings.Join(supportedSpies, ","),
-				armMessage(),
-				color.BlueString("https://github.com/pyroscope-io/pyroscope/issues"),
+				color.GreenString("https://github.com/pyroscope-io/pyroscope/issues"),
 			)
 		}
 	}
@@ -57,7 +55,7 @@ func Cli(cfg *config.Config, args []string) error {
 	if cfg.Exec.ApplicationName == "" {
 		logrus.Infof("we recommend specifying application name via %s flag or env variable %s", color.YellowString("-application-name"), color.YellowString("PYROSCOPE_APPLICATION_NAME"))
 		cfg.Exec.ApplicationName = spyName + "." + names.GetRandomName(generateSeed(args))
-		logrus.Infof("for now we chose the name for you and it's \"%s\"", color.BlueString(cfg.Exec.ApplicationName))
+		logrus.Infof("for now we chose the name for you and it's \"%s\"", color.GreenString(cfg.Exec.ApplicationName))
 	}
 
 	logrus.WithFields(logrus.Fields{
@@ -143,22 +141,17 @@ func waitForProcessToExit(cmd *exec.Cmd) {
 
 func performChecks(spyName string) error {
 	if spyName == "gospy" {
-		return fmt.Errorf("gospy can not profile other processes. See our documentation on using gospy: %s", color.BlueString("https://pyroscope.io/docs/"))
+		return fmt.Errorf("gospy can not profile other processes. See our documentation on using gospy: %s", color.GreenString("https://pyroscope.io/docs/"))
 	}
 
-	if runtime.GOOS == "darwin" {
-		if !isRoot() {
-			logrus.Fatal("on macOS you're required to run the agent with sudo")
-		}
-	}
+	performOSChecks()
 
 	if !stringsContains(spy.SupportedSpies, spyName) {
 		supportedSpies := spy.SupportedExecSpies()
 		return fmt.Errorf(
-			"Spy \"%s\" is not supported. Available spies are: %s\n%s",
-			color.BlueString(spyName),
+			"Spy \"%s\" is not supported. Available spies are: %s\n",
+			color.GreenString(spyName),
 			strings.Join(supportedSpies, ","),
-			armMessage(),
 		)
 	}
 
@@ -179,13 +172,6 @@ func isRoot() bool {
 	return err == nil && u.Username == "root"
 }
 
-func armMessage() string {
-	if runtime.GOARCH == "arm64" {
-		return "Note that rbspy is not available on arm64 platform"
-	}
-	return ""
-}
-
 func generateSeed(args []string) string {
 	path, err := os.Getwd()
 	if err != nil {

pkg/exec/cli_darwin.go

@@ -0,0 +1,13 @@
+// +build darwin
+
+package exec
+
+import (
+	"github.com/sirupsen/logrus"
+)
+
+func performOSChecks() {
+	if !isRoot() {
+		logrus.Fatal("on macOS you're required to run the agent with sudo")
+	}
+}

pkg/exec/cli_linux.go

@@ -0,0 +1,32 @@
+// +build linux
+
+package exec
+
+import (
+	"github.com/pyroscope-io/pyroscope/pkg/util/caps"
+	"github.com/sirupsen/logrus"
+)
+
+func performOSChecks() {
+	if !hasSysPtraceCap() {
+		logrus.Fatal("if you're running pyroscope in a Docker container, add --cap-add=sys_ptrace. See our Docker Guide for more information: https://pyroscope.io/docs/docker-guide")
+	}
+}
+
+// See linux source code: https://github.com/torvalds/linux/blob/6ad4bf6ea1609fb539a62f10fca87ddbd53a0315/include/uapi/linux/capability.h#L235
+const CAP_SYS_PTRACE = 19
+
+func hasSysPtraceCap() bool {
+	c, err := caps.Get()
+	if err != nil {
+		logrus.Warn("Could not read capabilities. Please submit an issue at https://github.com/pyroscope-io/pyroscope/issues")
+		return true // I don't know of cases when this would happen, but if it does I'd rather give this program a chance
+	}
+
+	if c.Inheritable() == 0 {
+		logrus.Warn("Could not read capabilities. Please submit an issue at https://github.com/pyroscope-io/pyroscope/issues")
+		return true // I don't know of cases when this would happen, but if it does I'd rather give this program a chance
+	}
+
+	return c.Has(CAP_SYS_PTRACE)
+}

pkg/util/caps/capabilities.go

@@ -0,0 +1,58 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build linux
+
+// this is copied from https://golang.org/src/syscall/exec_linux_test.go
+
+package caps
+
+import (
+	"fmt"
+	"syscall"
+	"unsafe"
+)
+
+type header struct {
+	version uint32
+	pid     int32
+}
+
+type data struct {
+	effective   uint32
+	permitted   uint32
+	inheritable uint32
+}
+
+const CAP_SYS_TIME = 25
+const CAP_SYSLOG = 34
+
+type Caps struct {
+	header header
+	data   [2]data
+}
+
+func Get() (Caps, error) {
+	var c Caps
+
+	// Get capability version
+	if _, _, errno := syscall.Syscall(syscall.SYS_CAPGET, uintptr(unsafe.Pointer(&c.header)), uintptr(unsafe.Pointer(nil)), 0); errno != 0 {
+		return c, fmt.Errorf("SYS_CAPGET: %v", errno)
+	}
+
+	// Get current capabilities
+	if _, _, errno := syscall.Syscall(syscall.SYS_CAPGET, uintptr(unsafe.Pointer(&c.header)), uintptr(unsafe.Pointer(&c.data[0])), 0); errno != 0 {
+		return c, fmt.Errorf("SYS_CAPGET: %v", errno)
+	}
+
+	return c, nil
+}
+
+func (c Caps) Has(capSearch uint) bool {
+	return (c.data[0].inheritable & (1 << capSearch)) != 0
+}
+
+func (c Caps) Inheritable() uint32 {
+	return c.data[0].inheritable
+}