internal/testenv, syscall: move isNotSupported to internal/testenv

This allows to use this helper function in packages other than syscall,
namely package net.

For #58114

Change-Id: I72c59ab013e9195801ff1315019ae1aef4396287
Reviewed-on: https://go-review.googlesource.com/c/go/+/476216
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Bryan Mills <bcmills@google.com>

4 files changed, 63 insertions, 50 deletions

diff --git a/src/internal/testenv/testenv.go b/src/internal/testenv/testenv.go
index 816a1a100f..94cec0b8bd 100644
--- a/src/internal/testenv/testenv.go
+++ b/src/internal/testenv/testenv.go
@@ -422,3 +422,9 @@ func WriteImportcfg(t testing.TB, dstPath string, packageFiles map[string]string
 		t.Fatal(err)
 	}
 }
+
+// SyscallIsNotSupported reports whether err may indicate that a system call is
+// not supported by the current platform or execution environment.
+func SyscallIsNotSupported(err error) bool {
+	return syscallIsNotSupported(err)
+}
diff --git a/src/internal/testenv/testenv_notunix.go b/src/internal/testenv/testenv_notunix.go
index 180206bc9b..9313c7c827 100644
--- a/src/internal/testenv/testenv_notunix.go
+++ b/src/internal/testenv/testenv_notunix.go
@@ -6,8 +6,15 @@
 
 package testenv
 
-import "os"
+import (
+	"errors"
+	"os"
+)
 
 // Sigquit is the signal to send to kill a hanging subprocess.
 // On Unix we send SIGQUIT, but on non-Unix we only have os.Kill.
 var Sigquit = os.Kill
+
+func syscallIsNotSupported(err error) bool {
+	return errors.Is(err, errors.ErrUnsupported)
+}
diff --git a/src/internal/testenv/testenv_unix.go b/src/internal/testenv/testenv_unix.go
index a97e88da2f..92b5024f0b 100644
--- a/src/internal/testenv/testenv_unix.go
+++ b/src/internal/testenv/testenv_unix.go
@@ -6,8 +6,43 @@
 
 package testenv
 
-import "syscall"
+import (
+	"errors"
+	"io/fs"
+	"syscall"
+)
 
 // Sigquit is the signal to send to kill a hanging subprocess.
 // Send SIGQUIT to get a stack trace.
 var Sigquit = syscall.SIGQUIT
+
+func syscallIsNotSupported(err error) bool {
+	if err == nil {
+		return false
+	}
+
+	var errno syscall.Errno
+	if errors.As(err, &errno) {
+		switch errno {
+		case syscall.ENOSYS, syscall.ENOTSUP:
+			// Explicitly not supported.
+			// TODO(#41198): remove these cases when errors.Is reports that they are
+			// equivalent to ErrUnsupported.
+			return true
+		case syscall.EPERM, syscall.EROFS:
+			// User lacks permission: either the call requires root permission and the
+			// user is not root, or the call is denied by a container security policy.
+			return true
+		case syscall.EINVAL:
+			// Some containers return EINVAL instead of EPERM if a system call is
+			// denied by security policy.
+			return true
+		}
+	}
+
+	if errors.Is(err, fs.ErrPermission) || errors.Is(err, errors.ErrUnsupported) {
+		return true
+	}
+
+	return false
+}
diff --git a/src/syscall/exec_linux_test.go b/src/syscall/exec_linux_test.go
index 074a8172d7..7ec10ce3a7 100644
--- a/src/syscall/exec_linux_test.go
+++ b/src/syscall/exec_linux_test.go
@@ -8,12 +8,10 @@ package syscall_test
 
 import (
 	"bytes"
-	"errors"
 	"flag"
 	"fmt"
 	"internal/testenv"
 	"io"
-	"io/fs"
 	"os"
 	"os/exec"
 	"os/user"
@@ -27,39 +25,6 @@ import (
 	"unsafe"
 )
 
-// isNotSupported reports whether err may indicate that a system call is
-// not supported by the current platform or execution environment.
-func isNotSupported(err error) bool {
-	if err == nil {
-		return false
-	}
-
-	var errno syscall.Errno
-	if errors.As(err, &errno) {
-		switch errno {
-		case syscall.ENOSYS, syscall.ENOTSUP:
-			// Explicitly not supported.
-			// TODO(#41198): remove these cases when errors.Is reports that they are
-			// equivalent to ErrUnsupported.
-			return true
-		case syscall.EPERM, syscall.EROFS:
-			// User lacks permission: either the call requires root permission and the
-			// user is not root, or the call is denied by a container security policy.
-			return true
-		case syscall.EINVAL:
-			// Some containers return EINVAL instead of EPERM if a system call is
-			// denied by security policy.
-			return true
-		}
-	}
-
-	if errors.Is(err, fs.ErrPermission) || errors.Is(err, errors.ErrUnsupported) {
-		return true
-	}
-
-	return false
-}
-
 // whoamiNEWUSER returns a command that runs "whoami" with CLONE_NEWUSER,
 // mapping uid and gid 0 to the actual uid and gid of the test.
 func whoamiNEWUSER(t *testing.T, uid, gid int, setgroups bool) *exec.Cmd {
@@ -96,7 +61,7 @@ func TestCloneNEWUSERAndRemap(t *testing.T) {
 					if err == nil {
 						t.Skipf("unexpected success: probably old kernel without security fix?")
 					}
-					if isNotSupported(err) {
+					if testenv.SyscallIsNotSupported(err) {
 						t.Skipf("skipping: CLONE_NEWUSER appears to be unsupported")
 					}
 					t.Fatalf("got non-permission error") // Already logged above.
@@ -105,7 +70,7 @@ func TestCloneNEWUSERAndRemap(t *testing.T) {
 			}
 
 			if err != nil {
-				if isNotSupported(err) {
+				if testenv.SyscallIsNotSupported(err) {
 					// May be inside a container that disallows CLONE_NEWUSER.
 					t.Skipf("skipping: CLONE_NEWUSER appears to be unsupported")
 				}
@@ -125,7 +90,7 @@ func TestEmptyCredGroupsDisableSetgroups(t *testing.T) {
 	cmd := whoamiNEWUSER(t, os.Getuid(), os.Getgid(), false)
 	cmd.SysProcAttr.Credential = &syscall.Credential{}
 	if err := cmd.Run(); err != nil {
-		if isNotSupported(err) {
+		if testenv.SyscallIsNotSupported(err) {
 			t.Skipf("skipping: %v: %v", cmd, err)
 		}
 		t.Fatal(err)
@@ -156,7 +121,7 @@ func TestUnshare(t *testing.T) {
 	}
 	out, err := cmd.CombinedOutput()
 	if err != nil {
-		if isNotSupported(err) {
+		if testenv.SyscallIsNotSupported(err) {
 			// CLONE_NEWNET does not appear to be supported.
 			t.Skipf("skipping due to permission error: %v", err)
 		}
@@ -186,7 +151,7 @@ func TestGroupCleanup(t *testing.T) {
 	}
 	out, err := cmd.CombinedOutput()
 	if err != nil {
-		if isNotSupported(err) {
+		if testenv.SyscallIsNotSupported(err) {
 			t.Skipf("skipping: %v: %v", cmd, err)
 		}
 		t.Fatalf("Cmd failed with err %v, output: %s", err, out)
@@ -222,7 +187,7 @@ func TestGroupCleanupUserNamespace(t *testing.T) {
 	}
 	out, err := cmd.CombinedOutput()
 	if err != nil {
-		if isNotSupported(err) {
+		if testenv.SyscallIsNotSupported(err) {
 			t.Skipf("skipping: %v: %v", cmd, err)
 		}
 		t.Fatalf("Cmd failed with err %v, output: %s", err, out)
@@ -272,7 +237,7 @@ func TestUnshareMountNameSpace(t *testing.T) {
 
 	o, err := cmd.CombinedOutput()
 	if err != nil {
-		if isNotSupported(err) {
+		if testenv.SyscallIsNotSupported(err) {
 			t.Skipf("skipping: could not start process with CLONE_NEWNS: %v", err)
 		}
 		t.Fatalf("unshare failed: %v\n%s", err, o)
@@ -324,7 +289,7 @@ func TestUnshareMountNameSpaceChroot(t *testing.T) {
 
 	o, err := cmd.CombinedOutput()
 	if err != nil {
-		if isNotSupported(err) {
+		if testenv.SyscallIsNotSupported(err) {
 			t.Skipf("skipping: could not start process with CLONE_NEWNS and Chroot %q: %v", d, err)
 		}
 		t.Fatalf("unshare failed: %v\n%s", err, o)
@@ -383,7 +348,7 @@ func TestUnshareUidGidMapping(t *testing.T) {
 	}
 	out, err := cmd.CombinedOutput()
 	if err != nil {
-		if isNotSupported(err) {
+		if testenv.SyscallIsNotSupported(err) {
 			t.Skipf("skipping: could not start process with CLONE_NEWNS and CLONE_NEWUSER: %v", err)
 		}
 		t.Fatalf("Cmd failed with err %v, output: %s", err, out)
@@ -423,7 +388,7 @@ func prepareCgroupFD(t *testing.T) (int, string) {
 			CgroupFD:    -1,
 		},
 	})
-	if isNotSupported(err) {
+	if testenv.SyscallIsNotSupported(err) {
 		t.Skipf("clone3 with CLONE_INTO_CGROUP not available: %v", err)
 	}
 
@@ -432,7 +397,7 @@ func prepareCgroupFD(t *testing.T) (int, string) {
 	if err != nil {
 		// ErrPermission or EROFS (#57262) when running in an unprivileged container.
 		// ErrNotExist when cgroupfs is not mounted in chroot/schroot.
-		if os.IsNotExist(err) || isNotSupported(err) {
+		if os.IsNotExist(err) || testenv.SyscallIsNotSupported(err) {
 			t.Skipf("skipping: %v", err)
 		}
 		t.Fatal(err)
@@ -512,7 +477,7 @@ func TestCloneTimeNamespace(t *testing.T) {
 	}
 	out, err := cmd.CombinedOutput()
 	if err != nil {
-		if isNotSupported(err) {
+		if testenv.SyscallIsNotSupported(err) {
 			// CLONE_NEWTIME does not appear to be supported.
 			t.Skipf("skipping, CLONE_NEWTIME not supported: %v", err)
 		}
@@ -677,7 +642,7 @@ func testAmbientCaps(t *testing.T, userns bool) {
 		}
 	}
 	if err := cmd.Run(); err != nil {
-		if isNotSupported(err) {
+		if testenv.SyscallIsNotSupported(err) {
 			t.Skipf("skipping: %v: %v", cmd, err)
 		}
 		t.Fatal(err.Error())