Adding upstream version 1.20.14.upstream/1.20.14upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 641 insertions, 0 deletions

diff --git a/src/syscall/syscall_linux_test.go b/src/syscall/syscall_linux_test.go
new file mode 100644
index 0000000..ff128b1
--- /dev/null
+++ b/src/syscall/syscall_linux_test.go
@@ -0,0 +1,641 @@
+// 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.
+
+package syscall_test
+
+import (
+	"fmt"
+	"io"
+	"io/fs"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"sort"
+	"strconv"
+	"strings"
+	"sync"
+	"syscall"
+	"testing"
+	"unsafe"
+)
+
+// chtmpdir changes the working directory to a new temporary directory and
+// provides a cleanup function. Used when PWD is read-only.
+func chtmpdir(t *testing.T) func() {
+	oldwd, err := os.Getwd()
+	if err != nil {
+		t.Fatalf("chtmpdir: %v", err)
+	}
+	d, err := os.MkdirTemp("", "test")
+	if err != nil {
+		t.Fatalf("chtmpdir: %v", err)
+	}
+	if err := os.Chdir(d); err != nil {
+		t.Fatalf("chtmpdir: %v", err)
+	}
+	return func() {
+		if err := os.Chdir(oldwd); err != nil {
+			t.Fatalf("chtmpdir: %v", err)
+		}
+		os.RemoveAll(d)
+	}
+}
+
+func touch(t *testing.T, name string) {
+	f, err := os.Create(name)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := f.Close(); err != nil {
+		t.Fatal(err)
+	}
+}
+
+const (
+	_AT_SYMLINK_NOFOLLOW = 0x100
+	_AT_FDCWD            = -0x64
+	_AT_EACCESS          = 0x200
+	_F_OK                = 0
+	_R_OK                = 4
+)
+
+func TestFaccessat(t *testing.T) {
+	defer chtmpdir(t)()
+	touch(t, "file1")
+
+	err := syscall.Faccessat(_AT_FDCWD, "file1", _R_OK, 0)
+	if err != nil {
+		t.Errorf("Faccessat: unexpected error: %v", err)
+	}
+
+	err = syscall.Faccessat(_AT_FDCWD, "file1", _R_OK, 2)
+	if err != syscall.EINVAL {
+		t.Errorf("Faccessat: unexpected error: %v, want EINVAL", err)
+	}
+
+	err = syscall.Faccessat(_AT_FDCWD, "file1", _R_OK, _AT_EACCESS)
+	if err != nil {
+		t.Errorf("Faccessat: unexpected error: %v", err)
+	}
+
+	err = os.Symlink("file1", "symlink1")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = syscall.Faccessat(_AT_FDCWD, "symlink1", _R_OK, _AT_SYMLINK_NOFOLLOW)
+	if err != nil {
+		t.Errorf("Faccessat SYMLINK_NOFOLLOW: unexpected error %v", err)
+	}
+
+	// We can't really test _AT_SYMLINK_NOFOLLOW, because there
+	// doesn't seem to be any way to change the mode of a symlink.
+	// We don't test _AT_EACCESS because such tests are only
+	// meaningful if run as root.
+
+	err = syscall.Fchmodat(_AT_FDCWD, "file1", 0, 0)
+	if err != nil {
+		t.Errorf("Fchmodat: unexpected error %v", err)
+	}
+
+	err = syscall.Faccessat(_AT_FDCWD, "file1", _F_OK, _AT_SYMLINK_NOFOLLOW)
+	if err != nil {
+		t.Errorf("Faccessat: unexpected error: %v", err)
+	}
+
+	err = syscall.Faccessat(_AT_FDCWD, "file1", _R_OK, _AT_SYMLINK_NOFOLLOW)
+	if err != syscall.EACCES {
+		if syscall.Getuid() != 0 {
+			t.Errorf("Faccessat: unexpected error: %v, want EACCES", err)
+		}
+	}
+}
+
+func TestFchmodat(t *testing.T) {
+	defer chtmpdir(t)()
+
+	touch(t, "file1")
+	os.Symlink("file1", "symlink1")
+
+	err := syscall.Fchmodat(_AT_FDCWD, "symlink1", 0444, 0)
+	if err != nil {
+		t.Fatalf("Fchmodat: unexpected error: %v", err)
+	}
+
+	fi, err := os.Stat("file1")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if fi.Mode() != 0444 {
+		t.Errorf("Fchmodat: failed to change mode: expected %v, got %v", 0444, fi.Mode())
+	}
+
+	err = syscall.Fchmodat(_AT_FDCWD, "symlink1", 0444, _AT_SYMLINK_NOFOLLOW)
+	if err != syscall.EOPNOTSUPP {
+		t.Fatalf("Fchmodat: unexpected error: %v, expected EOPNOTSUPP", err)
+	}
+}
+
+func TestMain(m *testing.M) {
+	if os.Getenv("GO_DEATHSIG_PARENT") == "1" {
+		deathSignalParent()
+	} else if os.Getenv("GO_DEATHSIG_CHILD") == "1" {
+		deathSignalChild()
+	} else if os.Getenv("GO_SYSCALL_NOERROR") == "1" {
+		syscallNoError()
+	}
+
+	os.Exit(m.Run())
+}
+
+func TestParseNetlinkMessage(t *testing.T) {
+	for i, b := range [][]byte{
+		{103, 0, 0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 2, 11, 0, 1, 0, 0, 0, 0, 5, 8, 0, 3,
+			0, 8, 0, 6, 0, 0, 0, 0, 1, 63, 0, 10, 0, 69, 16, 0, 59, 39, 82, 64, 0, 64, 6, 21, 89, 127, 0, 0,
+			1, 127, 0, 0, 1, 230, 228, 31, 144, 32, 186, 155, 211, 185, 151, 209, 179, 128, 24, 1, 86,
+			53, 119, 0, 0, 1, 1, 8, 10, 0, 17, 234, 12, 0, 17, 189, 126, 107, 106, 108, 107, 106, 13, 10,
+		},
+		{106, 0, 0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 2, 11, 0, 1, 0, 0, 0, 0, 3, 8, 0, 3,
+			0, 8, 0, 6, 0, 0, 0, 0, 1, 66, 0, 10, 0, 69, 0, 0, 62, 230, 255, 64, 0, 64, 6, 85, 184, 127, 0, 0,
+			1, 127, 0, 0, 1, 237, 206, 31, 144, 73, 197, 128, 65, 250, 60, 192, 97, 128, 24, 1, 86, 253, 21, 0,
+			0, 1, 1, 8, 10, 0, 51, 106, 89, 0, 51, 102, 198, 108, 104, 106, 108, 107, 104, 108, 107, 104, 10,
+		},
+		{102, 0, 0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 2, 11, 0, 1, 0, 0, 0, 0, 1, 8, 0, 3, 0,
+			8, 0, 6, 0, 0, 0, 0, 1, 62, 0, 10, 0, 69, 0, 0, 58, 231, 2, 64, 0, 64, 6, 85, 185, 127, 0, 0, 1, 127,
+			0, 0, 1, 237, 206, 31, 144, 73, 197, 128, 86, 250, 60, 192, 97, 128, 24, 1, 86, 104, 64, 0, 0, 1, 1, 8,
+			10, 0, 52, 198, 200, 0, 51, 135, 232, 101, 115, 97, 103, 103, 10,
+		},
+	} {
+		m, err := syscall.ParseNetlinkMessage(b)
+		if err != syscall.EINVAL {
+			t.Errorf("#%d: got %v; want EINVAL", i, err)
+		}
+		if m != nil {
+			t.Errorf("#%d: got %v; want nil", i, m)
+		}
+	}
+}
+
+func TestSyscallNoError(t *testing.T) {
+	// On Linux there are currently no syscalls which don't fail and return
+	// a value larger than 0xfffffffffffff001 so we could test RawSyscall
+	// vs. RawSyscallNoError on 64bit architectures.
+	if unsafe.Sizeof(uintptr(0)) != 4 {
+		t.Skip("skipping on non-32bit architecture")
+	}
+
+	// See https://golang.org/issue/35422
+	// On MIPS, Linux returns whether the syscall had an error in a separate
+	// register (R7), not using a negative return value as on other
+	// architectures.
+	if runtime.GOARCH == "mips" || runtime.GOARCH == "mipsle" {
+		t.Skipf("skipping on %s", runtime.GOARCH)
+	}
+
+	if os.Getuid() != 0 {
+		t.Skip("skipping root only test")
+	}
+
+	if runtime.GOOS == "android" {
+		t.Skip("skipping on rooted android, see issue 27364")
+	}
+
+	// Copy the test binary to a location that a non-root user can read/execute
+	// after we drop privileges
+	tempDir, err := os.MkdirTemp("", "TestSyscallNoError")
+	if err != nil {
+		t.Fatalf("cannot create temporary directory: %v", err)
+	}
+	defer os.RemoveAll(tempDir)
+	os.Chmod(tempDir, 0755)
+
+	tmpBinary := filepath.Join(tempDir, filepath.Base(os.Args[0]))
+
+	src, err := os.Open(os.Args[0])
+	if err != nil {
+		t.Fatalf("cannot open binary %q, %v", os.Args[0], err)
+	}
+	defer src.Close()
+
+	dst, err := os.OpenFile(tmpBinary, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0755)
+	if err != nil {
+		t.Fatalf("cannot create temporary binary %q, %v", tmpBinary, err)
+	}
+	if _, err := io.Copy(dst, src); err != nil {
+		t.Fatalf("failed to copy test binary to %q, %v", tmpBinary, err)
+	}
+	err = dst.Close()
+	if err != nil {
+		t.Fatalf("failed to close test binary %q, %v", tmpBinary, err)
+	}
+
+	uid := uint32(0xfffffffe)
+	err = os.Chown(tmpBinary, int(uid), -1)
+	if err != nil {
+		t.Fatalf("failed to chown test binary %q, %v", tmpBinary, err)
+	}
+
+	err = os.Chmod(tmpBinary, 0755|fs.ModeSetuid)
+	if err != nil {
+		t.Fatalf("failed to set setuid bit on test binary %q, %v", tmpBinary, err)
+	}
+
+	cmd := exec.Command(tmpBinary)
+	cmd.Env = append(os.Environ(), "GO_SYSCALL_NOERROR=1")
+
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("failed to start first child process: %v", err)
+	}
+
+	got := strings.TrimSpace(string(out))
+	want := strconv.FormatUint(uint64(uid)+1, 10) + " / " +
+		strconv.FormatUint(uint64(-uid), 10) + " / " +
+		strconv.FormatUint(uint64(uid), 10)
+	if got != want {
+		if filesystemIsNoSUID(tmpBinary) {
+			t.Skip("skipping test when temp dir is mounted nosuid")
+		}
+		// formatted so the values are aligned for easier comparison
+		t.Errorf("expected %s,\ngot      %s", want, got)
+	}
+}
+
+// filesystemIsNoSUID reports whether the filesystem for the given
+// path is mounted nosuid.
+func filesystemIsNoSUID(path string) bool {
+	var st syscall.Statfs_t
+	if syscall.Statfs(path, &st) != nil {
+		return false
+	}
+	return st.Flags&syscall.MS_NOSUID != 0
+}
+
+func syscallNoError() {
+	// Test that the return value from SYS_GETEUID32 (which cannot fail)
+	// doesn't get treated as an error (see https://golang.org/issue/22924)
+	euid1, _, e := syscall.RawSyscall(syscall.Sys_GETEUID, 0, 0, 0)
+	euid2, _ := syscall.RawSyscallNoError(syscall.Sys_GETEUID, 0, 0, 0)
+
+	fmt.Println(uintptr(euid1), "/", int(e), "/", uintptr(euid2))
+	os.Exit(0)
+}
+
+// reference uapi/linux/prctl.h
+const (
+	PR_GET_KEEPCAPS uintptr = 7
+	PR_SET_KEEPCAPS         = 8
+)
+
+// TestAllThreadsSyscall tests that the go runtime can perform
+// syscalls that execute on all OSThreads - with which to support
+// POSIX semantics for security state changes.
+func TestAllThreadsSyscall(t *testing.T) {
+	if _, _, err := syscall.AllThreadsSyscall(syscall.SYS_PRCTL, PR_SET_KEEPCAPS, 0, 0); err == syscall.ENOTSUP {
+		t.Skip("AllThreadsSyscall disabled with cgo")
+	}
+
+	fns := []struct {
+		label string
+		fn    func(uintptr) error
+	}{
+		{
+			label: "prctl<3-args>",
+			fn: func(v uintptr) error {
+				_, _, e := syscall.AllThreadsSyscall(syscall.SYS_PRCTL, PR_SET_KEEPCAPS, v, 0)
+				if e != 0 {
+					return e
+				}
+				return nil
+			},
+		},
+		{
+			label: "prctl<6-args>",
+			fn: func(v uintptr) error {
+				_, _, e := syscall.AllThreadsSyscall6(syscall.SYS_PRCTL, PR_SET_KEEPCAPS, v, 0, 0, 0, 0)
+				if e != 0 {
+					return e
+				}
+				return nil
+			},
+		},
+	}
+
+	waiter := func(q <-chan uintptr, r chan<- uintptr, once bool) {
+		for x := range q {
+			runtime.LockOSThread()
+			v, _, e := syscall.Syscall(syscall.SYS_PRCTL, PR_GET_KEEPCAPS, 0, 0)
+			if e != 0 {
+				t.Errorf("tid=%d prctl(PR_GET_KEEPCAPS) failed: %v", syscall.Gettid(), e)
+			} else if x != v {
+				t.Errorf("tid=%d prctl(PR_GET_KEEPCAPS) mismatch: got=%d want=%d", syscall.Gettid(), v, x)
+			}
+			r <- v
+			if once {
+				break
+			}
+			runtime.UnlockOSThread()
+		}
+	}
+
+	// launches per fns member.
+	const launches = 11
+	question := make(chan uintptr)
+	response := make(chan uintptr)
+	defer close(question)
+
+	routines := 0
+	for i, v := range fns {
+		for j := 0; j < launches; j++ {
+			// Add another goroutine - the closest thing
+			// we can do to encourage more OS thread
+			// creation - while the test is running.  The
+			// actual thread creation may or may not be
+			// needed, based on the number of available
+			// unlocked OS threads at the time waiter
+			// calls runtime.LockOSThread(), but the goal
+			// of doing this every time through the loop
+			// is to race thread creation with v.fn(want)
+			// being executed. Via the once boolean we
+			// also encourage one in 5 waiters to return
+			// locked after participating in only one
+			// question response sequence. This allows the
+			// test to race thread destruction too.
+			once := routines%5 == 4
+			go waiter(question, response, once)
+
+			// Keep a count of how many goroutines are
+			// going to participate in the
+			// question/response test. This will count up
+			// towards 2*launches minus the count of
+			// routines that have been invoked with
+			// once=true.
+			routines++
+
+			// Decide what value we want to set the
+			// process-shared KEEPCAPS. Note, there is
+			// an explicit repeat of 0 when we change the
+			// variant of the syscall being used.
+			want := uintptr(j & 1)
+
+			// Invoke the AllThreadsSyscall* variant.
+			if err := v.fn(want); err != nil {
+				t.Errorf("[%d,%d] %s(PR_SET_KEEPCAPS, %d, ...): %v", i, j, v.label, j&1, err)
+			}
+
+			// At this point, we want all launched Go
+			// routines to confirm that they see the
+			// wanted value for KEEPCAPS.
+			for k := 0; k < routines; k++ {
+				question <- want
+			}
+
+			// At this point, we should have a large
+			// number of locked OS threads all wanting to
+			// reply.
+			for k := 0; k < routines; k++ {
+				if got := <-response; got != want {
+					t.Errorf("[%d,%d,%d] waiter result got=%d, want=%d", i, j, k, got, want)
+				}
+			}
+
+			// Provide an explicit opportunity for this Go
+			// routine to change Ms.
+			runtime.Gosched()
+
+			if once {
+				// One waiter routine will have exited.
+				routines--
+			}
+
+			// Whatever M we are now running on, confirm
+			// we see the wanted value too.
+			if v, _, e := syscall.Syscall(syscall.SYS_PRCTL, PR_GET_KEEPCAPS, 0, 0); e != 0 {
+				t.Errorf("[%d,%d] prctl(PR_GET_KEEPCAPS) failed: %v", i, j, e)
+			} else if v != want {
+				t.Errorf("[%d,%d] prctl(PR_GET_KEEPCAPS) gave wrong value: got=%v, want=1", i, j, v)
+			}
+		}
+	}
+}
+
+// compareStatus is used to confirm the contents of the thread
+// specific status files match expectations.
+func compareStatus(filter, expect string) error {
+	expected := filter + expect
+	pid := syscall.Getpid()
+	fs, err := os.ReadDir(fmt.Sprintf("/proc/%d/task", pid))
+	if err != nil {
+		return fmt.Errorf("unable to find %d tasks: %v", pid, err)
+	}
+	expectedProc := fmt.Sprintf("Pid:\t%d", pid)
+	foundAThread := false
+	for _, f := range fs {
+		tf := fmt.Sprintf("/proc/%s/status", f.Name())
+		d, err := os.ReadFile(tf)
+		if err != nil {
+			// There are a surprising number of ways this
+			// can error out on linux.  We've seen all of
+			// the following, so treat any error here as
+			// equivalent to the "process is gone":
+			//    os.IsNotExist(err),
+			//    "... : no such process",
+			//    "... : bad file descriptor.
+			continue
+		}
+		lines := strings.Split(string(d), "\n")
+		for _, line := range lines {
+			// Different kernel vintages pad differently.
+			line = strings.TrimSpace(line)
+			if strings.HasPrefix(line, "Pid:\t") {
+				// On loaded systems, it is possible
+				// for a TID to be reused really
+				// quickly. As such, we need to
+				// validate that the thread status
+				// info we just read is a task of the
+				// same process PID as we are
+				// currently running, and not a
+				// recently terminated thread
+				// resurfaced in a different process.
+				if line != expectedProc {
+					break
+				}
+				// Fall through in the unlikely case
+				// that filter at some point is
+				// "Pid:\t".
+			}
+			if strings.HasPrefix(line, filter) {
+				if line == expected {
+					foundAThread = true
+					break
+				}
+				if filter == "Groups:" && strings.HasPrefix(line, "Groups:\t") {
+					// https://github.com/golang/go/issues/46145
+					// Containers don't reliably output this line in sorted order so manually sort and compare that.
+					a := strings.Split(line[8:], " ")
+					sort.Strings(a)
+					got := strings.Join(a, " ")
+					if got == expected[8:] {
+						foundAThread = true
+						break
+					}
+
+				}
+				return fmt.Errorf("%q got:%q want:%q (bad) [pid=%d file:'%s' %v]\n", tf, line, expected, pid, string(d), expectedProc)
+			}
+		}
+	}
+	if !foundAThread {
+		return fmt.Errorf("found no thread /proc/<TID>/status files for process %q", expectedProc)
+	}
+	return nil
+}
+
+// killAThread locks the goroutine to an OS thread and exits; this
+// causes an OS thread to terminate.
+func killAThread(c <-chan struct{}) {
+	runtime.LockOSThread()
+	<-c
+	return
+}
+
+// TestSetuidEtc performs tests on all of the wrapped system calls
+// that mirror to the 9 glibc syscalls with POSIX semantics. The test
+// here is considered authoritative and should compile and run
+// CGO_ENABLED=0 or 1. Note, there is an extended copy of this same
+// test in ../../misc/cgo/test/issue1435.go which requires
+// CGO_ENABLED=1 and launches pthreads from C that run concurrently
+// with the Go code of the test - and the test validates that these
+// pthreads are also kept in sync with the security state changed with
+// the syscalls. Care should be taken to mirror any enhancements to
+// this test here in that file too.
+func TestSetuidEtc(t *testing.T) {
+	if syscall.Getuid() != 0 {
+		t.Skip("skipping root only test")
+	}
+	if _, err := os.Stat("/etc/alpine-release"); err == nil {
+		t.Skip("skipping glibc test on alpine - go.dev/issue/19938")
+	}
+	vs := []struct {
+		call           string
+		fn             func() error
+		filter, expect string
+	}{
+		{call: "Setegid(1)", fn: func() error { return syscall.Setegid(1) }, filter: "Gid:", expect: "\t0\t1\t0\t1"},
+		{call: "Setegid(0)", fn: func() error { return syscall.Setegid(0) }, filter: "Gid:", expect: "\t0\t0\t0\t0"},
+
+		{call: "Seteuid(1)", fn: func() error { return syscall.Seteuid(1) }, filter: "Uid:", expect: "\t0\t1\t0\t1"},
+		{call: "Setuid(0)", fn: func() error { return syscall.Setuid(0) }, filter: "Uid:", expect: "\t0\t0\t0\t0"},
+
+		{call: "Setgid(1)", fn: func() error { return syscall.Setgid(1) }, filter: "Gid:", expect: "\t1\t1\t1\t1"},
+		{call: "Setgid(0)", fn: func() error { return syscall.Setgid(0) }, filter: "Gid:", expect: "\t0\t0\t0\t0"},
+
+		{call: "Setgroups([]int{0,1,2,3})", fn: func() error { return syscall.Setgroups([]int{0, 1, 2, 3}) }, filter: "Groups:", expect: "\t0 1 2 3"},
+		{call: "Setgroups(nil)", fn: func() error { return syscall.Setgroups(nil) }, filter: "Groups:", expect: ""},
+		{call: "Setgroups([]int{0})", fn: func() error { return syscall.Setgroups([]int{0}) }, filter: "Groups:", expect: "\t0"},
+
+		{call: "Setregid(101,0)", fn: func() error { return syscall.Setregid(101, 0) }, filter: "Gid:", expect: "\t101\t0\t0\t0"},
+		{call: "Setregid(0,102)", fn: func() error { return syscall.Setregid(0, 102) }, filter: "Gid:", expect: "\t0\t102\t102\t102"},
+		{call: "Setregid(0,0)", fn: func() error { return syscall.Setregid(0, 0) }, filter: "Gid:", expect: "\t0\t0\t0\t0"},
+
+		{call: "Setreuid(1,0)", fn: func() error { return syscall.Setreuid(1, 0) }, filter: "Uid:", expect: "\t1\t0\t0\t0"},
+		{call: "Setreuid(0,2)", fn: func() error { return syscall.Setreuid(0, 2) }, filter: "Uid:", expect: "\t0\t2\t2\t2"},
+		{call: "Setreuid(0,0)", fn: func() error { return syscall.Setreuid(0, 0) }, filter: "Uid:", expect: "\t0\t0\t0\t0"},
+
+		{call: "Setresgid(101,0,102)", fn: func() error { return syscall.Setresgid(101, 0, 102) }, filter: "Gid:", expect: "\t101\t0\t102\t0"},
+		{call: "Setresgid(0,102,101)", fn: func() error { return syscall.Setresgid(0, 102, 101) }, filter: "Gid:", expect: "\t0\t102\t101\t102"},
+		{call: "Setresgid(0,0,0)", fn: func() error { return syscall.Setresgid(0, 0, 0) }, filter: "Gid:", expect: "\t0\t0\t0\t0"},
+
+		{call: "Setresuid(1,0,2)", fn: func() error { return syscall.Setresuid(1, 0, 2) }, filter: "Uid:", expect: "\t1\t0\t2\t0"},
+		{call: "Setresuid(0,2,1)", fn: func() error { return syscall.Setresuid(0, 2, 1) }, filter: "Uid:", expect: "\t0\t2\t1\t2"},
+		{call: "Setresuid(0,0,0)", fn: func() error { return syscall.Setresuid(0, 0, 0) }, filter: "Uid:", expect: "\t0\t0\t0\t0"},
+	}
+
+	for i, v := range vs {
+		// Generate some thread churn as we execute the tests.
+		c := make(chan struct{})
+		go killAThread(c)
+		close(c)
+
+		if err := v.fn(); err != nil {
+			t.Errorf("[%d] %q failed: %v", i, v.call, err)
+			continue
+		}
+		if err := compareStatus(v.filter, v.expect); err != nil {
+			t.Errorf("[%d] %q comparison: %v", i, v.call, err)
+		}
+	}
+}
+
+// TestAllThreadsSyscallError verifies that errors are properly returned when
+// the syscall fails on the original thread.
+func TestAllThreadsSyscallError(t *testing.T) {
+	// SYS_CAPGET takes pointers as the first two arguments. Since we pass
+	// 0, we expect to get EFAULT back.
+	r1, r2, err := syscall.AllThreadsSyscall(syscall.SYS_CAPGET, 0, 0, 0)
+	if err == syscall.ENOTSUP {
+		t.Skip("AllThreadsSyscall disabled with cgo")
+	}
+	if err != syscall.EFAULT {
+		t.Errorf("AllThreadSyscall(SYS_CAPGET) got %d, %d, %v, want err %v", r1, r2, err, syscall.EFAULT)
+	}
+}
+
+// TestAllThreadsSyscallBlockedSyscall confirms that AllThreadsSyscall
+// can interrupt threads in long-running system calls. This test will
+// deadlock if this doesn't work correctly.
+func TestAllThreadsSyscallBlockedSyscall(t *testing.T) {
+	if _, _, err := syscall.AllThreadsSyscall(syscall.SYS_PRCTL, PR_SET_KEEPCAPS, 0, 0); err == syscall.ENOTSUP {
+		t.Skip("AllThreadsSyscall disabled with cgo")
+	}
+
+	rd, wr, err := os.Pipe()
+	if err != nil {
+		t.Fatalf("unable to obtain a pipe: %v", err)
+	}
+
+	// Perform a blocking read on the pipe.
+	var wg sync.WaitGroup
+	ready := make(chan bool)
+	wg.Add(1)
+	go func() {
+		data := make([]byte, 1)
+
+		// To narrow the window we have to wait for this
+		// goroutine to block in read, synchronize just before
+		// calling read.
+		ready <- true
+
+		// We use syscall.Read directly to avoid the poller.
+		// This will return when the write side is closed.
+		n, err := syscall.Read(int(rd.Fd()), data)
+		if !(n == 0 && err == nil) {
+			t.Errorf("expected read to return 0, got %d, %s", n, err)
+		}
+
+		// Clean up rd and also ensure rd stays reachable so
+		// it doesn't get closed by GC.
+		rd.Close()
+		wg.Done()
+	}()
+	<-ready
+
+	// Loop here to give the goroutine more time to block in read.
+	// Generally this will trigger on the first iteration anyway.
+	pid := syscall.Getpid()
+	for i := 0; i < 100; i++ {
+		if id, _, e := syscall.AllThreadsSyscall(syscall.SYS_GETPID, 0, 0, 0); e != 0 {
+			t.Errorf("[%d] getpid failed: %v", i, e)
+		} else if int(id) != pid {
+			t.Errorf("[%d] getpid got=%d, want=%d", i, id, pid)
+		}
+		// Provide an explicit opportunity for this goroutine
+		// to change Ms.
+		runtime.Gosched()
+	}
+	wr.Close()
+	wg.Wait()
+}