From d461448006fb6d35b1942177e1d006d67fd2b8b5 Mon Sep 17 00:00:00 2001
From: Umang Parmar <umangjparmar@gmail.com>
Date: Tue, 17 Dec 2019 22:06:15 +0530
Subject: [PATCH] x/sys/unix: add PrctlRetInt, a Prctl variant that returns
 (int, error)

Fixes golang/go#35978
---
 unix/syscall_linux.go      | 11 +++++++++++
 unix/syscall_linux_test.go | 14 ++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/unix/syscall_linux.go b/unix/syscall_linux.go
index 26903bca..4a51e75d 100644
--- a/unix/syscall_linux.go
+++ b/unix/syscall_linux.go
@@ -1631,6 +1631,17 @@ func Getpgrp() (pid int) {
 //sysnb	Settimeofday(tv *Timeval) (err error)
 //sys	Setns(fd int, nstype int) (err error)
 
+// PrctlRetInt performs a prctl operation specified by option and further
+// optional arguments arg2 through arg5 depending on option. It returns a
+// non-negative integer that is returned by the prctl syscall.
+func PrctlRetInt(option int, arg2 uintptr, arg3 uintptr, arg4 uintptr, arg5 uintptr) (int, error) {
+	ret, _, err := Syscall6(SYS_PRCTL, uintptr(option), uintptr(arg2), uintptr(arg3), uintptr(arg4), uintptr(arg5), 0)
+	if err != 0 {
+		return 0, err
+	}
+	return int(ret), nil
+}
+
 // issue 1435.
 // On linux Setuid and Setgid only affects the current thread, not the process.
 // This does not match what most callers expect so we must return an error
diff --git a/unix/syscall_linux_test.go b/unix/syscall_linux_test.go
index 7d9c8a16..abdfc52c 100644
--- a/unix/syscall_linux_test.go
+++ b/unix/syscall_linux_test.go
@@ -686,3 +686,17 @@ func TestEpoll(t *testing.T) {
 		t.Errorf("EpollWait: wrong Fd in event: got %v, expected %v", got, fd)
 	}
 }
+
+func TestPrctlRetInt(t *testing.T) {
+	err := unix.Prctl(unix.PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)
+	if err != nil {
+		t.Skipf("Prctl: %v, skipping test", err)
+	}
+	v, err := unix.PrctlRetInt(unix.PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0)
+	if err != nil {
+		t.Fatalf("failed to perform prctl: %v", err)
+	}
+	if v != 1 {
+		t.Fatalf("unexpected return from prctl; got %v, expected %v", v, 1)
+	}
+}