runtime: consistently define fcntl

Clean up and consolidate on a single consistent definition of fcntl,
which takes three int32 arguments and returns either a positive result
or a negative errno value.

Change-Id: Id9505492712db4b0aab469c6bd15e4fce3c9ff6e
Reviewed-on: https://go-review.googlesource.com/c/go/+/495075
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Michael Pratt <mpratt@google.com>

34 files changed, 209 insertions, 86 deletions

diff --git a/src/runtime/export_aix_test.go b/src/runtime/export_aix_test.go
index 51df951738..48455333c1 100644
--- a/src/runtime/export_aix_test.go
+++ b/src/runtime/export_aix_test.go
@@ -4,5 +4,4 @@
 
 package runtime
 
-var Fcntl = syscall_fcntl1
 var SetNonblock = setNonblock
diff --git a/src/runtime/export_darwin_test.go b/src/runtime/export_darwin_test.go
index 66e2c02c4f..48455333c1 100644
--- a/src/runtime/export_darwin_test.go
+++ b/src/runtime/export_darwin_test.go
@@ -4,12 +4,4 @@
 
 package runtime
 
-func Fcntl(fd, cmd, arg uintptr) (uintptr, uintptr) {
-	r := fcntl(int32(fd), int32(cmd), int32(arg))
-	if r < 0 {
-		return ^uintptr(0), uintptr(-r)
-	}
-	return uintptr(r), 0
-}
-
 var SetNonblock = setNonblock
diff --git a/src/runtime/export_openbsd_test.go b/src/runtime/export_openbsd_test.go
deleted file mode 100644
index ef680dc282..0000000000
--- a/src/runtime/export_openbsd_test.go
+++ /dev/null
@@ -1,15 +0,0 @@
-// Copyright 2022 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.
-
-//go:build openbsd && !mips64
-
-package runtime
-
-func Fcntl(fd, cmd, arg uintptr) (uintptr, uintptr) {
-	r := fcntl(int32(fd), int32(cmd), int32(arg))
-	if r < 0 {
-		return ^uintptr(0), uintptr(-r)
-	}
-	return uintptr(r), 0
-}
diff --git a/src/runtime/export_solaris_test.go b/src/runtime/export_solaris_test.go
deleted file mode 100644
index e865c77691..0000000000
--- a/src/runtime/export_solaris_test.go
+++ /dev/null
@@ -1,9 +0,0 @@
-// Copyright 2019 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 runtime
-
-func Fcntl(fd, cmd, arg uintptr) (uintptr, uintptr) {
-	return sysvicall3Err(&libc_fcntl, fd, cmd, arg)
-}
diff --git a/src/runtime/export_unix_test.go b/src/runtime/export_unix_test.go
index 71a55d8941..6967e7645c 100644
--- a/src/runtime/export_unix_test.go
+++ b/src/runtime/export_unix_test.go
@@ -9,6 +9,7 @@ package runtime
 import "unsafe"
 
 var NonblockingPipe = nonblockingPipe
+var Fcntl = fcntl
 
 func sigismember(mask *sigset, i int) bool {
 	clear := *mask
diff --git a/src/runtime/nbpipe_fcntl_libc_test.go b/src/runtime/nbpipe_fcntl_libc_test.go
deleted file mode 100644
index 170245defe..0000000000
--- a/src/runtime/nbpipe_fcntl_libc_test.go
+++ /dev/null
@@ -1,18 +0,0 @@
-// Copyright 2019 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.
-
-//go:build aix || darwin || (openbsd && !mips64) || solaris
-
-package runtime_test
-
-import (
-	"runtime"
-	"syscall"
-)
-
-// Call fcntl libc function rather than calling syscall.
-func fcntl(fd uintptr, cmd int, arg uintptr) (uintptr, syscall.Errno) {
-	res, errno := runtime.Fcntl(fd, uintptr(cmd), arg)
-	return res, syscall.Errno(errno)
-}
diff --git a/src/runtime/nbpipe_fcntl_unix_test.go b/src/runtime/nbpipe_fcntl_unix_test.go
deleted file mode 100644
index b7252ea9fa..0000000000
--- a/src/runtime/nbpipe_fcntl_unix_test.go
+++ /dev/null
@@ -1,17 +0,0 @@
-// Copyright 2019 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.
-
-//go:build dragonfly || freebsd || linux || netbsd || (openbsd && mips64)
-
-package runtime_test
-
-import (
-	"internal/syscall/unix"
-	"syscall"
-)
-
-func fcntl(fd uintptr, cmd int, arg uintptr) (uintptr, syscall.Errno) {
-	res, _, err := syscall.Syscall(unix.FcntlSyscall, fd, uintptr(cmd), arg)
-	return res, err
-}
diff --git a/src/runtime/nbpipe_test.go b/src/runtime/nbpipe_test.go
index 0b0f64d076..bb21003c35 100644
--- a/src/runtime/nbpipe_test.go
+++ b/src/runtime/nbpipe_test.go
@@ -14,23 +14,29 @@ import (
 )
 
 func TestNonblockingPipe(t *testing.T) {
-	t.Parallel()
-
 	// NonblockingPipe is the test name for nonblockingPipe.
 	r, w, errno := runtime.NonblockingPipe()
 	if errno != 0 {
 		t.Fatal(syscall.Errno(errno))
 	}
-	defer func() {
-		runtime.Close(r)
-		runtime.Close(w)
-	}()
+	defer runtime.Close(w)
 
 	checkIsPipe(t, r, w)
 	checkNonblocking(t, r, "reader")
 	checkCloseonexec(t, r, "reader")
 	checkNonblocking(t, w, "writer")
 	checkCloseonexec(t, w, "writer")
+
+	// Test that fcntl returns an error as expected.
+	if runtime.Close(r) != 0 {
+		t.Fatalf("Close(%d) failed", r)
+	}
+	val := runtime.Fcntl(r, syscall.F_GETFD, 0)
+	if val >= 0 {
+		t.Errorf("Fcntl succeeded unexpectedly")
+	} else if syscall.Errno(-val) != syscall.EBADF {
+		t.Errorf("Fcntl failed with error %v, expected %v", -val, syscall.EBADF)
+	}
 }
 
 func checkIsPipe(t *testing.T, r, w int32) {
@@ -49,9 +55,9 @@ func checkIsPipe(t *testing.T, r, w int32) {
 
 func checkNonblocking(t *testing.T, fd int32, name string) {
 	t.Helper()
-	flags, errno := fcntl(uintptr(fd), syscall.F_GETFL, 0)
-	if errno != 0 {
-		t.Errorf("fcntl(%s, F_GETFL) failed: %v", name, syscall.Errno(errno))
+	flags := runtime.Fcntl(fd, syscall.F_GETFL, 0)
+	if flags < 0 {
+		t.Errorf("fcntl(%s, F_GETFL) failed: %v", name, syscall.Errno(-flags))
 	} else if flags&syscall.O_NONBLOCK == 0 {
 		t.Errorf("O_NONBLOCK not set in %s flags %#x", name, flags)
 	}
@@ -59,9 +65,9 @@ func checkNonblocking(t *testing.T, fd int32, name string) {
 
 func checkCloseonexec(t *testing.T, fd int32, name string) {
 	t.Helper()
-	flags, errno := fcntl(uintptr(fd), syscall.F_GETFD, 0)
-	if errno != 0 {
-		t.Errorf("fcntl(%s, F_GETFD) failed: %v", name, syscall.Errno(errno))
+	flags := runtime.Fcntl(fd, syscall.F_GETFD, 0)
+	if flags < 0 {
+		t.Errorf("fcntl(%s, F_GETFD) failed: %v", name, syscall.Errno(flags))
 	} else if flags&syscall.FD_CLOEXEC == 0 {
 		t.Errorf("FD_CLOEXEC not set in %s flags %#x", name, flags)
 	}
diff --git a/src/runtime/netpoll_solaris.go b/src/runtime/netpoll_solaris.go
index 426cee4378..41b2f474ac 100644
--- a/src/runtime/netpoll_solaris.go
+++ b/src/runtime/netpoll_solaris.go
@@ -96,10 +96,6 @@ func errno() int32 {
 	return *getg().m.perrno
 }
 
-func fcntl(fd, cmd, arg int32) int32 {
-	return int32(sysvicall3(&libc_fcntl, uintptr(fd), uintptr(cmd), uintptr(arg)))
-}
-
 func port_create() int32 {
 	return int32(sysvicall0(&libc_port_create))
 }
diff --git a/src/runtime/os3_solaris.go b/src/runtime/os3_solaris.go
index 42fe3790e3..a0427009a1 100644
--- a/src/runtime/os3_solaris.go
+++ b/src/runtime/os3_solaris.go
@@ -570,6 +570,15 @@ func pipe2(flags int32) (r, w int32, errno int32) {
 }
 
 //go:nosplit
+func fcntl(fd, cmd, arg int32) int32 {
+	r1, err := sysvicall3Err(&libc_fcntl, uintptr(fd), uintptr(cmd), uintptr(arg))
+	if r := int32(r1); r >= 0 {
+		return r
+	}
+	return -int32(err)
+}
+
+//go:nosplit
 func closeonexec(fd int32) {
 	fcntl(fd, _F_SETFD, _FD_CLOEXEC)
 }
diff --git a/src/runtime/os_aix.go b/src/runtime/os_aix.go
index e07c7f1da6..56b77e955a 100644
--- a/src/runtime/os_aix.go
+++ b/src/runtime/os_aix.go
@@ -353,7 +353,10 @@ func walltime() (sec int64, nsec int32) {
 
 //go:nosplit
 func fcntl(fd, cmd, arg int32) int32 {
-	r, _ := syscall3(&libc_fcntl, uintptr(fd), uintptr(cmd), uintptr(arg))
+	r, errno := syscall3(&libc_fcntl, uintptr(fd), uintptr(cmd), uintptr(arg))
+	if int32(r) < 0 {
+		return -int32(errno)
+	}
 	return int32(r)
 }
 
diff --git a/src/runtime/os_dragonfly.go b/src/runtime/os_dragonfly.go
index fa480be029..188dabbf5e 100644
--- a/src/runtime/os_dragonfly.go
+++ b/src/runtime/os_dragonfly.go
@@ -63,6 +63,7 @@ func kqueue() int32
 func kevent(kq int32, ch *keventt, nch int32, ev *keventt, nev int32, ts *timespec) int32
 
 func pipe2(flags int32) (r, w int32, errno int32)
+func fcntl(fd, cmd, arg int32) int32
 func closeonexec(fd int32)
 
 // From DragonFly's <sys/sysctl.h>
diff --git a/src/runtime/os_freebsd.go b/src/runtime/os_freebsd.go
index d5f02d9da5..cd010cf3a1 100644
--- a/src/runtime/os_freebsd.go
+++ b/src/runtime/os_freebsd.go
@@ -48,6 +48,7 @@ func kqueue() int32
 func kevent(kq int32, ch *keventt, nch int32, ev *keventt, nev int32, ts *timespec) int32
 
 func pipe2(flags int32) (r, w int32, errno int32)
+func fcntl(fd, cmd, arg int32) int32
 func closeonexec(fd int32)
 
 // From FreeBSD's <sys/sysctl.h>
diff --git a/src/runtime/os_linux.go b/src/runtime/os_linux.go
index 398ff18991..b0246e5c9f 100644
--- a/src/runtime/os_linux.go
+++ b/src/runtime/os_linux.go
@@ -466,6 +466,16 @@ func osyield_no_g() {
 
 func pipe2(flags int32) (r, w int32, errno int32)
 
+//go:nosplit
+func fcntl(fd, cmd, arg int32) int32 {
+	r, _, errno := syscall.Syscall6(syscall.SYS_FCNTL, uintptr(fd), uintptr(cmd), uintptr(arg), 0, 0, 0)
+	ri := int32(r)
+	if ri < 0 {
+		return -int32(errno)
+	}
+	return ri
+}
+
 const (
 	_si_max_size    = 128
 	_sigev_max_size = 64
diff --git a/src/runtime/os_netbsd.go b/src/runtime/os_netbsd.go
index f76c87e02e..940a1b2a36 100644
--- a/src/runtime/os_netbsd.go
+++ b/src/runtime/os_netbsd.go
@@ -79,6 +79,7 @@ func kqueue() int32
 func kevent(kq int32, ch *keventt, nch int32, ev *keventt, nev int32, ts *timespec) int32
 
 func pipe2(flags int32) (r, w int32, errno int32)
+func fcntl(fd, cmd, arg int32) int32
 func closeonexec(fd int32)
 
 const (
diff --git a/src/runtime/os_openbsd_syscall2.go b/src/runtime/os_openbsd_syscall2.go
index ebf478badf..0b61773c9d 100644
--- a/src/runtime/os_openbsd_syscall2.go
+++ b/src/runtime/os_openbsd_syscall2.go
@@ -95,6 +95,7 @@ func nanotime1() int64
 //go:noescape
 func sigaltstack(new, old *stackt)
 
+func fcntl(fd, cmd, arg int32) int32
 func closeonexec(fd int32)
 
 func walltime() (sec int64, nsec int32)
diff --git a/src/runtime/os_solaris.go b/src/runtime/os_solaris.go
index f881508b77..6e7cada0f7 100644
--- a/src/runtime/os_solaris.go
+++ b/src/runtime/os_solaris.go
@@ -149,7 +149,7 @@ func sysvicall3(fn *libcFunc, a1, a2, a3 uintptr) uintptr {
 //go:cgo_unsafe_args
 
 // sysvicall3Err returns both the system call result and the errno value.
-// This is used by sysicall3 and write1.
+// This is used by sysvicall3 and write1.
 func sysvicall3Err(fn *libcFunc, a1, a2, a3 uintptr) (r1, err uintptr) {
 	// Leave caller's PC/SP around for traceback.
 	gp := getg()
diff --git a/src/runtime/sys_darwin_amd64.s b/src/runtime/sys_darwin_amd64.s
index 1e2a353e6c..0ad67ca424 100644
--- a/src/runtime/sys_darwin_amd64.s
+++ b/src/runtime/sys_darwin_amd64.s
@@ -369,6 +369,12 @@ TEXT runtime·fcntl_trampoline(SB),NOSPLIT,$0
 	MOVL	0(DI), DI		// arg 1 fd
 	XORL	AX, AX			// vararg: say "no float args"
 	CALL	libc_fcntl(SB)
+	TESTL	AX, AX
+	JGT	noerr
+	CALL	libc_error(SB)
+	MOVL	(AX), AX
+	NEGL	AX			// caller expects negative errno value
+noerr:
 	RET
 
 // mstart_stub is the first function executed on a new thread started by pthread_create.
diff --git a/src/runtime/sys_darwin_arm64.s b/src/runtime/sys_darwin_arm64.s
index 4a51fb3a86..4111b3427b 100644
--- a/src/runtime/sys_darwin_arm64.s
+++ b/src/runtime/sys_darwin_arm64.s
@@ -314,6 +314,13 @@ TEXT runtime·fcntl_trampoline(SB),NOSPLIT,$0
 	MOVW	R2, (RSP)	// arg 3 is variadic, pass on stack
 	MOVW	0(R0), R0	// arg 1 fd
 	BL	libc_fcntl(SB)
+	MOVD	$-1, R1
+	CMP	R0, R1
+	BNE	noerr
+	BL	libc_error(SB)
+	MOVW	(R0), R0
+	NEG	R0, R0		// caller expects negative errno value
+noerr:
 	ADD	$16, RSP
 	RET
 
diff --git a/src/runtime/sys_dragonfly_amd64.s b/src/runtime/sys_dragonfly_amd64.s
index cae2039477..7901bb709f 100644
--- a/src/runtime/sys_dragonfly_amd64.s
+++ b/src/runtime/sys_dragonfly_amd64.s
@@ -385,6 +385,18 @@ TEXT runtime·kevent(SB),NOSPLIT,$0
 	MOVL	AX, ret+48(FP)
 	RET
 
+// func fcntl(fd, cmd, arg int32) int32
+TEXT runtime·fcntl(SB),NOSPLIT,$0
+	MOVL	fd+0(FP), DI	// fd
+	MOVL	cmd+4(FP), SI	// cmd
+	MOVL	arg+8(FP), DX	// arg
+	MOVL	$92, AX		// fcntl
+	SYSCALL
+	JCC	2(PC)
+	NEGL	AX		// caller expects negative errno
+	MOVL	AX, ret+16(FP)
+	RET
+
 // void runtime·closeonexec(int32 fd);
 TEXT runtime·closeonexec(SB),NOSPLIT,$0
 	MOVL	fd+0(FP), DI	// fd
diff --git a/src/runtime/sys_freebsd_386.s b/src/runtime/sys_freebsd_386.s
index 4e0bc9b08c..55c299f36f 100644
--- a/src/runtime/sys_freebsd_386.s
+++ b/src/runtime/sys_freebsd_386.s
@@ -451,6 +451,15 @@ TEXT runtime·kevent(SB),NOSPLIT,$0
 	MOVL	AX, ret+24(FP)
 	RET
 
+// func fcntl(fd, cmd, arg int32) int32
+TEXT runtime·fcntl(SB),NOSPLIT,$-4
+	MOVL	$SYS_fcntl, AX
+	INT	$0x80
+	JAE	2(PC)
+	NEGL	AX			// caller expects negative errno
+	MOVL	AX, ret+12(FP)
+	RET
+
 // int32 runtime·closeonexec(int32 fd);
 TEXT runtime·closeonexec(SB),NOSPLIT,$32
 	MOVL	$SYS_fcntl, AX
diff --git a/src/runtime/sys_freebsd_amd64.s b/src/runtime/sys_freebsd_amd64.s
index 26242d545a..b57bd2e920 100644
--- a/src/runtime/sys_freebsd_amd64.s
+++ b/src/runtime/sys_freebsd_amd64.s
@@ -548,6 +548,18 @@ TEXT runtime·kevent(SB),NOSPLIT,$0
 	MOVL	AX, ret+48(FP)
 	RET
 
+// func fcntl(fd, cmd, arg int32) int32
+TEXT runtime·fcntl(SB),NOSPLIT,$0
+	MOVL	fd+0(FP), DI	// fd
+	MOVL	cmd+4(FP), SI	// cmd
+	MOVL	arg+8(FP), DX	// arg
+	MOVL	$SYS_fcntl, AX
+	SYSCALL
+	JCC	2(PC)
+	NEGQ	AX		// caller expects negative errno
+	MOVL	AX, ret+16(FP)
+	RET
+
 // void runtime·closeonexec(int32 fd);
 TEXT runtime·closeonexec(SB),NOSPLIT,$0
 	MOVL	fd+0(FP), DI	// fd
diff --git a/src/runtime/sys_freebsd_arm.s b/src/runtime/sys_freebsd_arm.s
index a3fee1426c..2da092ad8e 100644
--- a/src/runtime/sys_freebsd_arm.s
+++ b/src/runtime/sys_freebsd_arm.s
@@ -387,6 +387,17 @@ TEXT runtime·kevent(SB),NOSPLIT,$0
 	MOVW	R0, ret+24(FP)
 	RET
 
+// func fcntl(fd, cmd, arg int32) int32
+TEXT runtime·fcntl(SB),NOSPLIT,$0
+	MOVW fd+0(FP), R0	// fd
+	MOVW cmd+4(FP), R1	// cmd
+	MOVW arg+8(FP), R2	// arg
+	MOVW $SYS_fcntl, R7
+	SWI $0
+	RSB.CS $0, R0		// caller expects negative errno
+	MOVW R0, ret+12(FP)
+	RET
+
 // void runtime·closeonexec(int32 fd)
 TEXT runtime·closeonexec(SB),NOSPLIT,$0
 	MOVW fd+0(FP), R0	// fd
diff --git a/src/runtime/sys_freebsd_arm64.s b/src/runtime/sys_freebsd_arm64.s
index 3b2805311f..0483b36892 100644
--- a/src/runtime/sys_freebsd_arm64.s
+++ b/src/runtime/sys_freebsd_arm64.s
@@ -439,6 +439,19 @@ ok:
 	MOVW	R0, ret+48(FP)
 	RET
 
+// func fcntl(fd, cmd, arg int32) int32
+TEXT runtime·fcntl(SB),NOSPLIT,$0
+	MOVW	fd+0(FP), R0
+	MOVW	cmd+4(FP), R1
+	MOVW	arg+8(FP), R2
+	MOVD	$SYS_fcntl, R8
+	SVC
+	BCC	ok
+	NEG	R0, R0		// caller expects negative errno
+ok:
+	MOVW	R0, ret+16(FP)
+	RET
+
 // func closeonexec(fd int32)
 TEXT runtime·closeonexec(SB),NOSPLIT|NOFRAME,$0
 	MOVW	fd+0(FP), R0
diff --git a/src/runtime/sys_freebsd_riscv64.s b/src/runtime/sys_freebsd_riscv64.s
index 30deed2573..0d3a0a83fb 100644
--- a/src/runtime/sys_freebsd_riscv64.s
+++ b/src/runtime/sys_freebsd_riscv64.s
@@ -420,6 +420,19 @@ ok:
 	MOVW	A0, ret+48(FP)
 	RET
 
+// func fcntl(fd, cmd, arg int32) int32
+TEXT runtime·fcntl(SB),NOSPLIT,$0
+	MOVW	fd+0(FP), A0
+	MOVW	cmd+4(FP), A1
+	MOVW	arg+8(FP), A2
+	MOV	$SYS_fcntl, T0
+	ECALL
+	BEQ	T0, ZERO, ok
+	NEG	A0, A0		// caller expects negative errno
+ok:
+	MOVW	A0, ret+16(FP)
+	RET
+
 // func closeonexec(fd int32)
 TEXT runtime·closeonexec(SB),NOSPLIT|NOFRAME,$0
 	MOVW	fd+0(FP), A0
diff --git a/src/runtime/sys_netbsd_386.s b/src/runtime/sys_netbsd_386.s
index 7be18c61d8..a05e1d4478 100644
--- a/src/runtime/sys_netbsd_386.s
+++ b/src/runtime/sys_netbsd_386.s
@@ -457,6 +457,15 @@ TEXT runtime·kevent(SB),NOSPLIT,$0
 	MOVL	AX, ret+24(FP)
 	RET
 
+// func fcntl(fd, cmd, arg int32) int32
+TEXT runtime·fcntl(SB),NOSPLIT,$-4
+	MOVL	$SYS_fcntl, AX
+	INT	$0x80
+	JAE	2(PC)
+	NEGL	AX			// caller expects negative errno
+	MOVL	AX, ret+12(FP)
+	RET
+
 // int32 runtime·closeonexec(int32 fd)
 TEXT runtime·closeonexec(SB),NOSPLIT,$32
 	MOVL	$SYS_fcntl, AX
diff --git a/src/runtime/sys_netbsd_amd64.s b/src/runtime/sys_netbsd_amd64.s
index 721ffd614c..79a50be8e6 100644
--- a/src/runtime/sys_netbsd_amd64.s
+++ b/src/runtime/sys_netbsd_amd64.s
@@ -432,6 +432,18 @@ TEXT runtime·kevent(SB),NOSPLIT,$0
 	MOVL	AX, ret+48(FP)
 	RET
 
+// func fcntl(fd, cmd, arg int32) int2
+TEXT runtime·fcntl(SB),NOSPLIT,$0
+	MOVL	fd+0(FP), DI	// fd
+	MOVL	cmd+4(FP), SI	// cmd
+	MOVL	arg+8(FP), DX	// arg
+	MOVL	$SYS_fcntl, AX
+	SYSCALL
+	JCC	2(PC)
+	NEGQ	AX		// caller expects negative errno
+	MOVL	AX, ret+16(FP)
+	RET
+
 // void runtime·closeonexec(int32 fd)
 TEXT runtime·closeonexec(SB),NOSPLIT,$0
 	MOVL	fd+0(FP), DI	// fd
diff --git a/src/runtime/sys_netbsd_arm.s b/src/runtime/sys_netbsd_arm.s
index 62fa852add..f9cbcb6df1 100644
--- a/src/runtime/sys_netbsd_arm.s
+++ b/src/runtime/sys_netbsd_arm.s
@@ -398,6 +398,16 @@ TEXT runtime·kevent(SB),NOSPLIT,$8
 	MOVW	R0, ret+24(FP)
 	RET
 
+// func fcntl(fd, cmd, args int32) int32
+TEXT runtime·fcntl(SB),NOSPLIT,$0
+	MOVW fd+0(FP), R0
+	MOVW cmd+4(FP), R1
+	MOVW arg+8(FP), R2
+	SWI $SYS_fcntl
+	RSB.CS $0, R0		// caller expects negative errno
+	MOVW R0, ret+12(FP)
+	RET
+
 // void runtime·closeonexec(int32 fd)
 TEXT runtime·closeonexec(SB),NOSPLIT,$0
 	MOVW fd+0(FP), R0	// fd
diff --git a/src/runtime/sys_netbsd_arm64.s b/src/runtime/sys_netbsd_arm64.s
index fffd18f8b0..37c0af2880 100644
--- a/src/runtime/sys_netbsd_arm64.s
+++ b/src/runtime/sys_netbsd_arm64.s
@@ -416,6 +416,18 @@ ok:
 	MOVW	R0, ret+48(FP)
 	RET
 
+// func fcntl(fd, cmd, arg int32) int32
+TEXT runtime·fcntl(SB),NOSPLIT,$0
+	MOVW	fd+0(FP), R0	// fd
+	MOVW	cmd+4(FP), R1	// cmd
+	MOVW	arg+8(FP), R2	// arg
+	SVC	$SYS_fcntl
+	BCC	ok
+	NEG	R0, R0		// caller expects negative errno
+ok:
+	MOVW	R0, ret+16(FP)
+	RET
+
 // void runtime·closeonexec(int32 fd)
 TEXT runtime·closeonexec(SB),NOSPLIT,$0
 	MOVW	fd+0(FP), R0		// arg 1 - fd
diff --git a/src/runtime/sys_openbsd_386.s b/src/runtime/sys_openbsd_386.s
index 963678a2c3..3e5dbc2b0a 100644
--- a/src/runtime/sys_openbsd_386.s
+++ b/src/runtime/sys_openbsd_386.s
@@ -542,6 +542,12 @@ TEXT runtime·fcntl_trampoline(SB),NOSPLIT,$0
 	MOVL	CX, 8(SP)		// arg 3 - arg
 	MOVL	$0, 12(SP)		// vararg
 	CALL	libc_fcntl(SB)
+	CMPL	AX, $-1
+	JNE	noerr
+	CALL	libc_errno(SB)
+	MOVL	(AX), AX
+	NEGL	AX			// caller expects negative errno
+noerr:
 	MOVL	BP, SP
 	POPL	BP
 	RET
diff --git a/src/runtime/sys_openbsd_amd64.s b/src/runtime/sys_openbsd_amd64.s
index d3e87c2372..47edde7def 100644
--- a/src/runtime/sys_openbsd_amd64.s
+++ b/src/runtime/sys_openbsd_amd64.s
@@ -309,6 +309,12 @@ TEXT runtime·fcntl_trampoline(SB),NOSPLIT,$0
 	MOVL	0(DI), DI		// arg 1 fd
 	XORL	AX, AX			// vararg: say "no float args"
 	CALL	libc_fcntl(SB)
+	TESTL	AX, AX
+	JGE	noerr
+	CALL	libc_errno(SB)
+	MOVL	(AX), AX
+	NEGL	AX			// caller expects negative errno value
+noerr:
 	RET
 
 TEXT runtime·sigaction_trampoline(SB),NOSPLIT,$0
diff --git a/src/runtime/sys_openbsd_arm.s b/src/runtime/sys_openbsd_arm.s
index e03cfb52f6..3568d4eb94 100644
--- a/src/runtime/sys_openbsd_arm.s
+++ b/src/runtime/sys_openbsd_arm.s
@@ -424,6 +424,12 @@ TEXT runtime·fcntl_trampoline(SB),NOSPLIT,$0
 	MOVW	R2, 0(R13)
 	MOVW	0(R0), R0		// arg 1 fd
 	BL	libc_fcntl(SB)
+	CMP	$-1, R0
+	BNE	noerr
+	BL	libc_errno(SB)
+	MOVW	(R0), R0
+	RSB.CS	$0, R0			// caller expects negative errno
+noerr:
 	MOVW	R9, R13
 	RET
 
diff --git a/src/runtime/sys_openbsd_arm64.s b/src/runtime/sys_openbsd_arm64.s
index 97005eac14..87a0b5c4de 100644
--- a/src/runtime/sys_openbsd_arm64.s
+++ b/src/runtime/sys_openbsd_arm64.s
@@ -306,6 +306,12 @@ TEXT runtime·fcntl_trampoline(SB),NOSPLIT,$0
 	MOVW	0(R0), R0		// arg 1 - fd
 	MOVD	$0, R3			// vararg
 	CALL	libc_fcntl(SB)
+	CMP	$-1, R0
+	BNE	noerr
+	CALL	libc_errno(SB)
+	MOVW	(R0), R0
+	NEG	R0, R0			// caller expects negative errno value
+noerr:
 	RET
 
 TEXT runtime·sigaction_trampoline(SB),NOSPLIT,$0
diff --git a/src/runtime/sys_openbsd_mips64.s b/src/runtime/sys_openbsd_mips64.s
index affd586742..0ba53cd37d 100644
--- a/src/runtime/sys_openbsd_mips64.s
+++ b/src/runtime/sys_openbsd_mips64.s
@@ -364,6 +364,18 @@ TEXT runtime·kevent(SB),NOSPLIT,$0
 	MOVW	R2, ret+48(FP)
 	RET
 
+// func fcntl(fd, cmd, arg int32) int32
+TEXT runtime·fcntl(SB),NOSPLIT,$0
+	MOVW	fd+0(FP), R4	// fd
+	MOVW	cmd+4(FP), R5	// cmd
+	MOVW	arg+8(FP), R6	// arg
+	MOVV	$92, R2		// sys_fcntl
+	SYSCALL
+	BEQ	R7, 2(PC)
+	SUBVU	R2, R0, R2	// caller expects negative errno
+	MOVW	R2, ret+16(FP)
+	RET
+
 // func closeonexec(fd int32)
 TEXT runtime·closeonexec(SB),NOSPLIT,$0
 	MOVW	fd+0(FP), R4		// arg 1 - fd