[release-branch.go1.19] runtime: change fcntl to return two values

Separate the result and the errno value, rather than assuming
that the result can never be negative.

Change-Id: Ib01a70a3d46285aa77e95371cdde74e1504e7c12
Reviewed-on: https://go-review.googlesource.com/c/go/+/496416
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-on: https://go-review.googlesource.com/c/go/+/497136
Run-TryBot: Roland Shoemaker <roland@golang.org>
Auto-Submit: Heschi Kreinick <heschi@google.com>

26 files changed, 167 insertions, 101 deletions

diff --git a/src/runtime/nbpipe_test.go b/src/runtime/nbpipe_test.go
index bb21003c35..337b8e5914 100644
--- a/src/runtime/nbpipe_test.go
+++ b/src/runtime/nbpipe_test.go
@@ -31,11 +31,11 @@ func TestNonblockingPipe(t *testing.T) {
 	if runtime.Close(r) != 0 {
 		t.Fatalf("Close(%d) failed", r)
 	}
-	val := runtime.Fcntl(r, syscall.F_GETFD, 0)
-	if val >= 0 {
+	val, errno := runtime.Fcntl(r, syscall.F_GETFD, 0)
+	if val != -1 {
 		t.Errorf("Fcntl succeeded unexpectedly")
-	} else if syscall.Errno(-val) != syscall.EBADF {
-		t.Errorf("Fcntl failed with error %v, expected %v", -val, syscall.EBADF)
+	} else if syscall.Errno(errno) != syscall.EBADF {
+		t.Errorf("Fcntl failed with error %v, expected %v", syscall.Errno(errno), syscall.EBADF)
 	}
 }
 
@@ -55,9 +55,9 @@ func checkIsPipe(t *testing.T, r, w int32) {
 
 func checkNonblocking(t *testing.T, fd int32, name string) {
 	t.Helper()
-	flags := runtime.Fcntl(fd, syscall.F_GETFL, 0)
-	if flags < 0 {
-		t.Errorf("fcntl(%s, F_GETFL) failed: %v", name, syscall.Errno(-flags))
+	flags, errno := runtime.Fcntl(fd, syscall.F_GETFL, 0)
+	if flags == -1 {
+		t.Errorf("fcntl(%s, F_GETFL) failed: %v", name, syscall.Errno(errno))
 	} else if flags&syscall.O_NONBLOCK == 0 {
 		t.Errorf("O_NONBLOCK not set in %s flags %#x", name, flags)
 	}
@@ -65,9 +65,9 @@ func checkNonblocking(t *testing.T, fd int32, name string) {
 
 func checkCloseonexec(t *testing.T, fd int32, name string) {
 	t.Helper()
-	flags := runtime.Fcntl(fd, syscall.F_GETFD, 0)
-	if flags < 0 {
-		t.Errorf("fcntl(%s, F_GETFD) failed: %v", name, syscall.Errno(flags))
+	flags, errno := runtime.Fcntl(fd, syscall.F_GETFD, 0)
+	if flags == -1 {
+		t.Errorf("fcntl(%s, F_GETFD) failed: %v", name, syscall.Errno(errno))
 	} else if flags&syscall.FD_CLOEXEC == 0 {
 		t.Errorf("FD_CLOEXEC not set in %s flags %#x", name, flags)
 	}
diff --git a/src/runtime/os3_solaris.go b/src/runtime/os3_solaris.go
index 783a294976..150843ab46 100644
--- a/src/runtime/os3_solaris.go
+++ b/src/runtime/os3_solaris.go
@@ -569,12 +569,9 @@ func pipe2(flags int32) (r, w int32, errno int32) {
 }
 
 //go:nosplit
-func fcntl(fd, cmd, arg int32) int32 {
+func fcntl(fd, cmd, arg int32) (ret int32, errno int32) {
 	r1, err := sysvicall3Err(&libc_fcntl, uintptr(fd), uintptr(cmd), uintptr(arg))
-	if r := int32(r1); r >= 0 {
-		return r
-	}
-	return -int32(err)
+	return int32(r1), int32(err)
 }
 
 //go:nosplit
diff --git a/src/runtime/os_aix.go b/src/runtime/os_aix.go
index 66b4d94cf2..21f7cea908 100644
--- a/src/runtime/os_aix.go
+++ b/src/runtime/os_aix.go
@@ -361,12 +361,9 @@ func walltime() (sec int64, nsec int32) {
 }
 
 //go:nosplit
-func fcntl(fd, cmd, arg int32) int32 {
+func fcntl(fd, cmd, arg int32) (int32, int32) {
 	r, errno := syscall3(&libc_fcntl, uintptr(fd), uintptr(cmd), uintptr(arg))
-	if int32(r) < 0 {
-		return -int32(errno)
-	}
-	return int32(r)
+	return int32(r), int32(errno)
 }
 
 //go:nosplit
@@ -376,8 +373,10 @@ func closeonexec(fd int32) {
 
 //go:nosplit
 func setNonblock(fd int32) {
-	flags := fcntl(fd, _F_GETFL, 0)
-	fcntl(fd, _F_SETFL, flags|_O_NONBLOCK)
+	flags, _ := fcntl(fd, _F_GETFL, 0)
+	if flags != -1 {
+		fcntl(fd, _F_SETFL, flags|_O_NONBLOCK)
+	}
 }
 
 // sigPerThreadSyscall is only used on linux, so we assign a bogus signal
diff --git a/src/runtime/os_dragonfly.go b/src/runtime/os_dragonfly.go
index 728d2bcdab..a73db29734 100644
--- a/src/runtime/os_dragonfly.go
+++ b/src/runtime/os_dragonfly.go
@@ -63,7 +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 fcntl(fd, cmd, arg int32) (ret int32, errno 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 94a6de2cdf..128e8e3b8b 100644
--- a/src/runtime/os_freebsd.go
+++ b/src/runtime/os_freebsd.go
@@ -48,7 +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 fcntl(fd, cmd, arg int32) (ret int32, errno 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 af4a0922c9..3091a90d59 100644
--- a/src/runtime/os_linux.go
+++ b/src/runtime/os_linux.go
@@ -457,13 +457,9 @@ 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
+func fcntl(fd, cmd, arg int32) (ret int32, errno int32) {
+	r, _, err := syscall.Syscall6(syscall.SYS_FCNTL, uintptr(fd), uintptr(cmd), uintptr(arg), 0, 0, 0)
+	return int32(r), int32(err)
 }
 
 const (
diff --git a/src/runtime/os_netbsd.go b/src/runtime/os_netbsd.go
index 34f43ddecb..8dbde23b2b 100644
--- a/src/runtime/os_netbsd.go
+++ b/src/runtime/os_netbsd.go
@@ -79,7 +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 fcntl(fd, cmd, arg int32) (ret int32, errno int32)
 func closeonexec(fd int32)
 
 const (
diff --git a/src/runtime/os_openbsd_syscall2.go b/src/runtime/os_openbsd_syscall2.go
index c2a43bac8b..b56190abe4 100644
--- a/src/runtime/os_openbsd_syscall2.go
+++ b/src/runtime/os_openbsd_syscall2.go
@@ -95,7 +95,7 @@ func nanotime1() int64
 //go:noescape
 func sigaltstack(new, old *stackt)
 
-func fcntl(fd, cmd, arg int32) int32
+func fcntl(fd, cmd, arg int32) (ret int32, errno int32)
 func closeonexec(fd int32)
 
 func walltime() (sec int64, nsec int32)
diff --git a/src/runtime/sys_darwin.go b/src/runtime/sys_darwin.go
index 88af894409..03a2294e5e 100644
--- a/src/runtime/sys_darwin.go
+++ b/src/runtime/sys_darwin.go
@@ -382,8 +382,13 @@ func sysctlbyname_trampoline()
 
 //go:nosplit
 //go:cgo_unsafe_args
-func fcntl(fd, cmd, arg int32) int32 {
-	return libcCall(unsafe.Pointer(abi.FuncPCABI0(fcntl_trampoline)), unsafe.Pointer(&fd))
+func fcntl(fd, cmd, arg int32) (ret int32, errno int32) {
+	args := struct {
+		fd, cmd, arg int32
+		ret, errno   int32
+	}{fd, cmd, arg, 0, 0}
+	libcCall(unsafe.Pointer(abi.FuncPCABI0(fcntl_trampoline)), unsafe.Pointer(&args))
+	return args.ret, args.errno
 }
 func fcntl_trampoline()
 
@@ -485,8 +490,10 @@ func closeonexec(fd int32) {
 
 //go:nosplit
 func setNonblock(fd int32) {
-	flags := fcntl(fd, _F_GETFL, 0)
-	fcntl(fd, _F_SETFL, flags|_O_NONBLOCK)
+	flags, _ := fcntl(fd, _F_GETFL, 0)
+	if flags != -1 {
+		fcntl(fd, _F_SETFL, flags|_O_NONBLOCK)
+	}
 }
 
 // Tell the linker that the libc_* functions are to be found
diff --git a/src/runtime/sys_darwin_amd64.s b/src/runtime/sys_darwin_amd64.s
index 3ba673c5ec..b9c2298d77 100644
--- a/src/runtime/sys_darwin_amd64.s
+++ b/src/runtime/sys_darwin_amd64.s
@@ -432,17 +432,21 @@ ok:
 TEXT runtime·fcntl_trampoline(SB),NOSPLIT,$0
 	PUSHQ	BP
 	MOVQ	SP, BP
-	MOVL	4(DI), SI		// arg 2 cmd
-	MOVL	8(DI), DX		// arg 3 arg
-	MOVL	0(DI), DI		// arg 1 fd
+	MOVQ	DI, BX
+	MOVL	0(BX), DI		// arg 1 fd
+	MOVL	4(BX), SI		// arg 2 cmd
+	MOVL	8(BX), DX		// arg 3 arg
 	XORL	AX, AX			// vararg: say "no float args"
 	CALL	libc_fcntl(SB)
-	TESTL	AX, AX
-	JGT	noerr
+	XORL	DX, DX
+	CMPQ	AX, $-1
+	JNE	noerr
 	CALL	libc_error(SB)
-	MOVL	(AX), AX
-	NEGL	AX			// caller expects negative errno value
+	MOVL	(AX), DX
+	MOVL	$-1, AX
 noerr:
+	MOVL	AX, 12(BX)
+	MOVL	DX, 16(BX)
 	POPQ	BP
 	RET
 
diff --git a/src/runtime/sys_darwin_arm64.s b/src/runtime/sys_darwin_arm64.s
index 5f8e824395..474aedfdbf 100644
--- a/src/runtime/sys_darwin_arm64.s
+++ b/src/runtime/sys_darwin_arm64.s
@@ -309,18 +309,22 @@ ok:
 
 TEXT runtime·fcntl_trampoline(SB),NOSPLIT,$0
 	SUB	$16, RSP
-	MOVW	4(R0), R1	// arg 2 cmd
-	MOVW	8(R0), R2	// arg 3 arg
+	MOVD	R0, R19
+	MOVW	0(R19), R0	// arg 1 fd
+	MOVW	4(R19), R1	// arg 2 cmd
+	MOVW	8(R19), R2	// arg 3 arg
 	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
+	MOVD	$0, R1
+	MOVD	$-1, R2
+	CMP	R0, R2
 	BNE	noerr
 	BL	libc_error(SB)
-	MOVW	(R0), R0
-	NEG	R0, R0		// caller expects negative errno value
+	MOVW	(R0), R1
+	MOVW	$-1, R0
 noerr:
+	MOVW	R0, 12(R19)
+	MOVW	R1, 16(R19)
 	ADD	$16, RSP
 	RET
 
diff --git a/src/runtime/sys_dragonfly_amd64.s b/src/runtime/sys_dragonfly_amd64.s
index e3d85ab062..958d712cd3 100644
--- a/src/runtime/sys_dragonfly_amd64.s
+++ b/src/runtime/sys_dragonfly_amd64.s
@@ -387,16 +387,20 @@ TEXT runtime·kevent(SB),NOSPLIT,$0
 	MOVL	AX, ret+48(FP)
 	RET
 
-// func fcntl(fd, cmd, arg int32) int32
+// func fcntl(fd, cmd, arg int32) (ret int32, errno 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
+	JCC	noerr
+	MOVL	$-1, ret+16(FP)
+	MOVL	AX, errno+20(FP)
+	RET
+noerr:
 	MOVL	AX, ret+16(FP)
+	MOVL	$0, errno+20(FP)
 	RET
 
 // void runtime·closeonexec(int32 fd);
diff --git a/src/runtime/sys_freebsd_386.s b/src/runtime/sys_freebsd_386.s
index 3375fc1fae..c99172dff7 100644
--- a/src/runtime/sys_freebsd_386.s
+++ b/src/runtime/sys_freebsd_386.s
@@ -415,13 +415,17 @@ TEXT runtime·kevent(SB),NOSPLIT,$0
 	MOVL	AX, ret+24(FP)
 	RET
 
-// func fcntl(fd, cmd, arg int32) int32
+// func fcntl(fd, cmd, arg int32) (int32, int32)
 TEXT runtime·fcntl(SB),NOSPLIT,$-4
 	MOVL	$92, AX
 	INT	$0x80
-	JAE	2(PC)
-	NEGL	AX			// caller expects negative errno
+	JAE	noerr
+	MOVL	$-1, ret+12(FP)
+	MOVL	AX, errno+16(FP)
+	RET
+noerr:
 	MOVL	AX, ret+12(FP)
+	MOVL	$0, errno+16(FP)
 	RET
 
 // int32 runtime·closeonexec(int32 fd);
diff --git a/src/runtime/sys_freebsd_amd64.s b/src/runtime/sys_freebsd_amd64.s
index 55e7e250ae..d769577ed4 100644
--- a/src/runtime/sys_freebsd_amd64.s
+++ b/src/runtime/sys_freebsd_amd64.s
@@ -483,16 +483,20 @@ TEXT runtime·kevent(SB),NOSPLIT,$0
 	MOVL	AX, ret+48(FP)
 	RET
 
-// func fcntl(fd, cmd, arg int32) int32
+// func fcntl(fd, cmd, arg int32) (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
 	SYSCALL
-	JCC	2(PC)
-	NEGQ	AX		// caller expects negative errno
+	JCC	noerr
+	MOVL	$-1, ret+16(FP)
+	MOVL	AX, errno+20(FP)
+	RET
+noerr:
 	MOVL	AX, ret+16(FP)
+	MOVL	$0, errno+20(FP)
 	RET
 
 // void runtime·closeonexec(int32 fd);
diff --git a/src/runtime/sys_freebsd_arm.s b/src/runtime/sys_freebsd_arm.s
index 725303a8ac..d4a8a09bb8 100644
--- a/src/runtime/sys_freebsd_arm.s
+++ b/src/runtime/sys_freebsd_arm.s
@@ -387,15 +387,18 @@ TEXT runtime·kevent(SB),NOSPLIT,$0
 	MOVW	R0, ret+24(FP)
 	RET
 
-// func fcntl(fd, cmd, arg int32) int32
+// func fcntl(fd, cmd, arg int32) (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 $0, R1
+	MOVW.CS R0, R1
+	MOVW.CS $-1, R0
 	MOVW R0, ret+12(FP)
+	MOVW R1, errno+16(FP)
 	RET
 
 // void runtime·closeonexec(int32 fd)
diff --git a/src/runtime/sys_freebsd_arm64.s b/src/runtime/sys_freebsd_arm64.s
index 4521ac61e4..799be4bd5d 100644
--- a/src/runtime/sys_freebsd_arm64.s
+++ b/src/runtime/sys_freebsd_arm64.s
@@ -444,17 +444,21 @@ ok:
 	MOVW	R0, ret+48(FP)
 	RET
 
-// func fcntl(fd, cmd, arg int32) int32
+// func fcntl(fd, cmd, arg int32) (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:
+	BCC	noerr
+	MOVW	$-1, R1
+	MOVW	R1, ret+16(FP)
+	MOVW	R0, errno+20(FP)
+	RET
+noerr:
 	MOVW	R0, ret+16(FP)
+	MOVW	$0, errno+20(FP)
 	RET
 
 // func closeonexec(fd int32)
diff --git a/src/runtime/sys_netbsd_386.s b/src/runtime/sys_netbsd_386.s
index a05e1d4478..e649fb13cb 100644
--- a/src/runtime/sys_netbsd_386.s
+++ b/src/runtime/sys_netbsd_386.s
@@ -457,13 +457,17 @@ TEXT runtime·kevent(SB),NOSPLIT,$0
 	MOVL	AX, ret+24(FP)
 	RET
 
-// func fcntl(fd, cmd, arg int32) int32
+// func fcntl(fd, cmd, arg int32) (int32, int32)
 TEXT runtime·fcntl(SB),NOSPLIT,$-4
 	MOVL	$SYS_fcntl, AX
 	INT	$0x80
-	JAE	2(PC)
-	NEGL	AX			// caller expects negative errno
+	JAE	noerr
+	MOVL	$-1, ret+12(FP)
+	MOVL	AX, errno+16(FP)
+	RET
+noerr:
 	MOVL	AX, ret+12(FP)
+	MOVL	$0, errno+16(FP)
 	RET
 
 // int32 runtime·closeonexec(int32 fd)
diff --git a/src/runtime/sys_netbsd_amd64.s b/src/runtime/sys_netbsd_amd64.s
index 368eef56ed..2c2d97c105 100644
--- a/src/runtime/sys_netbsd_amd64.s
+++ b/src/runtime/sys_netbsd_amd64.s
@@ -434,16 +434,20 @@ TEXT runtime·kevent(SB),NOSPLIT,$0
 	MOVL	AX, ret+48(FP)
 	RET
 
-// func fcntl(fd, cmd, arg int32) int2
+// func fcntl(fd, cmd, arg int32) (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
+	JCC	noerr
+	MOVL	$-1, ret+16(FP)
+	MOVL	AX, errno+20(FP)
+	RET
+noerr:
 	MOVL	AX, ret+16(FP)
+	MOVL	$0, errno+20(FP)
 	RET
 
 // void runtime·closeonexec(int32 fd)
diff --git a/src/runtime/sys_netbsd_arm.s b/src/runtime/sys_netbsd_arm.s
index f9cbcb6df1..9d969592c4 100644
--- a/src/runtime/sys_netbsd_arm.s
+++ b/src/runtime/sys_netbsd_arm.s
@@ -404,8 +404,11 @@ TEXT runtime·fcntl(SB),NOSPLIT,$0
 	MOVW cmd+4(FP), R1
 	MOVW arg+8(FP), R2
 	SWI $SYS_fcntl
-	RSB.CS $0, R0		// caller expects negative errno
+	MOVW $0, R1
+	MOVW.CS R0, R1
+	MOVW.CS $-1, R0
 	MOVW R0, ret+12(FP)
+	MOVW R1, errno+16(FP)
 	RET
 
 // void runtime·closeonexec(int32 fd)
diff --git a/src/runtime/sys_netbsd_arm64.s b/src/runtime/sys_netbsd_arm64.s
index d27133550a..0cd9262750 100644
--- a/src/runtime/sys_netbsd_arm64.s
+++ b/src/runtime/sys_netbsd_arm64.s
@@ -421,16 +421,20 @@ ok:
 	MOVW	R0, ret+48(FP)
 	RET
 
-// func fcntl(fd, cmd, arg int32) int32
+// func fcntl(fd, cmd, arg int32) (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:
+	BCC	noerr
+	MOVW	$-1, R1
+	MOVW	R1, ret+16(FP)
+	MOVW	R0, errno+20(FP)
+	RET
+noerr:
 	MOVW	R0, ret+16(FP)
+	MOVW	$0, errno+20(FP)
 	RET
 
 // void runtime·closeonexec(int32 fd)
diff --git a/src/runtime/sys_openbsd2.go b/src/runtime/sys_openbsd2.go
index f755cd528c..4324049898 100644
--- a/src/runtime/sys_openbsd2.go
+++ b/src/runtime/sys_openbsd2.go
@@ -161,8 +161,13 @@ func sysctl_trampoline()
 
 //go:nosplit
 //go:cgo_unsafe_args
-func fcntl(fd, cmd, arg int32) int32 {
-	return libcCall(unsafe.Pointer(abi.FuncPCABI0(fcntl_trampoline)), unsafe.Pointer(&fd))
+func fcntl(fd, cmd, arg int32) (ret int32, errno int32) {
+	args := struct {
+		fd, cmd, arg int32
+		ret, errno   int32
+	}{fd, cmd, arg, 0, 0}
+	libcCall(unsafe.Pointer(abi.FuncPCABI0(fcntl_trampoline)), unsafe.Pointer(&args))
+	return args.ret, args.errno
 }
 func fcntl_trampoline()
 
diff --git a/src/runtime/sys_openbsd_386.s b/src/runtime/sys_openbsd_386.s
index 3e5dbc2b0a..d0d9926ff9 100644
--- a/src/runtime/sys_openbsd_386.s
+++ b/src/runtime/sys_openbsd_386.s
@@ -542,12 +542,16 @@ TEXT runtime·fcntl_trampoline(SB),NOSPLIT,$0
 	MOVL	CX, 8(SP)		// arg 3 - arg
 	MOVL	$0, 12(SP)		// vararg
 	CALL	libc_fcntl(SB)
+	MOVL	$0, BX
 	CMPL	AX, $-1
 	JNE	noerr
 	CALL	libc_errno(SB)
-	MOVL	(AX), AX
-	NEGL	AX			// caller expects negative errno
+	MOVL	(AX), BX
+	MOVL	$-1, AX
 noerr:
+	MOVL	24(SP), DX		// pointer to args
+	MOVL	AX, 12(DX)
+	MOVL	BX, 16(DX)
 	MOVL	BP, SP
 	POPL	BP
 	RET
diff --git a/src/runtime/sys_openbsd_amd64.s b/src/runtime/sys_openbsd_amd64.s
index 35a57c026b..893a92e26f 100644
--- a/src/runtime/sys_openbsd_amd64.s
+++ b/src/runtime/sys_openbsd_amd64.s
@@ -388,17 +388,21 @@ noerr:
 TEXT runtime·fcntl_trampoline(SB),NOSPLIT,$0
 	PUSHQ	BP
 	MOVQ	SP, BP
-	MOVL	4(DI), SI		// arg 2 cmd
-	MOVL	8(DI), DX		// arg 3 arg
-	MOVL	0(DI), DI		// arg 1 fd
+	MOVQ	DI, BX
+	MOVL	0(BX), DI		// arg 1 fd
+	MOVL	4(BX), SI		// arg 2 cmd
+	MOVL	8(BX), DX		// arg 3 arg
 	XORL	AX, AX			// vararg: say "no float args"
 	CALL	libc_fcntl(SB)
-	TESTL	AX, AX
-	JGE	noerr
+	XORL	DX, DX
+	CMPL	AX, $-1
+	JNE	noerr
 	CALL	libc_errno(SB)
-	MOVL	(AX), AX
-	NEGL	AX			// caller expects negative errno value
+	MOVL	(AX), DX
+	MOVL	$-1, AX
 noerr:
+	MOVL	AX, 12(BX)
+	MOVL	DX, 16(BX)
 	POPQ	BP
 	RET
 
diff --git a/src/runtime/sys_openbsd_arm.s b/src/runtime/sys_openbsd_arm.s
index 3568d4eb94..fc04cf11a4 100644
--- a/src/runtime/sys_openbsd_arm.s
+++ b/src/runtime/sys_openbsd_arm.s
@@ -419,17 +419,21 @@ TEXT runtime·fcntl_trampoline(SB),NOSPLIT,$0
 	MOVW	R13, R9
 	SUB	$8, R13
 	BIC     $0x7, R13		// align for ELF ABI
-	MOVW	4(R0), R1		// arg 2 cmd
-	MOVW	8(R0), R2		// arg 3 arg (vararg, on stack)
+	MOVW	R0, R8
+	MOVW	0(R8), R0		// arg 1 fd
+	MOVW	4(R8), R1		// arg 2 cmd
+	MOVW	8(R8), R2		// arg 3 arg (vararg, on stack)
 	MOVW	R2, 0(R13)
-	MOVW	0(R0), R0		// arg 1 fd
 	BL	libc_fcntl(SB)
+	MOVW	$0, R1
 	CMP	$-1, R0
 	BNE	noerr
 	BL	libc_errno(SB)
-	MOVW	(R0), R0
-	RSB.CS	$0, R0			// caller expects negative errno
+	MOVW	(R0), R1
+	MOVW	$-1, R0
 noerr:
+	MOVW	R0, 12(R8)
+	MOVW	R1, 16(R8)
 	MOVW	R9, R13
 	RET
 
diff --git a/src/runtime/sys_openbsd_arm64.s b/src/runtime/sys_openbsd_arm64.s
index 0bd801ff7a..c40889861a 100644
--- a/src/runtime/sys_openbsd_arm64.s
+++ b/src/runtime/sys_openbsd_arm64.s
@@ -306,17 +306,21 @@ noerr:
 	RET
 
 TEXT runtime·fcntl_trampoline(SB),NOSPLIT,$0
-	MOVW	4(R0), R1		// arg 2 - cmd
-	MOVW	8(R0), R2		// arg 3 - arg
-	MOVW	0(R0), R0		// arg 1 - fd
+	MOVD	R0, R19
+	MOVW	0(R19), R0		// arg 1 - fd
+	MOVW	4(R19), R1		// arg 2 - cmd
+	MOVW	8(R19), R2		// arg 3 - arg
 	MOVD	$0, R3			// vararg
 	CALL	libc_fcntl(SB)
+	MOVD	$0, R1
 	CMP	$-1, R0
 	BNE	noerr
 	CALL	libc_errno(SB)
-	MOVW	(R0), R0
-	NEG	R0, R0			// caller expects negative errno value
+	MOVW	(R0), R1
+	MOVW	$-1, R0
 noerr:
+	MOVW	R0, 12(R19)
+	MOVW	R1, 16(R19)
 	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 0ddcac5595..eded88d647 100644
--- a/src/runtime/sys_openbsd_mips64.s
+++ b/src/runtime/sys_openbsd_mips64.s
@@ -364,16 +364,20 @@ TEXT runtime·kevent(SB),NOSPLIT,$0
 	MOVW	R2, ret+48(FP)
 	RET
 
-// func fcntl(fd, cmd, arg int32) int32
+// func fcntl(fd, cmd, arg int32) (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
+	MOVV	$0, R4
+	BEQ	R7, noerr
+	MOVV	R2, R4
+	MOVW	$-1, R2
+noerr:
 	MOVW	R2, ret+16(FP)
+	MOVW	R4, errno+20(FP)
 	RET
 
 // func closeonexec(fd int32)