runtime: consolidate on a single closeonexec definition

Now that we implement fcntl on all Unix systems, we can
write closeonexec that uses it. This lets us remove a bunch
of assembler code.

Change-Id: If35591df535ccfc67292086a9492f0a8920e3681
Reviewed-on: https://go-review.googlesource.com/c/go/+/496081
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Auto-Submit: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>

38 files changed, 43 insertions, 221 deletions

diff --git a/src/runtime/defs1_solaris_amd64.go b/src/runtime/defs1_solaris_amd64.go
index bb53c22e06..4e541a913b 100644
--- a/src/runtime/defs1_solaris_amd64.go
+++ b/src/runtime/defs1_solaris_amd64.go
@@ -96,10 +96,8 @@ const (
 	_O_TRUNC    = 0x200
 	_O_CREAT    = 0x100
 	_O_CLOEXEC  = 0x800000
-	_FD_CLOEXEC = 0x1
 	_F_GETFL    = 0x3
 	_F_SETFL    = 0x4
-	_F_SETFD    = 0x2
 
 	_POLLIN  = 0x1
 	_POLLOUT = 0x4
diff --git a/src/runtime/defs_aix.go b/src/runtime/defs_aix.go
index 389598966a..2f28e53468 100644
--- a/src/runtime/defs_aix.go
+++ b/src/runtime/defs_aix.go
@@ -144,11 +144,9 @@ const (
 	__SC_PAGE_SIZE        = C._SC_PAGE_SIZE
 	__SC_NPROCESSORS_ONLN = C._SC_NPROCESSORS_ONLN
 
-	_F_SETFD    = C.F_SETFD
-	_F_SETFL    = C.F_SETFL
-	_F_GETFD    = C.F_GETFD
-	_F_GETFL    = C.F_GETFL
-	_FD_CLOEXEC = C.FD_CLOEXEC
+	_F_SETFL = C.F_SETFL
+	_F_GETFD = C.F_GETFD
+	_F_GETFL = C.F_GETFL
 )
 
 type sigset C.sigset_t
diff --git a/src/runtime/defs_aix_ppc64.go b/src/runtime/defs_aix_ppc64.go
index 2d25b7ce3c..8e85096939 100644
--- a/src/runtime/defs_aix_ppc64.go
+++ b/src/runtime/defs_aix_ppc64.go
@@ -101,11 +101,9 @@ const (
 	__SC_PAGE_SIZE        = 0x30
 	__SC_NPROCESSORS_ONLN = 0x48
 
-	_F_SETFD    = 0x2
-	_F_SETFL    = 0x4
-	_F_GETFD    = 0x1
-	_F_GETFL    = 0x3
-	_FD_CLOEXEC = 0x1
+	_F_SETFL = 0x4
+	_F_GETFD = 0x1
+	_F_GETFL = 0x3
 )
 
 type sigset [4]uint64
diff --git a/src/runtime/defs_darwin.go b/src/runtime/defs_darwin.go
index 89e4253f33..9c6eeee45a 100644
--- a/src/runtime/defs_darwin.go
+++ b/src/runtime/defs_darwin.go
@@ -115,10 +115,8 @@ const (
 
 	PTHREAD_CREATE_DETACHED = C.PTHREAD_CREATE_DETACHED
 
-	F_SETFD    = C.F_SETFD
-	F_GETFL    = C.F_GETFL
-	F_SETFL    = C.F_SETFL
-	FD_CLOEXEC = C.FD_CLOEXEC
+	F_GETFL = C.F_GETFL
+	F_SETFL = C.F_SETFL
 
 	O_WRONLY   = C.O_WRONLY
 	O_NONBLOCK = C.O_NONBLOCK
diff --git a/src/runtime/defs_darwin_amd64.go b/src/runtime/defs_darwin_amd64.go
index 84e6f37203..fc7de3330a 100644
--- a/src/runtime/defs_darwin_amd64.go
+++ b/src/runtime/defs_darwin_amd64.go
@@ -94,10 +94,8 @@ const (
 
 	_PTHREAD_CREATE_DETACHED = 0x2
 
-	_F_SETFD    = 0x2
-	_F_GETFL    = 0x3
-	_F_SETFL    = 0x4
-	_FD_CLOEXEC = 0x1
+	_F_GETFL = 0x3
+	_F_SETFL = 0x4
 
 	_O_WRONLY   = 0x1
 	_O_NONBLOCK = 0x4
diff --git a/src/runtime/defs_darwin_arm64.go b/src/runtime/defs_darwin_arm64.go
index 30d7443f2e..e26df02959 100644
--- a/src/runtime/defs_darwin_arm64.go
+++ b/src/runtime/defs_darwin_arm64.go
@@ -96,10 +96,8 @@ const (
 
 	_PTHREAD_KEYS_MAX = 512
 
-	_F_SETFD    = 0x2
-	_F_GETFL    = 0x3
-	_F_SETFL    = 0x4
-	_FD_CLOEXEC = 0x1
+	_F_GETFL = 0x3
+	_F_SETFL = 0x4
 
 	_O_WRONLY   = 0x1
 	_O_NONBLOCK = 0x4
diff --git a/src/runtime/defs_openbsd.go b/src/runtime/defs_openbsd.go
index 4161e216db..2ca6a88eca 100644
--- a/src/runtime/defs_openbsd.go
+++ b/src/runtime/defs_openbsd.go
@@ -57,10 +57,8 @@ const (
 
 	PTHREAD_CREATE_DETACHED = C.PTHREAD_CREATE_DETACHED
 
-	F_SETFD    = C.F_SETFD
-	F_GETFL    = C.F_GETFL
-	F_SETFL    = C.F_SETFL
-	FD_CLOEXEC = C.FD_CLOEXEC
+	F_GETFL = C.F_GETFL
+	F_SETFL = C.F_SETFL
 
 	SIGHUP    = C.SIGHUP
 	SIGINT    = C.SIGINT
diff --git a/src/runtime/defs_openbsd_386.go b/src/runtime/defs_openbsd_386.go
index 25524c5982..d38a632577 100644
--- a/src/runtime/defs_openbsd_386.go
+++ b/src/runtime/defs_openbsd_386.go
@@ -35,10 +35,8 @@ const (
 
 	_PTHREAD_CREATE_DETACHED = 0x1
 
-	_F_SETFD    = 0x2
-	_F_GETFL    = 0x3
-	_F_SETFL    = 0x4
-	_FD_CLOEXEC = 0x1
+	_F_GETFL = 0x3
+	_F_SETFL = 0x4
 
 	_SIGHUP    = 0x1
 	_SIGINT    = 0x2
diff --git a/src/runtime/defs_openbsd_amd64.go b/src/runtime/defs_openbsd_amd64.go
index a31d03bce5..ed3c067989 100644
--- a/src/runtime/defs_openbsd_amd64.go
+++ b/src/runtime/defs_openbsd_amd64.go
@@ -35,10 +35,8 @@ const (
 
 	_PTHREAD_CREATE_DETACHED = 0x1
 
-	_F_SETFD    = 0x2
-	_F_GETFL    = 0x3
-	_F_SETFL    = 0x4
-	_FD_CLOEXEC = 0x1
+	_F_GETFL = 0x3
+	_F_SETFL = 0x4
 
 	_SIGHUP    = 0x1
 	_SIGINT    = 0x2
diff --git a/src/runtime/defs_openbsd_arm.go b/src/runtime/defs_openbsd_arm.go
index 1d1767bd3b..00b265e538 100644
--- a/src/runtime/defs_openbsd_arm.go
+++ b/src/runtime/defs_openbsd_arm.go
@@ -35,10 +35,8 @@ const (
 
 	_PTHREAD_CREATE_DETACHED = 0x1
 
-	_F_SETFD    = 0x2
-	_F_GETFL    = 0x3
-	_F_SETFL    = 0x4
-	_FD_CLOEXEC = 0x1
+	_F_GETFL = 0x3
+	_F_SETFL = 0x4
 
 	_SIGHUP    = 0x1
 	_SIGINT    = 0x2
diff --git a/src/runtime/defs_openbsd_arm64.go b/src/runtime/defs_openbsd_arm64.go
index 745d0d3923..894fd39b75 100644
--- a/src/runtime/defs_openbsd_arm64.go
+++ b/src/runtime/defs_openbsd_arm64.go
@@ -36,10 +36,8 @@ const (
 
 	_PTHREAD_CREATE_DETACHED = 0x1
 
-	_F_SETFD    = 0x2
-	_F_GETFL    = 0x3
-	_F_SETFL    = 0x4
-	_FD_CLOEXEC = 0x1
+	_F_GETFL = 0x3
+	_F_SETFL = 0x4
 
 	_SIGHUP    = 0x1
 	_SIGINT    = 0x2
diff --git a/src/runtime/defs_solaris.go b/src/runtime/defs_solaris.go
index 406304de5a..11708ee23a 100644
--- a/src/runtime/defs_solaris.go
+++ b/src/runtime/defs_solaris.go
@@ -125,10 +125,8 @@ const (
 	O_CREAT    = C.O_CREAT
 	O_TRUNC    = C.O_TRUNC
 	O_CLOEXEC  = C.O_CLOEXEC
-	FD_CLOEXEC = C.FD_CLOEXEC
 	F_GETFL    = C.F_GETFL
 	F_SETFL    = C.F_SETFL
-	F_SETFD    = C.F_SETFD
 
 	POLLIN  = C.POLLIN
 	POLLOUT = C.POLLOUT
diff --git a/src/runtime/export_linux_test.go b/src/runtime/export_linux_test.go
index a441c0efa2..426fd1e109 100644
--- a/src/runtime/export_linux_test.go
+++ b/src/runtime/export_linux_test.go
@@ -6,14 +6,9 @@
 
 package runtime
 
-import (
-	"runtime/internal/syscall"
-)
-
 const SiginfoMaxSize = _si_max_size
 const SigeventMaxSize = _sigev_max_size
 
-var Closeonexec = syscall.CloseOnExec
 var NewOSProc0 = newosproc0
 var Mincore = mincore
 var Add = add
diff --git a/src/runtime/export_unix2_test.go b/src/runtime/export_unix2_test.go
deleted file mode 100644
index 360565f272..0000000000
--- a/src/runtime/export_unix2_test.go
+++ /dev/null
@@ -1,10 +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 unix && !linux
-
-package runtime
-
-// for linux close-on-exec implemented in runtime/internal/syscall
-var Closeonexec = closeonexec
diff --git a/src/runtime/export_unix_test.go b/src/runtime/export_unix_test.go
index 6967e7645c..56ff771620 100644
--- a/src/runtime/export_unix_test.go
+++ b/src/runtime/export_unix_test.go
@@ -10,6 +10,7 @@ import "unsafe"
 
 var NonblockingPipe = nonblockingPipe
 var Fcntl = fcntl
+var Closeonexec = closeonexec
 
 func sigismember(mask *sigset, i int) bool {
 	clear := *mask
diff --git a/src/runtime/internal/syscall/defs_linux.go b/src/runtime/internal/syscall/defs_linux.go
deleted file mode 100644
index 71f1fa1453..0000000000
--- a/src/runtime/internal/syscall/defs_linux.go
+++ /dev/null
@@ -1,10 +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.
-
-package syscall
-
-const (
-	F_SETFD    = 2
-	FD_CLOEXEC = 1
-)
diff --git a/src/runtime/internal/syscall/syscall_linux.go b/src/runtime/internal/syscall/syscall_linux.go
index a103d318c4..7209634edb 100644
--- a/src/runtime/internal/syscall/syscall_linux.go
+++ b/src/runtime/internal/syscall/syscall_linux.go
@@ -60,7 +60,3 @@ func EpollCtl(epfd, op, fd int32, event *EpollEvent) (errno uintptr) {
 	_, _, e := Syscall6(SYS_EPOLL_CTL, uintptr(epfd), uintptr(op), uintptr(fd), uintptr(unsafe.Pointer(event)), 0, 0)
 	return e
 }
-
-func CloseOnExec(fd int32) {
-	Syscall6(SYS_FCNTL, uintptr(fd), F_SETFD, FD_CLOEXEC, 0, 0, 0)
-}
diff --git a/src/runtime/netpoll_solaris.go b/src/runtime/netpoll_solaris.go
index 41b2f474ac..13c7ffc2ca 100644
--- a/src/runtime/netpoll_solaris.go
+++ b/src/runtime/netpoll_solaris.go
@@ -121,7 +121,7 @@ var portfd int32 = -1
 func netpollinit() {
 	portfd = port_create()
 	if portfd >= 0 {
-		fcntl(portfd, _F_SETFD, _FD_CLOEXEC)
+		closeonexec(portfd)
 		return
 	}
 
diff --git a/src/runtime/os3_solaris.go b/src/runtime/os3_solaris.go
index d03f30dc9e..046d173c24 100644
--- a/src/runtime/os3_solaris.go
+++ b/src/runtime/os3_solaris.go
@@ -575,11 +575,6 @@ func fcntl(fd, cmd, arg int32) (ret int32, errno int32) {
 	return int32(r1), int32(err)
 }
 
-//go:nosplit
-func closeonexec(fd int32) {
-	fcntl(fd, _F_SETFD, _FD_CLOEXEC)
-}
-
 func osyield1()
 
 //go:nosplit
diff --git a/src/runtime/os_aix.go b/src/runtime/os_aix.go
index 7845de1470..8f10eb7380 100644
--- a/src/runtime/os_aix.go
+++ b/src/runtime/os_aix.go
@@ -358,11 +358,6 @@ func fcntl(fd, cmd, arg int32) (int32, int32) {
 }
 
 //go:nosplit
-func closeonexec(fd int32) {
-	fcntl(fd, _F_SETFD, _FD_CLOEXEC)
-}
-
-//go:nosplit
 func setNonblock(fd int32) {
 	flags, _ := fcntl(fd, _F_GETFL, 0)
 	if flags != -1 {
diff --git a/src/runtime/os_dragonfly.go b/src/runtime/os_dragonfly.go
index fb45de3c71..bb53f4a157 100644
--- a/src/runtime/os_dragonfly.go
+++ b/src/runtime/os_dragonfly.go
@@ -64,7 +64,6 @@ func kevent(kq int32, ch *keventt, nch int32, ev *keventt, nev int32, ts *timesp
 
 func pipe2(flags int32) (r, w int32, errno int32)
 func fcntl(fd, cmd, arg int32) (ret int32, errno int32)
-func closeonexec(fd int32)
 
 // From DragonFly's <sys/sysctl.h>
 const (
diff --git a/src/runtime/os_freebsd.go b/src/runtime/os_freebsd.go
index ad9e58c062..b53a70bef0 100644
--- a/src/runtime/os_freebsd.go
+++ b/src/runtime/os_freebsd.go
@@ -49,7 +49,6 @@ func kevent(kq int32, ch *keventt, nch int32, ev *keventt, nev int32, ts *timesp
 
 func pipe2(flags int32) (r, w int32, errno int32)
 func fcntl(fd, cmd, arg int32) (ret int32, errno int32)
-func closeonexec(fd int32)
 
 // From FreeBSD's <sys/sysctl.h>
 const (
diff --git a/src/runtime/os_netbsd.go b/src/runtime/os_netbsd.go
index 1688049ee7..92c02c193f 100644
--- a/src/runtime/os_netbsd.go
+++ b/src/runtime/os_netbsd.go
@@ -80,7 +80,6 @@ func kevent(kq int32, ch *keventt, nch int32, ev *keventt, nev int32, ts *timesp
 
 func pipe2(flags int32) (r, w int32, errno int32)
 func fcntl(fd, cmd, arg int32) (ret int32, errno int32)
-func closeonexec(fd int32)
 
 const (
 	_ESRCH     = 3
diff --git a/src/runtime/os_openbsd_syscall2.go b/src/runtime/os_openbsd_syscall2.go
index dcf3b09e67..bba89f3cb1 100644
--- a/src/runtime/os_openbsd_syscall2.go
+++ b/src/runtime/os_openbsd_syscall2.go
@@ -96,6 +96,5 @@ func nanotime1() int64
 func sigaltstack(new, old *stackt)
 
 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/os_unix.go b/src/runtime/os_unix.go
new file mode 100644
index 0000000000..fdbeba70cc
--- /dev/null
+++ b/src/runtime/os_unix.go
@@ -0,0 +1,19 @@
+// Copyright 2023 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 unix
+
+package runtime
+
+const (
+	// These values are the same on all known Unix systems.
+	// If we find a discrepancy some day, we can split them out.
+	_F_SETFD    = 2
+	_FD_CLOEXEC = 1
+)
+
+//go:nosplit
+func closeonexec(fd int32) {
+	fcntl(fd, _F_SETFD, _FD_CLOEXEC)
+}
diff --git a/src/runtime/sys_darwin.go b/src/runtime/sys_darwin.go
index a56a9373b9..2229ee87ed 100644
--- a/src/runtime/sys_darwin.go
+++ b/src/runtime/sys_darwin.go
@@ -537,11 +537,6 @@ func exitThread(wait *atomic.Uint32) {
 }
 
 //go:nosplit
-func closeonexec(fd int32) {
-	fcntl(fd, _F_SETFD, _FD_CLOEXEC)
-}
-
-//go:nosplit
 func setNonblock(fd int32) {
 	flags, _ := fcntl(fd, _F_GETFL, 0)
 	if flags != -1 {
diff --git a/src/runtime/sys_dragonfly_amd64.s b/src/runtime/sys_dragonfly_amd64.s
index 28bc0a70eb..4e16c9d662 100644
--- a/src/runtime/sys_dragonfly_amd64.s
+++ b/src/runtime/sys_dragonfly_amd64.s
@@ -400,12 +400,3 @@ noerr:
 	MOVL	AX, ret+16(FP)
 	MOVL	$0, errno+20(FP)
 	RET
-
-// void runtime·closeonexec(int32 fd);
-TEXT runtime·closeonexec(SB),NOSPLIT,$0
-	MOVL	fd+0(FP), DI	// fd
-	MOVQ	$2, SI		// F_SETFD
-	MOVQ	$1, DX		// FD_CLOEXEC
-	MOVL	$92, AX		// fcntl
-	SYSCALL
-	RET
diff --git a/src/runtime/sys_freebsd_386.s b/src/runtime/sys_freebsd_386.s
index a5a668cb70..3d5531fecb 100644
--- a/src/runtime/sys_freebsd_386.s
+++ b/src/runtime/sys_freebsd_386.s
@@ -12,8 +12,6 @@
 
 #define CLOCK_REALTIME		0
 #define CLOCK_MONOTONIC		4
-#define FD_CLOEXEC		1
-#define F_SETFD			2
 
 #define SYS_exit		1
 #define SYS_read		3
@@ -464,19 +462,6 @@ noerr:
 	MOVL	$0, errno+16(FP)
 	RET
 
-// int32 runtime·closeonexec(int32 fd);
-TEXT runtime·closeonexec(SB),NOSPLIT,$32
-	MOVL	$SYS_fcntl, AX
-	// 0(SP) is where the caller PC would be; kernel skips it
-	MOVL	fd+0(FP), BX
-	MOVL	BX, 4(SP)	// fd
-	MOVL	$F_SETFD, 8(SP)
-	MOVL	$FD_CLOEXEC, 12(SP)
-	INT	$0x80
-	JAE	2(PC)
-	NEGL	AX
-	RET
-
 // func cpuset_getaffinity(level int, which int, id int64, size int, mask *byte) int32
 TEXT runtime·cpuset_getaffinity(SB), NOSPLIT, $0-28
 	MOVL	$SYS_cpuset_getaffinity, AX
diff --git a/src/runtime/sys_freebsd_amd64.s b/src/runtime/sys_freebsd_amd64.s
index 2f600ea678..ff39d15a03 100644
--- a/src/runtime/sys_freebsd_amd64.s
+++ b/src/runtime/sys_freebsd_amd64.s
@@ -13,8 +13,6 @@
 
 #define CLOCK_REALTIME		0
 #define CLOCK_MONOTONIC		4
-#define FD_CLOEXEC		1
-#define F_SETFD			2
 #define AMD64_SET_FSBASE	129
 
 #define SYS_exit		1
@@ -564,15 +562,6 @@ noerr:
 	MOVL	$0, errno+20(FP)
 	RET
 
-// void runtime·closeonexec(int32 fd);
-TEXT runtime·closeonexec(SB),NOSPLIT,$0
-	MOVL	fd+0(FP), DI	// fd
-	MOVQ	$F_SETFD, SI
-	MOVQ	$FD_CLOEXEC, DX
-	MOVL	$SYS_fcntl, AX
-	SYSCALL
-	RET
-
 // func cpuset_getaffinity(level int, which int, id int64, size int, mask *byte) int32
 TEXT runtime·cpuset_getaffinity(SB), NOSPLIT, $0-44
 	MOVQ	level+0(FP), DI
diff --git a/src/runtime/sys_freebsd_arm.s b/src/runtime/sys_freebsd_arm.s
index 9b09d9d349..3b76cc84a7 100644
--- a/src/runtime/sys_freebsd_arm.s
+++ b/src/runtime/sys_freebsd_arm.s
@@ -401,15 +401,6 @@ TEXT runtime·fcntl(SB),NOSPLIT,$0
 	MOVW R1, errno+16(FP)
 	RET
 
-// void runtime·closeonexec(int32 fd)
-TEXT runtime·closeonexec(SB),NOSPLIT,$0
-	MOVW fd+0(FP), R0	// fd
-	MOVW $2, R1	// F_SETFD
-	MOVW $1, R2	// FD_CLOEXEC
-	MOVW $SYS_fcntl, R7
-	SWI $0
-	RET
-
 // TODO: this is only valid for ARMv7+
 TEXT ·publicationBarrier(SB),NOSPLIT|NOFRAME,$0-0
 	B	runtime·armPublicationBarrier(SB)
diff --git a/src/runtime/sys_freebsd_arm64.s b/src/runtime/sys_freebsd_arm64.s
index dcf32a26e7..ef0366277f 100644
--- a/src/runtime/sys_freebsd_arm64.s
+++ b/src/runtime/sys_freebsd_arm64.s
@@ -14,8 +14,6 @@
 
 #define CLOCK_REALTIME		0
 #define CLOCK_MONOTONIC		4
-#define FD_CLOEXEC		1
-#define F_SETFD			2
 #define F_GETFL			3
 #define F_SETFL			4
 #define O_NONBLOCK		4
@@ -456,15 +454,6 @@ noerr:
 	MOVW	$0, errno+20(FP)
 	RET
 
-// func closeonexec(fd int32)
-TEXT runtime·closeonexec(SB),NOSPLIT|NOFRAME,$0
-	MOVW	fd+0(FP), R0
-	MOVD	$F_SETFD, R1
-	MOVD	$FD_CLOEXEC, R2
-	MOVD	$SYS_fcntl, R8
-	SVC
-	RET
-
 // func getCntxct(physical bool) uint32
 TEXT runtime·getCntxct(SB),NOSPLIT,$0
 	MOVB	physical+0(FP), R0
diff --git a/src/runtime/sys_freebsd_riscv64.s b/src/runtime/sys_freebsd_riscv64.s
index 58173c2cb6..be6966b9aa 100644
--- a/src/runtime/sys_freebsd_riscv64.s
+++ b/src/runtime/sys_freebsd_riscv64.s
@@ -13,8 +13,6 @@
 
 #define CLOCK_REALTIME		0
 #define CLOCK_MONOTONIC		4
-#define FD_CLOEXEC		1
-#define F_SETFD			2
 #define F_GETFL			3
 #define F_SETFL			4
 #define O_NONBLOCK		4
@@ -437,15 +435,6 @@ noerr:
 	MOVW	ZERO, errno+20(FP)
 	RET
 
-// func closeonexec(fd int32)
-TEXT runtime·closeonexec(SB),NOSPLIT|NOFRAME,$0
-	MOVW	fd+0(FP), A0
-	MOV	$F_SETFD, A1
-	MOV	$FD_CLOEXEC, A2
-	MOV	$SYS_fcntl, T0
-	ECALL
-	RET
-
 // func getCntxct() uint32
 TEXT runtime·getCntxct(SB),NOSPLIT|NOFRAME,$0
 	RDTIME	A0
diff --git a/src/runtime/sys_netbsd_386.s b/src/runtime/sys_netbsd_386.s
index e649fb13cb..dbfc4b552e 100644
--- a/src/runtime/sys_netbsd_386.s
+++ b/src/runtime/sys_netbsd_386.s
@@ -12,8 +12,6 @@
 
 #define CLOCK_REALTIME		0
 #define CLOCK_MONOTONIC		3
-#define FD_CLOEXEC		1
-#define F_SETFD			2
 
 #define SYS_exit			1
 #define SYS_read			3
@@ -469,16 +467,3 @@ noerr:
 	MOVL	AX, ret+12(FP)
 	MOVL	$0, errno+16(FP)
 	RET
-
-// int32 runtime·closeonexec(int32 fd)
-TEXT runtime·closeonexec(SB),NOSPLIT,$32
-	MOVL	$SYS_fcntl, AX
-	// 0(SP) is where the caller PC would be; kernel skips it
-	MOVL	fd+0(FP), BX
-	MOVL	BX, 4(SP)	// fd
-	MOVL	$F_SETFD, 8(SP)
-	MOVL	$FD_CLOEXEC, 12(SP)
-	INT	$0x80
-	JAE	2(PC)
-	NEGL	AX
-	RET
diff --git a/src/runtime/sys_netbsd_amd64.s b/src/runtime/sys_netbsd_amd64.s
index c01473a0cf..948f62b8c5 100644
--- a/src/runtime/sys_netbsd_amd64.s
+++ b/src/runtime/sys_netbsd_amd64.s
@@ -13,8 +13,6 @@
 
 #define CLOCK_REALTIME		0
 #define CLOCK_MONOTONIC		3
-#define FD_CLOEXEC		1
-#define F_SETFD			2
 
 #define SYS_exit			1
 #define SYS_read			3
@@ -447,12 +445,3 @@ noerr:
 	MOVL	AX, ret+16(FP)
 	MOVL	$0, errno+20(FP)
 	RET
-
-// void runtime·closeonexec(int32 fd)
-TEXT runtime·closeonexec(SB),NOSPLIT,$0
-	MOVL	fd+0(FP), DI	// fd
-	MOVQ	$F_SETFD, SI
-	MOVQ	$FD_CLOEXEC, DX
-	MOVL	$SYS_fcntl, AX
-	SYSCALL
-	RET
diff --git a/src/runtime/sys_netbsd_arm.s b/src/runtime/sys_netbsd_arm.s
index 9d969592c4..91ec00e424 100644
--- a/src/runtime/sys_netbsd_arm.s
+++ b/src/runtime/sys_netbsd_arm.s
@@ -12,8 +12,6 @@
 
 #define CLOCK_REALTIME		0
 #define CLOCK_MONOTONIC		3
-#define FD_CLOEXEC		1
-#define F_SETFD			2
 
 #define SWI_OS_NETBSD			0xa00000
 #define SYS_exit			SWI_OS_NETBSD | 1
@@ -411,14 +409,6 @@ TEXT runtime·fcntl(SB),NOSPLIT,$0
 	MOVW R1, errno+16(FP)
 	RET
 
-// void runtime·closeonexec(int32 fd)
-TEXT runtime·closeonexec(SB),NOSPLIT,$0
-	MOVW fd+0(FP), R0	// fd
-	MOVW $F_SETFD, R1	// F_SETFD
-	MOVW $FD_CLOEXEC, R2	// FD_CLOEXEC
-	SWI $SYS_fcntl
-	RET
-
 // TODO: this is only valid for ARMv7+
 TEXT ·publicationBarrier(SB),NOSPLIT|NOFRAME,$0-0
 	B	runtime·armPublicationBarrier(SB)
diff --git a/src/runtime/sys_netbsd_arm64.s b/src/runtime/sys_netbsd_arm64.s
index 34523530d5..611b9e1d74 100644
--- a/src/runtime/sys_netbsd_arm64.s
+++ b/src/runtime/sys_netbsd_arm64.s
@@ -13,8 +13,6 @@
 
 #define CLOCK_REALTIME		0
 #define CLOCK_MONOTONIC		3
-#define FD_CLOEXEC		1
-#define F_SETFD			2
 #define F_GETFL			3
 #define F_SETFL			4
 #define O_NONBLOCK		4
@@ -431,11 +429,3 @@ noerr:
 	MOVW	R0, ret+16(FP)
 	MOVW	$0, errno+20(FP)
 	RET
-
-// void runtime·closeonexec(int32 fd)
-TEXT runtime·closeonexec(SB),NOSPLIT,$0
-	MOVW	fd+0(FP), R0		// arg 1 - fd
-	MOVW	$F_SETFD, R1
-	MOVW	$FD_CLOEXEC, R2
-	SVC	$SYS_fcntl
-	RET
diff --git a/src/runtime/sys_openbsd2.go b/src/runtime/sys_openbsd2.go
index 12a53dfc6d..e69bfc3348 100644
--- a/src/runtime/sys_openbsd2.go
+++ b/src/runtime/sys_openbsd2.go
@@ -258,11 +258,6 @@ func exitThread(wait *atomic.Uint32) {
 	throw("exitThread")
 }
 
-//go:nosplit
-func closeonexec(fd int32) {
-	fcntl(fd, _F_SETFD, _FD_CLOEXEC)
-}
-
 // Tell the linker that the libc_* functions are to be found
 // in a system library, with the libc_ prefix missing.
 
diff --git a/src/runtime/sys_openbsd_mips64.s b/src/runtime/sys_openbsd_mips64.s
index 9238e7d0b0..bea20f2433 100644
--- a/src/runtime/sys_openbsd_mips64.s
+++ b/src/runtime/sys_openbsd_mips64.s
@@ -379,12 +379,3 @@ noerr:
 	MOVW	R2, ret+16(FP)
 	MOVW	R4, errno+20(FP)
 	RET
-
-// func closeonexec(fd int32)
-TEXT runtime·closeonexec(SB),NOSPLIT,$0
-	MOVW	fd+0(FP), R4		// arg 1 - fd
-	MOVV	$2, R5			// arg 2 - cmd (F_SETFD)
-	MOVV	$1, R6			// arg 3 - arg (FD_CLOEXEC)
-	MOVV	$92, R2			// sys_fcntl
-	SYSCALL
-	RET