runtime: add fcntl wrapper for syscall

Signed-off-by: leongross <[email protected]>

src/runtime/os_linux.go

@@ -5,7 +5,9 @@ package runtime
 // This file is for systems that are _actually_ Linux (not systems that pretend
 // to be Linux, like baremetal systems).
 
-import "unsafe"
+import (
+	"unsafe"
+)
 
 const GOOS = "linux"
 
@@ -139,3 +141,7 @@ func hardwareRand() (n uint64, ok bool) {
 //
 //export getrandom
 func libc_getrandom(buf unsafe.Pointer, buflen uintptr, flags uint32) uint32
+
+//go:linknam runtime_fcntl syscall/syscall_fcntl
+//go:export
+func runtime_fcntl(fd, cmd, arg int32) (ret int32, errno int32)

src/syscall/syscall_libc.go

@@ -212,6 +212,13 @@ func Truncate(path string, length int64) (err error) {
 	return
 }
 
+//go:linkname syscall_fcntl runtime.fcntl
+func syscall_fcntl(fd, cmd, arg int32) (ret int32, errno int32) {
+	// https://cs.opensource.google/go/go/+/master:src/runtime/os_linux.go;l=452?q=runtime.fcntl&ss=go%2Fgo
+	r, _, err := Syscall6(SYS_FCNTL, uintptr(fd), uintptr(cmd), uintptr(arg), 0, 0, 0)
+	return int32(r), int32(err)
+}
+
 func Faccessat(dirfd int, path string, mode uint32, flags int) (err error)
 
 func Kill(pid int, sig Signal) (err error) {