Internal change.

PiperOrigin-RevId: 228979583

tcpip/link/rawfile/blockingpoll_amd64.s

@@ -20,7 +20,7 @@
 //
 // func blockingPoll(fds *pollEvent, nfds int, timeout int64) (n int, err syscall.Errno)
 TEXT ·blockingPoll(SB),NOSPLIT,$0-40
-	CALL	runtime·entersyscallblock(SB)
+	CALL	·callEntersyscallblock(SB)
 	MOVQ	fds+0(FP), DI
 	MOVQ	nfds+8(FP), SI
 	MOVQ	timeout+16(FP), DX
@@ -31,10 +31,10 @@ TEXT ·blockingPoll(SB),NOSPLIT,$0-40
 	MOVQ	$-1, n+24(FP)
 	NEGQ	AX
 	MOVQ	AX, err+32(FP)
-	CALL	runtime·exitsyscall(SB)
+	CALL	·callExitsyscall(SB)
 	RET
 ok:
 	MOVQ	AX, n+24(FP)
 	MOVQ	$0, err+32(FP)
-	CALL	runtime·exitsyscall(SB)
+	CALL	·callExitsyscall(SB)
 	RET

tcpip/link/rawfile/blockingpoll_amd64_unsafe.go

@@ -0,0 +1,59 @@
+// Copyright 2018 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build linux,amd64
+// +build !go1.13
+
+// This must be validated with Go 1.13 and future releases.
+
+package rawfile
+
+import (
+	"syscall"
+	_ "unsafe" // for go:linkname
+)
+
+//go:noescape
+func blockingPoll(fds *pollEvent, nfds int, timeout int64) (int, syscall.Errno)
+
+// Use go:linkname to call into the runtime. As of Go 1.12 this has to
+// be done from Go code so that we make an ABIInternal call to an
+// ABIInternal function; see https://golang.org/issue/27539.
+
+// We need to call both entersyscallblock and exitsyscall this way so
+// that the runtime's check on the stack pointer lines up.
+
+// Note that calling an unexported function in the runtime package is
+// unsafe and this hack is likely to break in future Go releases.
+
+//go:linkname entersyscallblock runtime.entersyscallblock
+func entersyscallblock()
+
+//go:linkname exitsyscall runtime.exitsyscall
+func exitsyscall()
+
+// These forwarding functions must be nosplit because 1) we must
+// disallow preemption between entersyscallblock and exitsyscall, and
+// 2) we have an untyped assembly frame on the stack which can not be
+// grown or moved.
+
+//go:nosplit
+func callEntersyscallblock() {
+	entersyscallblock()
+}
+
+//go:nosplit
+func callExitsyscall() {
+	exitsyscall()
+}