7 files changed, 31 insertions, 56 deletions
diff --git a/pkg/flipcall/BUILD b/pkg/flipcall/BUILD
index 9730b88c1..c810c7946 100644
--- a/pkg/flipcall/BUILD
+++ b/pkg/flipcall/BUILD
@@ -10,9 +10,7 @@ go_library(
         "flipcall_unsafe.go",
         "futex_linux.go",
         "io.go",
-        "packet_window_allocator.go",
-        "packet_window_mmap_amd64.go",
-        "packet_window_mmap_arm64.go",
+        "packet_window.go",
     ],
     visibility = ["//visibility:public"],
     deps = [
diff --git a/pkg/flipcall/ctrl_futex.go b/pkg/flipcall/ctrl_futex.go
index 2e8452a02..99410628f 100644
--- a/pkg/flipcall/ctrl_futex.go
+++ b/pkg/flipcall/ctrl_futex.go
@@ -12,6 +12,9 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+//go:build go1.1
+// +build go1.1
+
 package flipcall
 
 import (
@@ -118,7 +121,7 @@ func (ep *Endpoint) ctrlWaitFirst() error {
 	return ep.futexWaitUntilActive()
 }
 
-func (ep *Endpoint) ctrlRoundTrip() error {
+func (ep *Endpoint) ctrlRoundTrip(mayRetainP bool) error {
 	if err := ep.enterFutexWait(); err != nil {
 		return err
 	}
@@ -130,6 +133,9 @@ func (ep *Endpoint) ctrlRoundTrip() error {
 	if err := ep.futexWakePeer(); err != nil {
 		return err
 	}
+	// Since we don't know if the peer Endpoint is in the same process as this
+	// one (in which case it may need our P to run), we allow our P to be
+	// retaken regardless of mayRetainP.
 	return ep.futexWaitUntilActive()
 }
 
diff --git a/pkg/flipcall/flipcall.go b/pkg/flipcall/flipcall.go
index 8d8309a73..88588ba0e 100644
--- a/pkg/flipcall/flipcall.go
+++ b/pkg/flipcall/flipcall.go
@@ -22,6 +22,7 @@ import (
 	"sync/atomic"
 
 	"golang.org/x/sys/unix"
+	"gvisor.dev/gvisor/pkg/memutil"
 )
 
 // An Endpoint provides the ability to synchronously transfer data and control
@@ -96,9 +97,9 @@ func (ep *Endpoint) Init(side EndpointSide, pwd PacketWindowDescriptor, opts ...
 	if pwd.Length > math.MaxUint32 {
 		return fmt.Errorf("packet window size (%d) exceeds maximum (%d)", pwd.Length, math.MaxUint32)
 	}
-	m, e := packetWindowMmap(pwd)
-	if e != 0 {
-		return fmt.Errorf("failed to mmap packet window: %v", e)
+	m, err := memutil.MapFile(0, uintptr(pwd.Length), unix.PROT_READ|unix.PROT_WRITE, unix.MAP_SHARED, uintptr(pwd.FD), uintptr(pwd.Offset))
+	if err != nil {
+		return fmt.Errorf("failed to mmap packet window: %v", err)
 	}
 	ep.packet = m
 	ep.dataCap = uint32(pwd.Length) - uint32(PacketHeaderBytes)
@@ -222,6 +223,23 @@ func (ep *Endpoint) RecvFirst() (uint32, error) {
 // * If ep is a client Endpoint, ep.Connect() has previously been called and
 //   returned nil.
 func (ep *Endpoint) SendRecv(dataLen uint32) (uint32, error) {
+	return ep.sendRecv(dataLen, false /* mayRetainP */)
+}
+
+// SendRecvFast is equivalent to SendRecv, but may prevent the caller's runtime
+// P from being released, in which case the calling goroutine continues to
+// count against GOMAXPROCS while waiting for the peer Endpoint to return
+// control to the caller.
+//
+// SendRecvFast is appropriate if the peer Endpoint is expected to consistently
+// return control in a short amount of time (less than ~10ms).
+//
+// Preconditions: As for SendRecv.
+func (ep *Endpoint) SendRecvFast(dataLen uint32) (uint32, error) {
+	return ep.sendRecv(dataLen, true /* mayRetainP */)
+}
+
+func (ep *Endpoint) sendRecv(dataLen uint32, mayRetainP bool) (uint32, error) {
 	if dataLen > ep.dataCap {
 		panic(fmt.Sprintf("attempting to send packet with datagram length %d (maximum %d)", dataLen, ep.dataCap))
 	}
@@ -232,7 +250,7 @@ func (ep *Endpoint) SendRecv(dataLen uint32) (uint32, error) {
 	// they can only shoot themselves in the foot.
 	*ep.dataLen() = dataLen
 	raceBecomeInactive()
-	if err := ep.ctrlRoundTrip(); err != nil {
+	if err := ep.ctrlRoundTrip(mayRetainP); err != nil {
 		return 0, err
 	}
 	raceBecomeActive()
diff --git a/pkg/flipcall/futex_linux.go b/pkg/flipcall/futex_linux.go
index c212f05f1..4bb85939b 100644
--- a/pkg/flipcall/futex_linux.go
+++ b/pkg/flipcall/futex_linux.go
@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+//go:build linux
 // +build linux
 
 package flipcall
diff --git a/pkg/flipcall/packet_window_allocator.go b/pkg/flipcall/packet_window.go
index 9122c97b7..9122c97b7 100644
--- a/pkg/flipcall/packet_window_allocator.go
+++ b/pkg/flipcall/packet_window.go
diff --git a/pkg/flipcall/packet_window_mmap_amd64.go b/pkg/flipcall/packet_window_mmap_amd64.go
deleted file mode 100644
index ced587a2a..000000000
--- a/pkg/flipcall/packet_window_mmap_amd64.go
+++ /dev/null
@@ -1,23 +0,0 @@
-// Copyright 2020 The gVisor Authors.
-//
-// 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.
-
-package flipcall
-
-import "golang.org/x/sys/unix"
-
-// Return a memory mapping of the pwd in memory that can be shared outside the sandbox.
-func packetWindowMmap(pwd PacketWindowDescriptor) (uintptr, unix.Errno) {
-	m, _, err := unix.RawSyscall6(unix.SYS_MMAP, 0, uintptr(pwd.Length), unix.PROT_READ|unix.PROT_WRITE, unix.MAP_SHARED, uintptr(pwd.FD), uintptr(pwd.Offset))
-	return m, err
-}
diff --git a/pkg/flipcall/packet_window_mmap_arm64.go b/pkg/flipcall/packet_window_mmap_arm64.go
deleted file mode 100644
index 87ad1a4a1..000000000
--- a/pkg/flipcall/packet_window_mmap_arm64.go
+++ /dev/null
@@ -1,25 +0,0 @@
-// Copyright 2020 The gVisor Authors.
-//
-// 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 arm64
-
-package flipcall
-
-import "golang.org/x/sys/unix"
-
-// Return a memory mapping of the pwd in memory that can be shared outside the sandbox.
-func packetWindowMmap(pwd PacketWindowDescriptor) (uintptr, unix.Errno) {
-	m, _, err := unix.RawSyscall6(unix.SYS_MMAP, 0, uintptr(pwd.Length), unix.PROT_READ|unix.PROT_WRITE, unix.MAP_SHARED, uintptr(pwd.FD), uintptr(pwd.Offset))
-	return m, err
-}