Move flipcall.packetWindowMmap to memutil.

PiperOrigin-RevId: 381100861

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 = [

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)

pkg/memutil/BUILD

@@ -4,7 +4,11 @@ package(licenses = ["notice"])
 
 go_library(
     name = "memutil",
-    srcs = ["memutil_unsafe.go"],
+    srcs = [
+        "memfd_linux_unsafe.go",
+        "memutil.go",
+        "mmap.go",
+    ],
     visibility = ["//visibility:public"],
     deps = ["@org_golang_x_sys//unix:go_default_library"],
 )

pkg/memutil/memfd_linux_unsafe.go

@@ -14,7 +14,6 @@
 
 // +build linux
 
-// Package memutil provides a wrapper for the memfd_create() system call.
 package memutil
 
 import (

pkg/memutil/memutil.go

@@ -1,4 +1,4 @@
-// Copyright 2020 The gVisor Authors.
+// Copyright 2018 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.
@@ -12,14 +12,5 @@
 // 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
-}
+// Package memutil provides utilities for working with shared memory files.
+package memutil

pkg/memutil/mmap.go

@@ -12,12 +12,18 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package flipcall
+package memutil
 
-import "golang.org/x/sys/unix"
+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
+// MapFile returns a memory mapping configured by the given options as per
+// mmap(2).
+func MapFile(addr, len, prot, flags, fd, offset uintptr) (uintptr, error) {
+	m, _, e := unix.RawSyscall6(unix.SYS_MMAP, addr, len, prot, flags, fd, offset)
+	if e != 0 {
+		return 0, e
+	}
+	return m, nil
 }