Remove usermem dependency from marshal

Both marshal and usermem are depended on by many packages and a dependency on
marshal can often create circular dependencies. marshal should consider adding
internal dependencies carefully moving forward.

Fixes #6160

PiperOrigin-RevId: 379199882

pkg/abi/linux/signal.go

@@ -293,8 +293,6 @@ type Sigevent struct {
 	UnRemainder [44]byte
 }
 
-// LINT.IfChange
-
 // SigAction represents struct sigaction.
 //
 // +marshal
@@ -306,8 +304,6 @@ type SigAction struct {
 	Mask     SignalSet
 }
 
-// LINT.ThenChange(../../safecopy/safecopy_unsafe.go)
-
 // SignalStack represents information about a user stack, and is equivalent to
 // stack_t.
 //

pkg/marshal/primitive/BUILD

@@ -12,9 +12,7 @@ go_library(
         "//:sandbox",
     ],
     deps = [
-        "//pkg/context",
         "//pkg/hostarch",
         "//pkg/marshal",
-        "//pkg/usermem",
     ],
 )

pkg/marshal/primitive/primitive.go

@@ -19,10 +19,8 @@ package primitive
 import (
 	"io"
 
-	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/hostarch"
 	"gvisor.dev/gvisor/pkg/marshal"
-	"gvisor.dev/gvisor/pkg/usermem"
 )
 
 // Int8 is a marshal.Marshallable implementation for int8.
@@ -400,26 +398,3 @@ func CopyStringOut(cc marshal.CopyContext, addr hostarch.Addr, src string) (int,
 	srcP := ByteSlice(src)
 	return srcP.CopyOut(cc, addr)
 }
-
-// IOCopyContext wraps an object implementing hostarch.IO to implement
-// marshal.CopyContext.
-type IOCopyContext struct {
-	Ctx  context.Context
-	IO   usermem.IO
-	Opts usermem.IOOpts
-}
-
-// CopyScratchBuffer implements marshal.CopyContext.CopyScratchBuffer.
-func (i *IOCopyContext) CopyScratchBuffer(size int) []byte {
-	return make([]byte, size)
-}
-
-// CopyOutBytes implements marshal.CopyContext.CopyOutBytes.
-func (i *IOCopyContext) CopyOutBytes(addr hostarch.Addr, b []byte) (int, error) {
-	return i.IO.CopyOut(i.Ctx, addr, b, i.Opts)
-}
-
-// CopyInBytes implements marshal.CopyContext.CopyInBytes.
-func (i *IOCopyContext) CopyInBytes(addr hostarch.Addr, b []byte) (int, error) {
-	return i.IO.CopyIn(i.Ctx, addr, b, i.Opts)
-}

pkg/safecopy/BUILD

@@ -18,6 +18,7 @@ go_library(
     ],
     visibility = ["//:sandbox"],
     deps = [
+        "//pkg/abi/linux",
         "//pkg/syserror",
         "@org_golang_x_sys//unix:go_default_library",
     ],

pkg/safecopy/safecopy_unsafe.go

@@ -20,6 +20,7 @@ import (
 	"unsafe"
 
 	"golang.org/x/sys/unix"
+	"gvisor.dev/gvisor/pkg/abi/linux"
 )
 
 // maxRegisterSize is the maximum register size used in memcpy and memclr. It
@@ -342,15 +343,7 @@ func errorFromFaultSignal(addr uintptr, sig int32) error {
 // handler however, and if this is function is being used externally then the
 // same courtesy is expected.
 func ReplaceSignalHandler(sig unix.Signal, handler uintptr, previous *uintptr) error {
-	// TODO(gvisor.dev/issue/6160): This struct is the same as linux.SigAction.
-	// Once the usermem dependency is removed from primitive, delete this replica
-	// and remove IFTTT comments in abi/linux/signal.go.
-	var sa struct {
-		handler  uintptr
-		flags    uint64
-		restorer uintptr
-		mask     uint64
-	}
+	var sa linux.SigAction
 	const maskLen = 8
 
 	// Get the existing signal handler information, and save the current
@@ -361,14 +354,14 @@ func ReplaceSignalHandler(sig unix.Signal, handler uintptr, previous *uintptr) e
 	}
 
 	// Fail if there isn't a previous handler.
-	if sa.handler == 0 {
+	if sa.Handler == 0 {
 		return fmt.Errorf("previous handler for signal %x isn't set", sig)
 	}
 
-	*previous = sa.handler
+	*previous = uintptr(sa.Handler)
 
 	// Install our own handler.
-	sa.handler = handler
+	sa.Handler = uint64(handler)
 	if _, _, e := unix.RawSyscall6(unix.SYS_RT_SIGACTION, uintptr(sig), uintptr(unsafe.Pointer(&sa)), 0, maskLen, 0, 0); e != 0 {
 		return e
 	}

pkg/sentry/kernel/pipe/pipe_util.go

@@ -135,7 +135,7 @@ func (p *Pipe) Ioctl(ctx context.Context, io usermem.IO, args arch.SyscallArgume
 			v = math.MaxInt32 // Silently truncate.
 		}
 		// Copy result to userspace.
-		iocc := primitive.IOCopyContext{
+		iocc := usermem.IOCopyContext{
 			IO:  io,
 			Ctx: ctx,
 			Opts: usermem.IOOpts{

pkg/usermem/BUILD

@@ -7,6 +7,7 @@ go_library(
     srcs = [
         "bytes_io.go",
         "bytes_io_unsafe.go",
+        "marshal.go",
         "usermem.go",
     ],
     visibility = ["//:sandbox"],

pkg/usermem/marshal.go

@@ -0,0 +1,43 @@
+// Copyright 2021 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 usermem
+
+import (
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/hostarch"
+)
+
+// IOCopyContext wraps an object implementing hostarch.IO to implement
+// marshal.CopyContext.
+type IOCopyContext struct {
+	Ctx  context.Context
+	IO   IO
+	Opts IOOpts
+}
+
+// CopyScratchBuffer implements marshal.CopyContext.CopyScratchBuffer.
+func (i *IOCopyContext) CopyScratchBuffer(size int) []byte {
+	return make([]byte, size)
+}
+
+// CopyOutBytes implements marshal.CopyContext.CopyOutBytes.
+func (i *IOCopyContext) CopyOutBytes(addr hostarch.Addr, b []byte) (int, error) {
+	return i.IO.CopyOut(i.Ctx, addr, b, i.Opts)
+}
+
+// CopyInBytes implements marshal.CopyContext.CopyInBytes.
+func (i *IOCopyContext) CopyInBytes(addr hostarch.Addr, b []byte) (int, error) {
+	return i.IO.CopyIn(i.Ctx, addr, b, i.Opts)
+}