2 files changed, 153 insertions, 0 deletions
diff --git a/pkg/sentry/fdimport/BUILD b/pkg/sentry/fdimport/BUILD
new file mode 100644
index 000000000..5e41ceb4e
--- /dev/null
+++ b/pkg/sentry/fdimport/BUILD
@@ -0,0 +1,19 @@
+load("//tools:defs.bzl", "go_library")
+
+package(licenses = ["notice"])
+
+go_library(
+    name = "fdimport",
+    srcs = [
+        "fdimport.go",
+    ],
+    visibility = ["//pkg/sentry:internal"],
+    deps = [
+        "//pkg/context",
+        "//pkg/sentry/fs",
+        "//pkg/sentry/fs/host",
+        "//pkg/sentry/fsimpl/host",
+        "//pkg/sentry/kernel",
+        "//pkg/sentry/vfs",
+    ],
+)
diff --git a/pkg/sentry/fdimport/fdimport.go b/pkg/sentry/fdimport/fdimport.go
new file mode 100644
index 000000000..1b7cb94c0
--- /dev/null
+++ b/pkg/sentry/fdimport/fdimport.go
@@ -0,0 +1,134 @@
+// 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 fdimport
+
+import (
+	"fmt"
+
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/sentry/fs"
+	"gvisor.dev/gvisor/pkg/sentry/fs/host"
+	hostvfs2 "gvisor.dev/gvisor/pkg/sentry/fsimpl/host"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+)
+
+// Import imports a slice of FDs into the given FDTable. If console is true,
+// sets up TTY for the first 3 FDs in the slice representing stdin, stdout,
+// stderr. Upon success, Import takes ownership of all FDs.
+func Import(ctx context.Context, fdTable *kernel.FDTable, console bool, fds []int) (*host.TTYFileOperations, *hostvfs2.TTYFileDescription, error) {
+	if kernel.VFS2Enabled {
+		ttyFile, err := importVFS2(ctx, fdTable, console, fds)
+		return nil, ttyFile, err
+	}
+	ttyFile, err := importFS(ctx, fdTable, console, fds)
+	return ttyFile, nil, err
+}
+
+func importFS(ctx context.Context, fdTable *kernel.FDTable, console bool, fds []int) (*host.TTYFileOperations, error) {
+	var ttyFile *fs.File
+	for appFD, hostFD := range fds {
+		var appFile *fs.File
+
+		if console && appFD < 3 {
+			// Import the file as a host TTY file.
+			if ttyFile == nil {
+				var err error
+				appFile, err = host.ImportFile(ctx, hostFD, true /* isTTY */)
+				if err != nil {
+					return nil, err
+				}
+				defer appFile.DecRef(ctx)
+
+				// Remember this in the TTY file, as we will
+				// use it for the other stdio FDs.
+				ttyFile = appFile
+			} else {
+				// Re-use the existing TTY file, as all three
+				// stdio FDs must point to the same fs.File in
+				// order to share TTY state, specifically the
+				// foreground process group id.
+				appFile = ttyFile
+			}
+		} else {
+			// Import the file as a regular host file.
+			var err error
+			appFile, err = host.ImportFile(ctx, hostFD, false /* isTTY */)
+			if err != nil {
+				return nil, err
+			}
+			defer appFile.DecRef(ctx)
+		}
+
+		// Add the file to the FD map.
+		if err := fdTable.NewFDAt(ctx, int32(appFD), appFile, kernel.FDFlags{}); err != nil {
+			return nil, err
+		}
+	}
+
+	if ttyFile == nil {
+		return nil, nil
+	}
+	return ttyFile.FileOperations.(*host.TTYFileOperations), nil
+}
+
+func importVFS2(ctx context.Context, fdTable *kernel.FDTable, console bool, stdioFDs []int) (*hostvfs2.TTYFileDescription, error) {
+	k := kernel.KernelFromContext(ctx)
+	if k == nil {
+		return nil, fmt.Errorf("cannot find kernel from context")
+	}
+
+	var ttyFile *vfs.FileDescription
+	for appFD, hostFD := range stdioFDs {
+		var appFile *vfs.FileDescription
+
+		if console && appFD < 3 {
+			// Import the file as a host TTY file.
+			if ttyFile == nil {
+				var err error
+				appFile, err = hostvfs2.ImportFD(ctx, k.HostMount(), hostFD, true /* isTTY */)
+				if err != nil {
+					return nil, err
+				}
+				defer appFile.DecRef(ctx)
+
+				// Remember this in the TTY file, as we will use it for the other stdio
+				// FDs.
+				ttyFile = appFile
+			} else {
+				// Re-use the existing TTY file, as all three stdio FDs must point to
+				// the same fs.File in order to share TTY state, specifically the
+				// foreground process group id.
+				appFile = ttyFile
+			}
+		} else {
+			var err error
+			appFile, err = hostvfs2.ImportFD(ctx, k.HostMount(), hostFD, false /* isTTY */)
+			if err != nil {
+				return nil, err
+			}
+			defer appFile.DecRef(ctx)
+		}
+
+		if err := fdTable.NewFDAtVFS2(ctx, int32(appFD), appFile, kernel.FDFlags{}); err != nil {
+			return nil, err
+		}
+	}
+
+	if ttyFile == nil {
+		return nil, nil
+	}
+	return ttyFile.Impl().(*hostvfs2.TTYFileDescription), nil
+}