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// Copyright 2016 The Bazel Authors. All rights reserved.
//
// 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 com.google.devtools.build.lib.sandbox;
import com.google.common.io.Files;
import com.google.devtools.build.lib.util.Preconditions;
import com.google.devtools.build.lib.vfs.FileStatus;
import com.google.devtools.build.lib.vfs.FileSystemUtils;
import com.google.devtools.build.lib.vfs.Path;
import com.google.devtools.build.lib.vfs.PathFragment;
import com.google.devtools.build.lib.vfs.Symlinks;
import java.io.IOException;
import java.util.Collection;
import java.util.HashSet;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
/**
* Creates an execRoot for a Spawn that contains input files as symlinks to their original
* destination.
*/
public final class SymlinkedExecRoot implements SandboxExecRoot {
private final Path sandboxExecRoot;
public SymlinkedExecRoot(Path sandboxExecRoot) {
this.sandboxExecRoot = sandboxExecRoot;
}
@Override
public void createFileSystem(
Map<PathFragment, Path> inputs, Collection<PathFragment> outputs, Set<Path> writableDirs)
throws IOException {
Set<Path> createdDirs = new HashSet<>();
cleanFileSystem(inputs.keySet());
FileSystemUtils.createDirectoryAndParentsWithCache(createdDirs, sandboxExecRoot);
createParentDirectoriesForInputs(createdDirs, inputs.keySet());
createSymlinksForInputs(inputs);
createWritableDirectories(createdDirs, writableDirs);
createDirectoriesForOutputs(createdDirs, outputs);
}
private void cleanFileSystem(Set<PathFragment> allowedFiles) throws IOException {
if (sandboxExecRoot.exists(Symlinks.NOFOLLOW)) {
deleteExceptAllowedFiles(sandboxExecRoot, allowedFiles);
}
}
private void deleteExceptAllowedFiles(Path root, Set<PathFragment> allowedFiles)
throws IOException {
for (Path p : root.getDirectoryEntries()) {
FileStatus stat = p.stat(Symlinks.NOFOLLOW);
if (!stat.isDirectory()) {
if (!allowedFiles.contains(p.relativeTo(sandboxExecRoot))) {
p.delete();
}
} else {
deleteExceptAllowedFiles(p, allowedFiles);
if (p.readdir(Symlinks.NOFOLLOW).isEmpty()) {
p.delete();
}
}
}
}
/**
* No input can be a child of another input, because otherwise we might try to create a symlink
* below another symlink we created earlier - which means we'd actually end up writing somewhere
* in the workspace.
*
* <p>If all inputs were regular files, this situation could naturally not happen - but
* unfortunately, we might get the occasional action that has directories in its inputs.
*
* <p>Creating all parent directories first ensures that we can safely create symlinks to
* directories, too, because we'll get an IOException with EEXIST if inputs happen to be nested
* once we start creating the symlinks for all inputs.
*/
private void createParentDirectoriesForInputs(Set<Path> createdDirs, Set<PathFragment> inputs)
throws IOException {
for (PathFragment inputPath : inputs) {
Path dir = sandboxExecRoot.getRelative(inputPath).getParentDirectory();
Preconditions.checkArgument(dir.startsWith(sandboxExecRoot));
FileSystemUtils.createDirectoryAndParentsWithCache(createdDirs, dir);
}
}
private void createSymlinksForInputs(Map<PathFragment, Path> inputs) throws IOException {
// All input files are relative to the execroot.
for (Entry<PathFragment, Path> entry : inputs.entrySet()) {
Path key = sandboxExecRoot.getRelative(entry.getKey());
FileStatus keyStat = key.statNullable(Symlinks.NOFOLLOW);
if (keyStat != null) {
if (keyStat.isSymbolicLink()
&& key.readSymbolicLink().equals(entry.getValue().asFragment())) {
continue;
}
key.delete();
}
key.createSymbolicLink(entry.getValue());
}
}
private void createWritableDirectories(Set<Path> createdDirs, Set<Path> writableDirs)
throws IOException {
for (Path writablePath : writableDirs) {
if (writablePath.startsWith(sandboxExecRoot)) {
FileSystemUtils.createDirectoryAndParentsWithCache(createdDirs, writablePath);
}
}
}
/** Prepare the output directories in the sandbox. */
private void createDirectoriesForOutputs(Set<Path> createdDirs, Collection<PathFragment> outputs)
throws IOException {
for (PathFragment output : outputs) {
FileSystemUtils.createDirectoryAndParentsWithCache(
createdDirs, sandboxExecRoot.getRelative(output.getParentDirectory()));
}
}
/** Moves all {@code outputs} to {@code execRoot}. */
@Override
public void copyOutputs(Path execRoot, Collection<PathFragment> outputs) throws IOException {
for (PathFragment output : outputs) {
Path source = sandboxExecRoot.getRelative(output);
Path target = execRoot.getRelative(output);
if (source.isFile() || source.isSymbolicLink()) {
Files.move(source.getPathFile(), target.getPathFile());
} else if (source.isDirectory()) {
try {
source.renameTo(target);
} catch (IOException e) {
// Failed to move directory directly, thus move it recursively.
target.createDirectory();
FileSystemUtils.moveTreesBelow(source, target);
}
}
}
}
}
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