Refactor our sandboxing code.

--
MOS_MIGRATED_REVID=131817068

1 files changed, 115 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/sandbox/SymlinkedExecRoot.java b/src/main/java/com/google/devtools/build/lib/sandbox/SymlinkedExecRoot.java
new file mode 100644
index 0000000000..de0f31f46e
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/sandbox/SymlinkedExecRoot.java
@@ -0,0 +1,115 @@
+// 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.FileSystemUtils;
+import com.google.devtools.build.lib.vfs.Path;
+import com.google.devtools.build.lib.vfs.PathFragment;
+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.
+ */
+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<>();
+    FileSystemUtils.createDirectoryAndParentsWithCache(createdDirs, sandboxExecRoot);
+    createParentDirectoriesForInputs(createdDirs, inputs.keySet());
+    createSymlinksForInputs(inputs);
+    createWritableDirectories(createdDirs, writableDirs);
+    createDirectoriesForOutputs(createdDirs, outputs);
+  }
+
+  /**
+   * 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());
+      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 {
+    Set<Path> createdDirs = new HashSet<>();
+    for (PathFragment output : outputs) {
+      Path source = sandboxExecRoot.getRelative(output);
+      if (source.isFile() || source.isSymbolicLink()) {
+        FileSystemUtils.createDirectoryAndParentsWithCache(
+            createdDirs, execRoot.getRelative(output.getParentDirectory()));
+
+        Path target = execRoot.getRelative(output);
+        Files.move(source.getPathFile(), target.getPathFile());
+      }
+    }
+  }
+}