[view compilation] Add viewcompiler support to installd

This change adds methods to installd to call viewcompiler and generate
precompiled layouts when requested either by `pm compile --compile-layouts`,
package install, or package upgrade.

Bug: 111895153
Test: manual
Change-Id: Ic021d7a41c15642664f44542653170ad24055f22
diff --git a/cmds/installd/view_compiler.cpp b/cmds/installd/view_compiler.cpp
new file mode 100644
index 0000000..f1ac717
--- /dev/null
+++ b/cmds/installd/view_compiler.cpp
@@ -0,0 +1,99 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * 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.
+ */
+
+#include "view_compiler.h"
+
+#include <string>
+
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include "utils.h"
+
+#include "android-base/logging.h"
+#include "android-base/stringprintf.h"
+#include "android-base/unique_fd.h"
+
+namespace android {
+namespace installd {
+
+using base::unique_fd;
+
+bool view_compiler(const char* apk_path, const char* package_name, const char* out_dex_file,
+                   int uid) {
+    CHECK(apk_path != nullptr);
+    CHECK(package_name != nullptr);
+    CHECK(out_dex_file != nullptr);
+
+    // viewcompiler won't have permission to open anything, so we have to open the files first
+    // and pass file descriptors.
+
+    // Open input file
+    unique_fd infd{open(apk_path, 0)};
+    if (infd.get() < 0) {
+        PLOG(ERROR) << "Could not open input file: " << apk_path;
+        return false;
+    }
+
+    // Set up output file. viewcompiler can't open outputs by fd, but it can write to stdout, so
+    // we close stdout and open it towards the right output.
+    unique_fd outfd{open(out_dex_file, O_CREAT | O_TRUNC | O_WRONLY, 0644)};
+    if (outfd.get() < 0) {
+        PLOG(ERROR) << "Could not open output file: " << out_dex_file;
+        return false;
+    }
+    if (fchmod(outfd, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH) != 0) {
+        PLOG(ERROR) << "Could not change output file permissions";
+        return false;
+    }
+    if (close(STDOUT_FILENO) != 0) {
+        PLOG(ERROR) << "Could not close stdout";
+        return false;
+    }
+    if (dup2(outfd, STDOUT_FILENO) < 0) {
+        PLOG(ERROR) << "Could not duplicate output file descriptor";
+        return false;
+    }
+
+    // Prepare command line arguments for viewcompiler
+    std::string args[] = {"/system/bin/viewcompiler",
+                          "--apk",
+                          "--infd",
+                          android::base::StringPrintf("%d", infd.get()),
+                          "--dex",
+                          "--package",
+                          package_name};
+    char* const argv[] = {const_cast<char*>(args[0].c_str()), const_cast<char*>(args[1].c_str()),
+                          const_cast<char*>(args[2].c_str()), const_cast<char*>(args[3].c_str()),
+                          const_cast<char*>(args[4].c_str()), const_cast<char*>(args[5].c_str()),
+                          const_cast<char*>(args[6].c_str()), nullptr};
+
+    pid_t pid = fork();
+    if (pid == 0) {
+        // Now that we've opened the files we need, drop privileges.
+        drop_capabilities(uid);
+        execv("/system/bin/viewcompiler", argv);
+        _exit(1);
+    }
+
+    return wait_child(pid) == 0;
+}
+
+} // namespace installd
+} // namespace android
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