arcvm: Generate first stage fstab file for ARCVM

The new file, /run/arcvm/host_generated/fstab, is exported by crosvm
to the guest via the device tree so the guest can read certain files
in its init's first stage.

Previously, the generated file was just:

/run/arcvm/host_generated/factory/factory.prop

With this CL, they will be:

/run/arcvm/host_generated/fstab
/run/arcvm/host_generated/combined.prop

This CL depends on
https://chromium-review.googlesource.com/c/chromiumos/platform2/+/2217082

BUG=b:157188856
TEST=arc.BuildProperties.vm

Change-Id: Ia646fe592e94e83ddce80e21177086f5b996ee3e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2216916Reviewed-by: Long Cheng <lgcheng@google.com>
Commit-Queue: Yusuke Sato <yusukes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#773532}

chrome/browser/chromeos/arc/session/arc_session_manager.cc

@@ -10,6 +10,7 @@
 #include "base/bind.h"
 #include "base/callback_helpers.h"
 #include "base/command_line.h"
+#include "base/files/file_util.h"
 #include "base/logging.h"
 #include "base/rand_util.h"
 #include "base/strings/string16.h"
@@ -185,6 +186,18 @@ std::string GetOrCreateSerialNumber(PrefService* prefs) {
   return serial_number;
 }
 
+bool ExpandPropertyFilesInternal(const base::FilePath& source_path,
+                                 const base::FilePath& dest_path,
+                                 bool single_file) {
+  if (!arc::ExpandPropertyFiles(source_path, dest_path, single_file))
+    return false;
+  if (!arc::IsArcVmEnabled())
+    return true;
+  // For ARCVM, the first stage fstab file needs to be generated.
+  return arc::GenerateFirstStageFstab(dest_path,
+                                      dest_path.DirName().Append("fstab"));
+}
+
 }  // namespace
 
 // This class is used to track statuses on OptIn flow. It is created in case ARC
@@ -1284,13 +1297,13 @@ void ArcSessionManager::EmitLoginPromptVisibleCalled() {
 void ArcSessionManager::ExpandPropertyFiles() {
   VLOG(1) << "Started expanding *.prop files";
 
-  // For ARCVM, generate <dest_path>/factory/factory.prop. For ARC, generate
+  // For ARCVM, generate <dest_path>/{combined.prop,fstab}. For ARC, generate
   // <dest_path>/{default,build,vendor_build}.prop.
   const bool is_arcvm = arc::IsArcVmEnabled();
   base::ThreadPool::PostTaskAndReplyWithResult(
       FROM_HERE, {base::MayBlock(), base::TaskPriority::USER_VISIBLE},
-      base::BindOnce(&arc::ExpandPropertyFiles, property_files_source_dir_,
-                     is_arcvm ? property_files_dest_dir_.Append("factory")
+      base::BindOnce(&ExpandPropertyFilesInternal, property_files_source_dir_,
+                     is_arcvm ? property_files_dest_dir_.Append("combined.prop")
                               : property_files_dest_dir_,
                      /*single_file=*/is_arcvm),
       base::BindOnce(&ArcSessionManager::OnExpandPropertyFiles,

components/arc/arc_util.cc

@@ -11,6 +11,8 @@
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/feature_list.h"
+#include "base/files/file_path.h"
+#include "base/files/file_util.h"
 #include "base/optional.h"
 #include "base/strings/string_number_conversions.h"
 #include "chromeos/constants/chromeos_switches.h"
@@ -303,7 +305,6 @@ bool IsArcPlayAutoInstallDisabled() {
       chromeos::switches::kArcDisablePlayAutoInstall);
 }
 
-// static
 int32_t GetLcdDensityForDeviceScaleFactor(float device_scale_factor) {
   const auto* command_line = base::CommandLine::ForCurrentProcess();
   if (command_line->HasSwitch(chromeos::switches::kArcScale)) {
@@ -333,4 +334,26 @@ int32_t GetLcdDensityForDeviceScaleFactor(float device_scale_factor) {
       kDefaultDensityDpi);
 }
 
+bool GenerateFirstStageFstab(const base::FilePath& combined_property_file_name,
+                             const base::FilePath& fstab_path) {
+  DCHECK(IsArcVmEnabled());
+  // The file is exposed to the guest by crosvm via /sys/firmware/devicetree,
+  // which in turn allows the guest's init process to mount /vendor very early,
+  // in its first stage (device) initialization step. crosvm also special-cases
+  // #dt-vendor line and expose |combined_property_file_name| via the device
+  // tree file system too. This also allow the init process to load the expanded
+  // properties very early even before all file systems are mounted.
+  //
+  // The device name for /vendor has to match what arc_vm_client_adapter.cc
+  // configures.
+  constexpr const char kFirstStageFstabTemplate[] =
+      "/dev/block/vdb /vendor squashfs ro,noatime,nosuid,nodev "
+      "wait,check,formattable,reservedsize=128M\n"
+      "#dt-vendor build.prop %s default default\n";
+  return base::WriteFile(
+      fstab_path,
+      base::StringPrintf(kFirstStageFstabTemplate,
+                         combined_property_file_name.value().c_str()));
+}
+
 }  // namespace arc

components/arc/arc_util.h

@@ -18,6 +18,7 @@ class Window;
 
 namespace base {
 class CommandLine;
+class FilePath;
 }  // namespace base
 
 namespace user_manager {
@@ -149,6 +150,12 @@ void SetArcCpuRestriction(CpuRestrictionState cpu_restriction_state);
 // factor used on chrome.
 int32_t GetLcdDensityForDeviceScaleFactor(float device_scale_factor);
 
+// Generates a file called first stage fstab at |fstab_path| which is exported
+// by crosvm to the guest via the device tree so the guest can read certain
+// files in its init's first stage.
+bool GenerateFirstStageFstab(const base::FilePath& combined_property_file_name,
+                             const base::FilePath& fstab_path);
+
 }  // namespace arc
 
 #endif  // COMPONENTS_ARC_ARC_UTIL_H_

components/arc/arc_util_unittest.cc

@@ -10,6 +10,8 @@
 #include "ash/public/cpp/app_types.h"
 #include "base/base_switches.h"
 #include "base/command_line.h"
+#include "base/files/file_util.h"
+#include "base/files/scoped_temp_dir.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
 #include "base/test/scoped_feature_list.h"
@@ -275,5 +277,32 @@ TEST_F(ArcUtilTest, ScaleFactorToDensity) {
   EXPECT_EQ(240, GetLcdDensityForDeviceScaleFactor(2.0));
 }
 
+TEST_F(ArcUtilTest, GenerateFirstStageFstab) {
+  constexpr const char kFakeCombinedBuildPropPath[] = "/path/to/build.prop";
+  constexpr const char kAnotherFakeCombinedBuildPropPath[] =
+      "/foo/bar/baz.prop";
+
+  auto* command_line = base::CommandLine::ForCurrentProcess();
+  command_line->InitFromArgv({"", "--enable-arcvm"});
+
+  std::string content;
+  base::ScopedTempDir dir;
+  ASSERT_TRUE(dir.CreateUniqueTempDir());
+  const base::FilePath fstab(dir.GetPath().Append("fstab"));
+
+  // Generate the fstab and verify the content.
+  EXPECT_TRUE(GenerateFirstStageFstab(
+      base::FilePath(kFakeCombinedBuildPropPath), fstab));
+  EXPECT_TRUE(base::ReadFileToString(fstab, &content));
+  EXPECT_NE(std::string::npos, content.find(kFakeCombinedBuildPropPath));
+
+  // Generate the fstab again with the other prop file and verify the content.
+  EXPECT_TRUE(GenerateFirstStageFstab(
+      base::FilePath(kAnotherFakeCombinedBuildPropPath), fstab));
+  EXPECT_TRUE(base::ReadFileToString(fstab, &content));
+  EXPECT_EQ(std::string::npos, content.find(kFakeCombinedBuildPropPath));
+  EXPECT_NE(std::string::npos, content.find(kAnotherFakeCombinedBuildPropPath));
+}
+
 }  // namespace
 }  // namespace arc

components/arc/session/arc_property_util.cc

@@ -302,14 +302,13 @@ bool ExpandPropertyFiles(const base::FilePath& source_path,
                          const base::FilePath& dest_path,
                          bool single_file) {
   CrosConfig config;
-  const base::FilePath single_dest_file = dest_path.Append("factory.prop");
   if (single_file)
-    base::DeleteFile(single_dest_file, /*recursive=*/false);
+    base::DeleteFile(dest_path, /*recursive=*/false);
 
   for (const char* file : {"default.prop", "build.prop", "vendor_build.prop"}) {
-    if (!ExpandPropertyFile(
-            source_path.Append(file),
-            single_file ? single_dest_file : dest_path.Append(file), &config,
+    if (!ExpandPropertyFile(source_path.Append(file),
+                            single_file ? dest_path : dest_path.Append(file),
+                            &config,
                             /*append=*/single_file)) {
       LOG(ERROR) << "Failed to expand " << source_path.Append(file);
       return false;

components/arc/session/arc_property_util.h

@@ -59,9 +59,8 @@ bool ExpandPropertyFileForTesting(const base::FilePath& input,
 
 // Calls ExpandPropertyFile for {build,default,vendor_build}.prop files in
 // |source_path|. Expanded files are written in |dest_path|. Returns true on
-// success. When |single_file| is true, only one file (factory.prop) is written
-// in |dest_path|, and also, properties that are actually expanded are written
-// to the file.
+// success. When |single_file| is true, only one file (|dest_path| itself) is
+// written. All expanded properties are included in the single file.
 bool ExpandPropertyFiles(const base::FilePath& source_path,
                          const base::FilePath& dest_path,
                          bool single_file);

components/arc/session/arc_property_util_unittest.cc

@@ -357,48 +357,50 @@ TEST_F(ArcPropertyUtilTest, ExpandPropertyFiles_SingleFile) {
   // Both source and dest exist, but the source directory is empty.
   base::FilePath source_dir;
   ASSERT_TRUE(base::CreateTemporaryDirInDir(GetTempDir(), "test", &source_dir));
-  base::FilePath dest_dir;
-  ASSERT_TRUE(base::CreateTemporaryDirInDir(GetTempDir(), "test", &dest_dir));
-  EXPECT_FALSE(ExpandPropertyFiles(source_dir, dest_dir, true));
+  base::FilePath dest_prop_file;
+  ASSERT_TRUE(
+      base::CreateTemporaryDirInDir(GetTempDir(), "test", &dest_prop_file));
+  dest_prop_file = dest_prop_file.Append("combined.prop");
+  EXPECT_FALSE(ExpandPropertyFiles(source_dir, dest_prop_file, true));
 
   // Add default.prop to the source, but not build.prop.
   base::FilePath default_prop = source_dir.Append("default.prop");
   constexpr const char kDefaultProp[] = "ro.foo=bar\n";
   base::WriteFile(default_prop, kDefaultProp, strlen(kDefaultProp));
-  EXPECT_FALSE(ExpandPropertyFiles(source_dir, dest_dir, true));
+  EXPECT_FALSE(ExpandPropertyFiles(source_dir, dest_prop_file, true));
 
   // Add build.prop too. The call should not succeed still.
   base::FilePath build_prop = source_dir.Append("build.prop");
   constexpr const char kBuildProp[] = "ro.baz=boo\n";
   base::WriteFile(build_prop, kBuildProp, strlen(kBuildProp));
-  EXPECT_FALSE(ExpandPropertyFiles(source_dir, dest_dir, true));
+  EXPECT_FALSE(ExpandPropertyFiles(source_dir, dest_prop_file, true));
 
   // Add vendor_build.prop too. Then the call should succeed.
   base::FilePath vendor_build_prop = source_dir.Append("vendor_build.prop");
   constexpr const char kVendorBuildProp[] = "ro.a=b\n";
   base::WriteFile(vendor_build_prop, kVendorBuildProp,
                   strlen(kVendorBuildProp));
-  EXPECT_TRUE(ExpandPropertyFiles(source_dir, dest_dir, true));
+  EXPECT_TRUE(ExpandPropertyFiles(source_dir, dest_prop_file, true));
 
   // Verify only one dest file exists.
-  EXPECT_FALSE(base::PathExists(dest_dir.Append("default.prop")));
-  EXPECT_FALSE(base::PathExists(dest_dir.Append("build.prop")));
-  EXPECT_FALSE(base::PathExists(dest_dir.Append("vendor_build.prop")));
-  EXPECT_TRUE(base::PathExists(dest_dir.Append("factory.prop")));
+  EXPECT_FALSE(
+      base::PathExists(dest_prop_file.DirName().Append("default.prop")));
+  EXPECT_FALSE(base::PathExists(dest_prop_file.DirName().Append("build.prop")));
+  EXPECT_FALSE(
+      base::PathExists(dest_prop_file.DirName().Append("vendor_build.prop")));
+  EXPECT_TRUE(base::PathExists(dest_prop_file));
 
   // Verify the content.
   // Note: ExpandPropertyFileForTesting() adds a trailing LF.
   std::string content;
-  EXPECT_TRUE(
-      base::ReadFileToString(dest_dir.Append("factory.prop"), &content));
+  EXPECT_TRUE(base::ReadFileToString(dest_prop_file, &content));
   EXPECT_EQ(base::StringPrintf("%s\n%s\n%s\n", kDefaultProp, kBuildProp,
                                kVendorBuildProp),
             content);
 
   // Expand it again, verify the previous result is cleared.
-  EXPECT_TRUE(ExpandPropertyFiles(source_dir, dest_dir, true));
-  EXPECT_TRUE(
-      base::ReadFileToString(dest_dir.Append("factory.prop"), &content));
+  EXPECT_TRUE(ExpandPropertyFiles(source_dir, dest_prop_file, true));
+  EXPECT_TRUE(base::ReadFileToString(dest_prop_file, &content));
   EXPECT_EQ(base::StringPrintf("%s\n%s\n%s\n", kDefaultProp, kBuildProp,
                                kVendorBuildProp),
             content);

components/arc/session/arc_vm_client_adapter.cc

@@ -227,19 +227,21 @@ vm_tools::concierge::StartArcVmRequest CreateStartArcVmRequest(
 
   vm->set_kernel(file_system_status.guest_kernel_path().value());
 
-  // Add / as /dev/vda.
+  // Add rootfs as /dev/vda.
   vm->set_rootfs(file_system_status.system_image_path().value());
   request.set_rootfs_writable(file_system_status.is_host_rootfs_writable() &&
                               file_system_status.is_system_image_ext_format());
 
-  // Add /vendor as /dev/vdb.
+  // Add /vendor as /dev/block/vdb. The device name has to be consistent with
+  // the one in GenerateFirstStageFstab() in ../arc_util.cc.
   vm_tools::concierge::DiskImage* disk_image = request.add_disks();
   disk_image->set_path(file_system_status.vendor_image_path().value());
   disk_image->set_image_type(vm_tools::concierge::DISK_IMAGE_AUTO);
   disk_image->set_writable(false);
   disk_image->set_do_mount(true);
 
-  // Add /run/imageloader/.../android_demo_apps.squash as /dev/vdc if needed.
+  // Add /run/imageloader/.../android_demo_apps.squash as /dev/block/vdc if
+  // needed.
   // TODO(b/144542975): Do this on upgrade instead.
   if (!demo_session_apps_path.empty()) {
     disk_image = request.add_disks();

components/arc/session/file_system_status.cc

@@ -22,7 +22,7 @@ namespace {
 
 constexpr const char kArcVmConfigJsonPath[] = "/usr/share/arcvm/config.json";
 constexpr const char kBuiltinPath[] = "/opt/google/vms/android";
-constexpr const char kFstab[] = "fstab";
+constexpr const char kFstabPath[] = "/run/arcvm/host_generated/fstab";
 constexpr const char kKernel[] = "vmlinux";
 constexpr const char kRootFs[] = "system.raw.img";
 constexpr const char kVendorImage[] = "vendor.raw.img";
@@ -41,7 +41,7 @@ FileSystemStatus::FileSystemStatus()
       system_image_path_(base::FilePath(kBuiltinPath).Append(kRootFs)),
       vendor_image_path_(base::FilePath(kBuiltinPath).Append(kVendorImage)),
       guest_kernel_path_(base::FilePath(kBuiltinPath).Append(kKernel)),
-      fstab_path_(base::FilePath(kBuiltinPath).Append(kFstab)),
+      fstab_path_(kFstabPath),
       is_system_image_ext_format_(IsSystemImageExtFormat(system_image_path_)) {}
 
 // static