init: refactor first stage to not require fstab

In order to support dm-linear devices, we need an additional first-stage
step to ensure that required devices are created. This must happen before
setting up dm-verity or mounting any first-stage partitions.

This patch refactors FirstStageMount so that having a compatible fstab
is optional. This will let us use InitRequiredDevices on systems that
would not otherwise perform first-stage mounts.

Bug: 78914864
Test: non-AVB devices still boot
Change-Id: I11265375a9900d983da8cabcc77d32c503ded02e

1 files changed, 12 insertions, 15 deletions

diff --git a/init/init_first_stage.cpp b/init/init_first_stage.cpp
index 45d3d4499..1b6e97ec7 100644
--- a/init/init_first_stage.cpp
+++ b/init/init_first_stage.cpp
@@ -118,14 +118,14 @@ static bool inline IsRecoveryMode() {
 // -----------------
 FirstStageMount::FirstStageMount()
     : need_dm_verity_(false), device_tree_fstab_(fs_mgr_read_fstab_dt(), fs_mgr_free_fstab) {
-    if (!device_tree_fstab_) {
+    if (device_tree_fstab_) {
+        // Stores device_tree_fstab_->recs[] into mount_fstab_recs_ (vector<fstab_rec*>)
+        // for easier manipulation later, e.g., range-base for loop.
+        for (int i = 0; i < device_tree_fstab_->num_entries; i++) {
+            mount_fstab_recs_.push_back(&device_tree_fstab_->recs[i]);
+        }
+    } else {
         LOG(INFO) << "Failed to read fstab from device tree";
-        return;
-    }
-    // Stores device_tree_fstab_->recs[] into mount_fstab_recs_ (vector<fstab_rec*>)
-    // for easier manipulation later, e.g., range-base for loop.
-    for (int i = 0; i < device_tree_fstab_->num_entries; i++) {
-        mount_fstab_recs_.push_back(&device_tree_fstab_->recs[i]);
     }
 }
 
@@ -138,8 +138,11 @@ std::unique_ptr<FirstStageMount> FirstStageMount::Create() {
 }
 
 bool FirstStageMount::DoFirstStageMount() {
-    // Nothing to mount.
-    if (mount_fstab_recs_.empty()) return true;
+    if (mount_fstab_recs_.empty()) {
+        // Nothing to mount.
+        LOG(INFO) << "First stage mount skipped (missing/incompatible/empty fstab in device tree)";
+        return true;
+    }
 
     if (!InitDevices()) return false;
 
@@ -479,12 +482,6 @@ bool DoFirstStageMount() {
         return true;
     }
 
-    // Firstly checks if device tree fstab entries are compatible.
-    if (!is_android_dt_value_expected("fstab/compatible", "android,fstab")) {
-        LOG(INFO) << "First stage mount skipped (missing/incompatible fstab in device tree)";
-        return true;
-    }
-
     std::unique_ptr<FirstStageMount> handle = FirstStageMount::Create();
     if (!handle) {
         LOG(ERROR) << "Failed to create FirstStageMount";