first_stage_mount: Create snapshot devices before launching first_stage_console

During device bringup, dynamic partitions may not be properly
configured by some sort of build or load misconfiguration. Diagnosing
such issues can be difficult without being able to see which partitions
are available and what they contain.

Aditionally, making logical partitions available to first stage console
permits early mounting of vendor partition and allows primitive
validation of vendor scripts without requiring full Android
environment. For instance, vendor_dlkm partition and modules can be
probed needing to have a full Android bootup.

Creation of logical partitions is done only when first_stage_console is
requested in order to have minimal impact on normal boot. Thus, only a
small refactor is required to split CreateLogicalPartitions out of
MountPartitions.

Bug: 174685384
Bug: 173732805
Change-Id: I828ce999be6d786bf46dd5655dfda81d046906ab
Signed-off-by: Elliot Berman <[email protected]>

Author: Elliot Berman

init/first_stage_init.cpp

@@ -286,7 +286,15 @@ int FirstStageMain(int argc, char** argv) {
         }
     }
 
+
+    bool created_devices = false;
     if (want_console == FirstStageConsoleParam::CONSOLE_ON_FAILURE) {
+        if (!IsRecoveryMode()) {
+            created_devices = DoCreateDevices();
+            if (!created_devices){
+                LOG(ERROR) << "Failed to create device nodes early";
+            }
+        }
         StartConsole(cmdline);
     }
 
@@ -327,7 +335,7 @@ int FirstStageMain(int argc, char** argv) {
         }
     }
 
-    if (!DoFirstStageMount()) {
+    if (!DoFirstStageMount(!created_devices)) {
         LOG(FATAL) << "Failed to mount required partitions early ...";
     }
 

init/first_stage_mount.cpp

@@ -82,6 +82,7 @@ class FirstStageMount {
     // The factory method to create either FirstStageMountVBootV1 or FirstStageMountVBootV2
     // based on device tree configurations.
     static std::unique_ptr<FirstStageMount> Create();
+    bool DoCreateDevices();    // Creates devices and logical partitions from storage devices
     bool DoFirstStageMount();  // Mounts fstab entries read from device tree.
     bool InitDevices();
 
@@ -244,13 +245,7 @@ std::unique_ptr<FirstStageMount> FirstStageMount::Create() {
     }
 }
 
-bool FirstStageMount::DoFirstStageMount() {
-    if (!IsDmLinearEnabled() && fstab_.empty()) {
-        // Nothing to mount.
-        LOG(INFO) << "First stage mount skipped (missing/incompatible/empty fstab in device tree)";
-        return true;
-    }
-
+bool FirstStageMount::DoCreateDevices() {
     if (!InitDevices()) return false;
 
     // Mount /metadata before creating logical partitions, since we need to
@@ -269,6 +264,16 @@ bool FirstStageMount::DoFirstStageMount() {
 
     if (!CreateLogicalPartitions()) return false;
 
+    return true;
+}
+
+bool FirstStageMount::DoFirstStageMount() {
+    if (!IsDmLinearEnabled() && fstab_.empty()) {
+        // Nothing to mount.
+        LOG(INFO) << "First stage mount skipped (missing/incompatible/empty fstab in device tree)";
+        return true;
+    }
+
     if (!MountPartitions()) return false;
 
     return true;
@@ -829,8 +834,18 @@ bool FirstStageMountVBootV2::InitAvbHandle() {
 
 // Public functions
 // ----------------
+// Creates devices and logical partitions from storage devices
+bool DoCreateDevices() {
+    std::unique_ptr<FirstStageMount> handle = FirstStageMount::Create();
+    if (!handle) {
+        LOG(ERROR) << "Failed to create FirstStageMount";
+        return false;
+    }
+    return handle->DoCreateDevices();
+}
+
 // Mounts partitions specified by fstab in device tree.
-bool DoFirstStageMount() {
+bool DoFirstStageMount(bool create_devices) {
     // Skips first stage mount if we're in recovery mode.
     if (IsRecoveryMode()) {
         LOG(INFO) << "First stage mount skipped (recovery mode)";
@@ -842,6 +857,11 @@ bool DoFirstStageMount() {
         LOG(ERROR) << "Failed to create FirstStageMount";
         return false;
     }
+
+    if (create_devices) {
+        if (!handle->DoCreateDevices()) return false;
+    }
+
     return handle->DoFirstStageMount();
 }
 

init/first_stage_mount.h

@@ -19,7 +19,8 @@
 namespace android {
 namespace init {
 
-bool DoFirstStageMount();
+bool DoCreateDevices();
+bool DoFirstStageMount(bool create_devices);
 void SetInitAvbVersionInRecovery();
 
 }  // namespace init