init: Add support for GSI installations in first-stage mount.

Bug: 121209697
Test: gsi boots
Change-Id: I69db0f8e999da366e46728b1008602f543cd79f6
diff --git a/init/Android.bp b/init/Android.bp
index c920dc2..3369fb9 100644
--- a/init/Android.bp
+++ b/init/Android.bp
@@ -77,6 +77,7 @@
         "libext4_utils",
         "libfs_mgr",
         "libfscrypt",
+        "libgsi",
         "libhidl-gen-utils",
         "libkeyutils",
         "liblog",
diff --git a/init/Android.mk b/init/Android.mk
index bdd0301..69c63e1 100644
--- a/init/Android.mk
+++ b/init/Android.mk
@@ -91,6 +91,7 @@
     libz \
     libselinux \
     libcap \
+    libgsi \
 
 LOCAL_SANITIZE := signed-integer-overflow
 # First stage init is weird: it may start without stdout/stderr, and no /proc.
diff --git a/init/builtins.cpp b/init/builtins.cpp
index 4a66e46..0139317 100644
--- a/init/builtins.cpp
+++ b/init/builtins.cpp
@@ -54,6 +54,7 @@
 #include <fs_mgr.h>
 #include <fscrypt/fscrypt.h>
 #include <fscrypt/fscrypt_init_extensions.h>
+#include <libgsi/libgsi.h>
 #include <selinux/android.h>
 #include <selinux/label.h>
 #include <selinux/selinux.h>
@@ -520,6 +521,9 @@
         return Success();
     } else if (code == FS_MGR_MNTALL_DEV_NEEDS_RECOVERY) {
         /* Setup a wipe via recovery, and reboot into recovery */
+        if (android::gsi::IsGsiRunning()) {
+            return Error() << "cannot wipe within GSI";
+        }
         PLOG(ERROR) << "fs_mgr_mount_all suggested recovery, so wiping data via recovery.";
         const std::vector<std::string> options = {"--wipe_data", "--reason=fs_mgr_mount_all" };
         return reboot_into_recovery(options);
@@ -1022,7 +1026,8 @@
     }
     service->AddReapCallback([reboot_reason](const siginfo_t& siginfo) {
         if (siginfo.si_code != CLD_EXITED || siginfo.si_status != 0) {
-            if (fscrypt_is_native()) {
+            // TODO (b/122850122): support this in gsi
+            if (fscrypt_is_native() && !android::gsi::IsGsiRunning()) {
                 LOG(ERROR) << "Rebooting into recovery, reason: " << reboot_reason;
                 if (auto result = reboot_into_recovery(
                             {"--prompt_and_wipe_data", "--reason="s + reboot_reason});
diff --git a/init/first_stage_mount.cpp b/init/first_stage_mount.cpp
index 71fe401..affa39e 100644
--- a/init/first_stage_mount.cpp
+++ b/init/first_stage_mount.cpp
@@ -34,6 +34,7 @@
 #include <fs_mgr.h>
 #include <fs_mgr_dm_linear.h>
 #include <fs_mgr_overlayfs.h>
+#include <libgsi/libgsi.h>
 #include <liblp/liblp.h>
 
 #include "devices.h"
@@ -79,6 +80,7 @@
     bool IsDmLinearEnabled();
     bool GetDmLinearMetadataDevice();
     bool InitDmLinearBackingDevices(const android::fs_mgr::LpMetadata& metadata);
+    void UseGsiIfPresent();
 
     ListenerAction UeventCallback(const Uevent& uevent);
 
@@ -207,6 +209,8 @@
     }
 
     required_devices_partition_names_.emplace(super_partition_name_);
+    // When booting from live GSI images, userdata is the super device.
+    required_devices_partition_names_.emplace("userdata");
     return true;
 }
 
@@ -410,6 +414,16 @@
 // this case, we mount system first then pivot to it.  From that point on,
 // we are effectively identical to a system-as-root device.
 bool FirstStageMount::TrySwitchSystemAsRoot() {
+    auto metadata_partition = std::find_if(fstab_.begin(), fstab_.end(), [](const auto& entry) {
+        return entry.mount_point == "/metadata";
+    });
+    if (metadata_partition != fstab_.end()) {
+        if (MountPartition(&(*metadata_partition))) {
+            fstab_.erase(metadata_partition);
+            UseGsiIfPresent();
+        }
+    }
+
     auto system_partition = std::find_if(fstab_.begin(), fstab_.end(), [](const auto& entry) {
         return entry.mount_point == "/system";
     });
@@ -513,6 +527,40 @@
     return true;
 }
 
+void FirstStageMount::UseGsiIfPresent() {
+    std::string metadata_file, error;
+
+    if (!android::gsi::CanBootIntoGsi(&metadata_file, &error)) {
+        LOG(INFO) << "GSI " << error << ", proceeding with normal boot";
+        return;
+    }
+
+    auto metadata = android::fs_mgr::ReadFromImageFile(metadata_file.c_str());
+    if (!metadata) {
+        LOG(ERROR) << "GSI partition layout could not be read";
+        return;
+    }
+
+    if (!android::fs_mgr::CreateLogicalPartitions(*metadata.get(), "/dev/block/by-name/userdata")) {
+        LOG(ERROR) << "GSI partition layout could not be instantiated";
+        return;
+    }
+
+    if (!android::gsi::MarkSystemAsGsi()) {
+        PLOG(ERROR) << "GSI indicator file could not be written";
+        return;
+    }
+
+    // Replace the existing system fstab entry.
+    auto system_partition = std::find_if(fstab_.begin(), fstab_.end(), [](const auto& entry) {
+        return entry.mount_point == "/system";
+    });
+    if (system_partition != fstab_.end()) {
+        fstab_.erase(system_partition);
+    }
+    fstab_.emplace_back(BuildGsiSystemFstabEntry());
+}
+
 bool FirstStageMountVBootV1::GetDmVerityDevices() {
     std::string verity_loc_device;
     need_dm_verity_ = false;