From 3337e782e6f8462c6a2954617e4c59c01ec502be Mon Sep 17 00:00:00 2001
From: Yifan Hong <elsk@google.com>
Date: Wed, 28 Oct 2020 18:27:43 -0700
Subject: [PATCH] Move e2fsck into /first_stage_ramdisk.

On devices without a dedicated recovery partition, it is possible that
e2fsck exists in /system/bin, not /first_stage_ramdisk/system/bin, if
it is using generic ramdisk. When force_normal_boot, /system/bin/e2fsck
would not exist during first stage mount.

In this case, move /first_stage_ramdisk/system/bin/e2fsck to
/system/bin/e2fsck before switching root into /first_stage_ramdisk.
Abort if the operation fails.

On devices launching with R, e2fsck should already exist in the correct
place, so skip moving if force_normal_boot and
/first_stage_ramdisk/system/bin/e2fsck already exists.

On devices launching before R, it is possible that /system/bin/e2fsck
does not exist. Skip moving if force_normal_boot and /system/bin/e2fsck
does not exist.

Fixes: 171326057
Test: boot with GKI and move_recover_resources_to_vendor_boot, and
      check serial output

Change-Id: I8008a4cad54c7c74a84cbcabe56723bf0e193025
---
 init/first_stage_init.cpp | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/init/first_stage_init.cpp b/init/first_stage_init.cpp
index 554f301cc..d2a952fc2 100644
--- a/init/first_stage_init.cpp
+++ b/init/first_stage_init.cpp
@@ -99,6 +99,34 @@ bool ForceNormalBoot(const std::string& cmdline) {
     return cmdline.find("androidboot.force_normal_boot=1") != std::string::npos;
 }
 
+// Move e2fsck before switching root, so that it is available at the same path
+// after switching root.
+void PrepareSwitchRoot() {
+    constexpr const char* src = "/system/bin/e2fsck";
+    constexpr const char* dst = "/first_stage_ramdisk/system/bin/e2fsck";
+
+    if (access(dst, X_OK) == 0) {
+        LOG(INFO) << dst << " already exists and it can be executed";
+        return;
+    }
+
+    if (access(src, F_OK) != 0) {
+        PLOG(INFO) << "Not moving " << src << " because it cannot be accessed";
+        return;
+    }
+
+    auto dst_dir = android::base::Dirname(dst);
+    std::error_code ec;
+    if (!fs::create_directories(dst_dir, ec)) {
+        LOG(FATAL) << "Cannot create " << dst_dir << ": " << ec.message();
+    }
+    if (rename(src, dst) != 0) {
+        PLOG(FATAL) << "Cannot move " << src << " to " << dst
+                    << ". Either install e2fsck.ramdisk so that it is at the correct place (" << dst
+                    << "), or make ramdisk writable";
+    }
+}
+
 }  // namespace
 
 std::string GetModuleLoadList(bool recovery, const std::string& dir_path) {
@@ -298,6 +326,7 @@ int FirstStageMain(int argc, char** argv) {
 
     if (ForceNormalBoot(cmdline)) {
         mkdir("/first_stage_ramdisk", 0755);
+        PrepareSwitchRoot();
         // SwitchRoot() must be called with a mount point as the target, so we bind mount the
         // target directory to itself here.
         if (mount("/first_stage_ramdisk", "/first_stage_ramdisk", nullptr, MS_BIND, nullptr) != 0) {