Support custom legacy Sony devices with init.real setup

Custom ROM bring-ups of legacy Sony devices contain the following:
/init (symlink to /bin/init_sony)
/init.real (the "real" Android init)
/bin/init_sony (this was /sbin/init_sony on Android <11)

Kernel loads the ramdisk and starts /init -> /bin/init_sony
/bin/init_sony does low-level device setup (see: https://github.com/LineageOS/android_device_sony_common/blob/lineage-18.1/init/init_main.cpp)
/bin/init_sony unlinks /init and renames /init.real to /init
/bin/init_sony starts /init

Since init_sony needs to run first magiskinit needs to replace init.real instead, so add workarounds based on detection of init.real to boot patcher and uninstaller

Thanks @115ek and @bleckdeth

Fixes #3636

Co-authored-by: topjohnwu <topjohnwu@gmail.com>

native/jni/init/getinfo.cpp

@@ -252,6 +252,12 @@ bool check_two_stage() {
     if (access("/system/bin/init", F_OK) == 0)
         return true;
     // If we still have no indication, parse the original init and see what's up
-    auto init = mmap_data::ro("/.backup/init");
+    auto init = mmap_data::ro(backup_init());
     return init.contains("selinux_setup");
 }
+
+const char *backup_init() {
+    if (access("/.backup/init.real", F_OK) == 0)
+        return "/.backup/init.real";
+    return "/.backup/init";
+}

native/jni/init/init.cpp

@@ -59,7 +59,7 @@ public:
     RecoveryInit(char *argv[], BootConfig *cmd) : BaseInit(argv, cmd) {}
     void start() override {
         LOGD("Ramdisk is recovery, abort\n");
-        rename("/.backup/init", "/init");
+        rename(backup_init(), "/init");
         rm_rf("/.backup");
         exec_init();
     }

native/jni/init/init.hpp

@@ -40,6 +40,7 @@ bool unxz(int fd, const uint8_t *buf, size_t size);
 void load_kernel_info(BootConfig *config);
 bool check_two_stage();
 void setup_klog();
+const char *backup_init();
 
 /***************
  * Base classes

native/jni/init/mount.cpp

@@ -289,7 +289,7 @@ void RootFSInit::early_mount() {
     self = mmap_data::ro("/init");
 
     LOGD("Restoring /init\n");
-    rename("/.backup/init", "/init");
+    rename(backup_init(), "/init");
 
     mount_with_dt();
 }

native/jni/init/twostage.cpp

@@ -61,7 +61,7 @@ void FirstStageInit::prepare() {
         xmkdirs(FSR "/system/bin", 0755);
         rename("/init" /* magiskinit */, FSR "/system/bin/init");
         symlink("/system/bin/init", FSR "/init");
-        rename("/.backup/init", "/init");
+        rename(backup_init(), "/init");
 
         rename("/.backup", FSR "/.backup");
         rename("/overlay.d", FSR "/overlay.d");
@@ -71,7 +71,7 @@ void FirstStageInit::prepare() {
         xmkdir("/system", 0755);
         xmkdir("/system/bin", 0755);
         rename("/init" /* magiskinit */ , "/system/bin/init");
-        rename("/.backup/init", "/init");
+        rename(backup_init(), "/init");
     }
 
     char fstab_file[128];

native/jni/magiskboot/main.cpp

@@ -58,9 +58,9 @@ Supported actions:
       extract [ENTRY OUT]
         Extract ENTRY to OUT, or extract all entries to current directory
       test
-        Test the current cpio's patch status
-        Return values:
-        0:stock    1:Magisk    2:unsupported (phh, SuperSU, Xposed)
+        Test the current cpio's status
+        Return value is 0 or bitwise or-ed of following values:
+        0x1:Magisk    0x2:unsupported    0x4:Sony
       patch
         Apply ramdisk patches
         Configure with env variables: KEEPVERITY KEEPFORCEENCRYPT

native/jni/magiskboot/ramdisk.cpp

@@ -59,11 +59,12 @@ void magisk_cpio::patch() {
     }
 }
 
-#define STOCK_BOOT        0
 #define MAGISK_PATCHED    (1 << 0)
 #define UNSUPPORTED_CPIO  (1 << 1)
+#define SONY_INIT         (1 << 2)
 
 int magisk_cpio::test() {
+    int ret = 0;
     for (auto file : UNSUPPORT_LIST) {
         if (exists(file)) {
             return UNSUPPORTED_CPIO;
@@ -71,10 +72,13 @@ int magisk_cpio::test() {
     }
     for (auto file : MAGISK_LIST) {
         if (exists(file)) {
-            return MAGISK_PATCHED;
+            ret |= MAGISK_PATCHED;
+            break;
         }
     }
-    return STOCK_BOOT;
+    if (exists("init.real"))
+        ret |= SONY_INIT;
+    return ret;
 }
 
 #define for_each_line(line, buf, size) \