fs.mitm: Only create storage interface when needed.

stratosphere/fs_mitm/source/fsmitm_service.cpp

@@ -79,6 +79,7 @@ Result FsMitmService::OpenDataStorageByCurrentProcess(Out<std::shared_ptr<IStora
 
         Log(armGetTls(), 0x100);
         if (R_SUCCEEDED(rc)) {
+            if (Utils::HasSdRomfsContent(this->title_id)) {
                 /* TODO: Is there a sensible path that ends in ".romfs" we can use?" */
                 if (R_SUCCEEDED(Utils::OpenSdFileForAtmosphere(this->title_id, "romfs.bin", FS_OPEN_READ, &data_file))) {
                     storage = std::make_shared<IStorageInterface>(new LayeredRomFS(std::make_shared<RomInterfaceStorage>(data_storage), std::make_shared<RomFileStorage>(data_file), this->title_id));
@@ -89,6 +90,11 @@ Result FsMitmService::OpenDataStorageByCurrentProcess(Out<std::shared_ptr<IStora
                 if (out_storage.IsDomain()) {
                     out_domain_id = data_storage.s.object_id;
                 }
+            } else {
+                /* If we don't have anything to modify, there's no sense in maintaining a copy of the metadata tables. */
+                fsStorageClose(&data_storage);
+                rc = RESULT_FORWARD_TO_SESSION;
+            }
         }
     }
     
@@ -117,6 +123,7 @@ Result FsMitmService::OpenDataStorageByDataId(Out<std::shared_ptr<IStorageInterf
     rc = fsOpenDataStorageByDataIdFwd(this->forward_service.get(), storage_id, data_id, &data_storage);
 
     if (R_SUCCEEDED(rc)) {
+        if (Utils::HasSdRomfsContent(data_id)) {
             /* TODO: Is there a sensible path that ends in ".romfs" we can use?" */
             if (R_SUCCEEDED(Utils::OpenSdFileForAtmosphere(data_id, "romfs.bin", FS_OPEN_READ, &data_file))) {
                 storage = std::make_shared<IStorageInterface>(new LayeredRomFS(std::make_shared<RomInterfaceStorage>(data_storage), std::make_shared<RomFileStorage>(data_file), data_id));
@@ -126,6 +133,11 @@ Result FsMitmService::OpenDataStorageByDataId(Out<std::shared_ptr<IStorageInterf
             if (out_storage.IsDomain()) {
                 out_domain_id = data_storage.s.object_id;
             }
+        } else {
+            /* If we don't have anything to modify, there's no sense in maintaining a copy of the metadata tables. */
+            fsStorageClose(&data_storage);
+            rc = RESULT_FORWARD_TO_SESSION;
+        }
     }
     
     return rc;

stratosphere/fs_mitm/source/fsmitm_utils.cpp

@@ -201,20 +201,18 @@ Result Utils::OpenRomFSDir(FsFileSystem *fs, u64 title_id, const char *path, FsD
     return fsFsOpenDirectory(fs, safe_path, FS_DIROPEN_DIRECTORY | FS_DIROPEN_FILE, out);
 }
 
-Result Utils::HasSdRomfsContent(u64 title_id, bool *out) {
+bool Utils::HasSdRomfsContent(u64 title_id) {
-    Result rc;
     FsDir dir;
-    if (R_FAILED((rc = Utils::OpenRomFSSdDir(title_id, "", &dir)))) {
+    if (R_FAILED(Utils::OpenRomFSSdDir(title_id, "", &dir))) {
-        return rc;
+        return false;
     }
+    ON_SCOPE_EXIT {
+        fsDirClose(&dir);
+    };
     
     FsDirectoryEntry dir_entry;
     u64 read_entries;
-    if (R_SUCCEEDED((rc = fsDirRead(&dir, 0, &read_entries, 1, &dir_entry)))) {
+    return R_SUCCEEDED(fsDirRead(&dir, 0, &read_entries, 1, &dir_entry)) && read_entries == 1;
-        *out = (read_entries == 1);
-    }
-    fsDirClose(&dir);
-    return rc;
 }
 
 bool Utils::HasSdMitMFlag(u64 tid) {

stratosphere/fs_mitm/source/fsmitm_utils.hpp

@@ -28,11 +28,10 @@ class Utils {
         static Result OpenSdDirForAtmosphere(u64 title_id, const char *path, FsDir *out);
         static Result OpenRomFSSdDir(u64 title_id, const char *path, FsDir *out);        
         
-        
         static Result OpenRomFSFile(FsFileSystem *fs, u64 title_id, const char *fn, int flags, FsFile *out);
         static Result OpenRomFSDir(FsFileSystem *fs, u64 title_id, const char *path, FsDir *out);
         
-        static Result HasSdRomfsContent(u64 title_id, bool *out);
+        static bool HasSdRomfsContent(u64 title_id);
         
         /* SD card Initialization + MitM detection. */
         static void InitializeSdThreadFunc(void *args);

stratosphere/libstratosphere/include/stratosphere/mitm/mitm_session.hpp

@@ -21,6 +21,8 @@
 
 #include "mitm_query_service.hpp"
 
+#define RESULT_FORWARD_TO_SESSION 0xCAFEFC
+
 class MitmSession final : public ServiceSession {    
     private:
         /* This will be for the actual session. */
@@ -149,7 +151,7 @@ class MitmSession final : public ServiceSession {
                 }
             }
             
-            if (!found_entry) {
+            if (!found_entry || rc == RESULT_FORWARD_TO_SESSION) {
                 memcpy(armGetTls(), this->backup_tls, sizeof(this->backup_tls));
                 rc = ForwardRequest(ctx);
             }