core: Add dump RomFS support

This is added to LayeredFS, then the NCCH container and then the loader interface.

src/core/file_sys/layered_fs.cpp

@@ -52,7 +52,7 @@ struct FileMetadata {
 static_assert(sizeof(FileMetadata) == 0x20, "Size of FileMetadata is not correct");
 
 LayeredFS::LayeredFS(std::shared_ptr<RomFSReader> romfs_, std::string patch_path_,
-                     std::string patch_ext_path_)
+                     std::string patch_ext_path_, bool load_relocations)
     : romfs(std::move(romfs_)), patch_path(std::move(patch_path_)),
       patch_ext_path(std::move(patch_ext_path_)) {
 
@@ -64,8 +64,10 @@ LayeredFS::LayeredFS(std::shared_ptr<RomFSReader> romfs_, std::string patch_path
     root.parent = &root;
     LoadDirectory(root, 0);
 
-    LoadRelocations();
-    LoadExtRelocations();
+    if (load_relocations) {
+        LoadRelocations();
+        LoadExtRelocations();
+    }
 
     RebuildMetadata();
 }
@@ -541,4 +543,60 @@ std::size_t LayeredFS::ReadFile(std::size_t offset, std::size_t length, u8* buff
     return read_size;
 }
 
+bool LayeredFS::ExtractDirectory(Directory& current, const std::string& target_path) {
+    if (!FileUtil::CreateFullPath(target_path + current.path)) {
+        LOG_ERROR(Service_FS, "Could not create path {}", target_path + current.path);
+        return false;
+    }
+
+    constexpr std::size_t BufferSize = 0x10000;
+    std::array<u8, BufferSize> buffer;
+    for (const auto& file : current.files) {
+        // Extract file
+        const auto path = target_path + file->path;
+        LOG_INFO(Service_FS, "Extracting {} to {}", file->path, path);
+
+        FileUtil::IOFile target_file(path, "wb");
+        if (!target_file) {
+            LOG_ERROR(Service_FS, "Could not open file {}", path);
+            return false;
+        }
+
+        std::size_t written = 0;
+        while (written < file->relocation.size) {
+            const auto to_read =
+                std::min<std::size_t>(buffer.size(), file->relocation.size - written);
+            if (romfs->ReadFile(file->relocation.original_offset + written, to_read,
+                                buffer.data()) != to_read) {
+                LOG_ERROR(Service_FS, "Could not read from RomFS");
+                return false;
+            }
+
+            if (target_file.WriteBytes(buffer.data(), to_read) != to_read) {
+                LOG_ERROR(Service_FS, "Could not write to file {}", path);
+                return false;
+            }
+
+            written += to_read;
+        }
+    }
+
+    for (const auto& directory : current.directories) {
+        if (!ExtractDirectory(*directory, target_path)) {
+            return false;
+        }
+    }
+
+    return true;
+}
+
+bool LayeredFS::DumpRomFS(const std::string& target_path) {
+    std::string path = target_path;
+    if (path.back() == '/' || path.back() == '\\') {
+        path.erase(path.size() - 1, 1);
+    }
+
+    return ExtractDirectory(root, path);
+}
+
 } // namespace FileSys

src/core/file_sys/layered_fs.h

@@ -41,12 +41,14 @@ static_assert(sizeof(RomFSHeader) == 0x28, "Size of RomFSHeader is not correct")
 class LayeredFS : public RomFSReader {
 public:
     explicit LayeredFS(std::shared_ptr<RomFSReader> romfs, std::string patch_path,
-                       std::string patch_ext_path);
+                       std::string patch_ext_path, bool load_relocations = true);
     ~LayeredFS() override;
 
     std::size_t GetSize() const override;
     std::size_t ReadFile(std::size_t offset, std::size_t length, u8* buffer) override;
 
+    bool DumpRomFS(const std::string& target_path);
+
 private:
     struct File;
     struct Directory {
@@ -84,6 +86,10 @@ private:
     void BuildDirectories();
     void BuildFiles();
 
+    // Recursively extract a directory and all its contents to target_path
+    // target_path should be without trailing '/'.
+    bool ExtractDirectory(Directory& current, const std::string& target_path);
+
     void RebuildMetadata();
 
     std::shared_ptr<RomFSReader> romfs;

src/core/file_sys/ncch_container.cpp

@@ -597,7 +597,8 @@ Loader::ResultStatus NCCHContainer::LoadOverrideExeFSSection(const char* name,
     return Loader::ResultStatus::ErrorNotUsed;
 }
 
-Loader::ResultStatus NCCHContainer::ReadRomFS(std::shared_ptr<RomFSReader>& romfs_file) {
+Loader::ResultStatus NCCHContainer::ReadRomFS(std::shared_ptr<RomFSReader>& romfs_file,
+                                              bool use_layered_fs) {
     Loader::ResultStatus result = Load();
     if (result != Loader::ResultStatus::Success)
         return result;
@@ -640,7 +641,9 @@ Loader::ResultStatus NCCHContainer::ReadRomFS(std::shared_ptr<RomFSReader>& romf
     const auto path =
         fmt::format("{}mods/{:016X}/", FileUtil::GetUserPath(FileUtil::UserPath::LoadDir),
                     ncch_header.program_id & 0x00040000'FFFFFFFF);
-    if (FileUtil::Exists(path + "romfs/") || FileUtil::Exists(path + "romfs_ext/")) {
+    if (use_layered_fs &&
+        (FileUtil::Exists(path + "romfs/") || FileUtil::Exists(path + "romfs_ext/"))) {
+
         romfs_file = std::make_shared<LayeredFS>(std::move(direct_romfs), path + "romfs/",
                                                  path + "romfs_ext/");
     } else {
@@ -650,6 +653,21 @@ Loader::ResultStatus NCCHContainer::ReadRomFS(std::shared_ptr<RomFSReader>& romf
     return Loader::ResultStatus::Success;
 }
 
+Loader::ResultStatus NCCHContainer::DumpRomFS(const std::string& target_path) {
+    std::shared_ptr<RomFSReader> direct_romfs;
+    Loader::ResultStatus result = ReadRomFS(direct_romfs, false);
+    if (result != Loader::ResultStatus::Success)
+        return result;
+
+    std::shared_ptr<LayeredFS> layered_fs =
+        std::make_shared<LayeredFS>(std::move(direct_romfs), "", "", false);
+
+    if (!layered_fs->DumpRomFS(target_path)) {
+        return Loader::ResultStatus::Error;
+    }
+    return Loader::ResultStatus::Success;
+}
+
 Loader::ResultStatus NCCHContainer::ReadOverrideRomFS(std::shared_ptr<RomFSReader>& romfs_file) {
     // Check for RomFS overrides
     std::string split_filepath = filepath + ".romfs";

src/core/file_sys/ncch_container.h

@@ -247,7 +247,15 @@ public:
      * @param size The size of the romfs
      * @return ResultStatus result of function
      */
-    Loader::ResultStatus ReadRomFS(std::shared_ptr<RomFSReader>& romfs_file);
+    Loader::ResultStatus ReadRomFS(std::shared_ptr<RomFSReader>& romfs_file,
+                                   bool use_layered_fs = true);
+
+    /**
+     * Dump the RomFS of the NCCH container to the user folder.
+     * @param target_path target path to dump to
+     * @return ResultStatus result of function.
+     */
+    Loader::ResultStatus DumpRomFS(const std::string& target_path);
 
     /**
      * Get the override RomFS of the NCCH container

src/core/loader/loader.h

@@ -186,6 +186,15 @@ public:
         return ResultStatus::ErrorNotImplemented;
     }
 
+    /**
+     * Dump the RomFS of the applciation
+     * @param target_path The target path to dump to
+     * @return ResultStatus result of function
+     */
+    virtual ResultStatus DumpRomFS(const std::string& target_path) {
+        return ResultStatus::ErrorNotImplemented;
+    }
+
     /**
      * Get the update RomFS of the application
      * Since the RomFS can be huge, we return a file reference instead of copying to a buffer
@@ -196,6 +205,15 @@ public:
         return ResultStatus::ErrorNotImplemented;
     }
 
+    /**
+     * Dump the update RomFS of the applciation
+     * @param target_path The target path to dump to
+     * @return ResultStatus result of function
+     */
+    virtual ResultStatus DumpUpdateRomFS(const std::string& target_path) {
+        return ResultStatus::ErrorNotImplemented;
+    }
+
     /**
      * Get the title of the application
      * @param title Reference to store the application title into

src/core/loader/ncch.cpp

@@ -254,6 +254,18 @@ ResultStatus AppLoader_NCCH::ReadUpdateRomFS(std::shared_ptr<FileSys::RomFSReade
     return ResultStatus::Success;
 }
 
+ResultStatus AppLoader_NCCH::DumpRomFS(const std::string& target_path) {
+    return base_ncch.DumpRomFS(target_path);
+}
+
+ResultStatus AppLoader_NCCH::DumpUpdateRomFS(const std::string& target_path) {
+    u64 program_id;
+    ReadProgramId(program_id);
+    update_ncch.OpenFile(Service::AM::GetTitleContentPath(Service::FS::MediaType::SDMC,
+                                                          program_id | UPDATE_MASK));
+    return update_ncch.DumpRomFS(target_path);
+}
+
 ResultStatus AppLoader_NCCH::ReadTitle(std::string& title) {
     std::vector<u8> data;
     Loader::SMDH smdh;

src/core/loader/ncch.h

@@ -59,6 +59,10 @@ public:
 
     ResultStatus ReadUpdateRomFS(std::shared_ptr<FileSys::RomFSReader>& romfs_file) override;
 
+    ResultStatus DumpRomFS(const std::string& target_path) override;
+
+    ResultStatus DumpUpdateRomFS(const std::string& target_path) override;
+
     ResultStatus ReadTitle(std::string& title) override;
 
 private: