Kernel/Loader: Grab the system mode from the NCCH ExHeader.

3dsx and elf files default to system mode 2 (96MB allocated to the application).

This allows Home Menu to boot without modifications.
Closes #1849

src/citra/citra.cpp

@@ -135,17 +135,17 @@ int main(int argc, char** argv) {
         return -1;
     }
 
-    u32 system_mode;
-    Loader::ResultStatus load_result = loader->LoadKernelSystemMode(system_mode);
-    if (Loader::ResultStatus::Success != load_result) {
-        LOG_CRITICAL(Frontend, "Failed to load ROM (Error %i)!", load_result);
+    boost::optional<u32> system_mode = loader->LoadKernelSystemMode();
+
+    if (!system_mode) {
+        LOG_CRITICAL(Frontend, "Failed to load ROM (Could not determine system mode)!");
         return -1;
     }
 
-    System::Init(emu_window.get(), system_mode);
+    System::Init(emu_window.get(), system_mode.get());
     SCOPE_EXIT({ System::Shutdown(); });
 
-    load_result = loader->Load();
+    Loader::ResultStatus load_result = loader->Load();
     if (Loader::ResultStatus::Success != load_result) {
         LOG_CRITICAL(Frontend, "Failed to load ROM (Error %i)!", load_result);
         return -1;

src/citra_qt/main.cpp

@@ -299,16 +299,15 @@ bool GMainWindow::LoadROM(const std::string& filename) {
         return false;
     }
 
-    u32 system_mode;
-    Loader::ResultStatus load_result = app_loader->LoadKernelSystemMode(system_mode);
-    if (Loader::ResultStatus::Success != load_result) {
-        LOG_CRITICAL(Frontend, "Failed to load ROM!", load_result);
+    boost::optional<u32> system_mode = app_loader->LoadKernelSystemMode();
+    if (!system_mode) {
+        LOG_CRITICAL(Frontend, "Failed to load ROM!");
         QMessageBox::critical(this, tr("Error while loading ROM!"),
                               tr("Could not determine the system mode."));
         return false;
     }
 
-    if (!InitializeSystem(system_mode))
+    if (!InitializeSystem(system_mode.get()))
         return false;
 
     Loader::ResultStatus result = app_loader->Load();

src/core/loader/loader.h

@@ -9,6 +9,7 @@
 #include <memory>
 #include <string>
 #include <vector>
+#include <boost/optional.hpp>
 #include "common/common_types.h"
 #include "common/file_util.h"
 
@@ -97,13 +98,13 @@ public:
 
     /**
      * Loads the system mode that this application needs.
-     * This function defaults to 2 (96MB allocated to the application) if it can't read the information.
-     * @param system_mode Out variable where the system mode will be stored.
-     * @returns ResultStatus result of the operation
+     * This function defaults to 2 (96MB allocated to the application) if it can't read the
+     * information.
+     * @returns Optional with the kernel system mode
      */
-    virtual ResultStatus LoadKernelSystemMode(u32& system_mode) {
-        system_mode = 2; // 96MB allocated to the application.
-        return ResultStatus::Success;
+    virtual boost::optional<u32> LoadKernelSystemMode() {
+        // 96MB allocated to the application.
+        return 2;
     }
 
     /**

src/core/loader/ncch.cpp

@@ -117,12 +117,12 @@ FileType AppLoader_NCCH::IdentifyType(FileUtil::IOFile& file) {
     return FileType::Error;
 }
 
-ResultStatus AppLoader_NCCH::LoadKernelSystemMode(u32& memory_type) {
-    ResultStatus result = LoadExeFS();
-    if (result != ResultStatus::Success)
-        return result;
-    memory_type = exheader_header.arm11_system_local_caps.system_mode;
-    return ResultStatus::Success;
+boost::optional<u32> AppLoader_NCCH::LoadKernelSystemMode() {
+    if (!is_loaded) {
+        if (LoadExeFS() != ResultStatus::Success)
+            return boost::none;
+    }
+    return exheader_header.arm11_system_local_caps.system_mode.Value();
 }
 
 ResultStatus AppLoader_NCCH::LoadExec() {
@@ -285,7 +285,8 @@ ResultStatus AppLoader_NCCH::LoadExeFS() {
     LOG_DEBUG(Loader, "Core version:                %d", core_version);
     LOG_DEBUG(Loader, "Thread priority:             0x%X", priority);
     LOG_DEBUG(Loader, "Resource limit category:     %d", resource_limit_category);
-    LOG_DEBUG(Loader, "System Mode:                 %d", exheader_header.arm11_system_local_caps.system_mode);
+    LOG_DEBUG(Loader, "System Mode:                 %d",
+              exheader_header.arm11_system_local_caps.system_mode);
 
     if (exheader_header.arm11_system_local_caps.program_id != ncch_header.program_id) {
         LOG_ERROR(Loader, "ExHeader Program ID mismatch: the ROM is probably encrypted.");

src/core/loader/ncch.h

@@ -187,10 +187,9 @@ public:
 
     /**
      * Loads the Exheader and returns the system mode for this application.
-     * @param system_mode Out variable where the system mode will be stored.
-     * @return ResultStatus result of the operation
+     * @return Optional with the kernel system mode
      */
-    ResultStatus LoadKernelSystemMode(u32& system_mode);
+    boost::optional<u32> LoadKernelSystemMode();
 
     /**
      * Get the code (typically .code section) of the application