Services/AM: Implement the GetSystemUpdaterMutex function.

This function just returns a Mutex.

src/core/hle/service/am/am.cpp

@@ -1291,6 +1291,14 @@ void Module::Interface::DeleteProgram(Kernel::HLERequestContext& ctx) {
         LOG_ERROR(Service_AM, "FileUtil::DeleteDirRecursively unexpectedly failed");
 }
 
+void Module::Interface::GetSystemUpdaterMutex(Kernel::HLERequestContext& ctx) {
+    IPC::RequestParser rp(ctx, 0x412, 0, 0); // 0x04120000
+
+    IPC::RequestBuilder rb = rp.MakeBuilder(1, 2);
+    rb.Push(RESULT_SUCCESS);
+    rb.PushCopyObjects(am->system_updater_mutex);
+}
+
 void Module::Interface::GetMetaSizeFromCia(Kernel::HLERequestContext& ctx) {
     IPC::RequestParser rp(ctx, 0x0413, 0, 2); // 0x04130002
     auto cia = rp.PopObject<Kernel::ClientSession>();
@@ -1362,6 +1370,7 @@ void Module::Interface::GetMetaDataFromCia(Kernel::HLERequestContext& ctx) {
 
 Module::Module() {
     ScanForAllTitles();
+    system_updater_mutex = Kernel::Mutex::Create(false, "AM::SystemUpdaterMutex");
 }
 
 Module::~Module() = default;

src/core/hle/service/am/am.h

@@ -12,6 +12,7 @@
 #include "common/common_types.h"
 #include "core/file_sys/cia_container.h"
 #include "core/file_sys/file_backend.h"
+#include "core/hle/kernel/mutex.h"
 #include "core/hle/result.h"
 #include "core/hle/service/service.h"
 
@@ -480,6 +481,17 @@ public:
          */
         void DeleteProgram(Kernel::HLERequestContext& ctx);
 
+        /**
+         * AM::GetSystemUpdaterMutex service function
+         *  Inputs:
+         *      0 : Command header (0x04120000)
+         *  Outputs:
+         *      1 : Result, 0 on success, otherwise error code
+         *      2 : Copy handle descriptor
+         *      3 : System updater mutex
+         */
+        void GetSystemUpdaterMutex(Kernel::HLERequestContext& ctx);
+
         /**
          * AM::GetMetaSizeFromCia service function
          * Returns the size of a given CIA's meta section
@@ -522,6 +534,7 @@ private:
 
     bool cia_installing = false;
     std::array<std::vector<u64_le>, 3> am_title_list;
+    Kernel::SharedPtr<Kernel::Mutex> system_updater_mutex;
 };
 
 void InstallInterfaces(SM::ServiceManager& service_manager);

src/core/hle/service/am/am_u.cpp

@@ -70,7 +70,7 @@ AM_U::AM_U(std::shared_ptr<Module> am) : Module::Interface(std::move(am), "am:u"
         {0x040F0000, nullptr, "UpdateFirmwareAuto"},
         {0x041000C0, &AM_U::DeleteProgram, "DeleteProgram"},
         {0x04110044, nullptr, "GetTwlProgramListForReboot"},
-        {0x04120000, nullptr, "GetSystemUpdaterMutex"},
+        {0x04120000, &AM_U::GetSystemUpdaterMutex, "GetSystemUpdaterMutex"},
         {0x04130002, &AM_U::GetMetaSizeFromCia, "GetMetaSizeFromCia"},
         {0x04140044, &AM_U::GetMetaDataFromCia, "GetMetaDataFromCia"},
         {0x04150080, nullptr, "CheckDemoLaunchRights"},