loader: fix ECS after new-ipc rewrite

The call to serviceCreate(...) tries to query pointer buffer size, but
since we haven't had a chance to return the server side of the session
yet, this deadlocks. Instead, we defer creating the session and
mounting the filesystem until the first time the ECS object is
used. If mounting the filesystem fails, the ECS is silently discarded.

stratosphere/loader/source/ldr_ecs.cpp

@@ -28,16 +28,42 @@ namespace ams::ldr::ecs {
             NON_COPYABLE(ExternalContentSource);
             NON_MOVEABLE(ExternalContentSource);
             private:
+                bool has_mounted = false;
                 char device_name[DeviceNameSizeMax];
+                os::ManagedHandle client;
+
+                Result Mount() {
+                    /* Create service. */
+                    Service srv;
+                    serviceCreate(&srv, client.Move());
+                    FsFileSystem fs = { srv };
+                    auto fs_guard = SCOPE_GUARD { fsFsClose(&fs); };
+
+                    /* Try to mount. */
+                    R_UNLESS(fsdevMountDevice(device_name, fs) >= 0, fs::ResultMountNameAlreadyExists());
+                    fs_guard.Cancel();
+
+                    this->has_mounted = true;
+                    return ResultSuccess();
+                }
             public:
-                ExternalContentSource(const char *dn) {
+                ExternalContentSource(const char *dn, os::ManagedHandle client) : client(std::move(client)) {
                     std::strncpy(this->device_name, dn, sizeof(this->device_name));
                     this->device_name[sizeof(this->device_name) - 1] = '\0';
                 }
 
+                Result EnsureMounted() {
+                    if (!this->has_mounted) {
+                        return Mount();
+                    }
+                    return ResultSuccess();
+                }
+
                 ~ExternalContentSource() {
+                    if (this->has_mounted) {
                         fsdevUnmountDevice(this->device_name);
                     }
+                }
 
                 const char *GetDeviceName() const {
                     return this->device_name;
@@ -54,6 +80,10 @@ namespace ams::ldr::ecs {
         if (it == g_map.end()) {
             return nullptr;
         }
+        if (R_FAILED(it->second.EnsureMounted())) {
+            g_map.erase(it);
+            return nullptr;
+        }
         return it->second.GetDeviceName();
     }
 
@@ -72,18 +102,13 @@ namespace ams::ldr::ecs {
         os::ManagedHandle server, client;
         R_TRY(svcCreateSession(server.GetPointer(), client.GetPointer(), 0, 0));
 
-        /* Create service. */
+        /* Do not create service yet. */
-        Service srv;
+        /* Defer until we've handed the server side back so we don't deadlock on querying pointer buffer size. */
-        serviceCreate(&srv, client.Move());
-        FsFileSystem fs = { srv };
-        auto fs_guard = SCOPE_GUARD { fsFsClose(&fs); };
-
-        /* Try to mount. */
-        R_UNLESS(fsdevMountDevice(device_name, fs) >= 0, fs::ResultMountNameAlreadyExists());
-        fs_guard.Cancel();
 
         /* Add to map. */
-        g_map.emplace(static_cast<u64>(program_id), device_name);
+        g_map.emplace(std::piecewise_construct,
+                      std::make_tuple(static_cast<u64>(program_id)),
+                      std::make_tuple(device_name, std::move(client)));
         *out = server.Move();
         return ResultSuccess();
     }