mem: implement most of StandardAllocator

This was tested using `https://github.com/node-dot-cpp/alloc-test` plus a few other by-hand tests.

It seems to work for the case we care about (sysmodules without thread cache-ing).

External users are advised to build with assertions on and contact SciresM if you find issues.

This is a lot of code to have gotten right in one go, and it was written mostly after midnight while sick, so there are probably un-noticed issues.

libraries/libstratosphere/source/os/os_virtual_address_memory.cpp

@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2018-2020 Atmosphère-NX
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include <stratosphere.hpp>
+
+namespace ams::os {
+
+    namespace {
+
+        /* TODO: Remove, add VammManager */
+        size_t GetSystemResourceSize() {
+            u64 v;
+            if (R_SUCCEEDED(svcGetInfo(std::addressof(v), InfoType_SystemResourceSizeTotal, CUR_PROCESS_HANDLE, 0))) {
+                return v;
+            } else {
+                return 0;
+            }
+        }
+
+    }
+
+    bool IsVirtualAddressMemoryEnabled() {
+        return GetSystemResourceSize() > 0;
+    }
+
+}