kernel: svcGetInfo 33 is a page granule; give 29/30 a real region

The SDK checks module address/size against (id33 - 1) when initialising
DSOs, so id 33 is a page granule: return 0x1000. Report ids 29/30 as the
upper half of the alias region (a plausible VAMM address-space region,
backed through MapPhysicalMemory) instead of an empty region.

2 files changed, 18 insertions, 14 deletions

diff --git a/src/core/hle/kernel/svc/svc_info.cpp b/src/core/hle/kernel/svc/svc_info.cpp
index aec31ca148..97ad6bbdbc 100644
--- a/src/core/hle/kernel/svc/svc_info.cpp
+++ b/src/core/hle/kernel/svc/svc_info.cpp
@@ -70,19 +70,23 @@ Result GetInfo(Core::System& system, u64* result, InfoType info_id_type, Handle
             *result = process->GetPageTable().GetHeapRegionSize();
             R_SUCCEED();
         case InfoType::Nx2RegionAddress:
-            // Unknown Switch 2 region; report an empty one just past the alias region.
-            *result = GetInteger(process->GetPageTable().GetAliasRegionStart()) +
-                      process->GetPageTable().GetAliasRegionSize();
-            LOG_WARNING(Kernel_SVC, "(STUBBED) Switch 2 InfoType 29, returning {:#x}", *result);
-            R_SUCCEED();
-        case InfoType::Nx2RegionSize:
-            LOG_WARNING(Kernel_SVC, "(STUBBED) Switch 2 InfoType 30, returning 0");
-            *result = 0;
+        case InfoType::Nx2RegionSize: {
+            // Looks like the region Switch 2 VAMM reserves address space in (a title asks for a
+            // ~7.5 GiB reservation). VAMM backs it with MapPhysicalMemory, which only works in
+            // the alias region here, so hand out the upper half of the alias region.
+            auto& page_table = process->GetPageTable();
+            const u64 half = page_table.GetAliasRegionSize() / 2;
+            *result = info_id_type == InfoType::Nx2RegionAddress
+                          ? GetInteger(page_table.GetAliasRegionStart()) + half
+                          : half;
+            LOG_WARNING(Kernel_SVC, "(STUBBED) Switch 2 InfoType {}, returning {:#x}",
+                        static_cast<u32>(info_id_type), *result);
             R_SUCCEED();
+        }
         case InfoType::Nx2VammSize:
-            // Used as the size of VAMM's initial MapPhysicalMemory, so it must be non-zero.
-            // The real value is unknown; 2 MiB is the smallest size that keeps it block-aligned.
-            *result = 0x200000;
+            // A page granule: the SDK checks module addresses/sizes against (value - 1) and
+            // VAMM maps one granule up front. 4 KiB matches what Switch 1 kernels use.
+            *result = Core::Memory::YUZU_PAGESIZE;
             LOG_WARNING(Kernel_SVC, "(STUBBED) Switch 2 InfoType 33, returning {:#x}", *result);
             R_SUCCEED();
         case InfoType::AslrRegionAddress:
diff --git a/src/core/hle/kernel/svc_types.h b/src/core/hle/kernel/svc_types.h
index 4734522b35..8badaa6b2e 100644
--- a/src/core/hle/kernel/svc_types.h
+++ b/src/core/hle/kernel/svc_types.h
@@ -158,11 +158,11 @@ enum class InfoType : u32 {
     IoRegionHint = 27,
     AliasRegionExtraSize = 28,
     // Switch 2 kernels: address/size of a region the SDK queries between the alias and
-    // ASLR regions during nnosInitialize. Meaning not known yet.
+    // ASLR regions during nnosInitialize; likely the VAMM address-space region.
     Nx2RegionAddress = 29,
     Nx2RegionSize = 30,
-    // Switch 2 kernels: queried by nn::os::detail::VammManager::Initialize and used as the size
-    // of its first MapPhysicalMemory. Meaning not known yet.
+    // Switch 2 kernels: a page granule. The SDK aligns module ranges and VAMM's first
+    // MapPhysicalMemory to it.
     Nx2VammSize = 33,
 
     TransferMemoryHint = 34,