From 25ba61adae313f0000ceb9f88fde705ee20fc445 Mon Sep 17 00:00:00 2001
From: Michael Scire <SciresM@gmail.com>
Date: Fri, 21 Aug 2020 03:01:39 -0700
Subject: [PATCH] loader: extend memory region descriptors a touch more
 gracefully

---
 .../loader/source/ldr_capabilities.cpp        | 27 +++++++++++++++++++
 .../loader/source/ldr_capabilities.hpp        |  2 ++
 stratosphere/loader/source/ldr_meta.cpp       |  5 ++++
 3 files changed, 34 insertions(+)

diff --git a/stratosphere/loader/source/ldr_capabilities.cpp b/stratosphere/loader/source/ldr_capabilities.cpp
index 2766fe26c..6b0600a8c 100644
--- a/stratosphere/loader/source/ldr_capabilities.cpp
+++ b/stratosphere/loader/source/ldr_capabilities.cpp
@@ -47,6 +47,9 @@ namespace ams::ldr::caps {
             return static_cast<CapabilityId>(__builtin_ctz(~cap.value));
         }
 
+        constexpr inline util::BitPack32 EmptyCapability = {~u32{}};
+        static_assert(GetCapabilityId(EmptyCapability) == CapabilityId::Empty);
+
 #define CAPABILITY_CLASS_NAME(id) Capability##id
 
 #define DEFINE_CAPABILITY_CLASS(id, member_functions)                                                                           \
@@ -407,4 +410,28 @@ namespace ams::ldr::caps {
         }
     }
 
+    void ProcessCapabilities(void *kac, size_t kac_size) {
+        util::BitPack32 *caps = reinterpret_cast<util::BitPack32 *>(kac);
+        const size_t num_caps = kac_size / sizeof(*caps);
+
+        for (size_t i = 0; i < num_caps; i++) {
+            const auto cur_cap = caps[i];
+            switch (GetCapabilityId(cur_cap)) {
+                case CapabilityId::MapRegion:
+                    {
+                        /* MapRegion was added in 8.0.0+. */
+                        /* To prevent kernel error, we should reject the descriptor on lower firmwares. */
+                        /* NOTE: We also allow it on any firmware under mesosphere, as an extension. */
+                        const bool is_allowed = (hos::GetVersion() >= hos::Version_8_0_0 || svc::IsKernelMesosphere());
+                        if (!is_allowed) {
+                            caps[i] = EmptyCapability;
+                        }
+                    }
+                    break;
+                default:
+                    break;
+            }
+        }
+    }
+
 }
diff --git a/stratosphere/loader/source/ldr_capabilities.hpp b/stratosphere/loader/source/ldr_capabilities.hpp
index 07ae0e9c9..acaa9873f 100644
--- a/stratosphere/loader/source/ldr_capabilities.hpp
+++ b/stratosphere/loader/source/ldr_capabilities.hpp
@@ -23,4 +23,6 @@ namespace ams::ldr::caps {
     u16    GetProgramInfoFlags(const void *kac, size_t kac_size);
     void   SetProgramInfoFlags(u16 flags, void *kac, size_t kac_size);
 
+    void   ProcessCapabilities(void *kac, size_t kac_size);
+
 }
diff --git a/stratosphere/loader/source/ldr_meta.cpp b/stratosphere/loader/source/ldr_meta.cpp
index 75c7ac666..2073f6d20 100644
--- a/stratosphere/loader/source/ldr_meta.cpp
+++ b/stratosphere/loader/source/ldr_meta.cpp
@@ -225,6 +225,11 @@ namespace ams::ldr {
             }
         }
 
+        /* Pre-process the capabilities. */
+        /* This is used to e.g. avoid passing memory region descriptor to older kernels. */
+        caps::ProcessCapabilities(meta->acid_kac, meta->acid->kac_size);
+        caps::ProcessCapabilities(meta->aci_kac, meta->aci->kac_size);
+
         /* Set output. */
         g_cached_program_id = loc.program_id;
         g_cached_override_status = status;