From b8b04d1bf34133bd61ba1c5476822674d73bf421 Mon Sep 17 00:00:00 2001
From: Michael Scire <SciresM@gmail.com>
Date: Wed, 11 Oct 2023 08:41:36 -0700
Subject: [PATCH] kern: KSupervisorPageTable now checks wxn instead of setting
 it

---
 .../mesosphere/arch/arm64/kern_cpu_system_registers.hpp   | 4 ++++
 .../arch/arm64/kern_k_supervisor_page_table.hpp           | 5 +----
 .../source/arch/arm64/kern_k_supervisor_page_table.cpp    | 8 ++------
 3 files changed, 7 insertions(+), 10 deletions(-)

diff --git a/libraries/libmesosphere/include/mesosphere/arch/arm64/kern_cpu_system_registers.hpp b/libraries/libmesosphere/include/mesosphere/arch/arm64/kern_cpu_system_registers.hpp
index 3889b264f..61e066fee 100644
--- a/libraries/libmesosphere/include/mesosphere/arch/arm64/kern_cpu_system_registers.hpp
+++ b/libraries/libmesosphere/include/mesosphere/arch/arm64/kern_cpu_system_registers.hpp
@@ -372,6 +372,10 @@ namespace ams::kern::arch::arm64::cpu {
                 this->SetBit(19, en);
                 return *this;
             }
+
+            constexpr ALWAYS_INLINE bool GetWxn() const {
+                return this->GetBits(19, 1) != 0;
+            }
     };
 
     /* Accessors for timer registers. */
diff --git a/libraries/libmesosphere/include/mesosphere/arch/arm64/kern_k_supervisor_page_table.hpp b/libraries/libmesosphere/include/mesosphere/arch/arm64/kern_k_supervisor_page_table.hpp
index c8ccca33d..73d886d84 100644
--- a/libraries/libmesosphere/include/mesosphere/arch/arm64/kern_k_supervisor_page_table.hpp
+++ b/libraries/libmesosphere/include/mesosphere/arch/arm64/kern_k_supervisor_page_table.hpp
@@ -23,9 +23,8 @@ namespace ams::kern::arch::arm64 {
     class KSupervisorPageTable {
         private:
             KPageTable m_page_table;
-            u64 m_ttbr0_identity[cpu::NumCores];
         public:
-            constexpr KSupervisorPageTable() : m_page_table(util::ConstantInitialize), m_ttbr0_identity() { /* ... */ }
+            constexpr KSupervisorPageTable() : m_page_table(util::ConstantInitialize) { /* ... */ }
 
             NOINLINE void Initialize(s32 core_id);
 
@@ -61,8 +60,6 @@ namespace ams::kern::arch::arm64 {
                 return m_page_table.GetPhysicalAddress(out, address);
             }
 
-            constexpr u64 GetIdentityMapTtbr0(s32 core_id) const { return m_ttbr0_identity[core_id]; }
-
             void DumpMemoryBlocks() const {
                 return m_page_table.DumpMemoryBlocks();
             }
diff --git a/libraries/libmesosphere/source/arch/arm64/kern_k_supervisor_page_table.cpp b/libraries/libmesosphere/source/arch/arm64/kern_k_supervisor_page_table.cpp
index 23e3541de..5f5112f8d 100644
--- a/libraries/libmesosphere/source/arch/arm64/kern_k_supervisor_page_table.cpp
+++ b/libraries/libmesosphere/source/arch/arm64/kern_k_supervisor_page_table.cpp
@@ -18,12 +18,8 @@
 namespace ams::kern::arch::arm64 {
 
     void KSupervisorPageTable::Initialize(s32 core_id) {
-        /* Get the identity mapping ttbr0. */
-        m_ttbr0_identity[core_id] = cpu::GetTtbr0El1();
-
-        /* Set sctlr_el1 */
-        cpu::SystemControlRegisterAccessor().SetWxn(true).Store();
-        cpu::EnsureInstructionConsistency();
+        /* Verify that sctlr_el1 has the wxn bit set. */
+        MESOSPHERE_ABORT_UNLESS(cpu::SystemControlRegisterAccessor().GetWxn());
 
         /* Invalidate the entire TLB. */
         cpu::InvalidateEntireTlb();