From 5bcc79ef80b393ee491a11e6bb1238e00d5e1c57 Mon Sep 17 00:00:00 2001
From: Billy Laws <blaws05@gmail.com>
Date: Wed, 5 Apr 2023 15:06:13 +0100
Subject: [PATCH] Ensure SVC trampoline is always correctly sized

Despite the trampoline size being hardcoded, it was previously dynamic and could change based off of the value stored in the target register potentially leading to instructions being missed.
---
 app/src/main/cpp/skyline/nce.cpp | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/app/src/main/cpp/skyline/nce.cpp b/app/src/main/cpp/skyline/nce.cpp
index 08d9b35f..695339eb 100644
--- a/app/src/main/cpp/skyline/nce.cpp
+++ b/app/src/main/cpp/skyline/nce.cpp
@@ -256,7 +256,7 @@ namespace skyline::nce {
         staticNce = nullptr;
     }
 
-    constexpr size_t TrampolineSize{17}; // Size of the main SVC trampoline function in u32 units
+    constexpr size_t TrampolineSize{18}; // Size of the main SVC trampoline function in u32 units
 
     /**
      * @brief Writes a trampoline to the given target address that saves the current context and calls the given function
@@ -280,9 +280,12 @@ namespace skyline::nce {
         *code++ = 0xA9BF0BE1; // STP X1, X2, [SP, #-16]!
 
         /* Jump to SvcHandler */
-        for (const auto &mov : instructions::MoveRegister(registers::X2, target))
+        for (const auto &mov : instructions::MoveRegister(registers::X2, target)) {
             if (mov)
                 *code++ = mov;
+            else
+                *code++ = 0xD503201F; // NOP
+        }
         *code++ = 0xD63F0040; // BLR X2
 
         /* Restore Skyline TLS + guest SP */
@@ -297,7 +300,7 @@ namespace skyline::nce {
         return code;
     }
 
-    constexpr size_t RescaleClockSize{17}; //!< The size of the RescaleClock function in 32-bit ARMv8 instructions
+    constexpr size_t RescaleClockSize{19}; //!< The size of the RescaleClock function in 32-bit ARMv8 instructions
 
     /**
      * @brief Writes instructions to rescale the host clock to Tegra X1 levels
@@ -316,9 +319,12 @@ namespace skyline::nce {
         *code++ = 0xF2E14F80; // MOVK X0, #2684, LSL #48
 
         /* Load clock frequency value */
-        for (const auto &mov : instructions::MoveRegister(registers::X1, util::ClockFrequency))
+        for (const auto &mov : instructions::MoveRegister(registers::X1, util::ClockFrequency)) {
             if (mov)
                 *code++ = mov;
+            else
+                *code++ = 0xD503201F; // NOP
+        }
 
         /* Multiply clock frequency by magic constant */
         *code++ = 0xD345FC21; // LSR X1, X1, #5