Detect and use the CFW jit patch.

nx/include/switch/kernel/detect.h

@@ -19,3 +19,6 @@ bool kernelAbove500(void);
 bool kernelAbove600(void);
 /// Returns true if the process has a debugger attached.
 bool detectDebugger(void);
+
+/// Returns true if the kernel is patched to allow self-process-jit.
+bool detectCfwJitPatch(void);

nx/source/kernel/detect.c

@@ -1,26 +1,32 @@
 // Copyright 2017 plutoo
 #include "types.h"
+#include "result.h"
 #include "kernel/detect.h"
 #include "kernel/mutex.h"
 #include "kernel/svc.h"
+#include <malloc.h>
 
+static bool g_VersionCached = 0;
+static Mutex g_VersionMutex;
 static bool g_IsAbove200;
 static bool g_IsAbove300;
 static bool g_IsAbove400;
 static bool g_IsAbove500;
 static bool g_IsAbove600;
-static bool g_HasCached = 0;
-static Mutex g_Mutex;
 
-static void _CacheValues(void)
+static bool g_CfwJitCached = 0;
+static Mutex g_CfwJitMutex;
+static bool g_CfwJitPatchDetected;
+
+static void _CacheVersion(void)
 {
-    if (__atomic_load_n(&g_HasCached, __ATOMIC_SEQ_CST))
+    if (__atomic_load_n(&g_VersionCached, __ATOMIC_SEQ_CST))
         return;
 
-    mutexLock(&g_Mutex);
+    mutexLock(&g_VersionMutex);
 
-    if (g_HasCached) {
+    if (g_VersionCached) {
-        mutexUnlock(&g_Mutex);
+        mutexUnlock(&g_VersionMutex);
         return;
     }
 
@@ -36,33 +42,71 @@ static void _CacheValues(void)
     g_IsAbove300 |= g_IsAbove400;
     g_IsAbove200 |= g_IsAbove300;
 
-    __atomic_store_n(&g_HasCached, true, __ATOMIC_SEQ_CST);
+    __atomic_store_n(&g_VersionCached, true, __ATOMIC_SEQ_CST);
 
-    mutexUnlock(&g_Mutex);
+    mutexUnlock(&g_VersionMutex);
+}
+
+static void _CacheCfwJit(void)
+{
+    if (__atomic_load_n(&g_CfwJitCached, __ATOMIC_SEQ_CST))
+        return;
+
+    mutexLock(&g_CfwJitMutex);
+
+    if (g_CfwJitCached) {
+        mutexUnlock(&g_CfwJitMutex);
+        return;
+    }
+
+    void* heap = memalign(0x1000, 0x1000);
+
+    if (heap != NULL)
+    {
+	Handle code;
+	Result rc;
+	rc = svcCreateCodeMemory(&code, heap, 0x1000);
+
+	if (R_SUCCEEDED(rc))
+	{
+	    // On an unpatched kernel on 5.0.0 and above, this would return 0xD401.
+	    // It is not allowed for the creator-process of a CodeMemory object to use svcControlCodeMemory on it.
+	    rc = svcControlCodeMemory(code, -1, 0, 0x1000, 0);
+
+	    g_CfwJitPatchDetected = (rc == 0xF001);
+	    __atomic_store_n(&g_CfwJitCached, true, __ATOMIC_SEQ_CST);
+
+	    svcCloseHandle(code);
+	}
+
+	free(heap);
+    }
+
+    mutexUnlock(&g_CfwJitMutex);
 }
 
 bool kernelAbove200(void) {
-    _CacheValues();
+    _CacheVersion();
     return g_IsAbove200;
 }
 
 bool kernelAbove300(void) {
-    _CacheValues();
+    _CacheVersion();
     return g_IsAbove300;
 }
 
 bool kernelAbove400(void) {
-    _CacheValues();
+    _CacheVersion();
     return g_IsAbove400;
 }
 
 bool kernelAbove500(void) {
-    _CacheValues();
+    _CacheVersion();
     return g_IsAbove500;
 }
 
 bool kernelAbove600(void) {
-    _CacheValues();
+    _CacheVersion();
     return g_IsAbove600;
 }
 
@@ -71,3 +115,8 @@ bool detectDebugger(void) {
     svcGetInfo(&tmp, 8, 0, 0);
     return !!tmp;
 }
+
+bool detectCfwJitPatch(void) {
+    _CacheCfwJit();
+    return g_CfwJitPatchDetected;
+}

nx/source/kernel/jit.c

@@ -15,8 +15,9 @@ Result jitCreate(Jit* j, size_t size)
 
     // Use new jit primitive introduced in 4.0.0, if available.
     // Not usable with 5.0.0+ since svcMapJitMemory doesn't allow using that SVC under the same process which owns that object.
-    if (kernelAbove400() && !kernelAbove500() && envIsSyscallHinted(0x4B) && envIsSyscallHinted(0x4C)) {
+    if (kernelAbove400() && envIsSyscallHinted(0x4B) && envIsSyscallHinted(0x4C)
-        type = JitType_JitMemory;
+	    && (!kernelAbove500() || detectCfwJitPatch())) {
+	type = JitType_JitMemory;
     }
     // Fall back to MapProcessCodeMemory if available.
     else if (envIsSyscallHinted(0x73) && envIsSyscallHinted(0x77) && envIsSyscallHinted(0x78)