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togl/mach_override.h

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+// mach_override.h semver:1.2.0
+//   Copyright (c) 2003-2012 Jonathan 'Wolf' Rentzsch: http://rentzsch.com
+//   Some rights reserved: http://opensource.org/licenses/mit
+//   https://github.com/rentzsch/mach_override
+
+#ifndef		_mach_override_
+#define		_mach_override_
+
+#include <sys/types.h>
+#include <mach/error.h>
+
+#define	err_cannot_override	(err_local|1)
+
+__BEGIN_DECLS
+
+/****************************************************************************************
+	Dynamically overrides the function implementation referenced by
+	originalFunctionAddress with the implentation pointed to by overrideFunctionAddress.
+	Optionally returns a pointer to a "reentry island" which, if jumped to, will resume
+	the original implementation.
+	
+	@param	originalFunctionAddress			->	Required address of the function to
+												override (with overrideFunctionAddress).
+	@param	overrideFunctionAddress			->	Required address to the overriding
+												function.
+	@param	originalFunctionReentryIsland	<-	Optional pointer to pointer to the
+												reentry island. Can be NULL.
+	@result									<-	err_cannot_override if the original
+												function's implementation begins with
+												the 'mfctr' instruction.
+
+	************************************************************************************/
+
+    mach_error_t
+mach_override_ptr(
+	void *originalFunctionAddress,
+    const void *overrideFunctionAddress,
+    void **originalFunctionReentryIsland );
+
+__END_DECLS
+
+/****************************************************************************************
+	If you're using C++ this macro will ease the tedium of typedef'ing, naming, keeping
+	track of reentry islands and defining your override code. See test_mach_override.cp
+	for example usage.
+
+	************************************************************************************/
+ 
+#ifdef	__cplusplus
+#define MACH_OVERRIDE( ORIGINAL_FUNCTION_RETURN_TYPE, ORIGINAL_FUNCTION_NAME, ORIGINAL_FUNCTION_ARGS, ERR )		\
+{																												\
+	static ORIGINAL_FUNCTION_RETURN_TYPE (*ORIGINAL_FUNCTION_NAME##_reenter)ORIGINAL_FUNCTION_ARGS;				\
+	static bool ORIGINAL_FUNCTION_NAME##_overriden = false;														\
+	class mach_override_class__##ORIGINAL_FUNCTION_NAME {														\
+	public:																										\
+		static kern_return_t override(void *originalFunctionPtr) {												\
+			kern_return_t result = err_none;																	\
+			if (!ORIGINAL_FUNCTION_NAME##_overriden) {															\
+				ORIGINAL_FUNCTION_NAME##_overriden = true;														\
+				result = mach_override_ptr( (void*)originalFunctionPtr,											\
+											(void*)mach_override_class__##ORIGINAL_FUNCTION_NAME::replacement,	\
+											(void**)&ORIGINAL_FUNCTION_NAME##_reenter );						\
+			}																									\
+			return result;																						\
+		}																										\
+		static ORIGINAL_FUNCTION_RETURN_TYPE replacement ORIGINAL_FUNCTION_ARGS {
+
+#define END_MACH_OVERRIDE( ORIGINAL_FUNCTION_NAME )																\
+		}																										\
+	};																											\
+																												\
+	err = mach_override_class__##ORIGINAL_FUNCTION_NAME::override((void*)ORIGINAL_FUNCTION_NAME);				\
+}
+#endif
+
+#endif	//	_mach_override_