The Tor Browser: xpcom/build/mach_override.h@6474c204b198

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     1 /*******************************************************************************

     2 	mach_override.h

     3 		Copyright (c) 2003-2009 Jonathan 'Wolf' Rentzsch: <http://rentzsch.com>

     4 		Some rights reserved: <http://opensource.org/licenses/mit-license.php>

     6 	***************************************************************************/

     8 /***************************************************************************//**

     9 	@mainpage	mach_override

    10 	@author		Jonathan 'Wolf' Rentzsch: <http://rentzsch.com>

    12 	This package, coded in C to the Mach API, allows you to override ("patch")

    13 	program- and system-supplied functions at runtime. You can fully replace

    14 	functions with your implementations, or merely head- or tail-patch the

    15 	original implementations.

    17 	Use it by #include'ing mach_override.h from your .c, .m or .mm file(s).

    19 	@todo	Discontinue use of Carbon's MakeDataExecutable() and

    20 			CompareAndSwap() calls and start using the Mach equivalents, if they

    21 			exist. If they don't, write them and roll them in. That way, this

    22 			code will be pure Mach, which will make it easier to use everywhere.

    23 			Update: MakeDataExecutable() has been replaced by

    24 			msync(MS_INVALIDATE). There is an OSCompareAndSwap in libkern, but

    25 			I'm currently unsure if I can link against it. May have to roll in

    26 			my own version...

    27 	@todo	Stop using an entire 4K high-allocated VM page per 28-byte escape

    28 			branch island. Done right, this will dramatically speed up escape

    29 			island allocations when they number over 250. Then again, if you're

    30 			overriding more than 250 functions, maybe speed isn't your main

    31 			concern...

    32 	@todo	Add detection of: b, bl, bla, bc, bcl, bcla, bcctrl, bclrl

    33 			first-instructions. Initially, we should refuse to override

    34 			functions beginning with these instructions. Eventually, we should

    35 			dynamically rewrite them to make them position-independent.

    36 	@todo	Write mach_unoverride(), which would remove an override placed on a

    37 			function. Must be multiple-override aware, which means an almost

    38 			complete rewrite under the covers, because the target address can't

    39 			be spread across two load instructions like it is now since it will

    40 			need to be atomically updatable.

    41 	@todo	Add non-rentry variants of overrides to test_mach_override.

    43 	***************************************************************************/

    45 #ifndef		_mach_override_

    46 #define		_mach_override_

    48 #include <sys/types.h>

    49 #include <mach/error.h>

    51 #ifdef	__cplusplus

    52 	extern	"C"	{

    53 #endif

    55 /**

    56 	Returned if the function to be overrided begins with a 'mfctr' instruction.

    57 */

    58 #define	err_cannot_override	(err_local|1)

    60 /************************************************************************************//**

    61 	Dynamically overrides the function implementation referenced by

    62 	originalFunctionAddress with the implentation pointed to by overrideFunctionAddress.

    63 	Optionally returns a pointer to a "reentry island" which, if jumped to, will resume

    64 	the original implementation.

    66 	@param	originalFunctionAddress			->	Required address of the function to

    67 												override (with overrideFunctionAddress).

    68 	@param	overrideFunctionAddress			->	Required address to the overriding

    69 												function.

    70 	@param	originalFunctionReentryIsland	<-	Optional pointer to pointer to the

    71 												reentry island. Can be nullptr.

    72 	@result									<-	err_cannot_override if the original

    73 												function's implementation begins with

    74 												the 'mfctr' instruction.

    76 	************************************************************************************/

    78     mach_error_t

    79 mach_override_ptr(

    80 	void *originalFunctionAddress,

    81     const void *overrideFunctionAddress,

    82     void **originalFunctionReentryIsland );

    84 /************************************************************************************//**

    87 	************************************************************************************/

    89 #ifdef	__cplusplus

    91 #define MACH_OVERRIDE( ORIGINAL_FUNCTION_RETURN_TYPE, ORIGINAL_FUNCTION_NAME, ORIGINAL_FUNCTION_ARGS, ERR )			\

    92 	{																												\

    93 		static ORIGINAL_FUNCTION_RETURN_TYPE (*ORIGINAL_FUNCTION_NAME##_reenter)ORIGINAL_FUNCTION_ARGS;				\

    94 		static bool ORIGINAL_FUNCTION_NAME##_overriden = false;														\

    95 		class mach_override_class__##ORIGINAL_FUNCTION_NAME {														\

    96 		public:																										\

    97 			static kern_return_t override(void *originalFunctionPtr) {												\

    98 				kern_return_t result = err_none;																	\

    99 				if (!ORIGINAL_FUNCTION_NAME##_overriden) {															\

   100 					ORIGINAL_FUNCTION_NAME##_overriden = true;														\

   101 					result = mach_override_ptr( (void*)originalFunctionPtr,											\

   102 												(void*)mach_override_class__##ORIGINAL_FUNCTION_NAME::replacement,	\

   103 												(void**)&ORIGINAL_FUNCTION_NAME##_reenter );						\

   104 				}																									\

   105 				return result;																						\

   106 			}																										\

   107 			static ORIGINAL_FUNCTION_RETURN_TYPE replacement ORIGINAL_FUNCTION_ARGS {

   109 #define END_MACH_OVERRIDE( ORIGINAL_FUNCTION_NAME )																	\

   110 			}																										\

   111 		};																											\

   112 																													\

   113 		err = mach_override_class__##ORIGINAL_FUNCTION_NAME::override((void*)ORIGINAL_FUNCTION_NAME);				\

   114 	}

   116 #endif

   118 #ifdef	__cplusplus

   119 	}

   120 #endif

   121 #endif	//	_mach_override_

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