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> 5 6 ***************************************************************************/ 7 8 /***************************************************************************//** 9 @mainpage mach_override 10 @author Jonathan 'Wolf' Rentzsch: <http://rentzsch.com> 11 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. 16 17 Use it by #include'ing mach_override.h from your .c, .m or .mm file(s). 18 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way, this 22 code will be pure Mach, which will make it easier to use everywhere. 23 Update: MakeDataExecutable() has been replaced by 24 msync(MS_INVALIDATE).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. 42 43 ***************************************************************************/ 44 45 #ifndef _mach_override_ 46 #define _mach_override_ 47 48 #include <sys/types.h> 49 #include <mach/error.h> 50 51 #ifdef __cplusplus 52 extern "C" { 53 #endif 54 55 /** 56 Returned if the function to be overrided begins with a 'mfctr' instruction. 57 */ 58 #define err_cannot_override (err_local|1) 59 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. 65 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 NULL. 72 @result <- err_cannot_override if the original 73 function's implementation begins with 74 the 'mfctr' instruction. 75 76 ************************************************************************************/ 77 78 mach_error_t 79 mach_override_ptr( 80 void *originalFunctionAddress, 81 const void *overrideFunctionAddress, 82 void **originalFunctionReentryIsland ); 83 84 /************************************************************************************//** 85 86 87 ************************************************************************************/ 88 89 #ifdef __cplusplus 90 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 { 108 109 #define END_MACH_OVERRIDE( ORIGINAL_FUNCTION_NAME ) \ 110 } \ 111 }; \ 112 \ 113 err = mach_override_class__##ORIGINAL_FUNCTION_NAME::override((void*)ORIGINAL_FUNCTION_NAME); \ 114 } 115 116 #endif 117 118 #ifdef __cplusplus 119 } 120 #endif 121 #endif // _mach_override_ 122
