Quelle  mach_override.h   Sprache: C

/*******************************************************************************
mach_override.h
Copyright (c) 2003-2009 Jonathan 'Wolf' Rentzsch: <http://rentzsch.com>
Some rights reserved: <http://opensource.org/licenses/mit-license.php>

***************************************************************************/

/***************************************************************************//**
 @mainpage mach_override
 @author  Jonathan 'Wolf' Rentzsch: <http://rentzsch.com>

 This package, coded in C to the Mach API, allows you to override ("patch")
 program- and system-supplied functions at runtime. You can fully replace
 functions with your implementations, or merely head- or tail-patch the
 original implementations.

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

 @todo Discontinue use of Carbon's MakeDataExecutable() and
   CompareAndSwap() calls and start using the Mach equivalents, if they
   exist. If they don't, write them and roll them in. That way, this
   code will be pure Mach, which will make it easier to use everywhere.
   Update: MakeDataExecutable() has been replaced by
   msync(MS_INVALIDATE). There is an OSCompareAndSwap in libkern, but
   I'm currently unsure if I can link against it. May have to roll in
   my own version...
 @todo Stop using an entire 4K high-allocated VM page per 28-byte escape
   branch island. Done right, this will dramatically speed up escape
   island allocations when they number over 250. Then again, if you're
   overriding more than 250 functions, maybe speed isn't your main
   concern...
 @todo Add detection of: b, bl, bla, bc, bcl, bcla, bcctrl, bclrl
   first-instructions. Initially, we should refuse to override
   functions beginning with these instructions. Eventually, we should
   dynamically rewrite them to make them position-independent.
 @todo Write mach_unoverride(), which would remove an override placed on a
   function. Must be multiple-override aware, which means an almost
   complete rewrite under the covers, because the target address can't
   be spread across two load instructions like it is now since it will
   need to be atomically updatable.
 @todo Add non-rentry variants of overrides to test_mach_override.

 ***************************************************************************/

#ifndef  _mach_override_
#define  _mach_override_

#include <sys/types.h>
#include <mach/error.h>

#ifdef __cplusplus
 extern "C" {
#endif

/**
Returned if the function to be overrided begins with a 'mfctr' instruction.
*/
#define err_cannot_override (err_local|1)

/************************************************************************************//**
 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 nullptr.
 @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 );

/************************************************************************************//**


 ************************************************************************************/

#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

#ifdef __cplusplus
 }
#endif
#endif // _mach_override_