rom/exec/setfunction.c

   1 /*
   2     Copyright © 1995-2011, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: Patch a library or device function
   6     Lang: english
   7 */
   8
   9 #include <aros/debug.h>
  10 #include <exec/execbase.h>
  11 #include <proto/intuition.h>
  12 #include <aros/libcall.h>
  13 #include <proto/exec.h>
  14
  15 #include "exec_debug.h"
  16
  17 /*****************************************************************************
  18
  19     NAME */
  20
  21         AROS_LH3(APTR, SetFunction,
  22
  23 /*  SYNOPSIS */
  24         AROS_LHA(struct Library *, library,     A1),
  25         AROS_LHA(LONG,             funcOffset,  A0),
  26         AROS_LHA(APTR,             newFunction, D0),
  27
  28 /*  LOCATION */
  29         struct ExecBase *, SysBase, 70, Exec)
  30
  31 /*  FUNCTION
  32         Replaces a certain jumptable entry with another one. This function only
  33         Forbid()s taskswitching but doesn't Disable() interrupts. You have
  34         to do your own arbitration for functions which are callable from
  35         interrupts.
  36
  37     INPUTS
  38         library     - Pointer to library structure.
  39         funcOffset  - Offset of the jumpvector from the library base address in
  40                       bytes. It's the negative LVO (library vector offset)
  41                       multiplied with LIB_VECTSIZE.
  42         newFunction - New jumptable entry (pointer to the new function).
  43
  44     RESULT
  45         Old jumptable entry (pointer to the old function).
  46
  47     NOTES
  48         While it's more or less safe to patch a library vector with
  49         SetFunction() it's not possible to safely remove the patch later.
  50         So don't use this function if it can be avoided.
  51
  52     EXAMPLE
  53         Patch of the function Open() from dos.library:
  54         You can find the LVO of 5 in clib/dos_protos.h.
  55         SetFunction(DOSBase, -5 * LIB_VECTSIZE, NewOpen);
  56         NewOpen must be prepared with AROS_UFH macros.
  57
  58     BUGS
  59         None.
  60
  61     SEE ALSO
  62         MakeLibrary(), MakeFunctions(), SumLibrary()
  63
  64     INTERNALS
  65
  66 ******************************************************************************/
  67 {
  68     AROS_LIBFUNC_INIT
  69     APTR ret;
  70
  71     DSETFUNCTION("SetFunction(%s, %ld, 0x%p)", library->lib_Node.ln_Name, funcOffset, newFunction);
  72
  73     /* Vector pre-processing for non-native machines: */
  74     funcOffset = (-funcOffset) / LIB_VECTSIZE;
  75
  76     /*
  77         Arbitrate for the jumptable. This isn't enough for interrupt callable
  78         functions - but it need not be.
  79     */
  80     Forbid();
  81
  82     /* Mark the library as changed. */
  83     library->lib_Flags|=LIBF_CHANGED;
  84
  85     /* Get old vector. */
  86     ret = __AROS_GETVECADDR (library, funcOffset);
  87
  88     /* Don't forget to initialise the vector, or else there would be no actual
  89        assembler jump instruction in the vector */
  90     __AROS_INITVEC (library, funcOffset);
  91
  92     /* Write new one. */
  93     __AROS_SETVECADDR (library, funcOffset, newFunction);
  94
  95 #if 1
  96     /* And clear the instruction cache. */
  97     /* Simply clear the entire cache... */
  98     CacheClearU();
  99 #else
 100     /* ...or clear the vector address range specifically */
 101     CacheClearE (__AROS_GETJUMPVEC(library,funcOffset),LIB_VECTSIZE,CACRF_ClearI|CACRF_ClearD);
 102 #endif
 103
 104     /* Arbitration is no longer needed */
 105     Permit();
 106
 107     /* Sum the library up again */
 108     SumLibrary(library);
 109
 110     DSETFUNCTION("Old function: 0x%p", ret);
 111
 112     /* All done. */
 113     return ret;
 114     AROS_LIBFUNC_EXIT
 115 } /* SetFunction */
 116