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 #ifdef __AROS_USE_FULLJMP
  96     /* And clear the instruction cache (only if vectors actually contain instructions) */
  97 #if 1
  98     /*
  99      * Simply clear the entire cache...
 100      * CHECKME: Why? - sonic
 101      */
 102     CacheClearU();
 103 #else
 104     /* ...or clear the vector address range specifically */
 105     CacheClearE (__AROS_GETJUMPVEC(library,funcOffset),LIB_VECTSIZE,CACRF_ClearI|CACRF_ClearD);
 106 #endif
 107 #endif
 108
 109     /* Arbitration is no longer needed */
 110     Permit();
 111
 112     /* Sum the library up again */
 113     SumLibrary(library);
 114
 115     DSETFUNCTION("Old function: 0x%p", ret);
 116
 117     /* All done. */
 118     return ret;
 119     AROS_LIBFUNC_EXIT
 120 } /* SetFunction */
 121