rom/exec/setfunction.c

   1 /*
   2     Copyright © 1995-2001, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: Patch a library or device function
   6     Lang: english
   7 */
   8 #include <aros/config.h>
   9 #include <exec/execbase.h>
  10 #include <aros/libcall.h>
  11 #include <proto/exec.h>
  12 #include "exec_debug.h"
  13
  14 #ifndef DEBUG_SetFunction
  15 #   define DEBUG_SetFunction 0
  16 #endif
  17 #undef DEBUG
  18 #if DEBUG_SetFunction
  19 #   define DEBUG 1
  20 #endif
  21 #include <aros/debug.h>
  22 #undef kprintf
  23
  24 /*****************************************************************************
  25
  26     NAME */
  27
  28         AROS_LH3(APTR, SetFunction,
  29
  30 /*  SYNOPSIS */
  31         AROS_LHA(struct Library *, library,     A1),
  32         AROS_LHA(LONG,             funcOffset,  A0),
  33         AROS_LHA(APTR,             newFunction, D0),
  34
  35 /*  LOCATION */
  36         struct ExecBase *, SysBase, 70, Exec)
  37
  38 /*  FUNCTION
  39         Replaces a certain jumptable entry with another one. This function only
  40         Forbid()s taskswitching but doesn't Disable() interrupts. You have
  41         to do your own arbitration for functions which are callable from
  42         interrupts.
  43
  44     INPUTS
  45         library     - Pointer to library structure.
  46         funcOffset  - Offset of the jumpvector from the library base address in
  47                       bytes.
  48         newFunction - New jumptable entry (pointer to the new function).
  49
  50     RESULT
  51         Old jumptable entry (pointer to the old function).
  52
  53     NOTES
  54         While it's more or less safe to patch a library vector with
  55         SetFunction() it's not possible to safely remove the patch later.
  56         So don't use this function if it can be avoided.
  57
  58     EXAMPLE
  59
  60     BUGS
  61         On native builds, this contains a hack to fix dos.library/ramlib
  62         attempts to setfunction exec functions. Because of this, a funcOffset
  63         of more than 32 kB be truncated. This hack will also fix other programs
  64         only using the lower 16 bits of funcOffset and leaving garbage in the
  65         upper 16 bits. These programs should be fixed.
  66
  67     SEE ALSO
  68         MakeLibrary(), MakeFunctions(), SumLibrary().
  69
  70     INTERNALS
  71
  72 ******************************************************************************/
  73 {
  74     AROS_LIBFUNC_INIT
  75     APTR ret;
  76 #if (AROS_FLAVOUR & AROS_FLAVOUR_NATIVE)
  77     ULONG *vecaddr;
  78 #endif
  79
  80     D(bug("SetFunction(%s, %lx, %lx) = ", (ULONG)library->lib_Node.ln_Name, funcOffset, (ULONG)newFunction));
  81
  82 #if (AROS_FLAVOUR & AROS_FLAVOUR_NATIVE)
  83     /*
  84         Fix dos.library/ramlib attempts to SetFunction() CloseDevice/
  85         CloseLibrary/RemDevice/RemLibrary/OpenDevice/OpenLibrary.
  86
  87         This also effectively limits the max offset to 32k, but this limit was
  88         already in the original, though not really documented.
  89
  90         What happens is this: the prototype for the funcOffset says it is a
  91         long, but the autodoc also says that only a0.w (lower 16 bits) is used.
  92         Dos.library/ramlib only sets the lower 16 bits of a0 to the required
  93         offset, without sign-extending to the upper 16 bits, in fact without
  94         even clearing them. These high 16 bits will therefore contain garbage:
  95
  96         SetFunction(exec.library, 7804fe3e, fc6524) = 30303030 CloseDevice
  97         SetFunction(exec.library, 3030fe62, fc6528) = 30303030 CloseLibrary
  98         SetFunction(exec.library, 3030fe4a, fc651c) = 30303030 RemDevice
  99         SetFunction(exec.library, 3030fe6e, fc6520) = 30303030 RemLibrary
 100         SetFunction(exec.library, 3030fe44, fc6564) = 30303030 OpenDevice
 101         SetFunction(exec.library, 3030fdd8, fc659a) = 30303030 OpenLibrary
 102
 103         In my [ldp] opinion, the autodoc should never have said that only A0.W
 104         is used for the funcOffset, while specifying a "long" in the prototype.
 105         This will stay broken and this fix will stay here until we fix
 106         dos.library/ramlib.
 107     */
 108     if (funcOffset & 0x00008000)
 109     {
 110         funcOffset |= 0xffff0000;
 111     }
 112     else
 113     {
 114         funcOffset &= 0x0000ffff;
 115     }
 116
 117 #else
 118     /* Vector pre-processing for non-native machines: */
 119     funcOffset = (-funcOffset) / LIB_VECTSIZE;
 120
 121 #endif
 122
 123     /*
 124         Arbitrate for the jumptable. This isn't enough for interrupt callable
 125         functions - but it need not be.
 126     */
 127     Forbid();
 128
 129     /* Mark the library as changed. */
 130     library->lib_Flags|=LIBF_CHANGED;
 131
 132 #if (AROS_FLAVOUR & AROS_FLAVOUR_NATIVE)
 133     /* The following section is coded like this (instead of using the macros),
 134        because else gcc will output 64-bit muls instructions, that are not
 135        present on the 68060 (and will crash it). It's faster this way, too. :) */
 136     vecaddr = (APTR)((ULONG)library + funcOffset);
 137
 138     /* Get the old vector pointer */
 139     ret = (APTR)*(ULONG *)(((ULONG)vecaddr)+2);
 140
 141     /* Set new vector and jmp instruction */
 142     *(UWORD *)vecaddr = 0x4ef9;
 143     *(ULONG *)(((ULONG)vecaddr)+2) = (ULONG)newFunction;
 144
 145 #else /* non-native section follows */
 146     /* Get old vector. */
 147     ret = __AROS_GETVECADDR (library, funcOffset);
 148
 149     /* Don't forget to initialise the vector, or else there would be no actual
 150        assembler jump instruction in the vector */
 151     __AROS_INITVEC (library, funcOffset);
 152
 153     /* Write new one. */
 154     __AROS_SETVECADDR (library, funcOffset, newFunction);
 155
 156 #endif /* end if system specific sections */
 157
 158 #if 1
 159     /* And clear the instruction cache. */
 160     /* Simply clear the entire cache... */
 161     CacheClearU();
 162 #else
 163     /* ...or clear the vector address range specifically */
 164     CacheClearE (__AROS_GETJUMPVEC(library,funcOffset),LIB_VECTSIZE,CACRF_ClearI|CACRF_ClearD);
 165 #endif
 166
 167     /* Arbitration is no longer needed */
 168     Permit();
 169
 170     /* Sum the library up again */
 171     SumLibrary(library);
 172
 173     D(bug("%lx\n", ret));
 174
 175     /* All done. */
 176     return ret;
 177     AROS_LIBFUNC_EXIT
 178 } /* SetFunction */
 179