arch/m68k-all/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 #include <aros/config.h>
   9 #include <exec/execbase.h>
  10 #include <proto/intuition.h>
  11 #include <aros/libcall.h>
  12 #include <proto/exec.h>
  13 #include <exec/rawfmt.h>
  14
  15 #include "exec_debug.h"
  16 #include "exec_intern.h"
  17
  18 #ifndef DEBUG_SetFunction
  19 #   define DEBUG_SetFunction 0
  20 #endif
  21 #undef DEBUG
  22 #if DEBUG_SetFunction
  23 #   define DEBUG 1
  24 #endif
  25 #include <aros/debug.h>
  26 #undef kprintf
  27
  28 /* moveb %d0, %a3@+
  29  * rts
  30  */
  31 const ULONG m68k_string = 0x16c04e75;
  32 /* addql #1, %a3@
  33  * rts
  34  */
  35 const ULONG m68k_count  = 0x52934e75;
  36 /* jmp %a6@(-86 * 6)
  37  */
  38 const ULONG m68k_serial = 0x4eeefdfc;
  39
  40 static AROS_UFH5(APTR, myRawDoFmt,
  41         AROS_UFHA(CONST_STRPTR, fmt, A0),
  42         AROS_UFHA(APTR,        args, A1),
  43         AROS_UFHA(VOID_FUNC,  putch, A2),
  44         AROS_UFHA(APTR,      putptr, A3),
  45         AROS_UFHA(struct ExecBase *, SysBase, A6))
  46 {
  47     AROS_USERFUNC_INIT
  48
  49     switch ((IPTR)putch) {
  50     case (IPTR)RAWFMTFUNC_STRING:
  51         putch = (VOID_FUNC)&m68k_string;
  52         break;
  53     case (IPTR)RAWFMTFUNC_COUNT:
  54         putch = (VOID_FUNC)&m68k_count;
  55         break;
  56     case (IPTR)RAWFMTFUNC_SERIAL:
  57         putch = (VOID_FUNC)&m68k_serial;
  58         break;
  59     default:
  60         break;
  61     }
  62
  63     return AROS_UFC5(APTR, ((struct IntExecBase *)SysBase)->PlatformData.realRawDoFmt,
  64         AROS_UFCA(CONST_STRPTR, fmt, A0),
  65         AROS_UFCA(APTR,        args, A1),
  66         AROS_UFCA(VOID_FUNC,  putch, A2),
  67         AROS_UFCA(APTR,      putptr, A3),
  68         AROS_UFCA(struct ExecBase *, SysBase, A6));
  69
  70     AROS_USERFUNC_EXIT
  71 }
  72
  73 /*****************************************************************************
  74
  75     NAME */
  76
  77         AROS_LH3(APTR, SetFunction,
  78
  79 /*  SYNOPSIS */
  80         AROS_LHA(struct Library *, library,     A1),
  81         AROS_LHA(LONG,             funcOffset,  A0),
  82         AROS_LHA(APTR,             newFunction, D0),
  83
  84 /*  LOCATION */
  85         struct ExecBase *, SysBase, 70, Exec)
  86
  87 /*  FUNCTION
  88         Replaces a certain jumptable entry with another one. This function only
  89         Forbid()s taskswitching but doesn't Disable() interrupts. You have
  90         to do your own arbitration for functions which are callable from
  91         interrupts.
  92
  93     INPUTS
  94         library     - Pointer to library structure.
  95         funcOffset  - Offset of the jumpvector from the library base address in
  96                       bytes. It's the negative LVO (library vector offset)
  97                       multiplied with LIB_VECTSIZE.
  98         newFunction - New jumptable entry (pointer to the new function).
  99
 100     RESULT
 101         Old jumptable entry (pointer to the old function).
 102
 103     NOTES
 104         While it's more or less safe to patch a library vector with
 105         SetFunction() it's not possible to safely remove the patch later.
 106         So don't use this function if it can be avoided.
 107
 108     EXAMPLE
 109         Patch of the function Open() from dos.library:
 110         You can find the LVO of 5 in clib/dos_protos.h.
 111         SetFunction(DOSBase, -5 * LIB_VECTSIZE, NewOpen);
 112         NewOpen must be prepared with AROS_UFH macros.
 113
 114     BUGS
 115         This contains a hack to fix dos.library/ramlib attempts to
 116         setfunction exec functions. Because of this, a funcOffset
 117         of more than 32 kB be truncated. This hack will also fix
 118         other programs only using the lower 16 bits of funcOffset
 119         and leaving garbage in the upper 16 bits.
 120
 121         These programs should be fixed.
 122
 123         Also, this includes a hack to fix attempt to SetFunction the
 124         Exec/RawDoFmt() routine, which adds a wrapper to translate
 125         'magic' AROS PutChFunc vectors to real functions.
 126
 127     SEE ALSO
 128         MakeLibrary(), MakeFunctions(), SumLibrary()
 129
 130     INTERNALS
 131
 132 ******************************************************************************/
 133 {
 134     AROS_LIBFUNC_INIT
 135     APTR ret;
 136     ULONG *vecaddr;
 137
 138     D(bug("SetFunction(%s, -%lx, %lx) = ", (ULONG)library->lib_Node.ln_Name, -funcOffset, (ULONG)newFunction));
 139
 140     /*
 141         Fix dos.library/ramlib attempts to SetFunction() CloseDevice/
 142         CloseLibrary/RemDevice/RemLibrary/OpenDevice/OpenLibrary.
 143
 144         This also effectively limits the max offset to 32k, but this limit was
 145         already in the original, though not really documented.
 146
 147         What happens is this: the prototype for the funcOffset says it is a
 148         long, but the autodoc also says that only a0.w (lower 16 bits) is used.
 149         Dos.library/ramlib only sets the lower 16 bits of a0 to the required
 150         offset, without sign-extending to the upper 16 bits, in fact without
 151         even clearing them. These high 16 bits will therefore contain garbage:
 152
 153         SetFunction(exec.library, 7804fe3e, fc6524) = 30303030 CloseDevice
 154         SetFunction(exec.library, 3030fe62, fc6528) = 30303030 CloseLibrary
 155         SetFunction(exec.library, 3030fe4a, fc651c) = 30303030 RemDevice
 156         SetFunction(exec.library, 3030fe6e, fc6520) = 30303030 RemLibrary
 157         SetFunction(exec.library, 3030fe44, fc6564) = 30303030 OpenDevice
 158         SetFunction(exec.library, 3030fdd8, fc659a) = 30303030 OpenLibrary
 159
 160         In my [ldp] opinion, the autodoc should never have said that only A0.W
 161         is used for the funcOffset, while specifying a "long" in the prototype.
 162         This will stay broken and this fix will stay here until we fix
 163         dos.library/ramlib.
 164     */
 165     if (funcOffset & 0x00008000)
 166     {
 167         funcOffset |= 0xffff0000;
 168     }
 169     else
 170     {
 171         funcOffset &= 0x0000ffff;
 172     }
 173
 174     /* AOS 3.1's locale.library wants to trample over Exec/RawDoFmt.
 175      * Since the replacement does not understand the 'magic' AROS
 176      * RAWFMTFUNC_xxxx vectors, we need to install a wrapper to
 177      * translate those to real functions.
 178      *
 179      * This should not effect AROS usage of SetFunction() of
 180      * RawDoFmt, as it will only end up adding about 16 m68k
 181      * instructions of overhead.
 182      */
 183     if (library == (APTR)SysBase && funcOffset == (-87 * LIB_VECTSIZE)) {
 184         ((struct IntExecBase *)SysBase)->PlatformData.realRawDoFmt = newFunction;
 185         newFunction = myRawDoFmt;
 186     }
 187
 188     /*
 189         Arbitrate for the jumptable. This isn't enough for interrupt callable
 190         functions - but it need not be.
 191     */
 192     Forbid();
 193
 194     /* Mark the library as changed. */
 195     library->lib_Flags|=LIBF_CHANGED;
 196
 197     /* The following section is coded like this (instead of using the macros),
 198        because else gcc will output 64-bit muls instructions, that are not
 199        present on the 68060 (and will crash it). It's faster this way, too. :) */
 200     vecaddr = (APTR)((ULONG)library + funcOffset);
 201
 202     /* Get the old vector pointer */
 203     ret = (APTR)*(ULONG *)(((ULONG)vecaddr)+2);
 204
 205     /* Set new vector and jmp instruction */
 206     *(UWORD *)vecaddr = 0x4ef9;
 207     *(ULONG *)(((ULONG)vecaddr)+2) = (ULONG)newFunction;
 208
 209 #if 1
 210     CacheClearU();
 211 #else
 212     /* Can't use this because there are broken programs that
 213      * copy code and then call SetFunction().
 214      */
 215     CacheClearE(vecaddr,LIB_VECTSIZE,CACRF_ClearI|CACRF_ClearD);
 216 #endif
 217
 218     /* Arbitration is no longer needed */
 219     Permit();
 220
 221     /* Sum the library up again */
 222     SumLibrary(library);
 223
 224     D(bug("%lx\n", ret));
 225
 226     /* All done. */
 227     return ret;
 228     AROS_LIBFUNC_EXIT
 229 } /* SetFunction */
 230