{
Created: Friday, October 14, 1988 at 3:12 PM
    DisAsmLookup.p
    Pascal Interface to the Macintosh Libraries

    <<< DisAsmLookup - Disassembler Lookup Routines Interface File >>>
    

	Copyright Apple Computer, Inc.   1987-1988 
    All rights reserved
}


{$IFC UNDEFINED UsingIncludes}
{$SETC UsingIncludes := 0}
{$ENDC}

{$IFC NOT UsingIncludes}
    UNIT DisAsmLookup;
    INTERFACE
{$ENDC}

{$IFC UNDEFINED UsingDisAsmLookup}
{$SETC UsingDisAsmLookup := 1}

{$I+}
{$SETC DisAsmLookupIncludes := UsingIncludes}
{$SETC UsingIncludes := 1}
{$IFC UNDEFINED UsingTypes}
{$I $$Shell(PInterfaces)Types.p}
{$ENDC}
{$SETC UsingIncludes := DisAsmLookupIncludes}

TYPE

LookupRegs = (_A0_,_A1_,_A2_,_A3_,_A4_,_A5_,_A6_,_A7_,_PC_,_ABS_,_TRAP_);

DisAsmStr80 = String[80];



PROCEDURE Disassembler(DstAdjust: LONGINT;VAR BytesUsed: INTEGER;FirstByte: UNIV Ptr;
    VAR Opcode: UNIV DisAsmStr80;VAR Operand: UNIV DisAsmStr80;VAR Comment: UNIV DisAsmStr80;
    LookUpProc: UNIV Ptr);
(*
Disassembler is a Pascal routine to be called to disassemble a sequence of
bytes.  All MC68xxx, MC68881, and MC68851 instructions are supported.  The
sequence of bytes to be disassembled are pointed to by FirstByte.  BytesUsed
bytes starting at FirstByte are consumed by the disassembly, and the Opcode,
Operand, and Comment strings returned as NULL TERMINATED Pascal strings (for
easier manipulation with C).  The caller is then free to format or use the
output strings any way appropriate to the application.

Depending on the opcode and effective address(s) (EA's) to be disassembled,
the Opcode, Operand, and Comment strings contain the following information:

Case                     Opcode    Operand    Comment
=======================================================================
Non PC-relative EA's     op.sz     EA's
PC-relative EA's         op.sz     EA's       ; address
Toolbox traps            DC.W      $AXXX      ; TB XXXX
OS traps                 DC.W      $AXXX      ; OS XXXX
Invalid bytes            DC.W      $XXXX      ; ????
Invalid byte #immediate  DC.W      $XXXX,...  ; op.sz #$??XX,EA
=======================================================================

For valid disassembly of processor instructions the appropriate MC68XXX
opcode mnemonic is generated for the Opcode string along with a size
attribute when required. The source and destination EA's are generated as the
Operand along with a possible comment.  Comments start with a ';'.  Traps use
a DC.W assembler directive as the Opcode with the trap word as the Operand
and a comment indicating whether the trap is a toolbox or OS trap and what
the trap number is.  As described later the caller can generate symbolic
substitutions into EA's and provide names for traps.

Invalid instructions cause the string 'DC.W' to be returned in the Opcode
string. Operand is '$XXXX' (the invalid word) with a comment of '; ????'.
BytesUsed is 2. This is similar to the trap call case except for the comment.

A special case is made for immediate byte operands with a nonzero high order
byte.  For example, the bytes $020011FF, when actually executed, would be
interpreted as ANDI.B $FF,D0. The processor will IGNORE the high order byte
of the immediate data! Thus, the bytes may be considered as valid.  Since the
Disassembler has no way of knowing the context in which it is disassembling,
it returns the Opcode as 'DC.W' as in the normal invalid case.  However, the
Operand string shows ALL the words disassembled separated with commas and
places the possibly valid disassembly in the Operand's comment indicating the
nonzero bytes. Thus for the example $020011FF bytes, the Opcode will be
'DC.W', the Operand will be '$0200,$11FF', and the Comment 
'; ANDI.B #$??FF,D0'.  BytesUsed in this case would be 4.

Note, the Operand EA's is syntatically similar to but NOT COMPATIBLE with the
MPW assembler!  This is because the Disassembler generates byte hex constants
as "$XX" and word hex constants as "$XXXX".  Negative values (e.g., $FF or
$FFFF) produced by the Disassembler are treated as long word values by the MPW
assembler.  Thus it is assumed that Disassembler output will NOT be used as
MPW assembler input. If that is the goal, then the caller must convert strings
of the form $XX or $XXXX in the Operand string to their decimal equivalent.
The routine ModifyOperand is provided in this unit to aid with the conversion
process.

Since a PC-relative comment is an address, the only address that the
Disassembler knows about is the address of the code pointed to by FirstByte.
Generally, that may be a buffer that has no relation to "reality", i.e., the
actual code loaded into the buffer.  Therefore, to allow the address comment
to be mapped back to some actual address the caller may specify an adjustment
factor, specified by DstAdjust that is ADDED to the value that normally would
be placed in the comment.

Operand effective address strings are generated as a function of the 
effective address mode and a special case is made for A-trap opcode strings.
In places where a possible symbolic reference could be substituted for an
address (or a portion of an address), the Disassembler can call a user
specified routine to do the substitution (using th LookupProc parameter
described later).  The following table summarizes the generated effective
addresses and where symbolic substitutions (S) can be made:
     
Mode    Generated Effective Address  Effective Address with Substitution
========================================================================
  0     Dn                           Dn
  1     An                           An
  2     (An)                         (An)
  3     (An)+                        (An)+
  4     -(An)                        -(An)
  5     ¶(An)                        S(An) or just S (if An=A5, ¶³0)
 6n     ¶(An,Xn.Size*Scale)          S(An,Xn.Size*Scale)
 6n     (BD,An,Xn.Size*Scale)        (S,An,Xn.Size*Scale)
 6n     ([BD,An],Xm.Size*Scale,OD)   ([S,An],Xm.Size*Scale,OD)
 6n     ([BD,An,Xn.Size*Scale],OD)   ([S,An,Xn.Size*Scale],OD)
 70     ¶                            S
 71     ¶                            S
 72     *±¶                          S
 73     *±¶(Xn.Size*Scale)           S(Xn.Size*Scale)
 73     (*±¶,Xn.Size*Scale)          (S,Xn.Size*Scale)
 73     ([*±¶],Xm.Size*Scale,OD)     ([S],Xm.Size*Scale,OD)
 73     ([*±¶,Xn.Size*Scale],OD)     ([S,Xn.Size*Scale],OD)
 74     #data                        #data
========================================================================

For A-traps, the substitution can be performed to substitute for the DC.W
opcode string.  If the substitution is made then the Disassembler will
generate ,Sys and/or ,Immed flags as operands for Toolbox traps and
,AutoPop for OS traps when the bits in the trap word indicates these
settings.

        |         Generated          |            Substituted
        | Opcode  Operand  Comment   | Opcode  Operand        Comment
========================================================================
Toolbox | DC.W    $AXXX    ; TB XXXX | S       [,Sys][,Immed] ; AXXX
OS      | DC.W    $AXXX    ; OS XXXX | S       [,AutoPop]     ; AXXX
========================================================================

All displacements (¶, BD, OD) are hexadecimal values shown as a byte ($XX),
word ($XXXX), or long ($XXXXXXXX) as appropriate. The *Scale is suppressed if
1. The Size is W or L.  Note that effective address substitutions can only be
made for "¶(An)", "BD,An", and "*±¶" cases.
    
For all the effective address modes 5, 6n, 7n, and for A-traps, a coroutine (a
procedure) whose address is specified by the LookupProc parameter is called by
the Disassembler (if LookupProc is not NIL) to do the substitution (or A-trap
comment) with a string returned by the proc.  It is assumed that the proc
pointed to by LookupProc is a level 1 Pascal proc declared as follows:

PROCEDURE Lookup(     PC:      UNIV Ptr;        {Addr of extension/trap word}
                     BaseReg: LookupRegs;       {Base register/lookup mode  }
                     Opnd:    UNIV LongInt;     {Trap word, PC addr, disp.  }
                 VAR S:       DisAsmStr80);     {Returned substitution      }

where TYPE DisAsmStr80 = String[80];
  
or in C,

pascal void LookUp(Ptr         PC, 
                   LookupRegs  BaseReg, 
                   long        Opnd, 
                   char        *S); 

PC      = Pointer to instruction extension word or A-trap word in the
          buffer pointed to by the Disassembler's FirstByte parameter.
          
BaseReg = This determines the meaning of the Opnd value and supplies
          the base register for the "¶(An)", "BD,An", and "*±¶" cases.
          BaseReg may contain any one of the following values:
         
          _A0_   =  0 ==> A0
          _A1_   =  1 ==> A1
          _A2_   =  2 ==> A2
          _A3_   =  3 ==> A3
          _A4_   =  4 ==> A4
          _A5_   =  5 ==> A5
          _A6_   =  6 ==> A6
          _A7_   =  7 ==> A7
          _PC_   =  8 ==> PC-relative (special case)
          _ABS_  =  9 ==> Abs addr    (special case)
          _TRAP_ = 10 ==> Trap word   (special case)
          
          For absolute addressing (modes 70 and 71),  BaseReg contains _ABS_.
          For A-traps, BaseReg would contain _TRAP_.

Opnd    = The contents of this LongInt is determined by the BaseReg parameter
          just described.
       
          For BaseReg = _TRAP_ (A-traps):
              Opnd is the entire trap word. The high order 16 bits of Opnd are
              zero.

          For BaseReg = _ABS_  (absolute effective address):
              Opnd contains the (extended) 32-bit address specifed by the
              instruction's effective address.  Such addresses would generally
              be used to reference low memory globals on a Macintosh.

          For BaseReg = _PC_  (PC-relative effective address):
              Opnd contains the 32-bit address represented by "*±¶" adjusted
              by the Disassembler's DstAdjust parameter.
              
          For BaseReg = _An_  (effective address with a base register):
              Opnd contains the (sign-extended) 32-bit (base) displacement
              from the instruction's effective address.
              
              In the Macintosh environment, a BaseReg specifying A5 implies
              either global data references or Jump Table references. Positive
              Opnd values with an A5 BaseReg thus mean Jump Table references,
              while a negative offset would mean a global data reference.
              Base registers of A6 or A7 would usually mean local data.

S       = Pascal string returned from Lookup containing the effective address
          substitution string or a trap name for A-traps.  S is set to null
          PRIOR to calling Lookup.  If it is still null on return, the string
          is not used.  If not null, then for A-traps, the returned string is
          used as a opcode string. In all other cases the string is
          substituted as shown in the above table.
           
Depending on the application, the caller has three choices on how to use the
Disassembler and an associated Lookup proc:

(1). The caller can call just the Disassembler and provide his own Lookup
     proc. In that case the calling conventions discussed above must be
     followed.

(2). The caller can provide NIL for the LookupProc parameter, in which case,
     NO Lookup proc will be called.
     
(3). The caller can call first InitLookup (described below, a proc provided
     with this unit) and pass the address of this unit's standard Lookup proc
     when Disassembler is called.  In this case all the control logic to
     determine the kind of substitution to be done is provided for the caller
     and all that need to be provided by the user are routines to look up any
     or all of the following:
     
     ¥ PC-relative references
     ¥ Jump Table references
     ¥ Absolute address references
     ¥ Trap names
     ¥ References with offsets from base registers 
*)

PROCEDURE InitLookup(PCRelProc: UNIV Ptr;JTOffProc: UNIV Ptr;TrapProc: UNIV Ptr;
    AbsAddrProc: UNIV Ptr;IdProc: UNIV Ptr);
{ Prepare for use of this unit's Lookup proc.  When Disassembler is called
and the address of this unit's Lookup proc is specified, then for PC-relative,
Jump Table references, A-traps, absolute addresses, and offsets from a base
register, the associated level 1 Pascal proc specified here is called (if not
NULL -- all five addresses are preset to NULL). The calls assume the following
declarations for these procs (see Lookup, below for further details):
                             
PROCEDURE PCRelProc(Address: UNIV LongInt; 
                    VAR S:   UNIV DisAsmStr80);

PROCEDURE JTOffProc(A5JTOffset: UNIV Integer;
                    VAR S:      UNIV DisAsmStr80);

PROCEDURE TrapNameProc(TrapWord: UNIV Integer;
                       VAR S:     UNIV DisAsmStr80);
                        
PROCEDURE AbsAddrProc(AbsAddr: UNIV LongInt;
                      VAR S:   UNIV DisAsmStr80);

PROCEDURE IdProc(BaseReg: LookupRegs;
                 Offset:  UNIV LongInt;
                 VAR S:    UNIV DisAsmStr80);

or in C,

pascal void PCRelProc(long Address, char *S)

pascal void JTOffProc(short A5JTOffset, char *S)

pascal void TrapNameProc(unsigned short TrapWord, char *S)

pascal void AbsAddrProc(long AbsAddr, char *S)

pascal void IdProc(LookupRegs BaseReg, long Offset, char *S)

Note: InitLookup contains initialized data which requires initializing at load
      time (this is of concern only to users with assembler main programs.
 }

PROCEDURE Lookup(PC: UNIV Ptr;BaseReg: LookupRegs;Opnd: UNIV LongInt;VAR S: DisAsmStr80);
{ This is a standard Lookup proc available to the caller for calls to the
Disassembler.  If the caller elects to use this proc, then InitLookup MUST be
called prior to any calls to the Disassembler.  All the logic to determine the
type of lookup is done by this proc.  For PC-relative, Jump Table references,
A-traps, absolute addresses, and offsets from a base register, the associated
level 1 Pascal proc specified in the InitLookup call (if not NULL) is called.

This scheme simplifies the Lookup mechanism by allowing the caller to deal
with just the problems related to the application.
 }

PROCEDURE LookupTrapName(TrapWord: UNIV Integer;VAR S: UNIV DisAsmStr80);
{ This is a procedure provided to allow conversion of a trap instruction (in
 TrapWord) to its corresponding trap name (in S).  It is provided primarily for
 use with the Disassembler and its address may be passed to InitLookup above for
 use by this unit's Lookup routine.  Alternatively, there is nothing prohibiting
 the caller from using it directly for other purposes or by some other lookup
 proc.

Note: The tables in this proc make the size of this proc about 9500 bytes.  The
     trap names are fully spelled out in upper and lower case.
 }

PROCEDURE ModifyOperand(VAR Operand: UNIV DisAsmStr80);
{ Scan an operand string, i.e., the null terminated Pascal string returned by
the Disassembler (null MUST be present here) and modify negative hex values to
negated positive value. For example, $FFFF(A5) would be modified to -$0001(A5).
The operand to be processed is  passed as the function's parameter which is
edited "in place" and returned to the caller.

This routine is essentially a pattern matcher and attempts to only modify 2, 4,
and 8 digit hex strings in the operand that "might" be offsets from a base
register.  If the matching tests are passed, the same number of original digits
are output (because that indicates a value's size -- byte, word, or long).

For a hex string to be modified, the following tests must be passed:

¥ There must have been exactly 2, 4, or 8 digits.

  Only hex strings $XX, $XXXX, and $XXXXXXXX are possible candidates because
  that is the only way the Disassembler generates offsets.

¥ Hex string must be delimited by a "(" or a ",".

  The "(" allows offsets for $XXXX(An,...) and $XX(An,Xn) addressing modes.
  The comma allows for the MC68020 addressing forms.

¥ The "$X..." must NOT be preceded by a "±".

  This eliminates the possibility of modifying the offset of a PC-relative
  addressing mode always generated in the form "*±$XXXX".

¥ The "$X..." must NOT be preceded by a "#".

  This eliminates modifying immediate data.

¥ Value must be negative.

  Negative values are the only values we modify.  A value $FFFF is modified to
  -$0001.
 }

FUNCTION validMacsBugSymbol(symStart: UNIV Ptr;limit: UNIV Ptr;symbol: StringPtr): StringPtr; C;
{ Check that the bytes pointed to by symStart represents a valid MacsBug symbol.
The symbol must be fully contained in the bytes starting at symStart, up to,
but not including, the byte pointed to by the limit parameter.

If a valid symbol is NOT found, then NULL is returned as the function's result.
However, if a valid symbol is found, it is copied to symbol (if it is not NULL)
as a null terminated Pascal string, and return a pointer to where we think the
FOLLOWING module begins. In the "old style" cases (see below) this will always
be 8 or 16 bytes after the input symStart.  For new style Apple Pascal and C
cases this will depend on the symbol length, existence of a pad byte, and size
of the constant (literal) area.  In all cases, trailing blanks are removed from
the symbol.

A valid MacsBug symbol consists of the characters '_', '%', spaces, digits, and
upper/lower case letters in a format determined by the first two bytes of the
symbol as follows:

 1st byte  | 2nd byte  |  Byte  |
   Range   |  Range    | Length | Comments
==============================================================================
 $20 - $7F | $20 - $7F |    8   | "Old style" MacsBug symbol format
 $A0 - $FF | $20 - $7F |    8   | "Old style" MacsBug symbol format
------------------------------------------------------------------------------
 $20 - $7F | $80 - $FF |   16   | "Old style" MacApp symbol ab==>b.a
 $A0 - $FF | $80 - $FF |   16   | "Old style" MacApp symbol ab==>b.a
------------------------------------------------------------------------------
 $80       | $01 - $FF |    n   | n = 2nd byte       (Apple Compiler symbol)
 $81 - $9F | $00 - $FF |    m   | m = 1st byte & $7F (Apple Compiler symbol)
==============================================================================

The formats are determined by whether bit 7 is set in the first and second
bytes.  This bit will removed when we find it or'ed into the first and/or
second valid symbol characters.

The first two formats in the above table are the basic "old style" (pre-
existing) MacsBug formats. The first byte may or may not have bit 7 set the
second byte is a valid symbol character.  The first byte (with bit 7 removed)
and the next 7 bytes are assumed to comprise the symbol.

The second pair of formats are also "old style" formats, but used for MacApp
symbols.  Bit 7 set in the second character indicates these formats. The symbol
is assumed to be 16 bytes with the second 8 bytes preceding the first 8 bytes
in the generated symbol.  For example, 12345678abcdefgh represents the symbol
abcdefgh.12345678.

The last pair of formats are reserved by Apple and generated by the MPW Pascal
and C compilers.  In these cases the value of the first byte is always between
$80 and $9F, or with bit 7 removed, between $00 and $1F.  For $00, the second
byte is the length of the symbol with that many bytes following the second
byte (thus a max length of 255). Values $01 to $1F represent the length itself.
A pad byte may follow these variable length cases if the symbol does not end
on a word boundary.  Following the symbol and the possible pad byte is a word
containing the size of the constants (literals) generated by the compiler.

Note that if symStart actually does point to a valid MacsBug symbol, then you
may use showMacsBugSymbol to convert the MacsBug symbol bytes to a string that
could be used as a DC.B operand for disassembly purposes.  This string
explicitly shows the MacsBug symbol encodings. }

FUNCTION endOfModule(address: UNIV Ptr;limit: UNIV Ptr;symbol: StringPtr;
    VAR nextModule: UNIV Ptr): StringPtr; C;
{ Check to see if the specified memory address contains a RTS, JMP (A0) or
RTD #n instruction immediately followed by a valid MacsBug symbol.  These
sequences are the only ones which can determine an end of module when MacsBug
symbols are present.  During the check, the instruction and its following
MacsBug symbol must be fully contained in the bytes starting at the specified
address parameter, up to, but not including, the byte pointed to by the limit
parameter.

If the end of module is NOT found, then NULL is returned as the function's
result.  However, if a end of module is found, the MacsBug symbol is returned
in symbol (if it is not NULL) as a null terminated Pascal string (with trailing
blanks removed), and the functions returns the pointer to the start of the
MacsBug symbol (i.e., address+2 for RTS or JMP (A0) and address+4 for RTD #n).
This address may then be used as in input parameter to showMacsBugSymbol to
convert the MacsBug symbol to a Disassembler operand string.

Also returned in nextModule is where we think the FOLLOWING module begins. In
the "old style" cases (see validMacsBugSymbol) this will always be 8 or 16
bytes after the input address.  For new style the Apple Pascal and C cases this
will depend on the symbol length, existence of a pad byte, and size of the
constant (literal) area.  See validMacsBugSymbol for a description of valid
MacsBug symbol formats. 
 }

FUNCTION showMacsBugSymbol(symStart: UNIV Ptr;limit: UNIV Ptr;operand: StringPtr;
    VAR bytesUsed: INTEGER): StringPtr; C;
{ Format a MacsBug symbol as a operand of a DC.B directive.  The first one or two
bytes of the symbol are generated as $80+'c' if they have there high high bits
set.  All other characters are shown as characters in a string constant.  The
pad byte, if present, is one is also shown as $00.

This routine is called to check that the bytes pointed to by symStart represent
a valid MacsBug symbol.  The symbol must be fully contained in the bytes
starting at symStart, up to, but not including the byte pointed to by the limit
parameter.

When called, showMacsBugSymbol assumes that symStart is pointing at a valid
MacsBug symbol as validated by the validMacsBugSymbol or endOfModule routines.
As with validMacsBugSymbol, the symbol must be fully contained in the bytes
starting at symStart up to, but not including, the byte pointed to by the end
parameter.

The string is returned in the 'operand' parameter as a null terminated Pascal
string.  The function also returns a pointer to this string as its return
value (NULL is returned only if the byte pointed to by the limit parameter is
reached prior to processing the entire symbol -- which should not happen if
properly validated).  The number of bytes used for the symbol is returned in
bytesUsed.  Due to the way MacsBug symbols are encoded, bytesUsed may not
necessarily be the same as the length of the operand string.

A valid MacsBug symbol consists of the characters '_', '%', spaces, digits, and
upper/lower case letters in a format determined by the first two bytes of the
symbol as described in the validMacsBugSymbol routine.

 }


{$ENDC}    { UsingDisAsmLookup }

{$IFC NOT UsingIncludes}
    END.
{$ENDC}

