dis88.9

操作系统设计与实现源码

.CD "dis88 \(en disassembler [IBM]"
.SX "dis88\fR [\fB\(eno\fR] \fIinfile\fR [\fIoutfile\fR]"
.FL "\(eno" "List the object code along with the assembly code"
.EX "dis88 a.out >listing" "Disassemble \fIa.out\fR"
.EX "dis88 \(eno a.out listing" "Ditto, but with object code"
.PP
\fIDis88\fR disassembles 8088 object code to the assembly language format
used by 
.MX  .
It makes full use of
symbol table information, supports separate 
instruction and data space, and generates synthetic labels when needed. 
It does not support 8087 mnemonics, symbolic data segment references, or 
the ESC mnemonic.
.PP
The program is invoked by:
.HS
.Cx "dis88 [\(eno] infile [outfile]"
.HS
The \(eno flag causes object code to be listed. 
If no outfile is given, \fIstdout\fR is used.
.PP
The text segment of an object file is always padded to an even address.
In addition, if the file has split I/D space, the text segment will be padded
to a paragraph boundary (i.e., an address divisible by 16). Due to padding, the
disassembler may produce a few spurious, but harmless, instructions at the end
of the text segment.
.PP
Because the information to which initialized data refers cannot generally
be inferred from context, the data segment is treated literally. Byte values
(in hexadecimal) are output, and long stretches of null data are represented by
appropriate \fI.zerow\fR pseudo-ops. 
Disassembly of the bss segment, on the other
hand, is quite straightforward, because uninitialized data is all zero by 
definition. 
No data is output in the bss segment, but symbolic labels are output
as appropriate.
.PP
The output of operands in symbolic form is complicated somewhat by the
existence of assembler symbolic constants and segment override opcodes. Thus,
the program's symbol lookup routine attempts to apply a certain amount of
intelligence when it is asked to find a symbol. If it cannot match on a symbol
of the preferred type, it may output a symbol of some other type, depending on
preassigned (and somewhat arbitrary) rankings within each type. Finally, if
all else fails, it will output a string containing the address sought as a hex
constant. For user convenience, the targets of branches are also output, in
comments, as hexadecimal constants.
.SS "Error Messages"
.PP
Various error messages may be generated as a result of problems encountered
during the disassembly.
They are listed below
.HS.
.in +3.20i
.ta +2.75i +0.2i
.ti -2.95i
Cannot access input file	\(en	Input file cannot be opened or read
.ti -2.95i
Cannot open output file	\(en	Output file cannot be created
.ti -2.95i
Input file not in object format	\(en	Bad magic number
.ti -2.95i
Not an 8086/8088 object file	\(en	CPU ID of the file header is incorrect
.ti -2.95i
Reloc table overflow	\(en	Relocation table exceeds 1500 entries
.ti -2.95i
Symbol table overflow	\(en	Symbol table exceeds 1500 entries
.ti -2.95i
Lseek error	\(en	Input file corrupted (should never happen)
.ti -2.95i
Warning: no symbols	\(en	Symbol table is missing (use ast)
.ti -2.95i
Cannot reopen input file	\(en	Input file was removed during execution
.in -3.20i
.SS "Author"
.PP
\fIDis88\fR  was written and
copyrighted by G. M. Harding and is included here by permission. It may be
freely redistributed provided that complete source code, with all copyright
notices, accompanies any redistribution. This provision also applies to any
modifications you may make. You are urged to comment such changes, giving,
as a minimum, your name and complete address.