nasm/ndisasm.1

.\"
.\" This file is part of NASM and is released under the NASM License.
.\"
.TH NDISASM 1 "The Netwide Assembler Project"
.SH NAME
ndisasm \- the Netwide Disassembler, an 80x86 binary file disassembler
.SH SYNOPSIS
.B ndisasm
[
.B \-o
origin
] [
.B \-s
sync-point [...]]
[
.B \-a
|
.B \-i
] [
.B \-b
bits
] [
.B -u
] [
.B \-e
hdrlen
] [
.B \-k
offset,length [...]]
infile
.br
.B ndisasm \-h
.br
.B ndisasm \-r
.SH DESCRIPTION
The
.B ndisasm
command generates a disassembly listing of the binary file
.I infile
and directs it to stdout.
.SS OPTIONS
.TP
.B \-h
Causes
.B ndisasm
to exit immediately, after giving a summary of its invocation
options.
.TP
.BI \-r
Causes
.B ndisasm
to exit immediately, after displaying its version number.
.TP
.BI \-o " origin"
Specifies the notional load address for the file. This option causes
.B ndisasm
to get the addresses it lists down the left hand margin, and the
target addresses of PC-relative jumps and calls, right.
.TP
.BI \-s " sync-point"
Manually specifies a synchronisation address, such that
.B ndisasm
will not output any machine instruction which encompasses bytes on
both sides of the address. Hence the instruction which
.I starts
at that address will be correctly disassembled.
.TP
.BI \-e " hdrlen"
Specifies a number of bytes to discard from the beginning of the
file before starting disassembly. This does not count towards the
calculation of the disassembly offset: the first
.I disassembled
instruction will be shown starting at the given load address.
.TP
.BI \-k " offset,length"
Specifies that
.I length
bytes, starting from disassembly offset
.IR offset ,
should be skipped over without generating any output. The skipped
bytes still count towards the calculation of the disassembly offset.
.TP
.BR \-a " or " \-i
Enables automatic (or intelligent) sync mode, in which
.B ndisasm
will attempt to guess where synchronisation should be performed, by
means of examining the target addresses of the relative jumps and
calls it disassembles.
.TP
.BI \-b " bits"
Specifies 16-, 32- or 64-bit mode. The default is 16-bit mode.
.TP
.B \-u
Specifies 32-bit mode, more compactly than using `-b 32'.
.TP
.BI \-p " vendor"
Prefers instructions as defined by
.I vendor
in case of a conflict.  Known
.I vendor
names include
.BR intel ,
.BR amd ,
.BR cyrix ,
and
.BR idt .
The default is
.BR intel .
.PP
.RE
.SH RESTRICTIONS
.B ndisasm
only disassembles binary files: it has no understanding of the
header information present in object or executable files. If you
want to disassemble an object file, you should probably be using
.BR objdump "(" 1 ")."
.PP
Auto-sync mode won't necessarily cure all your synchronisation
problems: a sync marker can only be placed automatically if a jump
or call instruction is found to refer to it
.I before
.B ndisasm
actually disassembles that part of the code. Also, if spurious jumps
or calls result from disassembling non-machine-code data, sync
markers may get placed in strange places. Feel free to turn
auto-sync off and go back to doing it manually if necessary.
.PP
.SH SEE ALSO
.BR objdump "(" 1 ")."