ndisasm - the Netwide Disassembler, an 80x86 binary file disassembler
ndisasm [ -o origin ] [ -s sync-point [...]] [ -a | -i ] [ -b bits ] [
-u ] [ -e hdrlen ] [ -k offset,length [...]] infile
The ndisasm command generates a disassembly listing of the binary file
infile and directs it to stdout.
-h Causes ndisasm to exit immediately, after giving a summary of
its invocation options.
-r Causes ndisasm to exit immediately, after displaying its version
Specifies the notional load address for the file. This option
causes ndisasm to get the addresses it lists down the left hand
margin, and the target addresses of PC-relative jumps and calls,
Manually specifies a synchronisation address, such that ndisasm
will not output any machine instruction which encompasses bytes
on both sides of the address. Hence the instruction which starts
at that address will be correctly disassembled.
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 disassem-
bled instruction will be shown starting at the given load
Specifies that length bytes, starting from disassembly offset
offset, should be skipped over without generating any output.
The skipped bytes still count towards the calculation of the
-a or -i
Enables automatic (or intelligent) sync mode, in which 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.
Specifies either 16-bit or 32-bit mode. The default is 16-bit
-u Specifies 32-bit mode, more compactly than using ‘-b 32’.
Prefers instructions as defined by vendor in case of a conflict.
Known vendor names include intel, amd, cyrix, and idt. The
default is intel.
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 objdump(1).
Auto-sync mode won’t necessarily cure all your synchronisation prob-
lems: a sync marker can only be placed automatically if a jump or call
instruction is found to refer to it before ndisasm actually disassem-
bles 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.
ndisasm can only keep track of 8192 sync markers internally at once:
this is to do with portability, since DOS machines don’t take kindly to
more than 64K being allocated at a time.
The Netwide Assembler Project NDISASM(1)
Man(1) output converted with