<refentry lang="en">

<refentryinfo>

    <title>ndisasm(1)</title>

</refentryinfo>

<refmeta>

<refentrytitle>ndisasm</refentrytitle>

<manvolnum>1</manvolnum>

<refmiscinfo class="source">NASM</refmiscinfo>

<refmiscinfo class="manual">The Netwide Assembler Project</refmiscinfo>

</refmeta>

<refnamediv>

    <refname>ndisasm</refname>

    <refpurpose>the Netwide Disassembler, an 80x86 binary file disassembler</refpurpose>

</refnamediv>

<refsynopsisdiv id="_synopsis">

<simpara><emphasis role="strong">ndisasm</emphasis> [ <emphasis role="strong">-o</emphasis> origin ] [ <emphasis role="strong">-s</emphasis> sync-point […]] [ <emphasis role="strong">-a</emphasis> | <emphasis role="strong">-i</emphasis> ]

        [ <emphasis role="strong">-b</emphasis> bits ] [ <emphasis role="strong">-u</emphasis> ] [ <emphasis role="strong">-e</emphasis> hdrlen ] [ <emphasis role="strong">-p</emphasis> vendor ]

        [ <emphasis role="strong">-k</emphasis> offset,length […]] infile</simpara>

</refsynopsisdiv>

<refsect1 id="_description">

<title>DESCRIPTION</title>

<simpara>The <emphasis role="strong">ndisasm</emphasis> command generates a disassembly listing of the binary file

infile and directs it to stdout.</simpara>

</refsect1>

<refsect1 id="_options">

<title>OPTIONS</title>

<variablelist>

<varlistentry>

<term>

<emphasis role="strong">-h</emphasis>

</term>

<listitem>

<simpara>

        Causes <emphasis role="strong">ndisasm</emphasis> to exit immediately, after giving a summary

        of its invocation options.

</simpara>

</listitem>

</varlistentry>

<varlistentry>

<term>

<emphasis role="strong">-r</emphasis>|<emphasis role="strong">-v</emphasis>

</term>

<listitem>

<simpara>

        Causes <emphasis role="strong">ndisasm</emphasis> to exit immediately, after displaying its

        version number.

</simpara>

</listitem>

</varlistentry>

<varlistentry>

<term>

<emphasis role="strong">-o</emphasis> <emphasis>origin</emphasis>

</term>

<listitem>

<simpara>

        Specifies the notional load address for the file. This

        option causes <emphasis role="strong">ndisasm</emphasis> to get the addresses it lists

        down the left hand margin, and the target addresses

        of PC-relative jumps and calls, right.

</simpara>

</listitem>

</varlistentry>

<varlistentry>

<term>

<emphasis role="strong">-s</emphasis> <emphasis>sync-point</emphasis>

</term>

<listitem>

<simpara>

        Manually specifies a synchronisation address, such that

        <emphasis role="strong">ndisasm</emphasis> 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.

</simpara>

</listitem>

</varlistentry>

<varlistentry>

<term>

<emphasis role="strong">-e</emphasis> <emphasis>hdrlen</emphasis>

</term>

<listitem>

<simpara>

        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 <emphasis>disassembled</emphasis> instruction will be shown starting

        at the given load address.

</simpara>

</listitem>

</varlistentry>

<varlistentry>

<term>

<emphasis role="strong">-k</emphasis> <emphasis>offset,length</emphasis>

</term>

<listitem>

<simpara>

        Specifies that <emphasis>length</emphasis> bytes, starting from disassembly

        offset <emphasis>offset</emphasis>, should be skipped over without generating

        any output. The skipped bytes still count towards the

        calculation of the disassembly offset.

</simpara>

</listitem>

</varlistentry>

<varlistentry>

<term>

<emphasis role="strong">-a</emphasis>|<emphasis role="strong">-i</emphasis>

</term>

<listitem>

<simpara>

        Enables automatic (or intelligent) sync mode, in which

        <emphasis role="strong">ndisasm</emphasis> will attempt to guess where synchronisation should

        be performed, by means of examining the target addresses

        of the relative jumps and calls it disassembles.

</simpara>

</listitem>

</varlistentry>

<varlistentry>

<term>

<emphasis role="strong">-b</emphasis> <emphasis>bits</emphasis>

</term>

<listitem>

<simpara>

        Specifies 16-, 32- or 64-bit mode. The default is 16-bit

        mode.

</simpara>

</listitem>

</varlistentry>

<varlistentry>

<term>

<emphasis role="strong">-u</emphasis>

</term>

<listitem>

<simpara>

        Specifies 32-bit mode, more compactly than using ‘-b 32’.

</simpara>

</listitem>

</varlistentry>

<varlistentry>

<term>

<emphasis role="strong">-p</emphasis> <emphasis>vendor</emphasis>

</term>

<listitem>

<simpara>

        Prefers instructions as defined by <emphasis>vendor</emphasis> in case of

        a conflict. Known <emphasis>vendor</emphasis> names include <emphasis role="strong">intel</emphasis>, <emphasis role="strong">amd</emphasis>,

        <emphasis role="strong">cyrix</emphasis>, and <emphasis role="strong">idt</emphasis>. The default is <emphasis role="strong">intel</emphasis>.

</simpara>

</listitem>

</varlistentry>

</variablelist>

</refsect1>

<refsect1 id="_restrictions">

<title>RESTRICTIONS</title>

<simpara><emphasis role="strong">ndisasm</emphasis> 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 <emphasis role="strong">objdump</emphasis>(1).</simpara>

<simpara>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 <emphasis>before</emphasis>

<emphasis role="strong">ndisasm</emphasis> 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.</simpara>

</refsect1>

<refsect1 id="_see_also">

<title>SEE ALSO</title>

<simpara><emphasis role="strong">objdump</emphasis>(1)</simpara>

</refsect1>

</refentry>