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LDP/howto/linuxdoc/Assembly-HOWTO.sgml
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@ -1,26 +1,11 @@
<!doctype linuxdoc system>
<!-- $Id$
<!-- $Id$ -->
NOTE TO PUBLISHERS:
(1) This document uses iso-8859-1 latin encoding,
so you must give -l flag to sgmltools 0.99.x,
or -c latin to sgmltools 1.x...
(2) some of the material here can be skipped for a paper print,
as much as it is redundant with other material
(e.g. how to use the HOWTO, plea for contributions, etc,
which should be replaced by a generic explanation at the head
of any good HOWTO compendium),
or do not worth the paper to print it ("History", "Credits"),
considering that HOWTO compendiums must squeeze lot of
stuff on a limited place.
(3) I recommend you not to edit/remove/strip
the rest of the document (after the introduction)
unless you explicitly state you did it on the same page
as the HOWTO appears, and/or you agree with me before.
<!--
This is (probably) the last release of HOWTO with linuxdoc dtd.
Following releases will be in docbook dtd.
Translators (if any), get ready.
-->
<article>
@ -29,9 +14,9 @@
<author>
<url url="mailto:konst@linuxassembly.org" name="Konstantin Boldyshev"> and
<url url="mailto:fare@tunes.org" name="François-René Rideau">
<url url="mailto:fare@tunes.org" name="Francois-Rene Rideau">
<date>v0.5i, May 4, 2000
<date>v0.5j, June 14, 2000
<abstract>
This is the Linux Assembly HOWTO.
@ -39,26 +24,29 @@ This is the Linux Assembly HOWTO.
This document describes how to program in assembly language
using FREE programming tools,
focusing on development for or from the Linux Operating System,
mostly on IA32 (i386) platform.
mostly on IA-32 (i386) platform.
Included material may or may not be applicable
to other hardware and/or software platforms.
Contributions about them will be gladly accepted.
Contributions about them are gladly accepted.
<bf/Keywords/:
<tt/assembly, assembler, asm, inline asm, macroprocessor, preprocessor,
32-bit, IA32, i386, x86, gas, as86, nasm, OS, kernel, system, libc,
32-bit, IA-32, i386, x86, gas, as86, nasm, OS, kernel, system, libc,
system call, interrupt, small, fast, embedded, hardware, port/
</abstract>
<toc>
<sect>INTRODUCTION
<p>
You can skip this section if you are familiar with HOWTOs,
or just hate to read all this assembly-nonrelated crap.
<sect1>Legal Blurb
<p>Copyright &copy; 1999-2000 Konstantin Boldyshev.
<p>Copyright &copy; 1996-1999 François-René Rideau.
<p>Copyright &copy; 1996-1999 Francois-Rene Rideau.
This document may be distributed only subject to the terms and conditions set
forth in the <url url="http://linuxdoc.org/COPYRIGHT.html" name="LDP License">.
@ -80,15 +68,26 @@ and partial documents, must meet the following requirements:
the original author's (or authors') permission
</itemize>
The most recent official version of this document is available from
<url url="http://linuxassembly.org" name="Linux Assembly"> and
<url url="http://linuxdoc.org" name="LDP"> sites.
If you are reading a few-months-old copy,
consider checking urls above for a new version.
<sect1>Foreword
<p>
This document aims answering questions of those
who program or want to program 32-bit x86 assembly using
<em><url url="http://www.gnu.org/philosophy/" name="free software"></em>,
particularly under the Linux operating system.
It also points to other documents about
At many places, Universal Resource Locators (URL) are given for some
software or documentation repository.
This document also points to other documents about
non-free, non-x86, or non-32-bit assemblers,
although this is not its primary goal.
Also note that there are FAQs and docs about programming
on your favorite platform (whatever it is), which you should consult
for platform-specific issues, not related directly to assembly programming.
Because the main interest of assembly programming is to build
the guts of operating systems, interpreters, compilers, and games,
@ -96,7 +95,19 @@ where C compiler fails to provide the needed expressiveness
(performance is more and more seldom as issue),
we are focusing on development of such kind of software.
<sect1>Important Note
If you don't know what <em/free/ software is,
please do read <em/carefully/ the GNU General Public License,
which is used in a lot of free software,
and is the model for most of their licenses.
It generally comes in a file named <tt/COPYING/ (or <tt/COPYING.LIB/).
Literature from the <url url="http://www.fsf.org" name="FSF">
(free software foundation) might help you, too.
Particularly, the interesting feature of free software
is that it comes with sources that you can consult and correct,
or sometimes even borrow from.
Read your particular license carefully and do comply to it.
<sect1>Contributions
<p>
This is an interactively evolving document: you are especially invited
to ask questions,
@ -110,58 +121,39 @@ To contribute, please contact the Assembly-HOWTO maintainer.
At the time of this writing, it is
<url url="mailto:konst@linuxassembly.org" name="Konstantin Boldyshev">
and no more
<url url="mailto:fare@tunes.org" name="François-René Rideau">.
I (Faré) had been looking for some time for a serious hacker
<url url="mailto:fare@tunes.org" name="Francois-Rene Rideau">.
I (Fare) had been looking for some time for a serious hacker
to replace me as maintainer of this document,
and am pleased to announce Konstantin as my worthy successor.
<sect2>How to use this document
<sect1>Credits
<p>
This document contains answers to some frequently asked questions.
At many places, Universal Resource Locators (URL) are given for some
software or documentation repository.
Please see that the most useful repositories are mirrored,
and that by accessing a nearer mirror site,
you relieve the whole Internet from unneeded network traffic,
while saving your own precious time.
Particularly, there are large repositories all over the world,
that mirror other popular repositories.
You should learn and note what are those places near you (networkwise).
Sometimes, the list of mirrors is listed in a file,
or in a login message. Please heed the advice.
Else, you should ask archie about the software you're looking for...
The most recent official version of this document is available from
<url url="http://linuxassembly.org" name="Linux Assembly"> and
<url url="http://linuxdoc.org" name="LDP"> sites.
If you are reading a few-months-old copy,
please check the urls above for a new version.
<sect2>Other related documents
<p>
I would like to thank following persons, by order of appearance:
<itemize>
<item>If you don't know what <em/free/ software is,
please do read <em/carefully/ the GNU General Public License,
which is used in a lot of free software,
and is a model for most of their licenses.
It generally comes in a file named <tt/COPYING/,
with a library version in a file named <tt/COPYING.LIB/.
Literature from the <url url="http://www.fsf.org" name="FSF">
(free software foundation) might help you, too.
<item>Particularly, the interesting feature of free software
is that it comes with sources that you can consult and correct,
or sometimes even borrow from.
Read your particular license carefully, and do comply to it.
<item>There are FAQs and docs about programming on your favorite platform,
whatever it is, which you should consult for platform-specific issues,
not related directly to assembly programming.
<item>Refer to <ref id="res" name="RESOURCES"> section of this HOWTO
for pointers to related documents and projects.
<item><url url="mailto:buried.alive@in.mail" name="Linus Torvalds">
for Linux
<item><url url="mailto:bde@zeta.org.au" name="Bruce Evans">
for bcc from which as86 is extracted
<item><url url="mailto:anakin@pobox.com" name="Simon Tatham"> and
<url url="mailto:jules@earthcorp.com" name="Julian Hall">
for NASM
<item><url url="mailto:gregh@metalab.unc.edu" name="Greg Hankins">
and now
<url url="mailto:linux-howto@metalab.unc.edu" name="Tim Bynum">
for maintaining HOWTOs
<item><url url="mailto:raymoon@moonware.dgsys.com" name="Raymond Moon">
for his FAQ
<item><url url="mailto:dumas@linux.eu.org" name="Eric Dumas">
for his translation of the mini-HOWTO into French
(sad thing for the original author to be French and write in English)
<item><url url="mailto:paul@geeky1.ebtech.net" name="Paul Anderson">
and <url url="mailto:rahim@megsinet.net" name="Rahim Azizarab">
for helping me, if not for taking over the HOWTO.
<item><url url="mailto:pcg@goof.com" name="Marc Lehman">
for his insight on GCC invocation.
<item><url url="mailto:ams@wiw.org" name="Abhijit Menon-Sen">
for helping me figure out the argument passing convention
<item>All the people who have contributed ideas, answers, remarks, and moral support.
</itemize>
<sect1>History
@ -169,6 +161,11 @@ for pointers to related documents and projects.
Each version includes a few fixes and minor corrections,
that need not to be repeatedly mentioned every time.
<descrip>
<tag/Version 0.5j 14 Jun 2000/
Complete rearrangement of INTRODUCTION and RESOURCES;
FAQ added to RESOURCES, misc cleanups and additions
(and more to come)
<tag/Version 0.5i 04 May 2000/
Added HLA, TALC;
rearrangements in RESOURCES, QUICK START, ASSEMBLERS;
@ -212,7 +209,7 @@ that need not to be repeatedly mentioned every time.
<tag/Version 0.4q 22 June 1999/
process argument passing (argc,argv,environ) in assembly.
This is yet another
"last release by Faré before new maintainer takes over".
"last release by Fare before new maintainer takes over".
Nobody knows who might be the new maintainer.
<tag/Version 0.4p 6 June 1999/
@ -288,42 +285,13 @@ that need not to be repeatedly mentioned every time.
<tag/Version 0.2 04 May 1996/ *
<tag/Version 0.1 23 Apr 1996/
Francois-Rene "Faré" Rideau &lt;fare@tunes.org&gt;
Francois-Rene "Fare" Rideau &lt;fare@tunes.org&gt;
creates and publishes the first mini-HOWTO,
because "I'm sick of answering ever the same questions
on comp.lang.asm.x86"
</descrip>
<sect1>Credits
<p>
I would like to thank following persons, by order of appearance:
<itemize>
<item><url url="mailto:buried.alive@in.mail" name="Linus Torvalds">
for Linux
<item><url url="mailto:bde@zeta.org.au" name="Bruce Evans">
for bcc from which as86 is extracted
<item><url url="mailto:anakin@pobox.com" name="Simon Tatham"> and
<url url="mailto:jules@earthcorp.com" name="Julian Hall">
for NASM
<item><url url="mailto:gregh@metalab.unc.edu" name="Greg Hankins">
and now
<url url="mailto:linux-howto@metalab.unc.edu" name="Tim Bynum">
for maintaining HOWTOs
<item><url url="mailto:raymoon@moonware.dgsys.com" name="Raymond Moon">
for his FAQ
<item><url url="mailto:dumas@linux.eu.org" name="Eric Dumas">
for his translation of the mini-HOWTO into French
(sad thing for the original author to be French and write in English)
<item><url url="mailto:paul@geeky1.ebtech.net" name="Paul Anderson">
and <url url="mailto:rahim@megsinet.net" name="Rahim Azizarab">
for helping me, if not for taking over the HOWTO.
<item><url url="mailto:pcg@goof.com" name="Marc Lehman">
for his insight on GCC invocation.
<item><url url="mailto:ams@wiw.org" name="Abhijit Menon-Sen">
for helping me figure out the argument passing convention
<item>All the people who have contributed ideas, remarks, and moral support.
</itemize>
@ -358,11 +326,8 @@ Assembly can express very low-level things:
<item>you can produce reasonably fast code for tight loops
to cope with a bad non-optimizing compiler
(but then, there are free optimizing compilers available!)
<item>you can produce code where
(but only on CPUs with known instruction timings,
which generally excludes all current ....
<item>you can produce hand-optimized code
that's perfectly tuned for your particular hardware setup,
perfectly tuned for your particular hardware setup,
though not to anyone else's.
<item>you can write some code for your new language's
optimizing compiler
@ -378,8 +343,8 @@ Assembly is a very low-level language
This means
<itemize>
<item>it's long and tedious to write initially,
<item>it's very bug-prone,
<item>your bugs will be very difficult to chase,
<item>it's quite bug-prone,
<item>your bugs can be very difficult to chase,
<item>it's very difficult to understand and modify,
i.e. to maintain.
<item>the result is very non-portable to other architectures,
@ -607,47 +572,45 @@ The original GCC site is the GNU FTP site
together with all released application software from the GNU project.
Linux-configured and precompiled versions can be found in
<url url="ftp://metalab.unc.edu/pub/Linux/GCC/">
There exists a lot of FTP mirrors of both sites.
There are a lot of FTP mirrors of both sites,
everywhere around the world, as well as CD-ROM copies.
GCC development has split into two branches some time ago (GCC 2.8 and EGCS),
but they merged back, and current GCC webpage is <url url="http://gcc.cygnus.com">.
but they merged back, and current GCC webpage is <url url="http://gcc.gnu.org">.
Sources adapted to your favorite OS, and binaries precompiled for it,
Sources adapted to your favorite OS and precompiled binaries
should be found at your usual FTP sites.
For most popular DOS port of GCC is named DJGPP,
and can be found in directories of such name in FTP sites. See:
<url url="http://www.delorie.com/djgpp/">
and can be found in directories of such name in FTP sites.
See <url url="http://www.delorie.com/djgpp/">.
There are two Win32 GCC ports:
<url url="http://sourceware.cygnus.com/cygwin/" name="cygwin"> and
<url url="http://www.mingw.org" name="mingw">
There is also a port of GCC to OS/2 named EMX,
that also works under DOS,
and includes lots of unix-emulation library routines.
See around the following site:
<url url="ftp://ftp-os2.cdrom.com/pub/os2/emx09c/">.
<!-- Other URLs listed in previous versions of this HOWTO
seem to be as dead as OS/2. -->
<!-- broken url url="http://www.leo.org/pub/comp/os/os2/gnu/emx+gcc/"-->
<!-- broken url url="http://warp.eecs.berkeley.edu/os2/software/shareware/emx.html"-->
<sect2>Where to find docs for GCC Inline Asm
<p>
The documentation of GCC includes documentation files in texinfo format.
You can compile them with tex and print then result,
The documentation of GCC includes documentation files in TeXinfo format.
You can compile them with TeX and print then result,
or convert them to .info, and browse them with emacs,
or convert them to .html, or nearly whatever you like.
or convert them to .html, or nearly whatever you like;
convert (with the right tools) to whatever you like,
or just read as is.
The .info files are generally found on any good installation for GCC.
The right section to look for is:
<tt/C Extensions::Extended Asm::/
The right section to look for is <tt/C Extensions::Extended Asm::/
Section
<tt/Invoking GCC::Submodel Options::i386 Options::/
might help too.
Section <tt/Invoking GCC::Submodel Options::i386 Options::/ might help too.
Particularly, it gives the i386 specific constraint names for registers:
<tt/abcdSDB/ correspond to
<tt/&percnt;eax/,
@ -733,7 +696,7 @@ Note that modern GCC has <tt/-mpentium/ and such flags
(and <url url="http://goof.com/pcg/" name="PGCC"> has even more),
whereas GCC 2.7.x and older versions do not.
A good choice of CPU-specific flags should be in the Linux kernel.
Check the texinfo documentation of your current GCC installation for more.
Check the TeXinfo documentation of your current GCC installation for more.
<tt/-m386/ will help optimize for size,
hence also for speed on computers whose memory is tight and/or loaded,
@ -751,7 +714,7 @@ whereas other files will be optimized for size.
To optimize even more, option <tt/-mregparm=2/
and/or corresponding function attribute might help,
but might pose lots of problems when linking to foreign code,
<em/including the libc/.
<em/including libc/.
There are ways to correctly declare foreign functions
so the right call sequences be generated,
or you might want to recompile the foreign libraries
@ -908,19 +871,23 @@ The Netwide Assembler project provides cool i386 assembler,
written in C, that should be modular enough
to eventually support all known syntaxes and object formats.
<sect2>Where to find NASM
<sect2>Where to find NASM<label id="findnasm">
<p>
<url url="http://www.cryogen.com/Nasm/">
Binary release on your usual metalab mirror in
<tt>devel/lang/asm/</tt>
Binary release on your usual metalab mirror in <tt>devel/lang/asm/</tt>.
Should also be available as .rpm or .deb in your usual RedHat/Debian
distributions' contrib.
At the time of writing current version of NASM is 0.98.
Note: there's also an extented NASM version available at
<url url="ftp://ftp.linuxgames.com/crystal/nasm/">
know as 0.98e. It introduces several serious bugfixes and improvements,
so you may want to use it instead of "official" version.
<sect2>What it does
<p>
At the time this HOWTO is written, current version of NASM is 0.98.
The syntax is Intel-style.
Fairly good macroprocessing support is integrated.
@ -943,8 +910,8 @@ though of course, it doesn't support three bazillion different architectures.
If you like Intel-style syntax, as opposed to GAS syntax,
then it should be the assembler of choice...
Note: There's a <ref id="res-related" name="converter between GAS AT&amp;T and Intel assembler syntax">,
which does conversion in both directions.
Note: There are <ref id="res" name="converters between GAS AT&amp;T and Intel assembler syntax">,
which perform conversion in both directions.
<sect1>AS86
<p>
@ -1101,48 +1068,48 @@ improvement over many of its successors. -John"
<sect2>HLA
<p>
<url url="http://webster.cs.ucr.edu " name="HLA">
<url url="http://webster.cs.ucr.edu" name="HLA">
is a <bf/H/igh <bf/L/evel <bf/A/ssembly language.
It uses a high level language like syntax
(similar to Pascal, C/C++, and other HLLs) for variable declarations,
procedure declarations, and procedure calls. It uses a modified
assembly language syntax for the standard machine instructions.
It also provides several high level language style control structures
(if, while, repeat..until, etc.) that help you write much more readable code.
It uses a high level language like syntax
(similar to Pascal, C/C++, and other HLLs) for variable declarations,
procedure declarations, and procedure calls. It uses a modified
assembly language syntax for the standard machine instructions.
It also provides several high level language style control structures
(if, while, repeat..until, etc.) that help you write much more readable code.
HLA is free, but runs only under Win32.
You need MASM and a 32-bit version of MS-link,
HLA is free, but runs only under Win32.
You need MASM and a 32-bit version of MS-link,
because HLA produces MASM code and uses MASM for final
assembling and linking. However it comes with <tt/m2t/ (MASM to TASM)
post-processor program that converts the HLA MASM output to a form
that will compile under TASM. Unfortunately, NASM is not supported.
post-processor program that converts the HLA MASM output to a form
that will compile under TASM. Unfortunately, NASM is not supported.
<sect2>TALC
<p>
<url url="http://www.cs.cornell.edu/talc/ " name="TALC">
<url url="http://www.cs.cornell.edu/talc/" name="TALC">
is another free MASM/Win32 based compiler
(however it supports ELF output, does it?).
TAL stands for <bf/T/yped <bf/A/ssembly <bf/L/anguage.
It extends traditional untyped assembly languages with typing annotations,
memory management primitives, and a sound set of typing rules, to guarantee
the memory safety, control flow safety, and type safety of TAL programs.
Moreover, the typing constructs are expressive enough to encode
most source language programming features including records and structures,
arrays, higher-order and polymorphic functions, exceptions, abstract data types,
It extends traditional untyped assembly languages with typing annotations,
memory management primitives, and a sound set of typing rules, to guarantee
the memory safety, control flow safety,and type safety of TAL programs.
Moreover, the typing constructs are expressive enough to encode
most source language programming features including records and structures,
arrays, higher-order and polymorphic functions, exceptions, abstract data types,
subtyping, and modules.
Just as importantly, TAL is flexible enough to admit many low-level compiler optimizations.
Consequently, TAL is an ideal target platform for type-directed compilers
Just as importantly, TAL is flexible enough to admit many low-level compiler optimizations.
Consequently, TAL is an ideal target platform for type-directed compilers
that want to produce verifiably safe code
for use in secure mobile code applications
for use in secure mobile code applications
or extensible operating system kernels.
<sect2>Non-free and/or Non-32bit x86 assemblers.
<p>
You may find more about them,
together with the basics of x86 assembly programming,
in <ref id="res-general" name="Raymond Moon's FAQ for comp.lang.asm.x86">.
in <ref id="res-general" name="Raymond Moon's x86 assembly FAQ">.
Note that all DOS-based assemblers should work inside the Linux DOS Emulator,
as well as other similar emulators, so that if you already own one,
@ -1395,7 +1362,7 @@ make it unchallenged as for macroprocessing/metaprogramming.
<sect2>Linking to GCC
<p>
That's the preferred way.
This is the preferred way if you are developing mixed C-asm project.
Check GCC docs and examples from Linux kernel <tt/.S/ files
that go through gas (not those that go through as86).
@ -1453,12 +1420,8 @@ More generally, it will do lots of file format conversions.
<sect2>Direct Linux syscalls
<p>
Often you will be told that using libc is the only way,
and direct system calls are bad.
Believe it, <em/unless/ of course
you're specifically writing your own replacement for the libc,
adapted to your specific language or memory requirements or whatever.
But you must know that libc is not sacred, and in <em/most/ cases
and direct system calls are bad. This is true. To some extent.
So, you must know that libc is not sacred, and in <em/most/ cases
libc only does some checks, then calls kernel, and then sets errno.
You can easily do this in your program as well (if you need to),
and your program will be dozen times smaller, and
@ -1482,6 +1445,8 @@ Pros:
<itemize>
<item>smallest possible size; squeezing the last byte out of the system.
<item>highest possible speed; squeezing cycles out of your favorite benchmark.
<item>full control: you can adapt your program/library
to your specific language or memory requirements or whatever
<item>no pollution by libc cruft.
<item>no pollution by C calling conventions
(if you're developing your own language or environment).
@ -1496,14 +1461,14 @@ Cons:
<item>If any other program on your computer uses the libc,
then duplicating the libc code will actually
waste memory, not save it.
<item>Services redundantly implemented in many static binaries
are a waste of memory.
But you can make your libc replacement a shared library.
<item>Size is much better saved by having some kind
of bytecode, wordcode, or structure interpreter
than by writing everything in assembly.
(the interpreter itself could be written either in C or assembly.)
<item>Services redundantly implemented in many static binaries
are a waste of memory.
But you can put your libc replacement in a shared library.
<item>The best way to keep multiple binaries small is
The best way to keep multiple binaries small is
to not have multiple binaries, but instead
to have an interpreter process files with <tt/&num;!/ prefix.
This is how OCaml works when used in wordcode mode
@ -1537,9 +1502,11 @@ Cons:
and can be <em/quite/ boring sometimes.
Note that some people have already reimplemented &quot;light&quot;
replacements for parts of the libc -- check them out!
(Rick Hohensee's <url url="ftp://linux01.gwdg.de/pub/cLIeNUX/interim/libsys.tgz" name="libsys">,
Christian Fowelin's <ref id="res-projects" name="libASM">,
<ref id="res-projects" name="asmutils"> project is working on pure assembly libc)
(Redhat's minilibc,
Rick Hohensee's <url url="ftp://linux01.gwdg.de/pub/cLIeNUX/interim/libsys.tgz" name="libsys">,
Felix von Leitner's <url url="http://www.fefe.de/dietlibc/" name="dietlibc">,
Christian Fowelin's <ref id="res" name="libASM">,
<ref id="res" name="asmutils"> project is working on pure assembly libc)
<item>Static libraries prevent your benefitting from libc upgrades
as well as from libc add-ons such as the <tt/zlibc/ package,
@ -1579,7 +1546,7 @@ then here is some advice.
(And if you think you can do better,
then send feedback to the authors!)
<item>As an example of pure assembly code that does everything you want,
examine <ref id="res-projects" name="Linux Assembly Projects">.
examine <ref id="res" name="Linux Assembly resources">.
</itemize>
Basically, you issue an <tt/int 0x80/,
@ -1714,10 +1681,10 @@ This HOWTO is not about Windows programming,
you can find lots of documents about it everywhere..
The thing you should know is that
<url url="http://www.cygnus.com" name="Cygnus Solutions">
developed the cygwin32.dll library, for GNU programs to run on Win32 platform.
Thus, you can use GCC, GAS, all the GNU tools, and many other Unix applications.
Take a look on their webpage.
developed the
<url url="http://sourceware.cygnus.com/cygwin/" name="cygwin32.dll library">,
for GNU programs to run on Win32 platform; thus, you can use GCC, GAS,
all the GNU tools, and many other Unix applications.
<sect1>Your own OS
<p>
@ -1765,7 +1732,7 @@ it will communicate directly with kernel.
I will show the same sample program in two assemblers, <tt/nasm/ and <tt/gas/,
thus showing Intel and AT&amp;T syntax.
You may also want to read <ref id="res-tutorials"
You may also want to read <url url="http://linuxassembly.org/intro.html"
name="Introduction to UNIX assembly programming"> tutorial,
it contains sample code for other UNIX-like OSes.
@ -1775,7 +1742,7 @@ First of all you need assembler (compiler): <tt/nasm/ or <tt/gas/.
Second, you need linker: <tt/ld/, assembler produces only object code.
Almost all distributions include <tt/gas/ and <tt/ld/, in binutils package.
As for <tt/nasm/, you may have to download and install binary packages
for Linux and docs from the <ref id="res-related" name="nasm webpage">;
for Linux and docs from the <ref id="findnasm" name="nasm webpage">;
however, several distributions (Stampede, Debian, SuSe)
already include it, check first.
<p>
@ -1858,8 +1825,8 @@ _start:
<sect1>Producing object code
<p>
First step of building binary is producing object file from source, by invoking assembler;
we must issue the following:
First step of building binary is producing object file from source
by invoking assembler; we must issue the following:
<p>
For <tt/nasm/ example:
@ -1874,81 +1841,46 @@ This will produce <tt/hello.o/ object file.
<sect1>Producing executable
<p>
Second step is producing executable file itself from object file, by invoking linker:
Second step is producing executable file itself from object file
by invoking linker:
<p>
<tt/&dollar; ld -s -o hello hello.o/
This will finally build <tt/hello/ ELF binary.
This will finally build <tt/hello/ executable.
<p>
Hey, try to run it... Works? That's it. Pretty simple.
If you get interested and want to proceed further,
you may want to look through
<ref id="res-projects" name="Linux assembly projects">,
they contain PLENTY of source code and examples.
<sect>RESOURCES<label id="res">
<p>
You main resource for Linux/UNIX assembly programming material
is <url url="http://linuxassembly.org" name="Linux Assembly"> :).
Here are some of resources listed there. This list is cut-down and
may be outdated, so please visit the site for detailed up-to-date list.
is <bf><url url="http://linuxassembly.org/resources.html"
name="Linux Assembly resources page"></bf>
Do visit it, and get plenty of pointers to assembly projects,
tools, tutorials, documentation, guides, etc,
concerning different UNIX operating systems and CPUs.
Because it evolves quickly, I will no longer duplicate it in this HOWTO.
<sect1>Software projects<label id="res-projects">
<p>
If you are new to assembly in general, here are few starting pointers:
<label id="res-general">
<itemize>
<item><url url="http://linuxassembly.org/asmutils.html"
name="asmutils"> (miscellaneus utilities, assembly libc)
<item><url url="http://www.fowelin.de/christian/computer.linux.assembly.libASM.html"
name="libASM"> (assembly library, lots of various routines)
<item><url url="http://sax.sax.de/~adlibit/"
name="e3"> (cool WordStar-like text editor)
<item><url url="http://mars.wiwi.uni-halle.de/ec64/"
name="ec64"> (Commodore C64 emulator)
<item><url url="http://www.muppetlabs.com/~breadbox/software/elfkickers.html"
name="ELF kickers & tiny Linux executables">
<item><url url="ftp://www.netstat.ne.jp/pub/Linux/Linux-Alpha-JP/BLAS/"
name="Alpha Linux BLAS"> (basic linear algebra subroutines)
<item><url url="http://users.ev1.net/~redelm/"
name="cpuburn"> (CPU loading utililties)
<item><url url="http://www.lionking.org/~cubbi/serious/asmix.html"
name="ASMIX"> (several commandline unix utilities)
<item><url url="ftp://ftp.forth.org/pub/Forth/Compilers/native/unix/Linux/linux-eforth-1.0e.tar.gz"
name="eforth 1.0e">
<item><url url="http://sunsite.unc.edu/pub/Linux/system/misc/"
name="smallutils"> (few utils for i386 and Sparc)
<item><url url="http://webster.cs.ucr.edu/Page_asm/ArtOfAsm.html"
name="The Art Of Assembly">
<item><url url="http://www2.dgsys.com/&tilde;raymoon/faq/"
name="x86 assembly FAQ">
<item><url url="ftp://ftp.luth.se/pub/msdos/"
name="ftp.luth.se"> mirrors the hornet and x2ftp
former archives of msdos assembly coding stuff
<item><url url="http://www.koth.org" name="CoreWars">,
a fun way to learn assembly in general
<item>Usenet:
<url url="news://comp.lang.asm.x86" name="comp.lang.asm.x86">;
<url url="news://alt.lang.asm" name="alt.lang.asm">
</itemize>
Note that several projects are not Linux-specific,
and run on FreeBSD and other OSes too.
There are quite a lot of mixed C-assembly projects, like
<url url="http://www.kernel.org/" name="Linux kernel">,
<url url="http://www.swox.com/gmp/" name="GNU MP Library">,
<url url="http://www.gnu.org/glibc/" name="GNU libc">,
<url url="http://www.tutok.sk/fastgl/" name="OpenGUI">,
<url url="http://www.freeamp.org/" name="FreeAmp">,
just to name few.
Some of them use <tt/gas/ (sometimes with <tt/m4/), the other use <tt/nasm/.
You may want to examine their source code as well for examples
of assembly programming on different hardware platforms.
<sect1>Tutorials<label id="res-tutorials">
<p>
<itemize>
<item><url url="http://linuxassembly.org/intro.html"
name="Introduction to UNIX Assembly Programming">
<item><url url="http://www.cs.pdx.edu/~bjorn/CS200/linux_tutorial/"
name="Linux assembly tutorial"> (GAS and GDB related)
<item><url url="http://www.muppetlabs.com/~breadbox/software/tiny/teensy.html"
name="A Whirlwind Tutorial on Creating Really Teensy ELF Executables for Linux">
<item><url url="http://bewoner.dma.be/JanW/"
name="Jan's Linux & Assembler HomePage"> (mostly about assembly programming with libc)
</itemize>
<sect1>Mailing list<label id="res-list">
<p>
@ -1966,75 +1898,114 @@ To subscribe send a blank message to <url url="mailto:linux-assembly@egroups.com
List archives are available at <url url="http://www.egroups.com/list/linux-assembly/">.
<sect1>Books<label id="res-books">
<sect1>Frequently asked questions (with asnwers)<label id="faq">
<p>
Unfortunately there are no ready books I can recommend on the topic.
However I'm in the progress of writing a book "Linux Assembly Programming",
which /hopefully/ will be published somewhere in 2000-2001.
Here are frequently asked questions. Answers are taken
from the <ref id="res-list" name="linux-assembly mailing list">.
<sect1>CPU manuals and assembly programming guides<label id="res-cpu">
<sect2>How do I do graphics programming in Linux?
<p>
An answer from <url url="mailto:paulf@icom.co.za" name="Paul Furber">:
<itemize>
<item>IA32 (x86):
<url url="http://sandpile.org" name="sandpile.org">,
<url url="http://developer.intel.com" name="Intel">,
<url url="http://www.amd.com/support/techdocdir.html" name="AMD">,
<url url="http://www.cyrix.com/products/cyrindex.htm" name="Cyrix">,
<url url="http://www.xs4all.nl/~feldmann/86bugs.htm" name="x86 bugs">
<item>Alpha:
<url url="http://www.digital.com/semiconductor/alpha/papers/"
name="Digital Alpha papers">,
<url url="http://ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html"
name="Digital Documentation Library">,
<url url="http://www.unix.digital.com/faqs/publications/base_doc/DOCUMENTATION/V40D_PDF/"
name="more manuals">
<item>SPARC:
<url url="http://www.sparc.com/standards.html"
name="SPARC International Standard Documents Repository">
<item>MIPS:
<url url="http://www.mips.com/publications/"
name="MIPS Online Publications Library">
<item>PPC:
<url url="http://www.lightsoft.co.uk/Fantasm/Beginners/begin1.html"
name="Beginners Guide to PowerPC Assembly Language">
</itemize>
<verb>
Ok you have a number of options to graphics in Linux. Which one you use
depends on what you want to do. There isn't one Web site with all the
information but here are some tips:
<sect1>Somehow related projects<label id="res-related">
SVGALib: This is a C library for console SVGA access.
Pros: very easy to learn, good coding examples, not all that different
from equivalent gfx libraries for DOS, all the effects you know from DOS
can be converted with little difficulty.
Cons: programs need superuser rights to run since they write directly to
the hardware, doesn't work with all chipsets, can't run under X-Windows.
Search for svgalib-1.4.x on http://ftp.is.co.za
Framebuffer: do it yourself graphics at SVGA res
Pros: fast, linear mapped video access, ASM can be used if you want :)
Cons: has to be compiled into the kernel, chipset-specific issues, must
switch out of X to run, relies on good knowledge of linux system calls
and kernel, tough to debug
Examples: asmutils (http://www.linuxassembly.org) and the leaves example
and my own site for some framebuffer code and tips in asm
(http://ma.verick.co.za/linux4k/)
Xlib: the application and development libraries for XFree86.
Pros: Complete control over your X application
Cons: Difficult to learn, horrible to work with and requires quite a bit
of knowledge as to how X works at the low level.
Not recommended but if you're really masochistic go for it. All the
include and lib files are probably installed already so you have what
you need.
Low-level APIs: include PTC, SDL, GGI and Clanlib
Pros: very flexible, run under X or the console, generally abstract away
the video hardware a little so you can draw to a linear surface, lots of
good coding examples, can link to other APIs like OpenGL and sound libs,
Windows DirectX versions for free
Cons: Not as fast as doing it yourself, often in development so versions
can (and do) change frequently.
Examples: PTC and GGI have excellent demos, SDL is used in sdlQuake,
Myth II, Civ CTP and Clanlib has been used for games as well.
High-level APIs: OpenGL - any others?
Pros: clean api, tons of functionality and examples, industry standard
so you can learn from SGI demos for example
Cons: hardware acceleration is normally a must, some quirks between
versions and platforms
Examples: loads - check out www.mesa3d.org under the links section.
To get going try looking at the svgalib examples and also install SDL
and get it working. After that, the sky's the limit.
</verb>
<sect2>How do I debug pure assembly code under Linux?
<p>
An answer from <url url="mailto:dl@gazeta.ru" name="Dmitry Bakhvalov">:
<itemize>
<item><url url="http://www.cryogen.com/Nasm/"
name="NASM"> (portable x86 assembler with Intel syntax)
<item><url url="http://biew.sourceforge.net"
name="BIEW"> (portable console hex viewer/editor with built-in disassembler)
<item><url url="http://wildsau.idv.uni-linz.ac.at/mfx/upx.html"
name="UPX"> (portable executable packer for several formats)
<item><url url="http://hermes.terminal.at/intel2gas/"
name="Intel2gas"> (converter between AT&amp;T and Intel assembler syntax)
<item><url url="http://www.multimania.com/~placr/"
name="A2I"> (converter from AT&amp;T to NASM Intel assembler syntax)
<item><url url="http://asmjournal.freeservers.com"
name="Assembly Programming Journal"> (has articles on Linux/Unix assembly programming)
</itemize>
<verb>
Personally, I use gdb for debugging asmutils. Try this:
1) Use the following stuff to compile:
$nasm -f elf -g smth.asm
$ld -o smth smth.o
<sect1>General pointers<label id="res-general">
2) Fire up gdb:
$gdb smth
3) In gdb:
(gdb) disassemble _start
Place a breakpoint at <_start+1> (If placed at _start the breakpoint
wouldnt work, dunno why)
(gdb) b *0x8048075
To step thru the code I use the following macro:
(gdb)define n
>ni
>printf "eax=%x ebx=%x ...etc...",$eax,$ebx,...etc...
>disassemble $pc $pc+15
>end
Then start the program with r command and debug with n.
Hope this helps.
</verb>
<sect2>Any other useful debugging tools?
<p>
Definitely <tt/strace/ can help a lot (<tt/ktrace/ and <tt/kdump/ on FreeBSD),
it is used to trace system calls and signals. Read <tt/man strace/ for details.
<itemize>
<item><url url="http://webster.cs.ucr.edu/Page_asm/ArtOfAsm.html"
name="The Art Of Assembly">
<item><url url="http://www2.dgsys.com/&tilde;raymoon/faq/"
name="x86 assembly FAQ">
<item><url url="ftp://ftp.luth.se/pub/msdos/"
name="ftp.luth.se"> mirrors the hornet and x2ftp
former archives of msdos assembly coding stuff
<item>Fun stuff: <url url="http://www.koth.org"
name="CoreWars">, a fun way to learn assembly in general
<item>Usenet:
<url url="news://comp.lang.asm.x86" name="comp.lang.asm.x86">;
<url url="news://alt.lang.asm" name="alt.lang.asm">
</itemize>
<sect2>How do I access BIOS functions from Linux (BSD, BeOS, etc)?
<p>
Noway. This is protected mode, use OS services instead.
Again, you can't use <tt/int 0x10/, <tt/int 0x13/, etc.
Fortunately almost everything can be implemented
through system calls or library functions.
In the worst case you may go through direct port access,
or make a kernel patch to implement needed functionality.
<em/That's all for now, folks/.
$Id$