6 ms·

Linux Assembly How-to

99 points by rspivak 10y ago

znpy 10y ago
It would be nice to see this document updates, pages like http://www.tldp.org/HOWTO/Assembly-HOWTO/gcc.html http://www.tldp.org/HOWTO/Assembly-HOWTO/gcc.html still references gcc 2.7 and older.
TempleOS 10y ago
My assembler is like cat walks with no guard rails. It won't signal all invalid instructions and its missing instructions and has some nonstandard OPCODES. I guess I should make it better for the public. It cuts corners on 16-bit assembly, but that's off-limits in a 64-bit operating system anyway. I'll wait for people to start complaining. God says... systems resoluteness's clearinghouses Bismark's aquatic sieve's yesterdays thumbs contemplated haystack explicate bops bristles palomino's bobcat's stratagem Formosan microphone's sores vermicelli's obtaining hart's bootleggers abattoir's retrace dimmest philatelists matrixes hiccup dominoes inefficiently rotate
TomMasz 10y ago
I was quite adept at 6800 and 68000 assembler but I can't imagine getting to that level with modern x86. Maybe some glue routines, but beyond that give me any of the current compilers.
- ndesaulniers 10y ago
  https://nickdesaulniers.github.io/blog/2014/04/18/lets-write-some-x86-64/ https://nickdesaulniers.github.io/blog/2014/04/18/lets-write...
  - csense 10y ago
    It looked promising right up until the first code, and then I saw you're writing in AT&T syntax. AT&T syntax is such an abomination against nature and the gods of computing that every time I see it I want to gouge my eyes out. AT&T syntax is this weird awful syntax only used by GNU as. The syntax is some leftover from an assembler from the early UNIX days which was clearly written by a very lazy person. Whoever came up with it apparently thought to themselves, "If we make source files put a % character in front of registers and a $ character in front of constants, then I don't have to think too hard about how to write a parser. If we make source files specify their width in a suffix, then we don't have to think too hard about how to get this information out of the register name. And let's put our operands in (source, destination) order instead of (destination, source) order just to be evil and confuse people!" Aaagggghh. If gas wasn't used as the backend of gcc, I guarantee exactly zero people would use it, because AT&T syntax is so awful. You should consider posting an update using NASM / YASM (or if you feel you must use GAS, use its directive for Intel syntax). Your readers will thank you.
    - ndesaulniers 10y ago
      You should do it on your blog.
AdmiralAsshat 10y ago
Trying to read through "Programming From the Ground Up" (a GNU book on Assembly), and having some trouble keeping track of what I've thrown into what register. Does anyone have a recommendation for an IDE or debugger that can let me inspect my registers at a given step of the program?
- briansteffens 10y ago
  gdb is magic once you get the hang of it, I'd definitely recommend spending some time getting comfortable with it.
  - AdmiralAsshat 10y ago
    I know my way around GDB, but only as a C debugger. Haven't really used it for Assembly.
    - sigjuice 10y ago
      (gdb) help si Step one instruction exactly. (gdb) help ni Step one instruction, but proceed through subroutine calls. (gdb) help info registers List of integer registers and their contents, for selected stack frame. Register name as argument means describe only that register. (gdb) layout reg # to enable view of registers in split screen Also, you can use register names in expressions. e.g. p $r11 All of this is applicable when debugging a C program as well.
      - AdmiralAsshat 10y ago
        `layout reg` Did exactly what I wanted. Thank-you so much!
  - barrkel 10y ago
    I've found it very buggy when working at the assembly level on a complex program (e.g. JVM). I think it coredumped on average every 5 minutes as I tried to step through things or set breakpoints.
heinrichhartman 10y ago
From http://www.tldp.org/HOWTO/Assembly-HOWTO/external.html http://www.tldp.org/HOWTO/Assembly-HOWTO/external.html: About m4 macro-processor: "However, its disfunctional quoting and unquoting semantics force you to use explicit continuation-passing tail-recursive macro style if you want to do advanced macro programming (which is remindful of TeX -- BTW, has anyone tried to use TeX as a macroprocessor for anything else than typesetting ?)." This is a great point! The TeX Macro language is so much better than M4 quoting syntax. I'd love to have it available for e.g. writing blog-posts in HTML or coding. It seems that the tex macroprocessor can not be used independently of latex, which is a pitty. There are m4 clones with TeX-like syntax (e.g. http://www.nongnu.org/t4/ http://www.nongnu.org/t4/) - but none of those seems to be used much. To see what's possible with just assembly and macros see Tannenbaums paper: https://www.computer.org/csdl/trans/ts/1976/02/01702350.pdf https://www.computer.org/csdl/trans/ts/1976/02/01702350.pdf
- groovy2shoes 10y ago
  I'm a fan of TeX2page[1] for converting (La)TeX to HTML. There are also similar TeX/Scribe-inspired markup processors. Scribble[2] comes to mind, and Chibi Scheme[3] even comes with a very lightweight, very configurable "Scribble" processor in the form of `chibi-doc`. Chibi's flavor is a little more similar to TeX (using '\' as the leader rather than '@', for example), if that's important to you. [1]: https://ds26gte.github.io/tex2page/index.html https://ds26gte.github.io/tex2page/index.html [2]: https://docs.racket-lang.org/scribble/index.html https://docs.racket-lang.org/scribble/index.html [3]: http://synthcode.com/wiki/chibi-scheme http://synthcode.com/wiki/chibi-scheme And here's Chibi's own manual written in it: https://github.com/ashinn/chibi-scheme/blob/master/doc/chibi.scrbl https://github.com/ashinn/chibi-scheme/blob/master/doc/chibi... I think it would be freakishly easy to adapt chibi-doc into a general text preprocessor rather than an HTML generator, and honestly I've thought about it before. I may just do it yet :)
  - heinrichhartman 10y ago
    Wow, tex2page looks really great. I'll might setup a JEKYLL workflow for using it to write blog posts. LaTeX doc semantics are so much better than Markdown / HTML. Also I can see a LISP style macro processor being super awesome. Let me know if you are going to adapt chibi-doc that way.

99 points by rspivak 10y ago

znpy 10y ago

It would be nice to see this document updates, pages like http://www.tldp.org/HOWTO/Assembly-HOWTO/gcc.html http://www.tldp.org/HOWTO/Assembly-HOWTO/gcc.html still references gcc 2.7 and older.

TempleOS 10y ago

My assembler is like cat walks with no guard rails. It won't signal all invalid instructions and its missing instructions and has some nonstandard OPCODES. I guess I should make it better for the public. It cuts corners on 16-bit assembly, but that's off-limits in a 64-bit operating system anyway. I'll wait for people to start complaining. God says... systems resoluteness's clearinghouses Bismark's aquatic sieve's yesterdays thumbs contemplated haystack explicate bops bristles palomino's bobcat's stratagem Formosan microphone's sores vermicelli's obtaining hart's bootleggers abattoir's retrace dimmest philatelists matrixes hiccup dominoes inefficiently rotate

TomMasz 10y ago

I was quite adept at 6800 and 68000 assembler but I can't imagine getting to that level with modern x86. Maybe some glue routines, but beyond that give me any of the current compilers.

ndesaulniers 10y ago
https://nickdesaulniers.github.io/blog/2014/04/18/lets-write-some-x86-64/ https://nickdesaulniers.github.io/blog/2014/04/18/lets-write...
- csense 10y ago
  It looked promising right up until the first code, and then I saw you're writing in AT&T syntax. AT&T syntax is such an abomination against nature and the gods of computing that every time I see it I want to gouge my eyes out. AT&T syntax is this weird awful syntax only used by GNU as. The syntax is some leftover from an assembler from the early UNIX days which was clearly written by a very lazy person. Whoever came up with it apparently thought to themselves, "If we make source files put a % character in front of registers and a $ character in front of constants, then I don't have to think too hard about how to write a parser. If we make source files specify their width in a suffix, then we don't have to think too hard about how to get this information out of the register name. And let's put our operands in (source, destination) order instead of (destination, source) order just to be evil and confuse people!" Aaagggghh. If gas wasn't used as the backend of gcc, I guarantee exactly zero people would use it, because AT&T syntax is so awful. You should consider posting an update using NASM / YASM (or if you feel you must use GAS, use its directive for Intel syntax). Your readers will thank you.
  - ndesaulniers 10y ago
    You should do it on your blog.

AdmiralAsshat 10y ago

Trying to read through "Programming From the Ground Up" (a GNU book on Assembly), and having some trouble keeping track of what I've thrown into what register. Does anyone have a recommendation for an IDE or debugger that can let me inspect my registers at a given step of the program?

briansteffens 10y ago
gdb is magic once you get the hang of it, I'd definitely recommend spending some time getting comfortable with it.
- AdmiralAsshat 10y ago
  I know my way around GDB, but only as a C debugger. Haven't really used it for Assembly.
  - sigjuice 10y ago
    (gdb) help si Step one instruction exactly. (gdb) help ni Step one instruction, but proceed through subroutine calls. (gdb) help info registers List of integer registers and their contents, for selected stack frame. Register name as argument means describe only that register. (gdb) layout reg # to enable view of registers in split screen Also, you can use register names in expressions. e.g. p $r11 All of this is applicable when debugging a C program as well.
    - AdmiralAsshat 10y ago
      `layout reg` Did exactly what I wanted. Thank-you so much!
- barrkel 10y ago
  I've found it very buggy when working at the assembly level on a complex program (e.g. JVM). I think it coredumped on average every 5 minutes as I tried to step through things or set breakpoints.

heinrichhartman 10y ago

From http://www.tldp.org/HOWTO/Assembly-HOWTO/external.html http://www.tldp.org/HOWTO/Assembly-HOWTO/external.html: About m4 macro-processor: "However, its disfunctional quoting and unquoting semantics force you to use explicit continuation-passing tail-recursive macro style if you want to do advanced macro programming (which is remindful of TeX -- BTW, has anyone tried to use TeX as a macroprocessor for anything else than typesetting ?)." This is a great point! The TeX Macro language is so much better than M4 quoting syntax. I'd love to have it available for e.g. writing blog-posts in HTML or coding. It seems that the tex macroprocessor can not be used independently of latex, which is a pitty. There are m4 clones with TeX-like syntax (e.g. http://www.nongnu.org/t4/ http://www.nongnu.org/t4/) - but none of those seems to be used much. To see what's possible with just assembly and macros see Tannenbaums paper: https://www.computer.org/csdl/trans/ts/1976/02/01702350.pdf https://www.computer.org/csdl/trans/ts/1976/02/01702350.pdf

groovy2shoes 10y ago
I'm a fan of TeX2page[1] for converting (La)TeX to HTML. There are also similar TeX/Scribe-inspired markup processors. Scribble[2] comes to mind, and Chibi Scheme[3] even comes with a very lightweight, very configurable "Scribble" processor in the form of `chibi-doc`. Chibi's flavor is a little more similar to TeX (using '\' as the leader rather than '@', for example), if that's important to you. [1]: https://ds26gte.github.io/tex2page/index.html https://ds26gte.github.io/tex2page/index.html [2]: https://docs.racket-lang.org/scribble/index.html https://docs.racket-lang.org/scribble/index.html [3]: http://synthcode.com/wiki/chibi-scheme http://synthcode.com/wiki/chibi-scheme And here's Chibi's own manual written in it: https://github.com/ashinn/chibi-scheme/blob/master/doc/chibi.scrbl https://github.com/ashinn/chibi-scheme/blob/master/doc/chibi... I think it would be freakishly easy to adapt chibi-doc into a general text preprocessor rather than an HTML generator, and honestly I've thought about it before. I may just do it yet :)
- heinrichhartman 10y ago
  Wow, tex2page looks really great. I'll might setup a JEKYLL workflow for using it to write blog posts. LaTeX doc semantics are so much better than Markdown / HTML. Also I can see a LISP style macro processor being super awesome. Let me know if you are going to adapt chibi-doc that way.