AT&T Assembly
vivek, Mon, 2003-09-01 23:53
Updated: May/10 ‘06
This article is a ‘quick-n-dirty’ introduction to the AT&T assembly language syntax, as implemented in the GNU Assembler as(1). For the first timer the AT&T syntax may seem a bit confusing, but if you have any kind of assembly language programming background, it’s easy to catch up once you have a few rules in mind. I assume you have some familiarity to what is commonly referred to as the INTEL-syntax for assembly language instructions, as described in the x86 manuals. Due to its simplicity, I use the NASM (Netwide Assembler) variant of the INTEL-syntax to cite differences between the formats.
The GNU assembler is a part of the GNU Binary Utilities (binutils), and a back-end to the GNU Compiler Collection. Although as is not the preferred assembler for writing reasonably big assembler programs, its a vital part of contemporary Unix-like systems, especially for kernel-level hacking. Often criticised for its cryptic AT&T-style syntax, it is argued that as was written with an emphasis on being used as a back-end to GCC, with little concern for “developer-friendliness”. If you are an assembler programmer hailing from an INTEL-Syntax background, you’ll experience a degree of stifling with regard to code-readability and code-generation. Nevertheless, it must be stated that, many operating systems’ code-base depend on as as the assembler for generating low-level code.
