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(nasm.info)Chapter 8

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Chapter 8: Writing 32-bit Code (Unix, Win32, DJGPP)
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   This chapter attempts to cover some of the common issues involved
when writing 32-bit code, to run under Win32 or Unix, or to be linked
with C code generated by a Unix-style C compiler such as DJGPP. It
covers how to write assembly code to interface with 32-bit C routines,
and how to write position-independent code for shared libraries.

   Almost all 32-bit code, and in particular all code running under
`Win32', `DJGPP' or any of the PC Unix variants, runs in _flat_ memory
model. This means that the segment registers and paging have already
been set up to give you the same 32-bit 4Gb address space no matter
what segment you work relative to, and that you should ignore all
segment registers completely. When writing flat-model application code,
you never need to use a segment override or modify any segment
register, and the code-section addresses you pass to `CALL' and `JMP'
live in the same address space as the data-section addresses you access
your variables by and the stack-section addresses you access local
variables and procedure parameters by. Every address is 32 bits long
and contains only an offset part.

Section 8.1

Interfacing to 32-bit C Programs

Section 8.2

Writing NetBSD/FreeBSD/OpenBSD and Linux/ELF Shared Libraries