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--- ackassemblylanguage [2014/11/11 14:52]
127.0.0.1 external edit
+++ ackassemblylanguage [2015/01/03 13:05] (current)
antoineleca Clearly mark this page as completely irrelevant to current MINIX (!)
@@ Line 1: / Line 1: @@
+<div round alert>
+This page describes the assembly language(s) used in MINIX 1.6, MINIX 2.0 and MINIX 3.1. It is not relevant to recent (after 2010) releases of MINIX.</div>
+====== MINIX ACK Assembly Language ======
+===== What do the pseudo-ops in Minix assembly code mean? =====
+An ACK assembly file can have a number of sections. Things
+declared in the same section are collected together by the loader
+in the order they are found in an assembly file and in the order
+the object files are loaded together.
+Sections get meaning once they are put in a Minix binary.
+Section 0 (usually named //.text//) contains program code and is
+put in the code segment, section 1 (//.rom//) is read-only data
+and is put in the data segment, and so are section 2 (//.data//)
+for read-write data and section 3 (//.bss//) for read-write data
+initialized to zero.
+The ACK binary to Minix binary converter (//cv//) will
+complain if there are nonzero objects in the //.bss// section,
+but it doesn't care if there's code in //.rom//, //.data//, or
+data in //.text//.
+With //.define// a label is turned into a global variable
+that other files can use, otherwise it stays local to the assembly
+file it is in. With //.extern// one can import a global label,
+but the assembler seems to do that automatically anyway.
+With //.comm// (or //.lcomm//) you can put a label on a bunch of zeros. This
+is useful in the //.bss// section. The difference
+between "//.comm junk, 10//" and "//junk: .space 10//" only appears when
+the label is made global: multiple //common// declarations are merged at
+link-time, while multiple //space//d variables will conflict.
+With //.align// you can insert the number of zeros needed to
+align //.// (the address where stuff is put) to a given
+multiple. Objects bigger than a byte should be aligned to multiples
+of 2 or 4 bytes. Otherwise it will be slow on 386 descendants,
+and may cause alignment fault messages on a 486+.
+With //.data[124]// you can assemble 1, 2 or 4 byte sized
+numbers. With //.ascii "xyz"//, and //.asciz "xyz"// you
+can do the same as with //.data1 120, 121, 122// and ''.data1
+, 121, 122, 0''.
+===== In the code there are lines starting with ".sect". What do they mean? =====
+At the beginning of the code there is a line: ".sect .text; .sect .rom; .sect .data; .sect .bss", or there is ".sect .text begtext:". In the code ".sect .text" shows up again. What do these mean? What is the explanation of the segments in Minix assembly code?
+A new section name opens up a new section. By naming all
+sections in the first line you can be sure that the names are tied
+to the proper section numbers.
+===== How are comments indicated? =====
+The comment character is **//!//**. The C preprocessor is run
+on an assembly file if the very first character is a **//#//**. If
+so, then the **///*... *///** comment characters also work,
+because the C preprocessor removes C comments. The quote characters
+**//(', ")//** are a bit of a problem, because the
+preprocessor wants them to match. This is why you see **// '' (backquote)//** used in comments sometimes where one would normally use a **// ' (single quote)//**.
+=====  Inconsistency in syntax =====
+<code>
+From: drminix@naver.com (Sam)
+Subject: assembly syntax inconsistency in MINIX.
+Date: 31 May 2004 19:42:42 -0700
+I was reading two different MINIX assembly files, masterboot.s and
+mpx386.s. I then came across some differences between the assembly
+syntax used in each files.
+In mpx386.s, each section starts with .sect followed by the section
+name. For example, a text section starts with .sect .text
+However in masterboot.s, a text section starts with just .text
+MASTERBOOT.S  |     MPX386.s
+---------------------------------------
+.text         |   .sect .text
+.data         |   .sect .data
+And also, the pound sign(#) is used to indicate an immediate data in
+masterboot.s whereas using a pound sign(#) in mpx386.s gives you an
+error.
+I guess minix compiler understands both syntax. Can anyone tell me why
+there are two different ways to start a section?
+</code>
+<code>
+From: kjb=733616@cs.vu.nl (Kees J Bot)
+Subject: Re: assembly syntax inconsistency in MINIX.
+Date: Tue, 1 Jun 2004 12:18:58 +0200
+There's that, and there's this:
+mov ax, #10         |     mov ax, 10
+mov ax, variable    |     mov ax, (variable)
+The syntax for the 16-bit assembler under the 16-bit version was changed
+to be like Xenix or something.  I have no idea why.
+The 32-bit assembler uses the syntax on the right, both with 8086 and
+input.  I had to make an assembly syntax converter to allow this
+assembler to process the Xenix syntax.  The -Was-ncc option tells the
+compiler driver that the assembly input is the "new cc" syntax.  (Yes,
+there's also an "old cc" syntax.  Luckily we buried that.)
+Kees J. Bot
+Modified 12 March 2003
+</code>

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