                       Absolute Linker Program
                             Version 1.1

INTRODUCTION

This program accepts MS-DOS .OBJ and .LIB files and an entered set

of absolute segment addresses and generates a simple binary image file suitable for use as a .COM file, ROM, boot program or device driver. Most (all?) standard MS-DOS linkers can only generate a contiguous image which is less than 64K and which begins at 0. This program can generate any size image (any memory model may be used) and each segment in the image can be placed anywhere in the 1MB memory map.

COMPILING

Compile under UNIX or in MS-DOS compact model

COMMAND FORMAT and OPERATION

alink [-q] [-o outputfile] [-l listingfile] files

'-q' Quiet mode: Suppresses messages

'files' List object file and library file names. Also, text files containing whitespace separated lists of more file names may be specified

After the command is invoked, it displays a list of the segments and class groupings on the output. You then enter segment positioning data in this format:

XXXXX[,YYYYY] list

Where: XXXXX is a absolute 20-bit address in hexadecimal indicating where the segments in the list are to be linked.

YYYYY is an optional load address if it's to be different from the link
      address.

list  is the names of the segments.  If a class name is given, all
      the segments in the class are specified.  Private segments may
      also be specified by giving them in this format: SEGMENT(MODULE)

EXAMPLES

To generate a .COM file using Turbo-C 2.0:

test.c: main() { printf("Hello world\n"); }

>tcc -c -mt test.c
>alink -o test.com c0t.obj test.obj cs.lib

Segments: _TEXT _BSSEND _EMUSEG _SCNSEG _BSS _CRTSEG _DATA _CVTSEG

Classes: 'BSS'(_BSS) 'STACK'(_BSSEND) 'DATA'(_EMUSEG,_DATA,_SCNSEG,_CRTSEG,
_CVTSEG) 'CODE'(_TEXT)

>0 CODE DATA BSS STACK

Example of embedded system. The linker says:

Segments: _TEXT _SCNSEG _BSS _DATA _CVTSEG _START(c0t.asm)
Classes: BSS(_BSS) DATA(_DATA,_SCNSEG,_CVTSEG) CODE(_TEXT)

Then you could respond with:

> 00000 BSS
> 0F000 _TEXT DATA
> FFFF0,FFF0 _START(c0t.asm)

This would be appropriate for burning a 4K ROM for an embedded system where only 16-bits of address decoding are present and where 32K of RAM exists at address 0 and where the ROM exists at address 0F000. The private segment '_START(c0t.asm)' could be this:

_START segment byte assume cs:_START xor ax,ax mov ds,ax mov ss,ax mov sp,08000H jmp FAR PTR _main _START ends

A simple startup routine for a Turbo-C program. Since the upper 4 bits of the address are ignored, the ROM exists at 0F000 as well as FF000. You want the startup code to be linked for FFFF0 (the reset CS:IP value) therefore, but to be placed at 0FFF0 in the image.

FEATURES/RESTRICTIONS

The first byte of the generated output file is the first byte generated, not address 0 (unless code or data are generated there). In the above example, the first byte of the output file is address 0F000 and the output file is 4K in size.
A very detailed listing including a symbol cross-referencing listing and a list showing where each module is placed is generated if the '-l' option is used.
All symbols are case sensitive
There is no limit to the size of the binary image file EXCEPT that all of the generated code for it must fit in RAM when the linker is running (I.E., the entire 1MB image does not have to fit in ram if 4K is generated at 0 and 4K is generated at FF000).
No error checking is performed on external references. If an external reference is out of range, an invalid address will be generated.
Segment overflow, group overflow and segment overlap checking is performed, however.
32-bit 386 code is not supported. If someone knows the format of the 386 .OBJ file records, please send it to me so I can eliminate this restriction.
Works on Xenix for Xenix .o files as well.

Joseph H. Allen (jhallen@world.std.com)

Alink

Install / Use

README