[z80-coff-ld] how can I use ld for creating an exe from z80-coff-as ?

[z80-coff-ld] how can I use ld for creating an exe from z80-coff-as ?

[jseb]

Hello,

I've compiled this source file, using z80-coff-as.

~/z80-coff-as -als hello_world.asm -o hello_world.out

GAS LISTING hello_world.asm                     page 1


    1 0000 FE             db $fe
    2 0001 00C0 1AC0      dw debut,fin,debut
    2      00C0
    3
    4 0007 0000 0000      ORG $C000
    4      0000 0000
    4      0000 0000
    4      0000 0000
    4      0000 0000
    5
    6                    debut:
    7 c000 210D C0        LD HL,LABEL
    8 c003 7E            AFF: LD A,(HL)
    9 c004 23             INC HL
   10 c005 A7             AND A
   11 c006 C8             RET Z
   12 c007 CDA2 00        CALL $A2 ; HFDA4 ;CHPUT
   13 c00a 18F7           JR AFF
   14 c00c C9             RET
   15 c00d 5465 7374     LABEL: DEFB "Test chput",13,10,0
   15      2063 6870
   15      7574 0D0A
   15      00
   16                    fin:
   17                     END

GAS LISTING hello_world.asm                     page 2


DEFINED SYMBOLS
                             *ABS*:0000000000000000 fake
      hello_world.asm:6      .text:000000000000c000 debut
      hello_world.asm:16     .text:000000000000c01a fin
      hello_world.asm:15     .text:000000000000c00d LABEL
      hello_world.asm:8      .text:000000000000c003 AFF

NO UNDEFINED SYMBOLS


So, it gives me a COFF object files, and i don't want all those 
sections, as it's for using inside an 8 bit emulator (target is MSX 
machine).
I had success using «coff-z80-objcopy» with binary output, but i'd 
rather like using the linker instead.

I tried with:

~/test$ z80-coff-ld.bfd hello_world.out -o hello_world.msx

~/test$ hexdump hello_world.msx -C
00000000  fe 00 c1 1b c1 00 c1 00  00 00 00 00 00 00 00 00
   |................|
00000010  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
   |................|
*
0000c000  21 0d c1 7e 23 a7 c8 cd  a2 00 18 f7 c9 48 65 6c
   |!..~#........Hel|
0000c010  6c 6f 20 57 6f 72 6c 64  0d 0a 00
   |lo World...|

As you can see, the first bytes show that the origin is now 0xc100 , 
instead of 0xc000.
I guess it's because ld adds 0x100h (old .com startup) to my .org setting.
Another problem is i don't want all those fillers, between stub (the 
first seven bytes) and the start of my code section (at 0xc000).

I want to get this instead:
00000000  fe 00 c0 1b c0 00 c0 21  0d c0 7e 23 a7 c8 cd a2
   |.......!..~#....|
00000010  00 18 f7 c9 48 65 6c 6c  6f 20 57 6f 72 6c 64 0d
   |....Hello World.|
00000020  0a 00

I tried to set up a little ld script, for using with «-T» flag of ld, 
but all i got is the return of «COFF» sections…
SECTIONS
      {
        . = 0xC000;
        .text : { *(.text) }
      }


I've made extensive search on the web, on this list, and on dedicated 
emulators list, but didn't find anything about this problem.
If someone can helpÂ… thank you.

Re: [z80-coff-ld] how can I use ld for creating an exe from z80-coff-as ?

[Alan Modra]

On Tue, Feb 21, 2012 at 10:06:41PM +0100, jseb wrote:
> ... to my .org setting.

.org doesn't do what you think it does.  gas isn't an absolute
assembler, but instead produces relocatable object files.  .org just
adds space to make the offset from the start of the current section
equal to its argument.

You're on the right track in your use of a linker script to set the
start of your code.  Just leave out the .org in the assembly code.

-- 
Alan Modra
Australia Development Lab, IBM

Re: [z80-coff-ld] how can I use ld for creating an exe from z80-coff-as ?

[jseb]

> .org doesn't do what you think it does.  gas isn't an absolute
> assembler, but instead produces relocatable object files.  .org just
> adds space to make the offset from the start of the current section
> equal to its argument.

Ok, i did what you've said, and deleted .org argument in source file.
I've also named sections, with :
  «.stub» for the header.
  «.mycode» for the real code, which should be loaded at 0xC000


    1               	.section .stub
    2 0000 FE        	    db $fe
    3 0001 0000 1B00 	    dw debut,fin,debut
    3      0000
    4               	
    5               	; don't use .ORG directive
    6               	; .ORG $C000
    7               	
    8               	.section .mycode
    9               	;
   10               	debut:
   11 0000 210D 00   	 LD HL,LABEL
   12 0003 7E        	AFF: LD A,(HL)
   13 0004 23        	 INC HL
   14 0005 A7        	 AND A
   15 0006 C8        	 RET Z
   16 0007 CDA2 00   	 CALL $A2 ; HFDA4 ;CHPUT
   17               	;
   18 000a 18F7      	 JR AFF
   19 000c C9        	 RET
   20 000d 4865 6C6C 	LABEL: DEFB "Hello World",13,10,0
   20      6F20 576F
   20      726C 640D
   20      0A00
   21               	fin:
   22               	 END


And then, i've written this script:

OUTPUT_FORMAT(binary)
SECTIONS
      {
        .stub 0xC000 - 7 : { *(.stub) }
        .code : { *(.mycode) }

      }

Using this, i got correct output, working in emulator
00000000  fe 00 c0 1b c0 00 c0 21  0d c0 7e 23 a7 c8 cd a2
   |.......!..~#....|
00000010  00 18 f7 c9 48 65 6c 6c  6f 20 57 6f 72 6c 64 0d
   |....Hello World.|
00000020  0a 00

You see the stub at the beginning:
  FE   (magic)
  00C0 (start adress of code: 0xC000)
  1BC0 (end address: 0xC0B1)
  00C0 (entry point, same as start)

And then,code following with correct relocation for execution at 0xC000.

The ld script is not very nice (the magic number «7»), but i couldn't 
manage to do better.
I you have a suggestion, it will be welcome.

Thank you for helping.

Re: [z80-coff-ld] how can I use ld for creating an exe from z80-coff-as ?

[Chris Smith]

Hi Jseb.

I do a lot of complicated Z80 development using binutils, and have set
up a z80 specific makefile that sorts this all out. I include this
makefile in all my project makefiles to provide all the functionality
I need. I also have a platform specific linker script that defines
useful memory regions that I use. I can then target code to the memory
regions/segments as necessary.

Extracting the final linked binary is done through objcopy, with
listing dumps and map output done through objdump. It does what you
expect, and works beautifully for me at least.

Happy to share this base makefile and linker scripts with you, with
some examples (been meaning to write it all up and publish on my
website....)

Chris



On 21 February 2012 21:52, Alan Modra <amodra@gmail.com> wrote:
>
> On Tue, Feb 21, 2012 at 10:06:41PM +0100, jseb wrote:
> > ... to my .org setting.
>
> .org doesn't do what you think it does.  gas isn't an absolute
> assembler, but instead produces relocatable object files.  .org just
> adds space to make the offset from the start of the current section
> equal to its argument.
>
> You're on the right track in your use of a linker script to set the
> start of your code.  Just leave out the .org in the assembly code.
>
> --
> Alan Modra
> Australia Development Lab, IBM