Re: porting assembly file to compiled using GNU linker rather than ARMLINK

["Simon Berry" <simon at sanpeople dot com>]

Hi Ben

I am not sure if this is the definitive answer, but it is how I go about
doing it....

Firstly you need to have a linker script, example follows :

/*---------------------------------------------------*/

MEMORY {

        ram : ORIGIN = 0x202000, LENGTH = 0x2000

        rom : ORIGIN = 0x0, LENGTH = 0x2000

}

SECTIONS {

        .text : {

                PROVIDE(_stext = . );

                *(.text)

                . = ALIGN(4);

                PROVIDE(_etext = . );

                #(in your case you would probably need to do something like
:

                #PROVIDE(_Image$$RO$$Limit);


#---------------------------------------------------------------------------
---)

        } > rom

        .data : {

                PROVIDE(_sdata = . );

                *(.data)

                *(.rodata)

                *(.glue_7*)

                . = ALIGN(4);

                PROVIDE(_edata = . );

           } > ram

            .bss : {

                PROVIDE(_sbss = . );

                *(.bss)

                . = ALIGN(4);

                PROVIDE(_ebss = . );

            } > ram

            . += 0x1000;

            PROVIDE(_stack = .);

            PROVIDE(_end =.);

            }



/*------------------------------------------------------------*/

then in your aseembler file you can reference the symbols, as shown in my
crt0 below :

/*--------------------------------------------------------------*/

    .text

    .align

    .global main,_main

main:

_main:

    # copy .data section

    ldr r3, =_etext

    ldr r4, =_sdata

    ldr r5, =_edata

    subs r5, r5, r4

    bl copydata



    # clear .bss section

    ldr r4, =_sbss

    ldr r5, =_ebss

    subs r5, r5, r4

    bl clearbss




    # and jump to the kernel

    b boot



copydata:

    subs r5, r5, #4

    ldr r6, [r3], #4

    str r6, [r4], #4

    bne copydata

    mov pc, lr

clearbss:

    subs r5, r5, #4

    str r0, [r3], #4

    bne clearbss

    mov pc. lr



bss_start:

    .word _sbss

bss_end:

    .word _ebss

text_end:

    .word _etext

data_start:

    .word _sdata

data_end:

    .word _edata

stack_start:

    .word _stack

end:

    .word _end



/*------------------------------------------------------*/



The linker script file must be included in the linker flags with the -T
option.

Hope this helps

Regards

Simon



----- Original Message -----
From: <benjaminlee001 at shaw dot ca>
To: <crossgcc at sources dot redhat dot com>
Sent: Saturday, March 01, 2003 1:57 AM
Subject: porting assembly file to compiled using GNU linker rather than
ARMLINK


> Hi all,
>
> I've got a question regarding the use of GNU linker.
>
> I am trying to compile an assembler file using GNU as and ld.  The file is
a file to setup the C envoirnment and is originally built using ARM SDT
armasm and armlink.  I've changed all the directives in the file so that it
would compile under GNU as.  But when I try to link the file together with
other source files, it gives me a message saying that "undefined reference
to `Image$$RO$$Limit'" in that file.  The symbol "Image$$RO$$Limit'"
represents the code size and is determined at link time by armlink.  So how
can I get GNU linker to define the symbol at link time so I can build the
object file successfully?  The portion of code that contains that symbol is
listed below.
>
> >  IMPORT  |Image$$RO$$Limit|      ; End of ROM code (=start of ROM data)
> >  IMPORT  |Image$$RW$$Base|       ; Base of RAM to initialise
> >  IMPORT  |Image$$ZI$$Base|       ; Base and limit of area
> >  IMPORT  |Image$$ZI$$Limit|      ; to zero initialise
> >
> >        LDR     r0, =|Image$$RO$$Limit| ; Get pointer to ROM data
> >        LDR     r1, =|Image$$RW$$Base|  ; and RAM copy
> >        LDR     r3, =|Image$$ZI$$Base|  ; Zero init base to top of
initialised data
> >        CMP     r0, r1                  ; Check that they are different
> >        BEQ     %F1
> >0       CMP     r1, r3                  ; Copy init data
> >        LDRCC   r2, [r0], #4
> >        STRCC   r2, [r1], #4
> >        BCC     %B0
> >1       LDR     r1, =|Image$$ZI$$Limit| ; Top of zero init segment
> >        MOV     r2, #0
> >2       CMP     r3, r1                  ; Zero init
> >        STRCC   r2, [r3], #4
> >        BCC     %B2
>
> Please help me out on this,
>
> Thank you so much,
>
> Ben
>
>
> ------
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