How to utilize PowerPC pre-existing flash resident code ???

[Jon Miller <jmiller at silcom dot com>]

Hello,

I am trying to make the world's simplest example of a c program
utilizing pre-existing PowerPC flash resident code.

I hope someone there can look at this and at least point me to a
reference;

BACKGROUND :

    I am using the gnu tools for powerpc with cygwin.dll.

    The pre-existing function resides at 0x00010ff8 in physical memory.

    <main.c> calls <jon.s> in order to jump to the phy address but it
doesn't work?

    Here is  the resulting disassembly of the jump statement
       4:   48 01 0f fa     ba      10ff8 <wc_lbl+0x10ff8>     <--- ????

QUESTIONS:

1) Where can I read how to do this?

2)  Could  I do this directly from c with no s file?

3) How can I fix my existing setup?

Thanks,  Jon Miller 805-564-3119
www.jrmconsultants.com




====================================
(c code)

int main(void)
{
        *(int *)PBDIR  |=  0x2000;    /* PB 18 = Out */
        asm volatile (
                ".extern wc_lbl;"
                "bl wc_lbl;"    // use a stepping stone
                );
        return 0;
}

====================================
(asm  code)

#include "ppc-asm.h"
        .file   "jon.S"
        .text
.Lptr:
        .globl  wc_lbl
        .type   wc_lbl,@function
wc_lbl:
   mfspr    r30,LR      /* Save the Link Register value. */
   ba       0x00010ff8  /* jump to abs adr in low memory ??? */  ,
   mtspr    LR,r30      /* restore original Link Register value  */
   bclr  20,0           /*return */

====================================
(binary dump)

 powerpc-elf-objdump --disassemble jon.o
 jon.o:     file format elf32-powerpc
 Disassembly of section .text:

00000000 <wc_lbl>:
   0:   7f c8 02 a6     mflr    r30
   4:   48 01 0f fa     ba      10ff8 <wc_lbl+0x10ff8>     <--- ????
   8:   7f c8 03 a6     mtlr    r30
   c:   4e 80 00 20     blr

====================================
(loader script)

SECTIONS
{
        . = 0x00800000;
        .text : { *(.text) }
        .data : { *(.data) }
        .bss : { *(.bss) }
        __bss_start = .;
/*      . += 0x100; */
        __bss_end = .;
        __sbss_start = .;
/*      . += 0x100; */
        __sbss_end = .;
        . += 0x100;
PROVIDE (__stack = .);
        _end = .;
        .debug_info     0 : { *(.debug_info) }
        .debug_abbrev   0 : { *(.debug_abbrev) }
        .debug_line     0 : { *(.debug_line) }
        .debug_frame    0 : { *(.debug_frame) }
}

====================================
(cygwin makefile script)

    # POWER PC EXAMPLE MAKEFILE

PROC=powerpc
#TYPE=srec
TYPE=elf
TARGETBOARD=jon

# OTHER PRECONFIGURED TARGET BOARD LINK SCRIPTS:
#TARGETBOARD=SBC403
#TARGETBOARD=8260ADS
#TARGETBOARD=823FADS

PATH=/usr/local/bin:/usr/bin:$PATH
LIBPATH=/usr/local/$(PROC)-$(TYPE)/lib
INCPATH=/usr/local/$(PROC)-$(TYPE)/include
CC=$(PROC)-$(TYPE)-gcc
AS=$(PROC)-$(TYPE)-as
AR=$(PROC)-$(TYPE)-ar
LD=$(PROC)-$(TYPE)-ld
NM=$(PROC)-$(TYPE)-nm
OBJDUMP=$(PROC)-$(TYPE)-objdump

test:
        $(CC) -g -c --gstabs -o jon.o jon.S
        $(CC) -g -c test.c
        $(LD) -g -v -t -Tldscript_$(TARGETBOARD) -o test test.o jon.o
        $(NM) test
        objcopy test test.s2 -O srec

====================================

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