RE: [avr-gcc-list] avr-objcopy not copying custom section...

[Boyapati, Anitha]

➢ asm("  .section .version,\"x\"\n"

Actually, looking back, I don’t get the meaning of this. How can a section be 
‘executable’ without being ‘allocatable’ in ELF?

Anitha

________________________________________
From: address@hidden [mailto:address@hidden On Behalf Of Bill Westfield
Sent: Friday, February 25, 2011 2:51 PM
To: address@hidden
Subject: [avr-gcc-list] avr-objcopy not copying custom section...

I am trying to add a version number to my program, to be located at an absolute 
flash address.
But it looks like I can't get avr-objcopy to copy the section that I have put 
this data in.

I have in my .C file:

     asm("  .section .version,\"x\"\n"
    "optboot_version:  .word " MAKEVER(OPTIBOOT_MAJVER, OPTIBOOT_MINVER) "\n"
    "  .word 0x1234\n"
    "  .section .text\n");

And then I link with (for example):

      LDSECTIONS  = -Wl,--section-start=.text=0x3e00 
-Wl,--section-start=.version=0x3ffc

this seems to produce a correct .elf file:
optiboot_diecimila.elf:     file format elf32-avr

Sections:
Idx Name          Size      VMA       LMA       File off  Algn
  0 .text         000001d6  00003e00  00003e00  00000054  2**1
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
  1 .version      00000004  00003ffc  00003ffc  0000022a  2**0
                  CONTENTS, READONLY, CODE
     :

Contents of section .text:
 3e00 112484b7 14be81ff d3d085e0 80938100  .$..............
 3e10 82e08093 c00088e1 8093c100 86e08093  ................
 3e20 c20080e1 8093c400 8ee0bcd0 259a86e0  ............%...
 3e30 20e33cef 91e03093 85002093 840096bb   .<...0... .....
 3e40 b09bfecf 1d9aa895 8150a9f7 99249394  .........P...$..
 3e50 a5e0aa2e f1e1bf2e 9dd08134 21f481e0  ...........4!...
 3e60 b2d083e0 1fc08234 11f484e1 03c08534  .......4.......4
   :
Contents of section .version:
 3ffc 02043412                             ..4.           
Contents of section .debug_aranges:
 0000 24000000 02000000 00000400 00000000  $...............

But objcopy seems to not include this section in output files, producing an
empty hex file (data wise):
BillW-MacOSX-2<8748> /sw/cross/bin/avr-objdump -sh optiboot_diecimila.elf | 
less 
BillW-MacOSX-2<8748> /sw/cross/bin/avr-objcopy -j .version -O ihex 
optiboot_diecimila.elf foo.hex
BillW-MacOSX-2<8749> more foo.hex
:0400000300003E00BB
:00000001FF

Am I missing something obvious or is this some subtle bug to be tracked down?

Thanks
WestfW