>Number:         26160
>Category:       port-arm
>Synopsis:       objcopy creates unbootable kernel sometimes
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    port-arm-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Jul 04 08:23:00 UTC 2004
>Closed-Date:
>Last-Modified:
>Originator:     Martin Husemann
>Release:        NetBSD 2.0F
>Organization:
>Environment:
System: NetBSD drowsy.duskware.de 2.0F NetBSD 2.0F (DROWSY) #1: Sat Jun 19 15:21:30 CEST 2004 martin@night-porter.duskware.de:/usr/src/sys/arch/shark/compile/DROWSY shark
Architecture: arm
Machine: shark
>Description:
Sometimes shark a.out kernels are unbootable. Richard Earnshaw analyzed
this to be a bug in objcopy, causing wrong vma for .data and .bss sections.
See http://mail-index.netbsd.org/port-arm/2004/04/27/0002.html for details.
This bug can be worked around by using a ldscript that combines all link_set
sections into .text. Richard proposed a fixed ldscript that does this and
which works for the current kernel sources, but Jason Thorpe insisted on
the dynamic property of link_set additions (i.e. not having to change
ldscripts) and suggested to fix objcopy instead, see
http://mail-index.netbsd.org/port-arm/2004/04/27/0003.html for details.

Now we did not manage to fix objcopy yet, and this needs to be handled
for the 2.0 release.

>How-To-Repeat:
Try to boot a kernel from the autobuild and be unlucky.

>Fix:
There have been various fixes proposed:

 - Write a proper bootloader and start using the ELF kernel itself
   (probably the best long term solution)
 - Fix binutils
 - Hardcode the sections in a ldscript
 - Generate the ldscript on the fly by examining sections found in
   all kernel object files. The following fragment (where *.o should
   be replaced by ${SYSTEM_OBJ}) generates the needed dynamic part;
   the (fixed) head and tail need to be added and maybe this should
   all be done by awk instead...

#! /bin/sh

SETS=`objdump -x *.o | fgrep "RELOCATION RECORDS FOR [link_set" | \
        sort -u | sed 's/^.*\[\(.*\)\]:$/\1/'`

for s in $SETS; do
        printf "  . = ALIGN(4);\n"
        printf "  PROVIDE (__start_%s = .);\n" $s
        printf "  *(%s)\n" $s
        printf "  PROVIDE (__stop_%s = .);\n" $s
done
>Release-Note:
>Audit-Trail:
>Unformatted: