[syslinux] Linker script assertion with binutils 2.21

[H. Peter Anvin]

On 01/17/2011 06:53 AM, Colin Watson wrote:
> dos/syslinux.elf fails to build on current Ubuntu Natty (binutils 2.21)
> as follows:
> 
>   ld -m elf_i386 -T dosexe.ld -o syslinux.elf header.o crt0.o ldlinux.o syslinux.o fat.o syslxmod.o syslxopt.o setadv.o getopt_long.o bootsect_bin.o mbr_bin.o cache.o fatchain.o open.o searchdir.o libcom.a
>   /usr/bin/ld.bfd.real: syslinux_ldlinux_size must equal the size of .payload
>   /usr/bin/ld.bfd.real: syslinux_ldlinux_size must equal the size of .payload
> 
> 'objdump -t ldlinux.o' looks reasonable:
> 
>   SYMBOL TABLE:
>   00000000 l    d  .text  00000000 .text
>   00000000 l    d  .data  00000000 .data
>   00000000 l    d  .bss   00000000 .bss
>   00000000 l    d  .payload       00000000 .payload
>   00000000 l    d  .rodata        00000000 .rodata
>   00000000 g       .payload       00007c00 syslinux_ldlinux
>   00007c00 g       *ABS*  00000000 syslinux_ldlinux_size
>   00000000 g       .rodata        00000004 syslinux_ldlinux_len
> 
> Our toolchain packager pointed me at
> http://sources.redhat.com/git/?p=binutils.git;a=commitdiff;h=557189b0dd1f3dec6b00b91b9b0c5459ece72a52,
> which indeed seems like a likely cause of this kind of failure.
> However, I'm having a hard time pinning down what the problem might be.
> Does anyone more familiar with linker scripts than me know?
> 

The assertion in the linker script compares the symbols
syslinux_ldlinux_size (from the assembler) with __payload_len (from the
linker).  Comment out the assert and check the value of __payload_len in
syslinux.elf; if it is something other than 0x7c00 we need to find out
where it gets the value (by backtracking the component values.)

	-hpa