"relocation truncated"

[edmundo at rano.demon.co.uk]

As usually happens, I have some ideas of my own straight after
posting. Without actually understanding any of this, I have done some
experiments (randomly commenting out bits of assembler and seeing what
happens) and have discovered:

The "Warning: warning: missing prefix `*' in absolute indirect
address, maybe misassembled!" probably doesn't matter, but I can make
it go away by changing

	call	(%eax)

to:

	call	*(%eax)

The perhaps serious error "relocation truncated to fit" is caused by
this line:

	ljmp	$KERNEL_CS, $EXT(_SMP_TRAMP_32_ENTRY_)

I can make it go away by moving the .code32 directive to the other
side of it, i.e. replacing

	/* now go to 32-bit segment */
	ljmp	$KERNEL_CS, $EXT(_SMP_TRAMP_32_ENTRY_)

	.code32

by:

	.code32

	/* now go to 32-bit segment */
	ljmp	$KERNEL_CS, $EXT(_SMP_TRAMP_32_ENTRY_)

This change may be a good one, because the there's comment immediately
following that says:

 * [_SMP_TRAMP_32_ENTRY_ - 6] is the 32 bit address of the ljmp destination.

My empirical measurements indicate that the ljmp instruction takes
only 5 bytes in 16-bit mode, but 7 bytes in 32-bit mode.

All this in oskit/libsmp/x86/boot.S, so it may not be totally relevant
to L4 hackers ...

Edmund