Re: [PATCH] [POWERPC] Fix link errors for allyesconfig

[David Miller <davem@davemloft.net>]

From: Stephen Rothwell <sfr@canb.auug.org.au>
Date: Sun, 4 Nov 2007 13:28:39 +1100

> Dave, would something like this help as an alternative to the .fixup
> change you committed recently?

I tried it, doesn't help:

kernel/built-in.o: In function `context_switch':
/home/davem/src/GIT/sparc-2.6/kernel/sched.c:1950: relocation truncated to fit: R_SPARC_WDISP22 against symbol `ret_from_syscall' defined in .text section in arch/sparc64/kernel/head.o
drivers/built-in.o:(.fixup+0x0): relocation truncated to fit: R_SPARC_WDISP22 against `.text'
drivers/built-in.o:(.fixup+0x8): relocation truncated to fit: R_SPARC_WDISP22 against `.text'
drivers/built-in.o:(.fixup+0x10): relocation truncated to fit: R_SPARC_WDISP22 against `.text'
drivers/built-in.o:(.fixup+0x18): relocation truncated to fit: R_SPARC_WDISP22 against `.text'
drivers/built-in.o:(.fixup+0x20): relocation truncated to fit: R_SPARC_WDISP22 against `.text'
drivers/built-in.o:(.fixup+0x2c): relocation truncated to fit: R_SPARC_WDISP22 against `.text'
drivers/built-in.o:(.fixup+0x38): relocation truncated to fit: R_SPARC_WDISP22 against `.text'
drivers/built-in.o:(.fixup+0x44): relocation truncated to fit: R_SPARC_WDISP22 against `.text'
drivers/built-in.o:(.fixup+0x50): relocation truncated to fit: R_SPARC_WDISP22 against `.text'
drivers/built-in.o:(.fixup+0x5c): additional relocation overflows omitted from the output
make: *** [.tmp_vmlinux1] Error 1

drivers/built-in.o itself has a 16MB+ .text section which is
beyond the 22-bit signed branch displacement we have available.

There has to be a nicer way to do this.  In fact I think I
just figured out one such technique.

The whole reason we need these .fixup sections is to encode
a move of -EFAULT into some register, and a control transfer.

Every kernel text address, even for modules, is in the low 32-bits on
sparc64.  So we can encode this more simply, perhaps even with one
32-bit word for each entry.

I can probably encode it all in the __ex_table entries in fact,
and I'll give that a shot.