linux-kernel - [PATCH] alpha: link failure fix

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Date:	Sat, 21 Jun 2008 03:26:21 +0400
From:	Ivan Kokshaysky <ink@...assic.park.msu.ru>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Richard Henderson <rth@...ddle.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] alpha: link failure fix

With built-in scsi disk driver, the final link fails with a following
error:
`.exit.text' referenced in section `.rodata' of drivers/built-in.o:
defined in discarded section `.exit.text' of drivers/built-in.o

This happens with -Os (CONFIG_CC_OPTIMIZE_FOR_SIZE=y) with all gcc-4
versions, and also with -O2 and gcc-4.3.

The problem is in sd.c:sd_major() being inlined into __exit function
exit_sd(), and the compiler generating a jump table in .rodata section
for the 'switch' statement in sd_major(). So we have references to
discarded section.

Fixed with a big hammer in the form of -fno-jump-tables.

Note that jump tables vs. discarded sections is a generic problem,
other architectures are just lucky not to suffer from it. But with
a slightly more complex switch/case statement it can be reproduced
on x86 as well. So maybe at some point we should consider
-fno-jump-tables as a generic compile option...

Signed-off-by: Ivan Kokshaysky <ink@...assic.park.msu.ru>
---
 arch/alpha/Makefile |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/arch/alpha/Makefile b/arch/alpha/Makefile
index 4e1a8e2..4759fe7 100644
--- a/arch/alpha/Makefile
+++ b/arch/alpha/Makefile
@@ -13,6 +13,7 @@ NM := $(NM) -B
 LDFLAGS_vmlinux	:= -static -N #-relax
 CHECKFLAGS	+= -D__alpha__ -m64
 cflags-y	:= -pipe -mno-fp-regs -ffixed-8 -msmall-data
+cflags-y	+= $(call cc-option, -fno-jump-tables)
 
 cpuflags-$(CONFIG_ALPHA_EV4)		:= -mcpu=ev4
 cpuflags-$(CONFIG_ALPHA_EV5)		:= -mcpu=ev5
--
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