linux-kernel - percpu section failure with Gold linker

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Message-ID: <alpine.LNX.2.01.1211232136380.11359@nerf07.vanv.qr>
Date:	Fri, 23 Nov 2012 21:44:02 +0100 (CET)
From:	Jan Engelhardt <jengelh@...i.de>
To:	tj@...nel.org, cl@...ux-foundation.org
cc:	linux-mm@...ck.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: percpu section failure with Gold linker

Hi,


when compiling a kernel with the gold linker (3.7.0-rc6 26d29d06ea0204, 
gcc-4.7 and binutils-2.23 in my case), certain pcpu symbols are 
seemingly errneously copied over from .o files to .ko files, leading to 
a hard warning during depmod:

	gold$ make -j8 LD=gold HOSTLD=gold
	gold$ make modules_install INSTALL_MOD_PATH=/tmp/foo
	[...]
	WARNING: /tmp/foo/lib/modules/3.7.0-rc6-jng6-default+
	/kernel/net/rds/rds_tcp.ko needs unknown symbol
	__pcpu_scope_rds_tcp_stats

This happens with many modules using percpu; looking at things with nm 
reveals:

	gold/net/ipv6$ nm ipv6.o | grep __pcpu_
	0000000000000000 D __pcpu_unique_ipv6_cookie_scratch
	gold/net/ipv6$ nm ipv6.ko | grep __pcpu_
	                 U __pcpu_unique_ipv6_cookie_scratch

On the other hand, in a linux tree built with the original ld (ld.bfd), 
things look like:

	bfd$ make -j8
	[...]
	bfd/net/ipv6$ nm ipv6.o | grep pcpu
	0000000000000000 D __pcpu_unique_ipv6_cookie_scratch
	bfd/net/ipv6$ nm ipv6.ko | grep pcpu
	(no result)
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