x86: Make relocatable kernel work with new binutils

The CONFIG_RELOCATABLE=y option is broken with new binutils, which will make
boot panic.

According to Lu Hongjiu, the affected binutils are from 2.20.51.0.12 to
2.21.51.0.3, which are release since Oct 22 this year. At least ubuntu 10.10 is
using such binutils. See:

http://sourceware.org/bugzilla/show_bug.cgi?id=12327

The reason of the boot panic is that we have 'jiffies = jiffies_64;' in
vmlinux.lds.S. The jiffies isn't in any section. In kernel build, there is
warning saying jiffies is an absolute address and can't be relocatable. At
runtime, jiffies will have virtual address 0.

Signed-off-by: Shaohua Li<[e-mail]>
Cc: Lu Hongjiu<[e-mail]>
Cc: Huang Ying <[e-mail]>
Cc: Sam Ravnborg <[e-mail]>
LKML-Reference: <1295312269.1949.725.camel@sli10-conroe>
Signed-off-by: Ingo Molnar <[e-mail]>

arch/x86/kernel/vmlinux.lds.S

···
 #ifdef CONFIG_X86_32
 OUTPUT_ARCH(i386)
 ENTRY(phys_startup_32)
-jiffies = jiffies_64;
 #else
 OUTPUT_ARCH(i386:x86-64)
 ENTRY(phys_startup_64)
-jiffies_64 = jiffies;
 #endif
 
 #if defined(CONFIG_X86_64) && defined(CONFIG_DEBUG_RODATA)
···
 		CACHELINE_ALIGNED_DATA(L1_CACHE_BYTES)
 
 		DATA_DATA
+		/*
+		 * Workaround a binutils (2.20.51.0.12 to 2.21.51.0.3) bug.
+		 * This makes jiffies relocatable in such binutils
+		 */
+#ifdef CONFIG_X86_32
+		jiffies = jiffies_64;
+#else
+		jiffies_64 = jiffies;
+#endif
 		CONSTRUCTORS
 
 		/* rarely changed data like cpu maps */