[PATCH] x86: Work around gcc 4.2 over aggressive optimizer

The new PDA code uses a dummy _proxy_pda variable to describe
memory references to the PDA. It is never referenced
in inline assembly, but exists as input/output arguments.
gcc 4.2 in some cases can CSE references to this which causes
unresolved symbols.  Define it to zero to avoid this.

Signed-off-by: Andi Kleen <ak@suse.de>

arch/i386/kernel/vmlinux.lds.S

@@ -26,6 +26,7 @@ OUTPUT_FORMAT("elf32-i386", "elf32-i386", "elf32-i386")
 OUTPUT_ARCH(i386)
 ENTRY(phys_startup_32)
 jiffies = jiffies_64;
+_proxy_pda = 0;
 
 PHDRS {
 	text PT_LOAD FLAGS(5);	/* R_E */

arch/x86_64/kernel/vmlinux.lds.S

@@ -13,6 +13,7 @@ OUTPUT_FORMAT("elf64-x86-64", "elf64-x86-64", "elf64-x86-64")
 OUTPUT_ARCH(i386:x86-64)
 ENTRY(phys_startup_64)
 jiffies_64 = jiffies;
+_proxy_pda = 0;
 PHDRS {
 	text PT_LOAD FLAGS(5);	/* R_E */
 	data PT_LOAD FLAGS(7);	/* RWE */