x86: Provide _sdata in the vmlinux.lds.S file

_sdata is a common symbol defined by many architectures and made
available to the kernel via asm-generic/sections.h. Kmemleak uses this
symbol when scanning the data sections.

[ Impact: add new global symbol ]
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>
LKML-Reference: <20090511122105.26556.96593.stgit@pc1117.cambridge.arm.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/kernel/vmlinux.lds.S

@@ -108,6 +108,8 @@ SECTIONS
 	/* Data */
 	. = ALIGN(PAGE_SIZE);
 	.data : AT(ADDR(.data) - LOAD_OFFSET) {
+		/* Start of data section */
+		_sdata = .;
 		DATA_DATA
 		CONSTRUCTORS