x86-64: Pad vDSO to a page boundary

This avoids an information leak to userspace.
Signed-off-by: NAndy Lutomirski <luto@mit.edu>
Link: http://lkml.kernel.org/r/a63380a3c58a0506a2f5a18ba1b12dbde1f25e58.1312378163.git.luto@mit.eduSigned-off-by: NH. Peter Anvin <hpa@linux.intel.com>

arch/x86/vdso/vdso.S

@@ -9,6 +9,7 @@ __PAGE_ALIGNED_DATA
 vdso_start:
 	.incbin "arch/x86/vdso/vdso.so"
 vdso_end:
+	.align PAGE_SIZE /* extra data here leaks to userspace. */
 
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