x86: kallsyms: disable absolute percpu symbols on !SMP

scripts/kallsyms.c has a special --absolute-percpu command line option
which deals with the zero based per cpu offsets that are used when
building for SMP on x86_64.  This means that the option should only be
passed in that case, so add a Kconfig symbol with the correct predicate,
and use that instead.
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: NGuenter Roeck <linux@roeck-us.net>
Reviewed-by: NKees Cook <keescook@chromium.org>
Tested-by: NKees Cook <keescook@chromium.org>
Acked-by: NRusty Russell <rusty@rustcorp.com.au>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Michal Marek <mmarek@suse.cz>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

init/Kconfig

@@ -1420,6 +1420,10 @@ config KALLSYMS_ALL
 
 	   Say N unless you really need all symbols.
 
+config KALLSYMS_ABSOLUTE_PERCPU
+	bool
+	default X86_64 && SMP
+
 config PRINTK
 	default y
 	bool "Enable support for printk" if EXPERT

scripts/link-vmlinux.sh

@@ -86,7 +86,7 @@ kallsyms()
 		kallsymopt="${kallsymopt} --page-offset=$CONFIG_PAGE_OFFSET"
 	fi
 
-	if [ -n "${CONFIG_X86_64}" ]; then
+	if [ -n "${CONFIG_KALLSYMS_ABSOLUTE_PERCPU}" ]; then
 		kallsymopt="${kallsymopt} --absolute-percpu"
 	fi