linux-kernel - [PATCH v5 1/3] x86: kallsyms: disable absolute percpu symbols on !SMP

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Date:	Mon,  8 Feb 2016 18:57:46 +0100
From:	Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:	linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, x86@...nel.org,
	keescook@...omium.org, akpm@...ux-foundation.org, mingo@...nel.org,
	hpa@...or.com, heiko.carstens@...ibm.com, benh@...nel.crashing.org,
	mpe@...erman.id.au, mmarek@...e.cz, rusty@...tcorp.com.au,
	arnd@...db.de, linux-arch@...r.kernel.org, linux@...ck-us.net
Cc:	Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: [PATCH v5 1/3] 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.

Tested-by: Guenter Roeck <linux@...ck-us.net>
Reviewed-by: Kees Cook <keescook@...omium.org>
Tested-by: Kees Cook <keescook@...omium.org>
Acked-by: Rusty Russell <rusty@...tcorp.com.au>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
---
 init/Kconfig            | 4 ++++
 scripts/link-vmlinux.sh | 2 +-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/init/Kconfig b/init/Kconfig
index 22320804fbaf..b17824a875fa 100644
--- a/init/Kconfig
+++ b/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
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index ba6c34ea5429..7a08bf9a9576 100755
--- a/scripts/link-vmlinux.sh
+++ b/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
 
-- 
2.5.0