[PATCH v3 3/5] x86/asm: Error out if asm/jump_label.h is included inappropriately

Andy Lutomirski
2015-11-12T21:00:01Z

Rather than potentially generating incorrect code on a
non-HAVE_JUMP_LABEL kernel if someone includes asm/jump_label.h,
error out.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
arch/x86/include/asm/jump_label.h | 13 +++++++++++++
1 file changed, 13 insertions(+)

diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h
index 5daeca3d0f9e..96872dc96597 100644
--- a/arch/x86/include/asm/jump_label.h
+++ b/arch/x86/include/asm/jump_label.h
@@ -1,6 +1,19 @@
#ifndef _ASM_X86_JUMP_LABEL_H
#define _ASM_X86_JUMP_LABEL_H

+#ifndef HAVE_JUMP_LABEL
+/*
+ * For better or for worse, if jump labels (the gcc extension) are missing,
+ * then the entire static branch patching infrastructure is compiled out.
+ * If that happens, the code in here will malfunction. Raise a compiler
+ * error instead.
+ *
+ * In theory, jump labels and the static branch patching infrastructure
+ * could be decoupled to fix this.
+ */
+#error asm/jump_label.h included on a non-jump-label kernel
+#endif
+
#ifndef __ASSEMBLY__

#include <linux/stringify.h>
--
2.5.0