linux-kernel - [tip:x86/asm] x86/asm: Error out if asm/ jump

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Date:	Tue, 24 Nov 2015 01:35:58 -0800
From:	tip-bot for Andy Lutomirski <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	tglx@...utronix.de, torvalds@...ux-foundation.org,
	fweisbec@...il.com, hpa@...or.com, dvlasenk@...hat.com,
	peterz@...radead.org, luto@...nel.org, brgerst@...il.com,
	mingo@...nel.org, linux-kernel@...r.kernel.org,
	luto@...capital.net, bp@...en8.de
Subject: [tip:x86/asm] x86/asm: Error out if asm/
 jump_label.h is included inappropriately

Commit-ID:  c28454332fe0b65e22c3a2717e5bf05b5b47ca20
Gitweb:     http://git.kernel.org/tip/c28454332fe0b65e22c3a2717e5bf05b5b47ca20
Author:     Andy Lutomirski <luto@...nel.org>
AuthorDate: Thu, 12 Nov 2015 12:59:02 -0800
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 24 Nov 2015 09:56:43 +0100

x86/asm: Error out if asm/jump_label.h is included inappropriately

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@...nel.org>
Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Link: http://lkml.kernel.org/r/99407f0ac7fa3ab03a3d31ce076d47b5c2f44795.1447361906.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@...nel.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 5daeca3..96872dc 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>
--
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