linux-kernel - [PATCH 07/10] x86/alternatives: Add an auxilary section

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Date:	Tue, 26 Jan 2016 22:12:07 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH 07/10] x86/alternatives: Add an auxilary section

From: Borislav Petkov <bp@...e.de>

Add .altinstr_aux for additional instructions which will be used before
and/or during patching. All stuff which needs more sophisticated
patching should go there. See next patch.

Signed-off-by: Borislav Petkov <bp@...e.de>
---
 arch/x86/kernel/vmlinux.lds.S | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 74e4bf11f562..92dc211c11db 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -195,6 +195,17 @@ SECTIONS
 	:init
 #endif
 
+	/*
+	 * Section for code used exclusively before alternatives are run. All
+	 * references to such code must be patched out by alternatives, normally
+	 * by using X86_FEATURE_ALWAYS CPU feature bit.
+	 *
+	 * See static_cpu_has() for an example.
+	 */
+	.altinstr_aux : AT(ADDR(.altinstr_aux) - LOAD_OFFSET) {
+		*(.altinstr_aux)
+	}
+
 	INIT_DATA_SECTION(16)
 
 	.x86_cpu_dev.init : AT(ADDR(.x86_cpu_dev.init) - LOAD_OFFSET) {
-- 
2.3.5