linux-kernel - [PATCH v7 4/4] x86/stackvalidate: Add ignore macros

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Message-Id: <48aedf5bfc18c757c1c5150a81d8eb450bf36f78.1436893563.git.jpoimboe@redhat.com>
Date:	Tue, 14 Jul 2015 12:14:10 -0500
From:	Josh Poimboeuf <jpoimboe@...hat.com>
To:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>
Cc:	Michal Marek <mmarek@...e.cz>,
	Peter Zijlstra <peterz@...radead.org>,
	Andy Lutomirski <luto@...nel.org>,
	Borislav Petkov <bp@...en8.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>,
	Pedro Alves <palves@...hat.com>, x86@...nel.org,
	live-patching@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v7 4/4] x86/stackvalidate: Add ignore macros

Add new stackvalidate ignore macros: STACKVALIDATE_IGNORE_INSN and
STACKVALIDATE_IGNORE_FUNC.  These can be used to tell stackvalidate to
skip validation of an instruction or a function, respectively.

Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
---
 arch/x86/include/asm/stackvalidate.h | 28 ++++++++++++++++++++++++++++
 arch/x86/kernel/vmlinux.lds.S        |  5 ++++-
 include/linux/stackvalidate.h        | 21 +++++++++++++++++++++
 3 files changed, 53 insertions(+), 1 deletion(-)
 create mode 100644 arch/x86/include/asm/stackvalidate.h
 create mode 100644 include/linux/stackvalidate.h

diff --git a/arch/x86/include/asm/stackvalidate.h b/arch/x86/include/asm/stackvalidate.h
new file mode 100644
index 0000000..2d23c23
--- /dev/null
+++ b/arch/x86/include/asm/stackvalidate.h
@@ -0,0 +1,28 @@
+#ifndef _ASM_X86_STACKVALIDATE_H
+#define _ASM_X86_STACKVALIDATE_H
+
+#include <asm/asm.h>
+
+#ifdef __ASSEMBLY__
+
+/*
+ * This asm macro tells the stack validation script to ignore the instruction
+ * immediately after the macro.  It should only be used in special cases where
+ * you're 100% sure it won't affect the reliability of frame pointers and
+ * kernel stack traces.
+ *
+ * For more information, see Documentation/stack-validation.txt.
+ */
+.macro STACKVALIDATE_IGNORE_INSN
+	.if CONFIG_STACK_VALIDATION
+		.Ltemp_\@:
+		.pushsection __stackvalidate_ignore_insn, "a"
+		_ASM_ALIGN
+		.long .Ltemp_\@ - .
+		.popsection
+	.endif
+.endm
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* _ASM_X86_STACKVALIDATE_H */
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 00bf300..f2f8d7a 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -332,7 +332,10 @@ SECTIONS
 
 	/* Sections to be discarded */
 	DISCARDS
-	/DISCARD/ : { *(.eh_frame) }
+	/DISCARD/ : {
+		*(.eh_frame)
+		*(__stackvalidate_ignore_*)
+	}
 }
 
 
diff --git a/include/linux/stackvalidate.h b/include/linux/stackvalidate.h
new file mode 100644
index 0000000..5cc5c97
--- /dev/null
+++ b/include/linux/stackvalidate.h
@@ -0,0 +1,21 @@
+#ifndef _LINUX_STACKVALIDATE_H
+#define _LINUX_STACKVALIDATE_H
+
+#include <asm/stackvalidate.h>
+
+#ifndef __ASSEMBLY__
+
+/*
+ * This C macro tells the stack validation script to ignore the function.  It
+ * should only be used in special cases where you're 100% sure it won't affect
+ * the reliability of frame pointers and kernel stack traces.
+ *
+ * For more information, see Documentation/stack-validation.txt.
+ */
+#define STACKVALIDATE_IGNORE_FUNC(_func) \
+	static void __used __section(__stackvalidate_ignore_func) \
+		*__stackvalidate_ignore_func_##_func = _func
+
+#endif /* !__ASSEMBLY__ */
+
+#endif /* _LINUX_STACKVALIDATE_H */
-- 
2.1.0

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