[PATCH v11 05/20] x86/stackvalidate: Add ignore macros

[Josh Poimboeuf <jpoimboe@redhat.com>]

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@redhat.com>
---
 arch/x86/include/asm/stackvalidate.h | 45 ++++++++++++++++++++++++++++++++++++
 arch/x86/kernel/vmlinux.lds.S        |  5 +++-
 include/linux/stackvalidate.h        | 28 ++++++++++++++++++++++
 3 files changed, 77 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..95db052
--- /dev/null
+++ b/arch/x86/include/asm/stackvalidate.h
@@ -0,0 +1,45 @@
+#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
+#ifdef CONFIG_STACK_VALIDATION
+	.Lstackvalidate_ignore_\@:
+	.pushsection __stackvalidate_ignore_insn, "a"
+	_ASM_ALIGN
+	.long .Lstackvalidate_ignore_\@ - .
+	.popsection
+#endif
+.endm
+
+#else /* !__ASSEMBLY__ */
+
+#ifdef CONFIG_STACK_VALIDATION
+
+#define STACKVALIDATE_IGNORE_INSN				\
+	"1:\n"							\
+	".pushsection __stackvalidate_ignore_insn, \"a\"\n"	\
+	_ASM_ALIGN "\n"						\
+	".long 1b - .\n"					\
+	".popsection\n"
+
+#else /* !CONFIG_STACK_VALIDATION */
+
+#define STACKVALIDATE_IGNORE_INSN ""
+
+#endif /* CONFIG_STACK_VALIDATION */
+
+#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..4ae242c
--- /dev/null
+++ b/include/linux/stackvalidate.h
@@ -0,0 +1,28 @@
+#ifndef _LINUX_STACKVALIDATE_H
+#define _LINUX_STACKVALIDATE_H
+
+#include <asm/stackvalidate.h>
+
+#ifndef __ASSEMBLY__
+
+#ifdef CONFIG_STACK_VALIDATION
+/*
+ * 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
+
+#else /* !CONFIG_STACK_VALIDATION */
+
+#define STACKVALIDATE_IGNORE_FUNC(_func)
+
+#endif /* CONFIG_STACK_VALIDATION */
+
+#endif /* !__ASSEMBLY__ */
+
+#endif /* _LINUX_STACKVALIDATE_H */
-- 
2.4.3