[PATCH v17 4/9] x86/objtool: Add STACK_FRAME_NON_STANDARD macro

[Josh Poimboeuf]

Add a new objtool ignore macro, STACK_FRAME_NON_STANDARD, which can be
used to tell objtool to skip validation of a function.

Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
---
 MAINTAINERS                   |  1 +
 arch/x86/kernel/vmlinux.lds.S |  5 ++++-
 include/linux/objtool.h       | 22 ++++++++++++++++++++++
 3 files changed, 27 insertions(+), 1 deletion(-)
 create mode 100644 include/linux/objtool.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 7c7cebd..43a940e 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7782,6 +7782,7 @@ OBJTOOL
 M:	Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
 S:	Supported
 F:	tools/objtool/
+F:	include/linux/objtool.h
 
 OMAP SUPPORT
 M:	Tony Lindgren <tony@xxxxxxxxxxx>
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 92dc211..6038fe0 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -343,7 +343,10 @@ SECTIONS
 
 	/* Sections to be discarded */
 	DISCARDS
-	/DISCARD/ : { *(.eh_frame) }
+	/DISCARD/ : {
+		*(.eh_frame)
+		*(__objtool_ignore_*)
+	}
 }
 
 
diff --git a/include/linux/objtool.h b/include/linux/objtool.h
new file mode 100644
index 0000000..cce9d67
--- /dev/null
+++ b/include/linux/objtool.h
@@ -0,0 +1,22 @@
+#ifndef _LINUX_OBJTOOL_H
+#define _LINUX_OBJTOOL_H
+
+#ifdef CONFIG_STACK_VALIDATION
+/*
+ * This C macro tells objtool to ignore the function when doing stack metadata
+ * validation.  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 tools/objtool/Documentation/stack-validation.txt.
+ */
+#define STACK_FRAME_NON_STANDARD(_func) \
+	static void __used __section(__objtool_ignore_func) \
+		*__objtool_ignore_func_##_func = _func
+
+#else /* !CONFIG_STACK_VALIDATION */
+
+#define STACK_FRAME_NON_STANDARD(_func)
+
+#endif /* CONFIG_STACK_VALIDATION */
+
+#endif /* _LINUX_OBJTOOL_H */
-- 
2.4.3