[PATCH v19 02/10] objtool: Add STACK_FRAME_NON_STANDARD macro

From	Josh Poimboeuf <jpoimboe@redhat.com>
Newsgroups	linux.kernel
Subject	[PATCH v19 02/10] objtool: Add STACK_FRAME_NON_STANDARD macro
Date	2016-02-29 05:30 +0100
Message-ID	<r7nD4-5hw-9@gated-at.bofh.it> (permalink)
References	<r7nD4-5hw-5@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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Add a new macro, STACK_FRAME_NON_STANDARD, which is used to denote a
function which does something unusual related to its stack frame.  Use
of the macro prevents objtool from emitting a false positive warning.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
 arch/x86/kernel/vmlinux.lds.S |  5 ++++-
 include/linux/frame.h         | 23 +++++++++++++++++++++++
 2 files changed, 27 insertions(+), 1 deletion(-)
 create mode 100644 include/linux/frame.h

diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 92dc211..13fa0ad 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)
+		*(__func_stack_frame_non_standard)
+	}
 }
 
 
diff --git a/include/linux/frame.h b/include/linux/frame.h
new file mode 100644
index 0000000..e6baaba
--- /dev/null
+++ b/include/linux/frame.h
@@ -0,0 +1,23 @@
+#ifndef _LINUX_FRAME_H
+#define _LINUX_FRAME_H
+
+#ifdef CONFIG_STACK_VALIDATION
+/*
+ * This macro marks the given function's stack frame as "non-standard", which
+ * 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(__func_stack_frame_non_standard) \
+		*__func_stack_frame_non_standard_##func = func
+
+#else /* !CONFIG_STACK_VALIDATION */
+
+#define STACK_FRAME_NON_STANDARD(func)
+
+#endif /* CONFIG_STACK_VALIDATION */
+
+#endif /* _LINUX_FRAME_H */
-- 
2.4.3

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[PATCH v19 02/10] objtool: Add STACK_FRAME_NON_STANDARD macro Josh Poimboeuf <jpoimboe@redhat.com> - 2016-02-29 05:30 +0100
  [tip:core/objtool] objtool: Add STACK_FRAME_NON_STANDARD() macro tip-bot for Josh Poimboeuf <tipbot@zytor.com> - 2016-02-29 12:10 +0100

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