From 57b51d0bdce53a928bde6c3370fcd0f06cfa0ad4 Mon Sep 17 00:00:00 2001
From: Josh Poimboeuf <jpoimboe@redhat.com>
Date: Wed, 9 Jul 2014 10:34:22 -0500
Subject: [PATCH] add KPATCH_WARN_*_LINE macros

WARN macros are problematic because they embed the line number in an
instruction.  As a result, when a function is changed higher in a file,
the line numbers for any WARN calls below that function in the file can
result in unnecessarily changed functions.

These macros allow a patch author to hard code the line numbers in WARN
macros to prevent functions from otherwise changing and getting pulled
into a patch module unnecessarily.
---
 kmod/patch/kpatch-macros.h | 40 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/kmod/patch/kpatch-macros.h b/kmod/patch/kpatch-macros.h
index 7f17965..8f31637 100644
--- a/kmod/patch/kpatch-macros.h
+++ b/kmod/patch/kpatch-macros.h
@@ -2,6 +2,7 @@
 #define __KPATCH_MACROS_H_
 
 #include <linux/compiler.h>
+#include <linux/bug.h>
 
 typedef void (*kpatch_loadcall_t)(void);
 typedef void (*kpatch_unloadcall_t)(void);
@@ -64,4 +65,43 @@ struct kpatch_unload {
 #define KPATCH_FORCE_UNSAFE(_fn) \
 	void *__kpatch_force_func_##_fn __section(.kpatch.force) = _fn;
 
+
+/*
+ * KPATCH_WARN_*_LINE macros
+ *
+ * WARN macros are problematic because they embed the line number in an
+ * instruction.  As a result, when a function is changed higher in a file, the
+ * line numbers for any WARN calls below that function in the file can result
+ * in unnecessarily changed functions.
+ *
+ * These macros allow a patch author to hard code the line numbers in WARN
+ * macros to prevent functions from otherwise changing and getting pulled into
+ * a patch module unnecessarily.
+ *
+ * TODO: consider moving these __WARN_*_line variants upstream to bug.h
+ */
+#ifndef __WARN_TAINT
+#define __WARN_line(line) warn_slowpath_null(__FILE__, line)
+#define __WARN_printf_line(line, arg...) warn_slowpath_fmt(__FILE__, line, arg)
+#define __WARN_printf_taint_line(line, taint, arg...) \
+	warn_slowpath_fmt_taint(__FILE__, line, taint, arg)
+#else
+#error __WARN_TAINT not yet supported
+#endif
+
+#define KPATCH_WARN_LINE(line, condition, format...) ({			\
+	int __ret_warn_on = !!(condition);				\
+	if (unlikely(__ret_warn_on))					\
+		 __WARN_printf_line(line, format);			\
+	unlikely(__ret_warn_on);					\
+})
+#define KPATCH_WARN_ON_LINE(line, condition) ({				\
+	int __ret_warn_on = !!(condition);				\
+	if (unlikely(__ret_warn_on))					\
+		__WARN_line(line);					\
+	unlikely(__ret_warn_on);					\
+})
+#define KPATCH_WARN_ON_SMP_LINE(line, condition) \
+	KPATCH_WARN_ON_LINE(line, condition)
+
 #endif /* __KPATCH_MACROS_H_ */