2 files changed, 38 insertions, 16 deletions

diff --git a/include/linux/bug.h b/include/linux/bug.h
index dc11dc762fc3..7f4818673c41 100644
--- a/include/linux/bug.h
+++ b/include/linux/bug.h
@@ -17,6 +17,7 @@ struct pt_regs;
 #define BUILD_BUG_ON_ZERO(e) (0)
 #define BUILD_BUG_ON_NULL(e) ((void*)0)
 #define BUILD_BUG_ON_INVALID(e) (0)
+#define BUILD_BUG_ON_MSG(cond, msg) (0)
 #define BUILD_BUG_ON(condition) (0)
 #define BUILD_BUG() (0)
 #else /* __CHECKER__ */
@@ -40,6 +41,15 @@ struct pt_regs;
 #define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e))))
 
 /**
+ * BUILD_BUG_ON_MSG - break compile if a condition is true & emit supplied
+ *                    error message.
+ * @condition: the condition which the compiler should know is false.
+ *
+ * See BUILD_BUG_ON for description.
+ */
+#define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
+
+/**
  * BUILD_BUG_ON - break compile if a condition is true.
  * @condition: the condition which the compiler should know is false.
  *
@@ -60,15 +70,8 @@ struct pt_regs;
 #ifndef __OPTIMIZE__
 #define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)]))
 #else
-#define BUILD_BUG_ON(condition)                                         \
-        do {                                                            \
-                bool __cond = !!(condition);                            \
-                extern void __build_bug_on_failed(void)                 \
-                        __compiletime_error("BUILD_BUG_ON failed");     \
-                if (__cond)                                             \
-                        __build_bug_on_failed();                        \
-                __compiletime_error_fallback(__cond);                   \
-        } while (0)
+#define BUILD_BUG_ON(condition) \
+        BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
 #endif
 
 /**
@@ -78,12 +81,7 @@ struct pt_regs;
  * build time, you should use BUILD_BUG to detect if it is
  * unexpectedly used.
  */
-#define BUILD_BUG()                                             \
-        do {                                                    \
-                extern void __build_bug_failed(void)            \
-                        __compiletime_error("BUILD_BUG failed");\
-                __build_bug_failed();                           \
-        } while (0)
+#define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
 
 #endif  /* __CHECKER__ */
 
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 423bb6bd660f..10b8f23fab0f 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -308,11 +308,35 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
 #ifndef __compiletime_error
 # define __compiletime_error(message)
 # define __compiletime_error_fallback(condition) \
-        do { ((void)sizeof(char[1 - 2*!!(condition)])); } while (0)
+        do { ((void)sizeof(char[1 - 2 * condition])); } while (0)
 #else
 # define __compiletime_error_fallback(condition) do { } while (0)
 #endif
 
+#define __compiletime_assert(condition, msg, prefix, suffix)            \
+        do {                                                            \
+                bool __cond = !(condition);                             \
+                extern void prefix ## suffix(void) __compiletime_error(msg); \
+                if (__cond)                                             \
+                        prefix ## suffix();                             \
+                __compiletime_error_fallback(__cond);                   \
+        } while (0)
+
+#define _compiletime_assert(condition, msg, prefix, suffix) \
+        __compiletime_assert(condition, msg, prefix, suffix)
+
+/**
+ * compiletime_assert - break build and emit msg if condition is false
+ * @condition: a compile-time constant condition to check
+ * @msg:       a message to emit if condition is false
+ *
+ * In tradition of POSIX assert, this macro will break the build if the
+ * supplied condition is *false*, emitting the supplied error message if the
+ * compiler has support to do so.
+ */
+#define compiletime_assert(condition, msg) \
+        _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
+
 /*
  * Prevent the compiler from merging or refetching accesses.  The compiler
  * is also forbidden from reordering successive instances of ACCESS_ONCE(),