Merge branch '2021-07-01-buildtime-gd-sanity-check' into next

- Merge build-time sanity checks to ensure the size of gd doesn't
  change.  This can happen during cleanups due to not all symbols being
  implemented in Kconfig.

include/asm-generic/global_data.h

@@ -23,6 +23,8 @@
 #include <fdtdec.h>
 #include <membuff.h>
 #include <linux/list.h>
+#include <linux/build_bug.h>
+#include <asm-offsets.h>
 
 struct acpi_ctx;
 struct driver_rt;
@@ -464,6 +466,9 @@ struct global_data {
 	char *smbios_version;
 #endif
 };
+#ifndef DO_DEPS_ONLY
+static_assert(sizeof(struct global_data) == GD_SIZE);
+#endif
 
 /**
  * gd_board_type() - retrieve board type

include/linux/build_bug.h

@@ -79,6 +79,25 @@
  */
 #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
 
+/**
+ * static_assert - check integer constant expression at build time
+ *
+ * static_assert() is a wrapper for the C11 _Static_assert, with a
+ * little macro magic to make the message optional (defaulting to the
+ * stringification of the tested expression).
+ *
+ * Contrary to BUILD_BUG_ON(), static_assert() can be used at global
+ * scope, but requires the expression to be an integer constant
+ * expression (i.e., it is not enough that __builtin_constant_p() is
+ * true for expr).
+ *
+ * Also note that BUILD_BUG_ON() fails the build if the condition is
+ * true, while static_assert() fails the build if the expression is
+ * false.
+ */
+#define static_assert(expr, ...) __static_assert(expr, ##__VA_ARGS__, #expr)
+#define __static_assert(expr, msg, ...) _Static_assert(expr, msg)
+
 #endif	/* __CHECKER__ */
 
 #endif	/* _LINUX_BUILD_BUG_H */