LinuxKPI: Add static_assert() macro

And move it along BUILD_BUG family in to
linux/build_bug.h to match Linux.

Sponsored by:	Serenity Cyber Security, LLC
Reviewed by:	manu, bz
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D42800

2 files changed, 66 insertions, 22 deletions

diff --git a/sys/compat/linuxkpi/common/include/linux/build_bug.h b/sys/compat/linuxkpi/common/include/linux/build_bug.h
new file mode 100644
index 000000000000..59d1fc228afc
--- /dev/null
+++ b/sys/compat/linuxkpi/common/include/linux/build_bug.h
@@ -0,0 +1,65 @@
+/*-
+ * Copyright (c) 2017 Mark Johnston <markj@FreeBSD.org>
+ * Copyright (c) 2018 Johannes Lundberg <johalun0@gmail.com>
+ * Copyright (c) 2021 The FreeBSD Foundation
+ * Copyright (c) 2021 Vladimir Kondratyev <wulf@FreeBSD.org>
+ * Copyright (c) 2023 Serenity Cyber Security, LLC
+ *
+ * Portions of this software were developed by Bjoern A. Zeeb
+ * under sponsorship from the FreeBSD Foundation.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice unmodified, this list of conditions, and the following
+ *    disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef	_LINUXKPI_LINUX_BUILD_BUG_H_
+#define	_LINUXKPI_LINUX_BUILD_BUG_H_
+
+#include <sys/param.h>
+
+#include <linux/compiler.h>
+
+/*
+ * BUILD_BUG_ON() can happen inside functions where _Static_assert() does not
+ * seem to work.  Use old-schoold-ish CTASSERT from before commit
+ * a3085588a88fa58eb5b1eaae471999e1995a29cf but also make sure we do not
+ * end up with an unused typedef or variable. The compiler should optimise
+ * it away entirely.
+ */
+#define	_O_CTASSERT(x)		_O__CTASSERT(x, __LINE__)
+#define	_O__CTASSERT(x, y)	_O___CTASSERT(x, y)
+#define	_O___CTASSERT(x, y)	while (0) { \
+    typedef char __assert_line_ ## y[(x) ? 1 : -1]; \
+    __assert_line_ ## y _x; \
+    _x[0] = '\0'; \
+}
+
+#define	BUILD_BUG()			do { CTASSERT(0); } while (0)
+#define	BUILD_BUG_ON(x)			do { _O_CTASSERT(!(x)) } while (0)
+#define	BUILD_BUG_ON_MSG(x, msg)	BUILD_BUG_ON(x)
+#define	BUILD_BUG_ON_NOT_POWER_OF_2(x)	BUILD_BUG_ON(!powerof2(x))
+#define	BUILD_BUG_ON_INVALID(expr)	while (0) { (void)(expr); }
+#define	BUILD_BUG_ON_ZERO(x)	((int)sizeof(struct { int:-((x) != 0); }))
+
+#define static_assert(x, ...)		__static_assert(x, ##__VA_ARGS__, #x)
+#define __static_assert(x, msg, ...)	_Static_assert(x, msg)
+
+#endif
diff --git a/sys/compat/linuxkpi/common/include/linux/kernel.h b/sys/compat/linuxkpi/common/include/linux/kernel.h
index 73418c849544..097e22e5d8ea 100644
--- a/sys/compat/linuxkpi/common/include/linux/kernel.h
+++ b/sys/compat/linuxkpi/common/include/linux/kernel.h
@@ -41,6 +41,7 @@
 #include <sys/time.h>
 
 #include <linux/bitops.h>
+#include <linux/build_bug.h>
 #include <linux/compiler.h>
 #include <linux/stringify.h>
 #include <linux/errno.h>
@@ -90,28 +91,6 @@
 #define	S64_C(x) x ## LL
 #define	U64_C(x) x ## ULL
 
-/*
- * BUILD_BUG_ON() can happen inside functions where _Static_assert() does not
- * seem to work.  Use old-schoold-ish CTASSERT from before commit
- * a3085588a88fa58eb5b1eaae471999e1995a29cf but also make sure we do not
- * end up with an unused typedef or variable. The compiler should optimise
- * it away entirely.
- */
-#define	_O_CTASSERT(x)		_O__CTASSERT(x, __LINE__)
-#define	_O__CTASSERT(x, y)	_O___CTASSERT(x, y)
-#define	_O___CTASSERT(x, y)	while (0) { \
-    typedef char __unused __assert_line_ ## y[(x) ? 1 : -1]; \
-    __assert_line_ ## y _x; \
-    _x[0] = '\0'; \
-}
-
-#define	BUILD_BUG()			do { CTASSERT(0); } while (0)
-#define	BUILD_BUG_ON(x)			do { _O_CTASSERT(!(x)) } while (0)
-#define	BUILD_BUG_ON_MSG(x, msg)	BUILD_BUG_ON(x)
-#define	BUILD_BUG_ON_NOT_POWER_OF_2(x)	BUILD_BUG_ON(!powerof2(x))
-#define	BUILD_BUG_ON_INVALID(expr)	while (0) { (void)(expr); }
-#define	BUILD_BUG_ON_ZERO(x)	((int)sizeof(struct { int:-((x) != 0); }))
-
 #define	BUG()			panic("BUG at %s:%d", __FILE__, __LINE__)
 #define	BUG_ON(cond)		do {				\
 	if (cond) {						\