[PATCH 4.19 021/346] kbuild: avoid static_assert for genksyms

[Greg Kroah-Hartman]

From: Arnd Bergmann <arnd@xxxxxxxx>

commit 14dc3983b5dff513a90bd5a8cc90acaf7867c3d0 upstream.

genksyms does not know or care about the _Static_assert() built-in, and
sometimes falls back to ignoring the later symbols, which causes
undefined behavior such as

  WARNING: modpost: EXPORT symbol "ethtool_set_ethtool_phy_ops" [vmlinux] version generation failed, symbol will not be versioned.
  ld: net/ethtool/common.o: relocation R_AARCH64_ABS32 against `__crc_ethtool_set_ethtool_phy_ops' can not be used when making a shared object
  net/ethtool/common.o:(_ftrace_annotated_branch+0x0): dangerous relocation: unsupported relocation

Redefine static_assert for genksyms to avoid that.

Link: https://lkml.kernel.org/r/20201203230955.1482058-1-arnd@xxxxxxxxxx
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
Suggested-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
Cc: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Cc: Michal Marek <michal.lkml@xxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Rikard Falkeborn <rikard.falkeborn@xxxxxxxxx>
Cc: Marco Elver <elver@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 include/linux/build_bug.h |    5 +++++
 1 file changed, 5 insertions(+)

--- a/include/linux/build_bug.h
+++ b/include/linux/build_bug.h
@@ -80,4 +80,9 @@
 
 #endif	/* __CHECKER__ */
 
+#ifdef __GENKSYMS__
+/* genksyms gets confused by _Static_assert */
+#define _Static_assert(expr, ...)
+#endif
+
 #endif	/* _LINUX_BUILD_BUG_H */