Clang feature fixes for v5.13-rc4

- Correctly pass stack frame size checking under LTO (Nick Desaulniers)
 
 - Avoid CFI mismatches by checking initcall_t types (Marco Elver)
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Merge tag 'clang-features-v5.13-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull clang feature fixes from Kees Cook:

 - Correctly pass stack frame size checking under LTO (Nick Desaulniers)

 - Avoid CFI mismatches by checking initcall_t types (Marco Elver)

* tag 'clang-features-v5.13-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  Makefile: LTO: have linker check -Wframe-larger-than
  init: verify that function is initcall_t at compile-time

Makefile

@@ -928,6 +928,11 @@ CC_FLAGS_LTO	+= -fvisibility=hidden
 
 # Limit inlining across translation units to reduce binary size
 KBUILD_LDFLAGS += -mllvm -import-instr-limit=5
+
+# Check for frame size exceeding threshold during prolog/epilog insertion.
+ifneq ($(CONFIG_FRAME_WARN),0)
+KBUILD_LDFLAGS	+= -plugin-opt=-warn-stack-size=$(CONFIG_FRAME_WARN)
+endif
 endif
 
 ifdef CONFIG_LTO

include/linux/init.h

@@ -242,7 +242,8 @@ extern bool initcall_debug;
 	asm(".section	\"" __sec "\", \"a\"		\n"	\
 	    __stringify(__name) ":			\n"	\
 	    ".long	" __stringify(__stub) " - .	\n"	\
-	    ".previous					\n");
+	    ".previous					\n");	\
+	static_assert(__same_type(initcall_t, &fn));
 #else
 #define ____define_initcall(fn, __unused, __name, __sec)	\
 	static initcall_t __name __used 			\