[PATCH v2 1/7] compiler-clang: add build check for clang 10.0.1

[Nick Desaulniers]

During Plumbers 2020, we voted to just support the latest release of
Clang for now.  Add a compile time check for this.

We plan to remove workarounds for older versions now, which will break
in subtle and not so subtle ways.

Link: https://github.com/ClangBuiltLinux/linux/issues/9
Link: https://github.com/ClangBuiltLinux/linux/issues/941
Suggested-by: Sedat Dilek <sedat.dilek@xxxxxxxxx>
Suggested-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
Suggested-by: Kees Cook <keescook@xxxxxxxxxxxx>
Acked-by: Marco Elver <elver@xxxxxxxxxx>
Acked-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
Acked-by: Sedat Dilek <sedat.dilek@xxxxxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
Reviewed-by: Miguel Ojeda <miguel.ojeda.sandonis@xxxxxxxxx>
Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
---
Changes V1 -> V2:
* use a more informational error, as per Kees.
* collect tags.

 include/linux/compiler-clang.h | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
index cee0c728d39a..230604e7f057 100644
--- a/include/linux/compiler-clang.h
+++ b/include/linux/compiler-clang.h
@@ -3,6 +3,14 @@
 #error "Please don't include <linux/compiler-clang.h> directly, include <linux/compiler.h> instead."
 #endif
 
+#define CLANG_VERSION (__clang_major__ * 10000	\
+		     + __clang_minor__ * 100	\
+		     + __clang_patchlevel__)
+
+#if CLANG_VERSION < 100001
+# error Sorry, your version of Clang is too old - please use 10.0.1 or newer.
+#endif
+
 /* Compiler specific definitions for Clang compiler */
 
 /* same as gcc, this was present in clang-2.6 so we can assume it works
-- 
2.28.0.402.g5ffc5be6b7-goog