Re: [PATCH 4/4 v5] fortify: Add Clang support

On Wed, Feb 02, 2022 at 01:22:09PM -0800, Nick Desaulniers wrote:

On Tue, Feb 1, 2022 at 4:30 PM Kees Cook [off-list ref] wrote:

quoted

--- a/security/Kconfig
+++ b/security/Kconfig

@@ -179,7 +179,7 @@ config FORTIFY_SOURCE
        depends on ARCH_HAS_FORTIFY_SOURCE
        # https://bugs.llvm.org/show_bug.cgi?id=50322
        # https://bugs.llvm.org/show_bug.cgi?id=41459
-       depends on !CC_IS_CLANG
+       depends on !CC_IS_CLANG || CLANG_VERSION >= 130000

Are these comments still relevant, and is the clang version still correct?

Oh, good call. I thought the version was still correct (more below),
but yes, the comments need adjusting.

In https://lore.kernel.org/llvm/CANiq72n1d7ouKNi+pbsy7chsg0DfCXxez27qqtS9XE1n3m5=8Q@mail.gmail.com/ (local)
Miguel notes that diagnose_as only exists in clang-14+.  If this
series relies on diagnose_as, then should this version check be for
clang-14+ rather than clang-13+?

It doesn't rely on it; this is just taking advantage of an improvement.

https://bugs.llvm.org/show_bug.cgi?id=50322 is still open, but doesn't
signify why there's a version check. It makes sense if there's no
version check, but I'm not sure it's still relevant to this Kconfig
option after your series.

With __overloadable, this probably ended up going away.

https://bugs.llvm.org/show_bug.cgi?id=41459 was fixed in clang-13, but
it was also backported to the clang 12.0.1 release.  Is it still
relevant if we're gated on diagnose_as from clang-14?

Ah-ha! I missed that this got backported. Looks like 12.0.1 and later
have this fixed. That's excellent!

Perhaps a single comment, about the diagnose_as attribute or a link to
https://reviews.llvm.org/rGbc5f2d12cadce765620efc56a1ca815221db47af or
whatever, and updating the version check to be against clang-14 would
be more precise?

Yup, I will rework this after double-checking 12.0.1 builds.

Thanks!

-- 
Kees Cook