From: Nathan Chancellor <nathan@kernel.org>
To: Kees Cook <kees@kernel.org>,
	 Nick Desaulniers <nick.desaulniers+lkml@gmail.com>,
	 Bill Wendling <morbo@google.com>,
	Justin Stitt <justinstitt@google.com>
Cc: linux-hardening@vger.kernel.org, llvm@lists.linux.dev,
	 patches@lists.linux.dev, Nathan Chancellor <nathan@kernel.org>
Subject: [PATCH] init/Kconfig: Require a release version of clang-22 for CC_HAS_COUNTED_BY_PTR
Date: Wed, 18 Mar 2026 17:20:18 -0700	[thread overview]
Message-ID: <20260318-counted_by_ptr-release-clang-22-v1-1-e017da246df0@kernel.org> (raw)

Commit 150a04d817d8 ("compiler_types.h: Attributes: Add __counted_by_ptr
macro") used Clang 22.0.0 as a minimum supported version for
__counted_by_ptr, which made sense while 22.0.0 was the version of
LLVM's main branch to allow developers to easily test and develop uses
of __counted_by_ptr in their code. However, __counted_by_ptr requires a
change [1] merged towards the end of the 22 development cycle to avoid
errors when applied to void pointers.

  In file included from fs/xfs/xfs_attr_inactive.c:18:
  fs/xfs/libxfs/xfs_attr.h:59:2: error: 'counted_by' cannot be applied to a pointer with pointee of unknown size because 'void' is an incomplete type
     59 |         void                    *buffer __counted_by_ptr(bufsize);
        |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This is disruptive for deployed prerelease clang-22 builds (such as
Android LLVM) or when bisecting between llvmorg-21-init and the fix.

Require a released version of clang-22 (i.e., 21.1.0 or newer) to
enabled __counted_by_ptr to ensure all fixes needed for proper support
are present.

Fixes: 150a04d817d8 ("compiler_types.h: Attributes: Add __counted_by_ptr macro")
Link: https://github.com/llvm/llvm-project/commit/f29955a594aedf5943d492a999b83e8c6b8fafae [1]
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
 init/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/init/Kconfig b/init/Kconfig
index 444ce811ea67..7484cd703bc1 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -146,7 +146,7 @@ config CC_HAS_COUNTED_BY
 config CC_HAS_COUNTED_BY_PTR
 	bool
 	# supported since clang 22
-	default y if CC_IS_CLANG && CLANG_VERSION >= 220000
+	default y if CC_IS_CLANG && CLANG_VERSION >= 220100
 	# supported since gcc 16.0.0
 	default y if CC_IS_GCC && GCC_VERSION >= 160000
 

---
base-commit: f338e77383789c0cae23ca3d48adcc5e9e137e3c
change-id: 20260318-counted_by_ptr-release-clang-22-7c9bced0db2f

Best regards,
--  
Nathan Chancellor <nathan@kernel.org>

next             reply	other threads:[~2026-03-19  0:20 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-03-19  0:20 Nathan Chancellor [this message]
2026-03-20 18:52 ` [PATCH] init/Kconfig: Require a release version of clang-22 for CC_HAS_COUNTED_BY_PTR Kees Cook

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