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compiler_types.h: Attributes: Add __counted_by_ptr macro

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Introduce __counted_by_ptr(), which works like __counted_by(), but for
pointer struct members.

struct foo {
	int a, b, c;
	char *buffer __counted_by_ptr(bytes);
	short nr_bars;
	struct bar *bars __counted_by_ptr(nr_bars);
	size_t bytes;
};

Because "counted_by" can only be applied to pointer members in very
recent compiler versions, its application ends up needing to be distinct
from flexibe array "counted_by" annotations, hence a separate macro.

This is a reworking of Kees' previous patch [1].

Link: https://lore.kernel.org/all/20251020220118.1226740-1-kees@kernel.org/ [1]
Co-developed-by: Kees Cook <kees@kernel.org>
Signed-off-by: Bill Wendling <morbo@google.com>
Link: https://patch.msgid.link/20260116005838.2419118-1-morbo@google.com
Signed-off-by: Kees Cook <kees@kernel.org>
This commit is contained in:
Bill Wendling 2026-01-16 00:57:57 +00:00 • committed by Kees Cook
parent 9f54ab83cb
commit 150a04d817
4 changed files with 34 additions and 1 deletions
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6
Makefile
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@ -952,6 +952,12 @@ KBUILD_CFLAGS += $(CC_AUTO_VAR_INIT_ZERO_ENABLER)
endif
endif
ifdef CONFIG_CC_IS_CLANG
ifdef CONFIG_CC_HAS_COUNTED_BY_PTR
KBUILD_CFLAGS += -fexperimental-late-parse-attributes
endif
endif
# Explicitly clear padding bits during variable initialization
KBUILD_CFLAGS += $(call cc-option,-fzero-init-padding-bits=all)