archives/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-03-08 01:04:41 +01:00
Code Issues Projects Releases Packages Wiki Activity Actions

compiler_types.h: Attributes: Add __counted_by_ptr macro

Browse source 
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
Download patch file Download diff file Expand all files Collapse all files

6
Makefile
View file

@ -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)

18
include/linux/compiler_types.h
View file

@ -369,7 +369,7 @@ struct ftrace_likely_data {
* Optional: only supported since clang >= 18
*
* gcc: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108896
* clang: https://github.com/llvm/llvm-project/pull/76348
* clang: https://clang.llvm.org/docs/AttributeReference.html#counted-by-counted-by-or-null-sized-by-sized-by-or-null
*
* __bdos on clang < 19.1.2 can erroneously return 0:
* https://github.com/llvm/llvm-project/pull/110497
@ -383,6 +383,22 @@ struct ftrace_likely_data {
# define __counted_by(member)
#endif
/*
* Runtime track number of objects pointed to by a pointer member for use by
* CONFIG_FORTIFY_SOURCE and CONFIG_UBSAN_BOUNDS.
*
* Optional: only supported since gcc >= 16
* Optional: only supported since clang >= 22
*
* gcc: https://gcc.gnu.org/pipermail/gcc-patches/2025-April/681727.html
* clang: https://clang.llvm.org/docs/AttributeReference.html#counted-by-counted-by-or-null-sized-by-sized-by-or-null
*/
#ifdef CONFIG_CC_HAS_COUNTED_BY_PTR
#define __counted_by_ptr(member) __attribute__((__counted_by__(member)))
#else
#define __counted_by_ptr(member)
#endif
/*
* Optional: only supported since gcc >= 15
* Optional: not supported by Clang

4
include/uapi/linux/stddef.h
View file

@ -72,6 +72,10 @@
#define __counted_by_be(m)
#endif
#ifndef __counted_by_ptr
#define __counted_by_ptr(m)
#endif
#ifdef __KERNEL__
#define __kernel_nonstring __nonstring
#else

7
init/Kconfig
View file

@ -143,6 +143,13 @@ config CC_HAS_COUNTED_BY
# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108896
default y if CC_IS_GCC && GCC_VERSION >= 150100
config CC_HAS_COUNTED_BY_PTR
bool
# supported since clang 22
default y if CC_IS_CLANG && CLANG_VERSION >= 220000
# supported since gcc 16.0.0
default y if CC_IS_GCC && GCC_VERSION >= 160000
config CC_HAS_MULTIDIMENSIONAL_NONSTRING
def_bool $(success,echo 'char tag[][4] __attribute__((__nonstring__)) = { };' | $(CC) $(CLANG_FLAGS) -x c - -c -o /dev/null -Werror)