Clang and GCC are expanding the '__counted_by' attribute to support pointers in structs. Clang has support for it since version 21. This requires defining a separate macro, '__counted_by_ptr', because, while the attribute has the same name for both a pointer and a flexible array member, minimal compiler versions need to catch up.
The effect of this feature is the same as for __counted_by on flexible array members. It provides hardening the ability to perform run-time bounds checking on otherwise unknown-size pointers. Cc: Kees Cook <[email protected]> Cc: "Gustavo A. R. Silva" <[email protected]> Cc: Nathan Chancellor <[email protected]> Cc: Nick Desaulniers <[email protected]> Cc: Justin Stitt <[email protected]> Cc: Miguel Ojeda <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Heiko Carstens <[email protected]> Cc: Marc Herbert <[email protected]> Cc: Uros Bizjak <[email protected]> Cc: Tejun Heo <[email protected]> Cc: Jeff Xu <[email protected]> Cc: "Michal Koutný" <[email protected]> Cc: Shakeel Butt <[email protected]> Cc: "Thomas Weißschuh" <[email protected]> Cc: John Stultz <[email protected]> Cc: Christian Brauner <[email protected]> Cc: Randy Dunlap <[email protected]> Cc: Brian Gerst <[email protected]> Cc: Masahiro Yamada <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Signed-off-by: Bill Wendling <[email protected]> --- include/linux/compiler_types.h | 11 +++++++++++ init/Kconfig | 5 +++++ 2 files changed, 16 insertions(+) diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h index 0a1b9598940d..2b0251bb951c 100644 --- a/include/linux/compiler_types.h +++ b/include/linux/compiler_types.h @@ -351,6 +351,17 @@ struct ftrace_likely_data { # define __assume(expr) #endif +/* + * Optional: only supported since clang >= 21 + * + * clang: https://github.com/llvm/llvm-project/pull/137250 + */ +#ifdef CONFIG_CC_HAS_COUNTED_BY_FOR_POINTER +#define __counted_by_ptr(member) __attribute__((__counted_by__(member))) +#else +#define __counted_by_ptr(member) +#endif + /* * Optional: only supported since gcc >= 15 * Optional: only supported since clang >= 18 diff --git a/init/Kconfig b/init/Kconfig index cab3ad28ca49..298c94c4c1b1 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -139,6 +139,11 @@ 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_ON_POINTERS + bool + # Needs clang 21.1.0 or higher. + default y if CC_IS_CLANG && CLANG_VERSION >= 210100 + config CC_HAS_MULTIDIMENSIONAL_NONSTRING def_bool $(success,echo 'char tag[][4] __attribute__((__nonstring__)) = { };' | $(CC) $(CLANG_FLAGS) -x c - -c -o /dev/null -Werror) -- 2.52.0.rc2.455.g230fcf2819-goog
