On Thu, Aug 17, 2023 at 01:06:03PM -0700, Kees Cook wrote:
> GCC and Clang's current RFCs name this attribute "counted_by", and have
> moved away from using a string for the member name. Update the kernel's
> macros to match. Additionally provide a UAPI no-op macro for UAPI structs
> that will gain annotations.
>
> Cc: Miguel Ojeda <[email protected]>
> Cc: Nick Desaulniers <[email protected]>
> Fixes: dd06e72e68bc ("Compiler Attributes: Add __counted_by macro")
> Signed-off-by: Kees Cook <[email protected]>
Reviewed-by: Nathan Chancellor <[email protected]>
One comment below.
> ---
> include/linux/compiler_attributes.h | 26 +++++++++++++-------------
> include/uapi/linux/stddef.h | 4 ++++
> 2 files changed, 17 insertions(+), 13 deletions(-)
>
> diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h
> index 00efa35c350f..74716a407aac 100644
> --- a/include/linux/compiler_attributes.h
> +++ b/include/linux/compiler_attributes.h
> @@ -94,6 +94,19 @@
> # define __copy(symbol)
> #endif
>
> +/*
> + * Optional: only supported since gcc >= 14
> + * Optional: only supported since clang >= 17
Since you are in the area, should the supported clang version be
optimistically updated to '18'? 17.x has already branched and I suspect
it would be too late in the release cycle to cherry-pick that change
from main if it were landed today (which seems pretty unlikely, given
there do not appear to be many reviews from high profile clang folks
yet).
> + *
> + * gcc: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108896
> + * clang: https://reviews.llvm.org/D148381
> + */
> +#if __has_attribute(__counted_by__)
> +# define __counted_by(member) __attribute__((__counted_by__(member)))
> +#else
> +# define __counted_by(member)
> +#endif
> +
> /*
> * Optional: not supported by gcc
> * Optional: only supported since clang >= 14.0
> @@ -129,19 +142,6 @@
> # define __designated_init
> #endif
>
> -/*
> - * Optional: only supported since gcc >= 14
> - * Optional: only supported since clang >= 17
> - *
> - * gcc: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108896
> - * clang: https://reviews.llvm.org/D148381
> - */
> -#if __has_attribute(__element_count__)
> -# define __counted_by(member) __attribute__((__element_count__(#member)))
> -#else
> -# define __counted_by(member)
> -#endif
> -
> /*
> * Optional: only supported since clang >= 14.0
> *
> diff --git a/include/uapi/linux/stddef.h b/include/uapi/linux/stddef.h
> index 7837ba4fe728..7c3fc3980881 100644
> --- a/include/uapi/linux/stddef.h
> +++ b/include/uapi/linux/stddef.h
> @@ -45,3 +45,7 @@
> TYPE NAME[]; \
> }
> #endif
> +
> +#ifndef __counted_by
> +#define __counted_by(m)
> +#endif
> --
> 2.34.1
>