Compiler Attributes: counted_by: Adjust name and identifier expansion

[PATCH] Compiler Attributes: counted_by: Adjust name and identifier expansion

Posted by Kees Cook 2 years, 4 months ago

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 <ojeda@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Fixes: dd06e72e68bc ("Compiler Attributes: Add __counted_by macro")
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 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
+ *
+ *   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

Re: [PATCH] Compiler Attributes: counted_by: Adjust name and identifier expansion

Posted by Kees Cook 2 years, 4 months ago

On Thu, 17 Aug 2023 13:06:03 -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.

Applied to for-next/hardening, thanks!

[1/1] Compiler Attributes: counted_by: Adjust name and identifier expansion
      https://git.kernel.org/kees/c/c8248faf3ca2

Take care,

-- 
Kees Cook

Re: [PATCH] Compiler Attributes: counted_by: Adjust name and identifier expansion

Posted by Gustavo A. R. Silva 2 years, 4 months ago


On 8/17/23 14:06, 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 <ojeda@kernel.org>
> Cc: Nick Desaulniers <ndesaulniers@google.com>
> Fixes: dd06e72e68bc ("Compiler Attributes: Add __counted_by macro")
> Signed-off-by: Kees Cook <keescook@chromium.org>

Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Thanks
-- 
Gustavo

> ---
>   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
> + *
> + *   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

Re: [PATCH] Compiler Attributes: counted_by: Adjust name and identifier expansion

Posted by Miguel Ojeda 2 years, 4 months ago

On Thu, Aug 17, 2023 at 10:06 PM Kees Cook <keescook@chromium.org> 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 <ojeda@kernel.org>
> Cc: Nick Desaulniers <ndesaulniers@google.com>
> Fixes: dd06e72e68bc ("Compiler Attributes: Add __counted_by macro")
> Signed-off-by: Kees Cook <keescook@chromium.org>

Looks good to me, thanks. Perhaps we should split the UAPI bit into a
second patch.

I can take it into my tree; otherwise if you need this elsewhere:

    Acked-by: Miguel Ojeda <ojeda@kernel.org>

Cheers,
Miguel

Re: [PATCH] Compiler Attributes: counted_by: Adjust name and identifier expansion

Posted by Kees Cook 2 years, 4 months ago

On Fri, Aug 18, 2023 at 12:06:15AM +0200, Miguel Ojeda wrote:
> On Thu, Aug 17, 2023 at 10:06 PM Kees Cook <keescook@chromium.org> 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 <ojeda@kernel.org>
> > Cc: Nick Desaulniers <ndesaulniers@google.com>
> > Fixes: dd06e72e68bc ("Compiler Attributes: Add __counted_by macro")
> > Signed-off-by: Kees Cook <keescook@chromium.org>
> 
> Looks good to me, thanks. Perhaps we should split the UAPI bit into a
> second patch.

I'd like to keep the UAPI part -- that was an oversight when I first
added it.

> I can take it into my tree; otherwise if you need this elsewhere:
> 
>     Acked-by: Miguel Ojeda <ojeda@kernel.org>

Thanks! It'd be slightly easier for me if it was is my tree, so I'll
grab your Ack. :) Let me know if you'd prefer it otherwise.

-Kees

-- 
Kees Cook

Re: [PATCH] Compiler Attributes: counted_by: Adjust name and identifier expansion

Posted by Nathan Chancellor 2 years, 4 months ago

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 <ojeda@kernel.org>
> Cc: Nick Desaulniers <ndesaulniers@google.com>
> Fixes: dd06e72e68bc ("Compiler Attributes: Add __counted_by macro")
> Signed-off-by: Kees Cook <keescook@chromium.org>

Reviewed-by: Nathan Chancellor <nathan@kernel.org>

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
>

Re: [PATCH] Compiler Attributes: counted_by: Adjust name and identifier expansion

Posted by Kees Cook 2 years, 4 months ago

On Thu, Aug 17, 2023 at 01:13:04PM -0700, Nathan Chancellor wrote:
> 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 <ojeda@kernel.org>
> > Cc: Nick Desaulniers <ndesaulniers@google.com>
> > Fixes: dd06e72e68bc ("Compiler Attributes: Add __counted_by macro")
> > Signed-off-by: Kees Cook <keescook@chromium.org>
> 
> Reviewed-by: Nathan Chancellor <nathan@kernel.org>
> 
> 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).

Oops, yes. Excellent point. I'll bump this to 18.

-Kees

> 
> > + *
> > + *   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
> > 

-- 
Kees Cook