netdev - Re: [PATCH net-next] stddef: don't include compiler

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Message-ID: <20250820101752.63be03da@kernel.org>
Date: Wed, 20 Aug 2025 10:17:52 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Kees Cook <kees@...nel.org>
Cc: davem@...emloft.net, netdev@...r.kernel.org, edumazet@...gle.com,
 pabeni@...hat.com, andrew+netdev@...n.ch, horms@...nel.org,
 dhowells@...hat.com, gustavoars@...nel.org, aleksander.lobakin@...el.com,
 tstruk@...aio.com
Subject: Re: [PATCH net-next] stddef: don't include compiler_types.h in the
 uAPI header

On Mon, 18 Aug 2025 21:06:10 -0700 Kees Cook wrote:
> > Since nothing needs this include, let's remove it.  
> 
> But yes, nothing uses compiler_types.h via uapi/linux/stddef.h. That
> does seem to be true.

While staring at the kbuild bot report (which I can't repro :|) 
I realized this include is to give kernel's __counted_by and friends
precedence over the empty uAPI-facing defines.

Not sure this is the most fortunate approach, personally I'd rather wrap
our empty user-space-facing defines under ifndef __KERNEL__. I think
it'd be better from "include what you need" perspective. Perhaps stddef
pulling in compiler annotations is expected, dunno...

Would you be okay with:

diff --git a/scripts/headers_install.sh b/scripts/headers_install.sh
index 6bbccb43f7e7..4c20c62c4faf 100755
--- a/scripts/headers_install.sh
+++ b/scripts/headers_install.sh
@@ -32,7 +32,7 @@ fi
 sed -E -e '
        s/([[:space:](])(__user|__force|__iomem)[[:space:]]/\1/g
        s/__attribute_const__([[:space:]]|$)/\1/g
-       s@...nclude <linux/compiler(|_types).h>@@
+       s@...nclude <linux/compiler.h>@@
        s/(^|[^a-zA-Z0-9])__packed([^a-zA-Z0-9_]|$)/\1__attribute__((packed))\2/g
        s/(^|[[:space:](])(inline|asm|volatile)([[:space:](]|$)/\1__\2__\3/g
        s@#(ifndef|define|endif[[:space:]]*/[*])[[:space:]]*_UAPI@#\1 @
diff --git a/include/uapi/linux/stddef.h b/include/uapi/linux/stddef.h
index b87df1b485c2..9a28f7d9a334 100644
--- a/include/uapi/linux/stddef.h
+++ b/include/uapi/linux/stddef.h
@@ -2,7 +2,9 @@
 #ifndef _UAPI_LINUX_STDDEF_H
 #define _UAPI_LINUX_STDDEF_H
 
+#ifdef __KERNEL__
 #include <linux/compiler_types.h>
+#endif

? As you pointed out compiler_types.h is only included under stddef.h
so the special handling in the installation script is easily avoided.