Re: [PATCH] include/uapi/linux/swab: Fix potentially missing __always_inline

From: Florian Fainelli
Date: Thu Oct 06 2022 - 16:34:08 EST


Hi Nathan,

On 9/28/2022 3:36 PM, Nathan Chancellor wrote:
Hi Florian,

On Tue, Sep 27, 2022 at 02:52:56PM -0700, Florian Fainelli wrote:
From: Matt Redfearn <matt.redfearn@xxxxxxxx>

Commit bc27fb68aaad ("include/uapi/linux/byteorder, swab: force inlining
of some byteswap operations") added __always_inline to swab functions
and commit 283d75737837 ("uapi/linux/stddef.h: Provide __always_inline to
userspace headers") added a definition of __always_inline for use in
exported headers when the kernel's compiler.h is not available.

However, since swab.h does not include stddef.h, if the header soup does
not indirectly include it, the definition of __always_inline is missing,
resulting in a compilation failure, which was observed compiling the
perf tool using exported headers containing this commit:

In file included from /usr/include/linux/byteorder/little_endian.h:12:0,
from /usr/include/asm/byteorder.h:14,
from tools/include/uapi/linux/perf_event.h:20,
from perf.h:8,
from builtin-bench.c:18:
/usr/include/linux/swab.h:160:8: error: unknown type name `__always_inline'
static __always_inline __u16 __swab16p(const __u16 *p)

Fix this by replacing the inclusion of linux/compiler.h with
linux/stddef.h to ensure that we pick up that definition if required,
without relying on it's indirect inclusion. compiler.h is then included
indirectly, via stddef.h.

Fixes: 283d75737837 ("uapi/linux/stddef.h: Provide __always_inline to userspace headers")
Signed-off-by: Matt Redfearn <matt.redfearn@xxxxxxxx>
Reviewed-by: Petr Vaněk <arkamar@xxxxxxxx>
Signed-off-by: Florian Fainelli <f.fainelli@xxxxxxxxx>

I took this through my kernel build matrix and did not see any new
issues.

Tested-by: Nathan Chancellor <nathan@xxxxxxxxxx>

Great thanks! Since this is really useful for kernel-headers in toolchains, it would be great to get this picked up. Arnd is this something that would go via your tree?
--
Florian