linux-stable.git/usr, branch master

kbuild: uapi: also test UAPI headers against C++ compilers

2026-03-25T12:24:42+00:00

C++ language requirements differ from those of C.

Also test the headers against C++ compilers to make sure no errors
creep in accidentally.

Signed-off-by: Thomas Weißschuh 
Reviewed-by: Nathan Chancellor 
Link: https://patch.msgid.link/20260316-kbuild-uapi-c-v2-5-35d6d0ed863f@weissschuh.net
Signed-off-by: Nicolas Schier

kbuild: uapi: provide a C++ compatible dummy definition of NULL

2026-03-25T12:24:41+00:00

NULL works differently in C++ compared to C.

To allow testing the UAPI headers against C++ compilers, provide
a variant of NULL which works with those.

Signed-off-by: Thomas Weißschuh 
Reviewed-by: Nathan Chancellor 
Link: https://patch.msgid.link/20260316-kbuild-uapi-c-v2-4-35d6d0ed863f@weissschuh.net
Signed-off-by: Nicolas Schier

kbuild: uapi: handle UML in architecture-specific exclusion lists

2026-03-25T12:24:41+00:00

When building User Mode Linux SRCARCH is set to 'um', while the actual
underlying architecture is provided in HEADER_ARCH.

Allow the exclusion lists to work on UML by comparing against
HEADER_ARCH when that is available.

Signed-off-by: Thomas Weißschuh 
Reviewed-by: Nathan Chancellor 
Link: https://patch.msgid.link/20260316-kbuild-uapi-c-v2-3-35d6d0ed863f@weissschuh.net
Signed-off-by: Nicolas Schier

kbuild: uapi: move all include path flags together

2026-03-25T12:24:40+00:00

The argument to add the root of the UAPI header tree to the include path
is separated from the other arguments concerning the include path.

Move all include path arguments together for more consistency and
balanced line lengths.

Signed-off-by: Thomas Weißschuh 
Reviewed-by: Nathan Chancellor 
Link: https://patch.msgid.link/20260316-kbuild-uapi-c-v2-2-35d6d0ed863f@weissschuh.net
Signed-off-by: Nicolas Schier

kbuild: uapi: move some compiler arguments out of the command definition

2026-03-25T12:24:40+00:00

Simplify the definition of cmd_hdrtest by moving some of it to a new
variable. This will both enable the upcoming reuse of those flags
and also the extension of cmd_hdrtest.

Signed-off-by: Thomas Weißschuh 
Reviewed-by: Nathan Chancellor 
Link: https://patch.msgid.link/20260316-kbuild-uapi-c-v2-1-35d6d0ed863f@weissschuh.net
Signed-off-by: Nicolas Schier

kbuild: uapi: remove now unneeded guard headers

2026-03-12T11:48:09+00:00

The test compilation does not allow usage of the toolchain headers
anymore, so these dummy headers are not needed anymore.

Signed-off-by: Thomas Weißschuh 
Reviewed-by: Nathan Chancellor 
Reviewed-by: Nicolas Schier 
Tested-by: Nicolas Schier 
Acked-by: Arnd Bergmann 
Link: https://patch.msgid.link/20260227-kbuild-uapi-libc-v1-9-c17de0d19776@weissschuh.net
Signed-off-by: Nicolas Schier

kbuild: uapi: simplify libc dependency logic

2026-03-12T11:48:08+00:00

The only left user of the condition inverts it.

Invert the condition completely and simplify its user.

Signed-off-by: Thomas Weißschuh 
Reviewed-by: Nathan Chancellor 
Reviewed-by: Nicolas Schier 
Tested-by: Nicolas Schier 
Acked-by: Arnd Bergmann 
Link: https://patch.msgid.link/20260227-kbuild-uapi-libc-v1-8-c17de0d19776@weissschuh.net
Signed-off-by: Nicolas Schier

kbuild: uapi: use custom stub headers instead of libc ones

2026-03-12T11:48:08+00:00

Now that custom stub headers are provided for all libc headers used from
the UAPI headers, the dependency on the toolchain libc can be dropped.

Signed-off-by: Thomas Weißschuh 
Reviewed-by: Nathan Chancellor 
Reviewed-by: Nicolas Schier 
Tested-by: Nicolas Schier 
Acked-by: Arnd Bergmann 
Link: https://patch.msgid.link/20260227-kbuild-uapi-libc-v1-7-c17de0d19776@weissschuh.net
Signed-off-by: Nicolas Schier

kbuild: uapi: provide stub includes for some libc headers

2026-03-12T11:48:08+00:00

Some UAPI headers incorrectly use libc headers. To compile-test these
UAPI headers, their respective libc dependencies need to be present.
Not all kernel toolchains provide these headers, reducing test coverage.

Introduce some stub headers which provide just enough symbols to test
all UAPI headers. Most headers are empty anyways, as their symbols are
only used in macros which are not actually evaluated.

As these headers are only ever used with newer kernel toolchains, they
can defer to compiler builtins in many cases.

As more UAPI headers are cleaned up to not require these stubs anymore,
they can be removed again.

Signed-off-by: Thomas Weißschuh 
Reviewed-by: Nathan Chancellor 
Reviewed-by: Nicolas Schier 
Tested-by: Nicolas Schier 
Acked-by: Arnd Bergmann 
Link: https://patch.msgid.link/20260227-kbuild-uapi-libc-v1-6-c17de0d19776@weissschuh.net
Signed-off-by: Nicolas Schier

kbuild: uapi: only use dummy-include for headers which use libc

2026-03-12T11:48:08+00:00

The headers which do not rely on libc are using built using -nostdinc.
For them the dummy headers are pointless.

Signed-off-by: Thomas Weißschuh 
Reviewed-by: Nathan Chancellor 
Reviewed-by: Nicolas Schier 
Tested-by: Nicolas Schier 
Acked-by: Arnd Bergmann 
Link: https://patch.msgid.link/20260227-kbuild-uapi-libc-v1-5-c17de0d19776@weissschuh.net
Signed-off-by: Nicolas Schier