Based on Thomas Weißschuh's series to kernel headers to no longer require
an installed libc when build testing the uapi headers, the same can now
be done for the scripts/check-uapi.sh script.

The only required change here is to add the  usr/dummy-include include
path.

Link: https://lore.kernel.org/lkml/20260227-kbuild-uapi-libc-v1-0-c17de0d19776@weissschuh.net/ [1]
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Thomas Weißschuh <linux@weissschuh.net>
Acked-by: Nathan Chancellor <nathan@kernel.org>
Link: https://patch.msgid.link/20260306163309.2015837-4-arnd@kernel.org
Signed-off-by: Nicolas Schier <nsc@kernel.org>

When ${CROSS_COMPILE} is set, but ${CC} is not set, the logic in
check-uapi.sh is different from the top-level Makefile, which defaults
to using the cross gcc. This leads to using the native gcc instead of the
cross version, resulting in unexpected false-positive and false-negative
output.

Use the same logic here that we use in Kbuild for consistency.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Thomas Weißschuh <linux@weissschuh.net>
Acked-by: Nathan Chancellor <nathan@kernel.org>
Link: https://patch.msgid.link/20260306163309.2015837-3-arnd@kernel.org
Signed-off-by: Nicolas Schier <nsc@kernel.org>

While testing ABI changes across all architectures, I found that abidiff
sometimes produces nonsensical output. Further debugging identified
missing or broken libelf support for architecture specific relocations
in ET_REL binaries as the source of the problem[1].

Change the script to no longer produce a relocatable object file but
instead create a shared library for each header. This makes abidiff
work for all of the architectures in upstream linux kernels.

Link: https://sourceware.org/bugzilla/show_bug.cgi?id=33869
Cc: stable@vger.kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Thomas Weißschuh <linux@weissschuh.net>
Acked-by: Nathan Chancellor <nathan@kernel.org>
Link: https://patch.msgid.link/20260306163309.2015837-2-arnd@kernel.org
Signed-off-by: Nicolas Schier <nsc@kernel.org>

While the kernel community has been good at maintaining backwards
compatibility with kernel UAPIs, it would be helpful to have a tool
to check if a commit introduces changes that break backwards
compatibility.

To that end, introduce check-uapi.sh: a simple shell script that
checks for changes to UAPI headers using libabigail.

libabigail is "a framework which aims at helping developers and
software distributors to spot some ABI-related issues like interface
incompatibility in ELF shared libraries by performing a static
analysis of the ELF binaries at hand."

The script uses one of libabigail's tools, "abidiff", to compile the
changed header before and after the commit to detect any changes.

abidiff "compares the ABI of two shared libraries in ELF format. It
emits a meaningful report describing the differences between the two
ABIs."

The script also includes the ability to check the compatibility of
all UAPI headers across commits. This allows developers to inspect
the stability of the UAPIs over time.

Signed-off-by: John Moon <quic_johmoo@quicinc.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>