Re: [PATCH v4 1/2] check-uapi: Introduce check-uapi.sh

[John Moon]

On 4/7/2023 12:27 PM, Masahiro Yamada wrote:
> On Tue, Mar 28, 2023 at 2:42 AM John Moon <quic_johmoo@xxxxxxxxxxx> wrote:
> > 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@xxxxxxxxxxx>
> > ---
> >      - Refactored to exclusively check headers installed by make
> >        headers_install. This simplified the code dramatically and removed
> >        the need to perform complex git diffs.
> >      - Removed the "-m" flag. Since we're checking all installed headers
> >        every time, a flag to check only modified files didn't make sense.
> >      - Added info message when usr/include/Makefile is not present that
> >        it's likely because that file was only introduced in v5.3.
> >      - Changed default behavior of log file. Now, the script will not
> >        create a log file unless you pass "-l <file>".
> >      - Simplified exit handler.
> >      - Added -j $MAX_THREADS to make headers_install to improve speed.
> >      - Cleaned up variable references.
> >
> >   scripts/check-uapi.sh | 488 ++++++++++++++++++++++++++++++++++++++++++
> >   1 file changed, 488 insertions(+)
> >   create mode 100755 scripts/check-uapi.sh
>
> > +
> > +# Install headers for both git refs
> > +install_headers() {
> > +       local -r base_ref="$1"
> > +       local -r past_ref="$2"
> > +
> > +       DEVIATED_FROM_CURRENT_TREE="false"
> > +       for ref in "$base_ref" "$past_ref"; do
> > +               if [ -n "$ref" ]; then
> > +                       if [ "$DEVIATED_FROM_CURRENT_TREE" = "false" ]; then
> > +                               save_tree_state
> > +                               DEVIATED_FROM_CURRENT_TREE="true"
> > +                       fi
> > +                       # This script ($0) is already loaded into memory at this point,
> > +                       # so this operation is safe
> > +                       git checkout --quiet "$(git rev-parse "$ref")"
> > +               fi
> > +
> > +               printf "Installing sanitized UAPI headers from %s... " "${ref:-dirty tree}"
> > +               make -j "$MAX_THREADS" ARCH="$ARCH" INSTALL_HDR_PATH="${TMP_DIR}/${ref}/usr" headers_install > /dev/null 2>&1
>
>
> You suppressed stderr.
>
> If 'make headers_install' fails, users see a sudden death
> with no clue.

Good point, will remove that suppression.