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

[John Moon <quic_johmoo@quicinc.com>]

On 4/7/2023 12:27 PM, Masahiro Yamada wrote:
> On Tue, Mar 28, 2023 at 2:42 AM John Moon <quic_johmoo@quicinc.com> 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@quicinc.com>
>> ---
>>      - 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.