Re: [PATCH v5 1/2] check-uapi: Introduce check-uapi.sh - Greg Kroah-Hartman

From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Masahiro Yamada <masahiroy@kernel.org>
Cc: John Moon <quic_johmoo@quicinc.com>,
	Nathan Chancellor <nathan@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Nicolas Schier <nicolas@fjasle.eu>,
	linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-arm-msm@vger.kernel.org,
	Randy Dunlap <rdunlap@infradead.org>,
	Arnd Bergmann <arnd@arndb.de>,
	Bjorn Andersson <andersson@kernel.org>,
	Todd Kjos <tkjos@google.com>,
	Matthias Maennich <maennich@google.com>,
	Giuliano Procida <gprocida@google.com>,
	kernel-team@android.com, libabigail@sourceware.org,
	Jordan Crouse <jorcrous@amazon.com>,
	Trilok Soni <quic_tsoni@quicinc.com>,
	Satya Durga Srinivasu Prabhala <quic_satyap@quicinc.com>,
	Elliot Berman <quic_eberman@quicinc.com>,
	Guru Das Srinagesh <quic_gurus@quicinc.com>
Subject: Re: [PATCH v5 1/2] check-uapi: Introduce check-uapi.sh
Date: Mon, 10 Apr 2023 20:45:46 +0200	[thread overview]
Message-ID: <2023041015-lunar-dandelion-1b4e@gregkh> (raw)
In-Reply-To: <CAK7LNAQQmoyUx+0Jk3c7iqY20KokrHEOPwHNb2doZOOA8RWBDA@mail.gmail.com>

On Mon, Apr 10, 2023 at 07:03:05PM +0900, Masahiro Yamada wrote:
> On Sat, Apr 8, 2023 at 5:35 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>
> 
> 
> 
> BTW, is there anybody (except the submitters) who loves this tool?
> (or anybody who has ever evaluated this?)

I evaluated the first one, and yes, I do want this, but I haven't tested
it out yet, sorry.

I get patches for header files all the time and hand-verifying that they
don't break the abi is a pain at times

> According to this tool, it looks like we broke a lot of UAPI
> headers in the previous MW (between v6.2 and v6.3-rc1).

That's not ok, and needs to be fixed, otherwise this is useless as no
one can rely on it at all.

> The script takes some time because it builds many objects
> internally.
> 
> However, once this script starts running, you must not hit Ctrl-C.
> If you do it, your repository will be sprinkled with a ton
> of untracked files.

That needs to be unwound and fixed.

> CAVEAT
> This tool runs 'git checkout' a couple of times internally.
> If you interrupt it, your worktree might be messed up.

ctrl-c can be properly caught and the git state needs to be restored for
this to be able to be accepted.

thanks,

greg k-h