linux-kernel - Re: [PATCH 2/2] moderr: add module error injection tool

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Message-ID: <CAADnVQLto_Zt7q4vmTFXby0QH8QX7r5am5inLskC5sKqL=0gow@mail.gmail.com>
Date: Tue, 4 Feb 2025 15:28:03 +0000
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Daniel Gomez <da.gomez@...nel.org>
Cc: Daniel Gomez <da.gomez@...sung.com>, Luis Chamberlain <mcgrof@...nel.org>, 
	Petr Pavlu <petr.pavlu@...e.com>, Sami Tolvanen <samitolvanen@...gle.com>, 
	Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, 
	Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
	Yonghong Song <yonghong.song@...ux.dev>, John Fastabend <john.fastabend@...il.com>, 
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, 
	Jiri Olsa <jolsa@...nel.org>, Nathan Chancellor <nathan@...nel.org>, 
	Nick Desaulniers <ndesaulniers@...gle.com>, Bill Wendling <morbo@...gle.com>, 
	Justin Stitt <justinstitt@...gle.com>, linux-modules@...r.kernel.org, 
	LKML <linux-kernel@...r.kernel.org>, bpf <bpf@...r.kernel.org>, 
	clang-built-linux <llvm@...ts.linux.dev>, iovisor-dev <iovisor-dev@...ts.iovisor.org>, 
	gost.dev@...sung.com
Subject: Re: [PATCH 2/2] moderr: add module error injection tool

On Tue, Feb 4, 2025 at 1:30 PM Daniel Gomez <da.gomez@...nel.org> wrote:
>
> On Wed, Jan 22, 2025 at 09:02:19AM +0100, Alexei Starovoitov wrote:
> > On Wed, Jan 22, 2025 at 5:12 AM Daniel Gomez <da.gomez@...sung.com> wrote:
> > >
> > > Add support for a module error injection tool. The tool
> > > can inject errors in the annotated module kernel functions
> > > such as complete_formation(), do_init_module() and
> > > module_enable_rodata_after_init(). Module name and module function are
> > > required parameters to have control over the error injection.
> > >
> > > Example: Inject error -22 to module_enable_rodata_ro_after_init for
> > > brd module:
> > >
> > > sudo moderr --modname=brd --modfunc=module_enable_rodata_ro_after_init \
> > > --error=-22 --trace
> > > Monitoring module error injection... Hit Ctrl-C to end.
> > > MODULE     ERROR FUNCTION
> > > brd        -22   module_enable_rodata_after_init()
> > >
> > > Kernel messages:
> > > [   89.463690] brd: module loaded
> > > [   89.463855] brd: module_enable_rodata_ro_after_init() returned -22,
> > > ro_after_init data might still be writable
> > >
> > > Signed-off-by: Daniel Gomez <da.gomez@...sung.com>
> > > ---
> > >  tools/bpf/Makefile            |  13 ++-
> > >  tools/bpf/moderr/.gitignore   |   2 +
> > >  tools/bpf/moderr/Makefile     |  95 +++++++++++++++++
> > >  tools/bpf/moderr/moderr.bpf.c | 127 +++++++++++++++++++++++
> > >  tools/bpf/moderr/moderr.c     | 236 ++++++++++++++++++++++++++++++++++++++++++
> > >  tools/bpf/moderr/moderr.h     |  40 +++++++
> > >  6 files changed, 510 insertions(+), 3 deletions(-)
> >
> > The tool looks useful, but we don't add tools to the kernel repo.
> > It has to stay out of tree.
>
> Can you clarify what do you mean? There are other tools under tools/ and tools/
> bpf [1].
>
> [1] https://lore.kernel.org/bpf/20200114184230.GA204154@krava/

As you noticed we added only one tool out of many and recently
discussed removing it, since the value of keeping it in the tree
is minimal.

> I will anyway move the tool to the suggested location in the other thread.

I don't think it's a good idea.
Keep it outside. There is no reason for it to live in the tree.