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Subject: Re: [PATCH] bcache: make kobj_type structures constant
From:   Coly Li <colyli@suse.de>
In-Reply-To: <3c7289e1-2f21-4adc-bed9-df44fd8988d3@t-8ch.de>
Date:   Sat, 15 Apr 2023 22:37:24 +0800
Cc:     Kent Overstreet <kent.overstreet@gmail.com>,
        linux-bcache@vger.kernel.org, linux-kernel@vger.kernel.org
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Message-Id: <0E590AA0-6A76-4816-AF2E-5079CD81A26C@suse.de>
References: <20230214-kobj_type-bcache-v1-1-cf00ead7bee7@weissschuh.net>
 <125CA8D6-D3B7-42FB-83BE-DCA688F2ACAF@suse.de>
 <20230214152119.epkfhkojqjvokqmv@t-8ch.de>
 <9DE71214-283C-4410-B5A4-22DFDA7021F4@suse.de>
 <4cc38847-a967-487b-8efe-81b741ab6782@t-8ch.de>
 <F63C6A45-E428-4557-9995-FDB43CE243B3@suse.de>
 <3c7289e1-2f21-4adc-bed9-df44fd8988d3@t-8ch.de>
To:     =?utf-8?Q?Thomas_Wei=C3=9Fschuh?= <linux@weissschuh.net>
Precedence: bulk


> 2023=E5=B9=B44=E6=9C=8815=E6=97=A5 02:38=EF=BC=8CThomas Wei=C3=9Fschuh =
<linux@weissschuh.net> =E5=86=99=E9=81=93=EF=BC=9A
>=20
> Hi Coly,
>=20
> On 2023-04-05 21:38:01+0800, Coly Li wrote:
>>> 2023=E5=B9=B44=E6=9C=885=E6=97=A5 01:38=EF=BC=8CThomas Wei=C3=9Fschuh =
<linux@weissschuh.net> =E5=86=99=E9=81=93=EF=BC=9A
>>>=20
>>> Hi Coly,
>>>=20
>>> On 2023-02-15 00:16:03+0800, Coly Li wrote:
>>>>> 2023=E5=B9=B42=E6=9C=8814=E6=97=A5 23:21=EF=BC=8CThomas Wei=C3=9Fsch=
uh <linux@weissschuh.net> =E5=86=99=E9=81=93=EF=BC=9A
>>>>>=20
>>>>> On Tue, Feb 14, 2023 at 05:51:09PM +0800, Coly Li wrote:
>>>>>>=20
>>>>>>=20
>>>>>>> 2023=E5=B9=B42=E6=9C=8814=E6=97=A5 11:13=EF=BC=8CThomas =
Wei=C3=9Fschuh <linux@weissschuh.net> =E5=86=99=E9=81=93=EF=BC=9A
>>>>>>>=20
>>>>>>> Since commit ee6d3dd4ed48 ("driver core: make kobj_type =
constant.")
>>>>>>> the driver core allows the usage of const struct kobj_type.
>>>>>>>=20
>>>>>>> Take advantage of this to constify the structure definitions to =
prevent
>>>>>>> modification at runtime.
>>>>>>>=20
>>>>>>=20
>>>>>> How the const structure definition can prevent modification at =
run time?
>>>>>=20
>>>>> It will be put into .rodata instead of .data by the compiler.
>>>>> The .rodata section is mapped as read-only via the pagetable.
>>>>>=20
>>>>> See Documentation/security/self-protection.rst
>>>>> "Function pointers and sensitive variables must not be writable".
>>>>=20
>>>> I see. Thanks for the information.
>>>>=20
>>>> This patch will be added into my testing queue, and submitted =
later.
>>>=20
>>> It seems this was not submitted.
>>> Or did I miss it?
>>=20
>> No I don=E2=80=99t submit it yet. It is not emergent fix, and stay =
with other testing patches together.
>>=20
>> Do you want it to go now?
>=20
> No, it's not urgent.
>=20
> I just assumed it should have been in next by now and thought it got
> lost along the way.
> Let's keep it with the other testing patches.

Some patches from Zheming are not simple, and I need to find time to go =
through them carefully.
If I am not able to handle them in time, I will submit the simple ones =
to Jens some time later.

Thanks.

Coly Li