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Date: Thu, 07 Mar 2024 11:42:12 +0000
From: Daniel Golle <daniel@makrotopia.org>
To: linux-mtd@lists.infradead.org, Dan Carpenter <dan.carpenter@linaro.org>,
 Zhihao Cheng <chengzhihao1@huawei.com>
CC: Richard Weinberger <richard@nod.at>,
 Miquel Raynal <miquel.raynal@bootlin.com>,
 Vignesh Raghavendra <vigneshr@ti.com>, linux-kernel@vger.kernel.org,
 Guenter Roeck <linux@roeck-us.net>, Daniel Diaz <daniel.diaz@linaro.org>,
 Naresh Kamboju <naresh.kamboju@linaro.org>
Subject: Re: [PATCH v2] mtd: ubi: fix NVMEM over UBI volumes on 32-bit systems
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On 7 March 2024 09:17:45 UTC, Dan Carpenter <dan=2Ecarpenter@linaro=2Eorg>=
 wrote:
>On Wed, Feb 28, 2024 at 09:45:13AM +0800, Zhihao Cheng wrote:
>> =E5=9C=A8 2024/2/28 8:46, Daniel Golle =E5=86=99=E9=81=93:
>> > A compiler warning related to sizeof(int) !=3D 8 when calling do_div(=
)
>> > is triggered when building on 32-bit platforms=2E
>> > Address this by using integer types having a well-defined size=2E
>> >=20
>> > Fixes: 3ce485803da1 ("mtd: ubi: provide NVMEM layer over UBI volumes"=
)
>> > Signed-off-by: Daniel Golle <daniel@makrotopia=2Eorg>
>> > ---
>> > v2: use size_t for 'bytes_left' variable to match parameter type
>> >=20
>> >   drivers/mtd/ubi/nvmem=2Ec | 5 ++++-
>> >   1 file changed, 4 insertions(+), 1 deletion(-)
>> >=20
>> > diff --git a/drivers/mtd/ubi/nvmem=2Ec b/drivers/mtd/ubi/nvmem=2Ec
>> > index b7a93c495d172=2E=2Ee68b8589c4279 100644
>> > --- a/drivers/mtd/ubi/nvmem=2Ec
>> > +++ b/drivers/mtd/ubi/nvmem=2Ec
>> > @@ -23,9 +23,12 @@ struct ubi_nvmem {
>> >   static int ubi_nvmem_reg_read(void *priv, unsigned int from,
>> >   			      void *val, size_t bytes)
>> >   {
>> > -	int err =3D 0, lnum =3D from, offs, bytes_left =3D bytes, to_read;
>> >   	struct ubi_nvmem *unv =3D priv;
>> >   	struct ubi_volume_desc *desc;
>> > +	size_t bytes_left =3D bytes;
>> > +	uint32_t offs, to_read;
>> There still exist a type truncation assignment 'to_read =3D bytes_left'=
 below,
>> although it's safe in logic=2E
>
>Yeah=2E  As you say, from looking at the logic we know it's safe=2E
>
>    41                  if (to_read > bytes_left)
>    42                          to_read =3D bytes_left;
>
>Obviously the new value is smaller than the original, so it must fit
>within a u32 range=2E=2E=2E


I've sent v3 of this fix which should be finally be warning free now=2E

https://patchwork=2Eozlabs=2Eorg/project/linux-mtd/patch/ff29447dcee834c17=
e4e1e99725b9454c90136ca=2E1709178325=2Egit=2Edaniel@makrotopia=2Eorg/

>
>This bug has been breaking the build since Dec 19=2E =20

I have a hard time believing that as the offending commit was only applied=
 on Feb 25=2E

https://git=2Ekernel=2Eorg/pub/scm/linux/kernel/git/next/linux-next=2Egit/=
commit/?id=3D3ce485803da1b79b2692b6d0c2792829292ad838

> It's fine if you're
>able to manually create your own =2Econfigs to work around build breakage=
=2E
>But if you're doing automated testing at scale then it's a show stopper=
=2E
>Could we please fix it=2E
>
>regards,
>dan carpenter
>
>
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