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Date:   Mon, 22 May 2023 17:46:35 +0200
From:   Miquel Raynal <miquel.raynal@bootlin.com>
To:     Arnd Bergmann <arnd@kernel.org>
Cc:     Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        =?UTF-8?B?TWljaGHFgiBLxJlwaWXFhA==?= <kernel@kempniu.pl>,
        Arnd Bergmann <arnd@arndb.de>, linux-mtd@lists.infradead.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mtdchar: mark bits of ioctl handler noinline
Message-ID: <20230522174635.7acfb42c@xps-13>
In-Reply-To: <20230417205654.1982368-1-arnd@kernel.org>
References: <20230417205654.1982368-1-arnd@kernel.org>
Organization: Bootlin
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Hi Arnd,

arnd@kernel.org wrote on Mon, 17 Apr 2023 22:56:50 +0200:

> From: Arnd Bergmann <arnd@arndb.de>
>=20
> The addition of the mtdchar_read_ioctl() function caused the stack usage
> of mtdchar_ioctl() to grow beyond the warning limit on 32-bit architectur=
es
> with gcc-13:
>=20
> drivers/mtd/mtdchar.c: In function 'mtdchar_ioctl':
> drivers/mtd/mtdchar.c:1229:1: error: the frame size of 1488 bytes is larg=
er than 1024 bytes [-Werror=3Dframe-larger-than=3D]
>=20
> Mark both the read and write portions as noinline_for_stack to ensure
> they don't get inlined and use separate stack slots to reduce the
> maximum usage, both in the mtdchar_ioctl() and combined with any
> of its callees.
>=20
> Fixes: 095bb6e44eb1 ("mtdchar: add MEMREAD ioctl")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

I am about to take this as part of my next fixes PR, should we Cc:
stable? What is the current policy wrt gcc version issues?

> ---
>  drivers/mtd/mtdchar.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>=20
> diff --git a/drivers/mtd/mtdchar.c b/drivers/mtd/mtdchar.c
> index 01f1c6792df9..8dc4f5c493fc 100644
> --- a/drivers/mtd/mtdchar.c
> +++ b/drivers/mtd/mtdchar.c
> @@ -590,8 +590,8 @@ static void adjust_oob_length(struct mtd_info *mtd, u=
int64_t start,
>  			    (end_page - start_page + 1) * oob_per_page);
>  }
> =20
> -static int mtdchar_write_ioctl(struct mtd_info *mtd,
> -		struct mtd_write_req __user *argp)
> +static noinline_for_stack int
> +mtdchar_write_ioctl(struct mtd_info *mtd, struct mtd_write_req __user *a=
rgp)
>  {
>  	struct mtd_info *master =3D mtd_get_master(mtd);
>  	struct mtd_write_req req;
> @@ -688,8 +688,8 @@ static int mtdchar_write_ioctl(struct mtd_info *mtd,
>  	return ret;
>  }
> =20
> -static int mtdchar_read_ioctl(struct mtd_info *mtd,
> -		struct mtd_read_req __user *argp)
> +static noinline_for_stack int
> +mtdchar_read_ioctl(struct mtd_info *mtd, struct mtd_read_req __user *arg=
p)
>  {
>  	struct mtd_info *master =3D mtd_get_master(mtd);
>  	struct mtd_read_req req;


Thanks,
Miqu=C3=A8l