linux-kernel - Re: [PATCH] mtdchar: mark bits of ioctl handler noinline

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Message-ID: <20230522174635.7acfb42c@xps-13>
Date:   Mon, 22 May 2023 17:46:35 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Michał Kępień <kernel@...pniu.pl>,
        Arnd Bergmann <arnd@...db.de>, linux-mtd@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mtdchar: mark bits of ioctl handler noinline

Hi Arnd,

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

> From: Arnd Bergmann <arnd@...db.de>
> 
> The addition of the mtdchar_read_ioctl() function caused the stack usage
> of mtdchar_ioctl() to grow beyond the warning limit on 32-bit architectures
> with gcc-13:
> 
> drivers/mtd/mtdchar.c: In function 'mtdchar_ioctl':
> drivers/mtd/mtdchar.c:1229:1: error: the frame size of 1488 bytes is larger than 1024 bytes [-Werror=frame-larger-than=]
> 
> 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.
> 
> Fixes: 095bb6e44eb1 ("mtdchar: add MEMREAD ioctl")
> Signed-off-by: Arnd Bergmann <arnd@...db.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(-)
> 
> 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, uint64_t start,
>  			    (end_page - start_page + 1) * oob_per_page);
>  }
>  
> -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 *argp)
>  {
>  	struct mtd_info *master = mtd_get_master(mtd);
>  	struct mtd_write_req req;
> @@ -688,8 +688,8 @@ static int mtdchar_write_ioctl(struct mtd_info *mtd,
>  	return ret;
>  }
>  
> -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 *argp)
>  {
>  	struct mtd_info *master = mtd_get_master(mtd);
>  	struct mtd_read_req req;


Thanks,
Miquèl