linux-kernel - Re: [PATCH 11/99] fbdev/aty: Duplicate video-mode option string

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Date:   Mon, 6 Mar 2023 17:13:34 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Thomas Zimmermann <tzimmermann@...e.de>
Cc:     deller@....de, paulus@...ba.org, benh@...nel.crashing.org,
        linux@...linux.org.uk, pjones@...hat.com, timur@...nel.org,
        adaplas@...il.com, s.hauer@...gutronix.de, shawnguo@...nel.org,
        mbroemme@...mpq.org, thomas@...ischhofer.net,
        James.Bottomley@...senpartnership.com, spock@...too.org,
        sudipm.mukherjee@...il.com, teddy.wang@...iconmotion.com,
        geert+renesas@...der.be, corbet@....net,
        linux-fbdev@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 11/99] fbdev/aty: Duplicate video-mode option string

Hi Thomas,

Thanks for your patch!

On Mon, Mar 6, 2023 at 5:00 PM Thomas Zimmermann <tzimmermann@...e.de> wrote:
> Assume that the driver does not own the option string or its substrings
> and hence duplicate the option string for the video mode. The driver only
> parses the option string once as part of module initialization, so use
> a static buffer to store the duplicated mode option. Linux automatically
> frees the memory upon releasing the module.

Are you sure about that?
All of this code is inside "#ifndef MODULE".
In the aty128fb case, the function is not marked __init.
Enabling these 3 drivers adds 3x256 bytes of static buffer, more
if you enable more fbdev drivers.

> Done in preparation of switching the driver to struct option_iter and
> constifying the option string.
>
> Signed-off-by: Thomas Zimmermann <tzimmermann@...e.de>

> --- a/drivers/video/fbdev/aty/aty128fb.c
> +++ b/drivers/video/fbdev/aty/aty128fb.c
> @@ -1723,7 +1723,17 @@ static int aty128fb_setup(char *options)
>                         continue;
>                 }
>  #endif /* CONFIG_PPC_PMAC */
> -               mode_option = this_opt;
> +               {
> +                       static char mode_option_buf[256];
> +                       int ret;
> +
> +                       ret = snprintf(mode_option_buf, sizeof(mode_option_buf), "%s", this_opt);
> +                       if (WARN(ret < 0, "aty128: ignoring invalid option, ret=%d\n", ret))
> +                               continue;
> +                       if (WARN(ret >= sizeof(mode_option_buf), "aty128fb: option too long\n"))
> +                               continue;
> +                       mode_option = mode_option_buf;
> +               }
>         }
>         return 0;
>  }
eturn 0;
>  }

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds