linux-kernel - Re: [PATCH v2 5/9] vgacon: remove screen

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <3b047cd4-a61f-44b6-830b-b4e35bfccd72@app.fastmail.com>
Date:   Wed, 19 Jul 2023 16:38:57 +0200
From:   "Arnd Bergmann" <arnd@...db.de>
To:     Phil Mathieu-Daudé <philmd@...aro.org>,
        "Arnd Bergmann" <arnd@...nel.org>, linux-fbdev@...r.kernel.org,
        "Thomas Zimmermann" <tzimmermann@...e.de>,
        "Helge Deller" <deller@....de>,
        "Javier Martinez Canillas" <javierm@...hat.com>
Cc:     linux-hyperv@...r.kernel.org, x86@...nel.org,
        linux-ia64@...r.kernel.org, linux-sh@...r.kernel.org,
        "Catalin Marinas" <catalin.marinas@....com>,
        "Linus Walleij" <linus.walleij@...aro.org>,
        "Dave Hansen" <dave.hansen@...ux.intel.com>,
        dri-devel@...ts.freedesktop.org, linux-mips@...r.kernel.org,
        "Max Filippov" <jcmvbkbc@...il.com>,
        "Will Deacon" <will@...nel.org>, linux-efi@...r.kernel.org,
        guoren <guoren@...nel.org>,
        "linux-csky@...r.kernel.org" <linux-csky@...r.kernel.org>,
        sparclinux@...r.kernel.org, linux-hexagon@...r.kernel.org,
        "WANG Xuerui" <kernel@...0n.name>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        "Dave Airlie" <airlied@...il.com>,
        "Ard Biesheuvel" <ardb@...nel.org>, "Wei Liu" <wei.liu@...nel.org>,
        "Huacai Chen" <chenhuacai@...nel.org>,
        "Dexuan Cui" <decui@...rosoft.com>,
        "Russell King" <linux@...linux.org.uk>,
        "Deepak Rawat" <drawat.floss@...il.com>,
        "Ingo Molnar" <mingo@...hat.com>,
        "Matt Turner" <mattst88@...il.com>,
        "Haiyang Zhang" <haiyangz@...rosoft.com>,
        "Nicholas Piggin" <npiggin@...il.com>,
        "Borislav Petkov" <bp@...en8.de>, loongarch@...ts.linux.dev,
        "John Paul Adrian Glaubitz" <glaubitz@...sik.fu-berlin.de>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        linux-arm-kernel@...ts.infradead.org,
        "Khalid Aziz" <khalid@...ehiking.org>,
        "Brian Cain" <bcain@...cinc.com>,
        "Thomas Bogendoerfer" <tsbogend@...ha.franken.de>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, "Dinh Nguyen" <dinguyen@...nel.org>,
        linux-riscv@...ts.infradead.org,
        "Palmer Dabbelt" <palmer@...belt.com>,
        "Daniel Vetter" <daniel@...ll.ch>, linux-alpha@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org,
        "David S . Miller" <davem@...emloft.net>
Subject: Re: [PATCH v2 5/9] vgacon: remove screen_info dependency

On Wed, Jul 19, 2023, at 15:49, Philippe Mathieu-Daudé wrote:
> On 19/7/23 14:39, Arnd Bergmann wrote:

>> @@ -1074,13 +1077,13 @@ static int vgacon_resize(struct vc_data *c, unsigned int width,
>>   		 * Ho ho!  Someone (svgatextmode, eh?) may have reprogrammed
>>   		 * the video mode!  Set the new defaults then and go away.
>>   		 */
>> -		screen_info.orig_video_cols = width;
>> -		screen_info.orig_video_lines = height;
>> +		vga_si->orig_video_cols = width;
>> +		vga_si->orig_video_lines = height;
>>   		vga_default_font_height = c->vc_cell_height;
>>   		return 0;
>>   	}
>> -	if (width % 2 || width > screen_info.orig_video_cols ||
>> -	    height > (screen_info.orig_video_lines * vga_default_font_height)/
>> +	if (width % 2 || width > vga_si->orig_video_cols ||
>> +	    height > (vga_si->orig_video_lines * vga_default_font_height)/
>>   	    c->vc_cell_height)
>>   		return -EINVAL;
>>   
>> @@ -1110,8 +1113,8 @@ static void vgacon_save_screen(struct vc_data *c)
>>   		 * console initialization routines.
>>   		 */
>>   		vga_bootup_console = 1;
>> -		c->state.x = screen_info.orig_x;
>> -		c->state.y = screen_info.orig_y;
>> +		c->state.x = vga_si->orig_x;
>> +		c->state.y = vga_si->orig_y;
>
> Not really my area, so bare with me if this is obviously not
> possible :) If using DUMMY_CONSOLE, can we trigger a save_screen
> / resize? If so, we'd reach here with vga_si=NULL.
>

I think it cannot happen because the only way that anything calls
into vgacon.c is through the "conswitchp = &vga_con;" that now happens
at the same time as the "vga_si = &screen_info;". It's definitely
possible that I'm missing something as well here.

     Arnd