linux-kernel - Re: [PATCH] x86: efi: Turn off efi_enabled after setup on mixed fw/kernel

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: <5033A0F0.8080705@zytor.com>
Date:	Tue, 21 Aug 2012 07:53:36 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Matt Fleming <matt.fleming@...el.com>
CC:	Olof Johansson <olof@...om.net>,
	Maarten Lankhorst <maarten.lankhorst@...onical.com>,
	linux-kernel@...r.kernel.org, mk@....su,
	Marko Kohtala <marko.kohtala@...il.com>,
	Matthew Garrett <mjg@...hat.com>,
	Peter Jones <pjones@...hat.com>
Subject: Re: [PATCH] x86: efi: Turn off efi_enabled after setup on mixed fw/kernel

On 08/21/2012 07:39 AM, Matt Fleming wrote:
> On Mon, 2012-08-20 at 14:59 -0700, Olof Johansson wrote:
>>>  From a quick glance with some grepping, efi reboot and efifb will
>>> also no longer work, is that intentional?
>>
>> That's the very point of this patch, the EFI services won't work since
>> there are no runtime services in this state, just boot time setup. If
>> efi_enabled is left on, the reboot will panic.
>
> But efifb should still work without EFI runtime services, no? I see this
> in setup_arch(),
>
> #ifdef CONFIG_VT
> #if defined(CONFIG_VGA_CONSOLE)
>          if (!efi_enabled || (efi_mem_type(0xa0000) != EFI_CONVENTIONAL_MEMORY))
>                  conswitchp = &vga_con;
> #elif defined(CONFIG_DUMMY_CONSOLE)
>          conswitchp = &dummy_con;
> #endif
> #endif
>
> but efi_enabled check looks bogus now that efi_enabled has come to mean
> "EFI services available?". If we've been passed the dimensions of the
> EFI framebuffer I'm unaware of a reason we can't use it.
>

Yes, this should be conditional on the parameters being available. 
However, efi_mem_type() is probably also ill-defined in this case.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/