linux-kernel - Re: [PATCH 12/12] EFI: Runtime services virtual mapping

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]

Date:	Wed, 30 Oct 2013 17:32:27 +0800
From:	Dave Young <dyoung@...hat.com>
To:	Borislav Petkov <bp@...en8.de>
Cc:	X86 ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
	Borislav Petkov <bp@...e.de>,
	Matt Fleming <matt@...sole-pimps.org>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	Vivek Goyal <vgoyal@...hat.com>, linux-efi@...r.kernel.org,
	fwts-devel@...ts.ubuntu.com
Subject: Re: [PATCH 12/12] EFI: Runtime services virtual mapping

On 10/29/13 at 10:40am, Borislav Petkov wrote:
> On Tue, Oct 29, 2013 at 02:47:20PM +0800, Dave Young wrote:
> > Boris, could you update the comment? it says below: update that memory
> > descriptor with the virtual address obtained from ioremap().
> >
> > Logiclly your patch should update it, then my patch update it again
> > with the case of mapping to fixed address for kexec.
> 
> Thanks for catching this, I ended up doing the following:
> 
> /*
>  * This function will switch the EFI runtime services to virtual mode.
>  * Essentially, we look through the EFI memmap and map every region that
>  * has the runtime attribute bit set in its memory descriptor into the
>  * ->trampoline_pgd page table using a top-down VA allocation scheme.
>  *
>  * The old method which used to update that memory descriptor with the
>  * virtual address obtained from ioremap() is still supported when the
>  * kernel is booted with efi=old_map on its command line. Same old
>  * method enabled the runtime services to be called without having to
>  * thunk back into physical mode for every invocation.
>  *
>  * The new method does a pagetable switch in a preemption-safe manner
>  * so that we're in a different address space when calling a runtime
>  * function. For function arguments passing we do copy the PGDs of the
>  * kernel page table into ->trampoline_pgd prior to each call.
>  */

Boris, thanks for update, it's very elaborate, I have still wonder if
32 bit case should be mentioned as well.

Waiting for you next version of the patch series. I will redo my patches
based on that.

Thanks
Dave
--
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/