linux-kernel - Re: [PATCH] export efi.flags to sysfs

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:	Fri, 30 May 2014 10:24:38 +0800
From:	Dave Young <dyoung@...hat.com>
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	matt.fleming@...el.com, bp@...en8.de, linux-kernel@...r.kernel.org,
	linux-efi@...r.kernel.org
Subject: Re: [PATCH] export efi.flags to sysfs

On 05/29/14 at 08:45am, Vivek Goyal wrote:
> On Thu, May 29, 2014 at 10:08:37AM +0800, Dave Young wrote:
> > On 05/28/14 at 08:40am, Vivek Goyal wrote:
> > > On Wed, May 28, 2014 at 10:13:59AM +0800, Dave Young wrote:
> > > > On 05/27/14 at 09:34am, Vivek Goyal wrote:
> > > > > On Mon, May 26, 2014 at 04:39:35PM +0800, Dave Young wrote:
> > > > > > 
> > > > > > For efi=old_map and any old_map quirks like SGI UV in current
> > > > > > tree kexec/kdump will fail because it depends on the new 1:1 mapping.
> > > > > > 
> > > > > > Thus export the mapping method to sysfs so kexec tools can switch
> > > > > > to original way to boot.
> > > > > > 
> > > > > > Since we have efi.flags for all efi facilities so let's just export the
> > > > > > efi.flags itself, it maybe useful for other arches and use cases.
> > > > > > 
> > > > > 
> > > > > Does it require any documentation in Documentation/ABI/..
> > > > 
> > > > Yes, it's necessary. Will do in next version.
> > > > 
> > > > I'm still discussing with Matt, exporting efi.flags seems not a good way
> > > > because they are more internal interfaces. 
> > > > 
> > > > Probably I should export only a file 'old_map' instead.
> > > 
> > > How does /sys/firmware/efi/runtime-map/* look like with old mapping? Can't
> > > we look at it and figure out if it is 1:1 or not.
> > 
> > There's phys_addr and virt_addr, (virt_addr - phys_addr) will always be
> > -64G for 1:1 map, ioremapped addresses space is different.

Correct myself it's top to down (-4G - -64G) instead of down to top. 

> 
> I am curious that what's the meaning of 1:1 mapping here? So far I thought
> that means virt and physical addresses are same but that does not seem
> to be the case. So what does it mean?

while doing the mapping, we will iterate the memory ranges (md[])

Like below without considering alignment:
Virt addr   (down) <------------------------------> (top)
md0 (size0)                                 <-----> 
                                             (size0)
md1 (size1)                        <------->
                                    (size1)
...

Boris can correct me if I'm wrong.

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/