linux-kernel - Re: [PATCH 5/6] kexec-bzImage: Support for loading bzImage using 64bit entry

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, 22 Nov 2013 07:24:37 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Vivek Goyal <vgoyal@...hat.com>, Greg KH <greg@...ah.com>
CC:	linux-kernel@...r.kernel.org, kexec@...ts.infradead.org,
	ebiederm@...ssion.com, mjg59@...f.ucam.org
Subject: Re: [PATCH 5/6] kexec-bzImage: Support for loading bzImage using
 64bit entry

On 11/21/2013 11:21 AM, Vivek Goyal wrote:
>>
>> What do you mean by the "real mode entry"?  Do we need to care about
>> that because we aren't falling back to real mode when executing this,
>> are we?  Or does that just happen for 32bit kernels?
> 
> Original kexec offers real mode entry choice too. So we fall back
> to real mode and jump to kernel and kernel makes bunch of BIOS calls. I
> don't think this is a commonly used option.
> 

I know some users of it (who I shall not name.)  In general it is a bad
option, because after running the first kernel the state of the hardware
is not guaranteed to be such that executing the BIOS is safe.  In
general, I do think they do it just because they tried at some point and
it happened to work; discouraging its use is probably for the better.

	-hpa

--
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/