linux-kernel - Re: [PATCH 0/5] Add second memory region for crash 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: <4BD0CFC1.2060907@zytor.com>
Date:	Thu, 22 Apr 2010 15:37:53 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Vitaly Mayatskikh <v.mayatskih@...il.com>,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	Haren Myneni <hbabu@...ibm.com>,
	Neil Horman <nhorman@...driver.com>,
	Cong Wang <amwang@...hat.com>, kexec@...ts.infradead.org
Subject: Re: [PATCH 0/5] Add second memory region for crash kernel

On 04/22/2010 03:07 PM, Eric W. Biederman wrote:
> 
> Have you tried loading a 64bit vmlinux directly into a higher address
> range?  There may be a bit or two missing but you should be able to
> load a linux kernel above 4GB.  I tested the basics of that mechanism
> when I made the 64bit relocatable kernel.
> 
> I don't buy the argument that there is a direct connection between
> the amount of memory you have and how much memory it takes to dump it.
> Even an indirect connections seems suspicious.
> 

We actually have a 64-bit entry point even in bzImage; it is at offset
+0x200 from the 32-bit entry point.  Right now that offset is not
exported anywhere, but it has been stable for a very long time... at
least for as far back as the decompressor has been 64 bits.

The interface to the 64-bit code is by necessity wider, since there is
no such thing as paging off in 64-bit mode, but it probably isn't *too*
hard to figure out how page tables need to be set up in order to work
properly.  At that point, it would be good to document it.

	-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/