linux-kernel - Re: [tip:core/memblock] x86, memblock: Fix crashkernel allocation

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: <4CAE1767.5040409@intel.com>
Date:	Thu, 07 Oct 2010 11:54:31 -0700
From:	"H. Peter Anvin" <h.peter.anvin@...el.com>
To:	Vivek Goyal <vgoyal@...hat.com>
CC:	"mingo@...hat.com" <mingo@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"yinghai@...nel.org" <yinghai@...nel.org>,
	"caiqian@...hat.com" <caiqian@...hat.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"linux-tip-commits@...r.kernel.org" 
	<linux-tip-commits@...r.kernel.org>,
	Kexec Mailing List <kexec@...ts.infradead.org>
Subject: Re: [tip:core/memblock] x86, memblock: Fix crashkernel allocation

On 10/07/2010 11:18 AM, Vivek Goyal wrote:
> 
> Ok, I was browsing through kexec-tools, x86 bzImage code and trying to
> refresh my memory what segments were being loaded and what were memory
> address concerns.
> 
> - relocatable bzImage (max addr 0x37ffffff, 896MB). 
> 	Though I don't know/understand where that 896MB come from.
> 
> - initrd (max addr 0x37ffffff, 896MB)
> 	Don't know why 896MB as upper limit

896 MB is presumably the (default!!) LOWMEM limit on 32 bits.  This is
actually wrong if vmalloc= is also specified on command line, though, or
with nonstandard compile-time options.

> - Purgatory (max addr 2G)
> 
> - A segment to keep elf headers (no limit)
> 	These are accessed when second kernel as fully booted so can be
> 	addressed in higher addresses.
> 
> - A backup segment to copy first 640K of memory (not aware of any limit)
> - Setup/parameter segment (no limit)
> 	- We don't really execute anything here and just access it for
>   	  command line.

Probably has a 4 GB limit, since I believe it only has a 32-bit pointer.

> So atleast for bzImage it looks that if we specify crashkernel=128M<896M, it
> will work.
> 
> So I am fine with above additional syntax for crashkernel=. May be we shall
> have to the deprecate the crashkernel=X<@0 syntax.
> 
> CCing kexec list, in case others have any comments.

It would be easy enough to either deprecate or make it an alias for
crashkernel=...<896M, which is basically what Yinghai's patch does.

	-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/