From mboxrd@z Thu Jan  1 00:00:00 1970
Return-path: <kexec-bounces+dwmw2=infradead.org@lists.infradead.org>
Received: from mail.skyhub.de ([2a01:4f8:190:11c2::b:1457])
 by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux))
 id 1hIahH-0002HD-AS
 for kexec@lists.infradead.org; Mon, 22 Apr 2019 15:17:32 +0000
Date: Mon, 22 Apr 2019 17:17:23 +0200
From: Borislav Petkov <bp@alien8.de>
Subject: Re: [RFC PATCH] kexec, x86/boot: map systab region in identity
 mapping before accessing it
Message-ID: <20190422151723.GD21457@zn.tnic>
References: <20190419101733.GA10324@zn.tnic>
 <20190419105014.GE11060@MiWiFi-R3L-srv>
 <20190419112801.GB10324@zn.tnic> <20190419113621.GD10324@zn.tnic>
 <20190422143346.GD3584@localhost.localdomain>
MIME-Version: 1.0
Content-Disposition: inline
In-Reply-To: <20190422143346.GD3584@localhost.localdomain>
List-Id: <kexec.lists.infradead.org>
List-Unsubscribe: <http://lists.infradead.org/mailman/options/kexec>,
 <mailto:kexec-request@lists.infradead.org?subject=unsubscribe>
List-Archive: <http://lists.infradead.org/pipermail/kexec/>
List-Post: <mailto:kexec@lists.infradead.org>
List-Help: <mailto:kexec-request@lists.infradead.org?subject=help>
List-Subscribe: <http://lists.infradead.org/mailman/listinfo/kexec>,
 <mailto:kexec-request@lists.infradead.org?subject=subscribe>
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Sender: "kexec" <kexec-bounces@lists.infradead.org>
Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org
To: Baoquan He <bhe@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>
Cc: "x86@kernel.org" <x86@kernel.org>, Kairui Song <kasong@redhat.com>, Chao Fan <fanc.fnst@cn.fujitsu.com>, "kexec@lists.infradead.org" <kexec@lists.infradead.org>, linux-kernel@vger.kernel.org, Junichi Nomura <j-nomura@ce.jp.nec.com>, Thomas Gleixner <tglx@linutronix.de>, dyoung@redhat.com

+ hpa

On Mon, Apr 22, 2019 at 10:33:46PM +0800, Baoquan He wrote:
> On 04/19/19 at 01:36pm, Borislav Petkov wrote:
> > On Fri, Apr 19, 2019 at 01:28:01PM +0200, Borislav Petkov wrote:
> > > Read again what I said: "should all be passed through boot_params".
> > > Which means, boot_params should be extended with a field of a flag to
> > > say: "this is a kexec'ed kernel".
> > 
> > And by that I mean similar to the XLF_EFI_KEXEC mechanism. The first
> > kernel or kexec(1) should prepare the info needed by the kexec'ed
> > kernel.
> 
> We have set the loader type to '0x0D << 4' for kexec specifically, in both
> kexec_load and kexec_file_load. We can check this to identify if it's
> kexec-ed kernel or not.
> 
> Update patch with it?
> 
> static void *bzImage64_load(struct kimage *image, char *kernel,
>                             unsigned long kernel_len, char *initrd,
>                             unsigned long initrd_len, char *cmdline,
>                             unsigned long cmdline_len)
> {
> 
> 	...
> 	/* bootloader info. Do we need a separate ID for kexec kernel loader? */
>         params->hdr.type_of_loader = 0x0D << 4;

That's already documented in Documentation/x86/boot.txt

Field name:     type_of_loader
Type:           write (obligatory)
Offset/size:    0x210/1
Protocol:       2.00+

	...

        D  kexec-tools

And yes, the question in the code is still valid: do we need a separate ID.

I'd say no and we'll simply call 0xD all kernels loaded using a
kexec-type syscall.

IMO.

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.

_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec