linux-kernel - Re: [RFC 0/3] extend kexec_file

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Message-Id: <7619c6f9-689e-f062-08d4-0d11a2df66ad@au.ibm.com>
Date:	Fri, 22 Jul 2016 08:53:41 +0800
From:	Jeremy Kerr <jeremy.kerr@....ibm.com>
To:	Thiago Jung Bauermann <bauerman@...ux.vnet.ibm.com>,
	Arnd Bergmann <arnd@...db.de>
Cc:	Russell King - ARM Linux <linux@...linux.org.uk>,
	Vivek Goyal <vgoyal@...hat.com>,
	Mark Rutland <mark.rutland@....com>,
	Stewart Smith <stewart@...ux.vnet.ibm.com>,
	Mimi Zohar <zohar@...ux.vnet.ibm.com>, bhe@...hat.com,
	linuxppc-dev@...ts.ozlabs.org, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	AKASHI Takahiro <takahiro.akashi@...aro.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Samuel Mendoza-Jonas <sam@...dozajonas.com>,
	Dave Young <dyoung@...hat.com>,
	linux-arm-kernel@...ts.infradead.org,
	Jeremy Kerr <jeremy.kerr@....ibm.com>,
	Michael Ellerman <michael@...erman.id.au>
Subject: Re: [RFC 0/3] extend kexec_file_load system call

Hi Thiago,

> So even if not ideal, the solution above is desirable for powerpc. We would 
> like to preserve the ability of allowing userspace to pass parameters to the 
> OS via the DTB, even if secure boot is enabled.
> 
> I would like to turn the above into a proposal:
> 
> Extend the syscall as shown in this RFC from Takahiro AKASHI, but instead of 
> accepting a complete DTB from userspace, the syscall accepts a DTB 
> containing only a /chosen node. If the DTB contains any other node, the 
> syscall fails with EINVAL. If the DTB contains any subnode in /chosen, or if 
> there's a compatible or device_type property in /chosen, the syscall fails 
> with EINVAL as well.

This works for me. We could even have it as just a DTB fragment that is
merged *at* the /chosen/ node of the kernel-device tree - so would not
contain a /chosen node itself, and it would be impossible to provide
nodes outside of /chosen. Either is fine.

Thanks!


Jeremy