linux-kernel - Re: [PATCH v2 0/6] kexec_file: Add buffer hand-over for the next kernel

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Date:	Wed, 17 Aug 2016 10:52:26 +0800
From:	Dave Young <dyoung@...hat.com>
To:	Thiago Jung Bauermann <bauerman@...ux.vnet.ibm.com>
Cc:	kexec@...ts.infradead.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Balbir Singh <bsingharora@...il.com>,
	Paul Mackerras <paulus@...ba.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	linux-ima-devel@...ts.sourceforge.net,
	Stewart Smith <stewart@...ux.vnet.ibm.com>,
	Baoquan He <bhe@...hat.com>,
	Michael Ellerman <mpe@...erman.id.au>, x86@...nel.org,
	Ingo Molnar <mingo@...hat.com>,
	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	Petko Manolov <petkan@...-labs.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Eric Richter <erichte@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	David Laight <David.Laight@...LAB.COM>,
	Eric Biederman <ebiederm@...ssion.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Samuel Mendoza-Jonas <sam@...dozajonas.com>,
	linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v2 0/6] kexec_file: Add buffer hand-over for the next
 kernel

On 08/13/16 at 12:18am, Thiago Jung Bauermann wrote:
> Hello,
> 
> This patch series implements a mechanism which allows the kernel to pass
> on a buffer to the kernel that will be kexec'd. This buffer is passed
> as a segment which is added to the kimage when it is being prepared
> by kexec_file_load.
> 
> How the second kernel is informed of this buffer is architecture-specific.
> On powerpc, this is done via the device tree, by checking
> the properties /chosen/linux,kexec-handover-buffer-start and
> /chosen/linux,kexec-handover-buffer-end, which is analogous to how the
> kernel finds the initrd.
> 
> This is needed because the Integrity Measurement Architecture subsystem
> needs to preserve its measurement list accross the kexec reboot. The
> following patch series for the IMA subsystem uses this feature for that
> purpose:
> 
> https://lists.infradead.org/pipermail/kexec/2016-August/016745.html
> 
> This is so that IMA can implement trusted boot support on the OpenPower
> platform, because on such systems an intermediary Linux instance running
> as part of the firmware is used to boot the target operating system via
> kexec. Using this mechanism, IMA on this intermediary instance can
> hand over to the target OS the measurements of the components that were
> used to boot it.
> 
> Because there could be additional measurement events between the
> kexec_file_load call and the actual reboot, IMA needs a way to update the
> buffer with those additional events before rebooting. One can minimize
> the interval between the kexec_file_load and the reboot syscalls, but as
> small as it can be, there is always the possibility that the measurement
> list will be out of date at the time of reboot.
> 
> To address this issue, this patch series also introduces
> kexec_update_segment, which allows a reboot notifier to change the
> contents of the image segment during the reboot process.
> 
> Patch 5 makes kimage_load_normal_segment and kexec_update_segment share
> code. It's not much code that they can share though, so I'm not sure if
> the result is actually better.
> 
> The last patch is not intended to be merged, it just demonstrates how
> this feature can be used.
> 
> This series applies on top of v5 of the "kexec_file_load implementation
> for PowerPC" patch series (which applies on top of v4.8-rc1):
> 
> https://lists.infradead.org/pipermail/kexec/2016-August/016843.html

I'm trying to review your patches, but seems I can not apply them
cleanly to mainline kernel or v4.8-rc1

Apply the kexec_file_load series failed as below on v4.8-rc1:

Applying: kexec_file: Allow arch-specific memory walking for
kexec_add_buffer
error: patch failed: include/linux/kexec.h:149
error: include/linux/kexec.h: patch does not apply
Patch failed at 0001 kexec_file: Allow arch-specific memory walking for
kexec_add_buffer
The copy of the patch that failed is found in: .git/rebase-apply/patch
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".

What is the order of your patch series of the three patchset?

[PATCH v2 0/2] extend kexec_file_load system call
[PATCH v5 00/13] kexec_file_load implementation for PowerPC
[PATCH v2 0/6] kexec_file: Add buffer hand-over for the next kernel

Do they depend on other patches?

Thanks
Dave