From: Vivek Goyal <vgoyal@redhat.com>
To: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
AKASHI Takahiro <takahiro.akashi@linaro.org>,
dyoung@redhat.com, bhe@redhat.com, arnd@arndb.de,
kexec@lists.infradead.org, linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [RFC 0/3] extend kexec_file_load system call
Date: Tue, 12 Jul 2016 10:02:42 -0400 [thread overview]
Message-ID: <20160712140242.GA30181@redhat.com> (raw)
In-Reply-To: <2675986.6AfrV5PCe0@hactar>
On Tue, Jul 12, 2016 at 10:58:09AM -0300, Thiago Jung Bauermann wrote:
> Hello Eric,
>
> Am Dienstag, 12 Juli 2016, 08:25:48 schrieb Eric W. Biederman:
> > AKASHI Takahiro <takahiro.akashi@linaro.org> writes:
> > > Device tree blob must be passed to a second kernel on DTB-capable
> > > archs, like powerpc and arm64, but the current kernel interface
> > > lacks this support.
> > >
> > > This patch extends kexec_file_load system call by adding an extra
> > > argument to this syscall so that an arbitrary number of file descriptors
> > > can be handed out from user space to the kernel.
> > >
> > > See the background [1].
> > >
> > > Please note that the new interface looks quite similar to the current
> > > system call, but that it won't always mean that it provides the "binary
> > > compatibility."
> > >
> > > [1] http://lists.infradead.org/pipermail/kexec/2016-June/016276.html
> >
> > So this design is wrong. The kernel already has the device tree blob,
> > you should not be extracting it from the kernel munging it, and then
> > reinserting it in the kernel if you want signatures and everything to
> > pass.
> >
> > What x86 does is pass it's equivalent of the device tree blob from one
> > kernel to another directly and behind the scenes. It does not go
> > through userspace for this.
> >
> > Until a persuasive case can be made for going around the kernel and
> > probably adding a feature (like code execution) that can be used to
> > defeat the signature scheme I am going to nack this.
>
> There are situations where userspace needs to change things in the device
> tree to be used by the next kernel.
>
> For example, Petitboot (the boot loader used in OpenPOWER machines) is a
> userspace application running in an intermediary Linux instance and uses
> kexec to load the target OS. It has to modify the device tree that will be
> used by the next kernel so that the next kernel uses the same console that
> petitboot was configured to use (i.e., set the /chosen/linux,stdout-path
> property). It also modifies the device tree to allow the kernel to inherit
> Petitboot's Openfirmware framebuffer.
Can some of this be done with the help of kernel command line options for
second kernel?
Vivek
next prev parent reply other threads:[~2016-07-12 14:02 UTC|newest]
Thread overview: 87+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-12 1:41 [RFC 0/3] extend kexec_file_load system call AKASHI Takahiro
2016-07-12 1:41 ` [RFC 1/3] syscall: add kexec_file_load to generic unistd.h AKASHI Takahiro
2016-07-12 1:42 ` [RFC 2/3] kexec: add dtb info to struct kimage AKASHI Takahiro
2016-07-12 1:42 ` [RFC 3/3] kexec: extend kexec_file_load system call AKASHI Takahiro
2016-07-15 13:09 ` Vivek Goyal
2016-07-15 13:19 ` Mark Rutland
2016-07-18 2:30 ` Dave Young
2016-07-18 10:07 ` Mark Rutland
2016-07-19 0:55 ` Dave Young
2016-07-19 10:52 ` Mark Rutland
2016-07-19 12:24 ` Vivek Goyal
2016-07-19 12:47 ` Mark Rutland
2016-07-19 13:26 ` Vivek Goyal
2016-07-20 11:41 ` David Laight
2016-07-21 9:21 ` Russell King - ARM Linux
2016-07-18 2:33 ` Dave Young
2016-07-27 0:24 ` [PATCH v2 " Thiago Jung Bauermann
2016-08-05 20:46 ` Thiago Jung Bauermann
2016-07-12 13:25 ` [RFC 0/3] " Eric W. Biederman
2016-07-12 13:58 ` Thiago Jung Bauermann
2016-07-12 14:02 ` Vivek Goyal [this message]
2016-07-12 23:45 ` Stewart Smith
2016-07-13 13:27 ` Vivek Goyal
2016-07-12 14:02 ` Arnd Bergmann
2016-07-12 14:18 ` Vivek Goyal
2016-07-12 14:24 ` Arnd Bergmann
2016-07-12 14:50 ` Mark Rutland
2016-07-13 2:36 ` Dave Young
2016-07-13 8:01 ` Arnd Bergmann
2016-07-13 8:23 ` Stewart Smith
2016-07-13 9:41 ` Mark Rutland
2016-07-13 13:13 ` Arnd Bergmann
2016-07-13 18:45 ` Thiago Jung Bauermann
2016-07-13 19:59 ` Arnd Bergmann
2016-07-14 2:18 ` Thiago Jung Bauermann
2016-07-14 8:29 ` Arnd Bergmann
2016-07-15 1:44 ` Thiago Jung Bauermann
2016-07-15 7:31 ` Arnd Bergmann
2016-07-15 13:26 ` Vivek Goyal
2016-07-15 13:33 ` Mark Rutland
2016-07-15 15:29 ` Thiago Jung Bauermann
2016-07-15 15:47 ` Mark Rutland
2016-07-15 13:42 ` Russell King - ARM Linux
2016-07-15 20:26 ` Arnd Bergmann
2016-07-15 21:03 ` Thiago Jung Bauermann
2016-07-22 0:09 ` Thiago Jung Bauermann
2016-07-22 0:53 ` Jeremy Kerr
2016-07-22 2:54 ` Michael Ellerman
2016-07-22 20:41 ` Thiago Jung Bauermann
2016-07-15 8:49 ` Russell King - ARM Linux
2016-07-15 13:03 ` Vivek Goyal
2016-07-13 9:34 ` Mark Rutland
2016-07-13 17:38 ` AKASHI Takahiro
2016-07-13 17:58 ` Mark Rutland
2016-07-13 19:57 ` Arnd Bergmann
2016-07-14 12:42 ` Mark Rutland
2016-07-14 1:54 ` Dave Young
2016-07-14 1:50 ` Dave Young
2016-07-12 16:25 ` Thiago Jung Bauermann
2016-07-12 20:58 ` Petr Tesarik
2016-07-12 21:22 ` Eric W. Biederman
2016-07-12 21:36 ` Eric W. Biederman
2016-07-12 21:53 ` Petr Tesarik
2016-07-12 22:18 ` Russell King - ARM Linux
2016-07-13 4:59 ` Stewart Smith
2016-07-13 7:36 ` Russell King - ARM Linux
2016-07-13 7:47 ` Ard Biesheuvel
2016-07-13 8:09 ` Russell King - ARM Linux
2016-07-13 8:20 ` Stewart Smith
2016-07-13 7:55 ` Stewart Smith
2016-07-13 8:26 ` Russell King - ARM Linux
2016-07-13 8:36 ` Dave Young
2016-07-13 8:57 ` Petr Tesarik
2016-07-13 13:03 ` Vivek Goyal
2016-07-13 17:40 ` Russell King - ARM Linux
2016-07-13 18:22 ` Vivek Goyal
2016-07-18 12:46 ` Balbir Singh
2016-07-18 13:26 ` Vivek Goyal
2016-07-18 13:38 ` Vivek Goyal
2016-07-20 3:45 ` Balbir Singh
2016-07-20 8:35 ` Russell King - ARM Linux
2016-07-20 11:12 ` Arnd Bergmann
2016-07-20 15:50 ` Thiago Jung Bauermann
2016-07-20 12:46 ` Vivek Goyal
2016-07-20 12:27 ` Vivek Goyal
2016-07-12 23:41 ` Stewart Smith
2016-07-13 13:25 ` Vivek Goyal
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