linux-kernel - [PATCH 0/9] kexec: add kexec_file

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Message-Id: <20170908031616.17916-1-takahiro.akashi@linaro.org>
Date:   Fri,  8 Sep 2017 12:16:07 +0900
From:   AKASHI Takahiro <takahiro.akashi@...aro.org>
To:     catalin.marinas@....com, will.deacon@....com,
        bauerman@...ux.vnet.ibm.com, dhowells@...hat.com,
        vgoyal@...hat.com, herbert@...dor.apana.org.au,
        davem@...emloft.net, akpm@...ux-foundation.org, mpe@...erman.id.au,
        dyoung@...hat.com, bhe@...hat.com, arnd@...db.de,
        ard.biesheuvel@...aro.org
Cc:     kexec@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org,
        AKASHI Takahiro <takahiro.akashi@...aro.org>
Subject: [PATCH 0/9] kexec: add kexec_file_load() support

This is the second round of implementing kexec_file_load() support
on arm64.[1]
Most of the code is based on kexec-tools (along with some kernel code
from x86, which also came from kexec-tools).


This patch series enables us to
  * load the kernel, Image, with kexec_file_load system call, and
  * optionally verify its signature at load time for trusted boot.

To load the kernel via kexec_file_load system call, a small change
is also needed to kexec-tools. See [2]. This enables '-s' option.

As we discussed a long time ago, users may not be allowed to specify
device-tree file of the 2nd kernel explicitly with kexec-tools, therefore
re-using the blob of the first kernel.

Regarding a signing method, we conform with x86 (or rather Microsoft?)
style of signing since the binary can also be seen as in PE format
(assuming that CONFIG_EFI is enabled).

    Powerpc is also going to support extended-file-attribute-based
    verification[3] with vmlinux, but arm64 doesn't for now partly
    because we don't have TPM-based IMA at this moment.

Accordingly, we can use the existing command, sbsign, to sign the kernel.

    $ sbsign --key ${KEY} --cert ${CERT} Image

Please note that it is totally up to the system what key/certificate is
used for signing, but one of easy ways to *try* this feature is to turn on
CONFIG_MODULE_SIG so that we can reuse certs/signing_key.pem as a signing
key, KEY and CERT above, for kernel.
(This also enables CONFIG_CRYPTO_SHA1 by default.)


Some concerns(or future works):
* Even if the kernel is configured with CONFIG_RANDOMIZE_BASE, the 2nd
  kernel won't be placed at a randomized address. We will have to
  add some boot code similar to efi-stub to implement the feature.
* While big-endian kernel can support kernel signing, I'm not sure that
  Image can be recognized as in PE format because x86 standard only
  defines little-endian-based format.
* IMA(and file extended attribute)-based kexec
* vmlinux support

  [1] http://git.linaro.org/people/takahiro.akashi/linux-aarch64.git
	branch:arm64/kexec_file
  [2] http://git.linaro.org/people/takahiro.akashi/kexec-tools.git
	branch:arm64/kexec_file
  [3] http://lkml.iu.edu//hypermail/linux/kernel/1707.0/03669.html


Changes in v2 (Sep 8, 2017)
* move core-header-related functions from crash_core.c to kexec_file.c
* drop hash-check code from purgatory
* modify purgatory asm to remove arch_kexec_apply_relocations_add()
* drop older kernel support
* drop vmlinux support (at least, for this series)

Patch #1 to #4 are all preparatory patches on generic side.
Patch #5 is purgatory code.
Patch #6 to #8 are common for enabling kexec_file_load.
Patch #9 is for 'Image' support.


AKASHI Takahiro (9):
  include: pe.h: remove message[] from mz header definition
  resource: add walk_system_ram_res_rev()
  kexec_file: factor out crashdump elf header function from x86
  asm-generic: add kexec_file_load system call to unistd.h
  arm64: kexec_file: create purgatory
  arm64: kexec_file: load initrd, device-tree and purgatory segments
  arm64: kexec_file: set up for crash dump adding elf core header
  arm64: enable KEXEC_FILE config
  arm64: kexec_file: add Image format support

 arch/arm64/Kconfig                     |  29 +++
 arch/arm64/Makefile                    |   1 +
 arch/arm64/include/asm/kexec.h         |  24 ++
 arch/arm64/include/asm/kexec_file.h    |  69 ++++++
 arch/arm64/kernel/Makefile             |   4 +-
 arch/arm64/kernel/kexec_image.c        | 106 +++++++++
 arch/arm64/kernel/machine_kexec_file.c | 413 +++++++++++++++++++++++++++++++++
 arch/arm64/purgatory/Makefile          |  24 ++
 arch/arm64/purgatory/entry.S           |  55 +++++
 arch/x86/kernel/crash.c                | 324 --------------------------
 include/linux/ioport.h                 |   3 +
 include/linux/kexec.h                  |  19 ++
 include/linux/pe.h                     |   2 +-
 include/uapi/asm-generic/unistd.h      |   4 +-
 kernel/kexec_file.c                    | 329 ++++++++++++++++++++++++++
 kernel/resource.c                      |  59 +++++
 16 files changed, 1138 insertions(+), 327 deletions(-)
 create mode 100644 arch/arm64/include/asm/kexec_file.h
 create mode 100644 arch/arm64/kernel/kexec_image.c
 create mode 100644 arch/arm64/kernel/machine_kexec_file.c
 create mode 100644 arch/arm64/purgatory/Makefile
 create mode 100644 arch/arm64/purgatory/entry.S

-- 
2.14.1