linux-kernel - Re: [PATCH 00/11] kexec_file: Clean up purgatory load

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Date:   Fri, 9 Mar 2018 13:33:48 +0800
From:   Dave Young <dyoung@...hat.com>
To:     Philipp Rudo <prudo@...ux.vnet.ibm.com>
Cc:     kexec@...ts.infradead.org, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Eric Biederman <ebiederm@...ssion.com>,
        Vivek Goyal <vgoyal@...hat.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Thiago Jung Bauermann <bauerman@...ux.vnet.ibm.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>, x86@...nel.org,
        AKASHI Takahiro <takahiro.akashi@...aro.org>
Subject: Re: [PATCH 00/11] kexec_file: Clean up purgatory load

On 03/09/18 at 01:19pm, Dave Young wrote:
> Hi Philipp,
> On 02/26/18 at 04:16pm, Philipp Rudo wrote:
> > 
> > Hi everybody
> > 
> > following the discussion with Dave and AKASHI, here are the common code
> > patches extracted from my recent patch set (Add kexec_file_load support to
> > s390) [1]. The patches were extracted to allow upstream integration together
> > with AKASHI's common code patches before the arch code gets adjusted to the
> > new base.
> > 
> > The reason for this series is to prepare common code for adding
> > kexec_file_load to s390 as well as cleaning up the mis-use of the sh_offset
> > field during purgatory load. In detail this series contains:
> > 
> > Patch #1&2: Minor cleanups/fixes.
> > 
> > Patch #3-9: Clean up the purgatory load/relocation code. Especially remove
> > the mis-use of the purgatory_info->sechdrs->sh_offset field, currently
> > holding a pointer into either kexec_purgatory (ro) or purgatory_buf (rw)
> > depending on the section. With these patches the section address will be
> > calculated verbosely and sh_offset will contain the offset of the section
> > in the stripped purgatory binary (purgatory_buf).
> > 
> > Patch #10: Allows architectures to set the purgatory load address. This
> > patch is important for s390 as the kernel and purgatory have to be loaded
> > to fixed addresses. In current code this is impossible as the purgatory
> > load is opaque to the architecture.
> > 
> > Patch #11: Moves x86 purgatories sha implementation to common lib/
> > directory to allow reuse in other architectures.
> > 
> > The patches apply to v4.16-rc3. There are no changes compared to [1] (all
> > requested changes only affected s390 code). Please note that I had to touch
> > arch code for x86 and power a little. In theory this should not change the
> > behavior but I don't have a way to test it. Cross-compiling with
> > defconfig [2] works fine for both.
> > 
> > Thanks
> > Philipp
> > 
> > [1] http://lists.infradead.org/pipermail/kexec/2018-February/019926.html
> > [2] On x86 with the orc unwinder and stack validation turned off. objtool
> >     SEGFAULTs on s390...
> > 
> > Philipp Rudo (11):
> >   kexec_file: Silence compile warnings
> >   kexec_file: Remove checks in kexec_purgatory_load
> >   kexec_file: Make purgatory_info->ehdr const
> >   kexec_file: Search symbols in read-only kexec_purgatory
> >   kexec_file: Use read-only sections in arch_kexec_apply_relocations*
> >   kexec_file: Split up __kexec_load_puragory
> >   kexec_file: Simplify kexec_purgatory_setup_sechdrs 1
> >   kexec_file: Simplify kexec_purgatory_setup_sechdrs 2
> >   kexec_file: Remove mis-use of sh_offset field
> >   kexec_file: Allow archs to set purgatory load address
> >   kexec_file: Move purgatories sha256 to common code
> > 
> >  arch/powerpc/kernel/kexec_elf_64.c             |   9 +-
> >  arch/x86/kernel/kexec-bzimage64.c              |   8 +-
> >  arch/x86/kernel/machine_kexec_64.c             |  66 ++---
> >  arch/x86/purgatory/Makefile                    |   3 +
> >  arch/x86/purgatory/purgatory.c                 |   2 +-
> >  include/linux/kexec.h                          |  38 +--
> >  {arch/x86/purgatory => include/linux}/sha256.h |  10 +-
> >  kernel/kexec_file.c                            | 375 ++++++++++++-------------
> >  {arch/x86/purgatory => lib}/sha256.c           |   4 +-
> >  9 files changed, 244 insertions(+), 271 deletions(-)
> >  rename {arch/x86/purgatory => include/linux}/sha256.h (63%)
> >  rename {arch/x86/purgatory => lib}/sha256.c (99%)
> > 
> > -- 
> > 2.13.5
> > 
> 
> I did a test on x86, but it failed:
> [   15.636489] kexec: Undefined symbol: memcpy
> [   15.636496] kexec-bzImage64: Loading purgatory failed
> [   33.603356] kexec: Undefined symbol: memcpy
> [   33.603362] kexec-bzImage64: Loading purgatory failed
> 
> I think this relates to the sha256 splitting patch.
> 
> After reverting the sha256 patch (the last one), rebuilt a kernel but it still
> failed to load:
> 
> # kexec -d -s -l /home/dyoung/git/linux-x86/sign/bzImage.signed 
> Try gzip decompression.
> Try LZMA decompression.
> lzma_decompress_file: read on /home/dyoung/git/linux-x86/sign/bzImage.signed of 65536 bytes failed

Oops, this lzma error message should be not harmful, actually kernel should
have been loaded, I will do more tests anyway.

> 
> Thanks
> Dave