linux-kernel - Re: [PATCH v5 0/6] implement KASLR for powerpc/fsl

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Message-ID: <f91c90fde203ed87dcf206e795ee55ed67b5f641.camel@buserror.net>
Date:   Wed, 15 Apr 2020 14:31:38 -0500
From:   Scott Wood <oss@...error.net>
To:     Jason Yan <yanaijie@...wei.com>, mpe@...erman.id.au,
        linuxppc-dev@...ts.ozlabs.org, diana.craciun@....com,
        christophe.leroy@....fr, benh@...nel.crashing.org,
        paulus@...ba.org, npiggin@...il.com, keescook@...omium.org,
        kernel-hardening@...ts.openwall.com
Cc:     linux-kernel@...r.kernel.org, zhaohongjiang@...wei.com,
        dja@...ens.net
Subject: Re: [PATCH v5 0/6] implement KASLR for powerpc/fsl_booke/64

On Mon, 2020-03-30 at 10:20 +0800, Jason Yan wrote:
> This is a try to implement KASLR for Freescale BookE64 which is based on
> my earlier implementation for Freescale BookE32:
> 
https://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=131718&state=*
> 
> The implementation for Freescale BookE64 is similar as BookE32. One
> difference is that Freescale BookE64 set up a TLB mapping of 1G during
> booting. Another difference is that ppc64 needs the kernel to be
> 64K-aligned. So we can randomize the kernel in this 1G mapping and make
> it 64K-aligned. This can save some code to creat another TLB map at
> early boot. The disadvantage is that we only have about 1G/64K = 16384
> slots to put the kernel in.
> 
>     KERNELBASE
> 
>           64K                     |--> kernel <--|
>            |                      |              |
>         +--+--+--+    +--+--+--+--+--+--+--+--+--+    +--+--+
>         |  |  |  |....|  |  |  |  |  |  |  |  |  |....|  |  |
>         +--+--+--+    +--+--+--+--+--+--+--+--+--+    +--+--+
>         |                         |                        1G
>         |----->   offset    <-----|
> 
>                               kernstart_virt_addr
> 
> I'm not sure if the slot numbers is enough or the design has any
> defects. If you have some better ideas, I would be happy to hear that.
> 
> Thank you all.
> 
> v4->v5:
>   Fix "-Werror=maybe-uninitialized" compile error.
>   Fix typo "similar as" -> "similar to".
> v3->v4:
>   Do not define __kaslr_offset as a fixed symbol. Reference __run_at_load
> and
>     __kaslr_offset by symbol instead of magic offsets.
>   Use IS_ENABLED(CONFIG_PPC32) instead of #ifdef CONFIG_PPC32.
>   Change kaslr-booke32 to kaslr-booke in index.rst
>   Switch some instructions to 64-bit.
> v2->v3:
>   Fix build error when KASLR is disabled.
> v1->v2:
>   Add __kaslr_offset for the secondary cpu boot up.
> 
> Jason Yan (6):
>   powerpc/fsl_booke/kaslr: refactor kaslr_legal_offset() and
>     kaslr_early_init()
>   powerpc/fsl_booke/64: introduce reloc_kernel_entry() helper
>   powerpc/fsl_booke/64: implement KASLR for fsl_booke64
>   powerpc/fsl_booke/64: do not clear the BSS for the second pass
>   powerpc/fsl_booke/64: clear the original kernel if randomized
>   powerpc/fsl_booke/kaslr: rename kaslr-booke32.rst to kaslr-booke.rst
>     and add 64bit part
> 
>  Documentation/powerpc/index.rst               |  2 +-
>  .../{kaslr-booke32.rst => kaslr-booke.rst}    | 35 ++++++-
>  arch/powerpc/Kconfig                          |  2 +-
>  arch/powerpc/kernel/exceptions-64e.S          | 23 +++++
>  arch/powerpc/kernel/head_64.S                 | 13 +++
>  arch/powerpc/kernel/setup_64.c                |  3 +
>  arch/powerpc/mm/mmu_decl.h                    | 23 +++--
>  arch/powerpc/mm/nohash/kaslr_booke.c          | 91 +++++++++++++------
>  8 files changed, 147 insertions(+), 45 deletions(-)
>  rename Documentation/powerpc/{kaslr-booke32.rst => kaslr-booke.rst} (59%)
> 

Acked-by: Scott Wood <oss@...error.net>

-Scott