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Subject: Re: [PATCH v6 0/3] Introduce 64b relocatable kernel
To:     Michael Ellerman <mpe@ellerman.id.au>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
        linux-riscv@lists.infradead.org
References: <20210518101252.1484465-1-alex@ghiti.fr>
From:   Alex Ghiti <alex@ghiti.fr>
Message-ID: <8512c6b0-3dff-5485-b5d8-638044594973@ghiti.fr>
Date:   Thu, 17 Jun 2021 15:33:48 +0200
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Le 18/05/2021 ? 12:12, Alexandre Ghiti a ?crit?:
> After multiple attempts, this patchset is now based on the fact that the
> 64b kernel mapping was moved outside the linear mapping.
> 
> The first patch allows to build relocatable kernels but is not selected
> by default. That patch should ease KASLR implementation a lot.
> The second and third patches take advantage of an already existing powerpc
> script that checks relocations at compile-time, and uses it for riscv.

@Palmer, any thought about that? There are no users for now, do you want 
to wait for a KASLR implementation to use it before merging this? If so, 
I can work on a KASLR implementation based on older implementation from 
Zong.

Thanks,

> 
> This patchset was tested on:
> 
> * kernel:
> - rv32: OK
> - rv64 with RELOCATABLE: OK and checked that "suspicious" relocations are caught.
> - rv64 without RELOCATABLE: OK
> - powerpc: build only and checked that "suspicious" relocations are caught.
>                                                                                   
> * xipkernel:
> - rv32: build only
> - rv64: OK
> 
> * nommukernel:
> - rv64: build only
> 
> Changes in v6:
>    * Remove the kernel move to vmalloc zone
>    * Rebased on top of for-next
>    * Remove relocatable property from 32b kernel as the kernel is mapped in
>      the linear mapping and would then need to be copied physically too
>    * CONFIG_RELOCATABLE depends on !XIP_KERNEL
>    * Remove Reviewed-by from first patch as it changed a bit
> 
> Changes in v5:
>    * Add "static __init" to create_kernel_page_table function as reported by
>      Kbuild test robot
>    * Add reviewed-by from Zong
>    * Rebase onto v5.7
> 
> Changes in v4:
>    * Fix BPF region that overlapped with kernel's as suggested by Zong
>    * Fix end of module region that could be larger than 2GB as suggested by Zong
>    * Fix the size of the vm area reserved for the kernel as we could lose
>      PMD_SIZE if the size was already aligned on PMD_SIZE
>    * Split compile time relocations check patch into 2 patches as suggested by Anup
>    * Applied Reviewed-by from Zong and Anup
> 
> Changes in v3:
>    * Move kernel mapping to vmalloc
> 
> Changes in v2:
>    * Make RELOCATABLE depend on MMU as suggested by Anup
>    * Rename kernel_load_addr into kernel_virt_addr as suggested by Anup
>    * Use __pa_symbol instead of __pa, as suggested by Zong
>    * Rebased on top of v5.6-rc3
>    * Tested with sv48 patchset
>    * Add Reviewed/Tested-by from Zong and Anup
> 
> Alexandre Ghiti (3):
>    riscv: Introduce CONFIG_RELOCATABLE
>    powerpc: Move script to check relocations at compile time in scripts/
>    riscv: Check relocations at compile time
> 
>   arch/powerpc/tools/relocs_check.sh | 18 ++--------
>   arch/riscv/Kconfig                 | 12 +++++++
>   arch/riscv/Makefile                |  5 ++-
>   arch/riscv/Makefile.postlink       | 36 ++++++++++++++++++++
>   arch/riscv/kernel/vmlinux.lds.S    |  6 ++++
>   arch/riscv/mm/Makefile             |  4 +++
>   arch/riscv/mm/init.c               | 53 +++++++++++++++++++++++++++++-
>   arch/riscv/tools/relocs_check.sh   | 26 +++++++++++++++
>   scripts/relocs_check.sh            | 20 +++++++++++
>   9 files changed, 162 insertions(+), 18 deletions(-)
>   create mode 100644 arch/riscv/Makefile.postlink
>   create mode 100755 arch/riscv/tools/relocs_check.sh
>   create mode 100755 scripts/relocs_check.sh
>