Re: [PATCH v9 0/6] Introduce 64b relocatable kernel

[Palmer Dabbelt]

On Tue, 28 Mar 2023 21:53:23 PDT (-0700), alexghiti@xxxxxxxxxxxx wrote:
> 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 is a requirement for KASLR.
> The second and third patches take advantage of an already existing powerpc
> script that checks relocations at compile-time, and uses it for riscv.
>
> This patchset is rebased on top of:
>
> riscv: Use PUD/P4D/PGD pages for the linear mapping
> (https://patchwork.kernel.org/project/linux-riscv/list/?series=733603)
> base-commit-tag: v6.3-rc1

The QEMU CI has some way to say "this depends on an un-merged patch set 
sent as $MESSAGE_ID", not sure if that's a b4-ism but it's a bit less 
confusing.

I merged this on top of the pre-merge hugepage linear mapping changes, 
it's on for-next.

> Changes in v9:
>   * Fix gcc/llvm compilation errors by adding patch 1, thanks to Bjorn
>   * Move a patch to move rela.dyn outside of init (patch 2): it is a
>     separate patch to clearly explain why
>   * To effectively move rela.dyn to init, we need to add patch 6: separate patch since we may be
>     able at some point to revert (along with patch 2).
>   * Add a lot of orphan sections to the linker script
>
> Changes in v8:
>   * Fix UEFI boot by moving rela.dyn section into the data so that PE/COFF
>     loader actually copies the relocations too
>   * Fix check that used PGDIR instead of PUD which was not correct
>     for sv48 and sv57
>   * Fix PE/COFF header data size definition as it led to size of 0
>
> Changes in v7:
>   * Rebase on top of v5.15
>   * Fix LDFLAGS_vmlinux which was overriden when CONFIG_DYNAMIC_FTRACE was
>     set
>   * Make relocate_kernel static
>   * Add Ack from Michael
>
> 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 (6):
>   riscv: Prepare EFI header for relocatable kernels
>   riscv: Move .rela.dyn outside of init to avoid empty relocations
>   riscv: Introduce CONFIG_RELOCATABLE
>   powerpc: Move script to check relocations at compile time in scripts/
>   riscv: Check relocations at compile time
>   riscv: Use --emit-relocs in order to move .rela.dyn in init
>
>  arch/powerpc/tools/relocs_check.sh  | 18 ++--------
>  arch/riscv/Kconfig                  | 14 ++++++++
>  arch/riscv/Makefile                 |  7 ++--
>  arch/riscv/Makefile.postlink        | 49 ++++++++++++++++++++++++++
>  arch/riscv/boot/Makefile            |  7 ++++
>  arch/riscv/include/asm/set_memory.h |  3 ++
>  arch/riscv/kernel/efi-header.S      | 19 ++++++++--
>  arch/riscv/kernel/vmlinux.lds.S     | 26 ++++++++++----
>  arch/riscv/mm/Makefile              |  4 +++
>  arch/riscv/mm/init.c                | 54 ++++++++++++++++++++++++++++-
>  arch/riscv/tools/relocs_check.sh    | 26 ++++++++++++++
>  scripts/relocs_check.sh             | 20 +++++++++++
>  12 files changed, 218 insertions(+), 29 deletions(-)
>  create mode 100644 arch/riscv/Makefile.postlink
>  create mode 100755 arch/riscv/tools/relocs_check.sh
>  create mode 100755 scripts/relocs_check.sh