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

Palmer Dabbelt
2023-04-21T18:59:37Z

On Tue, 28 Mar 2023 21:53:23 PDT (-0700), alexghiti@rivosinc.com 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