Re: [PATCH v4 00/22] PBL: Add PBL ELF loading support with dynamic relocations

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Hello Sascha,

On 1/14/26 1:14 PM, Sascha Hauer wrote:
> Until now we linked the raw barebox proper binary into the PBL which
> comes with a number of disadvantages. We rely on self-modifying code
> to in barebox proper (relocate_to_current_adr()) and have no initialized
> bss segment (setup_c()). Also we can only mark the .text and .rodata as
> readonly during runtime of barebox proper.
> 
> This series overcomes this by linking a ELF image into the PBL. This
> image is properly layed out, linked and initialized in the PBL. With
> this barebox proper has a proper C environment and text/rodata
> protection from the start.
> 
> As a bonus this series also adds initial MMU support for RISCV, also
> based on loading the ELF image and configuring the MMU from the PBL.
> 
> I lost track about the review feedback for v1, partly because I asked
> Claude to integrate the review feedback for me, which it did, but not
> completely. Nevertheless I think this series has enough changes for now
> so that it deserves a second look.
> 
> What I didn't care about yet is that we found out that neither ARM nor
> RiscV use any absolute relocations, so we might be able to remove
> support for them, make sure these are not emitted during compile time,
> or properly test/fix them when we discover that they are indeed needed.

I am done with my review, so as far as I am concerned, this series can
go in with the minor points mentioned addressed.

Thanks,
Ahmad


> 
> Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> ---
> Changes in v4:
> - remove --remove-section=.note.gnu.build-id, catched by
>   --remove-section=.note*
> - actually use __image_* in remap_range_end_sans_image()
> - drop pbl_remap_range in favor of remap_range()
> - drop duplicate ELF entry point pr_debug()
> - add static inline wrapper for pbl_mmu_setup_from_elf()
> - reorder segments
> - make dynamic section RO
> - introduce elf_for_each_segment()
> - Use lowest vaddr segment for base address
> - Link to v3: https://lore.barebox.org/20260108-pbl-load-elf-v3-0-e28c931fc179@pengutronix.de
> 
> Changes in v3:
> - integrate Ahmads feedback
> - cleanup barebox proper entry
> - add missing "ax" flag to ARM exception table, and let linker do the
>   fixup
> - Link to v2: https://lore.barebox.org/20260106-pbl-load-elf-v2-0-487bc760f045@pengutronix.de
> 
> Changes in v2:
> - rebased on Ahmads patches and with it reused existing relocate_image()
> - hopefully integrated all feedback for v1
> - Link to v1: https://lore.barebox.org/20260105-pbl-load-elf-v1-0-e97853f98232@pengutronix.de
> 
> ---
> Sascha Hauer (22):
>       Makefile.compiler: add objcopy-option
>       elf: only accept images matching the native ELF_CLASS
>       elf: build for PBL as well
>       elf: add elf segment iterator
>       elf: add dynamic relocation support
>       ARM: implement elf_apply_relocations() for ELF relocation support
>       riscv: define generic relocate_image
>       riscv: implement elf_apply_relocations() for ELF relocation support
>       elf: implement elf_load_inplace()
>       elf: create elf_open_binary_into()
>       Makefile: add vmbarebox build target
>       PBL: allow to link ELF image into PBL
>       mmu: add MAP_CACHED_RO mapping type
>       ARM: drop arm_fixup_vectors()
>       ARM: linker script: create separate PT_LOAD segments for text, rodata, and data
>       ARM: link ELF image into PBL
>       ARM: cleanup barebox proper entry
>       ARM: PBL: setup MMU with proper permissions from ELF segments
>       riscv: linker script: create separate PT_LOAD segments for text, rodata, and data
>       riscv: link ELF image into PBL
>       riscv: Allwinner D1: Drop M-Mode
>       riscv: add ELF segment-based memory protection with MMU
> 
>  Makefile                           |  14 +-
>  arch/arm/Kconfig                   |   1 +
>  arch/arm/cpu/exceptions_32.S       |  54 +----
>  arch/arm/cpu/interrupts_32.c       |   5 +-
>  arch/arm/cpu/mmu-common.c          |  31 ++-
>  arch/arm/cpu/mmu-common.h          |   3 +-
>  arch/arm/cpu/mmu_32.c              |   6 +-
>  arch/arm/cpu/mmu_64.c              |   2 +-
>  arch/arm/cpu/no-mmu.c              |   2 -
>  arch/arm/cpu/start.c               |  22 +-
>  arch/arm/cpu/uncompress.c          |  34 ++-
>  arch/arm/include/asm/barebox-arm.h |   4 -
>  arch/arm/include/asm/elf.h         |   7 +
>  arch/arm/lib32/barebox.lds.S       |  42 ++--
>  arch/arm/lib32/reloc.c             |  19 ++
>  arch/arm/lib64/barebox.lds.S       |  38 ++--
>  arch/arm/lib64/reloc.c             |  21 +-
>  arch/riscv/Kconfig                 |  18 ++
>  arch/riscv/Kconfig.socs            |   1 -
>  arch/riscv/boot/start.c            |  19 +-
>  arch/riscv/boot/uncompress.c       |  34 ++-
>  arch/riscv/cpu/Makefile            |   1 +
>  arch/riscv/cpu/mmu.c               | 354 +++++++++++++++++++++++++++++
>  arch/riscv/cpu/mmu.h               | 120 ++++++++++
>  arch/riscv/include/asm/asm.h       |   3 +-
>  arch/riscv/include/asm/mmu.h       |  36 +++
>  arch/riscv/lib/barebox.lds.S       |  45 ++--
>  arch/riscv/lib/reloc.c             |  43 ++--
>  common/Makefile                    |   2 +-
>  common/elf.c                       | 446 +++++++++++++++++++++++++++++++++++--
>  include/elf.h                      |  79 +++++++
>  include/mmu.h                      |   3 +-
>  include/pbl/mmu.h                  |  38 ++++
>  pbl/Kconfig                        |   9 +
>  pbl/Makefile                       |   1 +
>  pbl/mmu.c                          | 107 +++++++++
>  scripts/Makefile.compiler          |   5 +
>  37 files changed, 1452 insertions(+), 217 deletions(-)
> ---
> base-commit: 2f99ee71fb44dc60b60d234fb38e0b3c6932f02b
> change-id: 20251227-pbl-load-elf-cb4cb0ceb7d8
> 
> Best regards,

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