Re: [PATCH 00/19] PBL: Add PBL ELF loading support with dynamic relocations

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

Hi,

On 1/5/26 12:26 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.
> 
> This series also marks my start into AI assisted programming as you can
> see in the Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
> and 🤖 Generated with [Claude Code](https://claude.com/claude-code)
> tags. Without it I wouldn't have started this series during my xmas
> break, but with it it was actually quite fun to do; it felt like having
> a programming team which I just had to delegate new tasks to while
> having fun with my family myself ;)

Did you do size comparisons to determine how much this series affects
binary size? I found that compressing every segment separately resulted
in a smaller binary size even after addition of ELF parsing to PBL, but
I used a purpose-built ELF loader unlike to what you did here.

Cheers,
Ahmad

> 
> Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> ---
> Sascha Hauer (19):
>       elf: Use memcmp to make suitable for PBL
>       elf: build for PBL as well
>       elf: add dynamic relocation support
>       ARM: implement elf_apply_relocations() for ELF relocation support
>       riscv: implement elf_apply_relocations() for ELF relocation support
>       elf: implement elf_load_inplace()
>       elf: create elf_open_binary_into()
>       Makefile: add barebox.elf build target
>       PBL: allow to link ELF image into PBL
>       mmu: add MAP_CACHED_RO mapping type
>       mmu: introduce pbl_remap_range()
>       ARM: use relative jumps in exception table
>       ARM: exceptions: make in-binary exception table const
>       ARM: linker script: create separate PT_LOAD segments for text, rodata, and data
>       ARM: link ELF image into PBL
>       ARM: PBL: setup MMU with proper permissions from ELF segments
>       riscv: link ELF image into PBL
>       riscv: linker script: create separate PT_LOAD segments for text, rodata, and data
>       riscv: add ELF segment-based memory protection with MMU
> 
>  Makefile                           |  16 +-
>  arch/arm/Kconfig                   |   2 +
>  arch/arm/cpu/exceptions_32.S       |  54 +++---
>  arch/arm/cpu/interrupts_32.c       |  41 +++-
>  arch/arm/cpu/mmu-common.c          |  66 +------
>  arch/arm/cpu/mmu-common.h          |   3 +-
>  arch/arm/cpu/mmu_32.c              |  19 +-
>  arch/arm/cpu/mmu_64.c              |  10 +-
>  arch/arm/cpu/no-mmu.c              |  11 +-
>  arch/arm/cpu/start.c               |   4 -
>  arch/arm/cpu/uncompress.c          |  46 ++++-
>  arch/arm/include/asm/barebox-arm.h |   4 +-
>  arch/arm/include/asm/barebox.lds.h |  14 +-
>  arch/arm/include/asm/elf.h         |  11 ++
>  arch/arm/include/asm/sections.h    |   1 +
>  arch/arm/lib/pbl.lds.S             |   8 +-
>  arch/arm/lib32/Makefile            |   1 +
>  arch/arm/lib32/barebox.lds.S       |  39 ++--
>  arch/arm/lib32/elf_reloc.c         | 105 ++++++++++
>  arch/arm/lib64/Makefile            |   1 +
>  arch/arm/lib64/barebox.lds.S       |  31 ++-
>  arch/arm/lib64/elf_reloc.c         | 105 ++++++++++
>  arch/riscv/Kconfig                 |  18 ++
>  arch/riscv/Kconfig.socs            |   1 -
>  arch/riscv/boot/start.c            |   4 -
>  arch/riscv/boot/uncompress.c       |  41 +++-
>  arch/riscv/cpu/Makefile            |   1 +
>  arch/riscv/cpu/mmu.c               | 386 +++++++++++++++++++++++++++++++++++++
>  arch/riscv/cpu/mmu.h               | 144 ++++++++++++++
>  arch/riscv/include/asm/asm.h       |   3 +-
>  arch/riscv/include/asm/mmu.h       |  44 +++++
>  arch/riscv/lib/Makefile            |   1 +
>  arch/riscv/lib/barebox.lds.S       |  38 ++--
>  arch/riscv/lib/elf_reloc.c         | 212 ++++++++++++++++++++
>  common/Makefile                    |   2 +-
>  common/elf.c                       | 367 +++++++++++++++++++++++++++++++++--
>  images/Makefile                    |  18 +-
>  images/piggy.S                     |   4 +
>  include/elf.h                      |  62 ++++++
>  include/mmu.h                      |  12 +-
>  include/pbl/mmu.h                  |  29 +++
>  lib/Makefile                       |   1 +
>  lib/elf_reloc.c                    |  15 ++
>  pbl/Kconfig                        |   8 +
>  pbl/Makefile                       |   1 +
>  pbl/mmu.c                          | 111 +++++++++++
>  scripts/prelink-riscv.inc          |   9 +-
>  47 files changed, 1922 insertions(+), 202 deletions(-)
> ---
> base-commit: e2d7e032281158b54541392b4d8108de204137a1
> change-id: 20251227-pbl-load-elf-cb4cb0ceb7d8
> 
> Best regards,

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