cleonos/docs/stage26.md

Stage 26 - Kernel Builtin ELF Loader + Root Hello ELF

Goal

• Move elfloader from standalone user ELF into a kernel builtin command.
• Keep hello.elf as root-level user ELF test payload.

Implementation

• Removed standalone user app elfloader_main.c.
• Added kernel shell builtin command: elfloader [path].
  • Default target path: /hello.elf.
  • Builtin flow: fs_read -> elf64 inspect -> exec load -> entry call -> return status.
• Updated CMake ramdisk placement rules:
  • hello.elf -> /hello.elf
• Simplified user Rust library back to shared helper export (cleonos_rust_guarded_len).
• Added x86_64 exec stack bridge (clks_exec_call_on_stack_x86_64) so ELF entry runs on a dedicated execution stack instead of inheriting deep shell call stack.

Acceptance Criteria

• No elfloader.elf is generated or packed.
• Ramdisk root contains /hello.elf.
• In kernel shell:
  • elfloader loads and executes /hello.elf, then returns status.
  • elfloader /path/to/app.elf works for other absolute/relative paths.
• exec /shell/shell.elf can take foreground control without immediate stack-chain crash.

Build Targets

• make userapps
• make ramdisk
• make iso
• make run

QEMU Command

• make run

Debug Notes

• If elfloader reports file missing, check ramdisk root packaging for /hello.elf.
• If it reports invalid elf64, verify user app link script and ELF output format.
• If it reports exec failed, inspect EXEC channel logs for load/entry/return status.
• For long-running interactive ELF (such as shell.elf), no RUN RETURNED log is expected unless the app exits.