[ARM] Bootstrap ILP32 on AArch64
a project by algraf
Updated about 6 years ago. 1 hackers ♥️.

Some customers are still stuck in a world of 32bit. On ARM64, we have two options for those poor folks:

1) Run applications in the legacy ARMv7 instruction set 2) Compile applications with 32bit, but for the new AArch64 instruction set. This is called ILP32.

The main reason option 1 is a bad idea is that some hardware is already dropping ARMv7 instruction set support. And there will be more to come.

So if we ever want to enable people to run code that is not 64bit safe on AArch64 platforms, we need to provide them with a way out. Hence we should bootstrap at least the bare minimum to enable them to compile their own (broken) code.

Beware that all of this is in a big flux. The interfaces (ABI, syscalls) are not yet set in stone.

Join this project

Looking for hackers with the skills:

arm ilp32 binutils kernel aarch64 obs openbuildservice

This project is part of:

Hack Week 12

Activity

  • about 10 years ago: a_faerber left this project.
  • about 10 years ago: a_faerber added keyword "obs" to this project.
  • about 10 years ago: a_faerber added keyword "openbuildservice" to this project.
  • about 10 years ago: a_faerber liked this project.
  • about 10 years ago: a_faerber joined this project.
  • about 10 years ago: algraf added keyword "arm" to this project.
  • about 10 years ago: algraf added keyword "ilp32" to this project.
  • about 10 years ago: algraf added keyword "binutils" to this project.
  • about 10 years ago: algraf added keyword "kernel" to this project.
  • about 10 years ago: algraf added keyword "aarch64" to this project.
  • about 10 years ago: algraf started this project.
  • about 10 years ago: algraf originated this project.


    • Comments

    Be the first to comment!

    Similar Projects

    early stage kdump support by mbrugger

    Project Description

    When we experience a early boot crash, we are not able to analyze the kernel dump, as user-space wasn't able to load the crash system. The idea is to make the crash system compiled into the host kernel (think of initramfs) so that we can create a kernel dump really early in the boot process.

    Goal for the Hackweeks

    1. Investigate if this is possible and the implications it would have (done in HW21)
    2. Hack up a PoC (done in HW22 and HW23)
    3. Prepare RFC series (giving it's only one week, we are entering wishful thinking territory here).

    update HW23

    • I was able to include the crash kernel into the kernel Image.
    • I'll need to find a way to load that from init/main.c:start_kernel() probably after kcsan_init()
    • I workaround for a smoke test was to hack kexec_file_load() systemcall which has two problems:
      1. My initramfs in the porduction kernel does not have a new enough kexec version, that's not a blocker but where the week ended
      2. As the crash kernel is part of init.data it will be already stale once I can call kexec_file_load() from user-space.

    The solution is probably to rewrite the POC so that the invocation can be done from init.text (that's my theory) but I'm not sure if I can reuse the kexec infrastructure in the kernel from there, which I rely on heavily.

    update HW24

    • Day1
      • rebased on v6.12 with no problems others then me breaking the config
      • setting up a new compilation and qemu/virtme env
      • getting desperate as nothing works that used to work
    • Day 2
      • getting to call the invocation of loading the early kernel from __init after kcsan_init()

    • Day 3

      • fix problem of memdup not being able to alloc so much memory... use 64K page sizes for now
      • code refactoring
      • I'm now able to load the crash kernel
      • When using virtme I can boot into the crash kernel, also it doesn't boot completely (major milestone!), crash in elfcorehdr_read_notes()

    • Day 4

      • crash systems crashes (no pun intended) in copy_old_mempage() link; will need to understand elfcorehdr...
      • call path vmcore_init() -> parse_crash_elf_headers() -> elfcorehdr_read() -> read_from_oldmem() -> copy_oldmem_page() -> copy_to_iter()

    • Day 5

      • hacking arch/arm64/kernel/crash_dump.c:copy_old_mempage() to see if crash system really starts. It does.
      • fun fact: retested with more reserved memory and with UEFI FW, host kernel crashes in init but directly starts the crash kernel, so it works (somehow) \o/

    • TODOs

      • fix elfcorehdr so that we actually can make use of all this...
      • test where in the boot __init() chain we can/should call kexec_early_dump()