Discussion on x86_64-unknown-none-hermitkernel target

[haraldh]

Followup discussion for

@haraldh I thought a little bit about your request. The main issue is that our llvm target is also defined in the spec file (see https://github.com/rust-lang/rust/blob/master/compiler/rustc_target/src/spec/x86_64_unknown_none_hermitkernel.rs#L14). This is used to define our kernel as standalone kernel (https://github.com/llvm/llvm-project/blob/e356027016c6365b3d8924f54c33e2c63d931492/llvm/include/llvm/MC/MCELFObjectWriter.h#L76-L77). In our case, we develop a library operating systems and everything is linked to one single boot image. Maybe it is currently working, but if I understand everything correctly, every part of the image should use the same OSABI. What do you think?

Originally posted by @stlankes in rust-lang/rust#89062 (comment)

[haraldh]

So, with x86_64-unknown-none instead of x86_64-unknown-none-hermitkernel the resulting binary is still ELFOSABI_STANDALONE

❯ readelf -h target/x86_64-unknown-hermit/debug/rusty_demo
ELF Header:
[…]
  OS/ABI:                            <unknown: ff>

❯ find target/ -name '*.a' -o -name '*.o' -print0 | xargs -0 readelf -h | grep -F 'OS/ABI' | sort -u
  OS/ABI:                            UNIX - System V
  OS/ABI:                            <unknown: ff>

Are you worried, that the linker would not want to link a ELFOSABI_NONE to a ELFOSABI_STANDALONE to produce a binary with ELFOSABI_STANDALONE ??

[stlankes]

Yes, I am not sure if this is correct behavior and would work also with all linkers.

We could change the OSABI of the static library with elfedit. But this isn't part of corgo-binutils. An OS-independent version of elfedit will be great.

[haraldh]

I don't want to introduce problems to your project... I just thought out loud on how to reduce targets with basically the same definitions.

[stlankes]

Yes, I completely understand. I discuss this @mkroening. Maybe we find a good solution.

[stlankes]

@haraldh The "none"-target for aarch64 doesn't support dynamic relocation (see https://github.com/hermitcore/rusty-hermit/runs/4747837810?check_suite_focus=true). Do you think that this feature could be enabled like in x86_64-unknown-none?

[haraldh]

@haraldh The "none"-target for aarch64 doesn't support dynamic relocation (see https://github.com/hermitcore/rusty-hermit/runs/4747837810?check_suite_focus=true). Do you think that this feature could be enabled like in x86_64-unknown-none?

@stlankes sorry, I am not familiar with the state of the aarch64 linkers