IBM z/Architecture (s390x) support

[raulcabello]

I got an error with the ring crate when compiling kwctl for s390x. It is the same error described here briansmith/ring#986

I get the same error compiling ring on a s390x VM and cross compiling with cargo build --target s390x-unknown-linux-gnu.
musl does not work on s390x, cargo build --target s390x-unknown-linux-musl fails because std is not available https://doc.rust-lang.org/nightly/rustc/platform-support.html#tier-3

This PR briansmith/ring#1297 adds support for s390x, but it looks like it's not in active development and needs more work. I successfully compiled ring from this PR on s390x, but rustls does not compile because there were some changes done in ring 0.17. I got the following error:

   Compiling rustls v0.19.1

error[E0061]: this function takes 3 arguments but 4 arguments were supplied
   --> /root/.cargo/registry/src/github.com-eae4ba8cbf2ce1c7/rustls-0.19.1/src/suites.rs:109:22
    |
109 |           let secret = ring::agreement::agree_ephemeral(self.privkey, &peer_key, (), |v| {
    |  ______________________^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^_------------__---------__--__-
    | |                      |
    | |                      expected 3 arguments
110 | |             let mut r = Vec::new();
111 | |             r.extend_from_slice(v);
112 | |             Ok(r)
113 | |         });
    | |_________- supplied 4 arguments


249 | pub fn agree_ephemeral<B: AsRef<[u8]>, R>(
    |        ^^^^^^^^^^^^^^^

error[E0061]: this function takes 3 arguments but 2 arguments were supplied
   --> /root/.cargo/registry/src/github.com-eae4ba8cbf2ce1c7/rustls-0.19.1/src/sign.rs:297:9
    |
297 |         EcdsaKeyPair::from_pkcs8(sigalg, &der.0)
    |         ^^^^^^^^^^^^^^^^^^^^^^^^ ------  ------ supplied 2 arguments
    |         |
    |         expected 3 arguments

I can compile kwctl if I remove rustls, then the following error is deployed when executing kwctl run

thread 'main' panicked at 'not implemented: Unimplemented relocation S390xPCRel32Dbl', /root/.cargo/registry/src/github.com-eae4ba8cbf2ce1c7/wasmtime-cranelift-0.30.0/src/obj.rs:454:26

Summary of what we would need:

• Add s390x support for ring (there is already a PR, but it looks like it's not in active development and needs more work)
• Modify rustls to use the ring version with s390x support
• Fix issue with wasmtime on s390x

[flavio]

Maybe it would be possible to build with ring and openssl, not with rusttls... You could do a quick test by replacing rusttls with openssl-sys inside of all our crates. Do something hackish, like changing all the Cargo.toml

[raulcabello]

@flavio I removed rustls from all crates and I could compile kwctl on s390x. I also had to remove mdcat because it was using rustls.
I got the following error when executing kwctl run

thread 'main' panicked at 'not implemented: Unimplemented relocation S390xPCRel32Dbl', /root/.cargo/registry/src/github.com-eae4ba8cbf2ce1c7/wasmtime-cranelift-0.30.0/src/obj.rs:454:26

I tried to use wasmtime 0.33.0 to see if this issue was fixed. For that I used wasmtime-provider v1.0.0-alpha.0, then I got this error:

error[E0277]: the trait bound `Result<WasmtimeEngineProvider, wasmtime_provider::errors::Error>: WebAssemblyEngineProvider` is not satisfied
   --> /root/policy-evaluator/src/policy_evaluator.rs:131:47
    let wapc_host = WapcHost::new(Box::new(engine), wapc_callback)?;
     ------------- ^^^^^^^^^^^^^^^^ the trait `WebAssemblyEngineProvider` is not implemented for   `Result<WasmtimeEngineProvider, wasmtime_provider::errors::Error>`
    required by a bound introduced by this call

Anyway it looks like relocation S390xPCRel32Dbl is still not implemented https://github.com/bytecodealliance/wasmtime/blob/main/crates/cranelift/src/obj.rs#L439

[flavio]

Ouch, thanks a lot for the investigation. This is useful information