repro issue #808

[qjerome]

Implemented test aiming to reproduce issue #808
There is a little quirk though !
It actually triggers a bug, but not the expected one ! So I hope, once the unexpected bug gets fixed it will trigger the expected one.

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[mergify]

@qjerome, this pull request is now in conflict and requires a rebase.

[alessandrod]

It actually triggers a bug, but not the expected one ! So I hope, once the unexpected bug gets fixed it will trigger the expected one.

RUSTFLAGS="-C debuginfo=2" 😂

And then you get:

running 1 test
test tests::load::log_str_random ... FAILED

failures:

---- tests::load::log_str_random stdout ----
thread 'tests::load::log_str_random' panicked at 'called `Result::unwrap()` on an `Err` value: LoadError { io_error: Os { code: 22, kind: InvalidInput, message: "Invalid argument" }, verifier_log: Validating write() func#1...
Global function write() doesn't return scalar. Only those are supported.
verification time 18 usec
stack depth 0+0
processed 0 insns (limit 1000000) max_states_per_insn 0 total_states 0 peak_states 0 mark_read 0
 }', test/integration-test/src/tests/load.rs:624:17

[alessandrod]

The issue is functions from external crates get compiled as global functions instead of static. Global functions can't return non-scalar types.

In bpf-linker, we should probably detect when a global function returns a non-scalar type, and override it to be static.

[alessandrod]

Fixed in aya-rs/bpf-linker#173