rmm: Initial fuzzing setup

[Skryptonyte]

(LFX Task 1)

This PR adds the initial fuzzing setup based on libfuzzer-sys along with two harnesses for RMI commands: FEATURES and VERSION.

Two scripts are provided:

1. ./scripts/fuzz.sh <fuzzer_name> <var_args> - Runs the fuzzer. The script will run the fuzzer natively if the host is aarch64, otherwise it will fall back to QEMU userspace emulator.
2. ./scripts/fuzz-coverage.sh <fuzzer_name> <duration> - Based on ./scripts/code-coverage.sh, the fuzzer is run for a set duration and an html report is generated after at ./code-coverage/index.html.

[Skryptonyte]

Just rebased. I think the CI should work now.

[zpzigi754]

CI log says that cargo check --workspace --exclude islet_sdk --exclude ciborium --exclude islet_mc_harnesses has failed with the included changes. As the error is related to std (error[E0463]: can't find crate for std), I guess that it might be related to the inclusion of an unexpected dependency.

I attach a part of the log below.

warning: `vmsa` (lib) generated 3 warnings
    Checking spin v0.9.8
    Checking tinyvec v1.6.0
    Checking log v0.4.21
   Compiling libfuzzer-sys v0.4.8
    Checking hex v0.4.3
    Checking arbitrary v1.4.1
error[E0463]: can't find crate for `std`
  |
  = note: the `aarch64-unknown-none-softfloat` target may not support the standard library
  = note: `std` is required by `arbitrary` because it does not declare `#![no_std]`
  = help: consider building the standard library from source with `cargo build -Zbuild-std`

    Checking uart v0.0.1 (/home/runner/work/islet/islet/lib/uart)
    Checking bitflags v1.3.2
error[E0463]: can't find crate for `std`
 --> /home/runner/.cargo/registry/src/index.crates.io-6f17d22bba15001f/arbitrary-1.4.1/src/error.rs:1:5
  |
1 | use std::{error, fmt};
  |     ^^^ can't find crate
  |
  = note: the `aarch64-unknown-none-softfloat` target may not support the standard library
  = help: consider building the standard library from source with `cargo build -Zbuild-std`

[zpzigi754]

I've fixed the issue with the pushed commit.

[bokdeuk-jeong]

Rather than putting it here, could you handle it at into/from_current() in rmm/src/rec/context.rs? This looks more cosistent to me.

[Skryptonyte]

I had attempted this, but the compiler would still complain about the following.

error: expected readable system register
  --> /home/parallels/.cargo/registry/src/index.crates.io-6f17d22bba15001f/aarch64-cpu-10.0.0/src/registers/macros.rs:18:42
   |
18 | ...   core::arch::asm!(concat!($asm_instr, " {reg:", $asm_width, "}, ", ...
   |                        ^
   |
note: instantiated into assembly here
  --> <inline asm>:1:10
   |
1  |     mrs x8, CNTPOFF_EL2
   |             ^

error: expected writable system register or pstate
  --> /home/parallels/.cargo/registry/src/index.crates.io-6f17d22bba15001f/aarch64-cpu-10.0.0/src/registers/macros.rs:40:42
   |
40 | ...   core::arch::asm!(concat!($asm_instr, " ", $asm_reg_name, ", {reg:"...
   |                        ^
   |
note: instantiated into assembly here
  --> <inline asm>:1:6
   |
1  |     msr CNTPOFF_EL2, x1

I followed your approach but also added the cfg switch to the entire save_state and restore_state functions in timer.rs to make it compile successfully. Let me know if this is acceptable to you.

[hihi-wang]

Refer other manifest file format, for instance, islet/rmm/Cargo.toml, and fill the fields on [package].

[Skryptonyte]

Done, I fixed up the author name and versioning to be consistent with other crate's manifests.