wasmtime_fuzzing/oracles/
diff_spec.rs

1//! Evaluate an exported Wasm function using the WebAssembly specification
2//! reference interpreter.
3
4use crate::generators::{Config, DiffValue, DiffValueType};
5use crate::oracles::engine::{DiffEngine, DiffInstance};
6use anyhow::{anyhow, Error, Result};
7use wasm_spec_interpreter::SpecValue;
8use wasmtime::Trap;
9
10/// A wrapper for `wasm-spec-interpreter` as a [`DiffEngine`].
11pub struct SpecInterpreter;
12
13impl SpecInterpreter {
14    pub(crate) fn new(config: &mut Config) -> Self {
15        let config = &mut config.module_config.config;
16
17        config.min_memories = config.min_memories.min(1);
18        config.max_memories = config.max_memories.min(1);
19        config.min_tables = config.min_tables.min(1);
20        config.max_tables = config.max_tables.min(1);
21
22        config.memory64_enabled = false;
23        config.threads_enabled = false;
24        config.bulk_memory_enabled = false;
25        config.reference_types_enabled = false;
26        config.tail_call_enabled = false;
27        config.relaxed_simd_enabled = false;
28        config.custom_page_sizes_enabled = false;
29        config.wide_arithmetic_enabled = false;
30        config.extended_const_enabled = false;
31
32        Self
33    }
34}
35
36impl DiffEngine for SpecInterpreter {
37    fn name(&self) -> &'static str {
38        "spec"
39    }
40
41    fn instantiate(&mut self, wasm: &[u8]) -> Result<Box<dyn DiffInstance>> {
42        let instance = wasm_spec_interpreter::instantiate(wasm)
43            .map_err(|e| anyhow!("failed to instantiate in spec interpreter: {}", e))?;
44        Ok(Box::new(SpecInstance { instance }))
45    }
46
47    fn assert_error_match(&self, err: &Error, trap: &Trap) {
48        // TODO: implement this for the spec interpreter
49        let _ = (trap, err);
50    }
51
52    fn is_non_deterministic_error(&self, err: &Error) -> bool {
53        err.to_string().contains("(Isabelle) call stack exhausted")
54    }
55}
56
57struct SpecInstance {
58    instance: wasm_spec_interpreter::SpecInstance,
59}
60
61impl DiffInstance for SpecInstance {
62    fn name(&self) -> &'static str {
63        "spec"
64    }
65
66    fn evaluate(
67        &mut self,
68        function_name: &str,
69        arguments: &[DiffValue],
70        _results: &[DiffValueType],
71    ) -> Result<Option<Vec<DiffValue>>> {
72        let arguments = arguments.iter().map(SpecValue::from).collect();
73        match wasm_spec_interpreter::interpret(&self.instance, function_name, Some(arguments)) {
74            Ok(results) => Ok(Some(results.into_iter().map(SpecValue::into).collect())),
75            Err(err) => Err(anyhow!(err)),
76        }
77    }
78
79    fn get_global(&mut self, name: &str, _ty: DiffValueType) -> Option<DiffValue> {
80        use wasm_spec_interpreter::{export, SpecExport::Global};
81        if let Ok(Global(g)) = export(&self.instance, name) {
82            Some(g.into())
83        } else {
84            panic!("expected an exported global value at name `{name}`")
85        }
86    }
87
88    fn get_memory(&mut self, name: &str, _shared: bool) -> Option<Vec<u8>> {
89        use wasm_spec_interpreter::{export, SpecExport::Memory};
90        if let Ok(Memory(m)) = export(&self.instance, name) {
91            Some(m)
92        } else {
93            panic!("expected an exported memory at name `{name}`")
94        }
95    }
96}
97
98impl From<&DiffValue> for SpecValue {
99    fn from(v: &DiffValue) -> Self {
100        match *v {
101            DiffValue::I32(n) => SpecValue::I32(n),
102            DiffValue::I64(n) => SpecValue::I64(n),
103            DiffValue::F32(n) => SpecValue::F32(n as i32),
104            DiffValue::F64(n) => SpecValue::F64(n as i64),
105            DiffValue::V128(n) => SpecValue::V128(n.to_le_bytes().to_vec()),
106            DiffValue::FuncRef { .. } | DiffValue::ExternRef { .. } | DiffValue::AnyRef { .. } => {
107                unimplemented!()
108            }
109        }
110    }
111}
112
113impl Into<DiffValue> for SpecValue {
114    fn into(self) -> DiffValue {
115        match self {
116            SpecValue::I32(n) => DiffValue::I32(n),
117            SpecValue::I64(n) => DiffValue::I64(n),
118            SpecValue::F32(n) => DiffValue::F32(n as u32),
119            SpecValue::F64(n) => DiffValue::F64(n as u64),
120            SpecValue::V128(n) => {
121                assert_eq!(n.len(), 16);
122                DiffValue::V128(u128::from_le_bytes(n.as_slice().try_into().unwrap()))
123            }
124        }
125    }
126}
127
128/// Set up the OCaml runtime for triggering its signal handler configuration.
129///
130/// Because both the OCaml runtime and Wasmtime set up signal handlers, we must
131/// carefully decide when to instantiate them; this function allows us to
132/// control when. Wasmtime uses these signal handlers for catching various
133/// WebAssembly failures. On certain OSes (e.g. Linux `x86_64`), the signal
134/// handlers interfere, observable as an uncaught `SIGSEGV`--not even caught by
135/// libFuzzer.
136///
137/// This failure can be mitigated by always running Wasmtime second in
138/// differential fuzzing. In some cases, however, this is not possible because
139/// which engine will execute first is unknown. This function can be explicitly
140/// executed first, e.g., during global initialization, to avoid this issue.
141pub fn setup_ocaml_runtime() {
142    wasm_spec_interpreter::setup_ocaml_runtime();
143}
144
145#[cfg(test)]
146mod tests {
147    use super::*;
148
149    #[test]
150    fn smoke() {
151        if !wasm_spec_interpreter::support_compiled_in() {
152            return;
153        }
154        crate::oracles::engine::smoke_test_engine(|_, config| Ok(SpecInterpreter::new(config)))
155    }
156}
wasmtime_fuzzing/oracles/diff_spec.rs

wasmtime_fuzzing/oracles/
diff_spec.rs
