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Throw out fewer fuzz inputs with differential fuzzer (#4859)

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* Throw out fewer fuzz inputs with differential fuzzer

Prior to this commit the differential fuzzer would generate a module and
then select an engine to execute the module against Wasmtime. This
meant, however, that the candidate list of engines were filtered against
the configuration used to generate the module to ensure that the
selected engine could run the generated module.

This commit inverts this logic and instead selects an engine first,
allowing the engine to then tweak the module configuration to ensure
that the generated module is compatible with the engine selected. This
means that fewer fuzz inputs are discarded because every fuzz input will
result in an engine being executed.

Internally the engine constructors have all been updated to update the
configuration to work instead of filtering the configuration. Some other
fixes were applied for the spec interpreter as well to work around #4852

* Fix tests
This commit is contained in:
Alex Crichton
2022-09-06 12:41:23 -05:00
committed by GitHub
parent 9856664f1f
commit 543a487939
8 changed files with 142 additions and 182 deletions
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15
crates/fuzzing/src/oracles/diff_wasmtime.rs
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@@ -1,15 +1,16 @@
//! Evaluate an exported Wasm function using Wasmtime.
use crate::generators::{self, DiffValue, DiffValueType};
use crate::generators::{self, DiffValue, DiffValueType, WasmtimeConfig};
use crate::oracles::dummy;
use crate::oracles::engine::DiffInstance;
use crate::oracles::{compile_module, engine::DiffEngine, StoreLimits};
use anyhow::{Context, Error, Result};
use arbitrary::Unstructured;
use wasmtime::{Extern, FuncType, Instance, Module, Store, Trap, TrapCode, Val};
/// A wrapper for using Wasmtime as a [`DiffEngine`].
pub struct WasmtimeEngine {
pub(crate) config: generators::Config,
config: generators::Config,
}
impl WasmtimeEngine {
@@ -17,7 +18,13 @@ impl WasmtimeEngine {
/// later. Ideally the store and engine could be built here but
/// `compile_module` takes a [`generators::Config`]; TODO re-factor this if
/// that ever changes.
pub fn new(config: generators::Config) -> Result<Self> {
pub fn new(u: &mut Unstructured<'_>, config: &generators::Config) -> arbitrary::Result<Self> {
let mut new_config = u.arbitrary::<WasmtimeConfig>()?;
new_config.make_compatible_with(&config.wasmtime);
let config = generators::Config {
wasmtime: new_config,
module_config: config.module_config.clone(),
};
Ok(Self { config })
}
}
@@ -220,5 +227,5 @@ impl Into<DiffValue> for Val {
#[test]
fn smoke() {
crate::oracles::engine::smoke_test_engine(|config| WasmtimeEngine::new(config))
crate::oracles::engine::smoke_test_engine(|u, config| WasmtimeEngine::new(u, config))
}