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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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53
crates/fuzzing/src/oracles/diff_wasmi.rs
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@@ -1,45 +1,30 @@
//! Evaluate an exported Wasm function using the wasmi interpreter.
use crate::generators::{DiffValue, DiffValueType, ModuleConfig};
use crate::generators::{Config, DiffValue, DiffValueType};
use crate::oracles::engine::{DiffEngine, DiffInstance};
use anyhow::{bail, Context, Error, Result};
use anyhow::{Context, Error, Result};
use wasmtime::{Trap, TrapCode};
/// A wrapper for `wasmi` as a [`DiffEngine`].
pub struct WasmiEngine;
impl WasmiEngine {
/// Build a new [`WasmiEngine`] but only if the configuration does not rely
/// on features that `wasmi` does not support.
pub fn new(config: &ModuleConfig) -> Result<Self> {
if config.config.reference_types_enabled {
bail!("wasmi does not support reference types")
}
if config.config.simd_enabled {
bail!("wasmi does not support SIMD")
}
if config.config.multi_value_enabled {
bail!("wasmi does not support multi-value")
}
if config.config.saturating_float_to_int_enabled {
bail!("wasmi does not support saturating float-to-int conversions")
}
if config.config.sign_extension_enabled {
bail!("wasmi does not support sign-extension")
}
if config.config.memory64_enabled {
bail!("wasmi does not support memory64");
}
if config.config.bulk_memory_enabled {
bail!("wasmi does not support bulk memory");
}
if config.config.threads_enabled {
bail!("wasmi does not support threads");
}
if config.config.max_memories > 1 {
bail!("wasmi does not support multi-memory");
}
Ok(Self)
pub(crate) fn new(config: &mut Config) -> Self {
let config = &mut config.module_config.config;
config.reference_types_enabled = false;
config.simd_enabled = false;
config.multi_value_enabled = false;
config.saturating_float_to_int_enabled = false;
config.sign_extension_enabled = false;
config.memory64_enabled = false;
config.bulk_memory_enabled = false;
config.threads_enabled = false;
config.max_memories = config.max_memories.min(1);
config.min_memories = config.min_memories.min(1);
config.max_tables = config.max_tables.min(1);
config.min_tables = config.min_tables.min(1);
Self
}
}
@@ -223,5 +208,5 @@ impl Into<DiffValue> for wasmi::RuntimeValue {
#[test]
fn smoke() {
crate::oracles::engine::smoke_test_engine(|config| WasmiEngine::new(&config.module_config))
crate::oracles::engine::smoke_test_engine(|_, config| Ok(WasmiEngine::new(config)))
}