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Fuzzing: Add test case logging and regression test template

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When the test case that causes the failure can successfully be disassembled to
WAT, we get logs like this:

```
[2019-11-26T18:48:46Z INFO  wasmtime_fuzzing] Wrote WAT disassembly to: /home/fitzgen/wasmtime/crates/fuzzing/target/scratch/8437-0.wat
[2019-11-26T18:48:46Z INFO  wasmtime_fuzzing] If this fuzz test fails, copy `/home/fitzgen/wasmtime/crates/fuzzing/target/scratch/8437-0.wat` to `wasmtime/crates/fuzzing/tests/regressions/my-regression.wat` and add the following test to `wasmtime/crates/fuzzing/tests/regressions.rs`:

    ```
    #[test]
    fn my_fuzzing_regression_test() {
        let data = wat::parse_str(
            include_str!("./regressions/my-regression.wat")
        ).unwrap();
        oracles::instantiate(data, CompilationStrategy::Auto)
    }
    ```
```

If the test case cannot be disassembled to WAT, then we get logs like this:

```
[2019-11-26T18:48:46Z INFO  wasmtime_fuzzing] Wrote Wasm test case to: /home/fitzgen/wasmtime/crates/fuzzing/target/scratch/8437-0.wasm
[2019-11-26T18:48:46Z INFO  wasmtime_fuzzing] Failed to disassemble Wasm into WAT:
    Bad magic number (at offset 0)

    Stack backtrace:
        Run with RUST_LIB_BACKTRACE=1 env variable to display a backtrace

[2019-11-26T18:48:46Z INFO  wasmtime_fuzzing] If this fuzz test fails, copy `/home/fitzgen/wasmtime/crates/fuzzing/target/scratch/8437-0.wasm` to `wasmtime/crates/fuzzing/tests/regressions/my-regression.wasm` and add the following test to `wasmtime/crates/fuzzing/tests/regressions.rs`:

    ```
    #[test]
    fn my_fuzzing_regression_test() {
        let data = include_bytes!("./regressions/my-regression.wasm");
        oracles::instantiate(data, CompilationStrategy::Auto)
    }
    ```
```
This commit is contained in:
Nick Fitzgerald
2019-11-25 16:20:59 -08:00
parent 8a58cad329
commit bab59a2cd2
9 changed files with 200 additions and 9 deletions
Download Patch File Download Diff File Expand all files Collapse all files

1
crates/fuzzing/src/generators.rs
View File

@@ -11,6 +11,7 @@
use arbitrary::{Arbitrary, Unstructured};
/// A Wasm test case generator that is powered by Binaryen's `wasm-opt -ttf`.
#[derive(Debug)]
pub struct WasmOptTtf {
/// The raw, encoded Wasm bytes.
pub wasm: Vec<u8>,

163
crates/fuzzing/src/lib.rs
View File

@@ -1,2 +1,165 @@
//! Fuzzing infrastructure for Wasmtime.
#![deny(missing_docs, missing_debug_implementations)]
pub mod generators;
pub mod oracles;
use anyhow::Context;
use std::fs;
use std::path::{Path, PathBuf};
use std::process;
use std::sync::{atomic, Once};
/// Run a fuzz test on Wasm test case with automatic logging.
///
/// This is intended for defining the body of a `libfuzzer_sys::fuzz_target!`
/// invocation.
///
/// Automatically prints out how to create a regression test that runs the exact
/// same set of oracles.
///
/// It also binds the expression getting the wasm bytes to the variable, for
/// example below the `wasm` variable is assigned the value
/// `&my_test_case.as_wasm_bytes()`. This variable can be used within the body.
///
/// ```ignore
/// use wasmtime_fuzzing::{oracles, with_log_wasm_test_case};
///
/// with_log_wasm_test_case!(&my_test_case.as_wasm_bytes(), |wasm| {
/// oracles::compile(wasm);
/// oracles::instantiate(wasm);
/// });
/// ```
#[macro_export]
macro_rules! with_log_wasm_test_case {
( $wasm:expr , |$wasm_var:ident| $oracle:expr ) => {{
let $wasm_var = $wasm;
wasmtime_fuzzing::log_wasm_test_case(
&$wasm_var,
stringify!($wasm_var),
stringify!($oracle),
);
$oracle;
}};
}
/// Given that we are going to do a fuzz test of the given Wasm buffer, log the
/// Wasm and its WAT disassembly, and preserve them to the filesystem so that if
/// we panic or crash, we can easily inspect the test case.
///
/// This is intended to be used via the `with_log_wasm_test_case` macro.
pub fn log_wasm_test_case(wasm: &[u8], wasm_var: &'static str, oracle_expr: &'static str) {
init_logging();
let wasm_path = wasm_test_case_path();
fs::write(&wasm_path, wasm)
.with_context(|| format!("Failed to write wasm to {}", wasm_path.display()))
.unwrap();
log::info!("Wrote Wasm test case to: {}", wasm_path.display());
match wasmprinter::print_bytes(wasm) {
Ok(wat) => {
log::info!("WAT disassembly:\n{}", wat);
let wat_path = wat_disassembly_path();
fs::write(&wat_path, &wat)
.with_context(|| {
format!("Failed to write WAT disassembly to {}", wat_path.display())
})
.unwrap();
log::info!("Wrote WAT disassembly to: {}", wat_path.display());
log::info!(
"If this fuzz test fails, copy `{wat_path}` to `wasmtime/crates/fuzzing/tests/regressions/my-regression.wat` and add the following test to `wasmtime/crates/fuzzing/tests/regressions.rs`:
```
#[test]
fn my_fuzzing_regression_test() {{
let {wasm_var} = wat::parse_str(
include_str!(\"./regressions/my-regression.wat\")
).unwrap();
{oracle_expr}
}}
```",
wat_path = wat_path.display(),
wasm_var = wasm_var,
oracle_expr = oracle_expr
);
}
Err(e) => {
log::info!("Failed to disassemble Wasm into WAT:\n{:?}", e);
log::info!(
"If this fuzz test fails, copy `{wasm_path}` to `wasmtime/crates/fuzzing/tests/regressions/my-regression.wasm` and add the following test to `wasmtime/crates/fuzzing/tests/regressions.rs`:
```
#[test]
fn my_fuzzing_regression_test() {{
let {wasm_var} = include_bytes!(\"./regressions/my-regression.wasm\");
{oracle_expr}
}}
```",
wasm_path = wasm_path.display(),
wasm_var = wasm_var,
oracle_expr = oracle_expr
);
}
}
}
fn scratch_dir() -> PathBuf {
let dir = Path::new(env!("CARGO_MANIFEST_DIR"))
.join("target")
.join("scratch");
static CREATE: Once = Once::new();
CREATE.call_once(|| {
fs::create_dir_all(&dir)
.with_context(|| format!("Failed to create {}", dir.display()))
.unwrap();
});
dir
}
fn wasm_test_case_path() -> PathBuf {
static WASM_TEST_CASE_COUNTER: atomic::AtomicUsize = atomic::AtomicUsize::new(0);
thread_local! {
static WASM_TEST_CASE_PATH: PathBuf = {
let dir = scratch_dir();
dir.join(format!("{}-{}.wasm",
process::id(),
WASM_TEST_CASE_COUNTER.fetch_add(1, atomic::Ordering::SeqCst)
))
};
}
WASM_TEST_CASE_PATH.with(|p| p.clone())
}
fn wat_disassembly_path() -> PathBuf {
static WAT_DISASSEMBLY_COUNTER: atomic::AtomicUsize = atomic::AtomicUsize::new(0);
thread_local! {
static WAT_DISASSEMBLY_PATH: PathBuf = {
let dir = scratch_dir();
dir.join(format!(
"{}-{}.wat",
process::id(),
WAT_DISASSEMBLY_COUNTER.fetch_add(1, atomic::Ordering::SeqCst)
))
};
}
WAT_DISASSEMBLY_PATH.with(|p| p.clone())
}
#[cfg(feature = "env_logger")]
fn init_logging() {
static INIT_LOGGING: Once = Once::new();
INIT_LOGGING.call_once(|| env_logger::init());
}
#[cfg(not(feature = "env_logger"))]
fn init_logging() {}