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|
//! A WebAssembly test case generator.
//!
//! ## Usage
//!
//! First, use [`cargo fuzz`](https://github.com/rust-fuzz/cargo-fuzz) to define
//! a new fuzz target:
//!
//! ```shell
//! $ cargo fuzz add my_wasm_smith_fuzz_target
//! ```
//!
//! Next, add `wasm-smith` to your dependencies:
//!
//! ```shell
//! $ cargo add wasm-smith
//! ```
//!
//! Then, define your fuzz target so that it takes arbitrary
//! `wasm_smith::Module`s as an argument, convert the module into serialized
//! Wasm bytes via the `to_bytes` method, and then feed it into your system:
//!
//! ```no_run
//! // fuzz/fuzz_targets/my_wasm_smith_fuzz_target.rs
//!
//! #![no_main]
//!
//! use libfuzzer_sys::fuzz_target;
//! use wasm_smith::Module;
//!
//! fuzz_target!(|module: Module| {
//! let wasm_bytes = module.to_bytes();
//!
//! // Your code here...
//! });
//! ```
//!
//! Finally, start fuzzing:
//!
//! ```shell
//! $ cargo fuzz run my_wasm_smith_fuzz_target
//! ```
//!
//! > **Note:** For a real world example, also check out [the `validate` fuzz
//! > target](https://github.com/fitzgen/wasm-smith/blob/main/fuzz/fuzz_targets/validate.rs)
//! > defined in this repository. Using the `wasmparser` crate, it checks that
//! > every module generated by `wasm-smith` validates successfully.
//!
//! ## Design
//!
//! The design and implementation strategy of wasm-smith is outlined in
//! [this article](https://fitzgeraldnick.com/2020/08/24/writing-a-test-case-generator.html).
#![deny(missing_docs, missing_debug_implementations)]
// Needed for the `instructions!` macro in `src/code_builder.rs`.
#![recursion_limit = "512"]
mod component;
mod config;
mod core;
pub use crate::core::{InstructionKind, InstructionKinds, Module};
use arbitrary::{Result, Unstructured};
pub use component::Component;
pub use config::{Config, MemoryOffsetChoices};
use std::{collections::HashSet, fmt::Write, str};
use wasm_encoder::MemoryType;
#[cfg(feature = "_internal_cli")]
pub use config::InternalOptionalConfig;
pub(crate) fn page_size(mem: &MemoryType) -> u32 {
const DEFAULT_WASM_PAGE_SIZE: u32 = 65_536;
mem.page_size_log2.unwrap_or(DEFAULT_WASM_PAGE_SIZE)
}
/// Do something an arbitrary number of times.
///
/// The callback can return `false` to exit the loop early.
pub(crate) fn arbitrary_loop<'a>(
u: &mut Unstructured<'a>,
min: usize,
max: usize,
mut f: impl FnMut(&mut Unstructured<'a>) -> Result<bool>,
) -> Result<()> {
assert!(max >= min);
for _ in 0..min {
if !f(u)? {
return Err(arbitrary::Error::IncorrectFormat);
}
}
for _ in 0..(max - min) {
let keep_going = u.arbitrary().unwrap_or(false);
if !keep_going {
break;
}
if !f(u)? {
break;
}
}
Ok(())
}
// Mirror what happens in `Arbitrary for String`, but do so with a clamped size.
pub(crate) fn limited_str<'a>(max_size: usize, u: &mut Unstructured<'a>) -> Result<&'a str> {
let size = u.arbitrary_len::<u8>()?;
let size = std::cmp::min(size, max_size);
match str::from_utf8(u.peek_bytes(size).unwrap()) {
Ok(s) => {
u.bytes(size).unwrap();
Ok(s)
}
Err(e) => {
let i = e.valid_up_to();
let valid = u.bytes(i).unwrap();
let s = str::from_utf8(valid).unwrap();
Ok(s)
}
}
}
pub(crate) fn limited_string(max_size: usize, u: &mut Unstructured) -> Result<String> {
Ok(limited_str(max_size, u)?.into())
}
pub(crate) fn unique_string(
max_size: usize,
names: &mut HashSet<String>,
u: &mut Unstructured,
) -> Result<String> {
let mut name = limited_string(max_size, u)?;
while names.contains(&name) {
write!(&mut name, "{}", names.len()).unwrap();
}
names.insert(name.clone());
Ok(name)
}
pub(crate) fn unique_kebab_string(
max_size: usize,
names: &mut HashSet<String>,
u: &mut Unstructured,
) -> Result<String> {
let size = std::cmp::min(u.arbitrary_len::<u8>()?, max_size);
let mut name = String::with_capacity(size);
let mut require_alpha = true;
for _ in 0..size {
name.push(match u.int_in_range::<u8>(0..=36)? {
x if (0..26).contains(&x) => {
require_alpha = false;
(b'a' + x) as char
}
x if (26..36).contains(&x) => {
if require_alpha {
require_alpha = false;
(b'a' + (x - 26)) as char
} else {
(b'0' + (x - 26)) as char
}
}
x if x == 36 => {
if require_alpha {
require_alpha = false;
'a'
} else {
require_alpha = true;
'-'
}
}
_ => unreachable!(),
});
}
if name.is_empty() || name.ends_with('-') {
name.push('a');
}
while names.contains(&name) {
write!(&mut name, "{}", names.len()).unwrap();
}
names.insert(name.clone());
Ok(name)
}
pub(crate) fn unique_url(
max_size: usize,
names: &mut HashSet<String>,
u: &mut Unstructured,
) -> Result<String> {
let path = unique_kebab_string(max_size, names, u)?;
Ok(format!("https://example.com/{path}"))
}
|
