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//! Wizer: the WebAssembly pre-initializer!
//!
//! See the [`Wizer`] struct for details.
#![deny(missing_docs)]
#[cfg(fuzzing)]
pub mod dummy;
#[cfg(not(fuzzing))]
mod dummy;
mod info;
mod instrument;
mod parse;
mod rewrite;
mod snapshot;
mod stack_ext;
mod translate;
use wasi_common::sync::WasiCtxBuilder;
/// Re-export wasmtime so users can align with our version. This is
/// especially useful when providing a custom Linker.
pub use wasmtime;
use anyhow::Context;
use dummy::dummy_imports;
use std::collections::{HashMap, HashSet};
use std::fmt::Display;
use std::path::PathBuf;
use std::rc::Rc;
#[cfg(feature = "structopt")]
use structopt::StructOpt;
use wasi_common::WasiCtx;
use wasmtime::{Engine, Extern};
const DEFAULT_INHERIT_STDIO: bool = true;
const DEFAULT_INHERIT_ENV: bool = false;
const DEFAULT_KEEP_INIT_FUNC: bool = false;
const DEFAULT_WASM_MULTI_VALUE: bool = true;
const DEFAULT_WASM_MULTI_MEMORY: bool = true;
const DEFAULT_WASM_BULK_MEMORY: bool = false;
const DEFAULT_WASM_SIMD: bool = true;
/// We only ever use `Store<T>` with a fixed `T` that is our optional WASI
/// context.
pub(crate) type Store = wasmtime::Store<Option<WasiCtx>>;
/// The type of linker that Wizer uses when evaluating the initialization function.
pub type Linker = wasmtime::Linker<Option<WasiCtx>>;
#[cfg(feature = "structopt")]
fn parse_map_dirs(s: &str) -> anyhow::Result<(PathBuf, PathBuf)> {
let parts: Vec<&str> = s.split("::").collect();
if parts.len() != 2 {
anyhow::bail!("must contain exactly one double colon ('::')");
}
Ok((parts[0].into(), parts[1].into()))
}
/// Wizer: the WebAssembly pre-initializer!
///
/// Don't wait for your Wasm module to initialize itself, pre-initialize it!
/// Wizer instantiates your WebAssembly module, executes its initialization
/// function, and then serializes the instance's initialized state out into a
/// new WebAssembly module. Now you can use this new, pre-initialized
/// WebAssembly module to hit the ground running, without making your users wait
/// for that first-time set up code to complete.
///
/// ## Caveats
///
/// * The initialization function may not call any imported functions. Doing so
/// will trigger a trap and `wizer` will exit.
///
/// * The Wasm module may not import globals, tables, or memories.
///
/// * Reference types are not supported yet. This is tricky because it would
/// allow the Wasm module to mutate tables, and we would need to be able to
/// snapshot the new table state, but funcrefs and externrefs don't have
/// identity and aren't comparable in the Wasm spec, which makes snapshotting
/// difficult.
#[cfg_attr(feature = "structopt", derive(StructOpt))]
#[derive(Clone)]
pub struct Wizer {
/// The Wasm export name of the function that should be executed to
/// initialize the Wasm module.
#[cfg_attr(
feature = "structopt",
structopt(short = "f", long = "init-func", default_value = "wizer.initialize")
)]
init_func: String,
/// Any function renamings to perform.
///
/// A renaming specification `dst=src` renames a function export `src` to
/// `dst`, overwriting any previous `dst` export.
///
/// Multiple renamings can be specified. It is an error to specify more than
/// one source to rename to a destination name, or to specify more than one
/// renaming destination for one source.
///
/// This option can be used, for example, to replace a `_start` entry point
/// in an initialized module with an alternate entry point.
///
/// When module linking is enabled, these renames are only applied to the
/// outermost module.
#[cfg_attr(
feature = "structopt",
structopt(
short = "r",
long = "rename-func",
alias = "func-rename",
value_name = "dst=src"
)
)]
func_renames: Vec<String>,
/// Allow WASI imports to be called during initialization.
///
/// This can introduce diverging semantics because the initialization can
/// observe nondeterminism that might have gone a different way at runtime
/// than it did at initialization time.
///
/// If your Wasm module uses WASI's `get_random` to add randomness to
/// something as a security mitigation (e.g. something akin to ASLR or the
/// way Rust's hash maps incorporate a random nonce) then note that, if the
/// randomization is added during initialization time and you don't ever
/// re-randomize at runtime, then that randomization will become per-module
/// rather than per-instance.
#[cfg_attr(feature = "structopt", structopt(long = "allow-wasi"))]
allow_wasi: bool,
/// Provide an additional preloaded module that is available to the
/// main module.
///
/// This allows running a module that depends on imports from
/// another module. Note that the additional module's state is *not*
/// snapshotted, nor is its code included in the Wasm snapshot;
/// rather, it is assumed that the resulting snapshot Wasm will also
/// be executed with the same imports available.
///
/// The main purpose of this option is to allow "stubs" for certain
/// intrinsics to be included, when these will be provided with
/// different implementations when running or further processing the
/// snapshot.
///
/// The format of this option is `name=file.{wasm,wat}`; e.g.,
/// `intrinsics=stubs.wat`. Multiple instances of the option may
/// appear.
#[cfg_attr(feature = "structopt", structopt(long = "preload"))]
preload: Vec<String>,
/// Like `preload` above, but with the module contents provided,
/// rather than a filename. This is more useful for programmatic
/// use-cases where the embedding tool may also embed a Wasm module.
#[cfg_attr(feature = "structopt", structopt(skip))]
preload_bytes: Vec<(String, Vec<u8>)>,
#[cfg_attr(feature = "structopt", structopt(skip))]
make_linker: Option<Rc<dyn Fn(&wasmtime::Engine) -> anyhow::Result<Linker>>>,
/// When using WASI during initialization, should `stdin`, `stderr`, and
/// `stdout` be inherited?
///
/// This is true by default.
#[cfg_attr(
feature = "structopt",
structopt(long = "inherit-stdio", value_name = "true|false")
)]
inherit_stdio: Option<bool>,
/// When using WASI during initialization, should environment variables be
/// inherited?
///
/// This is false by default.
#[cfg_attr(
feature = "structopt",
structopt(long = "inherit-env", value_name = "true|false")
)]
inherit_env: Option<bool>,
/// After initialization, should the Wasm module still export the
/// initialization function?
///
/// This is `false` by default, meaning that the initialization function is
/// no longer exported from the Wasm module.
#[cfg_attr(
feature = "structopt",
structopt(long = "keep-init-func", value_name = "true|false")
)]
keep_init_func: Option<bool>,
/// When using WASI during initialization, which file system directories
/// should be made available?
///
/// None are available by default.
#[cfg_attr(
feature = "structopt",
structopt(long = "dir", parse(from_os_str), value_name = "directory")
)]
dirs: Vec<PathBuf>,
/// When using WASI during initialization, which guest directories should be
/// mapped to a host directory?
///
/// The `--mapdir` option differs from `--dir` in that it allows giving a
/// custom guest name to the directory that is different from its name in
/// the host.
///
/// None are mapped by default.
#[cfg_attr(
feature = "structopt",
structopt(long = "mapdir", value_name = "GUEST_DIR::HOST_DIR", parse(try_from_str = parse_map_dirs))
)]
map_dirs: Vec<(PathBuf, PathBuf)>,
/// Enable or disable Wasm multi-memory proposal.
///
/// Enabled by default.
#[cfg_attr(feature = "structopt", structopt(long, value_name = "true|false"))]
wasm_multi_memory: Option<bool>,
/// Enable or disable the Wasm multi-value proposal.
///
/// Enabled by default.
#[cfg_attr(feature = "structopt", structopt(long, value_name = "true|false"))]
wasm_multi_value: Option<bool>,
/// Enable or disable Wasm bulk memory operations.
///
/// Note that only `memory.copy`, `memory.fill`, and `memory.init` operations
/// are currently supported. Modules which use other instructions, such as
/// `table.copy` will be rejected.
///
/// Disabled by default.
#[cfg_attr(feature = "structopt", structopt(long, value_name = "true|false"))]
wasm_bulk_memory: Option<bool>,
/// Enable or disable the Wasm SIMD128 proposal.
///
/// Enabled by default.
#[cfg_attr(feature = "structopt", structopt(long, value_name = "true|false"))]
wasm_simd: Option<bool>,
}
impl std::fmt::Debug for Wizer {
fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
let Wizer {
init_func,
func_renames,
allow_wasi,
preload,
preload_bytes,
make_linker: _,
inherit_stdio,
inherit_env,
keep_init_func,
dirs,
map_dirs,
wasm_multi_memory,
wasm_multi_value,
wasm_bulk_memory,
wasm_simd,
} = self;
f.debug_struct("Wizer")
.field("init_func", &init_func)
.field("func_renames", &func_renames)
.field("allow_wasi", &allow_wasi)
.field("preload", &preload)
.field("preload_bytes", &preload_bytes)
.field("make_linker", &"..")
.field("inherit_stdio", &inherit_stdio)
.field("inherit_env", &inherit_env)
.field("keep_init_func", &keep_init_func)
.field("dirs", &dirs)
.field("map_dirs", &map_dirs)
.field("wasm_multi_memory", &wasm_multi_memory)
.field("wasm_multi_value", &wasm_multi_value)
.field("wasm_bulk_memory", &wasm_bulk_memory)
.field("wasm_simd", &wasm_simd)
.finish()
}
}
struct FuncRenames {
/// For a given export name that we encounter in the original module, a map
/// to a new name, if any, to emit in the output module.
rename_src_to_dst: HashMap<String, String>,
/// A set of export names that we ignore in the original module (because
/// they are overwritten by renamings).
rename_dsts: HashSet<String>,
}
impl FuncRenames {
fn parse(renames: &Vec<String>) -> anyhow::Result<FuncRenames> {
let mut ret = FuncRenames {
rename_src_to_dst: HashMap::new(),
rename_dsts: HashSet::new(),
};
if renames.is_empty() {
return Ok(ret);
}
for rename_spec in renames {
let equal = rename_spec
.trim()
.find('=')
.ok_or_else(|| anyhow::anyhow!("Invalid function rename part: {}", rename_spec))?;
// TODO: use .split_off() when the API is stabilized.
let dst = rename_spec[..equal].to_owned();
let src = rename_spec[equal + 1..].to_owned();
if ret.rename_dsts.contains(&dst) {
anyhow::bail!("Duplicated function rename dst {}", dst);
}
if ret.rename_src_to_dst.contains_key(&src) {
anyhow::bail!("Duplicated function rename src {}", src);
}
ret.rename_dsts.insert(dst.clone());
ret.rename_src_to_dst.insert(src, dst);
}
Ok(ret)
}
}
impl Wizer {
/// Construct a new `Wizer` builder.
pub fn new() -> Self {
Wizer {
init_func: "wizer.initialize".into(),
func_renames: vec![],
allow_wasi: false,
preload: vec![],
preload_bytes: vec![],
make_linker: None,
inherit_stdio: None,
inherit_env: None,
keep_init_func: None,
dirs: vec![],
map_dirs: vec![],
wasm_multi_memory: None,
wasm_multi_value: None,
wasm_bulk_memory: None,
wasm_simd: None,
}
}
/// The export name of the initializer function.
///
/// Defaults to `"wizer.initialize"`.
pub fn init_func(&mut self, init_func: impl Into<String>) -> &mut Self {
self.init_func = init_func.into();
self
}
/// Add a function rename to perform.
pub fn func_rename(&mut self, new_name: impl Display, old_name: impl Display) -> &mut Self {
self.func_renames.push(format!("{}={}", new_name, old_name));
self
}
/// Allow WASI imports to be called during initialization?
///
/// This can introduce diverging semantics because the initialization can
/// observe nondeterminism that might have gone a different way at runtime
/// than it did at initialization time.
///
/// If your Wasm module uses WASI's `get_random` to add randomness to
/// something as a security mitigation (e.g. something akin to ASLR or the
/// way Rust's hash maps incorporate a random nonce) then note that, if the
/// randomization is added during initialization time and you don't ever
/// re-randomize at runtime, then that randomization will become per-module
/// rather than per-instance.
///
/// Defaults to `false`.
pub fn allow_wasi(&mut self, allow: bool) -> anyhow::Result<&mut Self> {
anyhow::ensure!(
self.make_linker.is_none(),
"Cannot use 'allow_wasi' with a custom linker"
);
self.allow_wasi = allow;
Ok(self)
}
/// Provide an additional preloaded module that is available to the
/// main module.
///
/// This allows running a module that depends on imports from
/// another module. Note that the additional module's state is *not*
/// snapshotted, nor is its code included in the Wasm snapshot;
/// rather, it is assumed that the resulting snapshot Wasm will also
/// be executed with the same imports available.
///
/// The main purpose of this option is to allow "stubs" for certain
/// intrinsics to be included, when these will be provided with
/// different implementations when running or further processing the
/// snapshot.
pub fn preload(&mut self, name: &str, filename: &str) -> anyhow::Result<&mut Self> {
anyhow::ensure!(
self.make_linker.is_none(),
"Cannot use 'preload' with a custom linker"
);
anyhow::ensure!(
!name.contains("="),
"Module name cannot contain an `=` character"
);
self.preload.push(format!("{}={}", name, filename));
Ok(self)
}
/// Provide an additional preloaded module that is available to the
/// main module. Unlike `preload()`, this method takes an owned
/// vector of bytes as the module's actual content, rather than a
/// filename. As with `preload()`, the module may be in Wasm binary
/// format or in WAT text format.
///
/// This allows running a module that depends on imports from
/// another module. Note that the additional module's state is *not*
/// snapshotted, nor is its code included in the Wasm snapshot;
/// rather, it is assumed that the resulting snapshot Wasm will also
/// be executed with the same imports available.
///
/// The main purpose of this option is to allow "stubs" for certain
/// intrinsics to be included, when these will be provided with
/// different implementations when running or further processing the
/// snapshot.
pub fn preload_bytes(
&mut self,
name: &str,
module_bytes: Vec<u8>,
) -> anyhow::Result<&mut Self> {
anyhow::ensure!(
self.make_linker.is_none(),
"Cannot use 'preload_bytes' with a custom linker"
);
self.preload_bytes.push((name.to_owned(), module_bytes));
Ok(self)
}
/// The linker to use during initialization rather than the default
/// `wasmtime::Linker`.
///
/// If you want your Wasm module to be able to import non-WASI functionality
/// (or a subset of WASI) during initialization, you can provide a closure
/// that returns a `Linker` result. Note, this has the same non-determinism
/// concerns that `.allow_wasi(true)` does: if the allowed imports interact
/// with the world in some way, the outcome of that interaction will be
/// snapshotted by Wizer during initialization and will yield the same result
/// in every instance of the wizened module.
pub fn make_linker(
&mut self,
make_linker: Option<Rc<dyn Fn(&wasmtime::Engine) -> anyhow::Result<Linker>>>,
) -> anyhow::Result<&mut Self> {
anyhow::ensure!(
!self.allow_wasi,
"Cannot use 'allow_wasi' with a custom linker"
);
self.make_linker = make_linker;
Ok(self)
}
/// When using WASI during initialization, should `stdin`, `stdout`, and
/// `stderr` be inherited?
///
/// Defaults to `true`.
pub fn inherit_stdio(&mut self, inherit: bool) -> &mut Self {
self.inherit_stdio = Some(inherit);
self
}
/// When using WASI during initialization, should the environment variables
/// be inherited?
///
/// Defaults to `false`.
pub fn inherit_env(&mut self, inherit: bool) -> &mut Self {
self.inherit_env = Some(inherit);
self
}
/// After initialization, should the Wasm module still export the
/// initialization function?
///
/// This is `false` by default, meaning that the initialization function is
/// no longer exported from the Wasm module.
pub fn keep_init_func(&mut self, keep: bool) -> &mut Self {
self.keep_init_func = Some(keep);
self
}
/// When using WASI during initialization, which file system directories
/// should be made available?
///
/// None are available by default.
pub fn dir(&mut self, directory: impl Into<PathBuf>) -> &mut Self {
self.dirs.push(directory.into());
self
}
/// When using WASI during initialization, which guest directories should be
/// mapped to a host directory?
///
/// The `map_dir` method differs from `dir` in that it allows giving a custom
/// guest name to the directory that is different from its name in the host.
///
/// None are mapped by default.
pub fn map_dir(
&mut self,
guest_dir: impl Into<PathBuf>,
host_dir: impl Into<PathBuf>,
) -> &mut Self {
self.map_dirs.push((guest_dir.into(), host_dir.into()));
self
}
/// Enable or disable the Wasm multi-memory proposal.
///
/// Defaults to `true`.
pub fn wasm_multi_memory(&mut self, enable: bool) -> &mut Self {
self.wasm_multi_memory = Some(enable);
self
}
/// Enable or disable the Wasm multi-value proposal.
///
/// Defaults to `true`.
pub fn wasm_multi_value(&mut self, enable: bool) -> &mut Self {
self.wasm_multi_value = Some(enable);
self
}
/// Enable or disable Wasm bulk memory operations.
///
/// Note that only `memory.copy`, `memory.fill`, and `memory.init`
/// operations are currently supported. Modules which use other
/// instructions, such as `table.copy` will be rejected.
///
/// Defaults to `false`.
pub fn wasm_bulk_memory(&mut self, enable: bool) -> &mut Self {
self.wasm_bulk_memory = Some(enable);
self
}
/// Enable or disable the Wasm SIMD128 proposal.
///
/// Defaults to `true`.
pub fn wasm_simd(&mut self, enable: bool) -> &mut Self {
self.wasm_simd = Some(enable);
self
}
/// Initialize the given Wasm, snapshot it, and return the serialized
/// snapshot as a new, pre-initialized Wasm module.
pub fn run(&self, wasm: &[u8]) -> anyhow::Result<Vec<u8>> {
// Parse rename spec.
let renames = FuncRenames::parse(&self.func_renames)?;
// Make sure we're given valid Wasm from the get go.
self.wasm_validate(&wasm)?;
let mut cx = parse::parse(wasm)?;
let instrumented_wasm = instrument::instrument(&cx);
if cfg!(debug_assertions) {
if let Err(error) = self.wasm_validate(&instrumented_wasm) {
#[cfg(feature = "wasmprinter")]
let wat = wasmprinter::print_bytes(&wasm)
.unwrap_or_else(|e| format!("Disassembling to WAT failed: {}", e));
#[cfg(not(feature = "wasmprinter"))]
let wat = "`wasmprinter` cargo feature is not enabled".to_string();
panic!(
"instrumented Wasm is not valid: {:?}\n\nWAT:\n{}",
error, wat
);
}
}
let config = self.wasmtime_config()?;
let engine = wasmtime::Engine::new(&config)?;
let wasi_ctx = self.wasi_context()?;
let mut store = wasmtime::Store::new(&engine, wasi_ctx);
let module = wasmtime::Module::new(&engine, &instrumented_wasm)
.context("failed to compile the Wasm module")?;
self.validate_init_func(&module)?;
let (instance, has_wasi_initialize) = self.initialize(&engine, &mut store, &module)?;
let snapshot = snapshot::snapshot(&mut store, &instance);
let rewritten_wasm = self.rewrite(
&mut cx,
&mut store,
&snapshot,
&renames,
has_wasi_initialize,
);
if cfg!(debug_assertions) {
if let Err(error) = self.wasm_validate(&rewritten_wasm) {
#[cfg(feature = "wasmprinter")]
let wat = wasmprinter::print_bytes(&wasm)
.unwrap_or_else(|e| format!("Disassembling to WAT failed: {}", e));
#[cfg(not(feature = "wasmprinter"))]
let wat = "`wasmprinter` cargo feature is not enabled".to_string();
panic!("rewritten Wasm is not valid: {:?}\n\nWAT:\n{}", error, wat);
}
}
Ok(rewritten_wasm)
}
// NB: keep this in sync with the wasmparser features.
fn wasmtime_config(&self) -> anyhow::Result<wasmtime::Config> {
let mut config = wasmtime::Config::new();
// Enable Wasmtime's code cache. This makes it so that repeated
// wizenings of the same Wasm module (e.g. with different WASI inputs)
// doesn't require re-compiling the Wasm to native code every time.
config.cache_config_load_default()?;
// Proposals we support.
config.wasm_multi_memory(self.wasm_multi_memory.unwrap_or(DEFAULT_WASM_MULTI_MEMORY));
config.wasm_multi_value(self.wasm_multi_value.unwrap_or(DEFAULT_WASM_MULTI_VALUE));
// Note that we only support `memory.copy`, `memory.fill`, and
// `memory.init` for the time being:
config.wasm_bulk_memory(self.wasm_bulk_memory.unwrap_or(DEFAULT_WASM_BULK_MEMORY));
config.wasm_simd(self.wasm_simd.unwrap_or(DEFAULT_WASM_SIMD));
// Proposals that we should add support for.
config.wasm_reference_types(false);
config.wasm_threads(false);
Ok(config)
}
// NB: keep this in sync with the Wasmtime config.
fn wasm_features(&self) -> wasmparser::WasmFeatures {
wasmparser::WasmFeatures {
mutable_global: true,
saturating_float_to_int: true,
sign_extension: true,
floats: true,
component_model_values: false,
component_model_nested_names: false,
// Proposals that we support.
multi_memory: self.wasm_multi_memory.unwrap_or(DEFAULT_WASM_MULTI_MEMORY),
multi_value: self.wasm_multi_value.unwrap_or(DEFAULT_WASM_MULTI_VALUE),
// Proposals that we should add support for.
reference_types: false,
simd: self.wasm_simd.unwrap_or(DEFAULT_WASM_SIMD),
threads: false,
tail_call: false,
memory64: false,
exceptions: false,
extended_const: false,
relaxed_simd: false,
component_model: false,
memory_control: false,
function_references: false,
gc: false,
// XXX: Though we don't fully support bulk memory yet, we
// unconditionally turn it on.
//
// Many parsers, notably our own `wasmparser`, assume that which
// Wasm features are enabled or disabled cannot affect parsing, only
// validation. That assumption is incorrect when it comes to data
// segments, the multi-memory proposal, and the bulk memory
// proposal. A `0x01` prefix of a data segment can either mean "this
// is a passive segment" if bulk memory is enabled or "this segment
// is referring to memory index 1" if both bulk memory is disabled
// and multi-memory is enabled. `wasmparser` fails to handle this
// edge case, which means that everything built on top of it, like
// Wasmtime, also fail to handle this edge case. However, because
// bulk memory is merged into the spec proper and is no longer
// technically a "proposal", and because a fix would require
// significant refactoring and API changes to give a
// `wasmparser::Parser` a `wasmparser::WasmFeatures`, we won't ever
// resolve this discrepancy in `wasmparser`.
//
// So we enable bulk memory during parsing, validation, and
// execution, but we add our own custom validation pass to ensure
// that no table-mutating instructions exist in our input modules
// until we *actually* support bulk memory.
bulk_memory: true,
}
}
fn wasm_validate(&self, wasm: &[u8]) -> anyhow::Result<()> {
log::debug!("Validating input Wasm");
let mut validator = wasmparser::Validator::new_with_features(self.wasm_features());
validator.validate_all(wasm)?;
// Reject bulk memory stuff that manipulates state we don't
// snapshot. See the comment inside `wasm_features`.
let mut wasm = wasm;
let mut parsers = vec![wasmparser::Parser::new(0)];
while !parsers.is_empty() {
let payload = match parsers.last_mut().unwrap().parse(wasm, true).unwrap() {
wasmparser::Chunk::NeedMoreData(_) => unreachable!(),
wasmparser::Chunk::Parsed { consumed, payload } => {
wasm = &wasm[consumed..];
payload
}
};
match payload {
wasmparser::Payload::CodeSectionEntry(code) => {
let mut ops = code.get_operators_reader().unwrap();
while !ops.eof() {
match ops.read().unwrap() {
wasmparser::Operator::TableCopy { .. } => {
anyhow::bail!("unsupported `table.copy` instruction")
}
wasmparser::Operator::TableInit { .. } => {
anyhow::bail!("unsupported `table.init` instruction")
}
wasmparser::Operator::ElemDrop { .. } => {
anyhow::bail!("unsupported `elem.drop` instruction")
}
wasmparser::Operator::DataDrop { .. } => {
anyhow::bail!("unsupported `data.drop` instruction")
}
wasmparser::Operator::TableSet { .. } => {
unreachable!("part of reference types")
}
_ => continue,
}
}
}
wasmparser::Payload::End(_) => {
parsers.pop();
}
_ => continue,
}
}
Ok(())
}
/// Check that the module exports an initialization function, and that the
/// function has the correct type.
fn validate_init_func(&self, module: &wasmtime::Module) -> anyhow::Result<()> {
log::debug!("Validating the exported initialization function");
match module.get_export(&self.init_func) {
Some(wasmtime::ExternType::Func(func_ty)) => {
if func_ty.params().len() != 0 || func_ty.results().len() != 0 {
anyhow::bail!(
"the Wasm module's `{}` function export does not have type `[] -> []`",
&self.init_func
);
}
}
Some(_) => anyhow::bail!(
"the Wasm module's `{}` export is not a function",
&self.init_func
),
None => anyhow::bail!(
"the Wasm module does not have a `{}` export",
&self.init_func
),
}
Ok(())
}
fn wasi_context(&self) -> anyhow::Result<Option<WasiCtx>> {
if !self.allow_wasi {
return Ok(None);
}
let mut ctx = WasiCtxBuilder::new();
if self.inherit_stdio.unwrap_or(DEFAULT_INHERIT_STDIO) {
ctx.inherit_stdio();
}
if self.inherit_env.unwrap_or(DEFAULT_INHERIT_ENV) {
ctx.inherit_env()?;
}
for dir in &self.dirs {
log::debug!("Preopening directory: {}", dir.display());
let preopened = wasi_common::sync::Dir::open_ambient_dir(
dir,
wasi_common::sync::ambient_authority(),
)
.with_context(|| format!("failed to open directory: {}", dir.display()))?;
ctx.preopened_dir(preopened, dir)?;
}
for (guest_dir, host_dir) in &self.map_dirs {
log::debug!(
"Preopening directory: {}::{}",
guest_dir.display(),
host_dir.display()
);
let preopened = wasi_common::sync::Dir::open_ambient_dir(
host_dir,
wasi_common::sync::ambient_authority(),
)
.with_context(|| format!("failed to open directory: {}", host_dir.display()))?;
ctx.preopened_dir(preopened, guest_dir)?;
}
Ok(Some(ctx.build()))
}
/// Preload a module.
fn do_preload(
&self,
engine: &Engine,
store: &mut Store,
linker: &mut Linker,
name: &str,
content: &[u8],
) -> anyhow::Result<()> {
let module =
wasmtime::Module::new(engine, content).context("failed to parse preload module")?;
let instance = wasmtime::Instance::new(&mut *store, &module, &[])
.context("failed to instantiate preload module")?;
linker
.instance(&mut *store, name, instance)
.context("failed to add preload's exports to linker")?;
Ok(())
}
/// Instantiate the module and call its initialization function.
fn initialize(
&self,
engine: &Engine,
store: &mut Store,
module: &wasmtime::Module,
) -> anyhow::Result<(wasmtime::Instance, bool)> {
log::debug!("Calling the initialization function");
let mut linker = if let Some(make_linker) = self.make_linker.as_deref() {
make_linker(store.engine()).context("failed to make custom linker")?
} else {
wasmtime::Linker::new(store.engine())
};
if self.allow_wasi {
wasi_common::sync::add_to_linker(&mut linker, |ctx: &mut Option<WasiCtx>| {
ctx.as_mut().unwrap()
})?;
}
for preload in &self.preload {
if let Some((name, value)) = preload.split_once('=') {
let content = std::fs::read(value).context("failed to read preload module")?;
self.do_preload(engine, &mut *store, &mut linker, &name[..], &content[..])?;
} else {
anyhow::bail!(
"Bad preload option: {} (must be of form `name=file`)",
preload
);
}
}
for (name, bytes) in &self.preload_bytes {
self.do_preload(engine, &mut *store, &mut linker, &name[..], &bytes[..])?;
}
dummy_imports(&mut *store, &module, &mut linker)?;
let instance = linker
.instantiate(&mut *store, module)
.context("failed to instantiate the Wasm module")?;
let mut has_wasi_initialize = false;
if let Some(export) = instance.get_export(&mut *store, "_initialize") {
if let Extern::Func(func) = export {
func.typed::<(), ()>(&store)
.and_then(|f| {
has_wasi_initialize = true;
f.call(&mut *store, ()).map_err(Into::into)
})
.context("calling the Reactor initialization function")?;
if self.init_func == "_initialize" && has_wasi_initialize {
// Don't run `_initialize` twice if the it was explicitly
// requested as the init function.
return Ok((instance, has_wasi_initialize));
}
}
}
let init_func = instance
.get_typed_func::<(), ()>(&mut *store, &self.init_func)
.expect("checked by `validate_init_func`");
init_func
.call(&mut *store, ())
.with_context(|| format!("the `{}` function trapped", self.init_func))?;
Ok((instance, has_wasi_initialize))
}
}