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Reimplement wasmtime-wasi on top of wasmtime (#899)

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* Reimplement `wasmtime-wasi` on top of `wasmtime`

This commit reimplements the `wasmtime-wasi` crate on top of the
`wasmtime` API crate, instead of being placed on top of the `wasmtime-*`
family of internal crates. The purpose here is to continue to exercise
the API as well as avoid usage of internals wherever possible and
instead use the safe API as much as possible.

The `wasmtime-wasi` crate's API has been updated as part of this PR as
well. The general outline of it is now:

* Each module snapshot has a `WasiCtxBuilder`, `WasiCtx`, and `Wasi`
  type.
  * The `WasiCtx*` types are reexported from `wasi-common`.
  * The `Wasi` type is synthesized by the `wig` crate's procedural macro
* The `Wasi` type exposes one constructor which takes a `Store` and a
  `WasiCtx`, and produces a `Wasi`
* Each `Wasi` struct fields for all the exported functions in that wasi
  module. They're all public an they all have type `wasmtime::Func`
* The `Wasi` type has a `get_export` method to fetch an struct field by
  name.

The intention here is that we can continue to make progress on #727 by
integrating WASI construction into the `Instance::new` experience, but
it requires everything to be part of the same system!

The main oddity required by the `wasmtime-wasi` crate is that it needs
access to the caller's `memory` export, if any. This is currently done
with a bit of a hack and is expected to go away once interface types are
more fully baked in.

* Remove now no-longer-necessary APIs from `wasmtime`

* rustfmt

* Rename to from_abi
This commit is contained in:
Alex Crichton
2020-02-06 09:23:06 -06:00
committed by GitHub
parent c9dce98ba2
commit 3dd5a3cb3f
20 changed files with 284 additions and 488 deletions
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131
crates/wasi/src/instantiate.rs
View File

@@ -1,131 +0,0 @@
use cranelift_codegen::ir::types;
use cranelift_codegen::{ir, isa};
use cranelift_entity::PrimaryMap;
use cranelift_wasm::DefinedFuncIndex;
use std::cell::RefCell;
use std::fs::File;
use std::sync::Arc;
use target_lexicon::HOST;
use wasi_common::hostcalls;
use wasi_common::wasi;
use wasi_common::{WasiCtx, WasiCtxBuilder};
use wasmtime_environ::{translate_signature, Export, Module};
use wasmtime_runtime::{Imports, InstanceHandle, InstantiationError, VMContext};
/// Creates `wasmtime::Instance` object implementing the "wasi" interface.
pub fn create_wasi_instance(
store: &wasmtime::Store,
preopened_dirs: &[(String, File)],
argv: &[String],
environ: &[(String, String)],
) -> Result<wasmtime::Instance, InstantiationError> {
let wasi = instantiate_wasi(preopened_dirs, argv, environ)?;
let instance = wasmtime::Instance::from_handle(&store, wasi);
Ok(instance)
}
/// Return an instance implementing the "wasi" interface.
pub fn instantiate_wasi(
preopened_dirs: &[(String, File)],
argv: &[String],
environ: &[(String, String)],
) -> Result<InstanceHandle, InstantiationError> {
let mut wasi_ctx_builder = WasiCtxBuilder::new()
.inherit_stdio()
.args(argv)
.envs(environ);
for (dir, f) in preopened_dirs {
wasi_ctx_builder = wasi_ctx_builder.preopened_dir(
f.try_clone().map_err(|err| {
InstantiationError::Resource(format!(
"couldn't clone an instance handle to pre-opened dir: {}",
err
))
})?,
dir,
);
}
let wasi_ctx = wasi_ctx_builder.build().map_err(|err| {
InstantiationError::Resource(format!("couldn't assemble WASI context object: {}", err))
})?;
instantiate_wasi_with_context(wasi_ctx)
}
/// Return an instance implementing the "wasi" interface.
///
/// The wasi context is configured by
pub fn instantiate_wasi_with_context(
wasi_ctx: WasiCtx,
) -> Result<InstanceHandle, InstantiationError> {
let pointer_type = types::Type::triple_pointer_type(&HOST);
let mut module = Module::new();
let mut finished_functions = PrimaryMap::new();
let call_conv = isa::CallConv::triple_default(&HOST);
// This function is defined in the macro invocation of
// `define_add_wrappers_to_module` below. For more information about how
// this works it'd recommended to read the source in
// `crates/wasi-common/wig/src/wasi.rs`.
add_wrappers_to_module(
&mut module,
&mut finished_functions,
call_conv,
pointer_type,
);
let imports = Imports::none();
let data_initializers = Vec::new();
let signatures = PrimaryMap::new();
unsafe {
InstanceHandle::new(
Arc::new(module),
finished_functions.into_boxed_slice(),
imports,
&data_initializers,
signatures.into_boxed_slice(),
None,
Box::new(RefCell::new(wasi_ctx)),
)
}
}
wig::define_add_wrappers_to_module!(
"snapshot" "wasi_snapshot_preview1"
);
// Used by `add_wrappers_to_module` defined in the macro above
fn get_wasi_ctx(vmctx: &mut VMContext) -> Result<&RefCell<WasiCtx>, wasi::__wasi_errno_t> {
unsafe {
vmctx
.host_state()
.downcast_ref()
.ok_or_else(|| panic!("no host state named WasiCtx available"))
}
}
// Used by `add_wrappers_to_module` defined in the macro above
fn get_memory(caller_vmctx: &mut VMContext) -> Result<&mut [u8], wasi::__wasi_errno_t> {
match unsafe { InstanceHandle::from_vmctx(caller_vmctx) }.lookup("memory") {
Some(wasmtime_runtime::Export::Memory {
definition,
vmctx: _,
memory: _,
}) => unsafe {
let definition = &*definition;
let ptr = definition.base;
let len = definition.current_length;
Ok(std::slice::from_raw_parts_mut(ptr, len))
},
Some(export) => {
log::error!("export named \"memory\" isn't a memory: {:?}", export);
Err(wasi::__WASI_ERRNO_INVAL)
}
None => {
log::error!("no export named \"memory\" available from caller");
Err(wasi::__WASI_ERRNO_INVAL)
}
}
}

62
crates/wasi/src/lib.rs
View File

@@ -1,7 +1,14 @@
mod instantiate;
pub mod old;
pub use instantiate::{create_wasi_instance, instantiate_wasi, instantiate_wasi_with_context};
use wasi_common::hostcalls;
pub use wasi_common::{WasiCtx, WasiCtxBuilder};
// Defines a `struct Wasi` with member fields and appropriate APIs for dealing
// with all the various WASI exports.
wig::define_wasi_struct!(
"snapshot" "wasi_snapshot_preview1"
);
pub fn is_wasi_module(name: &str) -> bool {
// FIXME: this should be more conservative, but while WASI is in flux and
@@ -9,3 +16,54 @@ pub fn is_wasi_module(name: &str) -> bool {
// trick.
name.starts_with("wasi")
}
/// This is an internal structure used to acquire a handle on the caller's
/// wasm memory buffer.
///
/// This exploits how we can implement `WasmArg` for ourselves locally even
/// though crates in general should not be doing that. This is a crate in
/// the wasmtime project, however, so we should be able to keep up with our own
/// changes.
///
/// In general this type is wildly unsafe. We need to update the wasi crates to
/// probably work with more `wasmtime`-like APIs to grip with the unsafety
/// around dealing with caller memory.
struct WasiCallerMemory {
base: *mut u8,
len: usize,
}
impl wasmtime::WasmArg for WasiCallerMemory {
type Abi = ();
fn push(_dst: &mut Vec<wasmtime::ValType>) {}
fn from_abi(vmctx: *mut wasmtime_runtime::VMContext, _abi: ()) -> Self {
unsafe {
match wasmtime_runtime::InstanceHandle::from_vmctx(vmctx).lookup("memory") {
Some(wasmtime_runtime::Export::Memory {
definition,
vmctx: _,
memory: _,
}) => WasiCallerMemory {
base: (*definition).base,
len: (*definition).current_length,
},
_ => WasiCallerMemory {
base: std::ptr::null_mut(),
len: 0,
},
}
}
}
}
impl WasiCallerMemory {
unsafe fn get(&self) -> Result<&mut [u8], wasi_common::wasi::__wasi_errno_t> {
if self.base.is_null() {
Err(wasi_common::wasi::__WASI_ERRNO_INVAL)
} else {
Ok(std::slice::from_raw_parts_mut(self.base, self.len))
}
}
}

15
crates/wasi/src/old/snapshot_0.rs Normal file
View File

@@ -0,0 +1,15 @@
use wasi_common::old::snapshot_0::hostcalls;
use wasi_common::old::snapshot_0::WasiCtx;
// Defines a `struct Wasi` with member fields and appropriate APIs for dealing
// with all the various WASI exports.
wig::define_wasi_struct!(
"old/snapshot_0" "wasi_unstable"
);
pub fn is_wasi_module(name: &str) -> bool {
// FIXME: this should be more conservative, but while WASI is in flux and
// we're figuring out how to support multiple revisions, this should do the
// trick.
name.starts_with("wasi")
}

131
crates/wasi/src/old/snapshot_0/instantiate.rs
View File

@@ -1,131 +0,0 @@
use cranelift_codegen::ir::types;
use cranelift_codegen::{ir, isa};
use cranelift_entity::PrimaryMap;
use cranelift_wasm::DefinedFuncIndex;
use std::cell::RefCell;
use std::fs::File;
use std::sync::Arc;
use target_lexicon::HOST;
use wasi_common::old::snapshot_0::hostcalls;
use wasi_common::old::snapshot_0::wasi;
use wasi_common::old::snapshot_0::{WasiCtx, WasiCtxBuilder};
use wasmtime_environ::{translate_signature, Export, Module};
use wasmtime_runtime::{Imports, InstanceHandle, InstantiationError, VMContext};
/// Creates `wasmtime::Instance` object implementing the "wasi" interface.
pub fn create_wasi_instance(
store: &wasmtime::Store,
preopened_dirs: &[(String, File)],
argv: &[String],
environ: &[(String, String)],
) -> Result<wasmtime::Instance, InstantiationError> {
let wasi = instantiate_wasi(preopened_dirs, argv, environ)?;
let instance = wasmtime::Instance::from_handle(&store, wasi);
Ok(instance)
}
/// Return an instance implementing the "wasi" interface.
pub fn instantiate_wasi(
preopened_dirs: &[(String, File)],
argv: &[String],
environ: &[(String, String)],
) -> Result<InstanceHandle, InstantiationError> {
let mut wasi_ctx_builder = WasiCtxBuilder::new()
.inherit_stdio()
.args(argv)
.envs(environ);
for (dir, f) in preopened_dirs {
wasi_ctx_builder = wasi_ctx_builder.preopened_dir(
f.try_clone().map_err(|err| {
InstantiationError::Resource(format!(
"couldn't clone an instance handle to pre-opened dir: {}",
err
))
})?,
dir,
);
}
let wasi_ctx = wasi_ctx_builder.build().map_err(|err| {
InstantiationError::Resource(format!("couldn't assemble WASI context object: {}", err))
})?;
instantiate_wasi_with_context(wasi_ctx)
}
/// Return an instance implementing the "wasi" interface.
///
/// The wasi context is configured by
pub fn instantiate_wasi_with_context(
wasi_ctx: WasiCtx,
) -> Result<InstanceHandle, InstantiationError> {
let pointer_type = types::Type::triple_pointer_type(&HOST);
let mut module = Module::new();
let mut finished_functions = PrimaryMap::new();
let call_conv = isa::CallConv::triple_default(&HOST);
// This function is defined in the macro invocation of
// `define_add_wrappers_to_module` below. For more information about how
// this works it'd recommended to read the source in
// `crates/wasi-common/wig/src/wasi.rs`.
add_wrappers_to_module(
&mut module,
&mut finished_functions,
call_conv,
pointer_type,
);
let imports = Imports::none();
let data_initializers = Vec::new();
let signatures = PrimaryMap::new();
unsafe {
InstanceHandle::new(
Arc::new(module),
finished_functions.into_boxed_slice(),
imports,
&data_initializers,
signatures.into_boxed_slice(),
None,
Box::new(RefCell::new(wasi_ctx)),
)
}
}
// Used by `add_wrappers_to_module` defined in the macro above
fn get_wasi_ctx(vmctx: &mut VMContext) -> Result<&RefCell<WasiCtx>, wasi::__wasi_errno_t> {
unsafe {
vmctx
.host_state()
.downcast_ref()
.ok_or_else(|| panic!("no host state named WasiCtx available"))
}
}
// Used by `add_wrappers_to_module` defined in the macro above
fn get_memory(caller_vmctx: &mut VMContext) -> Result<&mut [u8], wasi::__wasi_errno_t> {
match unsafe { InstanceHandle::from_vmctx(caller_vmctx) }.lookup("memory") {
Some(wasmtime_runtime::Export::Memory {
definition,
vmctx: _,
memory: _,
}) => unsafe {
let definition = &*definition;
let ptr = definition.base;
let len = definition.current_length;
Ok(std::slice::from_raw_parts_mut(ptr, len))
},
Some(export) => {
log::error!("export named \"memory\" isn't a memory: {:?}", export);
Err(wasi::__WASI_ERRNO_INVAL)
}
None => {
log::error!("no export named \"memory\" available from caller");
Err(wasi::__WASI_ERRNO_INVAL)
}
}
}
wig::define_add_wrappers_to_module!(
"old/snapshot_0" "wasi_unstable"
);

12
crates/wasi/src/old/snapshot_0/mod.rs
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@@ -1,12 +0,0 @@
extern crate alloc;
mod instantiate;
pub use instantiate::{create_wasi_instance, instantiate_wasi, instantiate_wasi_with_context};
pub fn is_wasi_module(name: &str) -> bool {
// FIXME: this should be more conservative, but while WASI is in flux and
// we're figuring out how to support multiple revisions, this should do the
// trick.
name.starts_with("wasi")
}