* implement wasmtime::component::flags! per #4308
This is the last macro needed to complete #4308. It supports generating a Rust
type that represents a `flags` component type, analogous to how the [bitflags
crate](https://crates.io/crates/bitflags) operates.
Signed-off-by: Joel Dice <joel.dice@fermyon.com>
* wrap `format_flags` output in parens
This ensures we generate non-empty output even when no flags are set. Empty
output for a `Debug` implementation would be confusing.
Signed-off-by: Joel Dice <joel.dice@fermyon.com>
* unconditionally derive `Lift` and `Lower` in wasmtime::component::flags!
Per feedback on #4414, we now derive impls for those traits unconditionally,
which simplifies the syntax of the macro.
Also, I happened to notice an alignment bug in `LowerExpander::expand_variant`,
so I fixed that and cleaned up some related code.
Finally, I used @jameysharp's trick to calculate bit masks without looping.
Signed-off-by: Joel Dice <joel.dice@fermyon.com>
* fix shift overflow regression in previous commit
Jamey pointed out my mistake: I didn't consider the case when the flag count was
evenly divisible by the representation size. This fixes the problem and adds
test cases to cover it.
Signed-off-by: Joel Dice <joel.dice@fermyon.com>
This commit removes Wasmtime's dependency on the `region` crate. The
motivation for this came about when I was updating dependencies and saw
that `region` had a new major version at 3.0.0 as opposed to our
currently used 2.3 track. In reviewing the use cases of `region` within
Wasmtime I found two trends in particular which motivated this commit:
* Some unix-specific areas of `wasmtime_runtime` use
`rustix::mm::mprotect` instead of `region::protect` already. This
means that the usage of `region::protect` for changing virtual memory
protections was already inconsistent.
* Many uses of `region::protect` were already in unix-specific regions
which could make use of `rustix`.
Overall I opted to remove the dependency on the `region` crate to avoid
chasing its versions over time. Unix-specific changes of protections
were easily changed to `rustix::mm::mprotect`. There were two locations
where a windows/unix split is now required and I subjectively ruled
"that seems ok". Finally removing `region` also meant that the "what is
the current page size" query needed to be inlined into
`wasmtime_runtime`, which I have also subjectively ruled "that seems
fine".
Finally one final refactoring here was that the `unix.rs` and `linux.rs`
split for the pooling allocator was merged. These two files already only
differed in one function so I slapped a `cfg_if!` in there to help
reduce the duplication.
* wasmtime: Rename host->wasm trampolines
As we introduce new types of trampolines, having clear names for our existing
trampolines will be helpful.
* Fix typo in docs for `VMCOMPONENT_MAGIC`
* wasmtime: Add criterion micro benchmarks for traps
* Bump versions of wasm-tools crates
Note that this leaves new features in the component model, outer type
aliases for core wasm types, unimplemented for now.
* Move to crates.io-based versions of tools
* Update tracing-core to a version which doesn't depend on lazy-static.
* Update crossbeam-utils to a version that doesn't depend on lazy-static.
* Update crossbeam-epoch to a version that doesn't depend on lazy-static.
* Update clap to a version that doesn't depend on lazy-static.
* Convert Wasmtime's own use of lazy_static to once_cell.
* Make `GDB_REGISTRATION`'s comment a doc comment.
* Fix compilation on Windows.
This commit adds support to Wasmtime for components which themselves
export instances. The support here adds new APIs for how instance
exports are accessed in the embedding API. For now this is mostly just a
first-pass where the API is somewhat confusing and has a lot of
lifetimes. I'm hoping that over time we can figure out how to simplify
this but for now it should at least be expressive enough for exploring
the exports of an instance.
* support variant, enum, and union derives
This is the second stage of implementing #4308. It adds support for deriving
variant, enum, and union impls for `ComponentType`, `Lift`, and `Lower`. It
also fixes derived record impls for generic `struct`s, which I had intended to
support in my previous commit, but forgot to test.
Signed-off-by: Joel Dice <joel.dice@fermyon.com>
* deduplicate component-macro code
Thanks to @jameysharp for the suggestion!
Signed-off-by: Joel Dice <joel.dice@fermyon.com>
* Wasmtime: disable unwind_info unless needed
fixes#4350
Otherwise wasm modules will be built with unwind info, even if
backtraces are disabled. This can get expensive in deeply recursive
modules.
* Wasmtime: test that disabling backtraces disables unwind_info
* fix: make sure we have unwind_info when the engine needs it
This commit updates the management of the `may_enter` flag in line with
WebAssembly/component-model#57. Namely the `may_enter` flag is now
exclusively managed in the `canon lift` function (which is
`TypedFunc::call`) and is only unset after post-return completes
successfully. This implements semantics where if any trap happens for
any reason (lifting, lowering, execution, imports, etc) then the
instance is considered permanently poisoned and can no longer be
entered.
Tests needed many updates to create new instances where previously the
same instance was reused after it had an erroneous state.
The more I read over this again the more I think that these should be
constants to explicitly indicate that we're supposed to be able to
optimize for them. Currently I'm predicting that adding memory64 support
will probably double the surface area of each trait (e.g. `lower32` and
`lower64`) rather than have a parameter passed around. This is in the
hopes that having specialized 32 and 64-bit paths will enable better
optimizations within each path instead of having to check all bounds
everywhere.
Additionally one day I'd like to have `fn load(bytes: &[u8;
Self::SIZE32])` but that doesn't work today in Rust.
* Implement `canon lower` of a `canon lift` function in the same component
This commit implements the "degenerate" logic for implementing a
function within a component that is lifted and then immediately lowered
again. In this situation the lowered function will immediately generate
a trap and doesn't need to implement anything else.
The implementation in this commit is somewhat heavyweight but I think is
probably justified moreso in future additions to the component model
rather than what exactly is here right now. It's not expected that this
"always trap" functionality will really be used all that often since it
would generally mean a buggy component, but the functionality plumbed
through here is hopefully going to be useful for implementing
component-to-component adapter trampolines.
Specifically this commit implements a strategy where the `canon.lower`'d
function is generated by Cranelift and simply has a single trap
instruction when called, doing nothing else. The main complexity comes
from juggling around all the data associated with these functions,
primarily plumbing through the traps into the `ModuleRegistry` to
ensure that the global `is_wasm_trap_pc` function returns `true` and at
runtime when we lookup information about the trap it's all readily
available (e.g. translating the trapping pc to a `TrapCode`).
* Fix non-component build
* Fix some offset calculations
* Only create one "always trap" per signature
Use an internal map to deduplicate during compilation.
This is the first stage of implementing
https://github.com/bytecodealliance/wasmtime/issues/4308, i.e. derive macros for
`ComponentType`, `Lift`, and `Lower` for composite types in the component model.
This stage only covers records; I expect the other composite types will follow a
similar pattern.
It borrows heavily from the work Jamey Sharp did in
https://github.com/bytecodealliance/wasmtime/pull/4217. Thanks for that, and
thanks to both Jamey and Alex Crichton for their excellent review feedback.
Thanks also to Brian for pairing up on the initial draft.
Signed-off-by: Joel Dice <joel.dice@fermyon.com>
* Implement lowered-then-lifted functions
This commit is a few features bundled into one, culminating in the
implementation of lowered-then-lifted functions for the component model.
It's probably not going to be used all that often but this is possible
within a valid component so Wasmtime needs to do something relatively
reasonable. The main things implemented in this commit are:
* Component instances are now assigned a `RuntimeComponentInstanceIndex`
to differentiate each one. This will be used in the future to detect
fusion (one instance lowering a function from another instance). For
now it's used to allocate separate `VMComponentFlags` for each
internal component instance.
* The `CoreExport<FuncIndex>` of lowered functions was changed to a
`CoreDef` since technically a lowered function can use another lowered
function as the callee. This ended up being not too difficult to plumb
through as everything else was already in place.
* A need arose to compile host-to-wasm trampolines which weren't already
present. Currently wasm in a component is always entered through a
host-to-wasm trampoline but core wasm modules are the source of all
the trampolines. In the case of a lowered-then-lifted function there
may not actually be any core wasm modules, so component objects now
contain necessary trampolines not otherwise provided by the core wasm
objects. This feature required splitting a new function into the
`Compiler` trait for creating a host-to-wasm trampoline. After doing
this core wasm compilation was also updated to leverage this which
further enabled compiling trampolines in parallel as opposed to the
previous synchronous compilation.
* Review comments
* Migrate from `winapi` to `windows-sys`
I believe that Microsoft itself is supporting the development of
`windows-sys` and it's also used by `cap-std` now so this switches
Wasmtime's dependencies on Windows APIs from the `winapi` crate to the
`windows-sys` crate. We still have `winapi` in our dependency graph but
that may get phased out over time.
* Make windows-sys a target-specific dependency
* Improve error message for failed function compiles
Add in the wasm function index, the name if specified, and the function
offset in the original file to assist in debugging failed function compiles.
* Review commments
This commit extends the `WasmList<T>` type to have an
`as_slice`-lookalike method (now renamed to `as_le_slice`) for all
integer types rather than just the `u8` type. With the guarantees of the
component model it's known that all lists are aligned in linear memory.
Additionally linear memories themselves are also generally guaranteed to
be aligned. This means that hosts where the primitive integer alignment
is at most the size (which I think is basically all host platforms) can
get a raw view into memory for the wasm linear memory for slices of
these types.
Note, though, that the remaining caveat after alignment is endianness.
Big-endian hosts need to be aware that the integers aren't stored in a
native format. Previously tools like wit-bindgen have added an `Le<T>`
wrapper but for now I've opted to instead use a method that has "le" in
the name - `as_le_slice`. I'm hoping that this is a clear enough
indicator for users to little-endian conversions as appropriate when
reading the values within the slice.
Previous to this commit Wasmtime would use the `GlobalModuleRegistry`
when learning information about a trap such as its trap code, the
symbols for each frame, etc. This has a downside though of holding a
global read-write lock for the duration of this operation which hinders
registration of new modules in parallel. In addition there was a fair
amount of internal duplication between this "global module registry" and
the store-local module registry. Finally relying on global state for
information like this gets a bit more brittle over time as it seems best
to scope global queries to precisely what's necessary rather than
holding extra information.
With the refactoring in wasm backtraces done in #4183 it's now possible
to always have a `StoreOpaque` reference when a backtrace is collected
for symbolication and otherwise Trap-identification purposes. This
commit adds a `StoreOpaque` parameter to the `Trap::from_runtime`
constructor and then plumbs that everywhere. Note that while doing this
I changed the internal `traphandlers::lazy_per_thread_init` function to
no longer return a `Result` and instead just `panic!` on Unix if memory
couldn't be allocated for a stack. This removed quite a lot of
error-handling code for a case that's expected to quite rarely happen.
If necessary in the future we can add a fallible initialization point
but this feels like a better default balance for the code here.
With a `StoreOpaque` in use when a trap is being symbolicated that means
we have a `ModuleRegistry` which can be used for queries and such. This
meant that the `GlobalModuleRegistry` state could largely be dismantled
and moved to per-`Store` state (within the `ModuleRegistry`, mostly just
moving methods around).
The final state is that the global rwlock is not exclusively scoped
around insertions/deletions/`is_wasm_trap_pc` which is just a lookup and
atomic add. Otherwise symbolication for a backtrace exclusively uses
store-local state now (as intended).
The original motivation for this commit was that frame information
lookup and pieces were looking to get somewhat complicated with the
addition of components which are a new vector of traps coming out of
Cranelift-generated code. My hope is that by having a `Store` around for
more operations it's easier to plumb all this through.
Currently `cargo doc` fails for a number of broken links and this commit
fixes all of them. Currently I don't think it's worth adding this to CI
because we don't actually generate docs for the component model anywhere
yet. When the component model support is compiled in by default I think
it would make sense to implement that.
This commit is a small refactoring of `wasmtime_runtime::Trap` and
various internals. The `Trap` structure is now a reason plus backtrace,
and the old `Trap` enum is mostly in `TrapReason` now. Additionally all
`Trap`-returning methods of `wasmtime_runtime` are changed to returning
a `TrapCode` to indicate that they never capture a backtrace. Finally
the `UnwindReason` internally now no longer duplicates the trap reasons,
instead only having two variants of "panic" and "trap".
The motivation for this commit is mostly just cleaning up trap internals
and removing the need for methods like
`wasmtime_runtime::Trap::insert_backtrace` to leave it only happening at
the `wasmtime` layer.
* Add a method to Linker and flag to wasmtime-cli to trap unknown import funcs
Sometimes users have a Command module which imports functions unknown to
the wasmtime-cli, but does not call them at runtime. This PR provides a
convenience method on Linker to define all unknown import functions in
a given Module as a trivial implementation which traps, and hooks this
up to a new cli flag --trap-unknown-imports.
* add cfg guards - func_new requires compiler (naturally)
This commit implements the `post-return` feature of the canonical ABI in
the component model. This attribute is an optionally-specified function
which is to be executed after the return value has been processed by the
caller to optionally clean-up the return value. This enables, for
example, returning an allocated string and the host then knows how to
clean it up to prevent memory leaks in the original module.
The API exposed in this PR changes the prior `TypedFunc::call` API in
behavior but not in its signature. Previously the `TypedFunc::call`
method would set the `may_enter` flag on the way out, but now that
operation is deferred until a new `TypedFunc::post_return` method is
called. This means that once a method on an instance is invoked then
nothing else can be done on the instance until the `post_return` method
is called. Note that the method must be called irrespective of whether
the `post-return` canonical ABI option was specified or not. Internally
wasm will be invoked if necessary.
This is a pretty wonky and unergonomic API to work with. For now I
couldn't think of a better alternative that improved on the ergonomics.
In the theory that the raw Wasmtime bindings for a component may not be
used all that heavily (instead `wit-bindgen` would largely be used) I'm
hoping that this isn't too much of an issue in the future.
cc #4185
One test case I wrote recently was to import a lowered function into a
wasm module and then immediately export it. This previously didn't work
because trampoline lookup would fail as the original
`VMCallerCheckedAnyfunc` function pointer points into the
`trampoline_obj` of a component which wasn't registered with the
`ModuleRegistry`. This plumbs through the necessary configuration to get
that all hooked up.
* Document a caveat regarding `max_wasm_stack`
Specifically, that the `max_wasm_stack` only limits the stack that can
be consumed by wasm, but it does not guarantee that the so much stack
space will be available.
* rustfmt
* Fix the claim about reseting the stack limit.
Cargo recently added the ability to have an optional dependency without
implicitly introducing a new named feature on a crate. This is triggered
with some new directives in the `[features]` section, specifically:
* The `dep:foo` syntax means that `foo` is activated but no implicit
feature should be added named `foo`.
* Additionally `foo?/bar` means that the `bar` feature of `foo` is only
activated if `foo` is otherwise activated elsewhere, for example a
conditional activation.
These two features can help avoid extra feature names showing up that we
don't want (e.g. currently the `wasmtime` crate has a `rayon` feature)
and additionally can help avoid runtime dependencies in niche cases for
us (e.g. activating `all-arch` but disabling `cranelift` would
previously pull-in cranelift but no longer will).
* Add support for nested components
This commit is an implementation of a number of features of the
component model including:
* Defining nested components
* Outer aliases to components and modules
* Instantiating nested components
The implementation here is intended to be a foundational pillar of
Wasmtime's component model support since recursion and nested components
are the bread-and-butter of the component model. At a high level the
intention for the component model implementation in Wasmtime has long
been that the recursive nature of components is "erased" at compile time
to something that's more optimized and efficient to process. This commit
ended up exemplifying this quite well where the vast majority of the
internal changes here are in the "compilation" phase of a component
rather than the runtime instantiation phase. The support in the
`wasmtime` crate, the runtime instantiation support, only had minor
updates here while the internals of translation have seen heavy updates.
The `translate` module was greatly refactored here in this commit.
Previously it would, as a component is parsed, create a final
`Component` to hand off to trampoline compilation and get persisted at
runtime. Instead now it's a thin layer over `wasmparser` which simply
records a list of `LocalInitializer` entries for how to instantiate the
component and its index spaces are built. This internal representation
of the instantiation of a component is pretty close to the binary format
intentionally.
Instead of performing dataflow legwork the `translate` phase of a
component is now responsible for two primary tasks:
1. All components and modules are discovered within a component. They're
assigned `Static{Component,Module}Index` depending on where they're
found and a `{Module,}Translation` is prepared for each one. This
"flattens" the recursive structure of the binary into an indexed list
processable later.
2. The lexical scope of components is managed here to implement outer
module and component aliases. This is a significant design
implementation because when closing over an outer component or module
that item may actually be imported or something like the result of a
previous instantiation. This means that the capture of
modules and components is both a lexical concern as well as a runtime
concern. The handling of the "runtime" bits are handled in the next
phase of compilation.
The next and currently final phase of compilation is a new pass where
much of the historical code in `translate.rs` has been moved to (but
heavily refactored). The goal of compilation is to produce one "flat"
list of initializers for a component (as happens prior to this PR) and
to achieve this an "inliner" phase runs which runs through the
instantiation process at compile time to produce a list of initializers.
This `inline` module is the main addition as part of this PR and is now
the workhorse for dataflow analysis and tracking what's actually
referring to what.
During the `inline` phase the local initializers recorded in the
`translate` phase are processed, in sequence, to instantiate a
component. Definitions of items are tracked to correspond to their root
definition which allows seeing across instantiation argument boundaries
and such. Handling "upvars" for component outer aliases is handled in
the `inline` phase as well by creating state for a component whenever a
component is defined as was recorded during the `translate` phase.
Finally this phase is chiefly responsible for doing all string-based
name resolution at compile time that it can. This means that at runtime
no string maps will need to be consulted for item exports and such.
The final result of inlining is a list of "global initializers" which is
a flat list processed during instantiation time. These are almost
identical to the initializers that were processed prior to this PR.
There are certainly still more gaps of the component model to implement
but this should be a major leg up in terms of functionality that
Wasmtime implements. This commit, however leaves behind a "hole" which
is not intended to be filled in at this time, namely importing and
exporting components at the "root" level from and to the host. This is
tracked and explained in more detail as part of #4283.
cc #4185 as this completes a number of items there
* Tweak code to work on stable without warning
* Review comments
* Decouple some more `Config` methods from each other
This commit decouples validation of stack sizes and guard sizes until
`Engine::new` to avoid odd interactions between the order of invocation
of `Config` methods.
* Fix C API
* Typos
This commit refactored `Config` to use a seperate `CompilerConfig` field instead
of operating on `CompilerBuilder` directly to make all its methods idempotent.
Fixes#4189
This commit updates the wasm-tools family of crates, notably pulling in
the refactorings and updates from bytecodealliance/wasm-tools#621 for
the latest iteration of the component model. This commit additionally
updates all support for the component model for these changes, notably:
* Many bits and pieces of type information was refactored. Many
`FooTypeIndex` namings are now `TypeFooIndex`. Additionally there is
now `TypeIndex` as well as `ComponentTypeIndex` for the two type index
spaces in a component.
* A number of new sections are now processed to handle the core and
component variants.
* Internal maps were split such as the `funcs` map into
`component_funcs` and `funcs` (same for `instances`).
* Canonical options are now processed individually instead of one bulk
`into` definition.
Overall this was not a major update to the internals of handling the
component model in Wasmtime. Instead this was mostly a surface-level
refactoring to make sure that everything lines up with the new binary
format for components.
* All text syntax used in tests was updated to the new syntax.
* Add shared memories
This change adds the ability to use shared memories in Wasmtime when the
[threads proposal] is enabled. Shared memories are annotated as `shared`
in the WebAssembly syntax, e.g., `(memory 1 1 shared)`, and are
protected from concurrent access during `memory.size` and `memory.grow`.
[threads proposal]: https://github.com/WebAssembly/threads/blob/master/proposals/threads/Overview.md
In order to implement this in Wasmtime, there are two main cases to
cover:
- a program may simply create a shared memory and possibly export it;
this means that Wasmtime itself must be able to create shared
memories
- a user may create a shared memory externally and pass it in as an
import during instantiation; this is the case when the program
contains code like `(import "env" "memory" (memory 1 1
shared))`--this case is handled by a new Wasmtime API
type--`SharedMemory`
Because of the first case, this change allows any of the current
memory-creation mechanisms to work as-is. Wasmtime can still create
either static or dynamic memories in either on-demand or pooling modes,
and any of these memories can be considered shared. When shared, the
`Memory` runtime container will lock appropriately during `memory.size`
and `memory.grow` operations; since all memories use this container, it
is an ideal place for implementing the locking once and once only.
The second case is covered by the new `SharedMemory` structure. It uses
the same `Mmap` allocation under the hood as non-shared memories, but
allows the user to perform the allocation externally to Wasmtime and
share the memory across threads (via an `Arc`). The pointer address to
the actual memory is carefully wired through and owned by the
`SharedMemory` structure itself. This means that there are differing
views of where to access the pointer (i.e., `VMMemoryDefinition`): for
owned memories (the default), the `VMMemoryDefinition` is stored
directly by the `VMContext`; in the `SharedMemory` case, however, this
`VMContext` must point to this separate structure.
To ensure that the `VMContext` can always point to the correct
`VMMemoryDefinition`, this change alters the `VMContext` structure.
Since a `SharedMemory` owns its own `VMMemoryDefinition`, the
`defined_memories` table in the `VMContext` becomes a sequence of
pointers--in the shared memory case, they point to the
`VMMemoryDefinition` owned by the `SharedMemory` and in the owned memory
case (i.e., not shared) they point to `VMMemoryDefinition`s stored in a
new table, `owned_memories`.
This change adds an additional indirection (through the `*mut
VMMemoryDefinition` pointer) that could add overhead. Using an imported
memory as a proxy, we measured a 1-3% overhead of this approach on the
`pulldown-cmark` benchmark. To avoid this, Cranelift-generated code will
special-case the owned memory access (i.e., load a pointer directly to
the `owned_memories` entry) for `memory.size` so that only
shared memories (and imported memories, as before) incur the indirection
cost.
* review: remove thread feature check
* review: swap wasmtime-types dependency for existing wasmtime-environ use
* review: remove unused VMMemoryUnion
* review: reword cross-engine error message
* review: improve tests
* review: refactor to separate prevent Memory <-> SharedMemory conversion
* review: into_shared_memory -> as_shared_memory
* review: remove commented out code
* review: limit shared min/max to 32 bits
* review: skip imported memories
* review: imported memories are not owned
* review: remove TODO
* review: document unsafe send + sync
* review: add limiter assertion
* review: remove TODO
* review: improve tests
* review: fix doc test
* fix: fixes based on discussion with Alex
This changes several key parts:
- adds memory indexes to imports and exports
- makes `VMMemoryDefinition::current_length` an atomic usize
* review: add `Extern::SharedMemory`
* review: remove TODO
* review: atomically load from VMMemoryDescription in JIT-generated code
* review: add test probing the last available memory slot across threads
* fix: move assertion to new location due to rebase
* fix: doc link
* fix: add TODOs to c-api
* fix: broken doc link
* fix: modify pooling allocator messages in tests
* review: make owned_memory_index panic instead of returning an option
* review: clarify calculation of num_owned_memories
* review: move 'use' to top of file
* review: change '*const [u8]' to '*mut [u8]'
* review: remove TODO
* review: avoid hard-coding memory index
* review: remove 'preallocation' parameter from 'Memory::_new'
* fix: component model memory length
* review: check that shared memory plans are static
* review: ignore growth limits for shared memory
* review: improve atomic store comment
* review: add FIXME for memory growth failure
* review: add comment about absence of bounds-checked 'memory.size'
* review: make 'current_length()' doc comment more precise
* review: more comments related to memory.size non-determinism
* review: make 'vmmemory' unreachable for shared memory
* review: move code around
* review: thread plan through to 'wrap()'
* review: disallow shared memory allocation with the pooling allocator
This commit updates the implementation of `ComponentType for ()` to
typecheck both the empty tuple type in addition to the `unit` type in
the component model. This allows the usage of `()` when either of those
types are used. Currently this can work because we don't need to
currently support the answer of "what is the type of this host
function". Instead the only question that needs to be answered at
runtime is "does this host function match this type".
This commit updates the lifting and lowering done by Wasmtime to
validate that alignment is all correct. Previously alignment was ignored
because I wasn't sure how this would all work out.
To be extra safe I haven't actually modified any loads/stores and
they're all still unaligned. If this becomes a performance issue we can
investigate aligned loads and stores but otherwise I believe the
requisite locations have been guarded with traps and I've also added
debug asserts to catch possible future mistakes.
This commit updates lifting for integer types and boolean types to
account for WebAssembly/component-model#35 where extra bits are now
discarded instead of being validated as all zero.
This commit splits the current `ComponentValue` trait into three
separate traits:
* `ComponentType` - contains size/align/typecheck information in
addition to the "lower" representation.
* `Lift` - only contains `lift` and `load`
* `Lower` - only contains `lower` and `store`
When describing the original implementation of host functions to Nick he
immediately pointed out this superior solution to the traits involved
with Wasmtime's support for typed parameters/returns in exported and
imported functions. Instead of having dynamic errors at runtime for
things like "you can't lift a `String`" that's instead a static
compile-time error now.
While I was doing this split I also refactored the `ComponentParams`
trait a bit to have `ComponentType` as a supertrait instead of a subtype
which made its implementations a bit more compact. Additionally its impl
blocks were folded into the existing tuple impl blocks.
* Enable passing host functions to components
This commit implements the ability to pass a host function into a
component. The `wasmtime::component::Linker` type now has a `func_wrap`
method allowing it to take a host function which is exposed internally
to the component and available for lowering.
This is currently mostly a "let's get at least the bare minimum working"
implementation. That involves plumbing around lots of various bits of
the canonical ABI and getting all the previous PRs to line up in this
one to get a test where we call a function where the host takes a
string. This PR also additionally starts reading and using the
`may_{enter,leave}` flags since this is the first time they're actually
relevant.
Overall while this is the bare bones of working this is not a final spot
we should end up at. One of the major downsides is that host functions
are represented as:
F: Fn(StoreContextMut<'_, T>, Arg1, Arg2, ...) -> Result<Return>
while this naively seems reasonable this critically doesn't allow
`Return` to actually close over any of its arguments. This means that if
you want to return a string to wasm then it has to be `String` or
`Rc<str>` or some other owned type. In the case of `String` this means
that to return a string to wasm you first have to copy it from the host
to a temporary `String` allocation, then to wasm. This extra copy for
all strings/lists is expected to be prohibitive. Unfortuantely I don't
think Rust is able to solve this, at least on stable, today.
Nevertheless I wanted to at least post this to get some feedback on it
since it's the final step in implementing host imports to see how others
feel about it.
* Fix a typo in an assertion
* Fix some typos
* Review comments
* Add a `VMComponentContext` type and create it on instantiation
This commit fills out the `wasmtime-runtime` crate's support for
`VMComponentContext` and creates it as part of the instantiation
process. This moves a few maps that were temporarily allocated in an
`InstanceData` into the `VMComponentContext` and additionally reads the
canonical options data from there instead.
This type still won't be used in its "full glory" until the lowering of
host functions is completely implemented, however, which will be coming
in a future commit.
* Remove `DerefMut` implementation
* Rebase conflicts
When lifting and lowering for component host imports there won't be a
`Func` available to represent the options and such for the lowering.
That means that the current construction of the `ComponentValue` trait
won't be sufficient for host imports. This commit instead refactors the
traits to instead work with an `Options` type where the `Options` type
can be manufactured from thin air out of the arguments passed to the
component host trampolines.
This new `Options` type is also suitable for storing in `WasmStr` and
`WasmList` to continue to be used to refer back to memory after
these lifted values have been given back to the embedder.
Overall this should largely just be shuffling code around and renaming
`func: &Func` to `options: &Options`.
* Add trampoline compilation support for lowered imports
This commit adds support to the component model implementation for
compiling trampolines suitable for calling host imports. Currently this
is purely just the compilation side of things, modifying the
wasmtime-cranelift crate and additionally filling out a new
`VMComponentOffsets` type (similar to `VMOffsets`). The actual creation
of a `VMComponentContext` is still not performed and will be a
subsequent PR.
Internally though some tests are actually possible with this where we at
least assert that compilation of a component and creation of everything
in-memory doesn't panic or trip any assertions, so some tests are added
here for that as well.
* Fix some test errors
* Implement module imports into components
As a step towards implementing function imports into a component this
commit implements importing modules into a component. This fills out
missing pieces of functionality such as exporting modules as well. The
previous translation code had initial support for translating imported
modules but some of the AST type information was restructured with
feedback from this implementation, namely splitting the
`InstantiateModule` initializer into separate upvar/import variants to
clarify that the item orderings for imports are resolved differently at
runtime.
Much of this commit is also adding infrastructure for any imports at all
into a component. For example a `Linker` type (analagous to
`wasmtime::Linker`) was added here as well. For now this type is quite
limited due to the inability to define host functions (it can only work
with instances and instances-of-modules) but it's enough to start
writing `*.wast` tests which exercise lots of module-related functionality.
* Fix a warning
This commit enhances the processing of components to track all the
dataflow for the processing of `canon.lower`'d functions. At the same
time this fills out a few other missing details to component processing
such as aliasing from some kinds of component instances and similar.
The major changes contained within this are the updates the `info`
submodule which has the AST of component type information. This has been
significantly refactored to prepare for representing lowered functions
and implementing those. The major change is from an `Instantiation` list
to an `Initializer` list which abstractly represents a few other
initialization actions.
This work is split off from my main work to implement component imports
of host functions. This is incomplete in the sense that it doesn't
actually finish everything necessary to define host functions and import
them into components. Instead this is only the changes necessary at the
translation layer (so far). Consequently this commit does not have tests
and also namely doesn't actually include the `VMComponentContext`
initialization and usage. The full body of work is still a bit too messy
to PR just yet so I'm hoping that this is a slimmed-down-enough piece to
adequately be reviewed.
Prior to this PR a major feature of calling component exports (#4039)
was the usage of the `Value<T>` type. This type represents a value
stored in wasm linear memory (the type `T` stored there). This
implementation had a number of drawbacks though:
* When returning a value it's ABI-specific whether you use `T` or
`Value<T>` as a return value. If `T` is represented with one wasm
primitive then you have to return `T`, otherwise the return value must
be `Value<T>`. This is somewhat non-obvious and leaks ABI-details into
the API which is unfortunate.
* The `T` in `Value<T>` was somewhat non-obvious. For example a
wasm-owned string was `Value<String>`. Using `Value<&str>` didn't
work.
* Working with `Value<T>` was unergonomic in the sense that you had to
first "pair" it with a `&Store<U>` to get a `Cursor<T>` and then you
could start reading the value.
* Custom structs and enums, while not implemented yet, were planned to
be quite wonky where when you had `Cursor<MyStruct>` then you would
have to import a `CursorMyStructExt` trait generated by a proc-macro
(think a `#[derive]` on the definition of `MyStruct`) which would
enable field accessors, returning cursors of all the fields.
* In general there was no "generic way" to load a `T` from memory. Other
operations like lift/lower/store all had methods in the
`ComponentValue` trait but load had no equivalent.
None of these drawbacks were deal-breakers per-se. When I started
to implement imported functions, though, the `Value<T>` type no longer
worked. The major difference between imports and exports is that when
receiving values from wasm an export returns at most one wasm primitive
where an import can yield (through arguments) up to 16 wasm primitives.
This means that if an export returned a string it would always be
`Value<String>` but if an import took a string as an argument there was
actually no way to represent this with `Value<String>` since the value
wasn't actually stored in memory but rather the pointer/length pair is
received as arguments. Overall this meant that `Value<T>` couldn't be
used for arguments-to-imports, which means that altogether something new
would be required.
This PR completely removes the `Value<T>` and `Cursor<T>` type in favor
of a different implementation. The inspiration from this comes from the
fact that all primitives can be both lifted and lowered into wasm while
it's just some times which can only go one direction. For example
`String` can be lowered into wasm but can't be lifted from wasm. Instead
some sort of "view" into wasm needs to be created during lifting.
One of the realizations from #4039 was that we could leverage
run-time-type-checking to reject static constructions that don't make
sense. For example if an embedder asserts that a wasm function returns a
Rust `String` we can reject that at typechecking time because it's
impossible for a wasm module to ever do that.
The new system of imports/exports in this PR now looks like:
* Type-checking takes into accont an `Op` operation which indicates
whether we'll be lifting or lowering the type. This means that we can
allow the lowering operation for `String` but disallow the lifting
operation. While we can't statically rule out an embedder saying that
a component returns a `String` we can now reject it at runtime and
disallow it from being called.
* The `ComponentValue` trait now sports a new `load` function. This
function will load and instance of `Self` from the byte-array
provided. This is implemented for all types but only ever actually
executed when the `lift` operation is allowed during type-checking.
* The `Lift` associated type is removed since it's now expected that the
lift operation returns `Self`.
* The `ComponentReturn` trait is now no longer necessary and is removed.
Instead returns are bounded by `ComponentValue`. During type-checking
it's required that the return value can be lifted, disallowing, for
example, returning a `String` or `&str`.
* With `Value` gone there's no need to specify the ABI details of the
return value, or whether it's communicated through memory or not. This
means that handling return values through memory is transparently
handled by Wasmtime.
* Validation is in a sense more eagerly performed now. Whenever a value
`T` is loaded the entire immediate structure of `T` is loaded and
validated. Note that recursive through memory validation still does
not happen, so the contents of lists or strings aren't validated, it's
just validated that the pointers are in-bounds.
Overall this felt like a much clearer system to work with and should be
much easier to integrate with imported functions as well. The new
`WasmStr` and `WasmList<T>` types can be used in import arguments and
lifted from the immediate arguments provided rather than forcing them to
always be stored in memory.
* Add a first-class `StoreId` type to Wasmtime
This commit adds a `StoreId` type to uniquely identify a store
internally within Wasmtime. This hasn't been created previously as it
was never really needed but I've run across a case for its usage in the
component model so I've gone ahead and split out a commit to add this type.
While I was here in this file I opted to improve some other
miscellaneous things as well:
* Notes were added to the `Index` impls that unchecked indexing could be
used in theory if we ever need it one day.
* The check in `Index` for the same store should now be a bit lighter on
codegen where instead of having a `panic!()` in the codegen for each
`Index` there's now an out-of-line version which is `#[cold]`. This
should improve codegen as calling a function with no arguments is
slighly more efficient than calling the panic macro with one string argument.
* An `assert!` guarded with a `cfg(debug_assertions)` was changed to a
`debug_assert!`.
* Allocation of a `StoreId` was refactored to a method on the `StoreId`
itself.
* Review comments
* Fix an ordering
* Change some `VMContext` pointers to `()` pointers
This commit is motivated by my work on the component model
implementation for imported functions. Currently all context pointers in
wasm are `*mut VMContext` but with the component model my plan is to
make some pointers instead along the lines of `*mut VMComponentContext`.
In doing this though one worry I have is breaking what has otherwise
been a core invariant of Wasmtime for quite some time, subtly
introducing bugs by accident.
To help assuage my worry I've opted here to erase knowledge of
`*mut VMContext` where possible. Instead where applicable a context
pointer is simply known as `*mut ()` and the embedder doesn't actually
know anything about this context beyond the value of the pointer. This
will help prevent Wasmtime from accidentally ever trying to interpret
this context pointer as an actual `VMContext` when it might instead be a
`VMComponentContext`.
Overall this was a pretty smooth transition. The main change here is
that the `VMTrampoline` (now sporting more docs) has its first argument
changed to `*mut ()`. The second argument, the caller context, is still
configured as `*mut VMContext` though because all functions are always
called from wasm still. Eventually for component-to-component calls I
think we'll probably "fake" the second argument as the same as the first
argument, losing track of the original caller, as an intentional way of
isolating components from each other.
Along the way there are a few host locations which do actually assume
that the first argument is indeed a `VMContext`. These are valid
assumptions that are upheld from a correct implementation, but I opted
to add a "magic" field to `VMContext` to assert this in debug mode. This
new "magic" field is inintialized during normal vmcontext initialization
and it's checked whenever a `VMContext` is reinterpreted as an
`Instance` (but only in debug mode). My hope here is to catch any future
accidental mistakes, if ever.
* Use a VMOpaqueContext wrapper
* Fix typos
