the Rc<RefCell<ctx>> wrapping inside the wasmtime-generated bindings
was eliminated, and instead the caller of ::new(linker, ctx) is
required to wrap the ctx in Rc<RefCell<>>.
The Rc wrapping inside WasiCryptoCtx can be eliminated due to this
change.
the original C implementation was derived directly from cloudabi-utils.
that implementation is no longer in tree.
acfoltzer's initial Rust implementation included a path_open function
that was ported from cloudabi-utils. this rewrite of wasi-common has
completely delegated all path lookup functionality to cap-std (in the
cap-std-sync impls), and cap-std itself has a completely re-designed
method of path resolution.
* Consume fuel during function execution
This commit adds codegen infrastructure necessary to instrument wasm
code to consume fuel as it executes. Currently nothing is really done
with the fuel, but that'll come in later commits.
The focus of this commit is to implement the codegen infrastructure
necessary to consume fuel and account for fuel consumed correctly.
* Periodically check remaining fuel in wasm JIT code
This commit enables wasm code to periodically check to see if fuel has
run out. When fuel runs out an intrinsic is called which can do what it
needs to do in the result of fuel running out. For now a trap is thrown
to have at least some semantics in synchronous stores, but another
planned use for this feature is for asynchronous stores to periodically
yield back to the host based on fuel running out.
Checks for remaining fuel happen in the same locations as interrupt
checks, which is to say the start of the function as well as loop
headers.
* Improve codegen by caching `*const VMInterrupts`
The location of the shared interrupt value and fuel value is through a
double-indirection on the vmctx (load through the vmctx and then load
through that pointer). The second pointer in this chain, however, never
changes, so we can alter codegen to account for this and remove some
extraneous load instructions and hopefully reduce some register
pressure even maybe.
* Add tests fuel can abort infinite loops
* More fuzzing with fuel
Use fuel to time out modules in addition to time, using fuzz input to
figure out which.
* Update docs on trapping instructions
* Fix doc links
* Fix a fuzz test
* Change setting fuel to adding fuel
* Fix a doc link
* Squelch some rustdoc warnings
1. Restricts max nop size to 15 instead of 16.
2. Fixes an edge case where gen_nop() would return a zero sized intruction on multiples of 16.
3. Clarifies the documentation of the gen_nop interface to state that returning zero is allowed when preferred_size is zero.
Fuzzing has turned up that module linking can create large amounts of
tables and memories in addition to instances. For example if N instances
are allowed and M tables are allowed per-instance, then currently
wasmtime allows MxN tables (which is quite a lot). This is causing some
wasm-smith-generated modules to exceed resource limits while fuzzing!
This commits adds corresponding `max_tables` and `max_memories`
functions to sit alongside the `max_instances` configuration.
Additionally fuzzing now by default configures all of these to a
somewhat low value to avoid too much resource usage while fuzzing.
Pat Hickey
Nick Fitzgerald
Benjamin Bouvier
Alex Crichton
Chris Fallin
Amanieu d'Antras
Kasey Carrothers
Johnnie Birch