* add a lifetime to the wiggle_runtime::GuestErrorType trait, wiggle_tests::WasiCtx struct
* wiggle-generate: make config parsing public so it can be reused in lucet
* wiggle-runtime: add as_raw method for [T]
* add trivial borrow checker back in
* integrate runtime borrow checker with as_raw methods
* handle pointer arith overflow correctly in as_raw, create PtrOverflow error
* runtime: add validation back to GuestType
* generate: impl validate for enums, flags, handles, ints
* oops! make validate its own method on trait GuestTypeTransparent
* fix transparent impls for enum, flag, handle, int
* some structs are transparent. fix tests.
* tests: define byte_slice_strat and friends
* wiggle-tests: i believe my allocator is working now
* some type juggling around memset for ease of use
* make GuestTypeTransparent an unsafe trait
* delete redundant validation of pointer align
* fix doc
* wiggle_test: aha, you cant use sets to track memory areas
* add multi-string test
which exercises the runtime borrow checker against
HostMemory::byte_slice_strat
* oops left debug panic in
* remove redundant (& incorrect, since unchecked) length calc
* redesign validate again, and actually hook to as_raw
* makr all validate impls as inline
this should hopefully allow as_raw's check loop to be unrolled to a
no-op in most cases!
* code review fixes
This commit rewrites the runtime crate to provide safety in the face
of recursive calls to the guest. The basic principle is that
`GuestMemory` is now a trait which dynamically returns the
pointer/length pair. This also has an implicit contract (hence the
`unsafe` trait) that the pointer/length pair point to a valid list of
bytes in host memory "until something is reentrant".
After this changes the various suite of `Guest*` types were rewritten.
`GuestRef` and `GuestRefMut` were both removed since they cannot safely
exist. The `GuestPtrMut` type was removed for simplicity, and the final
`GuestPtr` type subsumes `GuestString` and `GuestArray`. This means
that there's only one guest pointer type, `GuestPtr<'a, T>`, where `'a`
is the borrow into host memory, basically borrowing the `GuestMemory`
trait object itself.
Some core utilities are exposed on `GuestPtr`, but they're all 100%
safe. Unsafety is now entirely contained within a few small locations:
* Implementations of the `GuestType` for primitive types (e.g. `i8`,
`u8`, etc) use `unsafe` to read/write memory. The `unsafe` trait of
`GuestMemory` though should prove that they're safe.
* `GuestPtr<'_, str>` has a method which validates utf-8 contents, and
this requires `unsafe` internally to read all the bytes. This is
guaranteed to be safe however given the contract of `GuestMemory`.
And that's it! Everything else is a bunch of safe combinators all built
up on the various utilities provided by `GuestPtr`. The general idioms
are roughly the same as before, with various tweaks here and there. A
summary of expected idioms are:
* For small values you'd `.read()` or `.write()` very quickly. You'd
pass around the type itself.
* For strings, you'd pass `GuestPtr<'_, str>` down to the point where
it's actually consumed. At that moment you'd either decide to copy it
out (a safe operation) or you'd get a raw view to the string (an
unsafe operation) and assert that you won't call back into wasm while
you're holding that pointer.
* Arrays are similar to strings, passing around `GuestPtr<'_, [T]>`.
Arrays also have a `iter()` method which yields an iterator of
`GuestPtr<'_, T>` for convenience.
Overall there's still a lot of missing documentation on the runtime
crate specifically around the safety of the `GuestMemory` trait as well
as how the utilities/methods are expected to be used. Additionally
there's utilities which aren't currently implemented which would be easy
to implement. For example there's no method to copy out a string or a
slice, although that would be pretty easy to add.
In any case I'm curious to get feedback on this approach and see what
y'all think!
This commit puts context object, i.e., the implementor of the
WASI snapshot, behind a reference `&self` rather than a mutable
reference `&mut self`. As suggested by @alexcrichton, this gives
the implementor the possibility to determine how it handles its
interior mutability.
this allows us to reuse the code in wiggle-generate elsewhere, because
a proc-macro=true lib can only export a #[proc_macro] and not ordinary
functions.
In lucet, I will depend on wiggle-generate to define a proc macro that
glues wiggle to the specifics of the runtime.
This commit refactors trait system for guest types. Namely, as
discussed offline on zulip, `GuestType` now includes `GuestTypeClone`,
whereas `GuestTypeCopy` has been renamed to `GuestTypeTransparent`.
these names were artifacts of some early confusion / bad design i made
in the traits. read and write are much simpler names!
also, change a ptr_mut to ptr where we just read the contents in the
argument marshalling for structs. this has no effect, but it is more
correct.
* atoms in one test unit
* factor out pointers test
* factor structs into separate test unit
* factor out arrays, flags
* finally, separate into strings and ints
