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Instantiate fewer instances when fuzzing (#2768)

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This commit fixes an issue where when module linking was enabled for
fuzzing (which it is) import types of modules show as imports of
instances. In an attempt to satisfy the dummy values of such imports the
fuzzing integration would create instances for each import. This would,
however, count towards instance limits and isn't always desired.

This commit refactors the creation of dummy import values to decompose
imports of instances into imports of each individual item. This should
retain the pre-module-linking behavior of dummy imports for various
fuzzers.
This commit is contained in:
Alex Crichton
2021-03-25 13:35:38 -05:00
committed by GitHub
parent 30d9164b6e
commit 9476581ae6
3 changed files with 78 additions and 40 deletions
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52
crates/fuzzing/src/oracles/dummy.rs
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@@ -4,22 +4,44 @@ use std::fmt::Write;
use wasmtime::*;
/// Create a set of dummy functions/globals/etc for the given imports.
pub fn dummy_imports<'module>(
store: &Store,
import_tys: impl Iterator<Item = ImportType<'module>>,
) -> Vec<Extern> {
import_tys
.map(|imp| match imp.ty() {
ExternType::Func(func_ty) => Extern::Func(dummy_func(&store, func_ty)),
ExternType::Global(global_ty) => Extern::Global(dummy_global(&store, global_ty)),
ExternType::Table(table_ty) => Extern::Table(dummy_table(&store, table_ty)),
ExternType::Memory(mem_ty) => Extern::Memory(dummy_memory(&store, mem_ty)),
ExternType::Instance(instance_ty) => {
Extern::Instance(dummy_instance(&store, instance_ty))
pub fn dummy_linker<'module>(store: &Store, module: &Module) -> Linker {
let mut linker = Linker::new(store);
for import in module.imports() {
match import.name() {
Some(name) => {
linker
.define(import.module(), name, dummy_extern(store, import.ty()))
.unwrap();
}
ExternType::Module(module_ty) => Extern::Module(dummy_module(&store, module_ty)),
})
.collect()
None => match import.ty() {
ExternType::Instance(ty) => {
for ty in ty.exports() {
linker
.define(import.module(), ty.name(), dummy_extern(store, ty.ty()))
.unwrap();
}
}
other => {
linker
.define_name(import.module(), dummy_extern(store, other))
.unwrap();
}
},
}
}
linker
}
/// Construct a dummy `Extern` from its type signature
pub fn dummy_extern(store: &Store, ty: ExternType) -> Extern {
match ty {
ExternType::Func(func_ty) => Extern::Func(dummy_func(store, func_ty)),
ExternType::Global(global_ty) => Extern::Global(dummy_global(store, global_ty)),
ExternType::Table(table_ty) => Extern::Table(dummy_table(store, table_ty)),
ExternType::Memory(mem_ty) => Extern::Memory(dummy_memory(store, mem_ty)),
ExternType::Instance(instance_ty) => Extern::Instance(dummy_instance(store, instance_ty)),
ExternType::Module(module_ty) => Extern::Module(dummy_module(store, module_ty)),
}
}
/// Construct a dummy function for the given function type