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Use a union for VMContext for functions

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This makes the code more self documenting and correctly uses `unsafe`
to communicate that it's the user's responsibility to ensure that the
code paths that can lead to the access can only write the value they
expect to be there.
This commit is contained in:
Mark McCaskey
2020-10-22 11:46:42 -07:00
parent 36a713a649
commit b124ea2032
10 changed files with 105 additions and 50 deletions
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20
lib/api/src/native.rs
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@@ -17,7 +17,7 @@ use crate::{FromToNativeWasmType, Function, FunctionType, RuntimeError, Store, W
use std::panic::{catch_unwind, AssertUnwindSafe};
use wasmer_types::NativeWasmType;
use wasmer_vm::{
ExportFunction, VMContext, VMDynamicFunctionContext, VMFunctionBody, VMFunctionKind,
ExportFunction, VMDynamicFunctionContext, VMFunctionBody, VMFunctionExtraData, VMFunctionKind,
};
/// A WebAssembly function that can be called natively
@@ -26,7 +26,7 @@ pub struct NativeFunc<'a, Args = (), Rets = ()> {
definition: FunctionDefinition,
store: Store,
address: *const VMFunctionBody,
vmctx: *mut VMContext,
vmctx: VMFunctionExtraData,
arg_kind: VMFunctionKind,
// exported: ExportFunction,
_phantom: PhantomData<(&'a (), Args, Rets)>,
@@ -42,7 +42,7 @@ where
pub(crate) fn new(
store: Store,
address: *const VMFunctionBody,
vmctx: *mut VMContext,
vmctx: VMFunctionExtraData,
arg_kind: VMFunctionKind,
definition: FunctionDefinition,
) -> Self {
@@ -165,7 +165,7 @@ macro_rules! impl_native_traits {
match self.arg_kind {
VMFunctionKind::Static => {
let results = catch_unwind(AssertUnwindSafe(|| unsafe {
let f = std::mem::transmute::<_, unsafe extern "C" fn( *mut VMContext, $( $x, )*) -> Rets::CStruct>(self.address);
let f = std::mem::transmute::<_, unsafe extern "C" fn( VMFunctionExtraData, $( $x, )*) -> Rets::CStruct>(self.address);
// We always pass the vmctx
f( self.vmctx, $( $x, )* )
})).map_err(|e| RuntimeError::new(format!("{:?}", e)))?;
@@ -175,12 +175,16 @@ macro_rules! impl_native_traits {
let params_list = [ $( $x.to_native().to_value() ),* ];
let results = if !has_env {
type VMContextWithoutEnv = VMDynamicFunctionContext<VMDynamicFunctionWithoutEnv>;
let ctx = self.vmctx as *mut VMContextWithoutEnv;
unsafe { (*ctx).ctx.call(&params_list)? }
unsafe {
let ctx = self.vmctx.host_env as *mut VMContextWithoutEnv;
(*ctx).ctx.call(&params_list)?
}
} else {
type VMContextWithEnv = VMDynamicFunctionContext<VMDynamicFunctionWithEnv<std::ffi::c_void>>;
let ctx = self.vmctx as *mut VMContextWithEnv;
unsafe { (*ctx).ctx.call(&params_list)? }
unsafe {
let ctx = self.vmctx.host_env as *mut VMContextWithEnv;
(*ctx).ctx.call(&params_list)?
}
};
let mut rets_list_array = Rets::empty_array();
let mut_rets = rets_list_array.as_mut() as *mut [i128] as *mut i128;