wasmer_compiler_cranelift/trampoline/
dynamic_function.rs

1// This file contains code from external sources.
2// Attributions: https://github.com/wasmerio/wasmer/blob/main/docs/ATTRIBUTIONS.md
3
4//! A trampoline generator for calling dynamic host functions from Wasm.
5
6use crate::translator::{compiled_function_unwind_info, signature_to_cranelift_ir};
7use cranelift_codegen::{
8    Context,
9    ir::{self, Function, InstBuilder, MemFlags, StackSlotData, StackSlotKind, UserFuncName},
10    isa::TargetIsa,
11};
12use cranelift_frontend::{FunctionBuilder, FunctionBuilderContext};
13use std::{cmp, mem};
14use wasmer_compiler::types::function::FunctionBody;
15use wasmer_types::{CompileError, FunctionType, VMOffsets};
16
17/// Create a trampoline for invoking a WebAssembly function.
18pub fn make_trampoline_dynamic_function(
19    isa: &dyn TargetIsa,
20    offsets: &VMOffsets,
21    fn_builder_ctx: &mut FunctionBuilderContext,
22    func_type: &FunctionType,
23) -> Result<FunctionBody, CompileError> {
24    let pointer_type = isa.pointer_type();
25    let frontend_config = isa.frontend_config();
26    let signature = signature_to_cranelift_ir(func_type, frontend_config);
27    let mut stub_sig = ir::Signature::new(frontend_config.default_call_conv);
28    // Add the caller `vmctx` parameter.
29    stub_sig.params.push(ir::AbiParam::special(
30        pointer_type,
31        ir::ArgumentPurpose::VMContext,
32    ));
33
34    // Add the `values_vec` parameter.
35    stub_sig.params.push(ir::AbiParam::new(pointer_type));
36
37    // Compute the size of the values vector. The vmctx and caller vmctx are passed separately.
38    let value_size = mem::size_of::<u128>();
39    let values_vec_len =
40        (value_size * cmp::max(signature.params.len() - 1, signature.returns.len())) as u32;
41
42    let mut context = Context::new();
43    context.func = Function::with_name_signature(UserFuncName::user(0, 0), signature.clone());
44
45    let ss = context.func.create_sized_stack_slot(StackSlotData::new(
46        StackSlotKind::ExplicitSlot,
47        values_vec_len,
48        0,
49    ));
50
51    {
52        let mut builder = FunctionBuilder::new(&mut context.func, fn_builder_ctx);
53        let block0 = builder.create_block();
54
55        builder.append_block_params_for_function_params(block0);
56        builder.switch_to_block(block0);
57        builder.seal_block(block0);
58
59        let values_vec_ptr_val = builder.ins().stack_addr(pointer_type, ss, 0);
60        let mflags = MemFlags::trusted();
61        // We only get the non-vmctx arguments
62        for i in 1..signature.params.len() {
63            let val = builder.func.dfg.block_params(block0)[i];
64            builder.ins().store(
65                mflags,
66                val,
67                values_vec_ptr_val,
68                ((i - 1) * value_size) as i32,
69            );
70        }
71
72        let block_params = builder.func.dfg.block_params(block0);
73        let vmctx_ptr_val = block_params[0];
74        let callee_args = vec![vmctx_ptr_val, values_vec_ptr_val];
75
76        let new_sig = builder.import_signature(stub_sig);
77
78        let mem_flags = ir::MemFlags::trusted();
79        let callee_value = builder.ins().load(
80            pointer_type,
81            mem_flags,
82            vmctx_ptr_val,
83            offsets.vmdynamicfunction_import_context_address() as i32,
84        );
85
86        builder
87            .ins()
88            .call_indirect(new_sig, callee_value, &callee_args);
89
90        let mflags = MemFlags::trusted();
91        let mut results = Vec::new();
92        for (i, r) in signature.returns.iter().enumerate() {
93            let load = builder.ins().load(
94                r.value_type,
95                mflags,
96                values_vec_ptr_val,
97                (i * value_size) as i32,
98            );
99            results.push(load);
100        }
101        builder.ins().return_(&results);
102        builder.finalize()
103    }
104
105    let mut code_buf = Vec::new();
106    let mut ctrl_plane = Default::default();
107    let compiled = context
108        .compile(isa, &mut ctrl_plane)
109        .map_err(|error| CompileError::Codegen(error.inner.to_string()))?;
110    code_buf.extend_from_slice(compiled.code_buffer());
111
112    let unwind_info = compiled_function_unwind_info(isa, &context)?.maybe_into_to_windows_unwind();
113
114    Ok(FunctionBody {
115        body: code_buf,
116        unwind_info,
117    })
118}
wasmer_compiler_cranelift/trampoline/dynamic_function.rs

wasmer_compiler_cranelift/trampoline/
dynamic_function.rs
