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::{
7    CraneliftCallbacks,
8    translator::{compiled_function_unwind_info, signature_to_cranelift_ir},
9};
10use cranelift_codegen::{
11    Context,
12    ir::{self, Function, InstBuilder, MemFlags, StackSlotData, StackSlotKind, UserFuncName},
13    isa::TargetIsa,
14};
15use cranelift_frontend::{FunctionBuilder, FunctionBuilderContext};
16use std::{cmp, mem};
17use target_lexicon::Architecture;
18use wasmer_compiler::{misc::CompiledKind, types::function::FunctionBody};
19use wasmer_types::{CompileError, FunctionType, VMOffsets};
20
21/// Create a trampoline for invoking a WebAssembly function.
22pub fn make_trampoline_dynamic_function(
23    callbacks: &Option<CraneliftCallbacks>,
24    isa: &dyn TargetIsa,
25    arch: Architecture,
26    offsets: &VMOffsets,
27    fn_builder_ctx: &mut FunctionBuilderContext,
28    func_type: &FunctionType,
29    module_hash: &Option<String>,
30) -> Result<FunctionBody, CompileError> {
31    let pointer_type = isa.pointer_type();
32    let frontend_config = isa.frontend_config();
33    let signature = signature_to_cranelift_ir(func_type, frontend_config);
34    let mut stub_sig = ir::Signature::new(frontend_config.default_call_conv);
35    // Add the caller `vmctx` parameter.
36    stub_sig.params.push(ir::AbiParam::special(
37        pointer_type,
38        ir::ArgumentPurpose::VMContext,
39    ));
40
41    // Add the `values_vec` parameter.
42    stub_sig.params.push(ir::AbiParam::new(pointer_type));
43
44    // Compute the size of the values vector. The vmctx and caller vmctx are passed separately.
45    let value_size = mem::size_of::<u128>();
46    let values_vec_len =
47        (value_size * cmp::max(signature.params.len() - 1, signature.returns.len())) as u32;
48
49    let mut context = Context::new();
50    context.func = Function::with_name_signature(UserFuncName::user(0, 0), signature.clone());
51
52    let ss = context.func.create_sized_stack_slot(StackSlotData::new(
53        StackSlotKind::ExplicitSlot,
54        values_vec_len,
55        0,
56    ));
57
58    {
59        let mut builder = FunctionBuilder::new(&mut context.func, fn_builder_ctx);
60        let block0 = builder.create_block();
61
62        builder.append_block_params_for_function_params(block0);
63        builder.switch_to_block(block0);
64        builder.seal_block(block0);
65
66        let values_vec_ptr_val = builder.ins().stack_addr(pointer_type, ss, 0);
67        let mflags = MemFlags::trusted();
68        // We only get the non-vmctx arguments
69        for i in 1..signature.params.len() {
70            let val = builder.func.dfg.block_params(block0)[i];
71            builder.ins().store(
72                mflags,
73                val,
74                values_vec_ptr_val,
75                ((i - 1) * value_size) as i32,
76            );
77        }
78
79        let block_params = builder.func.dfg.block_params(block0);
80        let vmctx_ptr_val = block_params[0];
81        let callee_args = vec![vmctx_ptr_val, values_vec_ptr_val];
82
83        let new_sig = builder.import_signature(stub_sig);
84
85        let mem_flags = ir::MemFlags::trusted();
86        let callee_value = builder.ins().load(
87            pointer_type,
88            mem_flags,
89            vmctx_ptr_val,
90            offsets.vmdynamicfunction_import_context_address() as i32,
91        );
92
93        builder
94            .ins()
95            .call_indirect(new_sig, callee_value, &callee_args);
96
97        let mflags = MemFlags::trusted();
98        let mut results = Vec::new();
99        for (i, r) in signature.returns.iter().enumerate() {
100            let load = builder.ins().load(
101                r.value_type,
102                mflags,
103                values_vec_ptr_val,
104                (i * value_size) as i32,
105            );
106            results.push(load);
107        }
108        builder.ins().return_(&results);
109        builder.finalize()
110    }
111
112    if let Some(callbacks) = callbacks.as_ref() {
113        callbacks.preopt_ir(
114            &CompiledKind::DynamicFunctionTrampoline(func_type.clone()),
115            module_hash,
116            context.func.display().to_string().as_bytes(),
117        );
118    }
119
120    let mut code_buf = Vec::new();
121    let mut ctrl_plane = Default::default();
122    let compiled = context
123        .compile(isa, &mut ctrl_plane)
124        .map_err(|error| CompileError::Codegen(error.inner.to_string()))?;
125    code_buf.extend_from_slice(compiled.code_buffer());
126
127    if let Some(callbacks) = callbacks.as_ref() {
128        callbacks.obj_memory_buffer(
129            &CompiledKind::DynamicFunctionTrampoline(func_type.clone()),
130            module_hash,
131            &code_buf,
132        );
133        callbacks.asm_memory_buffer(
134            &CompiledKind::DynamicFunctionTrampoline(func_type.clone()),
135            module_hash,
136            arch,
137            &code_buf,
138        )?;
139    }
140
141    let unwind_info = compiled_function_unwind_info(isa, &context)?.maybe_into_to_windows_unwind();
142
143    Ok(FunctionBody {
144        body: code_buf,
145        unwind_info,
146    })
147}
wasmer_compiler_cranelift/trampoline/dynamic_function.rs

wasmer_compiler_cranelift/trampoline/
dynamic_function.rs
