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121 lines
4.1 KiB
Rust
121 lines
4.1 KiB
Rust
// This file contains code from external sources.
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// Attributions: https://github.com/wasmerio/wasmer/blob/master/ATTRIBUTIONS.md
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//! A trampoline generator for calling dynamic host functions from Wasm.
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use crate::translator::{compiled_function_unwind_info, signature_to_cranelift_ir};
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use cranelift_codegen::ir;
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use cranelift_codegen::ir::{
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ExternalName, Function, InstBuilder, MemFlags, StackSlotData, StackSlotKind,
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};
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use cranelift_codegen::isa::TargetIsa;
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use cranelift_codegen::print_errors::pretty_error;
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use cranelift_codegen::Context;
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use std::cmp;
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use std::mem;
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use cranelift_frontend::{FunctionBuilder, FunctionBuilderContext};
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use wasmer_compiler::{CompileError, FunctionBody};
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use wasmer_types::FunctionType;
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use wasmer_vm::VMOffsets;
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/// Create a trampoline for invoking a WebAssembly function.
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pub fn make_trampoline_dynamic_function(
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isa: &dyn TargetIsa,
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offsets: &VMOffsets,
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fn_builder_ctx: &mut FunctionBuilderContext,
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func_type: &FunctionType,
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) -> Result<FunctionBody, CompileError> {
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let pointer_type = isa.pointer_type();
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let frontend_config = isa.frontend_config();
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let signature = signature_to_cranelift_ir(func_type, frontend_config);
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let mut stub_sig = ir::Signature::new(frontend_config.default_call_conv);
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// Add the caller `vmctx` parameter.
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stub_sig.params.push(ir::AbiParam::special(
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pointer_type,
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ir::ArgumentPurpose::VMContext,
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));
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// Add the `values_vec` parameter.
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stub_sig.params.push(ir::AbiParam::new(pointer_type));
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// Compute the size of the values vector. The vmctx and caller vmctx are passed separately.
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let value_size = mem::size_of::<u128>();
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let values_vec_len =
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(value_size * cmp::max(signature.params.len() - 1, signature.returns.len())) as u32;
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let mut context = Context::new();
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context.func = Function::with_name_signature(ExternalName::user(0, 0), signature.clone());
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let ss = context.func.create_stack_slot(StackSlotData::new(
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StackSlotKind::ExplicitSlot,
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values_vec_len,
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));
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{
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let mut builder = FunctionBuilder::new(&mut context.func, fn_builder_ctx);
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let block0 = builder.create_block();
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builder.append_block_params_for_function_params(block0);
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builder.switch_to_block(block0);
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builder.seal_block(block0);
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let values_vec_ptr_val = builder.ins().stack_addr(pointer_type, ss, 0);
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let mflags = MemFlags::trusted();
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// We only get the non-vmctx arguments
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for i in 1..signature.params.len() {
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let val = builder.func.dfg.block_params(block0)[i];
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builder.ins().store(
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mflags,
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val,
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values_vec_ptr_val,
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((i - 1) * value_size) as i32,
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);
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}
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let block_params = builder.func.dfg.block_params(block0);
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let vmctx_ptr_val = block_params[0];
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let callee_args = vec![vmctx_ptr_val, values_vec_ptr_val];
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let new_sig = builder.import_signature(stub_sig);
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let mem_flags = ir::MemFlags::trusted();
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let callee_value = builder.ins().load(
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pointer_type,
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mem_flags,
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vmctx_ptr_val,
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offsets.vmdynamicfunction_import_context_address() as i32,
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);
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builder
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.ins()
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.call_indirect(new_sig, callee_value, &callee_args);
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let mflags = MemFlags::trusted();
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let mut results = Vec::new();
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for (i, r) in signature.returns.iter().enumerate() {
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let load = builder.ins().load(
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r.value_type,
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mflags,
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values_vec_ptr_val,
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(i * value_size) as i32,
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);
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results.push(load);
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}
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builder.ins().return_(&results);
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builder.finalize()
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}
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let mut code_buf = Vec::new();
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context
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.compile_and_emit(isa, &mut code_buf)
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.map_err(|error| CompileError::Codegen(pretty_error(&context.func, error)))?;
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let unwind_info = compiled_function_unwind_info(isa, &context)?.maybe_into_to_windows_unwind();
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Ok(FunctionBody {
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body: code_buf,
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unwind_info,
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})
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}
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