1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130

// This file contains code from external sources.
// Attributions: https://github.com/wasmerio/wasmer/blob/master/ATTRIBUTIONS.md

//! A trampoline generator for calling Wasm functions easily.
//!
//! That way, you can start calling Wasm functions doing things like:
//! ```ignore
//! let my_func = instance.exports.get("func");
//! my_func.call([1, 2])
//! ```
use super::binemit::TrampolineRelocSink;
use crate::translator::{
    compiled_function_unwind_info, signature_to_cranelift_ir, /*transform_jump_table, */
};
use cranelift_codegen::ir::InstBuilder;
use cranelift_codegen::isa::TargetIsa;
use cranelift_codegen::print_errors::pretty_error;
use cranelift_codegen::Context;
use cranelift_codegen::{binemit, ir};
use cranelift_frontend::{FunctionBuilder, FunctionBuilderContext};
use std::mem;
use wasmer_compiler::{CompileError, FunctionBody};
use wasmer_types::FunctionType;

/// Create a trampoline for invoking a WebAssembly function.
pub fn make_trampoline_function_call(
    isa: &dyn TargetIsa,
    fn_builder_ctx: &mut FunctionBuilderContext,
    func_type: &FunctionType,
) -> Result<FunctionBody, CompileError> {
    let pointer_type = isa.pointer_type();
    let frontend_config = isa.frontend_config();
    let signature = signature_to_cranelift_ir(func_type, frontend_config);
    let mut wrapper_sig = ir::Signature::new(frontend_config.default_call_conv);

    // Add the callee `vmctx` parameter.
    wrapper_sig.params.push(ir::AbiParam::special(
        pointer_type,
        ir::ArgumentPurpose::VMContext,
    ));

    // Add the `callee_address` parameter.
    wrapper_sig.params.push(ir::AbiParam::new(pointer_type));

    // Add the `values_vec` parameter.
    wrapper_sig.params.push(ir::AbiParam::new(pointer_type));

    let mut context = Context::new();
    context.func = ir::Function::with_name_signature(ir::ExternalName::user(0, 0), wrapper_sig);

    let value_size = mem::size_of::<u128>();
    {
        let mut builder = FunctionBuilder::new(&mut context.func, fn_builder_ctx);
        let block0 = builder.create_block();

        builder.append_block_params_for_function_params(block0);
        builder.switch_to_block(block0);
        builder.seal_block(block0);

        let (vmctx_ptr_val, callee_value, values_vec_ptr_val) = {
            let params = builder.func.dfg.block_params(block0);
            (params[0], params[1], params[2])
        };

        // Load the argument values out of `values_vec`.
        let mflags = ir::MemFlags::trusted();
        let callee_args = signature
            .params
            .iter()
            .enumerate()
            .map(|(i, r)| {
                match i {
                    0 => vmctx_ptr_val,
                    _ =>
                    // i - 1 because vmctx is not passed through `values_vec`.
                    {
                        builder.ins().load(
                            r.value_type,
                            mflags,
                            values_vec_ptr_val,
                            ((i - 1) * value_size) as i32,
                        )
                    }
                }
            })
            .collect::<Vec<_>>();

        let new_sig = builder.import_signature(signature);

        let call = builder
            .ins()
            .call_indirect(new_sig, callee_value, &callee_args);

        let results = builder.func.dfg.inst_results(call).to_vec();

        // Store the return values into `values_vec`.
        let mflags = ir::MemFlags::trusted();
        for (i, r) in results.iter().enumerate() {
            builder
                .ins()
                .store(mflags, *r, values_vec_ptr_val, (i * value_size) as i32);
        }

        builder.ins().return_(&[]);
        builder.finalize()
    }

    let mut code_buf = Vec::new();
    let mut reloc_sink = TrampolineRelocSink {};
    let mut trap_sink = binemit::NullTrapSink {};
    let mut stackmap_sink = binemit::NullStackMapSink {};

    context
        .compile_and_emit(
            isa,
            &mut code_buf,
            &mut reloc_sink,
            &mut trap_sink,
            &mut stackmap_sink,
        )
        .map_err(|error| CompileError::Codegen(pretty_error(&context.func, Some(isa), error)))?;

    let unwind_info = compiled_function_unwind_info(isa, &context)?.maybe_into_to_windows_unwind();

    Ok(FunctionBody {
        body: code_buf,
        unwind_info,
        // jt_offsets: transform_jump_table(context.func.jt_offsets),
    })
}