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main.go
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main.go
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// Copyright (c) 2018 Timo Savola. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Program wasys implements a standalone toy compiler and runtime.
package main
import (
"bytes"
"flag"
"fmt"
"io/ioutil"
"log"
"os"
"reflect"
"syscall"
"unsafe"
"github.com/tsavola/wag"
"github.com/tsavola/wag/buffer"
"github.com/tsavola/wag/object/debug/dump"
"github.com/tsavola/wag/wa"
)
const signalStackReserve = 8192
var (
verbose = false
)
type importFunc struct {
index int
params int
}
var (
importFuncs = make(map[string]importFunc)
importVector []byte
)
type resolver struct{}
func (resolver) ResolveFunc(module, field string, sig wa.FuncType) (index int, err error) {
if verbose {
log.Printf("import %s%s", field, sig)
}
if module != "env" {
err = fmt.Errorf("import function's module is unknown: %s %s", module, field)
return
}
i := importFuncs[field]
if i.index == 0 {
err = fmt.Errorf("import function not supported: %s", field)
return
}
if len(sig.Params) != i.params {
err = fmt.Errorf("%s: import function has wrong number of parameters: import signature has %d, syscall wrapper has %d", field, len(sig.Params), i.params)
return
}
index = i.index
return
}
func (resolver) ResolveGlobal(module, field string, t wa.Type) (init uint64, err error) {
err = fmt.Errorf("imported global not supported: %s %s", module, field)
return
}
func makeMem(size int, extraFlags int) (mem []byte, err error) {
if size > 0 {
mem, err = syscall.Mmap(-1, 0, size, syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_PRIVATE|syscall.MAP_ANONYMOUS|extraFlags)
}
return
}
func memAddr(mem []byte) uintptr {
return (*reflect.SliceHeader)(unsafe.Pointer(&mem)).Data
}
func alignSize(size, alignment int) int {
return (size + (alignment - 1)) &^ (alignment - 1)
}
func main() {
log.SetFlags(0)
flag.Usage = func() {
fmt.Fprintf(flag.CommandLine.Output(), "Usage: %s [options] wasmfile\n\n", os.Args[0])
fmt.Fprintf(flag.CommandLine.Output(), "Options:\n")
flag.PrintDefaults()
}
var (
textSize = 128 * 1024 * 1024
stackSize = 64 * 1024
entry = "main"
dumpText = false
)
flag.BoolVar(&verbose, "v", verbose, "verbose logging")
flag.IntVar(&textSize, "textsize", textSize, "maximum program text size")
flag.IntVar(&stackSize, "stacksize", stackSize, "call stack size")
flag.StringVar(&entry, "entry", entry, "function to run")
flag.BoolVar(&dumpText, "dumptext", dumpText, "disassemble the generated code to stdout")
flag.Parse()
if flag.NArg() != 1 {
flag.Usage()
os.Exit(2)
}
filename := flag.Arg(0)
prog, err := ioutil.ReadFile(filename)
if err != nil {
log.Fatal(err)
}
progReader := bytes.NewReader(prog)
vecSize := alignSize(len(importVector), os.Getpagesize())
vecTextMem, err := makeMem(vecSize+textSize, 0)
if err != nil {
log.Fatal(err)
}
vecMem := vecTextMem[:vecSize]
copy(vecMem[vecSize-len(importVector):], importVector)
textMem := vecTextMem[vecSize:]
textAddr := memAddr(textMem)
textBuf := buffer.NewStatic(textMem)
config := &wag.Config{
Text: textBuf,
MemoryAlignment: os.Getpagesize(),
Entry: entry,
}
obj, err := wag.Compile(config, progReader, resolver{})
if dumpText {
e := dump.Text(os.Stdout, obj.Text, textAddr, obj, &obj.Names)
if err == nil {
err = e
}
}
if err != nil {
log.Fatal(err)
}
memoryAddr := memAddr(obj.GlobalsMemory) + uintptr(obj.MemoryOffset)
initMemoryEnd := memoryAddr + uintptr(obj.InitialMemorySize)
growMemoryEnd := memoryAddr + uintptr(obj.MemorySizeLimit)
if err := syscall.Mprotect(vecMem, syscall.PROT_READ); err != nil {
log.Fatal(err)
}
if err := syscall.Mprotect(textMem, syscall.PROT_READ|syscall.PROT_EXEC); err != nil {
log.Fatal(err)
}
stackMem, err := makeMem(stackSize, syscall.MAP_STACK)
if err != nil {
log.Fatal(err)
}
stackOffset := stackSize - len(obj.StackFrame)
copy(stackMem[stackOffset:], obj.StackFrame)
stackAddr := memAddr(stackMem)
stackLimit := stackAddr + signalStackReserve
stackPtr := stackAddr + uintptr(stackOffset)
if stackLimit >= stackPtr {
log.Fatal("stack is too small for starting program")
}
exec(textAddr, stackLimit, memoryAddr, initMemoryEnd, growMemoryEnd, stackPtr)
}