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engine_cache.go
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/
engine_cache.go
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package compiler
import (
"bytes"
"encoding/binary"
"fmt"
"io"
"runtime"
"github.com/tetratelabs/wazero/experimental"
"github.com/tetratelabs/wazero/internal/platform"
"github.com/tetratelabs/wazero/internal/u32"
"github.com/tetratelabs/wazero/internal/u64"
"github.com/tetratelabs/wazero/internal/wasm"
)
func (e *engine) deleteCompiledModule(module *wasm.Module) {
e.mux.Lock()
defer e.mux.Unlock()
delete(e.codes, module.ID)
// Note: we do not call e.Cache.Delete, as the lifetime of
// the content is up to the implementation of extencache.Cache interface.
}
func (e *engine) addCompiledModule(module *wasm.Module, cm *compiledModule, withGoFunc bool) (err error) {
e.addCompiledModuleToMemory(module, cm)
if !withGoFunc {
err = e.addCompiledModuleToCache(module, cm)
}
return
}
func (e *engine) getCompiledModule(module *wasm.Module, listeners []experimental.FunctionListener) (cm *compiledModule, ok bool, err error) {
cm, ok = e.getCompiledModuleFromMemory(module)
if ok {
return
}
cm, ok, err = e.getCompiledModuleFromCache(module)
if ok {
e.addCompiledModuleToMemory(module, cm)
if len(listeners) > 0 {
// Files do not contain the actual listener instances (it's impossible to cache them as files!), so assign each here.
for i := range cm.functions {
cm.functions[i].listener = listeners[i]
}
}
}
return
}
func (e *engine) addCompiledModuleToMemory(module *wasm.Module, cm *compiledModule) {
e.mux.Lock()
defer e.mux.Unlock()
e.codes[module.ID] = cm
}
func (e *engine) getCompiledModuleFromMemory(module *wasm.Module) (cm *compiledModule, ok bool) {
e.mux.RLock()
defer e.mux.RUnlock()
cm, ok = e.codes[module.ID]
return
}
func (e *engine) addCompiledModuleToCache(module *wasm.Module, cm *compiledModule) (err error) {
if e.fileCache == nil || module.IsHostModule {
return
}
err = e.fileCache.Add(module.ID, serializeCompiledModule(e.wazeroVersion, cm))
return
}
func (e *engine) getCompiledModuleFromCache(module *wasm.Module) (cm *compiledModule, hit bool, err error) {
if e.fileCache == nil || module.IsHostModule {
return
}
// Check if the entries exist in the external cache.
var cached io.ReadCloser
cached, hit, err = e.fileCache.Get(module.ID)
if !hit || err != nil {
return
}
// Otherwise, we hit the cache on external cache.
// We retrieve *code structures from `cached`.
var staleCache bool
// Note: cached.Close is ensured to be called in deserializeCodes.
cm, staleCache, err = deserializeCompiledModule(e.wazeroVersion, cached, module)
if err != nil {
hit = false
return
} else if staleCache {
return nil, false, e.fileCache.Delete(module.ID)
}
cm.source = module
return
}
var wazeroMagic = "WAZERO" // version must be synced with the tag of the wazero library.
func serializeCompiledModule(wazeroVersion string, cm *compiledModule) io.Reader {
buf := bytes.NewBuffer(nil)
// First 6 byte: WAZERO header.
buf.WriteString(wazeroMagic)
// Next 1 byte: length of version:
buf.WriteByte(byte(len(wazeroVersion)))
// Version of wazero.
buf.WriteString(wazeroVersion)
if cm.ensureTermination {
buf.WriteByte(1)
} else {
buf.WriteByte(0)
}
// Number of *code (== locally defined functions in the module): 4 bytes.
buf.Write(u32.LeBytes(uint32(len(cm.functions))))
for i := 0; i < len(cm.functions); i++ {
f := &cm.functions[i]
// The stack pointer ceil (8 bytes).
buf.Write(u64.LeBytes(f.stackPointerCeil))
// The offset of this function in the executable (8 bytes).
buf.Write(u64.LeBytes(uint64(f.executableOffset)))
}
// The length of code segment (8 bytes).
buf.Write(u64.LeBytes(uint64(cm.executable.Len())))
// Append the native code.
buf.Write(cm.executable.Bytes())
return bytes.NewReader(buf.Bytes())
}
func deserializeCompiledModule(wazeroVersion string, reader io.ReadCloser, module *wasm.Module) (cm *compiledModule, staleCache bool, err error) {
defer reader.Close()
cacheHeaderSize := len(wazeroMagic) + 1 /* version size */ + len(wazeroVersion) + 1 /* ensure termination */ + 4 /* number of functions */
// Read the header before the native code.
header := make([]byte, cacheHeaderSize)
n, err := reader.Read(header)
if err != nil {
return nil, false, fmt.Errorf("compilationcache: error reading header: %v", err)
}
if n != cacheHeaderSize {
return nil, false, fmt.Errorf("compilationcache: invalid header length: %d", n)
}
// Check the version compatibility.
versionSize := int(header[len(wazeroMagic)])
cachedVersionBegin, cachedVersionEnd := len(wazeroMagic)+1, len(wazeroMagic)+1+versionSize
if cachedVersionEnd >= len(header) {
staleCache = true
return
} else if cachedVersion := string(header[cachedVersionBegin:cachedVersionEnd]); cachedVersion != wazeroVersion {
staleCache = true
return
}
ensureTermination := header[cachedVersionEnd] != 0
functionsNum := binary.LittleEndian.Uint32(header[len(header)-4:])
cm = &compiledModule{functions: make([]compiledFunction, functionsNum), ensureTermination: ensureTermination}
imported := module.ImportFunctionCount
var eightBytes [8]byte
for i := uint32(0); i < functionsNum; i++ {
f := &cm.functions[i]
f.parent = cm
// Read the stack pointer ceil.
if f.stackPointerCeil, err = readUint64(reader, &eightBytes); err != nil {
err = fmt.Errorf("compilationcache: error reading func[%d] stack pointer ceil: %v", i, err)
return
}
// Read the offset of each function in the executable.
var offset uint64
if offset, err = readUint64(reader, &eightBytes); err != nil {
err = fmt.Errorf("compilationcache: error reading func[%d] executable offset: %v", i, err)
return
}
f.executableOffset = uintptr(offset)
f.index = imported + i
}
executableLen, err := readUint64(reader, &eightBytes)
if err != nil {
err = fmt.Errorf("compilationcache: error reading executable size: %v", err)
return
}
if executableLen > 0 {
if err = cm.executable.Map(int(executableLen)); err != nil {
err = fmt.Errorf("compilationcache: error mmapping executable (len=%d): %v", executableLen, err)
return
}
_, err = io.ReadFull(reader, cm.executable.Bytes())
if err != nil {
err = fmt.Errorf("compilationcache: error reading executable (len=%d): %v", executableLen, err)
return
}
if runtime.GOARCH == "arm64" {
// On arm64, we cannot give all of rwx at the same time, so we change it to exec.
if err = platform.MprotectRX(cm.executable.Bytes()); err != nil {
return
}
}
}
return
}
// readUint64 strictly reads an uint64 in little-endian byte order, using the
// given array as a buffer. This returns io.EOF if less than 8 bytes were read.
func readUint64(reader io.Reader, b *[8]byte) (uint64, error) {
s := b[0:8]
n, err := reader.Read(s)
if err != nil {
return 0, err
} else if n < 8 { // more strict than reader.Read
return 0, io.EOF
}
// Read the u64 from the underlying buffer.
ret := binary.LittleEndian.Uint64(s)
// Clear the underlying array.
for i := 0; i < 8; i++ {
b[i] = 0
}
return ret, nil
}