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[experiment] add alternative wasm sqlite3 implementation available via build-tag (#2863)

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This allows for building GoToSocial with [SQLite transpiled to WASM](https://github.com/ncruces/go-sqlite3) and accessed through [Wazero](https://wazero.io/).
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kim 2024-05-27 15:46:15 +00:00 • committed by GitHub
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vendor/github.com/tetratelabs/wazero/internal/wasm/table.go generated vendored Normal file
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package wasm
import (
"fmt"
"math"
"sync"
"github.com/tetratelabs/wazero/api"
"github.com/tetratelabs/wazero/internal/leb128"
)
// Table describes the limits of elements and its type in a table.
type Table struct {
Min uint32
Max *uint32
Type RefType
}
// RefType is either RefTypeFuncref or RefTypeExternref as of WebAssembly core 2.0.
type RefType = byte
const (
// RefTypeFuncref represents a reference to a function.
RefTypeFuncref = ValueTypeFuncref
// RefTypeExternref represents a reference to a host object, which is not currently supported in wazero.
RefTypeExternref = ValueTypeExternref
)
func RefTypeName(t RefType) (ret string) {
switch t {
case RefTypeFuncref:
ret = "funcref"
case RefTypeExternref:
ret = "externref"
default:
ret = fmt.Sprintf("unknown(0x%x)", t)
}
return
}
// ElementMode represents a mode of element segment which is either active, passive or declarative.
//
// https://www.w3.org/TR/2022/WD-wasm-core-2-20220419/syntax/modules.html#element-segments
type ElementMode = byte
const (
// ElementModeActive is the mode which requires the runtime to initialize table with the contents in .Init field combined with OffsetExpr.
ElementModeActive ElementMode = iota
// ElementModePassive is the mode which doesn't require the runtime to initialize table, and only used with OpcodeTableInitName.
ElementModePassive
// ElementModeDeclarative is introduced in reference-types proposal which can be used to declare function indexes used by OpcodeRefFunc.
ElementModeDeclarative
)
// ElementSegment are initialization instructions for a TableInstance
//
// See https://www.w3.org/TR/2019/REC-wasm-core-1-20191205/#syntax-elem
type ElementSegment struct {
// OffsetExpr returns the table element offset to apply to Init indices.
// Note: This can be validated prior to instantiation unless it includes OpcodeGlobalGet (an imported global).
OffsetExpr ConstantExpression
// TableIndex is the table's index to which this element segment is applied.
// Note: This is used if and only if the Mode is active.
TableIndex Index
// Followings are set/used regardless of the Mode.
// Init indices are (nullable) table elements where each index is the function index by which the module initialize the table.
Init []Index
// Type holds the type of this element segment, which is the RefType in WebAssembly 2.0.
Type RefType
// Mode is the mode of this element segment.
Mode ElementMode
}
const (
// ElementInitNullReference represents the null reference in ElementSegment's Init.
// In Wasm spec, an init item represents either Function's Index or null reference,
// and in wazero, we limit the maximum number of functions available in a module to
// MaximumFunctionIndex. Therefore, it is safe to use 1 << 31 to represent the null
// reference in Element segments.
ElementInitNullReference Index = 1 << 31
// elementInitImportedGlobalReferenceType represents an init item which is resolved via an imported global constexpr.
// The actual function reference stored at Global is only known at instantiation-time, so we set this flag
// to items of ElementSegment.Init at binary decoding, and unwrap this flag at instantiation to resolve the value.
//
// This might collide the init element resolved via ref.func instruction which is resolved with the func index at decoding,
// but in practice, that is not allowed in wazero thanks to our limit MaximumFunctionIndex. Thus, it is safe to set this flag
// in init element to indicate as such.
elementInitImportedGlobalReferenceType Index = 1 << 30
)
// unwrapElementInitGlobalReference takes an item of the init vector of an ElementSegment,
// and returns the Global index if it is supposed to get generated from a global.
// ok is true if the given init item is as such.
func unwrapElementInitGlobalReference(init Index) (_ Index, ok bool) {
if init&elementInitImportedGlobalReferenceType == elementInitImportedGlobalReferenceType {
return init &^ elementInitImportedGlobalReferenceType, true
}
return init, false
}
// WrapGlobalIndexAsElementInit wraps the given index as an init item which is resolved via an imported global value.
// See the comments on elementInitImportedGlobalReferenceType for more details.
func WrapGlobalIndexAsElementInit(init Index) Index {
return init | elementInitImportedGlobalReferenceType
}
// IsActive returns true if the element segment is "active" mode which requires the runtime to initialize table
// with the contents in .Init field.
func (e *ElementSegment) IsActive() bool {
return e.Mode == ElementModeActive
}
// TableInstance represents a table of (RefTypeFuncref) elements in a module.
//
// See https://www.w3.org/TR/2019/REC-wasm-core-1-20191205/#table-instances%E2%91%A0
type TableInstance struct {
// References holds references whose type is either RefTypeFuncref or RefTypeExternref (unsupported).
//
// Currently, only function references are supported.
References []Reference
// Min is the minimum (function) elements in this table and cannot grow to accommodate ElementSegment.
Min uint32
// Max if present is the maximum (function) elements in this table, or nil if unbounded.
Max *uint32
// Type is either RefTypeFuncref or RefTypeExternRef.
Type RefType
// The following is only used when the table is exported.
// involvingModuleInstances is a set of module instances which are involved in the table instance.
// This is critical for safety purpose because once a table is imported, it can hold any reference to
// any function in the owner and importing module instances. Therefore, these module instance,
// transitively the compiled modules, must be alive as long as the table instance is alive.
involvingModuleInstances []*ModuleInstance
// involvingModuleInstancesMutex is a mutex to protect involvingModuleInstances.
involvingModuleInstancesMutex sync.RWMutex
}
// ElementInstance represents an element instance in a module.
//
// See https://www.w3.org/TR/2022/WD-wasm-core-2-20220419/exec/runtime.html#element-instances
type ElementInstance = []Reference
// Reference is the runtime representation of RefType which is either RefTypeFuncref or RefTypeExternref.
type Reference = uintptr
// validateTable ensures any ElementSegment is valid. This caches results via Module.validatedActiveElementSegments.
// Note: limitsType are validated by decoders, so not re-validated here.
func (m *Module) validateTable(enabledFeatures api.CoreFeatures, tables []Table, maximumTableIndex uint32) error {
if len(tables) > int(maximumTableIndex) {
return fmt.Errorf("too many tables in a module: %d given with limit %d", len(tables), maximumTableIndex)
}
importedTableCount := m.ImportTableCount
// Create bounds checks as these can err prior to instantiation
funcCount := m.ImportFunctionCount + m.SectionElementCount(SectionIDFunction)
globalsCount := m.ImportGlobalCount + m.SectionElementCount(SectionIDGlobal)
// Now, we have to figure out which table elements can be resolved before instantiation and also fail early if there
// are any imported globals that are known to be invalid by their declarations.
for i := range m.ElementSection {
elem := &m.ElementSection[i]
idx := Index(i)
initCount := uint32(len(elem.Init))
// Any offset applied is to the element, not the function index: validate here if the funcidx is sound.
for ei, init := range elem.Init {
if init == ElementInitNullReference {
continue
}
index, ok := unwrapElementInitGlobalReference(init)
if ok {
if index >= globalsCount {
return fmt.Errorf("%s[%d].init[%d] global index %d out of range", SectionIDName(SectionIDElement), idx, ei, index)
}
} else {
if elem.Type == RefTypeExternref {
return fmt.Errorf("%s[%d].init[%d] must be ref.null but was %d", SectionIDName(SectionIDElement), idx, ei, init)
}
if index >= funcCount {
return fmt.Errorf("%s[%d].init[%d] func index %d out of range", SectionIDName(SectionIDElement), idx, ei, index)
}
}
}
if elem.IsActive() {
if len(tables) <= int(elem.TableIndex) {
return fmt.Errorf("unknown table %d as active element target", elem.TableIndex)
}
t := tables[elem.TableIndex]
if t.Type != elem.Type {
return fmt.Errorf("element type mismatch: table has %s but element has %s",
RefTypeName(t.Type), RefTypeName(elem.Type),
)
}
// global.get needs to be discovered during initialization
oc := elem.OffsetExpr.Opcode
if oc == OpcodeGlobalGet {
globalIdx, _, err := leb128.LoadUint32(elem.OffsetExpr.Data)
if err != nil {
return fmt.Errorf("%s[%d] couldn't read global.get parameter: %w", SectionIDName(SectionIDElement), idx, err)
} else if err = m.verifyImportGlobalI32(SectionIDElement, idx, globalIdx); err != nil {
return err
}
} else if oc == OpcodeI32Const {
// Per https://github.com/WebAssembly/spec/blob/wg-1.0/test/core/elem.wast#L117 we must pass if imported
// table has set its min=0. Per https://github.com/WebAssembly/spec/blob/wg-1.0/test/core/elem.wast#L142, we
// have to do fail if module-defined min=0.
if !enabledFeatures.IsEnabled(api.CoreFeatureReferenceTypes) && elem.TableIndex >= importedTableCount {
// Treat constants as signed as their interpretation is not yet known per /RATIONALE.md
o, _, err := leb128.LoadInt32(elem.OffsetExpr.Data)
if err != nil {
return fmt.Errorf("%s[%d] couldn't read i32.const parameter: %w", SectionIDName(SectionIDElement), idx, err)
}
offset := Index(o)
if err = checkSegmentBounds(t.Min, uint64(initCount)+uint64(offset), idx); err != nil {
return err
}
}
} else {
return fmt.Errorf("%s[%d] has an invalid const expression: %s", SectionIDName(SectionIDElement), idx, InstructionName(oc))
}
}
}
return nil
}
// buildTable returns TableInstances if the module defines or imports a table.
// - importedTables: returned as `tables` unmodified.
// - importedGlobals: include all instantiated, imported globals.
//
// If the result `init` is non-nil, it is the `tableInit` parameter of Engine.NewModuleEngine.
//
// Note: An error is only possible when an ElementSegment.OffsetExpr is out of range of the TableInstance.Min.
func (m *ModuleInstance) buildTables(module *Module, skipBoundCheck bool) (err error) {
idx := module.ImportTableCount
for i := range module.TableSection {
tsec := &module.TableSection[i]
// The module defining the table is the one that sets its Min/Max etc.
m.Tables[idx] = &TableInstance{
References: make([]Reference, tsec.Min), Min: tsec.Min, Max: tsec.Max,
Type: tsec.Type,
}
idx++
}
if !skipBoundCheck {
for elemI := range module.ElementSection { // Do not loop over the value since elementSegments is a slice of value.
elem := &module.ElementSection[elemI]
table := m.Tables[elem.TableIndex]
var offset uint32
if elem.OffsetExpr.Opcode == OpcodeGlobalGet {
// Ignore error as it's already validated.
globalIdx, _, _ := leb128.LoadUint32(elem.OffsetExpr.Data)
global := m.Globals[globalIdx]
offset = uint32(global.Val)
} else { // i32.const
// Ignore error as it's already validated.
o, _, _ := leb128.LoadInt32(elem.OffsetExpr.Data)
offset = uint32(o)
}
// Check to see if we are out-of-bounds
initCount := uint64(len(elem.Init))
if err = checkSegmentBounds(table.Min, uint64(offset)+initCount, Index(elemI)); err != nil {
return
}
}
}
return
}
// checkSegmentBounds fails if the capacity needed for an ElementSegment.Init is larger than limitsType.Min
//
// WebAssembly 1.0 (20191205) doesn't forbid growing to accommodate element segments, and spectests are inconsistent.
// For example, the spectests enforce elements within Table limitsType.Min, but ignore Import.DescTable min. What this
// means is we have to delay offset checks on imported tables until we link to them.
// e.g. https://github.com/WebAssembly/spec/blob/wg-1.0/test/core/elem.wast#L117 wants pass on min=0 for import
// e.g. https://github.com/WebAssembly/spec/blob/wg-1.0/test/core/elem.wast#L142 wants fail on min=0 module-defined
func checkSegmentBounds(min uint32, requireMin uint64, idx Index) error { // uint64 in case offset was set to -1
if requireMin > uint64(min) {
return fmt.Errorf("%s[%d].init exceeds min table size", SectionIDName(SectionIDElement), idx)
}
return nil
}
func (m *Module) verifyImportGlobalI32(sectionID SectionID, sectionIdx Index, idx uint32) error {
ig := uint32(math.MaxUint32) // +1 == 0
for i := range m.ImportSection {
imp := &m.ImportSection[i]
if imp.Type == ExternTypeGlobal {
ig++
if ig == idx {
if imp.DescGlobal.ValType != ValueTypeI32 {
return fmt.Errorf("%s[%d] (global.get %d): import[%d].global.ValType != i32", SectionIDName(sectionID), sectionIdx, idx, i)
}
return nil
}
}
}
return fmt.Errorf("%s[%d] (global.get %d): out of range of imported globals", SectionIDName(sectionID), sectionIdx, idx)
}
// Grow appends the `initialRef` by `delta` times into the References slice.
// Returns -1 if the operation is not valid, otherwise the old length of the table.
//
// https://www.w3.org/TR/2022/WD-wasm-core-2-20220419/exec/instructions.html#xref-syntax-instructions-syntax-instr-table-mathsf-table-grow-x
func (t *TableInstance) Grow(delta uint32, initialRef Reference) (currentLen uint32) {
currentLen = uint32(len(t.References))
if delta == 0 {
return
}
if newLen := int64(currentLen) + int64(delta); // adding as 64bit ints to avoid overflow.
newLen >= math.MaxUint32 || (t.Max != nil && newLen > int64(*t.Max)) {
return 0xffffffff // = -1 in signed 32-bit integer.
}
t.References = append(t.References, make([]uintptr, delta)...)
// Uses the copy trick for faster filling the new region with the initial value.
// https://gist.github.com/taylorza/df2f89d5f9ab3ffd06865062a4cf015d
newRegion := t.References[currentLen:]
newRegion[0] = initialRef
for i := 1; i < len(newRegion); i *= 2 {
copy(newRegion[i:], newRegion[:i])
}
return
}