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chromium / v8 / v8 / 890d28f3615769c3aa82b1bdf7df12c55774f909 / . / src / wasm / module-decoder.cc
blob: b0d2314a3ce8b281f132b36ce250b9bd4b5ed41c [file] [log] [blame]
// Copyright 2015 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "src/wasm/module-decoder.h"
#include "src/base/functional.h"
#include "src/base/platform/platform.h"
#include "src/flags.h"
#include "src/macro-assembler.h"
#include "src/objects.h"
#include "src/v8.h"
#include "src/wasm/decoder.h"
#include "src/wasm/wasm-limits.h"
namespace v8 {
namespace internal {
namespace wasm {
#if DEBUG
#define TRACE(...) \
do { \
if (FLAG_trace_wasm_decoder) PrintF(__VA_ARGS__); \
} while (false)
#else
#define TRACE(...)
#endif
namespace {
const char* kNameString = "name";
const size_t kNameStringLength = 4;
LocalType TypeOf(const WasmModule* module, const WasmInitExpr& expr) {
switch (expr.kind) {
case WasmInitExpr::kNone:
return kAstStmt;
case WasmInitExpr::kGlobalIndex:
return expr.val.global_index < module->globals.size()
? module->globals[expr.val.global_index].type
: kAstStmt;
case WasmInitExpr::kI32Const:
return kAstI32;
case WasmInitExpr::kI64Const:
return kAstI64;
case WasmInitExpr::kF32Const:
return kAstF32;
case WasmInitExpr::kF64Const:
return kAstF64;
default:
UNREACHABLE();
return kAstStmt;
}
}
// An iterator over the sections in a WASM binary module.
// Automatically skips all unknown sections.
class WasmSectionIterator {
public:
explicit WasmSectionIterator(Decoder& decoder)
: decoder_(decoder),
section_code_(kUnknownSectionCode),
section_start_(decoder.pc()),
section_end_(decoder.pc()) {
next();
}
inline bool more() const {
return section_code_ != kUnknownSectionCode && decoder_.more();
}
inline WasmSectionCode section_code() const { return section_code_; }
inline const byte* section_start() const { return section_start_; }
inline uint32_t section_length() const {
return static_cast<uint32_t>(section_end_ - section_start_);
}
inline const byte* payload_start() const { return payload_start_; }
inline uint32_t payload_length() const {
return static_cast<uint32_t>(section_end_ - payload_start_);
}
inline const byte* section_end() const { return section_end_; }
// Advances to the next section, checking that decoding the current section
// stopped at {section_end_}.
void advance() {
if (decoder_.pc() != section_end_) {
const char* msg = decoder_.pc() < section_end_ ? "shorter" : "longer";
decoder_.error(decoder_.pc(), decoder_.pc(),
"section was %s than expected size "
"(%u bytes expected, %zu decoded)",
msg, section_length(),
static_cast<size_t>(decoder_.pc() - section_start_));
}
next();
}
private:
Decoder& decoder_;
WasmSectionCode section_code_;
const byte* section_start_;
const byte* payload_start_;
const byte* section_end_;
// Reads the section code/name at the current position and sets up
// the internal fields.
void next() {
while (true) {
if (!decoder_.more()) {
section_code_ = kUnknownSectionCode;
return;
}
uint8_t section_code = decoder_.consume_u8("section code");
// Read and check the section size.
uint32_t section_length = decoder_.consume_u32v("section length");
section_start_ = decoder_.pc();
payload_start_ = section_start_;
if (decoder_.checkAvailable(section_length)) {
// Get the limit of the section within the module.
section_end_ = section_start_ + section_length;
} else {
// The section would extend beyond the end of the module.
section_end_ = section_start_;
}
if (section_code == kUnknownSectionCode) {
// Check for the known "name" section.
uint32_t string_length = decoder_.consume_u32v("section name length");
const byte* section_name_start = decoder_.pc();
decoder_.consume_bytes(string_length, "section name");
if (decoder_.failed() || decoder_.pc() > section_end_) {
TRACE("Section name of length %u couldn't be read\n", string_length);
section_code_ = kUnknownSectionCode;
return;
}
payload_start_ = decoder_.pc();
TRACE(" +%d section name : \"%.*s\"\n",
static_cast<int>(section_name_start - decoder_.start()),
string_length < 20 ? string_length : 20, section_name_start);
if (string_length == kNameStringLength &&
strncmp(reinterpret_cast<const char*>(section_name_start),
kNameString, kNameStringLength) == 0) {
section_code = kNameSectionCode;
} else {
section_code = kUnknownSectionCode;
}
} else if (!IsValidSectionCode(section_code)) {
decoder_.error(decoder_.pc(), decoder_.pc(),
"unknown section code #0x%02x", section_code);
section_code = kUnknownSectionCode;
}
section_code_ = static_cast<WasmSectionCode>(section_code);
TRACE("Section: %s\n", SectionName(section_code_));
if (section_code_ == kUnknownSectionCode &&
section_end_ > decoder_.pc()) {
// skip to the end of the unknown section.
uint32_t remaining =
static_cast<uint32_t>(section_end_ - decoder_.pc());
decoder_.consume_bytes(remaining, "section payload");
// fall through and continue to the next section.
} else {
return;
}
}
}
};
// The main logic for decoding the bytes of a module.
class ModuleDecoder : public Decoder {
public:
ModuleDecoder(Zone* zone, const byte* module_start, const byte* module_end,
ModuleOrigin origin)
: Decoder(module_start, module_end), module_zone(zone), origin_(origin) {
result_.start = start_;
if (limit_ < start_) {
error(start_, "end is less than start");
limit_ = start_;
}
}
virtual void onFirstError() {
pc_ = limit_; // On error, terminate section decoding loop.
}
void DumpModule(const ModuleResult& result) {
std::string path;
if (FLAG_dump_wasm_module_path) {
path = FLAG_dump_wasm_module_path;
if (path.size() &&
!base::OS::isDirectorySeparator(path[path.size() - 1])) {
path += base::OS::DirectorySeparator();
}
}
// File are named `HASH.{ok,failed}.wasm`.
size_t hash = base::hash_range(start_, limit_);
char buf[32] = {'\0'};
#if V8_OS_WIN && _MSC_VER < 1900
#define snprintf sprintf_s
#endif
snprintf(buf, sizeof(buf) - 1, "%016zx.%s.wasm", hash,
result.ok() ? "ok" : "failed");
std::string name(buf);
if (FILE* wasm_file = base::OS::FOpen((path + name).c_str(), "wb")) {
fwrite(start_, limit_ - start_, 1, wasm_file);
fclose(wasm_file);
}
}
// Decodes an entire module.
ModuleResult DecodeModule(bool verify_functions = true) {
pc_ = start_;
WasmModule* module = new WasmModule(module_zone);
module->min_mem_pages = 0;
module->max_mem_pages = 0;
module->mem_export = false;
module->origin = origin_;
const byte* pos = pc_;
uint32_t magic_word = consume_u32("wasm magic");
#define BYTES(x) (x & 0xff), (x >> 8) & 0xff, (x >> 16) & 0xff, (x >> 24) & 0xff
if (magic_word != kWasmMagic) {
error(pos, pos,
"expected magic word %02x %02x %02x %02x, "
"found %02x %02x %02x %02x",
BYTES(kWasmMagic), BYTES(magic_word));
}
pos = pc_;
{
uint32_t magic_version = consume_u32("wasm version");
if (magic_version != kWasmVersion) {
error(pos, pos,
"expected version %02x %02x %02x %02x, "
"found %02x %02x %02x %02x",
BYTES(kWasmVersion), BYTES(magic_version));
}
}
WasmSectionIterator section_iter(*this);
// ===== Type section ====================================================
if (section_iter.section_code() == kTypeSectionCode) {
uint32_t signatures_count = consume_u32v("signatures count");
module->signatures.reserve(SafeReserve(signatures_count));
for (uint32_t i = 0; ok() && i < signatures_count; ++i) {
TRACE("DecodeSignature[%d] module+%d\n", i,
static_cast<int>(pc_ - start_));
FunctionSig* s = consume_sig();
module->signatures.push_back(s);
}
section_iter.advance();
}
// ===== Import section ==================================================
if (section_iter.section_code() == kImportSectionCode) {
uint32_t import_table_count = consume_u32v("import table count");
module->import_table.reserve(SafeReserve(import_table_count));
for (uint32_t i = 0; ok() && i < import_table_count; ++i) {
TRACE("DecodeImportTable[%d] module+%d\n", i,
static_cast<int>(pc_ - start_));
module->import_table.push_back({
0, // module_name_length
0, // module_name_offset
0, // field_name_offset
0, // field_name_length
kExternalFunction, // kind
0 // index
});
WasmImport* import = &module->import_table.back();
const byte* pos = pc_;
import->module_name_offset =
consume_string(&import->module_name_length, true);
if (import->module_name_length == 0) {
error(pos, "import module name cannot be NULL");
}
import->field_name_offset =
consume_string(&import->field_name_length, true);
import->kind = static_cast<WasmExternalKind>(consume_u8("import kind"));
switch (import->kind) {
case kExternalFunction: {
// ===== Imported function =======================================
import->index = static_cast<uint32_t>(module->functions.size());
module->num_imported_functions++;
module->functions.push_back({nullptr, // sig
import->index, // func_index
0, // sig_index
0, // name_offset
0, // name_length
0, // code_start_offset
0, // code_end_offset
true, // imported
false}); // exported
WasmFunction* function = &module->functions.back();
function->sig_index = consume_sig_index(module, &function->sig);
break;
}
case kExternalTable: {
// ===== Imported table ==========================================
import->index =
static_cast<uint32_t>(module->function_tables.size());
module->function_tables.push_back({0, 0, false,
std::vector<int32_t>(), true,
false, SignatureMap()});
expect_u8("element type", kWasmAnyFunctionTypeForm);
WasmIndirectFunctionTable* table = &module->function_tables.back();
consume_resizable_limits("element count", "elements",
kV8MaxWasmTableSize, &table->min_size,
&table->has_max, kV8MaxWasmTableSize,
&table->max_size);
break;
}
case kExternalMemory: {
// ===== Imported memory =========================================
bool has_max = false;
consume_resizable_limits("memory", "pages", kV8MaxWasmMemoryPages,
&module->min_mem_pages, &has_max,
kSpecMaxWasmMemoryPages,
&module->max_mem_pages);
module->has_memory = true;
break;
}
case kExternalGlobal: {
// ===== Imported global =========================================
import->index = static_cast<uint32_t>(module->globals.size());
module->globals.push_back(
{kAstStmt, false, WasmInitExpr(), 0, true, false});
WasmGlobal* global = &module->globals.back();
global->type = consume_value_type();
global->mutability = consume_u8("mutability") != 0;
if (global->mutability) {
error("mutable globals cannot be imported");
}
break;
}
default:
error(pos, pos, "unknown import kind 0x%02x", import->kind);
break;
}
}
section_iter.advance();
}
// ===== Function section ================================================
if (section_iter.section_code() == kFunctionSectionCode) {
uint32_t functions_count = consume_u32v("functions count");
module->functions.reserve(SafeReserve(functions_count));
module->num_declared_functions = functions_count;
for (uint32_t i = 0; ok() && i < functions_count; ++i) {
uint32_t func_index = static_cast<uint32_t>(module->functions.size());
module->functions.push_back({nullptr, // sig
func_index, // func_index
0, // sig_index
0, // name_offset
0, // name_length
0, // code_start_offset
0, // code_end_offset
false, // imported
false}); // exported
WasmFunction* function = &module->functions.back();
function->sig_index = consume_sig_index(module, &function->sig);
}
section_iter.advance();
}
// ===== Table section ===================================================
if (section_iter.section_code() == kTableSectionCode) {
const byte* pos = pc_;
uint32_t table_count = consume_u32v("table count");
// Require at most one table for now.
if (table_count > 1) {
error(pos, pos, "invalid table count %d, maximum 1", table_count);
}
if (module->function_tables.size() < 1) {
module->function_tables.push_back({0, 0, false, std::vector<int32_t>(),
false, false, SignatureMap()});
}
for (uint32_t i = 0; ok() && i < table_count; i++) {
WasmIndirectFunctionTable* table = &module->function_tables.back();
expect_u8("table type", kWasmAnyFunctionTypeForm);
consume_resizable_limits(
"table elements", "elements", kV8MaxWasmTableSize, &table->min_size,
&table->has_max, kV8MaxWasmTableSize, &table->max_size);
}
section_iter.advance();
}
// ===== Memory section ==================================================
if (section_iter.section_code() == kMemorySectionCode) {
const byte* pos = pc_;
uint32_t memory_count = consume_u32v("memory count");
// Require at most one memory for now.
if (memory_count > 1) {
error(pos, pos, "invalid memory count %d, maximum 1", memory_count);
}
for (uint32_t i = 0; ok() && i < memory_count; i++) {
bool has_max = false;
consume_resizable_limits(
"memory", "pages", kV8MaxWasmMemoryPages, &module->min_mem_pages,
&has_max, kSpecMaxWasmMemoryPages, &module->max_mem_pages);
}
module->has_memory = true;
section_iter.advance();
}
// ===== Global section ==================================================
if (section_iter.section_code() == kGlobalSectionCode) {
uint32_t globals_count = consume_u32v("globals count");
uint32_t imported_globals = static_cast<uint32_t>(module->globals.size());
if (!IsWithinLimit(std::numeric_limits<int32_t>::max(), globals_count,
imported_globals)) {
error(pos, pos, "too many imported+defined globals: %u + %u",
imported_globals, globals_count);
}
module->globals.reserve(SafeReserve(imported_globals + globals_count));
for (uint32_t i = 0; ok() && i < globals_count; ++i) {
TRACE("DecodeGlobal[%d] module+%d\n", i,
static_cast<int>(pc_ - start_));
// Add an uninitialized global and pass a pointer to it.
module->globals.push_back(
{kAstStmt, false, WasmInitExpr(), 0, false, false});
WasmGlobal* global = &module->globals.back();
DecodeGlobalInModule(module, i + imported_globals, global);
}
section_iter.advance();
}
// ===== Export section ==================================================
if (section_iter.section_code() == kExportSectionCode) {
uint32_t export_table_count = consume_u32v("export table count");
module->export_table.reserve(SafeReserve(export_table_count));
for (uint32_t i = 0; ok() && i < export_table_count; ++i) {
TRACE("DecodeExportTable[%d] module+%d\n", i,
static_cast<int>(pc_ - start_));
module->export_table.push_back({
0, // name_length
0, // name_offset
kExternalFunction, // kind
0 // index
});
WasmExport* exp = &module->export_table.back();
exp->name_offset = consume_string(&exp->name_length, true);
const byte* pos = pc();
exp->kind = static_cast<WasmExternalKind>(consume_u8("export kind"));
switch (exp->kind) {
case kExternalFunction: {
WasmFunction* func = nullptr;
exp->index = consume_func_index(module, &func);
module->num_exported_functions++;
if (func) func->exported = true;
break;
}
case kExternalTable: {
WasmIndirectFunctionTable* table = nullptr;
exp->index = consume_table_index(module, &table);
if (table) table->exported = true;
break;
}
case kExternalMemory: {
uint32_t index = consume_u32v("memory index");
if (index != 0) error("invalid memory index != 0");
module->mem_export = true;
break;
}
case kExternalGlobal: {
WasmGlobal* global = nullptr;
exp->index = consume_global_index(module, &global);
if (global) {
if (global->mutability) {
error("mutable globals cannot be exported");
}
global->exported = true;
}
break;
}
default:
error(pos, pos, "invalid export kind 0x%02x", exp->kind);
break;
}
}
// Check for duplicate exports.
if (ok() && module->export_table.size() > 1) {
std::vector<WasmExport> sorted_exports(module->export_table);
const byte* base = start_;
auto cmp_less = [base](const WasmExport& a, const WasmExport& b) {
// Return true if a < b.
if (a.name_length != b.name_length) {
return a.name_length < b.name_length;
}
return memcmp(base + a.name_offset, base + b.name_offset,
a.name_length) < 0;
};
std::stable_sort(sorted_exports.begin(), sorted_exports.end(),
cmp_less);
auto it = sorted_exports.begin();
WasmExport* last = &*it++;
for (auto end = sorted_exports.end(); it != end; last = &*it++) {
DCHECK(!cmp_less(*it, *last)); // Vector must be sorted.
if (!cmp_less(*last, *it)) {
const byte* pc = start_ + it->name_offset;
error(pc, pc,
"Duplicate export name '%.*s' for functions %d and %d",
it->name_length, pc, last->index, it->index);
break;
}
}
}
section_iter.advance();
}
// ===== Start section ===================================================
if (section_iter.section_code() == kStartSectionCode) {
WasmFunction* func;
const byte* pos = pc_;
module->start_function_index = consume_func_index(module, &func);
if (func &&
(func->sig->parameter_count() > 0 || func->sig->return_count() > 0)) {
error(pos,
"invalid start function: non-zero parameter or return count");
}
section_iter.advance();
}
// ===== Elements section ================================================
if (section_iter.section_code() == kElementSectionCode) {
uint32_t element_count = consume_u32v("element count");
for (uint32_t i = 0; ok() && i < element_count; ++i) {
const byte* pos = pc();
uint32_t table_index = consume_u32v("table index");
if (table_index != 0) {
error(pos, pos, "illegal table index %u != 0", table_index);
}
WasmIndirectFunctionTable* table = nullptr;
if (table_index >= module->function_tables.size()) {
error(pos, pos, "out of bounds table index %u", table_index);
} else {
table = &module->function_tables[table_index];
}
WasmInitExpr offset = consume_init_expr(module, kAstI32);
uint32_t num_elem = consume_u32v("number of elements");
std::vector<uint32_t> vector;
module->table_inits.push_back({table_index, offset, vector});
WasmTableInit* init = &module->table_inits.back();
init->entries.reserve(SafeReserve(num_elem));
for (uint32_t j = 0; ok() && j < num_elem; j++) {
WasmFunction* func = nullptr;
uint32_t index = consume_func_index(module, &func);
init->entries.push_back(index);
if (table && index < module->functions.size()) {
// Canonicalize signature indices during decoding.
// TODO(titzer): suboptimal, redundant when verifying only.
table->map.FindOrInsert(module->functions[index].sig);
}
}
}
section_iter.advance();
}
// ===== Code section ====================================================
if (section_iter.section_code() == kCodeSectionCode) {
const byte* pos = pc_;
uint32_t functions_count = consume_u32v("functions count");
if (functions_count != module->num_declared_functions) {
error(pos, pos, "function body count %u mismatch (%u expected)",
functions_count, module->num_declared_functions);
}
for (uint32_t i = 0; ok() && i < functions_count; ++i) {
WasmFunction* function =
&module->functions[i + module->num_imported_functions];
uint32_t size = consume_u32v("body size");
function->code_start_offset = pc_offset();
function->code_end_offset = pc_offset() + size;
if (verify_functions) {
ModuleBytesEnv module_env(module, nullptr,
ModuleWireBytes(start_, limit_));
VerifyFunctionBody(i + module->num_imported_functions, &module_env,
function);
}
consume_bytes(size, "function body");
}
section_iter.advance();
}
// ===== Data section ====================================================
if (section_iter.section_code() == kDataSectionCode) {
uint32_t data_segments_count = consume_u32v("data segments count");
module->data_segments.reserve(SafeReserve(data_segments_count));
for (uint32_t i = 0; ok() && i < data_segments_count; ++i) {
if (!module->has_memory) {
error("cannot load data without memory");
break;
}
TRACE("DecodeDataSegment[%d] module+%d\n", i,
static_cast<int>(pc_ - start_));
module->data_segments.push_back({
WasmInitExpr(), // dest_addr
0, // source_offset
0 // source_size
});
WasmDataSegment* segment = &module->data_segments.back();
DecodeDataSegmentInModule(module, segment);
}
section_iter.advance();
}
// ===== Name section ====================================================
if (section_iter.section_code() == kNameSectionCode) {
uint32_t functions_count = consume_u32v("functions count");
for (uint32_t i = 0; ok() && i < functions_count; ++i) {
uint32_t function_name_length = 0;
uint32_t name_offset = consume_string(&function_name_length, false);
uint32_t func_index = i;
if (func_index < module->functions.size()) {
module->functions[func_index].name_offset = name_offset;
module->functions[func_index].name_length = function_name_length;
}
uint32_t local_names_count = consume_u32v("local names count");
for (uint32_t j = 0; ok() && j < local_names_count; j++) {
skip_string();
}
}
section_iter.advance();
}
// ===== Remaining sections ==============================================
if (section_iter.more() && ok()) {
error(pc(), pc(), "unexpected section: %s",
SectionName(section_iter.section_code()));
}
if (ok()) {
CalculateGlobalOffsets(module);
}
const WasmModule* finished_module = module;
ModuleResult result = toResult(finished_module);
if (verify_functions && result.ok()) {
result.MoveFrom(result_); // Copy error code and location.
}
if (FLAG_dump_wasm_module) DumpModule(result);
return result;
}
uint32_t SafeReserve(uint32_t count) {
// Avoid OOM by only reserving up to a certain size.
const uint32_t kMaxReserve = 20000;
return count < kMaxReserve ? count : kMaxReserve;
}
// Decodes a single anonymous function starting at {start_}.
FunctionResult DecodeSingleFunction(ModuleBytesEnv* module_env,
WasmFunction* function) {
pc_ = start_;
function->sig = consume_sig(); // read signature
function->name_offset = 0; // ---- name
function->name_length = 0; // ---- name length
function->code_start_offset = off(pc_); // ---- code start
function->code_end_offset = off(limit_); // ---- code end
if (ok()) VerifyFunctionBody(0, module_env, function);
FunctionResult result;
result.MoveFrom(result_); // Copy error code and location.
result.val = function;
return result;
}
// Decodes a single function signature at {start}.
FunctionSig* DecodeFunctionSignature(const byte* start) {
pc_ = start;
FunctionSig* result = consume_sig();
return ok() ? result : nullptr;
}
WasmInitExpr DecodeInitExpr(const byte* start) {
pc_ = start;
return consume_init_expr(nullptr, kAstStmt);
}
private:
Zone* module_zone;
ModuleResult result_;
ModuleOrigin origin_;
uint32_t off(const byte* ptr) { return static_cast<uint32_t>(ptr - start_); }
// Decodes a single global entry inside a module starting at {pc_}.
void DecodeGlobalInModule(WasmModule* module, uint32_t index,
WasmGlobal* global) {
global->type = consume_value_type();
global->mutability = consume_u8("mutability") != 0;
const byte* pos = pc();
global->init = consume_init_expr(module, kAstStmt);
switch (global->init.kind) {
case WasmInitExpr::kGlobalIndex: {
uint32_t other_index = global->init.val.global_index;
if (other_index >= index) {
error(pos, pos,
"invalid global index in init expression, "
"index %u, other_index %u",
index, other_index);
} else if (module->globals[other_index].type != global->type) {
error(pos, pos,
"type mismatch in global initialization "
"(from global #%u), expected %s, got %s",
other_index, WasmOpcodes::TypeName(global->type),
WasmOpcodes::TypeName(module->globals[other_index].type));
}
break;
}
default:
if (global->type != TypeOf(module, global->init)) {
error(pos, pos,
"type error in global initialization, expected %s, got %s",
WasmOpcodes::TypeName(global->type),
WasmOpcodes::TypeName(TypeOf(module, global->init)));
}
}
}
bool IsWithinLimit(uint32_t limit, uint32_t offset, uint32_t size) {
if (offset > limit) return false;
if ((offset + size) < offset) return false; // overflow
return (offset + size) <= limit;
}
// Decodes a single data segment entry inside a module starting at {pc_}.
void DecodeDataSegmentInModule(WasmModule* module, WasmDataSegment* segment) {
const byte* start = pc_;
expect_u8("linear memory index", 0);
segment->dest_addr = consume_init_expr(module, kAstI32);
segment->source_size = consume_u32v("source size");
segment->source_offset = static_cast<uint32_t>(pc_ - start_);
// Validate the data is in the module.
uint32_t module_limit = static_cast<uint32_t>(limit_ - start_);
if (!IsWithinLimit(module_limit, segment->source_offset,
segment->source_size)) {
error(start, "segment out of bounds of module");
}
consume_bytes(segment->source_size, "segment data");
}
// Calculate individual global offsets and total size of globals table.
void CalculateGlobalOffsets(WasmModule* module) {
uint32_t offset = 0;
if (module->globals.size() == 0) {
module->globals_size = 0;
return;
}
for (WasmGlobal& global : module->globals) {
byte size =
WasmOpcodes::MemSize(WasmOpcodes::MachineTypeFor(global.type));
offset = (offset + size - 1) & ~(size - 1); // align
global.offset = offset;
offset += size;
}
module->globals_size = offset;
}
// Verifies the body (code) of a given function.
void VerifyFunctionBody(uint32_t func_num, ModuleBytesEnv* menv,
WasmFunction* function) {
if (FLAG_trace_wasm_decoder || FLAG_trace_wasm_decode_time) {
OFStream os(stdout);
os << "Verifying WASM function " << WasmFunctionName(function, menv)
<< std::endl;
}
FunctionBody body = {menv, function->sig, start_,
start_ + function->code_start_offset,
start_ + function->code_end_offset};
DecodeResult result = VerifyWasmCode(module_zone->allocator(), body);
if (result.failed()) {
// Wrap the error message from the function decoder.
std::ostringstream str;
str << "in function " << WasmFunctionName(function, menv) << ": ";
str << result;
std::string strval = str.str();
const char* raw = strval.c_str();
size_t len = strlen(raw);
char* buffer = new char[len];
strncpy(buffer, raw, len);
buffer[len - 1] = 0;
// Copy error code and location.
result_.MoveFrom(result);
result_.error_msg.reset(buffer);
}
}
// Reads a length-prefixed string, checking that it is within bounds. Returns
// the offset of the string, and the length as an out parameter.
uint32_t consume_string(uint32_t* length, bool validate_utf8) {
*length = consume_u32v("string length");
uint32_t offset = pc_offset();
const byte* string_start = pc_;
// Consume bytes before validation to guarantee that the string is not oob.
if (*length > 0) consume_bytes(*length, "string");
if (ok() && validate_utf8 &&
!unibrow::Utf8::Validate(string_start, *length)) {
error(string_start, "no valid UTF-8 string");
}
return offset;
}
// Skips over a length-prefixed string, but checks that it is within bounds.
void skip_string() {
uint32_t length = consume_u32v("string length");
consume_bytes(length, "string");
}
uint32_t consume_sig_index(WasmModule* module, FunctionSig** sig) {
const byte* pos = pc_;
uint32_t sig_index = consume_u32v("signature index");
if (sig_index >= module->signatures.size()) {
error(pos, pos, "signature index %u out of bounds (%d signatures)",
sig_index, static_cast<int>(module->signatures.size()));
*sig = nullptr;
return 0;
}
*sig = module->signatures[sig_index];
return sig_index;
}
uint32_t consume_func_index(WasmModule* module, WasmFunction** func) {
return consume_index("function index", module->functions, func);
}
uint32_t consume_global_index(WasmModule* module, WasmGlobal** global) {
return consume_index("global index", module->globals, global);
}
uint32_t consume_table_index(WasmModule* module,
WasmIndirectFunctionTable** table) {
return consume_index("table index", module->function_tables, table);
}
template <typename T>
uint32_t consume_index(const char* name, std::vector<T>& vector, T** ptr) {
const byte* pos = pc_;
uint32_t index = consume_u32v(name);
if (index >= vector.size()) {
error(pos, pos, "%s %u out of bounds (%d entries)", name, index,
static_cast<int>(vector.size()));
*ptr = nullptr;
return 0;
}
*ptr = &vector[index];
return index;
}
void consume_resizable_limits(const char* name, const char* units,
uint32_t max_initial, uint32_t* initial,
bool* has_max, uint32_t max_maximum,
uint32_t* maximum) {
uint32_t flags = consume_u32v("resizable limits flags");
const byte* pos = pc();
*initial = consume_u32v("initial size");
*has_max = false;
if (*initial > max_initial) {
error(pos, pos,
"initial %s size (%u %s) is larger than implementation limit (%u)",
name, *initial, units, max_initial);
}
if (flags & 1) {
*has_max = true;
pos = pc();
*maximum = consume_u32v("maximum size");
if (*maximum > max_maximum) {
error(
pos, pos,
"maximum %s size (%u %s) is larger than implementation limit (%u)",
name, *maximum, units, max_maximum);
}
if (*maximum < *initial) {
error(pos, pos, "maximum %s size (%u %s) is less than initial (%u %s)",
name, *maximum, units, *initial, units);
}
} else {
*has_max = false;
*maximum = max_initial;
}
}
bool expect_u8(const char* name, uint8_t expected) {
const byte* pos = pc();
uint8_t value = consume_u8(name);
if (value != expected) {
error(pos, pos, "expected %s 0x%02x, got 0x%02x", name, expected, value);
return false;
}
return true;
}
WasmInitExpr consume_init_expr(WasmModule* module, LocalType expected) {
const byte* pos = pc();
uint8_t opcode = consume_u8("opcode");
WasmInitExpr expr;
unsigned len = 0;
switch (opcode) {
case kExprGetGlobal: {
GlobalIndexOperand operand(this, pc() - 1);
if (module->globals.size() <= operand.index) {
error("global index is out of bounds");
expr.kind = WasmInitExpr::kNone;
expr.val.i32_const = 0;
break;
}
WasmGlobal* global = &module->globals[operand.index];
if (global->mutability || !global->imported) {
error(
"only immutable imported globals can be used in initializer "
"expressions");
expr.kind = WasmInitExpr::kNone;
expr.val.i32_const = 0;
break;
}
expr.kind = WasmInitExpr::kGlobalIndex;
expr.val.global_index = operand.index;
len = operand.length;
break;
}
case kExprI32Const: {
ImmI32Operand operand(this, pc() - 1);
expr.kind = WasmInitExpr::kI32Const;
expr.val.i32_const = operand.value;
len = operand.length;
break;
}
case kExprF32Const: {
ImmF32Operand operand(this, pc() - 1);
expr.kind = WasmInitExpr::kF32Const;
expr.val.f32_const = operand.value;
len = operand.length;
break;
}
case kExprI64Const: {
ImmI64Operand operand(this, pc() - 1);
expr.kind = WasmInitExpr::kI64Const;
expr.val.i64_const = operand.value;
len = operand.length;
break;
}
case kExprF64Const: {
ImmF64Operand operand(this, pc() - 1);
expr.kind = WasmInitExpr::kF64Const;
expr.val.f64_const = operand.value;
len = operand.length;
break;
}
default: {
error("invalid opcode in initialization expression");
expr.kind = WasmInitExpr::kNone;
expr.val.i32_const = 0;
}
}
consume_bytes(len, "init code");
if (!expect_u8("end opcode", kExprEnd)) {
expr.kind = WasmInitExpr::kNone;
}
if (expected != kAstStmt && TypeOf(module, expr) != kAstI32) {
error(pos, pos, "type error in init expression, expected %s, got %s",
WasmOpcodes::TypeName(expected),
WasmOpcodes::TypeName(TypeOf(module, expr)));
}
return expr;
}
// Reads a single 8-bit integer, interpreting it as a local type.
LocalType consume_value_type() {
byte val = consume_u8("value type");
LocalTypeCode t = static_cast<LocalTypeCode>(val);
switch (t) {
case kLocalI32:
return kAstI32;
case kLocalI64:
return kAstI64;
case kLocalF32:
return kAstF32;
case kLocalF64:
return kAstF64;
case kLocalS128:
if (origin_ != kAsmJsOrigin && FLAG_wasm_simd_prototype) {
return kAstS128;
} else {
error(pc_ - 1, "invalid local type");
return kAstStmt;
}
default:
error(pc_ - 1, "invalid local type");
return kAstStmt;
}
}
// Parses a type entry, which is currently limited to functions only.
FunctionSig* consume_sig() {
if (!expect_u8("type form", kWasmFunctionTypeForm)) return nullptr;
// parse parameter types
uint32_t param_count = consume_u32v("param count");
std::vector<LocalType> params;
for (uint32_t i = 0; ok() && i < param_count; ++i) {
LocalType param = consume_value_type();
params.push_back(param);
}
// parse return types
const byte* pt = pc_;
uint32_t return_count = consume_u32v("return count");
if (return_count > kMaxReturnCount) {
error(pt, pt, "return count of %u exceeds maximum of %u", return_count,
kMaxReturnCount);
return nullptr;
}
std::vector<LocalType> returns;
for (uint32_t i = 0; ok() && i < return_count; ++i) {
LocalType ret = consume_value_type();
returns.push_back(ret);
}
if (failed()) {
// Decoding failed, return void -> void
return new (module_zone) FunctionSig(0, 0, nullptr);
}
// FunctionSig stores the return types first.
LocalType* buffer =
module_zone->NewArray<LocalType>(param_count + return_count);
uint32_t b = 0;
for (uint32_t i = 0; i < return_count; ++i) buffer[b++] = returns[i];
for (uint32_t i = 0; i < param_count; ++i) buffer[b++] = params[i];
return new (module_zone) FunctionSig(return_count, param_count, buffer);
}
};
// Helpers for nice error messages.
class ModuleError : public ModuleResult {
public:
explicit ModuleError(const char* msg) {
error_code = kError;
size_t len = strlen(msg) + 1;
char* result = new char[len];
strncpy(result, msg, len);
result[len - 1] = 0;
error_msg.reset(result);
}
};
// Helpers for nice error messages.
class FunctionError : public FunctionResult {
public:
explicit FunctionError(const char* msg) {
error_code = kError;
size_t len = strlen(msg) + 1;
char* result = new char[len];
strncpy(result, msg, len);
result[len - 1] = 0;
error_msg.reset(result);
}
};
// Find section with given section code. Return Vector of the payload, or null
// Vector if section is not found or module bytes are invalid.
Vector<const byte> FindSection(const byte* module_start, const byte* module_end,
WasmSectionCode code) {
Decoder decoder(module_start, module_end);
uint32_t magic_word = decoder.consume_u32("wasm magic");
if (magic_word != kWasmMagic) decoder.error("wrong magic word");
uint32_t magic_version = decoder.consume_u32("wasm version");
if (magic_version != kWasmVersion) decoder.error("wrong wasm version");
WasmSectionIterator section_iter(decoder);
while (section_iter.more()) {
if (section_iter.section_code() == code) {
return Vector<const uint8_t>(section_iter.payload_start(),
section_iter.payload_length());
}
decoder.consume_bytes(section_iter.payload_length(), "section payload");
section_iter.advance();
}
return Vector<const uint8_t>();
}
} // namespace
ModuleResult DecodeWasmModule(Isolate* isolate, const byte* module_start,
const byte* module_end, bool verify_functions,
ModuleOrigin origin) {
HistogramTimerScope wasm_decode_module_time_scope(
isolate->counters()->wasm_decode_module_time());
size_t size = module_end - module_start;
if (module_start > module_end) return ModuleError("start > end");
if (size >= kV8MaxWasmModuleSize)
return ModuleError("size > maximum module size");
// TODO(bradnelson): Improve histogram handling of size_t.
isolate->counters()->wasm_module_size_bytes()->AddSample(
static_cast<int>(size));
// Signatures are stored in zone memory, which have the same lifetime
// as the {module}.
Zone* zone = new Zone(isolate->allocator(), ZONE_NAME);
ModuleDecoder decoder(zone, module_start, module_end, origin);
ModuleResult result = decoder.DecodeModule(verify_functions);
// TODO(bradnelson): Improve histogram handling of size_t.
// TODO(titzer): this isn't accurate, since it doesn't count the data
// allocated on the C++ heap.
// https://bugs.chromium.org/p/chromium/issues/detail?id=657320
isolate->counters()->wasm_decode_module_peak_memory_bytes()->AddSample(
static_cast<int>(zone->allocation_size()));
return result;
}
FunctionSig* DecodeWasmSignatureForTesting(Zone* zone, const byte* start,
const byte* end) {
ModuleDecoder decoder(zone, start, end, kWasmOrigin);
return decoder.DecodeFunctionSignature(start);
}
WasmInitExpr DecodeWasmInitExprForTesting(const byte* start, const byte* end) {
AccountingAllocator allocator;
Zone zone(&allocator, ZONE_NAME);
ModuleDecoder decoder(&zone, start, end, kWasmOrigin);
return decoder.DecodeInitExpr(start);
}
FunctionResult DecodeWasmFunction(Isolate* isolate, Zone* zone,
ModuleBytesEnv* module_env,
const byte* function_start,
const byte* function_end) {
HistogramTimerScope wasm_decode_function_time_scope(
isolate->counters()->wasm_decode_function_time());
size_t size = function_end - function_start;
if (function_start > function_end) return FunctionError("start > end");
if (size > kV8MaxWasmFunctionSize)
return FunctionError("size > maximum function size");
isolate->counters()->wasm_function_size_bytes()->AddSample(
static_cast<int>(size));
WasmFunction* function = new WasmFunction();
ModuleDecoder decoder(zone, function_start, function_end, kWasmOrigin);
return decoder.DecodeSingleFunction(module_env, function);
}
FunctionOffsetsResult DecodeWasmFunctionOffsets(const byte* module_start,
const byte* module_end) {
// Find and decode the code section.
Vector<const byte> code_section =
FindSection(module_start, module_end, kCodeSectionCode);
Decoder decoder(code_section.start(), code_section.end());
FunctionOffsets table;
if (!code_section.start()) {
decoder.error("no code section");
return decoder.toResult(std::move(table));
}
uint32_t functions_count = decoder.consume_u32v("functions count");
// Reserve space for the entries, taking care of invalid input.
if (functions_count < static_cast<unsigned>(code_section.length()) / 2) {
table.reserve(functions_count);
}
int section_offset = static_cast<int>(code_section.start() - module_start);
DCHECK_LE(0, section_offset);
for (uint32_t i = 0; i < functions_count && decoder.ok(); ++i) {
uint32_t size = decoder.consume_u32v("body size");
int offset = static_cast<int>(section_offset + decoder.pc_offset());
table.push_back(std::make_pair(offset, static_cast<int>(size)));
DCHECK(table.back().first >= 0 && table.back().second >= 0);
decoder.consume_bytes(size);
}
if (decoder.more()) decoder.error("unexpected additional bytes");
return decoder.toResult(std::move(table));
}
AsmJsOffsetsResult DecodeAsmJsOffsets(const byte* tables_start,
const byte* tables_end) {
AsmJsOffsets table;
Decoder decoder(tables_start, tables_end);
uint32_t functions_count = decoder.consume_u32v("functions count");
// Reserve space for the entries, taking care of invalid input.
if (functions_count < static_cast<unsigned>(tables_end - tables_start)) {
table.reserve(functions_count);
}
for (uint32_t i = 0; i < functions_count && decoder.ok(); ++i) {
uint32_t size = decoder.consume_u32v("table size");
if (size == 0) {
table.push_back(std::vector<AsmJsOffsetEntry>());
continue;
}
if (!decoder.checkAvailable(size)) {
decoder.error("illegal asm function offset table size");
}
const byte* table_end = decoder.pc() + size;
uint32_t locals_size = decoder.consume_u32("locals size");
int last_byte_offset = locals_size;
int last_asm_position = 0;
std::vector<AsmJsOffsetEntry> func_asm_offsets;
func_asm_offsets.reserve(size / 4); // conservative estimation
while (decoder.ok() && decoder.pc() < table_end) {
last_byte_offset += decoder.consume_u32v("byte offset delta");
int call_position =
last_asm_position + decoder.consume_i32v("call position delta");
int to_number_position =
call_position + decoder.consume_i32v("to_number position delta");
last_asm_position = to_number_position;
func_asm_offsets.push_back(
{last_byte_offset, call_position, to_number_position});
}
if (decoder.pc() != table_end) {
decoder.error("broken asm offset table");
}
table.push_back(std::move(func_asm_offsets));
}
if (decoder.more()) decoder.error("unexpected additional bytes");
return decoder.toResult(std::move(table));
}
} // namespace wasm
} // namespace internal
} // namespace v8