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bootstrap: handle snapshot errors gracefully

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This patch refactors the SnapshotBuilder::Generate() routines
so that when running into errors during the snapshot building
process, they can exit gracefully by printing the error
and return a non-zero exit code. If the error is likely to
be caused by internal scripts, the return code would be 12,
if the error is caused by user scripts the return code would
be 1. In addition this refactors the generation of embedded
snapshots and directly writes to the output file stream
instead of producing an intermediate string with string
streams.

PR-URL: https://github.com/nodejs/node/pull/43531
Refs: https://github.com/nodejs/node/issues/35711
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>
This commit is contained in:
Joyee Cheung 2022-06-22 15:24:34 +08:00
parent 9bfabe8a79
commit 49bb1c6832
No known key found for this signature in database
GPG Key ID: 92B78A53C8303B8D
6 changed files with 206 additions and 173 deletions
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3
doc/api/process.md
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@ -3822,6 +3822,9 @@ cases:
options were set, but the port number chosen was invalid or unavailable.
* `13` **Unfinished Top-Level Await**: `await` was used outside of a function
in the top-level code, but the passed `Promise` never resolved.
* `14` **Snapshot Failure**: Node.js was started to build a V8 startup
snapshot and it failed because certain requirements of the state of
the application were not met.
* `>128` **Signal Exits**: If Node.js receives a fatal signal such as
`SIGKILL` or `SIGHUP`, then its exit code will be `128` plus the
value of the signal code. This is a standard POSIX practice, since

19
src/env.h
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@ -963,13 +963,17 @@ struct EnvSerializeInfo {
};
struct SnapshotData {
// The result of v8::SnapshotCreator::CreateBlob() during the snapshot
// building process.
v8::StartupData v8_snapshot_blob_data;
enum class DataOwnership { kOwned, kNotOwned };
static const size_t kNodeBaseContextIndex = 0;
static const size_t kNodeMainContextIndex = kNodeBaseContextIndex + 1;
DataOwnership data_ownership = DataOwnership::kOwned;
// The result of v8::SnapshotCreator::CreateBlob() during the snapshot
// building process.
v8::StartupData v8_snapshot_blob_data{nullptr, 0};
std::vector<size_t> isolate_data_indices;
// TODO(joyeecheung): there should be a vector of env_info once we snapshot
// the worker environments.
@ -979,6 +983,15 @@ struct SnapshotData {
// read only space. We use native_module::CodeCacheInfo because
// v8::ScriptCompiler::CachedData is not copyable.
std::vector<native_module::CodeCacheInfo> code_cache;
~SnapshotData();
SnapshotData(const SnapshotData&) = delete;
SnapshotData& operator=(const SnapshotData&) = delete;
SnapshotData(SnapshotData&&) = delete;
SnapshotData& operator=(SnapshotData&&) = delete;
SnapshotData() = default;
};
class Environment : public MemoryRetainer {

11
src/node_snapshot_builder.h
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@ -15,13 +15,14 @@ struct SnapshotData;
class NODE_EXTERN_PRIVATE SnapshotBuilder {
public:
static std::string Generate(const std::vector<std::string> args,
const std::vector<std::string> exec_args);
static int Generate(std::ostream& out,
const std::vector<std::string> args,
const std::vector<std::string> exec_args);
// Generate the snapshot into out.
static void Generate(SnapshotData* out,
const std::vector<std::string> args,
const std::vector<std::string> exec_args);
static int Generate(SnapshotData* out,
const std::vector<std::string> args,
const std::vector<std::string> exec_args);
// If nullptr is returned, the binary is not built with embedded
// snapshot.

328
src/node_snapshotable.cc
View File

@ -29,7 +29,6 @@ using v8::FunctionCallbackInfo;
using v8::HandleScope;
using v8::Isolate;
using v8::Local;
using v8::MaybeLocal;
using v8::Object;
using v8::ScriptCompiler;
using v8::ScriptOrigin;
@ -39,8 +38,15 @@ using v8::String;
using v8::TryCatch;
using v8::Value;
SnapshotData::~SnapshotData() {
if (data_ownership == DataOwnership::kOwned &&
v8_snapshot_blob_data.data != nullptr) {
delete[] v8_snapshot_blob_data.data;
}
}
template <typename T>
void WriteVector(std::ostringstream* ss, const T* vec, size_t size) {
void WriteVector(std::ostream* ss, const T* vec, size_t size) {
for (size_t i = 0; i < size; i++) {
*ss << std::to_string(vec[i]) << (i == size - 1 ? '\n' : ',');
}
@ -70,15 +76,14 @@ static std::string FormatSize(size_t size) {
return buf;
}
static void WriteStaticCodeCacheData(std::ostringstream* ss,
static void WriteStaticCodeCacheData(std::ostream* ss,
const native_module::CodeCacheInfo& info) {
*ss << "static const uint8_t " << GetCodeCacheDefName(info.id) << "[] = {\n";
WriteVector(ss, info.data.data(), info.data.size());
*ss << "};";
}
static void WriteCodeCacheInitializer(std::ostringstream* ss,
const std::string& id) {
static void WriteCodeCacheInitializer(std::ostream* ss, const std::string& id) {
std::string def_name = GetCodeCacheDefName(id);
*ss << " { \"" << id << "\",\n";
*ss << " {" << def_name << ",\n";
@ -87,9 +92,7 @@ static void WriteCodeCacheInitializer(std::ostringstream* ss,
*ss << " },\n";
}
std::string FormatBlob(SnapshotData* data) {
std::ostringstream ss;
void FormatBlob(std::ostream& ss, SnapshotData* data) {
ss << R"(#include <cstddef>
#include "env.h"
#include "node_snapshot_builder.h"
@ -116,6 +119,9 @@ static const int v8_snapshot_blob_size = )"
}
ss << R"(SnapshotData snapshot_data {
// -- data_ownership begins --
SnapshotData::DataOwnership::kNotOwned,
// -- data_ownership ends --
// -- v8_snapshot_blob_data begins --
{ v8_snapshot_blob_data, v8_snapshot_blob_size },
// -- v8_snapshot_blob_data ends --
@ -148,8 +154,6 @@ const SnapshotData* SnapshotBuilder::GetEmbeddedSnapshotData() {
}
} // namespace node
)";
return ss.str();
}
Mutex SnapshotBuilder::snapshot_data_mutex_;
@ -166,175 +170,185 @@ void SnapshotBuilder::InitializeIsolateParams(const SnapshotData* data,
const_cast<v8::StartupData*>(&(data->v8_snapshot_blob_data));
}
void SnapshotBuilder::Generate(SnapshotData* out,
const std::vector<std::string> args,
const std::vector<std::string> exec_args) {
// TODO(joyeecheung): share these exit code constants across the code base.
constexpr int UNCAUGHT_EXCEPTION_ERROR = 1;
constexpr int BOOTSTRAP_ERROR = 10;
constexpr int SNAPSHOT_ERROR = 14;
int SnapshotBuilder::Generate(SnapshotData* out,
const std::vector<std::string> args,
const std::vector<std::string> exec_args) {
const std::vector<intptr_t>& external_references =
CollectExternalReferences();
Isolate* isolate = Isolate::Allocate();
isolate->SetCaptureStackTraceForUncaughtExceptions(
true, 10, v8::StackTrace::StackTraceOptions::kDetailed);
// Must be done before the SnapshotCreator creation so that the
// memory reducer can be initialized.
per_process::v8_platform.Platform()->RegisterIsolate(isolate,
uv_default_loop());
std::unique_ptr<NodeMainInstance> main_instance;
std::string result;
SnapshotCreator creator(isolate, external_references.data());
isolate->SetCaptureStackTraceForUncaughtExceptions(
true, 10, v8::StackTrace::StackTraceOptions::kDetailed);
Environment* env = nullptr;
std::unique_ptr<NodeMainInstance> main_instance =
NodeMainInstance::Create(isolate,
uv_default_loop(),
per_process::v8_platform.Platform(),
args,
exec_args);
// The cleanups should be done in case of an early exit due to errors.
auto cleanup = OnScopeLeave([&]() {
// Must be done while the snapshot creator isolate is entered i.e. the
// creator is still alive. The snapshot creator destructor will destroy
// the isolate.
if (env != nullptr) {
FreeEnvironment(env);
}
main_instance->Dispose();
per_process::v8_platform.Platform()->UnregisterIsolate(isolate);
});
{
const std::vector<intptr_t>& external_references =
CollectExternalReferences();
SnapshotCreator creator(isolate, external_references.data());
Environment* env;
HandleScope scope(isolate);
TryCatch bootstrapCatch(isolate);
auto print_Exception = OnScopeLeave([&]() {
if (bootstrapCatch.HasCaught()) {
PrintCaughtException(
isolate, isolate->GetCurrentContext(), bootstrapCatch);
}
});
out->isolate_data_indices =
main_instance->isolate_data()->Serialize(&creator);
// The default context with only things created by V8.
Local<Context> default_context = Context::New(isolate);
// The Node.js-specific context with primodials, can be used by workers
// TODO(joyeecheung): investigate if this can be used by vm contexts
// without breaking compatibility.
Local<Context> base_context = NewContext(isolate);
if (base_context.IsEmpty()) {
return BOOTSTRAP_ERROR;
}
Local<Context> main_context = NewContext(isolate);
if (main_context.IsEmpty()) {
return BOOTSTRAP_ERROR;
}
// Initialize the main instance context.
{
main_instance =
NodeMainInstance::Create(isolate,
uv_default_loop(),
per_process::v8_platform.Platform(),
args,
exec_args);
out->isolate_data_indices =
main_instance->isolate_data()->Serialize(&creator);
Context::Scope context_scope(main_context);
HandleScope scope(isolate);
// Create the environment.
env = new Environment(main_instance->isolate_data(),
main_context,
args,
exec_args,
nullptr,
node::EnvironmentFlags::kDefaultFlags,
{});
// The default context with only things created by V8.
creator.SetDefaultContext(Context::New(isolate));
auto CreateBaseContext = [&]() {
TryCatch bootstrapCatch(isolate);
// Run the per-context scripts.
Local<Context> base_context = NewContext(isolate);
if (bootstrapCatch.HasCaught()) {
PrintCaughtException(isolate, base_context, bootstrapCatch);
abort();
// Run scripts in lib/internal/bootstrap/
if (env->RunBootstrapping().IsEmpty()) {
return BOOTSTRAP_ERROR;
}
// If --build-snapshot is true, lib/internal/main/mksnapshot.js would be
// loaded via LoadEnvironment() to execute process.argv[1] as the entry
// point (we currently only support this kind of entry point, but we
// could also explore snapshotting other kinds of execution modes
// in the future).
if (per_process::cli_options->build_snapshot) {
#if HAVE_INSPECTOR
// TODO(joyeecheung): move this before RunBootstrapping().
env->InitializeInspector({});
#endif
if (LoadEnvironment(env, StartExecutionCallback{}).IsEmpty()) {
return UNCAUGHT_EXCEPTION_ERROR;
}
// FIXME(joyeecheung): right now running the loop in the snapshot
// builder seems to introduces inconsistencies in JS land that need to
// be synchronized again after snapshot restoration.
int exit_code = SpinEventLoop(env).FromMaybe(UNCAUGHT_EXCEPTION_ERROR);
if (exit_code != 0) {
return exit_code;
}
return base_context;
};
// The Node.js-specific context with primodials, can be used by workers
// TODO(joyeecheung): investigate if this can be used by vm contexts
// without breaking compatibility.
{
size_t index = creator.AddContext(CreateBaseContext());
CHECK_EQ(index, SnapshotData::kNodeBaseContextIndex);
}
// The main instance context.
{
Local<Context> main_context = CreateBaseContext();
Context::Scope context_scope(main_context);
TryCatch bootstrapCatch(isolate);
if (per_process::enabled_debug_list.enabled(DebugCategory::MKSNAPSHOT)) {
env->PrintAllBaseObjects();
printf("Environment = %p\n", env);
}
// Create the environment.
env = new Environment(main_instance->isolate_data(),
main_context,
args,
exec_args,
nullptr,
node::EnvironmentFlags::kDefaultFlags,
{});
// Run scripts in lib/internal/bootstrap/
MaybeLocal<Value> result = env->RunBootstrapping();
if (bootstrapCatch.HasCaught()) {
// TODO(joyeecheung): fail by exiting with a non-zero exit code.
PrintCaughtException(isolate, main_context, bootstrapCatch);
abort();
}
result.ToLocalChecked();
// If --build-snapshot is true, lib/internal/main/mksnapshot.js would be
// loaded via LoadEnvironment() to execute process.argv[1] as the entry
// point (we currently only support this kind of entry point, but we
// could also explore snapshotting other kinds of execution modes
// in the future).
if (per_process::cli_options->build_snapshot) {
#if HAVE_INSPECTOR
env->InitializeInspector({});
#endif
// TODO(joyeecheung): we could use the result for something special,
// like setting up initializers that should be invoked at snapshot
// dehydration.
MaybeLocal<Value> result =
LoadEnvironment(env, StartExecutionCallback{});
if (bootstrapCatch.HasCaught()) {
// TODO(joyeecheung): fail by exiting with a non-zero exit code.
PrintCaughtException(isolate, main_context, bootstrapCatch);
abort();
}
result.ToLocalChecked();
// FIXME(joyeecheung): right now running the loop in the snapshot
// builder seems to introduces inconsistencies in JS land that need to
// be synchronized again after snapshot restoration.
int exit_code = SpinEventLoop(env).FromMaybe(1);
CHECK_EQ(exit_code, 0);
if (bootstrapCatch.HasCaught()) {
// TODO(joyeecheung): fail by exiting with a non-zero exit code.
PrintCaughtException(isolate, main_context, bootstrapCatch);
abort();
}
}
if (per_process::enabled_debug_list.enabled(
DebugCategory::MKSNAPSHOT)) {
env->PrintAllBaseObjects();
printf("Environment = %p\n", env);
}
// Serialize the native states
out->env_info = env->Serialize(&creator);
// Serialize the context
size_t index = creator.AddContext(
main_context, {SerializeNodeContextInternalFields, env});
CHECK_EQ(index, SnapshotData::kNodeMainContextIndex);
// Serialize the native states
out->env_info = env->Serialize(&creator);
#ifdef NODE_USE_NODE_CODE_CACHE
// Regenerate all the code cache.
CHECK(native_module::NativeModuleEnv::CompileAllModules(main_context));
native_module::NativeModuleEnv::CopyCodeCache(&(out->code_cache));
for (const auto& item : out->code_cache) {
std::string size_str = FormatSize(item.data.size());
per_process::Debug(DebugCategory::MKSNAPSHOT,
"Generated code cache for %d: %s\n",
item.id.c_str(),
size_str.c_str());
}
#endif
// Regenerate all the code cache.
if (!native_module::NativeModuleEnv::CompileAllModules(main_context)) {
return UNCAUGHT_EXCEPTION_ERROR;
}
native_module::NativeModuleEnv::CopyCodeCache(&(out->code_cache));
for (const auto& item : out->code_cache) {
std::string size_str = FormatSize(item.data.size());
per_process::Debug(DebugCategory::MKSNAPSHOT,
"Generated code cache for %d: %s\n",
item.id.c_str(),
size_str.c_str());
}
#endif
}
// Must be out of HandleScope
out->v8_snapshot_blob_data =
creator.CreateBlob(SnapshotCreator::FunctionCodeHandling::kClear);
// We must be able to rehash the blob when we restore it or otherwise
// the hash seed would be fixed by V8, introducing a vulnerability.
CHECK(out->v8_snapshot_blob_data.CanBeRehashed());
// We cannot resurrect the handles from the snapshot, so make sure that
// no handles are left open in the environment after the blob is created
// (which should trigger a GC and close all handles that can be closed).
if (!env->req_wrap_queue()->IsEmpty()
|| !env->handle_wrap_queue()->IsEmpty()
|| per_process::enabled_debug_list.enabled(DebugCategory::MKSNAPSHOT)) {
PrintLibuvHandleInformation(env->event_loop(), stderr);
}
CHECK(env->req_wrap_queue()->IsEmpty());
CHECK(env->handle_wrap_queue()->IsEmpty());
// Must be done while the snapshot creator isolate is entered i.e. the
// creator is still alive.
FreeEnvironment(env);
main_instance->Dispose();
// Global handles to the contexts can't be disposed before the
// blob is created. So initialize all the contexts before adding them.
// TODO(joyeecheung): figure out how to remove this restriction.
creator.SetDefaultContext(default_context);
size_t index = creator.AddContext(base_context);
CHECK_EQ(index, SnapshotData::kNodeBaseContextIndex);
index = creator.AddContext(main_context,
{SerializeNodeContextInternalFields, env});
CHECK_EQ(index, SnapshotData::kNodeMainContextIndex);
}
per_process::v8_platform.Platform()->UnregisterIsolate(isolate);
// Must be out of HandleScope
out->v8_snapshot_blob_data =
creator.CreateBlob(SnapshotCreator::FunctionCodeHandling::kClear);
// We must be able to rehash the blob when we restore it or otherwise
// the hash seed would be fixed by V8, introducing a vulnerability.
if (!out->v8_snapshot_blob_data.CanBeRehashed()) {
return SNAPSHOT_ERROR;
}
// We cannot resurrect the handles from the snapshot, so make sure that
// no handles are left open in the environment after the blob is created
// (which should trigger a GC and close all handles that can be closed).
bool queues_are_empty =
env->req_wrap_queue()->IsEmpty() && env->handle_wrap_queue()->IsEmpty();
if (!queues_are_empty ||
per_process::enabled_debug_list.enabled(DebugCategory::MKSNAPSHOT)) {
PrintLibuvHandleInformation(env->event_loop(), stderr);
}
if (!queues_are_empty) {
return SNAPSHOT_ERROR;
}
return 0;
}
std::string SnapshotBuilder::Generate(
const std::vector<std::string> args,
const std::vector<std::string> exec_args) {
int SnapshotBuilder::Generate(std::ostream& out,
const std::vector<std::string> args,
const std::vector<std::string> exec_args) {
SnapshotData data;
Generate(&data, args, exec_args);
std::string result = FormatBlob(&data);
delete[] data.v8_snapshot_blob_data.data;
return result;
int exit_code = Generate(&data, args, exec_args);
if (exit_code != 0) {
return exit_code;
}
FormatBlob(out, &data);
return exit_code;
}
SnapshotableObject::SnapshotableObject(Environment* env,

1
test/fixtures/snapshot/error.js vendored Normal file
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@ -0,0 +1 @@
throw new Error('test');

17
tools/snapshot/node_mksnapshot.cc
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@ -83,17 +83,18 @@ int BuildSnapshot(int argc, char* argv[]) {
return 1;
}
int exit_code = 0;
{
std::string snapshot =
node::SnapshotBuilder::Generate(result.args, result.exec_args);
out << snapshot;
if (!out) {
std::cerr << "Failed to write " << out_path << "\n";
return 1;
exit_code =
node::SnapshotBuilder::Generate(out, result.args, result.exec_args);
if (exit_code == 0) {
if (!out) {
std::cerr << "Failed to write " << out_path << "\n";
exit_code = 1;
}
}
}
node::TearDownOncePerProcess();
return 0;
return exit_code;
}