openjdk17 hotspot JVM解析class文件
##openjdk17 hotspot JVM解析class文件ClassFileParser::parse_stream 解析字节码
void ClassFileParser::parse_stream(const ClassFileStream* const stream,
TRAPS) {
assert(stream != NULL, "invariant");
assert(_class_name != NULL, "invariant");
// BEGIN STREAM PARSING
stream->guarantee_more(8, CHECK);// magic, major, minor
// Magic value
const u4 magic = stream->get_u4_fast();
guarantee_property(magic == JAVA_CLASSFILE_MAGIC,
"Incompatible magic value %u in class file %s",
magic, CHECK);
// Version numbers
_minor_version = stream->get_u2_fast();
_major_version = stream->get_u2_fast();
// Check version numbers - we check this even with verifier off
verify_class_version(_major_version, _minor_version, _class_name, CHECK);
stream->guarantee_more(3, CHECK); // length, first cp tag
u2 cp_size = stream->get_u2_fast();
guarantee_property(
cp_size >= 1, "Illegal constant pool size %u in class file %s",
cp_size, CHECK);
_orig_cp_size = cp_size;
if (is_hidden()) { // Add a slot for hidden class name.
cp_size++;
}
_cp = ConstantPool::allocate(_loader_data,
cp_size,
CHECK);
ConstantPool* const cp = _cp;
parse_constant_pool(stream, cp, _orig_cp_size, CHECK);
assert(cp_size == (const u2)cp->length(), "invariant");
// ACCESS FLAGS
stream->guarantee_more(8, CHECK);// flags, this_class, super_class, infs_len
// Access flags
jint flags;
// JVM_ACC_MODULE is defined in JDK-9 and later.
if (_major_version >= JAVA_9_VERSION) {
flags = stream->get_u2_fast() & (JVM_RECOGNIZED_CLASS_MODIFIERS | JVM_ACC_MODULE);
} else {
flags = stream->get_u2_fast() & JVM_RECOGNIZED_CLASS_MODIFIERS;
}
if ((flags & JVM_ACC_INTERFACE) && _major_version < JAVA_6_VERSION) {
// Set abstract bit for old class files for backward compatibility
flags |= JVM_ACC_ABSTRACT;
}
verify_legal_class_modifiers(flags, CHECK);
short bad_constant = class_bad_constant_seen();
if (bad_constant != 0) {
// Do not throw CFE until after the access_flags are checked because if
// ACC_MODULE is set in the access flags, then NCDFE must be thrown, not CFE.
classfile_parse_error("Unknown constant tag %u in class file %s", bad_constant, THREAD);
return;
}
_access_flags.set_flags(flags);
// This class and superclass
_this_class_index = stream->get_u2_fast();
check_property(
valid_cp_range(_this_class_index, cp_size) &&
cp->tag_at(_this_class_index).is_unresolved_klass(),
"Invalid this class index %u in constant pool in class file %s",
_this_class_index, CHECK);
Symbol* const class_name_in_cp = cp->klass_name_at(_this_class_index);
assert(class_name_in_cp != NULL, "class_name can't be null");
// Don't need to check whether this class name is legal or not.
// It has been checked when constant pool is parsed.
// However, make sure it is not an array type.
if (_need_verify) {
guarantee_property(class_name_in_cp->char_at(0) != JVM_SIGNATURE_ARRAY,
"Bad class name in class file %s",
CHECK);
}
#ifdef ASSERT
// Basic sanity checks
if (_is_hidden) {
assert(_class_name != vmSymbols::unknown_class_name(), "hidden classes should have a special name");
}
#endif
// Update the _class_name as needed depending on whether this is a named, un-named, or hidden class.
if (_is_hidden) {
assert(_class_name != NULL, "Unexpected null _class_name");
#ifdef ASSERT
if (_need_verify) {
verify_legal_class_name(_class_name, CHECK);
}
#endif
} else {
// Check if name in class file matches given name
if (_class_name != class_name_in_cp) {
if (_class_name != vmSymbols::unknown_class_name()) {
ResourceMark rm(THREAD);
Exceptions::fthrow(THREAD_AND_LOCATION,
vmSymbols::java_lang_NoClassDefFoundError(),
"%s (wrong name: %s)",
class_name_in_cp->as_C_string(),
_class_name->as_C_string()
);
return;
} else {
// The class name was not known by the caller so we set it from
// the value in the CP.
update_class_name(class_name_in_cp);
}
// else nothing to do: the expected class name matches what is in the CP
}
}
// Verification prevents us from creating names with dots in them, this
// asserts that that's the case.
assert(is_internal_format(_class_name), "external class name format used internally");
if (!is_internal()) {
LogTarget(Debug, class, preorder) lt;
if (lt.is_enabled()){
ResourceMark rm(THREAD);
LogStream ls(lt);
ls.print("%s", _class_name->as_klass_external_name());
if (stream->source() != NULL) {
ls.print(" source: %s", stream->source());
}
ls.cr();
}
}
// SUPERKLASS
_super_class_index = stream->get_u2_fast();
_super_klass = parse_super_class(cp,
_super_class_index,
_need_verify,
CHECK);
// Interfaces
_itfs_len = stream->get_u2_fast();
parse_interfaces(stream,
_itfs_len,
cp,
&_has_nonstatic_concrete_methods,
CHECK);
assert(_local_interfaces != NULL, "invariant");
// Fields (offsets are filled in later)
_fac = new FieldAllocationCount();
parse_fields(stream,
_access_flags.is_interface(),
_fac,
cp,
cp_size,
&_java_fields_count,
CHECK);
assert(_fields != NULL, "invariant");
// Methods
AccessFlags promoted_flags;
parse_methods(stream,
_access_flags.is_interface(),
&promoted_flags,
&_has_final_method,
&_declares_nonstatic_concrete_methods,
CHECK);
assert(_methods != NULL, "invariant");
// promote flags from parse_methods() to the klass' flags
_access_flags.add_promoted_flags(promoted_flags.as_int());
if (_declares_nonstatic_concrete_methods) {
_has_nonstatic_concrete_methods = true;
}
// Additional attributes/annotations
_parsed_annotations = new ClassAnnotationCollector();
parse_classfile_attributes(stream, cp, _parsed_annotations, CHECK);
assert(_inner_classes != NULL, "invariant");
// Finalize the Annotations metadata object,
// now that all annotation arrays have been created.
create_combined_annotations(CHECK);
// Make sure this is the end of class file stream
guarantee_property(stream->at_eos(),
"Extra bytes at the end of class file %s",
CHECK);
// all bytes in stream read and parsed
} ##解析方法
parse_methods(stream,
_access_flags.is_interface(),
&promoted_flags,
&_has_final_method,
&_declares_nonstatic_concrete_methods,
CHECK);
void ClassFileParser::parse_methods(const ClassFileStream* const cfs,
bool is_interface,
AccessFlags* promoted_flags,
bool* has_final_method,
bool* declares_nonstatic_concrete_methods,
TRAPS) {
assert(cfs != NULL, "invariant");
assert(promoted_flags != NULL, "invariant");
assert(has_final_method != NULL, "invariant");
assert(declares_nonstatic_concrete_methods != NULL, "invariant");
assert(NULL == _methods, "invariant");
cfs->guarantee_more(2, CHECK);// length
const u2 length = cfs->get_u2_fast();
if (length == 0) {
_methods = Universe::the_empty_method_array();
} else {
_methods = MetadataFactory::new_array<Method*>(_loader_data,
length,
NULL,
CHECK);
for (int index = 0; index < length; index++) {
Method* method = parse_method(cfs,
is_interface,
_cp,
promoted_flags,
CHECK);
if (method->is_final()) {
*has_final_method = true;
}
// declares_nonstatic_concrete_methods: declares concrete instance methods, any access flags
// used for interface initialization, and default method inheritance analysis
if (is_interface && !(*declares_nonstatic_concrete_methods)
&& !method->is_abstract() && !method->is_static()) {
*declares_nonstatic_concrete_methods = true;
}
_methods->at_put(index, method);
}
if (_need_verify && length > 1) {
// Check duplicated methods
ResourceMark rm(THREAD);
NameSigHash** names_and_sigs = NEW_RESOURCE_ARRAY_IN_THREAD(
THREAD, NameSigHash*, HASH_ROW_SIZE);
initialize_hashtable(names_and_sigs);
bool dup = false;
const Symbol* name = NULL;
const Symbol* sig = NULL;
{
debug_only(NoSafepointVerifier nsv;)
for (int i = 0; i < length; i++) {
const Method* const m = _methods->at(i);
name = m->name();
sig = m->signature();
// If no duplicates, add name/signature in hashtable names_and_sigs.
if (!put_after_lookup(name, sig, names_and_sigs)) {
dup = true;
break;
}
}
}
if (dup) {
classfile_parse_error("Duplicate method name \"%s\" with signature \"%s\" in class file %s",
name->as_C_string(), sig->as_klass_external_name(), THREAD);
}
}
}
}
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