bool FileMapInfo::validate_header() {
bool status = _header->validate();
if (status) {
if (!ClassLoader::check_shared_paths_misc_info(_paths_misc_info, _header->_paths_misc_info_size)) {
if (!PrintSharedArchiveAndExit) {
fail_continue("shared class paths mismatch (hint: enable -XX:+TraceClassPaths to diagnose the failure)");
status = false;
}
}
}
if (_paths_misc_info != NULL) {
FREE_C_HEAP_ARRAY(char, _paths_misc_info);
_paths_misc_info = NULL;
}
return status;
}
// Map the whole region at once, assumed to be allocated contiguously.
ReservedSpace FileMapInfo::reserve_shared_memory() {
struct FileMapInfo::FileMapHeader::space_info* si = &_header->_space[0];
char* requested_addr = si->_base;
size_t size = FileMapInfo::shared_spaces_size();
// Reserve the space first, then map otherwise map will go right over some
// other reserved memory (like the code cache).
ReservedSpace rs(size, os::vm_allocation_granularity(), false, requested_addr);
if (!rs.is_reserved()) {
fail_continue("Unable to reserve shared space at required address " INTPTR_FORMAT, requested_addr);
return rs;
}
// the reserved virtual memory is for mapping class data sharing archive
MemTracker::record_virtual_memory_type((address)rs.base(), mtClassShared);
return rs;
}
bool FileMapInfo::verify_region_checksum(int i) {
if (!VerifySharedSpaces) {
return true;
}
size_t sz = _header->_space[i]._used;
if (sz == 0) {
return true; // no data
}
if (MetaspaceShared::is_string_region(i) && StringTable::shared_string_ignored()) {
return true; // shared string data are not mapped
}
const char* buf = _header->region_addr(i);
int crc = ClassLoader::crc32(0, buf, (jint)sz);
if (crc != _header->_space[i]._crc) {
fail_continue("Checksum verification failed.");
return false;
}
return true;
}
char* FileMapInfo::map_region(int i) {
struct FileMapInfo::FileMapHeader::space_info* si = &_header->_space[i];
size_t used = si->_used;
size_t alignment = os::vm_allocation_granularity();
size_t size = align_size_up(used, alignment);
char *requested_addr = si->_base;
// map the contents of the CDS archive in this memory
char *base = os::map_memory(_fd, _full_path, si->_file_offset,
requested_addr, size, si->_read_only,
si->_allow_exec);
if (base == NULL || base != si->_base) {
fail_continue(err_msg("Unable to map %s shared space at required address.", shared_region_name[i]));
return NULL;
}
#ifdef _WINDOWS
// This call is Windows-only because the memory_type gets recorded for the other platforms
// in method FileMapInfo::reserve_shared_memory(), which is not called on Windows.
MemTracker::record_virtual_memory_type((address)base, mtClassShared);
#endif
return base;
}
// Open the shared archive file, read and validate the header
// information (version, boot classpath, etc.). If initialization
// fails, shared spaces are disabled and the file is closed. [See
// fail_continue.]
//
// Validation of the archive is done in two steps:
//
// [1] validate_header() - done here. This checks the header, including _paths_misc_info.
// [2] validate_classpath_entry_table - this is done later, because the table is in the RW
// region of the archive, which is not mapped yet.
bool FileMapInfo::initialize() {
assert(UseSharedSpaces, "UseSharedSpaces expected.");
if (JvmtiExport::can_modify_any_class() || JvmtiExport::can_walk_any_space()) {
fail_continue("Tool agent requires sharing to be disabled.");
return false;
}
if (!open_for_read()) {
return false;
}
init_from_file(_fd);
if (!validate_header()) {
return false;
}
SharedReadOnlySize = _header->_space[0]._capacity;
SharedReadWriteSize = _header->_space[1]._capacity;
SharedMiscDataSize = _header->_space[2]._capacity;
SharedMiscCodeSize = _header->_space[3]._capacity;
return true;
}
/**
* 检查jar包是否可共享
*/
bool FileMapInfo::validate() {
if (_header._version != current_version()) {
fail_continue("The shared archive file is the wrong version.");
return false;
}
if (_header._magic != (int)0xf00baba2) {
fail_continue("The shared archive file has a bad magic number.");
return false;
}
if (strncmp(_header._jvm_ident, VM_Version::internal_vm_info_string(),
JVM_IDENT_MAX-1) != 0) {
fail_continue("The shared archive file was created by a different"
" version or build of HotSpot.");
return false;
}
// Cannot verify interpreter yet, as it can only be created after the GC
// heap has been initialized.
if (_header._num_jars >= JVM_SHARED_JARS_MAX) {
fail_continue("Too many jar files to share.");
return false;
}
// Build checks on classpath and jar files
int num_jars_now = 0;
ClassPathEntry *cpe = ClassLoader::classpath_entry(0);
for ( ; cpe != NULL; cpe = cpe->next()) {
if (cpe->is_jar_file()) { //jar包文件
if (num_jars_now < _header._num_jars) {
// Jar file - verify timestamp and file size.
struct stat st;
const char *path = cpe->name();
if (os::stat(path, &st) != 0) {
fail_continue("Unable to open jar file %s.", path);
return false;
}
//jar包已被修改,不能共享
if (_header._jar[num_jars_now]._timestamp != st.st_mtime ||
_header._jar[num_jars_now]._filesize != st.st_size) {
fail_continue("A jar file is not the one used while building"
" the shared archive file.");
return false;
}
}
++num_jars_now;
} else {
// If directories appear in boot classpath, they must be empty to
// avoid having to verify each individual class file.
const char* name = ((ClassPathDirEntry*)cpe)->name();
if (!os::dir_is_empty(name)) { //类路径
fail_continue("Boot classpath directory %s is not empty.", name);
return false;
}
}
}
if (num_jars_now < _header._num_jars) {
fail_continue("The number of jar files in the boot classpath is"
" less than the number the shared archive was created with.");
return false;
}
return true;
}
bool FileMapInfo::map_string_regions() {
#if INCLUDE_ALL_GCS
if (UseG1GC && UseCompressedOops && UseCompressedClassPointers) {
// Check that all the narrow oop and klass encodings match the archive
if (narrow_oop_mode() != Universe::narrow_oop_mode() ||
narrow_oop_shift() != Universe::narrow_oop_shift() ||
narrow_klass_base() != Universe::narrow_klass_base() ||
narrow_klass_shift() != Universe::narrow_klass_shift()) {
if (PrintSharedSpaces && _header->_space[MetaspaceShared::first_string]._used > 0) {
tty->print_cr("Shared string data from the CDS archive is being ignored. "
"The current CompressedOops/CompressedClassPointers encoding differs from "
"that archived due to heap size change. The archive was dumped using max heap "
"size %dM.", max_heap_size()/M);
}
} else {
string_ranges = new MemRegion[MetaspaceShared::max_strings];
struct FileMapInfo::FileMapHeader::space_info* si;
for (int i = MetaspaceShared::first_string;
i < MetaspaceShared::first_string + MetaspaceShared::max_strings; i++) {
si = &_header->_space[i];
size_t used = si->_used;
if (used > 0) {
size_t size = used;
char* requested_addr = (char*)((void*)oopDesc::decode_heap_oop_not_null(
(narrowOop)si->_addr._offset));
string_ranges[num_ranges] = MemRegion((HeapWord*)requested_addr, size / HeapWordSize);
num_ranges ++;
}
}
if (num_ranges == 0) {
StringTable::ignore_shared_strings(true);
return true; // no shared string data
}
// Check that ranges are within the java heap
if (!G1CollectedHeap::heap()->check_archive_addresses(string_ranges, num_ranges)) {
fail_continue("Unable to allocate shared string space: range is not "
"within java heap.");
return false;
}
// allocate from java heap
if (!G1CollectedHeap::heap()->alloc_archive_regions(string_ranges, num_ranges)) {
fail_continue("Unable to allocate shared string space: range is "
"already in use.");
return false;
}
// Map the string data. No need to call MemTracker::record_virtual_memory_type()
// for mapped string regions as they are part of the reserved java heap, which
// is already recorded.
for (int i = 0; i < num_ranges; i++) {
si = &_header->_space[MetaspaceShared::first_string + i];
char* addr = (char*)string_ranges[i].start();
char* base = os::map_memory(_fd, _full_path, si->_file_offset,
addr, string_ranges[i].byte_size(), si->_read_only,
si->_allow_exec);
if (base == NULL || base != addr) {
fail_continue("Unable to map shared string space at required address.");
return false;
}
}
if (!verify_string_regions()) {
fail_continue("Shared string regions are corrupt");
return false;
}
// the shared string data is mapped successfully
return true;
}
} else {
if (PrintSharedSpaces && _header->_space[MetaspaceShared::first_string]._used > 0) {
tty->print_cr("Shared string data from the CDS archive is being ignored. UseG1GC, "
"UseCompressedOops and UseCompressedClassPointers are required.");
}
}
// if we get here, the shared string data is not mapped
assert(string_ranges == NULL && num_ranges == 0, "sanity");
StringTable::ignore_shared_strings(true);
#endif
return true;
}
