jdk-24/hotspot/src/share/vm/memory/filemap.hpp

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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#ifndef SHARE_VM_MEMORY_FILEMAP_HPP
#define SHARE_VM_MEMORY_FILEMAP_HPP

#include "memory/metaspaceShared.hpp"

// Layout of the file:
//  header: dump of archive instance plus versioning info, datestamp, etc.
//   [magic # = 0xF00BABA2]
//  ... padding to align on page-boundary
//  read-write space from CompactingPermGenGen
//  read-only space from CompactingPermGenGen
//  misc data (block offset table, string table, symbols, dictionary, etc.)
//  tag(666)

static const int JVM_SHARED_JARS_MAX = 128;
static const int JVM_SPACENAME_MAX = 128;
static const int JVM_IDENT_MAX = 256;
static const int JVM_ARCH_MAX = 12;


class Metaspace;

class FileMapInfo : public CHeapObj<mtInternal> {
private:
  enum {
    _invalid_version = -1,
    _current_version = 1
  };

  bool  _file_open;
  int   _fd;
  long  _file_offset;

  // FileMapHeader describes the shared space data in the file to be
  // mapped.  This structure gets written to a file.  It is not a class, so
  // that the compilers don't add any compiler-private data to it.

  struct FileMapHeader {
    int    _magic;                    // identify file type.
    int    _version;                  // (from enum, above.)
    size_t _alignment;                // how shared archive should be aligned
    int    _obj_alignment;            // value of ObjectAlignmentInBytes

    struct space_info {
      int    _file_offset;   // sizeof(this) rounded to vm page size
      char*  _base;          // copy-on-write base address
      size_t _capacity;      // for validity checking
      size_t _used;          // for setting space top on read
      bool   _read_only;     // read only space?
      bool   _allow_exec;    // executable code in space?
    } _space[MetaspaceShared::n_regions];

    // The following fields are all sanity checks for whether this archive
    // will function correctly with this JVM and the bootclasspath it's
    // invoked with.
    char  _arch[JVM_ARCH_MAX];            // architecture
    char  _jvm_ident[JVM_IDENT_MAX];      // identifier for jvm
    int   _num_jars;              // Number of jars in bootclasspath

    // Per jar file data:  timestamp, size.

    struct {
      time_t _timestamp;          // jar timestamp.
      long   _filesize;           // jar file size.
    } _jar[JVM_SHARED_JARS_MAX];
  } _header;
  const char* _full_path;

  static FileMapInfo* _current_info;

  bool  init_from_file(int fd);
  void  align_file_position();

public:
  FileMapInfo() {
    _file_offset = 0;
    _file_open = false;
    _header._version = _invalid_version;
  }

  static int current_version()        { return _current_version; }
  void   populate_header(size_t alignment);
  bool   validate();
  void   invalidate();
  int    version()                    { return _header._version; }
  size_t alignment()                  { return _header._alignment; }
  size_t space_capacity(int i)        { return _header._space[i]._capacity; }
  char*  region_base(int i)           { return _header._space[i]._base; }
  struct FileMapHeader* header()      { return &_header; }

  static void set_current_info(FileMapInfo* info) {
    CDS_ONLY(_current_info = info;)
  }

  static FileMapInfo* current_info() {
    CDS_ONLY(return _current_info;)
    NOT_CDS(return NULL;)
  }

  static void assert_mark(bool check);

  // File manipulation.
  bool  initialize() NOT_CDS_RETURN_(false);
  bool  open_for_read();
  void  open_for_write();
  void  write_header();
  void  write_space(int i, Metaspace* space, bool read_only);
  void  write_region(int region, char* base, size_t size,
                     size_t capacity, bool read_only, bool allow_exec);
  void  write_bytes(const void* buffer, int count);
  void  write_bytes_aligned(const void* buffer, int count);
  char* map_region(int i);
  void  unmap_region(int i);
  void  close();
  bool  is_open() { return _file_open; }
  ReservedSpace reserve_shared_memory();

  // JVM/TI RedefineClasses() support:
  // Remap the shared readonly space to shared readwrite, private.
  bool  remap_shared_readonly_as_readwrite();

  // Errors.
  static void fail_stop(const char *msg, ...);
  void fail_continue(const char *msg, ...);

  // Return true if given address is in the mapped shared space.
  bool is_in_shared_space(const void* p) NOT_CDS_RETURN_(false);
};

#endif // SHARE_VM_MEMORY_FILEMAP_HPP