Quelle relocInfo.hpp Sprache: C

/*
* Copyright (c) 1997, 2022, Oracle and/or its affiliates. All rights reserved.
* 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.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/

#ifndef SHARE_CODE_RELOCINFO_HPP
#define SHARE_CODE_RELOCINFO_HPP

#include "memory/allocation.hpp"
#include "oops/oopsHierarchy.hpp"
#include "runtime/osInfo.hpp"
#include "utilities/macros.hpp"
#include "utilities/globalDefinitions.hpp"

class nmethod;
class CodeBlob;
class CompiledMethod;
class Metadata;
class NativeMovConstReg;

// Types in this file:
//    relocInfo
//      One element of an array of halfwords encoding compressed relocations.
//      Also, the source of relocation types (relocInfo::oop_type, ...).
//    Relocation
//      A flyweight object representing a single relocation.
//      It is fully unpacked from the compressed relocation array.
//    metadata_Relocation, ... (subclasses of Relocation)
//      The location of some type-specific operations (metadata_addr, ...).
//      Also, the source of relocation specs (metadata_Relocation::spec, ...).
//    oop_Relocation, ... (subclasses of Relocation)
//      oops in the code stream (strings, class loaders)
//      Also, the source of relocation specs (oop_Relocation::spec, ...).
//    RelocationHolder
//      A value type which acts as a union holding a Relocation object.
//      Represents a relocation spec passed into a CodeBuffer during assembly.
//    RelocIterator
//      A StackObj which iterates over the relocations associated with
//      a range of code addresses.  Can be used to operate a copy of code.

// Notes on relocType:
//
// These hold enough information to read or write a value embedded in
// the instructions of an CodeBlob.  They're used to update:
//
//   1) embedded oops     (isOop()          == true)
//   2) inline caches     (isIC()           == true)
//   3) runtime calls     (isRuntimeCall()  == true)
//   4) internal word ref (isInternalWord() == true)
//   5) external word ref (isExternalWord() == true)
//
// when objects move (GC) or if code moves (compacting the code heap).
// They are also used to patch the code (if a call site must change)
//
// A relocInfo is represented in 16 bits:
//   4 bits indicating the relocation type
//  12 bits indicating the offset from the previous relocInfo address
//
// The offsets accumulate along the relocInfo stream to encode the
// address within the CodeBlob, which is named RelocIterator::addr().
// The address of a particular relocInfo always points to the first
// byte of the relevant instruction (and not to any of its subfields
// or embedded immediate constants).
//
// The offset value is scaled appropriately for the target machine.
// (See relocInfo_<arch>.hpp for the offset scaling.)
//
// On some machines, there may also be a "format" field which may provide
// additional information about the format of the instruction stream
// at the corresponding code address.  The format value is usually zero.
// Any machine (such as Intel) whose instructions can sometimes contain
// more than one relocatable constant needs format codes to distinguish
// which operand goes with a given relocation.
//
// If the target machine needs N format bits, the offset has 12-N bits,
// the format is encoded between the offset and the type, and the
// relocInfo_<arch>.hpp file has manifest constants for the format codes.
//
// If the type is "data_prefix_tag" then the offset bits are further encoded,
// and in fact represent not a code-stream offset but some inline data.
// The data takes the form of a counted sequence of halfwords, which
// precedes the actual relocation record.  (Clients never see it directly.)
// The interpretation of this extra data depends on the relocation type.
//
// On machines that have 32-bit immediate fields, there is usually
// little need for relocation "prefix" data, because the instruction stream
// is a perfectly reasonable place to store the value.  On machines in
// which 32-bit values must be "split" across instructions, the relocation
// data is the "true" specification of the value, which is then applied
// to some field of the instruction (22 or 13 bits, on SPARC).
//
// Whenever the location of the CodeBlob changes, any PC-relative
// relocations, and any internal_word_type relocations, must be reapplied.
// After the GC runs, oop_type relocations must be reapplied.
//
//
// Here are meanings of the types:
//
// relocInfo::none -- a filler record
//   Value:  none
//   Instruction: The corresponding code address is ignored
//   Data:  Any data prefix and format code are ignored
//   (This means that any relocInfo can be disabled by setting
//   its type to none.  See relocInfo::remove.)
//
// relocInfo::oop_type, relocInfo::metadata_type -- a reference to an oop or meta data
//   Value:  an oop, or else the address (handle) of an oop
//   Instruction types: memory (load), set (load address)
//   Data:  []       an oop stored in 4 bytes of instruction
//          [n]      n is the index of an oop in the CodeBlob's oop pool
//          [[N]n l] and l is a byte offset to be applied to the oop
//          [Nn Ll]  both index and offset may be 32 bits if necessary
//   Here is a special hack, used only by the old compiler:
//          [[N]n 00] the value is the __address__ of the nth oop in the pool
//   (Note that the offset allows optimal references to class variables.)
//
// relocInfo::internal_word_type -- an address within the same CodeBlob
// relocInfo::section_word_type -- same, but can refer to another section
//   Value:  an address in the CodeBlob's code or constants section
//   Instruction types: memory (load), set (load address)
//   Data:  []     stored in 4 bytes of instruction
//          [[L]l] a relative offset (see [About Offsets] below)
//   In the case of section_word_type, the offset is relative to a section
//   base address, and the section number (e.g., SECT_INSTS) is encoded
//   into the low two bits of the offset L.
//
// relocInfo::external_word_type -- a fixed address in the runtime system
//   Value:  an address
//   Instruction types: memory (load), set (load address)
//   Data:  []   stored in 4 bytes of instruction
//          [n]  the index of a "well-known" stub (usual case on RISC)
//          [Ll] a 32-bit address
//
// relocInfo::runtime_call_type -- a fixed subroutine in the runtime system
//   Value:  an address
//   Instruction types: PC-relative call (or a PC-relative branch)
//   Data:  []   stored in 4 bytes of instruction
//
// relocInfo::static_call_type -- a static call
//   Value:  an CodeBlob, a stub, or a fixup routine
//   Instruction types: a call
//   Data:  []
//   The identity of the callee is extracted from debugging information.
//   //%note reloc_3
//
// relocInfo::virtual_call_type -- a virtual call site (which includes an inline
//                                 cache)
//   Value:  an CodeBlob, a stub, the interpreter, or a fixup routine
//   Instruction types: a call, plus some associated set-oop instructions
//   Data:  []       the associated set-oops are adjacent to the call
//          [n]      n is a relative offset to the first set-oop
//          [[N]n l] and l is a limit within which the set-oops occur
//          [Nn Ll]  both n and l may be 32 bits if necessary
//   The identity of the callee is extracted from debugging information.
//
// relocInfo::opt_virtual_call_type -- a virtual call site that is statically bound
//
//    Same info as a static_call_type. We use a special type, so the handling of
//    virtuals and statics are separated.
//
//
//   The offset n points to the first set-oop.  (See [About Offsets] below.)
//   In turn, the set-oop instruction specifies or contains an oop cell devoted
//   exclusively to the IC call, which can be patched along with the call.
//
//   The locations of any other set-oops are found by searching the relocation
//   information starting at the first set-oop, and continuing until all
//   relocations up through l have been inspected.  The value l is another
//   relative offset.  (Both n and l are relative to the call's first byte.)
//
//   The limit l of the search is exclusive.  However, if it points within
//   the call (e.g., offset zero), it is adjusted to point after the call and
//   any associated machine-specific delay slot.
//
//   Since the offsets could be as wide as 32-bits, these conventions
//   put no restrictions whatever upon code reorganization.
//
//   The compiler is responsible for ensuring that transition from a clean
//   state to a monomorphic compiled state is MP-safe.  This implies that
//   the system must respond well to intermediate states where a random
//   subset of the set-oops has been correctly from the clean state
//   upon entry to the VEP of the compiled method.  In the case of a
//   machine (Intel) with a single set-oop instruction, the 32-bit
//   immediate field must not straddle a unit of memory coherence.
//   //%note reloc_3
//
// relocInfo::static_stub_type -- an extra stub for each static_call_type
//   Value:  none
//   Instruction types: a virtual call:  { set_oop; jump; }
//   Data:  [[N]n]  the offset of the associated static_call reloc
//   This stub becomes the target of a static call which must be upgraded
//   to a virtual call (because the callee is interpreted).
//   See [About Offsets] below.
//   //%note reloc_2
//
// relocInfo::poll_[return_]type -- a safepoint poll
//   Value:  none
//   Instruction types: memory load or test
//   Data:  none
//
// For example:
//
//   INSTRUCTIONS                        RELOC: TYPE    PREFIX DATA
//   ------------                               ----    -----------
// sethi      %hi(myObject),  R               oop_type [n(myObject)]
// ld      [R+%lo(myObject)+fldOffset], R2    oop_type [n(myObject) fldOffset]
// add R2, 1, R2
// st  R2, [R+%lo(myObject)+fldOffset]        oop_type [n(myObject) fldOffset]
//%note reloc_1
//
// This uses 4 instruction words, 8 relocation halfwords,
// and an entry (which is shareable) in the CodeBlob's oop pool,
// for a total of 36 bytes.
//
// Note that the compiler is responsible for ensuring the "fldOffset" when
// added to "%lo(myObject)" does not overflow the immediate fields of the
// memory instructions.
//
//
// [About Offsets] Relative offsets are supplied to this module as
// positive byte offsets, but they may be internally stored scaled
// and/or negated, depending on what is most compact for the target
// system.  Since the object pointed to by the offset typically
// precedes the relocation address, it is profitable to store
// these negative offsets as positive numbers, but this decision
// is internal to the relocation information abstractions.
//

class Relocation;
class CodeBuffer;
class CodeSection;
class RelocIterator;

class relocInfo {
  friend class RelocIterator;
public:
  enum relocType {
    none                    =  0, // Used when no relocation should be generated
    oop_type                =  1, // embedded oop
    virtual_call_type       =  2, // a standard inline cache call for a virtual send
    opt_virtual_call_type   =  3, // a virtual call that has been statically bound (i.e., no IC cache)
    static_call_type        =  4, // a static send
    static_stub_type        =  5, // stub-entry for static send  (takes care of interpreter case)
    runtime_call_type       =  6, // call to fixed external routine
    external_word_type      =  7, // reference to fixed external address
    internal_word_type      =  8, // reference within the current code blob
    section_word_type       =  9, // internal, but a cross-section reference
    poll_type               = 10, // polling instruction for safepoints
    poll_return_type        = 11, // polling instruction for safepoints at return
    metadata_type           = 12, // metadata that used to be oops
    trampoline_stub_type    = 13, // stub-entry for trampoline
    runtime_call_w_cp_type  = 14, // Runtime call which may load its target from the constant pool
    data_prefix_tag         = 15, // tag for a prefix (carries data arguments)
    post_call_nop_type      = 16, // A tag for post call nop relocations
    entry_guard_type        = 17, // A tag for an nmethod entry barrier guard value
    type_mask               = 31  // A mask which selects only the above values
  };

private:
  unsigned short _value;

  static const enum class RawBitsToken {} RAW_BITS{};

  relocInfo(relocType type, RawBitsToken, int bits)
    : _value((type << nontype_width) + bits) { }

  static relocType check_relocType(relocType type) NOT_DEBUG({ return type; });

  static void check_offset_and_format(int offset, int format) NOT_DEBUG_RETURN;

  static int compute_bits(int offset, int format) {
    check_offset_and_format(offset, format);
    return (offset / offset_unit) + (format << offset_width);
  }

public:
  relocInfo(relocType type, int offset, int format = 0)
    : relocInfo(check_relocType(type), RAW_BITS, compute_bits(offset, format)) {}

  #define APPLY_TO_RELOCATIONS(visitor) \
    visitor(oop) \
    visitor(metadata) \
    visitor(virtual_call) \
    visitor(opt_virtual_call) \
    visitor(static_call) \
    visitor(static_stub) \
    visitor(runtime_call) \
    visitor(runtime_call_w_cp) \
    visitor(external_word) \
    visitor(internal_word) \
    visitor(poll) \
    visitor(poll_return) \
    visitor(section_word) \
    visitor(trampoline_stub) \
    visitor(post_call_nop) \
    visitor(entry_guard) \

public:
  enum {
    value_width             = sizeof(unsigned short) * BitsPerByte,
    type_width              = 5,   // == log2(type_mask+1)
    nontype_width           = value_width - type_width,
    datalen_width           = nontype_width-1,
    datalen_tag             = 1 << datalen_width,  // or-ed into _value
    datalen_limit           = 1 << datalen_width,
    datalen_mask            = (1 << datalen_width)-1
  };

  // accessors
public:
  relocType  type()       const { return (relocType)((unsigned)_value >> nontype_width); }
  int  format()           const { return format_mask==0? 0: format_mask &
                                         ((unsigned)_value >> offset_width); }
  int  addr_offset()      const { assert(!is_prefix(), "must have offset");
                                  return (_value & offset_mask)*offset_unit; }

protected:
  const short* data()     const { assert(is_datalen(), "must have data");
                                  return (const short*)(this + 1); }
  int          datalen()  const { assert(is_datalen(), "must have data");
                                  return (_value & datalen_mask); }
  int         immediate() const { assert(is_immediate(), "must have immed");
                                  return (_value & datalen_mask); }
public:
  static int addr_unit()        { return offset_unit; }
  static int offset_limit()     { return (1 << offset_width) * offset_unit; }

  void set_type(relocType type);

  void remove() { set_type(none); }

protected:
  bool is_none()                const { return type() == none; }
  bool is_prefix()              const { return type() == data_prefix_tag; }
  bool is_datalen()             const { assert(is_prefix(), "must be prefix");
                                        return (_value & datalen_tag) != 0; }
  bool is_immediate()           const { assert(is_prefix(), "must be prefix");
                                        return (_value & datalen_tag) == 0; }

public:
  // Occasionally records of type relocInfo::none will appear in the stream.
  // We do not bother to filter these out, but clients should ignore them.
  // These records serve as "filler" in three ways:
  //  - to skip large spans of unrelocated code (this is rare)
  //  - to pad out the relocInfo array to the required oop alignment
  //  - to disable old relocation information which is no longer applicable

  inline friend relocInfo filler_relocInfo();

  // Every non-prefix relocation may be preceded by at most one prefix,
  // which supplies 1 or more halfwords of associated data.  Conventionally,
  // an int is represented by 0, 1, or 2 halfwords, depending on how
  // many bits are required to represent the value.  (In addition,
  // if the sole halfword is a 10-bit unsigned number, it is made
  // "immediate" in the prefix header word itself.  This optimization
  // is invisible outside this module.)

  inline friend relocInfo prefix_relocInfo(int datalen);

private:
  // an immediate relocInfo optimizes a prefix with one 10-bit unsigned value
  static relocInfo immediate_relocInfo(int data0) {
    assert(fits_into_immediate(data0), "data0 in limits");
    return relocInfo(relocInfo::data_prefix_tag, RAW_BITS, data0);
  }
  static bool fits_into_immediate(int data0) {
    return (data0 >= 0 && data0 < datalen_limit);
  }

public:
  // Support routines for compilers.

  // This routine takes an infant relocInfo (unprefixed) and
  // edits in its prefix, if any.  It also updates dest.locs_end.
  void initialize(CodeSection* dest, Relocation* reloc);

  // This routine updates a prefix and returns the limit pointer.
  // It tries to compress the prefix from 32 to 16 bits, and if
  // successful returns a reduced "prefix_limit" pointer.
  relocInfo* finish_prefix(short* prefix_limit);

  // bit-packers for the data array:

  // As it happens, the bytes within the shorts are ordered natively,
  // but the shorts within the word are ordered big-endian.
  // This is an arbitrary choice, made this way mainly to ease debugging.
  static int data0_from_int(jint x)         { return x >> value_width; }
  static int data1_from_int(jint x)         { return (short)x; }
  static jint jint_from_data(short* data) {
    return (data[0] << value_width) + (unsigned short)data[1];
  }

  static jint short_data_at(int n, short* data, int datalen) {
    return datalen > n ? data[n] : 0;
  }

  static jint jint_data_at(int n, short* data, int datalen) {
    return datalen > n+1 ? jint_from_data(&data[n]) : short_data_at(n, data, datalen);
  }

  // Update methods for relocation information
  // (since code is dynamically patched, we also need to dynamically update the relocation info)
  // Both methods takes old_type, so it is able to perform sanity checks on the information removed.
  static void change_reloc_info_for_address(RelocIterator *itr, address pc, relocType old_type, relocType new_type);

  // Machine dependent stuff
#include CPU_HEADER(relocInfo)

protected:
  // Derived constant, based on format_width which is PD:
  enum {
    offset_width       = nontype_width - format_width,
    offset_mask        = (1<<offset_width) - 1,
    format_mask        = (1<<format_width) - 1
  };
public:
  enum {
#ifdef _LP64
    // for use in format
    // format_width must be at least 1 on _LP64
    narrow_oop_in_const = 1,
#endif
    // Conservatively large estimate of maximum length (in shorts)
    // of any relocation record.
    // Extended format is length prefix, data words, and tag/offset suffix.
    length_limit       = 1 + 1 + (3*BytesPerWord/BytesPerShort) + 1,
    have_format        = format_width > 0
  };
};

#define FORWARD_DECLARE_EACH_CLASS(name)              \
class name##_Relocation;
APPLY_TO_RELOCATIONS(FORWARD_DECLARE_EACH_CLASS)
#undef FORWARD_DECLARE_EACH_CLASS

inline relocInfo filler_relocInfo() {
  return relocInfo(relocInfo::none, relocInfo::offset_limit() - relocInfo::offset_unit);
}

inline relocInfo prefix_relocInfo(int datalen = 0) {
  assert(relocInfo::fits_into_immediate(datalen), "datalen in limits");
  return relocInfo(relocInfo::data_prefix_tag, relocInfo::RAW_BITS, relocInfo::datalen_tag | datalen);
}

// Holder for flyweight relocation objects.
// Although the flyweight subclasses are of varying sizes,
// the holder is "one size fits all".
class RelocationHolder {
  friend class Relocation;
  friend class CodeSection;

private:
  // this preallocated memory must accommodate all subclasses of Relocation
  // (this number is assertion-checked in Relocation::operator new)
  enum { _relocbuf_size = 5 };
  void* _relocbuf[ _relocbuf_size ];

public:
  Relocation* reloc() const { return (Relocation*) &_relocbuf[0]; }
  inline relocInfo::relocType type() const;

  // Add a constant offset to a relocation.  Helper for class Address.
  RelocationHolder plus(int offset) const;

  inline RelocationHolder();                // initializes type to none

  inline RelocationHolder(Relocation* r);   // make a copy

  static const RelocationHolder none;
};

// A RelocIterator iterates through the relocation information of a CodeBlob.
// It provides access to successive relocations as it is advanced through a
// code stream.
// Usage:
//   RelocIterator iter(nm);
//   while (iter.next()) {
//     iter.reloc()->some_operation();
//   }
// or:
//   RelocIterator iter(nm);
//   while (iter.next()) {
//     switch (iter.type()) {
//      case relocInfo::oop_type          :
//      case relocInfo::ic_type           :
//      case relocInfo::prim_type         :
//      case relocInfo::uncommon_type     :
//      case relocInfo::runtime_call_type :
//      case relocInfo::internal_word_type:
//      case relocInfo::external_word_type:
//      ...
//     }
//   }

class RelocIterator : public StackObj {
  friend class section_word_Relocation; // for section verification
  enum { SECT_LIMIT = 3 };  // must be equal to CodeBuffer::SECT_LIMIT, checked in ctor
  friend class Relocation;
  friend class relocInfo;   // for change_reloc_info_for_address only
  typedef relocInfo::relocType relocType;

private:
  address         _limit;   // stop producing relocations after this _addr
  relocInfo*      _current; // the current relocation information
  relocInfo*      _end;     // end marker; we're done iterating when _current == _end
  CompiledMethod* _code;    // compiled method containing _addr
  address         _addr;    // instruction to which the relocation applies
  short           _databuf; // spare buffer for compressed data
  short*          _data;    // pointer to the relocation's data
  short           _datalen; // number of halfwords in _data

  // Base addresses needed to compute targets of section_word_type relocs.
  address _section_start[SECT_LIMIT];
  address _section_end  [SECT_LIMIT];

  void set_has_current(bool b) {
    _datalen = !b ? -1 : 0;
    debug_only(_data = NULL);
  }
  void set_current(relocInfo& ri) {
    _current = &ri;
    set_has_current(true);
  }

  RelocationHolder _rh; // where the current relocation is allocated

  relocInfo* current() const { assert(has_current(), "must have current");
                               return _current; }

  void set_limits(address begin, address limit);

  void advance_over_prefix();    // helper method

  void initialize_misc();

  void initialize(CompiledMethod* nm, address begin, address limit);

  RelocIterator() { initialize_misc(); }

public:
  // constructor
  RelocIterator(CompiledMethod* nm, address begin = NULL, address limit = NULL);
  RelocIterator(CodeSection* cb, address begin = NULL, address limit = NULL);

  // get next reloc info, return !eos
  bool next() {
    _current++;
    assert(_current <= _end, "must not overrun relocInfo");
    if (_current == _end) {
      set_has_current(false);
      return false;
    }
    set_has_current(true);

    if (_current->is_prefix()) {
      advance_over_prefix();
      assert(!current()->is_prefix(), "only one prefix at a time");
    }

    _addr += _current->addr_offset();

    if (_limit != NULL && _addr >= _limit) {
      set_has_current(false);
      return false;
    }

    return true;
  }

  // accessors
  address      limit()        const { return _limit; }
  relocType    type()         const { return current()->type(); }
  int          format()       const { return (relocInfo::have_format) ? current()->format() : 0; }
  address      addr()         const { return _addr; }
  CompiledMethod*     code()  const { return _code; }
  short*       data()         const { return _data; }
  int          datalen()      const { return _datalen; }
  bool     has_current()      const { return _datalen >= 0; }
  bool   addr_in_const()      const;

  address section_start(int n) const {
    assert(_section_start[n], "must be initialized");
    return _section_start[n];
  }
  address section_end(int n) const {
    assert(_section_end[n], "must be initialized");
    return _section_end[n];
  }

  // The address points to the affected displacement part of the instruction.
  // For RISC, this is just the whole instruction.
  // For Intel, this is an unaligned 32-bit word.

  // type-specific relocation accessors:  oop_Relocation* oop_reloc(), etc.
  #define EACH_TYPE(name)                               \
  inline name##_Relocation* name##_reloc();
  APPLY_TO_RELOCATIONS(EACH_TYPE)
  #undef EACH_TYPE
  // generic relocation accessor; switches on type to call the above
  Relocation* reloc();

#ifndef PRODUCT
public:
  void print();
  void print_current();
#endif
};

// A Relocation is a flyweight object allocated within a RelocationHolder.
// It represents the relocation data of relocation record.
// So, the RelocIterator unpacks relocInfos into Relocations.

class Relocation {
  friend class RelocationHolder;
  friend class RelocIterator;

private:
  // When a relocation has been created by a RelocIterator,
  // this field is non-null.  It allows the relocation to know
  // its context, such as the address to which it applies.
  RelocIterator* _binding;

  relocInfo::relocType _rtype;

protected:
  RelocIterator* binding() const {
    assert(_binding != NULL, "must be bound");
    return _binding;
  }
  void set_binding(RelocIterator* b) {
    assert(_binding == NULL, "must be unbound");
    _binding = b;
    assert(_binding != NULL, "must now be bound");
  }

  Relocation(relocInfo::relocType rtype) : _binding(NULL), _rtype(rtype) { }

  static RelocationHolder newHolder() {
    return RelocationHolder();
  }

public:
  void* operator new(size_t size, const RelocationHolder& holder) throw() {
    assert(size <= sizeof(holder._relocbuf), "Make _relocbuf bigger!");
    assert((void* const *)holder.reloc() == &holder._relocbuf[0], "ptrs must agree");
    return holder.reloc();
  }

  // make a generic relocation for a given type (if possible)
  static RelocationHolder spec_simple(relocInfo::relocType rtype);

  // here is the type-specific hook which writes relocation data:
  virtual void pack_data_to(CodeSection* dest) { }

  // here is the type-specific hook which reads (unpacks) relocation data:
  virtual void unpack_data() {
    assert(datalen()==0 || type()==relocInfo::none, "no data here");
  }

protected:
  // Helper functions for pack_data_to() and unpack_data().

  // Most of the compression logic is confined here.
  // (The "immediate data" mechanism of relocInfo works independently
  // of this stuff, and acts to further compress most 1-word data prefixes.)

  // A variable-width int is encoded as a short if it will fit in 16 bits.
  // The decoder looks at datalen to decide whether to unpack short or jint.
  // Most relocation records are quite simple, containing at most two ints.

  static bool is_short(jint x) { return x == (short)x; }
  static short* add_short(short* p, int x)  { *p++ = x; return p; }
  static short* add_jint (short* p, jint x) {
    *p++ = relocInfo::data0_from_int(x); *p++ = relocInfo::data1_from_int(x);
    return p;
  }
  static short* add_var_int(short* p, jint x) {   // add a variable-width int
    if (is_short(x))  p = add_short(p, x);
    else              p = add_jint (p, x);
    return p;
  }

  static short* pack_1_int_to(short* p, jint x0) {
    // Format is one of:  [] [x] [Xx]
    if (x0 != 0)  p = add_var_int(p, x0);
    return p;
  }
  int unpack_1_int() {
    assert(datalen() <= 2, "too much data");
    return relocInfo::jint_data_at(0, data(), datalen());
  }

  // With two ints, the short form is used only if both ints are short.
  short* pack_2_ints_to(short* p, jint x0, jint x1) {
    // Format is one of:  [] [x y?] [Xx Y?y]
    if (x0 == 0 && x1 == 0) {
      // no halfwords needed to store zeroes
    } else if (is_short(x0) && is_short(x1)) {
      // 1-2 halfwords needed to store shorts
      p = add_short(p, x0); if (x1!=0) p = add_short(p, x1);
    } else {
      // 3-4 halfwords needed to store jints
      p = add_jint(p, x0);             p = add_var_int(p, x1);
    }
    return p;
  }
  void unpack_2_ints(jint& x0, jint& x1) {
    int    dlen = datalen();
    short* dp  = data();
    if (dlen <= 2) {
      x0 = relocInfo::short_data_at(0, dp, dlen);
      x1 = relocInfo::short_data_at(1, dp, dlen);
    } else {
      assert(dlen <= 4, "too much data");
      x0 = relocInfo::jint_data_at(0, dp, dlen);
      x1 = relocInfo::jint_data_at(2, dp, dlen);
    }
  }

protected:
  // platform-independent utility for patching constant section
  void       const_set_data_value    (address x);
  void       const_verify_data_value (address x);
  // platform-dependent utilities for decoding and patching instructions
  void       pd_set_data_value       (address x, intptr_t off, bool verify_only = false); // a set or mem-ref
  void       pd_verify_data_value    (address x, intptr_t off) { pd_set_data_value(x, off, true); }
  address    pd_call_destination     (address orig_addr = NULL);
  void       pd_set_call_destination (address x);

  // this extracts the address of an address in the code stream instead of the reloc data
  address* pd_address_in_code       ();

  // this extracts an address from the code stream instead of the reloc data
  address  pd_get_address_from_code ();

  // these convert from byte offsets, to scaled offsets, to addresses
  static jint scaled_offset(address x, address base) {
    int byte_offset = x - base;
    int offset = -byte_offset / relocInfo::addr_unit();
    assert(address_from_scaled_offset(offset, base) == x, "just checkin'");
    return offset;
  }
  static jint scaled_offset_null_special(address x, address base) {
    // Some relocations treat offset=0 as meaning NULL.
    // Handle this extra convention carefully.
    if (x == NULL)  return 0;
    assert(x != base, "offset must not be zero");
    return scaled_offset(x, base);
  }
  static address address_from_scaled_offset(jint offset, address base) {
    int byte_offset = -( offset * relocInfo::addr_unit() );
    return base + byte_offset;
  }

  // helpers for mapping between old and new addresses after a move or resize
  address old_addr_for(address newa, const CodeBuffer* src, CodeBuffer* dest);
  address new_addr_for(address olda, const CodeBuffer* src, CodeBuffer* dest);
  void normalize_address(address& addr, const CodeSection* dest, bool allow_other_sections = false);

public:
  // accessors which only make sense for a bound Relocation
  address         addr()            const { return binding()->addr(); }
  CompiledMethod* code()            const { return binding()->code(); }
  bool            addr_in_const()   const { return binding()->addr_in_const(); }
protected:
  short*   data()         const { return binding()->data(); }
  int      datalen()      const { return binding()->datalen(); }
  int      format()       const { return binding()->format(); }

public:
  relocInfo::relocType type()              const { return _rtype; }

  // is it a call instruction?
  virtual bool is_call()                         { return false; }

  // is it a data movement instruction?
  virtual bool is_data()                         { return false; }

  // some relocations can compute their own values
  virtual address  value();

  // all relocations are able to reassert their values
  virtual void set_value(address x);

  virtual bool clear_inline_cache()              { return true; }

  // This method assumes that all virtual/static (inline) caches are cleared (since for static_call_type and
  // ic_call_type is not always position dependent (depending on the state of the cache)). However, this is
  // probably a reasonable assumption, since empty caches simplifies code reloacation.
  virtual void fix_relocation_after_move(const CodeBuffer* src, CodeBuffer* dest) { }
};

// certain inlines must be deferred until class Relocation is defined:

inline RelocationHolder::RelocationHolder() {
  // initialize the vtbl, just to keep things type-safe
  new(*this) Relocation(relocInfo::none);
}

inline RelocationHolder::RelocationHolder(Relocation* r) {
  // wordwise copy from r (ok if it copies garbage after r)
  for (int i = 0; i < _relocbuf_size; i++) {
    _relocbuf[i] = ((void**)r)[i];
  }
}

relocInfo::relocType RelocationHolder::type() const {
  return reloc()->type();
}

// A DataRelocation always points at a memory or load-constant instruction..
// It is absolute on most machines, and the constant is split on RISCs.
// The specific subtypes are oop, external_word, and internal_word.
// By convention, the "value" does not include a separately reckoned "offset".
class DataRelocation : public Relocation {
public:
  DataRelocation(relocInfo::relocType type) : Relocation(type) {}

  bool          is_data()                      { return true; }

  // both target and offset must be computed somehow from relocation data
  virtual int    offset()                      { return 0; }
  address         value()                      = 0;
  void        set_value(address x)             { set_value(x, offset()); }
  void        set_value(address x, intptr_t o) {
    if (addr_in_const())
      const_set_data_value(x);
    else
      pd_set_data_value(x, o);
  }
  void        verify_value(address x) {
    if (addr_in_const())
      const_verify_data_value(x);
    else
      pd_verify_data_value(x, offset());
  }

  // The "o" (displacement) argument is relevant only to split relocations
  // on RISC machines.  In some CPUs (SPARC), the set-hi and set-lo ins'ns
  // can encode more than 32 bits between them.  This allows compilers to
  // share set-hi instructions between addresses that differ by a small
  // offset (e.g., different static variables in the same class).
  // On such machines, the "x" argument to set_value on all set-lo
  // instructions must be the same as the "x" argument for the
  // corresponding set-hi instructions.  The "o" arguments for the
  // set-hi instructions are ignored, and must not affect the high-half
  // immediate constant.  The "o" arguments for the set-lo instructions are
  // added into the low-half immediate constant, and must not overflow it.
};

class post_call_nop_Relocation : public Relocation {
  friend class RelocIterator;

public:
  post_call_nop_Relocation() : Relocation(relocInfo::post_call_nop_type) { }

  static RelocationHolder spec() {
    RelocationHolder rh = newHolder();
    new(rh) post_call_nop_Relocation();
    return rh;
  }
};

class entry_guard_Relocation : public Relocation {
  friend class RelocIterator;

public:
  entry_guard_Relocation() : Relocation(relocInfo::entry_guard_type) { }

  static RelocationHolder spec() {
    RelocationHolder rh = newHolder();
    new(rh) entry_guard_Relocation();
    return rh;
  }
};

// A CallRelocation always points at a call instruction.
// It is PC-relative on most machines.
class CallRelocation : public Relocation {
public:
  CallRelocation(relocInfo::relocType type) : Relocation(type) { }

  bool is_call() { return true; }

  address  destination()                    { return pd_call_destination(); }
  void     set_destination(address x); // pd_set_call_destination

  void     fix_relocation_after_move(const CodeBuffer* src, CodeBuffer* dest);
  address  value()                          { return destination();  }
  void     set_value(address x)             { set_destination(x); }
};

class oop_Relocation : public DataRelocation {
public:
  // encode in one of these formats:  [] [n] [n l] [Nn l] [Nn Ll]
  // an oop in the CodeBlob's oop pool
  static RelocationHolder spec(int oop_index, int offset = 0) {
    assert(oop_index > 0, "must be a pool-resident oop");
    RelocationHolder rh = newHolder();
    new(rh) oop_Relocation(oop_index, offset);
    return rh;
  }
  // an oop in the instruction stream
  static RelocationHolder spec_for_immediate() {
    // If no immediate oops are generated, we can skip some walks over nmethods.
    // Assert that they don't get generated accidentally!
    assert(relocInfo::mustIterateImmediateOopsInCode(),
           "Must return true so we will search for oops as roots etc. in the code.");
    const int oop_index = 0;
    const int offset    = 0;    // if you want an offset, use the oop pool
    RelocationHolder rh = newHolder();
    new(rh) oop_Relocation(oop_index, offset);
    return rh;
  }

private:
  jint _oop_index;                  // if > 0, index into CodeBlob::oop_at
  jint _offset;                     // byte offset to apply to the oop itself

  oop_Relocation(int oop_index, int offset)
    : DataRelocation(relocInfo::oop_type), _oop_index(oop_index), _offset(offset) { }

  friend class RelocIterator;
  oop_Relocation() : DataRelocation(relocInfo::oop_type) {}

public:
  int oop_index() { return _oop_index; }
  int offset()    { return _offset; }

  // data is packed in "2_ints" format:  [i o] or [Ii Oo]
  void pack_data_to(CodeSection* dest);
  void unpack_data();

  void fix_oop_relocation();        // reasserts oop value

  void verify_oop_relocation();

  address value()  { return cast_from_oop<address>(*oop_addr()); }

  bool oop_is_immediate()  { return oop_index() == 0; }

  oop* oop_addr();                  // addr or &pool[jint_data]
  oop  oop_value();                 // *oop_addr
  // Note:  oop_value transparently converts Universe::non_oop_word to NULL.
};

// copy of oop_Relocation for now but may delete stuff in both/either
class metadata_Relocation : public DataRelocation {

public:
  // encode in one of these formats:  [] [n] [n l] [Nn l] [Nn Ll]
  // an metadata in the CodeBlob's metadata pool
  static RelocationHolder spec(int metadata_index, int offset = 0) {
    assert(metadata_index > 0, "must be a pool-resident metadata");
    RelocationHolder rh = newHolder();
    new(rh) metadata_Relocation(metadata_index, offset);
    return rh;
  }
  // an metadata in the instruction stream
  static RelocationHolder spec_for_immediate() {
    const int metadata_index = 0;
    const int offset    = 0;    // if you want an offset, use the metadata pool
    RelocationHolder rh = newHolder();
    new(rh) metadata_Relocation(metadata_index, offset);
    return rh;
  }

private:
  jint _metadata_index;            // if > 0, index into nmethod::metadata_at
  jint _offset;                     // byte offset to apply to the metadata itself

  metadata_Relocation(int metadata_index, int offset)
    : DataRelocation(relocInfo::metadata_type), _metadata_index(metadata_index), _offset(offset) { }

  friend class RelocIterator;
  metadata_Relocation() : DataRelocation(relocInfo::metadata_type) { }

  // Fixes a Metadata pointer in the code. Most platforms embeds the
  // Metadata pointer in the code at compile time so this is empty
  // for them.
  void pd_fix_value(address x);

public:
  int metadata_index() { return _metadata_index; }
  int offset()    { return _offset; }

  // data is packed in "2_ints" format:  [i o] or [Ii Oo]
  void pack_data_to(CodeSection* dest);
  void unpack_data();

  void fix_metadata_relocation();        // reasserts metadata value

  address value()  { return (address) *metadata_addr(); }

  bool metadata_is_immediate()  { return metadata_index() == 0; }

  Metadata**   metadata_addr();                  // addr or &pool[jint_data]
  Metadata*    metadata_value();                 // *metadata_addr
  // Note:  metadata_value transparently converts Universe::non_metadata_word to NULL.
};

class virtual_call_Relocation : public CallRelocation {

public:
  // "cached_value" points to the first associated set-oop.
  // The oop_limit helps find the last associated set-oop.
  // (See comments at the top of this file.)
  static RelocationHolder spec(address cached_value, jint method_index = 0) {
    RelocationHolder rh = newHolder();
    new(rh) virtual_call_Relocation(cached_value, method_index);
    return rh;
  }

private:
  address _cached_value; // location of set-value instruction
  jint    _method_index; // resolved method for a Java call

  virtual_call_Relocation(address cached_value, int method_index)
    : CallRelocation(relocInfo::virtual_call_type),
      _cached_value(cached_value),
      _method_index(method_index) {
    assert(cached_value != NULL, "first oop address must be specified");
  }

  friend class RelocIterator;
  virtual_call_Relocation() : CallRelocation(relocInfo::virtual_call_type) { }

public:
  address cached_value();

  int     method_index() { return _method_index; }
  Method* method_value();

  // data is packed as scaled offsets in "2_ints" format:  [f l] or [Ff Ll]
  // oop_limit is set to 0 if the limit falls somewhere within the call.
  // When unpacking, a zero oop_limit is taken to refer to the end of the call.
  // (This has the effect of bringing in the call's delay slot on SPARC.)
  void pack_data_to(CodeSection* dest);
  void unpack_data();

  bool clear_inline_cache();
};

class opt_virtual_call_Relocation : public CallRelocation {
public:
  static RelocationHolder spec(int method_index = 0) {
    RelocationHolder rh = newHolder();
    new(rh) opt_virtual_call_Relocation(method_index);
    return rh;
  }

private:
  jint _method_index; // resolved method for a Java call

  opt_virtual_call_Relocation(int method_index)
    : CallRelocation(relocInfo::opt_virtual_call_type),
      _method_index(method_index) { }

  friend class RelocIterator;
  opt_virtual_call_Relocation() : CallRelocation(relocInfo::opt_virtual_call_type) {}

public:
  int     method_index() { return _method_index; }
  Method* method_value();

  void pack_data_to(CodeSection* dest);
  void unpack_data();

  bool clear_inline_cache();

  // find the matching static_stub
  address static_stub();
};

class static_call_Relocation : public CallRelocation {
public:
  static RelocationHolder spec(int method_index = 0) {
    RelocationHolder rh = newHolder();
    new(rh) static_call_Relocation(method_index);
    return rh;
  }

private:
  jint _method_index; // resolved method for a Java call

  static_call_Relocation(int method_index)
    : CallRelocation(relocInfo::static_call_type),
    _method_index(method_index) { }

  friend class RelocIterator;
  static_call_Relocation() : CallRelocation(relocInfo::static_call_type) {}

public:
  int     method_index() { return _method_index; }
  Method* method_value();

  void pack_data_to(CodeSection* dest);
  void unpack_data();

  bool clear_inline_cache();

  // find the matching static_stub
  address static_stub();
};

class static_stub_Relocation : public Relocation {
public:
  static RelocationHolder spec(address static_call) {
    RelocationHolder rh = newHolder();
    new(rh) static_stub_Relocation(static_call);
    return rh;
  }

private:
  address _static_call;  // location of corresponding static_call

  static_stub_Relocation(address static_call)
    : Relocation(relocInfo::static_stub_type),
      _static_call(static_call) { }

  friend class RelocIterator;
  static_stub_Relocation() : Relocation(relocInfo::static_stub_type) { }

public:
  bool clear_inline_cache();

  address static_call() { return _static_call; }

  // data is packed as a scaled offset in "1_int" format:  [c] or [Cc]
  void pack_data_to(CodeSection* dest);
  void unpack_data();
};

class runtime_call_Relocation : public CallRelocation {

public:
  static RelocationHolder spec() {
    RelocationHolder rh = newHolder();
    new(rh) runtime_call_Relocation();
    return rh;
  }

private:
  friend class RelocIterator;
  runtime_call_Relocation() : CallRelocation(relocInfo::runtime_call_type) { }

public:
};

class runtime_call_w_cp_Relocation : public CallRelocation {
public:
  static RelocationHolder spec() {
    RelocationHolder rh = newHolder();
    new(rh) runtime_call_w_cp_Relocation();
    return rh;
  }

private:
  friend class RelocIterator;
  runtime_call_w_cp_Relocation()
    : CallRelocation(relocInfo::runtime_call_w_cp_type),
      _offset(-4) /* <0 = invalid */ { }

  // On z/Architecture, runtime calls are either a sequence
  // of two instructions (load destination of call from constant pool + do call)
  // or a pc-relative call. The pc-relative call is faster, but it can only
  // be used if the destination of the call is not too far away.
  // In order to be able to patch a pc-relative call back into one using
  // the constant pool, we have to remember the location of the call's destination
  // in the constant pool.
  int _offset;

public:
  void set_constant_pool_offset(int offset) { _offset = offset; }
  int get_constant_pool_offset() { return _offset; }
  void pack_data_to(CodeSection * dest);
  void unpack_data();
};

// Trampoline Relocations.
// A trampoline allows to encode a small branch in the code, even if there
// is the chance that this branch can not reach all possible code locations.
// If the relocation finds that a branch is too far for the instruction
// in the code, it can patch it to jump to the trampoline where is
// sufficient space for a far branch. Needed on PPC.
class trampoline_stub_Relocation : public Relocation {
public:
  static RelocationHolder spec(address static_call) {
    RelocationHolder rh = newHolder();
    return (new (rh) trampoline_stub_Relocation(static_call));
  }

private:
  address _owner;    // Address of the NativeCall that owns the trampoline.

  trampoline_stub_Relocation(address owner)
    : Relocation(relocInfo::trampoline_stub_type),
      _owner(owner) { }

  friend class RelocIterator;
  trampoline_stub_Relocation() : Relocation(relocInfo::trampoline_stub_type) { }

public:

  // Return the address of the NativeCall that owns the trampoline.
  address owner() { return _owner; }

  void pack_data_to(CodeSection * dest);
  void unpack_data();

  // Find the trampoline stub for a call.
  static address get_trampoline_for(address call, nmethod* code);
};

class external_word_Relocation : public DataRelocation {
public:
  static RelocationHolder spec(address target) {
    assert(target != NULL, "must not be null");
    RelocationHolder rh = newHolder();
    new(rh) external_word_Relocation(target);
    return rh;
  }

  // Use this one where all 32/64 bits of the target live in the code stream.
  // The target must be an intptr_t, and must be absolute (not relative).
  static RelocationHolder spec_for_immediate() {
    RelocationHolder rh = newHolder();
    new(rh) external_word_Relocation(NULL);
    return rh;
  }

  // Some address looking values aren't safe to treat as relocations
  // and should just be treated as constants.
  static bool can_be_relocated(address target) {
    assert(target == NULL || (uintptr_t)target >= (uintptr_t)OSInfo::vm_page_size(), INTPTR_FORMAT, (intptr_t)target);
    return target != NULL;
  }

private:
  address _target;                  // address in runtime

  external_word_Relocation(address target)
    : DataRelocation(relocInfo::external_word_type), _target(target) { }

  friend class RelocIterator;
  external_word_Relocation() : DataRelocation(relocInfo::external_word_type) { }

public:
  // data is packed as a well-known address in "1_int" format:  [a] or [Aa]
  // The function runtime_address_to_index is used to turn full addresses
  // to short indexes, if they are pre-registered by the stub mechanism.
  // If the "a" value is 0 (i.e., _target is NULL), the address is stored
  // in the code stream.  See external_word_Relocation::target().
  void pack_data_to(CodeSection* dest);
  void unpack_data();

  void fix_relocation_after_move(const CodeBuffer* src, CodeBuffer* dest);
  address  target();        // if _target==NULL, fetch addr from code stream
  address  value()          { return target(); }
};

class internal_word_Relocation : public DataRelocation {

public:
  static RelocationHolder spec(address target) {
    assert(target != NULL, "must not be null");
    RelocationHolder rh = newHolder();
    new(rh) internal_word_Relocation(target);
    return rh;
  }

  // use this one where all the bits of the target can fit in the code stream:
  static RelocationHolder spec_for_immediate() {
    RelocationHolder rh = newHolder();
    new(rh) internal_word_Relocation(NULL);
    return rh;
  }

  // default section -1 means self-relative
  internal_word_Relocation(address target, int section = -1,
    relocInfo::relocType type = relocInfo::internal_word_type)
    : DataRelocation(type), _target(target), _section(section) { }

protected:
  address _target;                  // address in CodeBlob
  int     _section;                 // section providing base address, if any

  friend class RelocIterator;
  internal_word_Relocation(relocInfo::relocType type = relocInfo::internal_word_type)
    : DataRelocation(type) { }

  // bit-width of LSB field in packed offset, if section >= 0
  enum { section_width = 2 }; // must equal CodeBuffer::sect_bits

public:
  // data is packed as a scaled offset in "1_int" format:  [o] or [Oo]
  // If the "o" value is 0 (i.e., _target is NULL), the offset is stored
  // in the code stream.  See internal_word_Relocation::target().
  // If _section is not -1, it is appended to the low bits of the offset.
  void pack_data_to(CodeSection* dest);
  void unpack_data();

  void fix_relocation_after_move(const CodeBuffer* src, CodeBuffer* dest);
  address  target();        // if _target==NULL, fetch addr from code stream
  int      section()        { return _section;   }
  address  value()          { return target();   }
};

class section_word_Relocation : public internal_word_Relocation {
public:
  static RelocationHolder spec(address target, int section) {
    RelocationHolder rh = newHolder();
    new(rh) section_word_Relocation(target, section);
    return rh;
  }

  section_word_Relocation(address target, int section)
    : internal_word_Relocation(target, section, relocInfo::section_word_type) {
    assert(target != NULL, "must not be null");
    assert(section >= 0 && section < RelocIterator::SECT_LIMIT, "must be a valid section");
  }

  //void pack_data_to -- inherited
  void unpack_data();

private:
  friend class RelocIterator;
  section_word_Relocation() : internal_word_Relocation(relocInfo::section_word_type) { }
};

class poll_Relocation : public Relocation {
  bool          is_data()                      { return true; }
  void     fix_relocation_after_move(const CodeBuffer* src, CodeBuffer* dest);
public:
  poll_Relocation(relocInfo::relocType type = relocInfo::poll_type) : Relocation(type) { }
};

class poll_return_Relocation : public poll_Relocation {
public:
  poll_return_Relocation() : poll_Relocation(relocInfo::relocInfo::poll_return_type) { }
};

// We know all the xxx_Relocation classes, so now we can define these:
#define EACH_CASE(name)                                         \
inline name##_Relocation* RelocIterator::name##_reloc() {       \
  assert(type() == relocInfo::name##_type, "type must agree");  \
  /* The purpose of the placed "new" is to re-use the same */   \
  /* stack storage for each new iteration. */                   \
  name##_Relocation* r = new(_rh) name##_Relocation();          \
  r->set_binding(this);                                         \
  r->name##_Relocation::unpack_data();                          \
  return r;                                                     \
}
APPLY_TO_RELOCATIONS(EACH_CASE);
#undef EACH_CASE

inline RelocIterator::RelocIterator(CompiledMethod* nm, address begin, address limit) {
  initialize(nm, begin, limit);
}

#endif // SHARE_CODE_RELOCINFO_HPP

quality100%

¤ Dauer der Verarbeitung: 0.24 Sekunden (vorverarbeitet) ¤

Wurzel

Suchen

Beweissystem der NASA

Beweissystem Isabelle

NIST Cobol Testsuite

Cephes Mathematical Library

Wiener Entwicklungsmethode

Haftungshinweis

Die Informationen auf dieser Webseite wurden nach bestem Wissen sorgfältig zusammengestellt. Es wird jedoch weder Vollständigkeit, noch Richtigkeit, noch Qualität der bereit gestellten Informationen zugesichert.

Bemerkung:

Die farbliche Syntaxdarstellung ist noch experimentell.