1 /*
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   6  * under the terms of the GNU General Public License version 2 only, as
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  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
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  24 
  25 #ifndef SHARE_CODE_RELOCINFO_HPP
  26 #define SHARE_CODE_RELOCINFO_HPP
  27 
  28 #include "memory/allocation.hpp"
  29 #include "oops/oopsHierarchy.hpp"
  30 #include "runtime/osInfo.hpp"
  31 #include "utilities/checkedCast.hpp"
  32 #include "utilities/globalDefinitions.hpp"
  33 #include "utilities/macros.hpp"
  34 
  35 #include <new>
  36 
  37 class CodeBlob;
  38 class Metadata;
  39 class NativeMovConstReg;
  40 class nmethod;
  41 
  42 // Types in this file:
  43 //    relocInfo
  44 //      One element of an array of halfwords encoding compressed relocations.
  45 //      Also, the source of relocation types (relocInfo::oop_type, ...).
  46 //    Relocation
  47 //      A flyweight object representing a single relocation.
  48 //      It is fully unpacked from the compressed relocation array.
  49 //    metadata_Relocation, ... (subclasses of Relocation)
  50 //      The location of some type-specific operations (metadata_addr, ...).
  51 //      Also, the source of relocation specs (metadata_Relocation::spec, ...).
  52 //    oop_Relocation, ... (subclasses of Relocation)
  53 //      oops in the code stream (strings, class loaders)
  54 //      Also, the source of relocation specs (oop_Relocation::spec, ...).
  55 //    RelocationHolder
  56 //      A value type which acts as a union holding a Relocation object.
  57 //      Represents a relocation spec passed into a CodeBuffer during assembly.
  58 //    RelocIterator
  59 //      A StackObj which iterates over the relocations associated with
  60 //      a range of code addresses.  Can be used to operate a copy of code.
  61 
  62 
  63 // Notes on relocType:
  64 //
  65 // These hold enough information to read or write a value embedded in
  66 // the instructions of an CodeBlob.  They're used to update:
  67 //
  68 //   1) embedded oops     (isOop()          == true)
  69 //   2) inline caches     (isIC()           == true)
  70 //   3) runtime calls     (isRuntimeCall()  == true)
  71 //   4) internal word ref (isInternalWord() == true)
  72 //   5) external word ref (isExternalWord() == true)
  73 //
  74 // when objects move (GC) or if code moves (compacting the code heap).
  75 // They are also used to patch the code (if a call site must change)
  76 //
  77 // A relocInfo is represented in 16 bits:
  78 //   4 bits indicating the relocation type
  79 //  12 bits indicating the offset from the previous relocInfo address
  80 //
  81 // The offsets accumulate along the relocInfo stream to encode the
  82 // address within the CodeBlob, which is named RelocIterator::addr().
  83 // The address of a particular relocInfo always points to the first
  84 // byte of the relevant instruction (and not to any of its subfields
  85 // or embedded immediate constants).
  86 //
  87 // The offset value is scaled appropriately for the target machine.
  88 // (See relocInfo_<arch>.hpp for the offset scaling.)
  89 //
  90 // On some machines, there may also be a "format" field which may provide
  91 // additional information about the format of the instruction stream
  92 // at the corresponding code address.  The format value is usually zero.
  93 // Any machine (such as Intel) whose instructions can sometimes contain
  94 // more than one relocatable constant needs format codes to distinguish
  95 // which operand goes with a given relocation.
  96 //
  97 // If the target machine needs N format bits, the offset has 12-N bits,
  98 // the format is encoded between the offset and the type, and the
  99 // relocInfo_<arch>.hpp file has manifest constants for the format codes.
 100 //
 101 // If the type is "data_prefix_tag" then the offset bits are further encoded,
 102 // and in fact represent not a code-stream offset but some inline data.
 103 // The data takes the form of a counted sequence of halfwords, which
 104 // precedes the actual relocation record.  (Clients never see it directly.)
 105 // The interpretation of this extra data depends on the relocation type.
 106 //
 107 // On machines that have 32-bit immediate fields, there is usually
 108 // little need for relocation "prefix" data, because the instruction stream
 109 // is a perfectly reasonable place to store the value.  On machines in
 110 // which 32-bit values must be "split" across instructions, the relocation
 111 // data is the "true" specification of the value, which is then applied
 112 // to some field of the instruction (22 or 13 bits, on SPARC).
 113 //
 114 // Whenever the location of the CodeBlob changes, any PC-relative
 115 // relocations, and any internal_word_type relocations, must be reapplied.
 116 // After the GC runs, oop_type relocations must be reapplied.
 117 //
 118 //
 119 // Here are meanings of the types:
 120 //
 121 // relocInfo::none -- a filler record
 122 //   Value:  none
 123 //   Instruction: The corresponding code address is ignored
 124 //   Data:  Any data prefix and format code are ignored
 125 //   (This means that any relocInfo can be disabled by setting
 126 //   its type to none.  See relocInfo::remove.)
 127 //
 128 // relocInfo::oop_type, relocInfo::metadata_type -- a reference to an oop or meta data
 129 //   Value:  an oop, or else the address (handle) of an oop
 130 //   Instruction types: memory (load), set (load address)
 131 //   Data:  []       an oop stored in 4 bytes of instruction
 132 //          [[N]n]   the index of an oop in the CodeBlob's oop pool
 133 //
 134 // relocInfo::internal_word_type -- an address within the same CodeBlob
 135 // relocInfo::section_word_type -- same, but can refer to another section
 136 //   Value:  an address in the CodeBlob's code or constants section
 137 //   Instruction types: memory (load), set (load address)
 138 //   Data:  []     stored in 4 bytes of instruction
 139 //          [[L]l] a relative offset (see [About Offsets] below)
 140 //   In the case of section_word_type, the offset is relative to a section
 141 //   base address, and the section number (e.g., SECT_INSTS) is encoded
 142 //   into the low two bits of the offset L.
 143 //
 144 // relocInfo::external_word_type -- a fixed address in the runtime system
 145 //   Value:  an address
 146 //   Instruction types: memory (load), set (load address)
 147 //   Data:  []   stored in 4 bytes of instruction
 148 //          [n]  the index of a "well-known" stub (usual case on RISC)
 149 //          [Ll] a 32-bit address
 150 //
 151 // relocInfo::runtime_call_type -- a fixed subroutine in the runtime system
 152 //   Value:  an address
 153 //   Instruction types: PC-relative call (or a PC-relative branch)
 154 //   Data:  []   stored in 4 bytes of instruction
 155 //
 156 // relocInfo::static_call_type -- a static call
 157 //   Value:  an CodeBlob, a stub, or a fixup routine
 158 //   Instruction types: a call
 159 //   Data:  []
 160 //   The identity of the callee is extracted from debugging information.
 161 //   //%note reloc_3
 162 //
 163 // relocInfo::virtual_call_type -- a virtual call site (which includes an inline
 164 //                                 cache)
 165 //   Value:  an CodeBlob, a stub, the interpreter, or a fixup routine
 166 //   Instruction types: a call, plus some associated set-oop instructions
 167 //   Data:  []       the associated set-oops are adjacent to the call
 168 //          [n]      n is a relative offset to the first set-oop
 169 //          [[N]n l] and l is a limit within which the set-oops occur
 170 //          [Nn Ll]  both n and l may be 32 bits if necessary
 171 //   The identity of the callee is extracted from debugging information.
 172 //
 173 // relocInfo::opt_virtual_call_type -- a virtual call site that is statically bound
 174 //
 175 //    Same info as a static_call_type. We use a special type, so the handling of
 176 //    virtuals and statics are separated.
 177 //
 178 //
 179 //   The offset n points to the first set-oop.  (See [About Offsets] below.)
 180 //   In turn, the set-oop instruction specifies or contains an oop cell devoted
 181 //   exclusively to the IC call, which can be patched along with the call.
 182 //
 183 //   The locations of any other set-oops are found by searching the relocation
 184 //   information starting at the first set-oop, and continuing until all
 185 //   relocations up through l have been inspected.  The value l is another
 186 //   relative offset.  (Both n and l are relative to the call's first byte.)
 187 //
 188 //   The limit l of the search is exclusive.  However, if it points within
 189 //   the call (e.g., offset zero), it is adjusted to point after the call and
 190 //   any associated machine-specific delay slot.
 191 //
 192 //   Since the offsets could be as wide as 32-bits, these conventions
 193 //   put no restrictions whatever upon code reorganization.
 194 //
 195 //   The compiler is responsible for ensuring that transition from a clean
 196 //   state to a monomorphic compiled state is MP-safe.  This implies that
 197 //   the system must respond well to intermediate states where a random
 198 //   subset of the set-oops has been correctly from the clean state
 199 //   upon entry to the VEP of the compiled method.  In the case of a
 200 //   machine (Intel) with a single set-oop instruction, the 32-bit
 201 //   immediate field must not straddle a unit of memory coherence.
 202 //   //%note reloc_3
 203 //
 204 // relocInfo::static_stub_type -- an extra stub for each static_call_type
 205 //   Value:  none
 206 //   Instruction types: a virtual call:  { set_oop; jump; }
 207 //   Data:  [[N]n]  the offset of the associated static_call reloc
 208 //   This stub becomes the target of a static call which must be upgraded
 209 //   to a virtual call (because the callee is interpreted).
 210 //   See [About Offsets] below.
 211 //   //%note reloc_2
 212 //
 213 // relocInfo::poll_[return_]type -- a safepoint poll
 214 //   Value:  none
 215 //   Instruction types: memory load or test
 216 //   Data:  none
 217 //
 218 // For example:
 219 //
 220 //   INSTRUCTIONS                        RELOC: TYPE    PREFIX DATA
 221 //   ------------                               ----    -----------
 222 // sethi      %hi(myObject),  R               oop_type [n(myObject)]
 223 // ld      [R+%lo(myObject)+fldOffset], R2    oop_type [n(myObject) fldOffset]
 224 // add R2, 1, R2
 225 // st  R2, [R+%lo(myObject)+fldOffset]        oop_type [n(myObject) fldOffset]
 226 //%note reloc_1
 227 //
 228 // This uses 4 instruction words, 8 relocation halfwords,
 229 // and an entry (which is shareable) in the CodeBlob's oop pool,
 230 // for a total of 36 bytes.
 231 //
 232 // Note that the compiler is responsible for ensuring the "fldOffset" when
 233 // added to "%lo(myObject)" does not overflow the immediate fields of the
 234 // memory instructions.
 235 //
 236 //
 237 // [About Offsets] Relative offsets are supplied to this module as
 238 // positive byte offsets, but they may be internally stored scaled
 239 // and/or negated, depending on what is most compact for the target
 240 // system.  Since the object pointed to by the offset typically
 241 // precedes the relocation address, it is profitable to store
 242 // these negative offsets as positive numbers, but this decision
 243 // is internal to the relocation information abstractions.
 244 //
 245 
 246 class Relocation;
 247 class CodeBuffer;
 248 class CodeSection;
 249 class RelocIterator;
 250 
 251 class relocInfo {
 252   friend class RelocIterator;
 253  public:
 254   enum relocType {
 255     none                    =  0, // Used when no relocation should be generated
 256     oop_type                =  1, // embedded oop
 257     virtual_call_type       =  2, // a standard inline cache call for a virtual send
 258     opt_virtual_call_type   =  3, // a virtual call that has been statically bound (i.e., no IC cache)
 259     static_call_type        =  4, // a static send
 260     static_stub_type        =  5, // stub-entry for static send  (takes care of interpreter case)
 261     runtime_call_type       =  6, // call to fixed external routine
 262     external_word_type      =  7, // reference to fixed external address
 263     internal_word_type      =  8, // reference within the current code blob
 264     section_word_type       =  9, // internal, but a cross-section reference
 265     poll_type               = 10, // polling instruction for safepoints
 266     poll_return_type        = 11, // polling instruction for safepoints at return
 267     metadata_type           = 12, // metadata that used to be oops
 268     trampoline_stub_type    = 13, // stub-entry for trampoline
 269     runtime_call_w_cp_type  = 14, // Runtime call which may load its target from the constant pool
 270     data_prefix_tag         = 15, // tag for a prefix (carries data arguments)
 271     post_call_nop_type      = 16, // A tag for post call nop relocations
 272     entry_guard_type        = 17, // A tag for an nmethod entry barrier guard value
 273     barrier_type            = 18, // GC barrier data
 274     type_mask               = 31  // A mask which selects only the above values
 275   };
 276 
 277  private:
 278   unsigned short _value;
 279 
 280   static const enum class RawBitsToken {} RAW_BITS{};
 281 
 282   relocInfo(relocType type, RawBitsToken, int bits)
 283     : _value(checked_cast<unsigned short>((type << nontype_width) + bits)) { }
 284 
 285   static relocType check_relocType(relocType type) NOT_DEBUG({ return type; });
 286 
 287   static void check_offset_and_format(int offset, int format) NOT_DEBUG_RETURN;
 288 
 289   static int compute_bits(int offset, int format) {
 290     check_offset_and_format(offset, format);
 291     return (offset / offset_unit) + (format << offset_width);
 292   }
 293 
 294  public:
 295   relocInfo(relocType type, int offset, int format = 0)
 296     : relocInfo(check_relocType(type), RAW_BITS, compute_bits(offset, format)) {}
 297 
 298   #define APPLY_TO_RELOCATIONS(visitor) \
 299     visitor(oop) \
 300     visitor(metadata) \
 301     visitor(virtual_call) \
 302     visitor(opt_virtual_call) \
 303     visitor(static_call) \
 304     visitor(static_stub) \
 305     visitor(runtime_call) \
 306     visitor(runtime_call_w_cp) \
 307     visitor(external_word) \
 308     visitor(internal_word) \
 309     visitor(poll) \
 310     visitor(poll_return) \
 311     visitor(section_word) \
 312     visitor(trampoline_stub) \
 313     visitor(post_call_nop) \
 314     visitor(entry_guard) \
 315     visitor(barrier) \
 316 
 317 
 318  public:
 319   enum : unsigned short{
 320     value_width             = sizeof(unsigned short) * BitsPerByte,
 321     type_width              = 5,   // == log2(type_mask+1)
 322     nontype_width           = value_width - type_width,
 323     datalen_width           = nontype_width-1,
 324     datalen_tag             = 1 << datalen_width,  // or-ed into _value
 325     datalen_limit           = 1 << datalen_width,
 326     datalen_mask            = (1 << datalen_width)-1
 327   };
 328 
 329   // accessors
 330  public:
 331   relocType  type()       const { return (relocType)((unsigned)_value >> nontype_width); }
 332   int  format()           const { return format_mask==0? 0: format_mask &
 333                                          ((unsigned)_value >> offset_width); }
 334   int  addr_offset()      const { assert(!is_prefix(), "must have offset");
 335                                   return (_value & offset_mask)*offset_unit; }
 336 
 337  protected:
 338   const short* data()       const { assert(is_datalen(), "must have data");
 339                                     return (const short*)(this + 1); }
 340   unsigned short datalen()  const { assert(is_datalen(), "must have data");
 341                                   return (_value & datalen_mask); }
 342   unsigned short immediate() const { assert(is_immediate(), "must have immed");
 343                                   return (_value & datalen_mask); }
 344  public:
 345   static int addr_unit()        { return offset_unit; }
 346   static int offset_limit()     { return (1 << offset_width) * offset_unit; }
 347 
 348   void set_type(relocType type);
 349 
 350   void remove() { set_type(none); }
 351 
 352  protected:
 353   bool is_none()                const { return type() == none; }
 354   bool is_prefix()              const { return type() == data_prefix_tag; }
 355   bool is_datalen()             const { assert(is_prefix(), "must be prefix");
 356                                         return (_value & datalen_tag) != 0; }
 357   bool is_immediate()           const { assert(is_prefix(), "must be prefix");
 358                                         return (_value & datalen_tag) == 0; }
 359 
 360  public:
 361   // Occasionally records of type relocInfo::none will appear in the stream.
 362   // We do not bother to filter these out, but clients should ignore them.
 363   // These records serve as "filler" in three ways:
 364   //  - to skip large spans of unrelocated code (this is rare)
 365   //  - to pad out the relocInfo array to the required oop alignment
 366   //  - to disable old relocation information which is no longer applicable
 367 
 368   static relocInfo filler_info() {
 369     return relocInfo(relocInfo::none, relocInfo::offset_limit() - relocInfo::offset_unit);
 370   }
 371 
 372   // Every non-prefix relocation may be preceded by at most one prefix,
 373   // which supplies 1 or more halfwords of associated data.  Conventionally,
 374   // an int is represented by 0, 1, or 2 halfwords, depending on how
 375   // many bits are required to represent the value.  (In addition,
 376   // if the sole halfword is a 10-bit unsigned number, it is made
 377   // "immediate" in the prefix header word itself.  This optimization
 378   // is invisible outside this module.)
 379 
 380   static relocInfo prefix_info(int datalen = 0) {
 381     assert(relocInfo::fits_into_immediate(datalen), "datalen in limits");
 382     return relocInfo(relocInfo::data_prefix_tag, relocInfo::RAW_BITS, relocInfo::datalen_tag | datalen);
 383   }
 384 
 385  private:
 386   // an immediate relocInfo optimizes a prefix with one 10-bit unsigned value
 387   static relocInfo immediate_relocInfo(int data0) {
 388     assert(fits_into_immediate(data0), "data0 in limits");
 389     return relocInfo(relocInfo::data_prefix_tag, RAW_BITS, data0);
 390   }
 391   static bool fits_into_immediate(int data0) {
 392     return (data0 >= 0 && data0 < datalen_limit);
 393   }
 394 
 395  public:
 396   // Support routines for compilers.
 397 
 398   // This routine takes an infant relocInfo (unprefixed) and
 399   // edits in its prefix, if any.  It also updates dest.locs_end.
 400   void initialize(CodeSection* dest, Relocation* reloc);
 401 
 402   // This routine updates a prefix and returns the limit pointer.
 403   // It tries to compress the prefix from 32 to 16 bits, and if
 404   // successful returns a reduced "prefix_limit" pointer.
 405   relocInfo* finish_prefix(short* prefix_limit);
 406 
 407   // bit-packers for the data array:
 408 
 409   // As it happens, the bytes within the shorts are ordered natively,
 410   // but the shorts within the word are ordered big-endian.
 411   // This is an arbitrary choice, made this way mainly to ease debugging.
 412   static short data0_from_int(jint x)         { return (short)(x >> value_width); }
 413   static short data1_from_int(jint x)         { return (short)x; }
 414   static jint jint_from_data(short* data) {
 415     return (data[0] << value_width) + (unsigned short)data[1];
 416   }
 417 
 418   static jint short_data_at(int n, short* data, int datalen) {
 419     return datalen > n ? data[n] : 0;
 420   }
 421 
 422   static jint jint_data_at(int n, short* data, int datalen) {
 423     return datalen > n+1 ? jint_from_data(&data[n]) : short_data_at(n, data, datalen);
 424   }
 425 
 426   // Update methods for relocation information
 427   // (since code is dynamically patched, we also need to dynamically update the relocation info)
 428   // Both methods takes old_type, so it is able to perform sanity checks on the information removed.
 429   static void change_reloc_info_for_address(RelocIterator *itr, address pc, relocType old_type, relocType new_type);
 430 
 431   // Machine dependent stuff
 432 #include CPU_HEADER(relocInfo)
 433 
 434  protected:
 435   // Derived constant, based on format_width which is PD:
 436   enum {
 437     offset_width       = nontype_width - format_width,
 438     offset_mask        = (1<<offset_width) - 1,
 439     format_mask        = (1<<format_width) - 1
 440   };
 441  public:
 442   enum {
 443 #ifdef _LP64
 444     // for use in format
 445     // format_width must be at least 1 on _LP64
 446     narrow_oop_in_const = 1,
 447 #endif
 448     // Conservatively large estimate of maximum length (in shorts)
 449     // of any relocation record.
 450     // Extended format is length prefix, data words, and tag/offset suffix.
 451     length_limit       = 1 + 1 + (3*BytesPerWord/BytesPerShort) + 1,
 452     have_format        = format_width > 0
 453   };
 454 };
 455 
 456 #define FORWARD_DECLARE_EACH_CLASS(name)              \
 457 class name##_Relocation;
 458 APPLY_TO_RELOCATIONS(FORWARD_DECLARE_EACH_CLASS)
 459 #undef FORWARD_DECLARE_EACH_CLASS
 460 
 461 // Holder for flyweight relocation objects.
 462 // Although the flyweight subclasses are of varying sizes,
 463 // the holder is "one size fits all".
 464 class RelocationHolder {
 465   friend class Relocation;
 466 
 467  private:
 468   // A Relocation is "held" by placement constructing a Relocation into
 469   // _relocbuf. Hence, _relocbuf must accomodate all subclasses of
 470   // Relocation. We also need the Relocation base class to be at the same
 471   // address as the start of the object, e.g. at the address of _relocbuf.
 472   // Both of these requirements are checked (see emplace_relocation).
 473   // The placement of the base class subobject isn't guaranteed by C++, since
 474   // these aren't standard layout classes, but all supported implementations
 475   // provide that behavior.  If that changes, we can instead add a Relocation*
 476   // _reloc member to capture the result of the placement new, and use that to
 477   // access the base subobject.
 478   static const size_t _relocbuf_size = 5 * sizeof(void*);
 479   alignas(void*) char _relocbuf[_relocbuf_size];
 480 
 481   template<typename Reloc, typename... Args>
 482   void emplace_relocation(const Args&... args) {
 483     static_assert(std::is_base_of<Relocation, Reloc>::value, "not Relocation");
 484     static_assert(sizeof(Reloc) <= sizeof(_relocbuf), "_relocbuf too small");
 485     Relocation* reloc = ::new (_relocbuf) Reloc(args...);
 486     // Verify the base class subobject of the object constructed into
 487     // _relocbuf is at the same address as the derived object.
 488     assert(static_cast<const void*>(reloc) == _relocbuf, "invariant");
 489   }
 490 
 491   // Support for Relocation::copy_into.
 492   // reloc should be a most derived object.
 493   template<typename Reloc>
 494   void copy_into_impl(const Reloc& reloc) {
 495     emplace_relocation<Reloc>(reloc);
 496   }
 497 
 498   // Tag for selecting the constructor below and carrying the type of the
 499   // relocation object the new holder will (initially) contain.
 500   template<typename Reloc> struct Construct {};
 501 
 502   // Constructor used by construct().  Constructs a new holder containing a
 503   // relocation of type Reloc that is constructed using the provided args.
 504   template<typename Reloc, typename... Args>
 505   RelocationHolder(Construct<Reloc>, const Args&... args) {
 506     emplace_relocation<Reloc>(args...);
 507   }
 508 
 509  public:
 510   Relocation* reloc() const { return (Relocation*)_relocbuf; }
 511   inline relocInfo::relocType type() const;
 512 
 513   // Return a holder containing a relocation of type Reloc, constructed using args.
 514   template<typename Reloc, typename... Args>
 515   static RelocationHolder construct(const Args&... args) {
 516     return RelocationHolder(Construct<Reloc>(), args...);
 517   }
 518 
 519   RelocationHolder();           // Initializes type to none.
 520 
 521   // Depends on the destructor for all relocation types being trivial
 522   // (verified in .cpp file).
 523   ~RelocationHolder() = default;
 524 
 525   RelocationHolder(const RelocationHolder& from);
 526   RelocationHolder& operator=(const RelocationHolder& from);
 527 
 528   static const RelocationHolder none;
 529 };
 530 
 531 // A RelocIterator iterates through the relocation information of a CodeBlob.
 532 // It provides access to successive relocations as it is advanced through a
 533 // code stream.
 534 // Usage:
 535 //   RelocIterator iter(nm);
 536 //   while (iter.next()) {
 537 //     iter.reloc()->some_operation();
 538 //   }
 539 // or:
 540 //   RelocIterator iter(nm);
 541 //   while (iter.next()) {
 542 //     switch (iter.type()) {
 543 //      case relocInfo::oop_type          :
 544 //      case relocInfo::ic_type           :
 545 //      case relocInfo::prim_type         :
 546 //      case relocInfo::uncommon_type     :
 547 //      case relocInfo::runtime_call_type :
 548 //      case relocInfo::internal_word_type:
 549 //      case relocInfo::external_word_type:
 550 //      ...
 551 //     }
 552 //   }
 553 
 554 class RelocIterator : public StackObj {
 555   friend class section_word_Relocation; // for section verification
 556   enum { SECT_LIMIT = 3 };  // must be equal to CodeBuffer::SECT_LIMIT, checked in ctor
 557   friend class Relocation;
 558   friend class relocInfo;   // for change_reloc_info_for_address only
 559   typedef relocInfo::relocType relocType;
 560 
 561  private:
 562   address         _limit;   // stop producing relocations after this _addr
 563   relocInfo*      _current; // the current relocation information
 564   relocInfo*      _end;     // end marker; we're done iterating when _current == _end
 565   nmethod*        _code;    // compiled method containing _addr
 566   address         _addr;    // instruction to which the relocation applies
 567   short           _databuf; // spare buffer for compressed data
 568   short*          _data;    // pointer to the relocation's data
 569   short           _datalen; // number of halfwords in _data
 570 
 571   // Base addresses needed to compute targets of section_word_type relocs.
 572   address _section_start[SECT_LIMIT];
 573   address _section_end  [SECT_LIMIT];
 574 
 575   void set_has_current(bool b) {
 576     _datalen = !b ? -1 : 0;
 577     debug_only(_data = nullptr);
 578   }
 579   void set_current(relocInfo& ri) {
 580     _current = &ri;
 581     set_has_current(true);
 582   }
 583 
 584   RelocationHolder _rh; // where the current relocation is allocated
 585 
 586   relocInfo* current() const { assert(has_current(), "must have current");
 587                                return _current; }
 588 
 589   void set_limits(address begin, address limit);
 590 
 591   void advance_over_prefix();    // helper method
 592 
 593   void initialize_misc();
 594 
 595   void initialize(nmethod* nm, address begin, address limit);
 596 
 597   RelocIterator() { initialize_misc(); }
 598 
 599  public:
 600   // constructor
 601   RelocIterator(nmethod* nm, address begin = nullptr, address limit = nullptr);
 602   RelocIterator(CodeSection* cb, address begin = nullptr, address limit = nullptr);
 603 
 604   // get next reloc info, return !eos
 605   bool next() {
 606     _current++;
 607     assert(_current <= _end, "must not overrun relocInfo");
 608     if (_current == _end) {
 609       set_has_current(false);
 610       return false;
 611     }
 612     set_has_current(true);
 613 
 614     if (_current->is_prefix()) {
 615       advance_over_prefix();
 616       assert(!current()->is_prefix(), "only one prefix at a time");
 617     }
 618 
 619     _addr += _current->addr_offset();
 620 
 621     if (_limit != nullptr && _addr >= _limit) {
 622       set_has_current(false);
 623       return false;
 624     }
 625 
 626     return true;
 627   }
 628 
 629   // accessors
 630   address      limit()        const { return _limit; }
 631   relocType    type()         const { return current()->type(); }
 632   int          format()       const { return (relocInfo::have_format) ? current()->format() : 0; }
 633   address      addr()         const { return _addr; }
 634   nmethod*     code()         const { return _code; }
 635   short*       data()         const { return _data; }
 636   int          datalen()      const { return _datalen; }
 637   bool     has_current()      const { return _datalen >= 0; }
 638   bool   addr_in_const()      const;
 639 
 640   address section_start(int n) const {
 641     assert(_section_start[n], "must be initialized");
 642     return _section_start[n];
 643   }
 644   address section_end(int n) const {
 645     assert(_section_end[n], "must be initialized");
 646     return _section_end[n];
 647   }
 648 
 649   // The address points to the affected displacement part of the instruction.
 650   // For RISC, this is just the whole instruction.
 651   // For Intel, this is an unaligned 32-bit word.
 652 
 653   // type-specific relocation accessors:  oop_Relocation* oop_reloc(), etc.
 654   #define EACH_TYPE(name)                               \
 655   inline name##_Relocation* name##_reloc();
 656   APPLY_TO_RELOCATIONS(EACH_TYPE)
 657   #undef EACH_TYPE
 658   // generic relocation accessor; switches on type to call the above
 659   Relocation* reloc();
 660 
 661 #ifndef PRODUCT
 662  public:
 663   void print();
 664   void print_current();
 665 #endif
 666 };
 667 
 668 
 669 // A Relocation is a flyweight object allocated within a RelocationHolder.
 670 // It represents the relocation data of relocation record.
 671 // So, the RelocIterator unpacks relocInfos into Relocations.
 672 
 673 class Relocation {
 674   friend class RelocIterator;
 675 
 676  private:
 677   // When a relocation has been created by a RelocIterator,
 678   // this field is non-null.  It allows the relocation to know
 679   // its context, such as the address to which it applies.
 680   RelocIterator* _binding;
 681 
 682   relocInfo::relocType _rtype;
 683 
 684  protected:
 685   RelocIterator* binding() const {
 686     assert(_binding != nullptr, "must be bound");
 687     return _binding;
 688   }
 689   void set_binding(RelocIterator* b) {
 690     assert(_binding == nullptr, "must be unbound");
 691     _binding = b;
 692     assert(_binding != nullptr, "must now be bound");
 693   }
 694 
 695   explicit Relocation(relocInfo::relocType rtype) : _binding(nullptr), _rtype(rtype) { }
 696 
 697   // Helper for copy_into functions for derived classes.
 698   // Forwards operation to RelocationHolder::copy_into_impl so that
 699   // RelocationHolder only needs to befriend this class, rather than all
 700   // derived classes that implement copy_into.
 701   template<typename Reloc>
 702   static void copy_into_helper(const Reloc& reloc, RelocationHolder& holder) {
 703     holder.copy_into_impl(reloc);
 704   }
 705 
 706  public:
 707   // make a generic relocation for a given type (if possible)
 708   static RelocationHolder spec_simple(relocInfo::relocType rtype);
 709 
 710   // here is the type-specific hook which writes relocation data:
 711   virtual void pack_data_to(CodeSection* dest) { }
 712 
 713   // here is the type-specific hook which reads (unpacks) relocation data:
 714   virtual void unpack_data() {
 715     assert(datalen()==0 || type()==relocInfo::none, "no data here");
 716   }
 717 
 718  protected:
 719   // Helper functions for pack_data_to() and unpack_data().
 720 
 721   // Most of the compression logic is confined here.
 722   // (The "immediate data" mechanism of relocInfo works independently
 723   // of this stuff, and acts to further compress most 1-word data prefixes.)
 724 
 725   // A variable-width int is encoded as a short if it will fit in 16 bits.
 726   // The decoder looks at datalen to decide whether to unpack short or jint.
 727   // Most relocation records are quite simple, containing at most two ints.
 728 
 729   static bool is_short(jint x) { return x == (short)x; }
 730   static short* add_short(short* p, short x)  { *p++ = x; return p; }
 731   static short* add_jint (short* p, jint x) {
 732     *p++ = relocInfo::data0_from_int(x); *p++ = relocInfo::data1_from_int(x);
 733     return p;
 734   }
 735   static short* add_var_int(short* p, jint x) {   // add a variable-width int
 736     if (is_short(x))  p = add_short(p, (short)x);
 737     else              p = add_jint (p, x);
 738     return p;
 739   }
 740 
 741   static short* pack_1_int_to(short* p, jint x0) {
 742     // Format is one of:  [] [x] [Xx]
 743     if (x0 != 0)  p = add_var_int(p, x0);
 744     return p;
 745   }
 746   int unpack_1_int() {
 747     assert(datalen() <= 2, "too much data");
 748     return relocInfo::jint_data_at(0, data(), datalen());
 749   }
 750 
 751   // With two ints, the short form is used only if both ints are short.
 752   short* pack_2_ints_to(short* p, jint x0, jint x1) {
 753     // Format is one of:  [] [x y?] [Xx Y?y]
 754     if (x0 == 0 && x1 == 0) {
 755       // no halfwords needed to store zeroes
 756     } else if (is_short(x0) && is_short(x1)) {
 757       // 1-2 halfwords needed to store shorts
 758       p = add_short(p, (short)x0); if (x1!=0) p = add_short(p, (short)x1);
 759     } else {
 760       // 3-4 halfwords needed to store jints
 761       p = add_jint(p, x0);             p = add_var_int(p, x1);
 762     }
 763     return p;
 764   }
 765   void unpack_2_ints(jint& x0, jint& x1) {
 766     int    dlen = datalen();
 767     short* dp  = data();
 768     if (dlen <= 2) {
 769       x0 = relocInfo::short_data_at(0, dp, dlen);
 770       x1 = relocInfo::short_data_at(1, dp, dlen);
 771     } else {
 772       assert(dlen <= 4, "too much data");
 773       x0 = relocInfo::jint_data_at(0, dp, dlen);
 774       x1 = relocInfo::jint_data_at(2, dp, dlen);
 775     }
 776   }
 777 
 778  protected:
 779   // platform-independent utility for patching constant section
 780   void       const_set_data_value    (address x);
 781   void       const_verify_data_value (address x);
 782   // platform-dependent utilities for decoding and patching instructions
 783   void       pd_set_data_value       (address x, bool verify_only = false); // a set or mem-ref
 784   void       pd_verify_data_value    (address x) { pd_set_data_value(x, true); }
 785   address    pd_call_destination     (address orig_addr = nullptr);
 786   void       pd_set_call_destination (address x);
 787 
 788   // this extracts the address of an address in the code stream instead of the reloc data
 789   address* pd_address_in_code       ();
 790 
 791   // this extracts an address from the code stream instead of the reloc data
 792   address  pd_get_address_from_code ();
 793 
 794   // these convert from byte offsets, to scaled offsets, to addresses
 795   static jint scaled_offset(address x, address base) {
 796     int byte_offset = checked_cast<int>(x - base);
 797     int offset = -byte_offset / relocInfo::addr_unit();
 798     assert(address_from_scaled_offset(offset, base) == x, "just checkin'");
 799     return offset;
 800   }
 801   static jint scaled_offset_null_special(address x, address base) {
 802     // Some relocations treat offset=0 as meaning nullptr.
 803     // Handle this extra convention carefully.
 804     if (x == nullptr)  return 0;
 805     assert(x != base, "offset must not be zero");
 806     return scaled_offset(x, base);
 807   }
 808   static address address_from_scaled_offset(jint offset, address base) {
 809     int byte_offset = -( offset * relocInfo::addr_unit() );
 810     return base + byte_offset;
 811   }
 812 
 813   // helpers for mapping between old and new addresses after a move or resize
 814   address old_addr_for(address newa, const CodeBuffer* src, CodeBuffer* dest);
 815   address new_addr_for(address olda, const CodeBuffer* src, CodeBuffer* dest);
 816   void normalize_address(address& addr, const CodeSection* dest, bool allow_other_sections = false);
 817 
 818  public:
 819   // accessors which only make sense for a bound Relocation
 820   address         addr()            const { return binding()->addr(); }
 821   nmethod*        code()            const { return binding()->code(); }
 822   bool            addr_in_const()   const { return binding()->addr_in_const(); }
 823  protected:
 824   short*   data()         const { return binding()->data(); }
 825   int      datalen()      const { return binding()->datalen(); }
 826 
 827  public:
 828   // Make a filler relocation.
 829   Relocation() : Relocation(relocInfo::none) {}
 830 
 831   // Intentionally public non-virtual destructor, even though polymorphic.  We
 832   // never heap allocate a Relocation, so never delete through a base pointer.
 833   // RelocationHolder depends on the destructor for all relocation types being
 834   // trivial, so this must not be virtual (and hence non-trivial).
 835   ~Relocation() = default;
 836 
 837   int      format()       const { return binding()->format(); }
 838 
 839   relocInfo::relocType type()              const { return _rtype; }
 840 
 841   // Copy this relocation into holder.
 842   virtual void copy_into(RelocationHolder& holder) const;
 843 
 844   // is it a call instruction?
 845   virtual bool is_call()                         { return false; }
 846 
 847   // is it a data movement instruction?
 848   virtual bool is_data()                         { return false; }
 849 
 850   // some relocations can compute their own values
 851   virtual address  value();
 852 
 853   // all relocations are able to reassert their values
 854   virtual void set_value(address x);
 855 
 856   virtual void clear_inline_cache() {}
 857 
 858   // This method assumes that all virtual/static (inline) caches are cleared (since for static_call_type and
 859   // ic_call_type is not always position dependent (depending on the state of the cache)). However, this is
 860   // probably a reasonable assumption, since empty caches simplifies code reloacation.
 861   virtual void fix_relocation_after_move(const CodeBuffer* src, CodeBuffer* dest) { }
 862 };
 863 
 864 
 865 // certain inlines must be deferred until class Relocation is defined:
 866 
 867 inline RelocationHolder::RelocationHolder() :
 868   RelocationHolder(Construct<Relocation>())
 869 {}
 870 
 871 inline RelocationHolder::RelocationHolder(const RelocationHolder& from) {
 872   from.reloc()->copy_into(*this);
 873 }
 874 
 875 inline RelocationHolder& RelocationHolder::operator=(const RelocationHolder& from) {
 876   // All Relocation types are trivially destructible (verified in .cpp file),
 877   // so we don't need to destruct our old value before copying over it.
 878   // If not for that we would need to decide what to do about self-assignment.
 879   from.reloc()->copy_into(*this);
 880   return *this;
 881 }
 882 
 883 relocInfo::relocType RelocationHolder::type() const {
 884   return reloc()->type();
 885 }
 886 
 887 // A DataRelocation always points at a memory or load-constant instruction..
 888 // It is absolute on most machines, and the constant is split on RISCs.
 889 // The specific subtypes are oop, external_word, and internal_word.
 890 class DataRelocation : public Relocation {
 891  public:
 892   DataRelocation(relocInfo::relocType type) : Relocation(type) {}
 893 
 894   bool    is_data() override { return true; }
 895 
 896   // target must be computed somehow from relocation data
 897   address value() override = 0;
 898   void    set_value(address x) override {
 899     if (addr_in_const()) {
 900       const_set_data_value(x);
 901     } else {
 902       pd_set_data_value(x);
 903     }
 904   }
 905   void    verify_value(address x) {
 906     if (addr_in_const()) {
 907       const_verify_data_value(x);
 908     } else {
 909       pd_verify_data_value(x);
 910     }
 911   }
 912 };
 913 
 914 class post_call_nop_Relocation : public Relocation {
 915   friend class RelocationHolder;
 916 
 917 public:
 918   post_call_nop_Relocation() : Relocation(relocInfo::post_call_nop_type) { }
 919 
 920   static RelocationHolder spec() {
 921     return RelocationHolder::construct<post_call_nop_Relocation>();
 922   }
 923 
 924   void copy_into(RelocationHolder& holder) const override;
 925 };
 926 
 927 class entry_guard_Relocation : public Relocation {
 928   friend class RelocationHolder;
 929 
 930 public:
 931   entry_guard_Relocation() : Relocation(relocInfo::entry_guard_type) { }
 932 
 933   static RelocationHolder spec() {
 934     return RelocationHolder::construct<entry_guard_Relocation>();
 935   }
 936 
 937   void copy_into(RelocationHolder& holder) const override;
 938 };
 939 
 940 // A CallRelocation always points at a call instruction.
 941 // It is PC-relative on most machines.
 942 class CallRelocation : public Relocation {
 943  public:
 944   CallRelocation(relocInfo::relocType type) : Relocation(type) { }
 945 
 946   bool is_call() override { return true; }
 947 
 948   address  destination()                    { return pd_call_destination(); }
 949   void     set_destination(address x); // pd_set_call_destination
 950 
 951   void     fix_relocation_after_move(const CodeBuffer* src, CodeBuffer* dest) override;
 952   address  value() override                 { return destination();  }
 953   void     set_value(address x) override    { set_destination(x); }
 954 };
 955 
 956 class oop_Relocation : public DataRelocation {
 957  public:
 958   // an oop in the CodeBlob's oop pool; encoded as [n] or [Nn]
 959   static RelocationHolder spec(int oop_index) {
 960     assert(oop_index > 0, "must be a pool-resident oop");
 961     return RelocationHolder::construct<oop_Relocation>(oop_index);
 962   }
 963   // an oop in the instruction stream; encoded as []
 964   static RelocationHolder spec_for_immediate() {
 965     // If no immediate oops are generated, we can skip some walks over nmethods.
 966     // Assert that they don't get generated accidentally!
 967     assert(relocInfo::mustIterateImmediateOopsInCode(),
 968            "Must return true so we will search for oops as roots etc. in the code.");
 969     const int oop_index = 0;
 970     return RelocationHolder::construct<oop_Relocation>(oop_index);
 971   }
 972 
 973   void copy_into(RelocationHolder& holder) const override;
 974 
 975  private:
 976   jint _oop_index;                  // if > 0, index into CodeBlob::oop_at
 977 
 978   oop_Relocation(int oop_index)
 979     : DataRelocation(relocInfo::oop_type), _oop_index(oop_index) { }
 980 
 981   friend class RelocationHolder;
 982   oop_Relocation() : DataRelocation(relocInfo::oop_type) {}
 983 
 984  public:
 985   int oop_index() { return _oop_index; }
 986 
 987   // oop_index is packed in "1_int" format:  [n] or [Nn]
 988   void pack_data_to(CodeSection* dest) override;
 989   void unpack_data() override;
 990 
 991   void fix_oop_relocation();        // reasserts oop value
 992 
 993   void verify_oop_relocation();
 994 
 995   address value() override { return *reinterpret_cast<address*>(oop_addr()); }
 996 
 997   bool oop_is_immediate()  { return oop_index() == 0; }
 998 
 999   oop* oop_addr();                  // addr or &pool[jint_data]
1000   oop  oop_value();                 // *oop_addr
1001   // Note:  oop_value transparently converts Universe::non_oop_word to nullptr.
1002 };
1003 
1004 
1005 // copy of oop_Relocation for now but may delete stuff in both/either
1006 class metadata_Relocation : public DataRelocation {
1007 
1008  public:
1009   // an metadata in the CodeBlob's metadata pool; encoded as [n] or [Nn]
1010   static RelocationHolder spec(int metadata_index) {
1011     assert(metadata_index > 0, "must be a pool-resident metadata");
1012     return RelocationHolder::construct<metadata_Relocation>(metadata_index);
1013   }
1014   // an metadata in the instruction stream; encoded as []
1015   static RelocationHolder spec_for_immediate() {
1016     const int metadata_index = 0;
1017     return RelocationHolder::construct<metadata_Relocation>(metadata_index);
1018   }
1019 
1020   void copy_into(RelocationHolder& holder) const override;
1021 
1022  private:
1023   jint _metadata_index;            // if > 0, index into nmethod::metadata_at
1024 
1025   metadata_Relocation(int metadata_index)
1026     : DataRelocation(relocInfo::metadata_type), _metadata_index(metadata_index) { }
1027 
1028   friend class RelocationHolder;
1029   metadata_Relocation() : DataRelocation(relocInfo::metadata_type) { }
1030 
1031   // Fixes a Metadata pointer in the code. Most platforms embeds the
1032   // Metadata pointer in the code at compile time so this is empty
1033   // for them.
1034   void pd_fix_value(address x);
1035 
1036  public:
1037   int metadata_index() { return _metadata_index; }
1038 
1039   // metadata_index is packed in "1_int" format:  [n] or [Nn]
1040   void pack_data_to(CodeSection* dest) override;
1041   void unpack_data() override;
1042 
1043   void fix_metadata_relocation();        // reasserts metadata value
1044 
1045   address value() override { return (address) *metadata_addr(); }
1046 
1047   bool metadata_is_immediate()  { return metadata_index() == 0; }
1048 
1049   Metadata**   metadata_addr();                  // addr or &pool[jint_data]
1050   Metadata*    metadata_value();                 // *metadata_addr
1051   // Note:  metadata_value transparently converts Universe::non_metadata_word to nullptr.
1052 };
1053 
1054 
1055 class barrier_Relocation : public Relocation {
1056 
1057  public:
1058   // The uninitialized value used before the relocation has been patched.
1059   // Code assumes that the unpatched value is zero.
1060   static const int16_t unpatched = 0;
1061 
1062   static RelocationHolder spec() {
1063     return RelocationHolder::construct<barrier_Relocation>();
1064   }
1065 
1066   void copy_into(RelocationHolder& holder) const override;
1067 
1068  private:
1069   friend class RelocIterator;
1070   friend class RelocationHolder;
1071   barrier_Relocation() : Relocation(relocInfo::barrier_type) { }
1072 };
1073 
1074 
1075 class virtual_call_Relocation : public CallRelocation {
1076 
1077  public:
1078   // "cached_value" points to the first associated set-oop.
1079   // The oop_limit helps find the last associated set-oop.
1080   // (See comments at the top of this file.)
1081   static RelocationHolder spec(address cached_value, jint method_index = 0) {
1082     return RelocationHolder::construct<virtual_call_Relocation>(cached_value, method_index);
1083   }
1084 
1085   void copy_into(RelocationHolder& holder) const override;
1086 
1087  private:
1088   address _cached_value; // location of set-value instruction
1089   jint    _method_index; // resolved method for a Java call
1090 
1091   virtual_call_Relocation(address cached_value, int method_index)
1092     : CallRelocation(relocInfo::virtual_call_type),
1093       _cached_value(cached_value),
1094       _method_index(method_index) {
1095     assert(cached_value != nullptr, "first oop address must be specified");
1096   }
1097 
1098   friend class RelocationHolder;
1099   virtual_call_Relocation() : CallRelocation(relocInfo::virtual_call_type) { }
1100 
1101  public:
1102   address cached_value();
1103 
1104   int     method_index() { return _method_index; }
1105   Method* method_value();
1106 
1107   // data is packed as scaled offsets in "2_ints" format:  [f l] or [Ff Ll]
1108   // oop_limit is set to 0 if the limit falls somewhere within the call.
1109   // When unpacking, a zero oop_limit is taken to refer to the end of the call.
1110   // (This has the effect of bringing in the call's delay slot on SPARC.)
1111   void pack_data_to(CodeSection* dest) override;
1112   void unpack_data() override;
1113 
1114   void clear_inline_cache() override;
1115 };
1116 
1117 
1118 class opt_virtual_call_Relocation : public CallRelocation {
1119  public:
1120   static RelocationHolder spec(int method_index = 0) {
1121     return RelocationHolder::construct<opt_virtual_call_Relocation>(method_index);
1122   }
1123 
1124   void copy_into(RelocationHolder& holder) const override;
1125 
1126  private:
1127   jint _method_index; // resolved method for a Java call
1128 
1129   opt_virtual_call_Relocation(int method_index)
1130     : CallRelocation(relocInfo::opt_virtual_call_type),
1131       _method_index(method_index) { }
1132 
1133   friend class RelocationHolder;
1134   opt_virtual_call_Relocation() : CallRelocation(relocInfo::opt_virtual_call_type) {}
1135 
1136  public:
1137   int     method_index() { return _method_index; }
1138   Method* method_value();
1139 
1140   void pack_data_to(CodeSection* dest) override;
1141   void unpack_data() override;
1142 
1143   void clear_inline_cache() override;
1144 
1145   // find the matching static_stub
1146   address static_stub();
1147 };
1148 
1149 
1150 class static_call_Relocation : public CallRelocation {
1151  public:
1152   static RelocationHolder spec(int method_index = 0) {
1153     return RelocationHolder::construct<static_call_Relocation>(method_index);
1154   }
1155 
1156   void copy_into(RelocationHolder& holder) const override;
1157 
1158  private:
1159   jint _method_index; // resolved method for a Java call
1160 
1161   static_call_Relocation(int method_index)
1162     : CallRelocation(relocInfo::static_call_type),
1163     _method_index(method_index) { }
1164 
1165   friend class RelocationHolder;
1166   static_call_Relocation() : CallRelocation(relocInfo::static_call_type) {}
1167 
1168  public:
1169   int     method_index() { return _method_index; }
1170   Method* method_value();
1171 
1172   void pack_data_to(CodeSection* dest) override;
1173   void unpack_data() override;
1174 
1175   void clear_inline_cache() override;
1176 
1177   // find the matching static_stub
1178   address static_stub();
1179 };
1180 
1181 class static_stub_Relocation : public Relocation {
1182  public:
1183   static RelocationHolder spec(address static_call) {
1184     return RelocationHolder::construct<static_stub_Relocation>(static_call);
1185   }
1186 
1187   void copy_into(RelocationHolder& holder) const override;
1188 
1189  private:
1190   address _static_call;  // location of corresponding static_call
1191 
1192   static_stub_Relocation(address static_call)
1193     : Relocation(relocInfo::static_stub_type),
1194       _static_call(static_call) { }
1195 
1196   friend class RelocationHolder;
1197   static_stub_Relocation() : Relocation(relocInfo::static_stub_type) { }
1198 
1199  public:
1200   void clear_inline_cache() override;
1201 
1202   address static_call() { return _static_call; }
1203 
1204   // data is packed as a scaled offset in "1_int" format:  [c] or [Cc]
1205   void pack_data_to(CodeSection* dest) override;
1206   void unpack_data() override;
1207 };
1208 
1209 class runtime_call_Relocation : public CallRelocation {
1210 
1211  public:
1212   static RelocationHolder spec() {
1213     return RelocationHolder::construct<runtime_call_Relocation>();
1214   }
1215 
1216   void copy_into(RelocationHolder& holder) const override;
1217 
1218  private:
1219   friend class RelocationHolder;
1220   runtime_call_Relocation() : CallRelocation(relocInfo::runtime_call_type) { }
1221 };
1222 
1223 
1224 class runtime_call_w_cp_Relocation : public CallRelocation {
1225  public:
1226   static RelocationHolder spec() {
1227     return RelocationHolder::construct<runtime_call_w_cp_Relocation>();
1228   }
1229 
1230   void copy_into(RelocationHolder& holder) const override;
1231 
1232  private:
1233   friend class RelocationHolder;
1234   runtime_call_w_cp_Relocation()
1235     : CallRelocation(relocInfo::runtime_call_w_cp_type),
1236       _offset(-4) /* <0 = invalid */ { }
1237 
1238   // On z/Architecture, runtime calls are either a sequence
1239   // of two instructions (load destination of call from constant pool + do call)
1240   // or a pc-relative call. The pc-relative call is faster, but it can only
1241   // be used if the destination of the call is not too far away.
1242   // In order to be able to patch a pc-relative call back into one using
1243   // the constant pool, we have to remember the location of the call's destination
1244   // in the constant pool.
1245   int _offset;
1246 
1247  public:
1248   void set_constant_pool_offset(int offset) { _offset = offset; }
1249   int get_constant_pool_offset() { return _offset; }
1250   void pack_data_to(CodeSection * dest) override;
1251   void unpack_data() override;
1252 };
1253 
1254 // Trampoline Relocations.
1255 // A trampoline allows to encode a small branch in the code, even if there
1256 // is the chance that this branch can not reach all possible code locations.
1257 // If the relocation finds that a branch is too far for the instruction
1258 // in the code, it can patch it to jump to the trampoline where is
1259 // sufficient space for a far branch. Needed on PPC.
1260 class trampoline_stub_Relocation : public Relocation {
1261 #ifdef USE_TRAMPOLINE_STUB_FIX_OWNER
1262   void pd_fix_owner_after_move();
1263   void fix_relocation_after_move(const CodeBuffer* src, CodeBuffer* dest) override;
1264 #endif
1265 
1266  public:
1267   static RelocationHolder spec(address static_call) {
1268     return RelocationHolder::construct<trampoline_stub_Relocation>(static_call);
1269   }
1270 
1271   void copy_into(RelocationHolder& holder) const override;
1272 
1273  private:
1274   address _owner;    // Address of the NativeCall that owns the trampoline.
1275 
1276   trampoline_stub_Relocation(address owner)
1277     : Relocation(relocInfo::trampoline_stub_type),
1278       _owner(owner) { }
1279 
1280   friend class RelocationHolder;
1281   trampoline_stub_Relocation() : Relocation(relocInfo::trampoline_stub_type) { }
1282 
1283  public:
1284 
1285   // Return the address of the NativeCall that owns the trampoline.
1286   address owner() { return _owner; }
1287 
1288   void pack_data_to(CodeSection * dest) override;
1289   void unpack_data() override;
1290 
1291   // Find the trampoline stub for a call.
1292   static address get_trampoline_for(address call, nmethod* code);
1293 };
1294 
1295 class external_word_Relocation : public DataRelocation {
1296  public:
1297   static RelocationHolder spec(address target) {
1298     assert(target != nullptr, "must not be null");
1299     return RelocationHolder::construct<external_word_Relocation>(target);
1300   }
1301 
1302   // Use this one where all 32/64 bits of the target live in the code stream.
1303   // The target must be an intptr_t, and must be absolute (not relative).
1304   static RelocationHolder spec_for_immediate() {
1305     return RelocationHolder::construct<external_word_Relocation>(nullptr);
1306   }
1307 
1308   void copy_into(RelocationHolder& holder) const override;
1309 
1310   // Some address looking values aren't safe to treat as relocations
1311   // and should just be treated as constants.
1312   static bool can_be_relocated(address target) {
1313     assert(target == nullptr || (uintptr_t)target >= (uintptr_t)OSInfo::vm_page_size(), INTPTR_FORMAT, (intptr_t)target);
1314     return target != nullptr;
1315   }
1316 
1317  private:
1318   address _target;                  // address in runtime
1319 
1320   external_word_Relocation(address target)
1321     : DataRelocation(relocInfo::external_word_type), _target(target) { }
1322 
1323   friend class RelocationHolder;
1324   external_word_Relocation() : DataRelocation(relocInfo::external_word_type) { }
1325 
1326  public:
1327   // data is packed as a well-known address in "1_int" format:  [a] or [Aa]
1328   // The function runtime_address_to_index is used to turn full addresses
1329   // to short indexes, if they are pre-registered by the stub mechanism.
1330   // If the "a" value is 0 (i.e., _target is nullptr), the address is stored
1331   // in the code stream.  See external_word_Relocation::target().
1332   void pack_data_to(CodeSection* dest) override;
1333   void unpack_data() override;
1334 
1335   void fix_relocation_after_move(const CodeBuffer* src, CodeBuffer* dest) override;
1336   address  target();        // if _target==nullptr, fetch addr from code stream
1337   address  value() override { return target(); }
1338 };
1339 
1340 class internal_word_Relocation : public DataRelocation {
1341 
1342  public:
1343   static RelocationHolder spec(address target) {
1344     assert(target != nullptr, "must not be null");
1345     return RelocationHolder::construct<internal_word_Relocation>(target);
1346   }
1347 
1348   // use this one where all the bits of the target can fit in the code stream:
1349   static RelocationHolder spec_for_immediate() {
1350     return RelocationHolder::construct<internal_word_Relocation>(nullptr);
1351   }
1352 
1353   void copy_into(RelocationHolder& holder) const override;
1354 
1355   // default section -1 means self-relative
1356   internal_word_Relocation(address target, int section = -1,
1357     relocInfo::relocType type = relocInfo::internal_word_type)
1358     : DataRelocation(type), _target(target), _section(section) { }
1359 
1360  protected:
1361   address _target;                  // address in CodeBlob
1362   int     _section;                 // section providing base address, if any
1363 
1364   friend class RelocationHolder;
1365   internal_word_Relocation(relocInfo::relocType type = relocInfo::internal_word_type)
1366     : DataRelocation(type) { }
1367 
1368   // bit-width of LSB field in packed offset, if section >= 0
1369   enum { section_width = 2 }; // must equal CodeBuffer::sect_bits
1370 
1371  public:
1372   // data is packed as a scaled offset in "1_int" format:  [o] or [Oo]
1373   // If the "o" value is 0 (i.e., _target is nullptr), the offset is stored
1374   // in the code stream.  See internal_word_Relocation::target().
1375   // If _section is not -1, it is appended to the low bits of the offset.
1376   void pack_data_to(CodeSection* dest) override;
1377   void unpack_data() override;
1378 
1379   void fix_relocation_after_move(const CodeBuffer* src, CodeBuffer* dest) override;
1380   address  target();        // if _target==nullptr, fetch addr from code stream
1381   int      section()        { return _section;   }
1382   address  value() override { return target();   }
1383 };
1384 
1385 class section_word_Relocation : public internal_word_Relocation {
1386  public:
1387   static RelocationHolder spec(address target, int section) {
1388     return RelocationHolder::construct<section_word_Relocation>(target, section);
1389   }
1390 
1391   void copy_into(RelocationHolder& holder) const override;
1392 
1393   section_word_Relocation(address target, int section)
1394     : internal_word_Relocation(target, section, relocInfo::section_word_type) {
1395     assert(target != nullptr, "must not be null");
1396     assert(section >= 0 && section < RelocIterator::SECT_LIMIT, "must be a valid section");
1397   }
1398 
1399   //void pack_data_to -- inherited
1400   void unpack_data() override;
1401 
1402  private:
1403   friend class RelocationHolder;
1404   section_word_Relocation() : internal_word_Relocation(relocInfo::section_word_type) { }
1405 };
1406 
1407 
1408 class poll_Relocation : public Relocation {
1409   bool is_data() override { return true; }
1410   void fix_relocation_after_move(const CodeBuffer* src, CodeBuffer* dest) override;
1411  public:
1412   poll_Relocation(relocInfo::relocType type = relocInfo::poll_type) : Relocation(type) { }
1413 
1414   void copy_into(RelocationHolder& holder) const override;
1415 };
1416 
1417 class poll_return_Relocation : public poll_Relocation {
1418  public:
1419   poll_return_Relocation() : poll_Relocation(relocInfo::relocInfo::poll_return_type) { }
1420 
1421   void copy_into(RelocationHolder& holder) const override;
1422 };
1423 
1424 // We know all the xxx_Relocation classes, so now we can define these:
1425 #define EACH_CASE_AUX(Accessor, Reloc)                                  \
1426 inline Reloc* RelocIterator::Accessor() {                               \
1427   static const RelocationHolder proto = RelocationHolder::construct<Reloc>(); \
1428   assert(type() == proto.type(), "type must agree");                    \
1429   _rh = proto;                                                          \
1430   Reloc* r = static_cast<Reloc*>(_rh.reloc());                          \
1431   r->set_binding(this);                                                 \
1432   r->Reloc::unpack_data();                                              \
1433   return r;                                                             \
1434 }
1435 #define EACH_CASE(name) \
1436   EACH_CASE_AUX(PASTE_TOKENS(name, _reloc), PASTE_TOKENS(name, _Relocation))
1437 APPLY_TO_RELOCATIONS(EACH_CASE);
1438 #undef EACH_CASE_AUX
1439 #undef EACH_CASE
1440 
1441 inline RelocIterator::RelocIterator(nmethod* nm, address begin, address limit) {
1442   initialize(nm, begin, limit);
1443 }
1444 
1445 #endif // SHARE_CODE_RELOCINFO_HPP