1 /*
2 * Copyright (c) 1997, 2010, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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24
25 #ifndef SHARE_VM_CODE_RELOCINFO_HPP
26 #define SHARE_VM_CODE_RELOCINFO_HPP
27
28 #include "memory/allocation.hpp"
29 #include "utilities/top.hpp"
30
31 // Types in this file:
32 // relocInfo
33 // One element of an array of halfwords encoding compressed relocations.
34 // Also, the source of relocation types (relocInfo::oop_type, ...).
35 // Relocation
36 // A flyweight object representing a single relocation.
37 // It is fully unpacked from the compressed relocation array.
38 // oop_Relocation, ... (subclasses of Relocation)
39 // The location of some type-specific operations (oop_addr, ...).
40 // Also, the source of relocation specs (oop_Relocation::spec, ...).
41 // RelocationHolder
42 // A ValueObj type which acts as a union holding a Relocation object.
43 // Represents a relocation spec passed into a CodeBuffer during assembly.
44 // RelocIterator
45 // A StackObj which iterates over the relocations associated with
46 // a range of code addresses. Can be used to operate a copy of code.
47 // PatchingRelocIterator
48 // Specialized subtype of RelocIterator which removes breakpoints
49 // temporarily during iteration, then restores them.
50 // BoundRelocation
51 // An _internal_ type shared by packers and unpackers of relocations.
52 // It pastes together a RelocationHolder with some pointers into
53 // code and relocInfo streams.
54
55
56 // Notes on relocType:
57 //
58 // These hold enough information to read or write a value embedded in
59 // the instructions of an CodeBlob. They're used to update:
60 //
61 // 1) embedded oops (isOop() == true)
62 // 2) inline caches (isIC() == true)
63 // 3) runtime calls (isRuntimeCall() == true)
64 // 4) internal word ref (isInternalWord() == true)
65 // 5) external word ref (isExternalWord() == true)
66 //
67 // when objects move (GC) or if code moves (compacting the code heap).
68 // They are also used to patch the code (if a call site must change)
69 //
70 // A relocInfo is represented in 16 bits:
71 // 4 bits indicating the relocation type
72 // 12 bits indicating the offset from the previous relocInfo address
73 //
74 // The offsets accumulate along the relocInfo stream to encode the
75 // address within the CodeBlob, which is named RelocIterator::addr().
76 // The address of a particular relocInfo always points to the first
77 // byte of the relevant instruction (and not to any of its subfields
78 // or embedded immediate constants).
79 //
80 // The offset value is scaled appropriately for the target machine.
81 // (See relocInfo_<arch>.hpp for the offset scaling.)
82 //
83 // On some machines, there may also be a "format" field which may provide
84 // additional information about the format of the instruction stream
85 // at the corresponding code address. The format value is usually zero.
86 // Any machine (such as Intel) whose instructions can sometimes contain
87 // more than one relocatable constant needs format codes to distinguish
88 // which operand goes with a given relocation.
89 //
90 // If the target machine needs N format bits, the offset has 12-N bits,
91 // the format is encoded between the offset and the type, and the
92 // relocInfo_<arch>.hpp file has manifest constants for the format codes.
93 //
94 // If the type is "data_prefix_tag" then the offset bits are further encoded,
95 // and in fact represent not a code-stream offset but some inline data.
96 // The data takes the form of a counted sequence of halfwords, which
97 // precedes the actual relocation record. (Clients never see it directly.)
98 // The interpetation of this extra data depends on the relocation type.
99 //
100 // On machines that have 32-bit immediate fields, there is usually
101 // little need for relocation "prefix" data, because the instruction stream
102 // is a perfectly reasonable place to store the value. On machines in
103 // which 32-bit values must be "split" across instructions, the relocation
104 // data is the "true" specification of the value, which is then applied
105 // to some field of the instruction (22 or 13 bits, on SPARC).
106 //
107 // Whenever the location of the CodeBlob changes, any PC-relative
108 // relocations, and any internal_word_type relocations, must be reapplied.
109 // After the GC runs, oop_type relocations must be reapplied.
110 //
111 //
112 // Here are meanings of the types:
113 //
114 // relocInfo::none -- a filler record
115 // Value: none
116 // Instruction: The corresponding code address is ignored
117 // Data: Any data prefix and format code are ignored
118 // (This means that any relocInfo can be disabled by setting
119 // its type to none. See relocInfo::remove.)
120 //
121 // relocInfo::oop_type -- a reference to an oop
122 // Value: an oop, or else the address (handle) of an oop
123 // Instruction types: memory (load), set (load address)
124 // Data: [] an oop stored in 4 bytes of instruction
125 // [n] n is the index of an oop in the CodeBlob's oop pool
126 // [[N]n l] and l is a byte offset to be applied to the oop
127 // [Nn Ll] both index and offset may be 32 bits if necessary
128 // Here is a special hack, used only by the old compiler:
129 // [[N]n 00] the value is the __address__ of the nth oop in the pool
130 // (Note that the offset allows optimal references to class variables.)
131 //
132 // relocInfo::internal_word_type -- an address within the same CodeBlob
133 // relocInfo::section_word_type -- same, but can refer to another section
134 // Value: an address in the CodeBlob's code or constants section
135 // Instruction types: memory (load), set (load address)
136 // Data: [] stored in 4 bytes of instruction
137 // [[L]l] a relative offset (see [About Offsets] below)
138 // In the case of section_word_type, the offset is relative to a section
139 // base address, and the section number (e.g., SECT_INSTS) is encoded
140 // into the low two bits of the offset L.
141 //
142 // relocInfo::external_word_type -- a fixed address in the runtime system
143 // Value: an address
144 // Instruction types: memory (load), set (load address)
145 // Data: [] stored in 4 bytes of instruction
146 // [n] the index of a "well-known" stub (usual case on RISC)
147 // [Ll] a 32-bit address
148 //
149 // relocInfo::runtime_call_type -- a fixed subroutine in the runtime system
150 // Value: an address
151 // Instruction types: PC-relative call (or a PC-relative branch)
152 // Data: [] stored in 4 bytes of instruction
153 //
154 // relocInfo::static_call_type -- a static call
155 // Value: an CodeBlob, a stub, or a fixup routine
156 // Instruction types: a call
157 // Data: []
158 // The identity of the callee is extracted from debugging information.
159 // //%note reloc_3
160 //
161 // relocInfo::virtual_call_type -- a virtual call site (which includes an inline
162 // cache)
163 // Value: an CodeBlob, a stub, the interpreter, or a fixup routine
164 // Instruction types: a call, plus some associated set-oop instructions
165 // Data: [] the associated set-oops are adjacent to the call
166 // [n] n is a relative offset to the first set-oop
167 // [[N]n l] and l is a limit within which the set-oops occur
168 // [Nn Ll] both n and l may be 32 bits if necessary
169 // The identity of the callee is extracted from debugging information.
170 //
171 // relocInfo::opt_virtual_call_type -- a virtual call site that is statically bound
172 //
173 // Same info as a static_call_type. We use a special type, so the handling of
174 // virtuals and statics are separated.
175 //
176 //
177 // The offset n points to the first set-oop. (See [About Offsets] below.)
178 // In turn, the set-oop instruction specifies or contains an oop cell devoted
179 // exclusively to the IC call, which can be patched along with the call.
180 //
181 // The locations of any other set-oops are found by searching the relocation
182 // information starting at the first set-oop, and continuing until all
183 // relocations up through l have been inspected. The value l is another
184 // relative offset. (Both n and l are relative to the call's first byte.)
185 //
186 // The limit l of the search is exclusive. However, if it points within
187 // the call (e.g., offset zero), it is adjusted to point after the call and
188 // any associated machine-specific delay slot.
189 //
190 // Since the offsets could be as wide as 32-bits, these conventions
191 // put no restrictions whatever upon code reorganization.
192 //
193 // The compiler is responsible for ensuring that transition from a clean
194 // state to a monomorphic compiled state is MP-safe. This implies that
195 // the system must respond well to intermediate states where a random
196 // subset of the set-oops has been correctly from the clean state
197 // upon entry to the VEP of the compiled method. In the case of a
198 // machine (Intel) with a single set-oop instruction, the 32-bit
199 // immediate field must not straddle a unit of memory coherence.
200 // //%note reloc_3
201 //
202 // relocInfo::breakpoint_type -- a conditional breakpoint in the code
203 // Value: none
204 // Instruction types: any whatsoever
205 // Data: [b [T]t i...]
206 // The b is a bit-packed word representing the breakpoint's attributes.
207 // The t is a target address which the breakpoint calls (when it is enabled).
208 // The i... is a place to store one or two instruction words overwritten
209 // by a trap, so that the breakpoint may be subsequently removed.
210 //
211 // relocInfo::static_stub_type -- an extra stub for each static_call_type
212 // Value: none
213 // Instruction types: a virtual call: { set_oop; jump; }
214 // Data: [[N]n] the offset of the associated static_call reloc
215 // This stub becomes the target of a static call which must be upgraded
216 // to a virtual call (because the callee is interpreted).
217 // See [About Offsets] below.
218 // //%note reloc_2
219 //
220 // For example:
221 //
222 // INSTRUCTIONS RELOC: TYPE PREFIX DATA
223 // ------------ ---- -----------
224 // sethi %hi(myObject), R oop_type [n(myObject)]
225 // ld [R+%lo(myObject)+fldOffset], R2 oop_type [n(myObject) fldOffset]
226 // add R2, 1, R2
227 // st R2, [R+%lo(myObject)+fldOffset] oop_type [n(myObject) fldOffset]
228 //%note reloc_1
229 //
230 // This uses 4 instruction words, 8 relocation halfwords,
231 // and an entry (which is sharable) in the CodeBlob's oop pool,
232 // for a total of 36 bytes.
233 //
234 // Note that the compiler is responsible for ensuring the "fldOffset" when
235 // added to "%lo(myObject)" does not overflow the immediate fields of the
236 // memory instructions.
237 //
238 //
239 // [About Offsets] Relative offsets are supplied to this module as
240 // positive byte offsets, but they may be internally stored scaled
241 // and/or negated, depending on what is most compact for the target
242 // system. Since the object pointed to by the offset typically
243 // precedes the relocation address, it is profitable to store
244 // these negative offsets as positive numbers, but this decision
245 // is internal to the relocation information abstractions.
246 //
247
248 class Relocation;
249 class CodeBuffer;
250 class CodeSection;
251 class RelocIterator;
252
253 class relocInfo VALUE_OBJ_CLASS_SPEC {
254 friend class RelocIterator;
255 public:
256 enum relocType {
257 none = 0, // Used when no relocation should be generated
258 oop_type = 1, // embedded oop
259 virtual_call_type = 2, // a standard inline cache call for a virtual send
260 opt_virtual_call_type = 3, // a virtual call that has been statically bound (i.e., no IC cache)
261 static_call_type = 4, // a static send
262 static_stub_type = 5, // stub-entry for static send (takes care of interpreter case)
263 runtime_call_type = 6, // call to fixed external routine
264 external_word_type = 7, // reference to fixed external address
265 internal_word_type = 8, // reference within the current code blob
266 section_word_type = 9, // internal, but a cross-section reference
267 poll_type = 10, // polling instruction for safepoints
268 poll_return_type = 11, // polling instruction for safepoints at return
269 breakpoint_type = 12, // an initialization barrier or safepoint
270 yet_unused_type = 13, // Still unused
271 yet_unused_type_2 = 14, // Still unused
272 data_prefix_tag = 15, // tag for a prefix (carries data arguments)
273 type_mask = 15 // A mask which selects only the above values
274 };
275
276 protected:
277 unsigned short _value;
278
279 enum RawBitsToken { RAW_BITS };
280 relocInfo(relocType type, RawBitsToken ignore, int bits)
281 : _value((type << nontype_width) + bits) { }
282
283 relocInfo(relocType type, RawBitsToken ignore, int off, int f)
284 : _value((type << nontype_width) + (off / (unsigned)offset_unit) + (f << offset_width)) { }
285
286 public:
287 // constructor
288 relocInfo(relocType type, int offset, int format = 0)
289 #ifndef ASSERT
290 {
291 (*this) = relocInfo(type, RAW_BITS, offset, format);
292 }
293 #else
294 // Put a bunch of assertions out-of-line.
295 ;
296 #endif
297
298 #define APPLY_TO_RELOCATIONS(visitor) \
299 visitor(oop) \
300 visitor(virtual_call) \
301 visitor(opt_virtual_call) \
302 visitor(static_call) \
303 visitor(static_stub) \
304 visitor(runtime_call) \
305 visitor(external_word) \
306 visitor(internal_word) \
307 visitor(poll) \
308 visitor(poll_return) \
309 visitor(breakpoint) \
310 visitor(section_word) \
311
312
313 public:
314 enum {
315 value_width = sizeof(unsigned short) * BitsPerByte,
316 type_width = 4, // == log2(type_mask+1)
317 nontype_width = value_width - type_width,
318 datalen_width = nontype_width-1,
319 datalen_tag = 1 << datalen_width, // or-ed into _value
320 datalen_limit = 1 << datalen_width,
321 datalen_mask = (1 << datalen_width)-1
322 };
323
324 // accessors
325 public:
326 relocType type() const { return (relocType)((unsigned)_value >> nontype_width); }
327 int format() const { return format_mask==0? 0: format_mask &
328 ((unsigned)_value >> offset_width); }
329 int addr_offset() const { assert(!is_prefix(), "must have offset");
330 return (_value & offset_mask)*offset_unit; }
331
332 protected:
333 const short* data() const { assert(is_datalen(), "must have data");
334 return (const short*)(this + 1); }
335 int datalen() const { assert(is_datalen(), "must have data");
336 return (_value & datalen_mask); }
337 int immediate() const { assert(is_immediate(), "must have immed");
338 return (_value & datalen_mask); }
339 public:
340 static int addr_unit() { return offset_unit; }
341 static int offset_limit() { return (1 << offset_width) * offset_unit; }
342
343 void set_type(relocType type);
344 void set_format(int format);
345
346 void remove() { set_type(none); }
347
348 protected:
349 bool is_none() const { return type() == none; }
350 bool is_prefix() const { return type() == data_prefix_tag; }
351 bool is_datalen() const { assert(is_prefix(), "must be prefix");
352 return (_value & datalen_tag) != 0; }
353 bool is_immediate() const { assert(is_prefix(), "must be prefix");
354 return (_value & datalen_tag) == 0; }
355
356 public:
357 // Occasionally records of type relocInfo::none will appear in the stream.
358 // We do not bother to filter these out, but clients should ignore them.
359 // These records serve as "filler" in three ways:
360 // - to skip large spans of unrelocated code (this is rare)
361 // - to pad out the relocInfo array to the required oop alignment
362 // - to disable old relocation information which is no longer applicable
363
364 inline friend relocInfo filler_relocInfo();
365
366 // Every non-prefix relocation may be preceded by at most one prefix,
367 // which supplies 1 or more halfwords of associated data. Conventionally,
368 // an int is represented by 0, 1, or 2 halfwords, depending on how
369 // many bits are required to represent the value. (In addition,
370 // if the sole halfword is a 10-bit unsigned number, it is made
371 // "immediate" in the prefix header word itself. This optimization
372 // is invisible outside this module.)
373
374 inline friend relocInfo prefix_relocInfo(int datalen = 0);
375
376 protected:
377 // an immediate relocInfo optimizes a prefix with one 10-bit unsigned value
378 static relocInfo immediate_relocInfo(int data0) {
379 assert(fits_into_immediate(data0), "data0 in limits");
380 return relocInfo(relocInfo::data_prefix_tag, RAW_BITS, data0);
381 }
382 static bool fits_into_immediate(int data0) {
383 return (data0 >= 0 && data0 < datalen_limit);
384 }
385
386 public:
387 // Support routines for compilers.
388
389 // This routine takes an infant relocInfo (unprefixed) and
390 // edits in its prefix, if any. It also updates dest.locs_end.
391 void initialize(CodeSection* dest, Relocation* reloc);
392
393 // This routine updates a prefix and returns the limit pointer.
394 // It tries to compress the prefix from 32 to 16 bits, and if
395 // successful returns a reduced "prefix_limit" pointer.
396 relocInfo* finish_prefix(short* prefix_limit);
397
398 // bit-packers for the data array:
399
400 // As it happens, the bytes within the shorts are ordered natively,
401 // but the shorts within the word are ordered big-endian.
402 // This is an arbitrary choice, made this way mainly to ease debugging.
403 static int data0_from_int(jint x) { return x >> value_width; }
404 static int data1_from_int(jint x) { return (short)x; }
405 static jint jint_from_data(short* data) {
406 return (data[0] << value_width) + (unsigned short)data[1];
407 }
408
409 static jint short_data_at(int n, short* data, int datalen) {
410 return datalen > n ? data[n] : 0;
411 }
412
413 static jint jint_data_at(int n, short* data, int datalen) {
414 return datalen > n+1 ? jint_from_data(&data[n]) : short_data_at(n, data, datalen);
415 }
416
417 // Update methods for relocation information
418 // (since code is dynamically patched, we also need to dynamically update the relocation info)
419 // Both methods takes old_type, so it is able to performe sanity checks on the information removed.
420 static void change_reloc_info_for_address(RelocIterator *itr, address pc, relocType old_type, relocType new_type);
421 static void remove_reloc_info_for_address(RelocIterator *itr, address pc, relocType old_type);
422
423 // Machine dependent stuff
424 #ifdef TARGET_ARCH_x86
425 # include "relocInfo_x86.hpp"
426 #endif
427 #ifdef TARGET_ARCH_sparc
428 # include "relocInfo_sparc.hpp"
429 #endif
430 #ifdef TARGET_ARCH_zero
431 # include "relocInfo_zero.hpp"
432 #endif
433
434
435 protected:
436 // Derived constant, based on format_width which is PD:
437 enum {
438 offset_width = nontype_width - format_width,
439 offset_mask = (1<<offset_width) - 1,
440 format_mask = (1<<format_width) - 1
441 };
442 public:
443 enum {
444 // Conservatively large estimate of maximum length (in shorts)
445 // of any relocation record (probably breakpoints are largest).
446 // Extended format is length prefix, data words, and tag/offset suffix.
447 length_limit = 1 + 1 + (3*BytesPerWord/BytesPerShort) + 1,
448 have_format = format_width > 0
449 };
450 };
451
452 #define FORWARD_DECLARE_EACH_CLASS(name) \
453 class name##_Relocation;
454 APPLY_TO_RELOCATIONS(FORWARD_DECLARE_EACH_CLASS)
455 #undef FORWARD_DECLARE_EACH_CLASS
456
457
458
459 inline relocInfo filler_relocInfo() {
460 return relocInfo(relocInfo::none, relocInfo::offset_limit() - relocInfo::offset_unit);
461 }
462
463 inline relocInfo prefix_relocInfo(int datalen) {
464 assert(relocInfo::fits_into_immediate(datalen), "datalen in limits");
465 return relocInfo(relocInfo::data_prefix_tag, relocInfo::RAW_BITS, relocInfo::datalen_tag | datalen);
466 }
467
468
469 // Holder for flyweight relocation objects.
470 // Although the flyweight subclasses are of varying sizes,
471 // the holder is "one size fits all".
472 class RelocationHolder VALUE_OBJ_CLASS_SPEC {
473 friend class Relocation;
474 friend class CodeSection;
475
476 private:
477 // this preallocated memory must accommodate all subclasses of Relocation
478 // (this number is assertion-checked in Relocation::operator new)
479 enum { _relocbuf_size = 5 };
480 void* _relocbuf[ _relocbuf_size ];
481
482 public:
483 Relocation* reloc() const { return (Relocation*) &_relocbuf[0]; }
484 inline relocInfo::relocType type() const;
485
486 // Add a constant offset to a relocation. Helper for class Address.
487 RelocationHolder plus(int offset) const;
488
489 inline RelocationHolder(); // initializes type to none
490
491 inline RelocationHolder(Relocation* r); // make a copy
492
493 static const RelocationHolder none;
494 };
495
496 // A RelocIterator iterates through the relocation information of a CodeBlob.
497 // It is a variable BoundRelocation which is able to take on successive
498 // values as it is advanced through a code stream.
499 // Usage:
500 // RelocIterator iter(nm);
501 // while (iter.next()) {
502 // iter.reloc()->some_operation();
503 // }
504 // or:
505 // RelocIterator iter(nm);
506 // while (iter.next()) {
507 // switch (iter.type()) {
508 // case relocInfo::oop_type :
509 // case relocInfo::ic_type :
510 // case relocInfo::prim_type :
511 // case relocInfo::uncommon_type :
512 // case relocInfo::runtime_call_type :
513 // case relocInfo::internal_word_type:
514 // case relocInfo::external_word_type:
515 // ...
516 // }
517 // }
518
519 class RelocIterator : public StackObj {
520 enum { SECT_LIMIT = 3 }; // must be equal to CodeBuffer::SECT_LIMIT, checked in ctor
521 friend class Relocation;
522 friend class relocInfo; // for change_reloc_info_for_address only
523 typedef relocInfo::relocType relocType;
524
525 private:
526 address _limit; // stop producing relocations after this _addr
527 relocInfo* _current; // the current relocation information
528 relocInfo* _end; // end marker; we're done iterating when _current == _end
529 nmethod* _code; // compiled method containing _addr
530 address _addr; // instruction to which the relocation applies
531 short _databuf; // spare buffer for compressed data
532 short* _data; // pointer to the relocation's data
533 short _datalen; // number of halfwords in _data
534 char _format; // position within the instruction
535
536 // Base addresses needed to compute targets of section_word_type relocs.
537 address _section_start[SECT_LIMIT];
538 address _section_end [SECT_LIMIT];
539
540 void set_has_current(bool b) {
541 _datalen = !b ? -1 : 0;
542 debug_only(_data = NULL);
543 }
544 void set_current(relocInfo& ri) {
545 _current = &ri;
546 set_has_current(true);
547 }
548
549 RelocationHolder _rh; // where the current relocation is allocated
550
551 relocInfo* current() const { assert(has_current(), "must have current");
552 return _current; }
553
554 void set_limits(address begin, address limit);
555
556 void advance_over_prefix(); // helper method
557
558 void initialize_misc();
559
560 void initialize(nmethod* nm, address begin, address limit);
561
562 friend class PatchingRelocIterator;
563 // make an uninitialized one, for PatchingRelocIterator:
564 RelocIterator() { initialize_misc(); }
565
566 public:
567 // constructor
568 RelocIterator(nmethod* nm, address begin = NULL, address limit = NULL);
569 RelocIterator(CodeSection* cb, address begin = NULL, address limit = NULL);
570
571 // get next reloc info, return !eos
572 bool next() {
573 _current++;
574 assert(_current <= _end, "must not overrun relocInfo");
575 if (_current == _end) {
576 set_has_current(false);
577 return false;
578 }
579 set_has_current(true);
580
581 if (_current->is_prefix()) {
582 advance_over_prefix();
583 assert(!current()->is_prefix(), "only one prefix at a time");
584 }
585
586 _addr += _current->addr_offset();
587
588 if (_limit != NULL && _addr >= _limit) {
589 set_has_current(false);
590 return false;
591 }
592
593 if (relocInfo::have_format) _format = current()->format();
594 return true;
595 }
596
597 // accessors
598 address limit() const { return _limit; }
599 void set_limit(address x);
600 relocType type() const { return current()->type(); }
601 int format() const { return (relocInfo::have_format) ? current()->format() : 0; }
602 address addr() const { return _addr; }
603 nmethod* code() const { return _code; }
604 short* data() const { return _data; }
605 int datalen() const { return _datalen; }
606 bool has_current() const { return _datalen >= 0; }
607
608 void set_addr(address addr) { _addr = addr; }
609 bool addr_in_const() const;
610
611 address section_start(int n) const {
612 assert(_section_start[n], "must be initialized");
613 return _section_start[n];
614 }
615 address section_end(int n) const {
616 assert(_section_end[n], "must be initialized");
617 return _section_end[n];
618 }
619
620 // The address points to the affected displacement part of the instruction.
621 // For RISC, this is just the whole instruction.
622 // For Intel, this is an unaligned 32-bit word.
623
624 // type-specific relocation accessors: oop_Relocation* oop_reloc(), etc.
625 #define EACH_TYPE(name) \
626 inline name##_Relocation* name##_reloc();
627 APPLY_TO_RELOCATIONS(EACH_TYPE)
628 #undef EACH_TYPE
629 // generic relocation accessor; switches on type to call the above
630 Relocation* reloc();
631
632 // CodeBlob's have relocation indexes for faster random access:
633 static int locs_and_index_size(int code_size, int locs_size);
634 // Store an index into [dest_start+dest_count..dest_end).
635 // At dest_start[0..dest_count] is the actual relocation information.
636 // Everything else up to dest_end is free space for the index.
637 static void create_index(relocInfo* dest_begin, int dest_count, relocInfo* dest_end);
638
639 #ifndef PRODUCT
640 public:
641 void print();
642 void print_current();
643 #endif
644 };
645
646
647 // A Relocation is a flyweight object allocated within a RelocationHolder.
648 // It represents the relocation data of relocation record.
649 // So, the RelocIterator unpacks relocInfos into Relocations.
650
651 class Relocation VALUE_OBJ_CLASS_SPEC {
652 friend class RelocationHolder;
653 friend class RelocIterator;
654
655 private:
656 static void guarantee_size();
657
658 // When a relocation has been created by a RelocIterator,
659 // this field is non-null. It allows the relocation to know
660 // its context, such as the address to which it applies.
661 RelocIterator* _binding;
662
663 protected:
664 RelocIterator* binding() const {
665 assert(_binding != NULL, "must be bound");
666 return _binding;
667 }
668 void set_binding(RelocIterator* b) {
669 assert(_binding == NULL, "must be unbound");
670 _binding = b;
671 assert(_binding != NULL, "must now be bound");
672 }
673
674 Relocation() {
675 _binding = NULL;
676 }
677
678 static RelocationHolder newHolder() {
679 return RelocationHolder();
680 }
681
682 public:
683 void* operator new(size_t size, const RelocationHolder& holder) {
684 if (size > sizeof(holder._relocbuf)) guarantee_size();
685 assert((void* const *)holder.reloc() == &holder._relocbuf[0], "ptrs must agree");
686 return holder.reloc();
687 }
688
689 // make a generic relocation for a given type (if possible)
690 static RelocationHolder spec_simple(relocInfo::relocType rtype);
691
692 // here is the type-specific hook which writes relocation data:
693 virtual void pack_data_to(CodeSection* dest) { }
694
695 // here is the type-specific hook which reads (unpacks) relocation data:
696 virtual void unpack_data() {
697 assert(datalen()==0 || type()==relocInfo::none, "no data here");
698 }
699
700 protected:
701 // Helper functions for pack_data_to() and unpack_data().
702
703 // Most of the compression logic is confined here.
704 // (The "immediate data" mechanism of relocInfo works independently
705 // of this stuff, and acts to further compress most 1-word data prefixes.)
706
707 // A variable-width int is encoded as a short if it will fit in 16 bits.
708 // The decoder looks at datalen to decide whether to unpack short or jint.
709 // Most relocation records are quite simple, containing at most two ints.
710
711 static bool is_short(jint x) { return x == (short)x; }
712 static short* add_short(short* p, int x) { *p++ = x; return p; }
713 static short* add_jint (short* p, jint x) {
714 *p++ = relocInfo::data0_from_int(x); *p++ = relocInfo::data1_from_int(x);
715 return p;
716 }
717 static short* add_var_int(short* p, jint x) { // add a variable-width int
718 if (is_short(x)) p = add_short(p, x);
719 else p = add_jint (p, x);
720 return p;
721 }
722
723 static short* pack_1_int_to(short* p, jint x0) {
724 // Format is one of: [] [x] [Xx]
725 if (x0 != 0) p = add_var_int(p, x0);
726 return p;
727 }
728 int unpack_1_int() {
729 assert(datalen() <= 2, "too much data");
730 return relocInfo::jint_data_at(0, data(), datalen());
731 }
732
733 // With two ints, the short form is used only if both ints are short.
734 short* pack_2_ints_to(short* p, jint x0, jint x1) {
735 // Format is one of: [] [x y?] [Xx Y?y]
736 if (x0 == 0 && x1 == 0) {
737 // no halfwords needed to store zeroes
738 } else if (is_short(x0) && is_short(x1)) {
739 // 1-2 halfwords needed to store shorts
740 p = add_short(p, x0); if (x1!=0) p = add_short(p, x1);
741 } else {
742 // 3-4 halfwords needed to store jints
743 p = add_jint(p, x0); p = add_var_int(p, x1);
744 }
745 return p;
746 }
747 void unpack_2_ints(jint& x0, jint& x1) {
748 int dlen = datalen();
749 short* dp = data();
750 if (dlen <= 2) {
751 x0 = relocInfo::short_data_at(0, dp, dlen);
752 x1 = relocInfo::short_data_at(1, dp, dlen);
753 } else {
754 assert(dlen <= 4, "too much data");
755 x0 = relocInfo::jint_data_at(0, dp, dlen);
756 x1 = relocInfo::jint_data_at(2, dp, dlen);
757 }
758 }
759
760 protected:
761 // platform-dependent utilities for decoding and patching instructions
762 void pd_set_data_value (address x, intptr_t off); // a set or mem-ref
763 address pd_call_destination (address orig_addr = NULL);
764 void pd_set_call_destination (address x);
765 void pd_swap_in_breakpoint (address x, short* instrs, int instrlen);
766 void pd_swap_out_breakpoint (address x, short* instrs, int instrlen);
767 static int pd_breakpoint_size ();
768
769 // this extracts the address of an address in the code stream instead of the reloc data
770 address* pd_address_in_code ();
771
772 // this extracts an address from the code stream instead of the reloc data
773 address pd_get_address_from_code ();
774
775 // these convert from byte offsets, to scaled offsets, to addresses
776 static jint scaled_offset(address x, address base) {
777 int byte_offset = x - base;
778 int offset = -byte_offset / relocInfo::addr_unit();
779 assert(address_from_scaled_offset(offset, base) == x, "just checkin'");
780 return offset;
781 }
782 static jint scaled_offset_null_special(address x, address base) {
783 // Some relocations treat offset=0 as meaning NULL.
784 // Handle this extra convention carefully.
785 if (x == NULL) return 0;
786 assert(x != base, "offset must not be zero");
787 return scaled_offset(x, base);
788 }
789 static address address_from_scaled_offset(jint offset, address base) {
790 int byte_offset = -( offset * relocInfo::addr_unit() );
791 return base + byte_offset;
792 }
793
794 // these convert between indexes and addresses in the runtime system
795 static int32_t runtime_address_to_index(address runtime_address);
796 static address index_to_runtime_address(int32_t index);
797
798 // helpers for mapping between old and new addresses after a move or resize
799 address old_addr_for(address newa, const CodeBuffer* src, CodeBuffer* dest);
800 address new_addr_for(address olda, const CodeBuffer* src, CodeBuffer* dest);
801 void normalize_address(address& addr, const CodeSection* dest, bool allow_other_sections = false);
802
803 public:
804 // accessors which only make sense for a bound Relocation
805 address addr() const { return binding()->addr(); }
806 nmethod* code() const { return binding()->code(); }
807 bool addr_in_const() const { return binding()->addr_in_const(); }
808 protected:
809 short* data() const { return binding()->data(); }
810 int datalen() const { return binding()->datalen(); }
811 int format() const { return binding()->format(); }
812
813 public:
814 virtual relocInfo::relocType type() { return relocInfo::none; }
815
816 // is it a call instruction?
817 virtual bool is_call() { return false; }
818
819 // is it a data movement instruction?
820 virtual bool is_data() { return false; }
821
822 // some relocations can compute their own values
823 virtual address value();
824
825 // all relocations are able to reassert their values
826 virtual void set_value(address x);
827
828 virtual void clear_inline_cache() { }
829
830 // This method assumes that all virtual/static (inline) caches are cleared (since for static_call_type and
831 // ic_call_type is not always posisition dependent (depending on the state of the cache)). However, this is
832 // probably a reasonable assumption, since empty caches simplifies code reloacation.
833 virtual void fix_relocation_after_move(const CodeBuffer* src, CodeBuffer* dest) { }
834
835 void print();
836 };
837
838
839 // certain inlines must be deferred until class Relocation is defined:
840
841 inline RelocationHolder::RelocationHolder() {
842 // initialize the vtbl, just to keep things type-safe
843 new(*this) Relocation();
844 }
845
846
847 inline RelocationHolder::RelocationHolder(Relocation* r) {
848 // wordwise copy from r (ok if it copies garbage after r)
849 for (int i = 0; i < _relocbuf_size; i++) {
850 _relocbuf[i] = ((void**)r)[i];
851 }
852 }
853
854
855 relocInfo::relocType RelocationHolder::type() const {
856 return reloc()->type();
857 }
858
859 // A DataRelocation always points at a memory or load-constant instruction..
860 // It is absolute on most machines, and the constant is split on RISCs.
861 // The specific subtypes are oop, external_word, and internal_word.
862 // By convention, the "value" does not include a separately reckoned "offset".
863 class DataRelocation : public Relocation {
864 public:
865 bool is_data() { return true; }
866
867 // both target and offset must be computed somehow from relocation data
868 virtual int offset() { return 0; }
869 address value() = 0;
870 void set_value(address x) { set_value(x, offset()); }
871 void set_value(address x, intptr_t o) {
872 if (addr_in_const())
873 *(address*)addr() = x;
874 else
875 pd_set_data_value(x, o);
876 }
877
878 // The "o" (displacement) argument is relevant only to split relocations
879 // on RISC machines. In some CPUs (SPARC), the set-hi and set-lo ins'ns
880 // can encode more than 32 bits between them. This allows compilers to
881 // share set-hi instructions between addresses that differ by a small
882 // offset (e.g., different static variables in the same class).
883 // On such machines, the "x" argument to set_value on all set-lo
884 // instructions must be the same as the "x" argument for the
885 // corresponding set-hi instructions. The "o" arguments for the
886 // set-hi instructions are ignored, and must not affect the high-half
887 // immediate constant. The "o" arguments for the set-lo instructions are
888 // added into the low-half immediate constant, and must not overflow it.
889 };
890
891 // A CallRelocation always points at a call instruction.
892 // It is PC-relative on most machines.
893 class CallRelocation : public Relocation {
894 public:
895 bool is_call() { return true; }
896
897 address destination() { return pd_call_destination(); }
898 void set_destination(address x); // pd_set_call_destination
899
900 void fix_relocation_after_move(const CodeBuffer* src, CodeBuffer* dest);
901 address value() { return destination(); }
902 void set_value(address x) { set_destination(x); }
903 };
904
905 class oop_Relocation : public DataRelocation {
906 relocInfo::relocType type() { return relocInfo::oop_type; }
907
908 public:
909 // encode in one of these formats: [] [n] [n l] [Nn l] [Nn Ll]
910 // an oop in the CodeBlob's oop pool
911 static RelocationHolder spec(int oop_index, int offset = 0) {
912 assert(oop_index > 0, "must be a pool-resident oop");
913 RelocationHolder rh = newHolder();
914 new(rh) oop_Relocation(oop_index, offset);
915 return rh;
916 }
917 // an oop in the instruction stream
918 static RelocationHolder spec_for_immediate() {
919 const int oop_index = 0;
920 const int offset = 0; // if you want an offset, use the oop pool
921 RelocationHolder rh = newHolder();
922 new(rh) oop_Relocation(oop_index, offset);
923 return rh;
924 }
925
926 private:
927 jint _oop_index; // if > 0, index into CodeBlob::oop_at
928 jint _offset; // byte offset to apply to the oop itself
929
930 oop_Relocation(int oop_index, int offset) {
931 _oop_index = oop_index; _offset = offset;
932 }
933
934 friend class RelocIterator;
935 oop_Relocation() { }
936
937 public:
938 int oop_index() { return _oop_index; }
939 int offset() { return _offset; }
940
941 // data is packed in "2_ints" format: [i o] or [Ii Oo]
942 void pack_data_to(CodeSection* dest);
943 void unpack_data();
944
945 void fix_oop_relocation(); // reasserts oop value
946
947 address value() { return (address) *oop_addr(); }
948
949 bool oop_is_immediate() { return oop_index() == 0; }
950
951 oop* oop_addr(); // addr or &pool[jint_data]
952 oop oop_value(); // *oop_addr
953 // Note: oop_value transparently converts Universe::non_oop_word to NULL.
954 };
955
956 class virtual_call_Relocation : public CallRelocation {
957 relocInfo::relocType type() { return relocInfo::virtual_call_type; }
958
959 public:
960 // "first_oop" points to the first associated set-oop.
961 // The oop_limit helps find the last associated set-oop.
962 // (See comments at the top of this file.)
963 static RelocationHolder spec(address first_oop, address oop_limit = NULL) {
964 RelocationHolder rh = newHolder();
965 new(rh) virtual_call_Relocation(first_oop, oop_limit);
966 return rh;
967 }
968
969 virtual_call_Relocation(address first_oop, address oop_limit) {
970 _first_oop = first_oop; _oop_limit = oop_limit;
971 assert(first_oop != NULL, "first oop address must be specified");
972 }
973
974 private:
975 address _first_oop; // location of first set-oop instruction
976 address _oop_limit; // search limit for set-oop instructions
977
978 friend class RelocIterator;
979 virtual_call_Relocation() { }
980
981
982 public:
983 address first_oop();
984 address oop_limit();
985
986 // data is packed as scaled offsets in "2_ints" format: [f l] or [Ff Ll]
987 // oop_limit is set to 0 if the limit falls somewhere within the call.
988 // When unpacking, a zero oop_limit is taken to refer to the end of the call.
989 // (This has the effect of bringing in the call's delay slot on SPARC.)
990 void pack_data_to(CodeSection* dest);
991 void unpack_data();
992
993 void clear_inline_cache();
994
995 // Figure out where an ic_call is hiding, given a set-oop or call.
996 // Either ic_call or first_oop must be non-null; the other is deduced.
997 // Code if non-NULL must be the nmethod, else it is deduced.
998 // The address of the patchable oop is also deduced.
999 // The returned iterator will enumerate over the oops and the ic_call,
1000 // as well as any other relocations that happen to be in that span of code.
1001 // Recognize relevant set_oops with: oop_reloc()->oop_addr() == oop_addr.
1002 static RelocIterator parse_ic(nmethod* &nm, address &ic_call, address &first_oop, oop* &oop_addr, bool *is_optimized);
1003 };
1004
1005
1006 class opt_virtual_call_Relocation : public CallRelocation {
1007 relocInfo::relocType type() { return relocInfo::opt_virtual_call_type; }
1008
1009 public:
1010 static RelocationHolder spec() {
1011 RelocationHolder rh = newHolder();
1012 new(rh) opt_virtual_call_Relocation();
1013 return rh;
1014 }
1015
1016 private:
1017 friend class RelocIterator;
1018 opt_virtual_call_Relocation() { }
1019
1020 public:
1021 void clear_inline_cache();
1022
1023 // find the matching static_stub
1024 address static_stub();
1025 };
1026
1027
1028 class static_call_Relocation : public CallRelocation {
1029 relocInfo::relocType type() { return relocInfo::static_call_type; }
1030
1031 public:
1032 static RelocationHolder spec() {
1033 RelocationHolder rh = newHolder();
1034 new(rh) static_call_Relocation();
1035 return rh;
1036 }
1037
1038 private:
1039 friend class RelocIterator;
1040 static_call_Relocation() { }
1041
1042 public:
1043 void clear_inline_cache();
1044
1045 // find the matching static_stub
1046 address static_stub();
1047 };
1048
1049 class static_stub_Relocation : public Relocation {
1050 relocInfo::relocType type() { return relocInfo::static_stub_type; }
1051
1052 public:
1053 static RelocationHolder spec(address static_call) {
1054 RelocationHolder rh = newHolder();
1055 new(rh) static_stub_Relocation(static_call);
1056 return rh;
1057 }
1058
1059 private:
1060 address _static_call; // location of corresponding static_call
1061
1062 static_stub_Relocation(address static_call) {
1063 _static_call = static_call;
1064 }
1065
1066 friend class RelocIterator;
1067 static_stub_Relocation() { }
1068
1069 public:
1070 void clear_inline_cache();
1071
1072 address static_call() { return _static_call; }
1073
1074 // data is packed as a scaled offset in "1_int" format: [c] or [Cc]
1075 void pack_data_to(CodeSection* dest);
1076 void unpack_data();
1077 };
1078
1079 class runtime_call_Relocation : public CallRelocation {
1080 relocInfo::relocType type() { return relocInfo::runtime_call_type; }
1081
1082 public:
1083 static RelocationHolder spec() {
1084 RelocationHolder rh = newHolder();
1085 new(rh) runtime_call_Relocation();
1086 return rh;
1087 }
1088
1089 private:
1090 friend class RelocIterator;
1091 runtime_call_Relocation() { }
1092
1093 public:
1094 };
1095
1096 class external_word_Relocation : public DataRelocation {
1097 relocInfo::relocType type() { return relocInfo::external_word_type; }
1098
1099 public:
1100 static RelocationHolder spec(address target) {
1101 assert(target != NULL, "must not be null");
1102 RelocationHolder rh = newHolder();
1103 new(rh) external_word_Relocation(target);
1104 return rh;
1105 }
1106
1107 // Use this one where all 32/64 bits of the target live in the code stream.
1108 // The target must be an intptr_t, and must be absolute (not relative).
1109 static RelocationHolder spec_for_immediate() {
1110 RelocationHolder rh = newHolder();
1111 new(rh) external_word_Relocation(NULL);
1112 return rh;
1113 }
1114
1115 private:
1116 address _target; // address in runtime
1117
1118 external_word_Relocation(address target) {
1119 _target = target;
1120 }
1121
1122 friend class RelocIterator;
1123 external_word_Relocation() { }
1124
1125 public:
1126 // data is packed as a well-known address in "1_int" format: [a] or [Aa]
1127 // The function runtime_address_to_index is used to turn full addresses
1128 // to short indexes, if they are pre-registered by the stub mechanism.
1129 // If the "a" value is 0 (i.e., _target is NULL), the address is stored
1130 // in the code stream. See external_word_Relocation::target().
1131 void pack_data_to(CodeSection* dest);
1132 void unpack_data();
1133
1134 void fix_relocation_after_move(const CodeBuffer* src, CodeBuffer* dest);
1135 address target(); // if _target==NULL, fetch addr from code stream
1136 address value() { return target(); }
1137 };
1138
1139 class internal_word_Relocation : public DataRelocation {
1140 relocInfo::relocType type() { return relocInfo::internal_word_type; }
1141
1142 public:
1143 static RelocationHolder spec(address target) {
1144 assert(target != NULL, "must not be null");
1145 RelocationHolder rh = newHolder();
1146 new(rh) internal_word_Relocation(target);
1147 return rh;
1148 }
1149
1150 // use this one where all the bits of the target can fit in the code stream:
1151 static RelocationHolder spec_for_immediate() {
1152 RelocationHolder rh = newHolder();
1153 new(rh) internal_word_Relocation(NULL);
1154 return rh;
1155 }
1156
1157 internal_word_Relocation(address target) {
1158 _target = target;
1159 _section = -1; // self-relative
1160 }
1161
1162 protected:
1163 address _target; // address in CodeBlob
1164 int _section; // section providing base address, if any
1165
1166 friend class RelocIterator;
1167 internal_word_Relocation() { }
1168
1169 // bit-width of LSB field in packed offset, if section >= 0
1170 enum { section_width = 2 }; // must equal CodeBuffer::sect_bits
1171
1172 public:
1173 // data is packed as a scaled offset in "1_int" format: [o] or [Oo]
1174 // If the "o" value is 0 (i.e., _target is NULL), the offset is stored
1175 // in the code stream. See internal_word_Relocation::target().
1176 // If _section is not -1, it is appended to the low bits of the offset.
1177 void pack_data_to(CodeSection* dest);
1178 void unpack_data();
1179
1180 void fix_relocation_after_move(const CodeBuffer* src, CodeBuffer* dest);
1181 address target(); // if _target==NULL, fetch addr from code stream
1182 int section() { return _section; }
1183 address value() { return target(); }
1184 };
1185
1186 class section_word_Relocation : public internal_word_Relocation {
1187 relocInfo::relocType type() { return relocInfo::section_word_type; }
1188
1189 public:
1190 static RelocationHolder spec(address target, int section) {
1191 RelocationHolder rh = newHolder();
1192 new(rh) section_word_Relocation(target, section);
1193 return rh;
1194 }
1195
1196 section_word_Relocation(address target, int section) {
1197 assert(target != NULL, "must not be null");
1198 assert(section >= 0, "must be a valid section");
1199 _target = target;
1200 _section = section;
1201 }
1202
1203 //void pack_data_to -- inherited
1204 void unpack_data();
1205
1206 private:
1207 friend class RelocIterator;
1208 section_word_Relocation() { }
1209 };
1210
1211
1212 class poll_Relocation : public Relocation {
1213 bool is_data() { return true; }
1214 relocInfo::relocType type() { return relocInfo::poll_type; }
1215 void fix_relocation_after_move(const CodeBuffer* src, CodeBuffer* dest);
1216 };
1217
1218 class poll_return_Relocation : public Relocation {
1219 bool is_data() { return true; }
1220 relocInfo::relocType type() { return relocInfo::poll_return_type; }
1221 void fix_relocation_after_move(const CodeBuffer* src, CodeBuffer* dest);
1222 };
1223
1224
1225 class breakpoint_Relocation : public Relocation {
1226 relocInfo::relocType type() { return relocInfo::breakpoint_type; }
1227
1228 enum {
1229 // attributes which affect the interpretation of the data:
1230 removable_attr = 0x0010, // buffer [i...] allows for undoing the trap
1231 internal_attr = 0x0020, // the target is an internal addr (local stub)
1232 settable_attr = 0x0040, // the target is settable
1233
1234 // states which can change over time:
1235 enabled_state = 0x0100, // breakpoint must be active in running code
1236 active_state = 0x0200, // breakpoint instruction actually in code
1237
1238 kind_mask = 0x000F, // mask for extracting kind
1239 high_bit = 0x4000 // extra bit which is always set
1240 };
1241
1242 public:
1243 enum {
1244 // kinds:
1245 initialization = 1,
1246 safepoint = 2
1247 };
1248
1249 // If target is NULL, 32 bits are reserved for a later set_target().
1250 static RelocationHolder spec(int kind, address target = NULL, bool internal_target = false) {
1251 RelocationHolder rh = newHolder();
1252 new(rh) breakpoint_Relocation(kind, target, internal_target);
1253 return rh;
1254 }
1255
1256 private:
1257 // We require every bits value to NOT to fit into relocInfo::datalen_width,
1258 // because we are going to actually store state in the reloc, and so
1259 // cannot allow it to be compressed (and hence copied by the iterator).
1260
1261 short _bits; // bit-encoded kind, attrs, & state
1262 address _target;
1263
1264 breakpoint_Relocation(int kind, address target, bool internal_target);
1265
1266 friend class RelocIterator;
1267 breakpoint_Relocation() { }
1268
1269 short bits() const { return _bits; }
1270 short& live_bits() const { return data()[0]; }
1271 short* instrs() const { return data() + datalen() - instrlen(); }
1272 int instrlen() const { return removable() ? pd_breakpoint_size() : 0; }
1273
1274 void set_bits(short x) {
1275 assert(live_bits() == _bits, "must be the only mutator of reloc info");
1276 live_bits() = _bits = x;
1277 }
1278
1279 public:
1280 address target() const;
1281 void set_target(address x);
1282
1283 int kind() const { return bits() & kind_mask; }
1284 bool enabled() const { return (bits() & enabled_state) != 0; }
1285 bool active() const { return (bits() & active_state) != 0; }
1286 bool internal() const { return (bits() & internal_attr) != 0; }
1287 bool removable() const { return (bits() & removable_attr) != 0; }
1288 bool settable() const { return (bits() & settable_attr) != 0; }
1289
1290 void set_enabled(bool b); // to activate, you must also say set_active
1291 void set_active(bool b); // actually inserts bpt (must be enabled 1st)
1292
1293 // data is packed as 16 bits, followed by the target (1 or 2 words), followed
1294 // if necessary by empty storage for saving away original instruction bytes.
1295 void pack_data_to(CodeSection* dest);
1296 void unpack_data();
1297
1298 // during certain operations, breakpoints must be out of the way:
1299 void fix_relocation_after_move(const CodeBuffer* src, CodeBuffer* dest) {
1300 assert(!active(), "cannot perform relocation on enabled breakpoints");
1301 }
1302 };
1303
1304
1305 // We know all the xxx_Relocation classes, so now we can define these:
1306 #define EACH_CASE(name) \
1307 inline name##_Relocation* RelocIterator::name##_reloc() { \
1308 assert(type() == relocInfo::name##_type, "type must agree"); \
1309 /* The purpose of the placed "new" is to re-use the same */ \
1310 /* stack storage for each new iteration. */ \
1311 name##_Relocation* r = new(_rh) name##_Relocation(); \
1312 r->set_binding(this); \
1313 r->name##_Relocation::unpack_data(); \
1314 return r; \
1315 }
1316 APPLY_TO_RELOCATIONS(EACH_CASE);
1317 #undef EACH_CASE
1318
1319 inline RelocIterator::RelocIterator(nmethod* nm, address begin, address limit) {
1320 initialize(nm, begin, limit);
1321 }
1322
1323 // if you are going to patch code, you should use this subclass of
1324 // RelocIterator
1325 class PatchingRelocIterator : public RelocIterator {
1326 private:
1327 RelocIterator _init_state;
1328
1329 void prepass(); // deactivates all breakpoints
1330 void postpass(); // reactivates all enabled breakpoints
1331
1332 // do not copy these puppies; it would have unpredictable side effects
1333 // these are private and have no bodies defined because they should not be called
1334 PatchingRelocIterator(const RelocIterator&);
1335 void operator=(const RelocIterator&);
1336
1337 public:
1338 PatchingRelocIterator(nmethod* nm, address begin = NULL, address limit = NULL)
1339 : RelocIterator(nm, begin, limit) { prepass(); }
1340
1341 ~PatchingRelocIterator() { postpass(); }
1342 };
1343
1344 #endif // SHARE_VM_CODE_RELOCINFO_HPP