1 /*
   2  * Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  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).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "asm/codeBuffer.hpp"
  27 #include "asm/macroAssembler.hpp"
  28 #include "asm/macroAssembler.inline.hpp"
  29 #include "gc/shared/collectedHeap.hpp"
  30 #include "memory/universe.hpp"
  31 #include "oops/compressedOops.hpp"
  32 #include "runtime/atomic.hpp"
  33 #include "runtime/icache.hpp"
  34 #include "runtime/os.hpp"
  35 #include "runtime/thread.hpp"
  36 
  37 
  38 // Implementation of AbstractAssembler
  39 //
  40 // The AbstractAssembler is generating code into a CodeBuffer. To make code generation faster,
  41 // the assembler keeps a copy of the code buffers boundaries & modifies them when
  42 // emitting bytes rather than using the code buffers accessor functions all the time.
  43 // The code buffer is updated via set_code_end(...) after emitting a whole instruction.
  44 
  45 AbstractAssembler::AbstractAssembler(CodeBuffer* code) {
  46   if (code == NULL)  return;
  47   CodeSection* cs = code->insts();
  48   cs->clear_mark();   // new assembler kills old mark
  49   if (cs->start() == NULL)  {
  50     vm_exit_out_of_memory(0, OOM_MMAP_ERROR, "CodeCache: no room for %s", code->name());
  51   }
  52   _code_section = cs;
  53   _oop_recorder= code->oop_recorder();
  54   DEBUG_ONLY( _short_branch_delta = 0; )
  55 }
  56 
  57 void AbstractAssembler::set_code_section(CodeSection* cs) {
  58   assert(cs->outer() == code_section()->outer(), "sanity");
  59   assert(cs->is_allocated(), "need to pre-allocate this section");
  60   cs->clear_mark();  // new assembly into this section kills old mark
  61   _code_section = cs;
  62 }
  63 
  64 // Inform CodeBuffer that incoming code and relocation will be for stubs
  65 address AbstractAssembler::start_a_stub(int required_space) {
  66   CodeBuffer*  cb = code();
  67   CodeSection* cs = cb->stubs();
  68   assert(_code_section == cb->insts(), "not in insts?");
  69   if (cs->maybe_expand_to_ensure_remaining(required_space)
  70       && cb->blob() == NULL) {
  71     return NULL;
  72   }
  73   set_code_section(cs);
  74   return pc();
  75 }
  76 
  77 // Inform CodeBuffer that incoming code and relocation will be code
  78 // Should not be called if start_a_stub() returned NULL
  79 void AbstractAssembler::end_a_stub() {
  80   assert(_code_section == code()->stubs(), "not in stubs?");
  81   set_code_section(code()->insts());
  82 }
  83 
  84 // Inform CodeBuffer that incoming code and relocation will be for stubs
  85 address AbstractAssembler::start_a_const(int required_space, int required_align) {
  86   CodeBuffer*  cb = code();
  87   CodeSection* cs = cb->consts();
  88   assert(_code_section == cb->insts() || _code_section == cb->stubs(), "not in insts/stubs?");
  89   address end = cs->end();
  90   int pad = -(intptr_t)end & (required_align-1);
  91   if (cs->maybe_expand_to_ensure_remaining(pad + required_space)) {
  92     if (cb->blob() == NULL)  return NULL;
  93     end = cs->end();  // refresh pointer
  94   }
  95   if (pad > 0) {
  96     while (--pad >= 0) { *end++ = 0; }
  97     cs->set_end(end);
  98   }
  99   set_code_section(cs);
 100   return end;
 101 }
 102 
 103 // Inform CodeBuffer that incoming code and relocation will be code
 104 // in section cs (insts or stubs).
 105 void AbstractAssembler::end_a_const(CodeSection* cs) {
 106   assert(_code_section == code()->consts(), "not in consts?");
 107   set_code_section(cs);
 108 }
 109 
 110 void AbstractAssembler::flush() {
 111   ICache::invalidate_range(addr_at(0), offset());
 112 }
 113 
 114 void AbstractAssembler::bind(Label& L) {
 115   if (L.is_bound()) {
 116     // Assembler can bind a label more than once to the same place.
 117     guarantee(L.loc() == locator(), "attempt to redefine label");
 118     return;
 119   }
 120   L.bind_loc(locator());
 121   L.patch_instructions((MacroAssembler*)this);
 122 }
 123 
 124 void AbstractAssembler::generate_stack_overflow_check(int frame_size_in_bytes) {
 125   if (UseStackBanging) {
 126     // Each code entry causes one stack bang n pages down the stack where n
 127     // is configurable by StackShadowPages.  The setting depends on the maximum
 128     // depth of VM call stack or native before going back into java code,
 129     // since only java code can raise a stack overflow exception using the
 130     // stack banging mechanism.  The VM and native code does not detect stack
 131     // overflow.
 132     // The code in JavaCalls::call() checks that there is at least n pages
 133     // available, so all entry code needs to do is bang once for the end of
 134     // this shadow zone.
 135     // The entry code may need to bang additional pages if the framesize
 136     // is greater than a page.
 137 
 138     const int page_size = os::vm_page_size();
 139     int bang_end = (int)JavaThread::stack_shadow_zone_size();
 140 
 141     // This is how far the previous frame's stack banging extended.
 142     const int bang_end_safe = bang_end;
 143 
 144     if (frame_size_in_bytes > page_size) {
 145       bang_end += frame_size_in_bytes;
 146     }
 147 
 148     int bang_offset = bang_end_safe;
 149     while (bang_offset <= bang_end) {
 150       // Need at least one stack bang at end of shadow zone.
 151       bang_stack_with_offset(bang_offset);
 152       bang_offset += page_size;
 153     }
 154   } // end (UseStackBanging)
 155 }
 156 
 157 void Label::add_patch_at(CodeBuffer* cb, int branch_loc, const char* file, int line) {
 158   assert(_loc == -1, "Label is unbound");
 159   // Don't add patch locations during scratch emit.
 160   if (cb->insts()->scratch_emit()) { return; }
 161   if (_patch_index < PatchCacheSize) {
 162     _patches[_patch_index] = branch_loc;
 163 #ifdef ASSERT
 164     _lines[_patch_index] = line;
 165     _files[_patch_index] = file;
 166 #endif
 167   } else {
 168     if (_patch_overflow == NULL) {
 169       _patch_overflow = cb->create_patch_overflow();
 170     }
 171     _patch_overflow->push(branch_loc);
 172   }
 173   ++_patch_index;
 174 }
 175 
 176 void Label::patch_instructions(MacroAssembler* masm) {
 177   assert(is_bound(), "Label is bound");
 178   CodeBuffer* cb = masm->code();
 179   int target_sect = CodeBuffer::locator_sect(loc());
 180   address target = cb->locator_address(loc());
 181   while (_patch_index > 0) {
 182     --_patch_index;
 183     int branch_loc;
 184     int line = 0;
 185     const char* file = NULL;
 186     if (_patch_index >= PatchCacheSize) {
 187       branch_loc = _patch_overflow->pop();
 188     } else {
 189       branch_loc = _patches[_patch_index];
 190 #ifdef ASSERT
 191       line = _lines[_patch_index];
 192       file = _files[_patch_index];
 193 #endif
 194     }
 195     int branch_sect = CodeBuffer::locator_sect(branch_loc);
 196     address branch = cb->locator_address(branch_loc);
 197     if (branch_sect == CodeBuffer::SECT_CONSTS) {
 198       // The thing to patch is a constant word.
 199       *(address*)branch = target;
 200       continue;
 201     }
 202 
 203 #ifdef ASSERT
 204     // Cross-section branches only work if the
 205     // intermediate section boundaries are frozen.
 206     if (target_sect != branch_sect) {
 207       for (int n = MIN2(target_sect, branch_sect),
 208                nlimit = (target_sect + branch_sect) - n;
 209            n < nlimit; n++) {
 210         CodeSection* cs = cb->code_section(n);
 211         assert(cs->is_frozen(), "cross-section branch needs stable offsets");
 212       }
 213     }
 214 #endif //ASSERT
 215 
 216     // Push the target offset into the branch instruction.
 217     masm->pd_patch_instruction(branch, target, file, line);
 218   }
 219 }
 220 
 221 struct DelayedConstant {
 222   typedef void (*value_fn_t)();
 223   BasicType type;
 224   intptr_t value;
 225   value_fn_t value_fn;
 226   // This limit of 20 is generous for initial uses.
 227   // The limit needs to be large enough to store the field offsets
 228   // into classes which do not have statically fixed layouts.
 229   // (Initial use is for method handle object offsets.)
 230   // Look for uses of "delayed_value" in the source code
 231   // and make sure this number is generous enough to handle all of them.
 232   enum { DC_LIMIT = 20 };
 233   static DelayedConstant delayed_constants[DC_LIMIT];
 234   static DelayedConstant* add(BasicType type, value_fn_t value_fn);
 235   bool match(BasicType t, value_fn_t cfn) {
 236     return type == t && value_fn == cfn;
 237   }
 238   static void update_all();
 239 };
 240 
 241 DelayedConstant DelayedConstant::delayed_constants[DC_LIMIT];
 242 // Default C structure initialization rules have the following effect here:
 243 // = { { (BasicType)0, (intptr_t)NULL }, ... };
 244 
 245 DelayedConstant* DelayedConstant::add(BasicType type,
 246                                       DelayedConstant::value_fn_t cfn) {
 247   for (int i = 0; i < DC_LIMIT; i++) {
 248     DelayedConstant* dcon = &delayed_constants[i];
 249     if (dcon->match(type, cfn))
 250       return dcon;
 251     if (dcon->value_fn == NULL) {
 252         dcon->value_fn = cfn;
 253         dcon->type = type;
 254         return dcon;
 255     }
 256   }
 257   // If this assert is hit (in pre-integration testing!) then re-evaluate
 258   // the comment on the definition of DC_LIMIT.
 259   guarantee(false, "too many delayed constants");
 260   return NULL;
 261 }
 262 
 263 void DelayedConstant::update_all() {
 264   for (int i = 0; i < DC_LIMIT; i++) {
 265     DelayedConstant* dcon = &delayed_constants[i];
 266     if (dcon->value_fn != NULL && dcon->value == 0) {
 267       typedef int     (*int_fn_t)();
 268       typedef address (*address_fn_t)();
 269       switch (dcon->type) {
 270       case T_INT:     dcon->value = (intptr_t) ((int_fn_t)    dcon->value_fn)(); break;
 271       case T_ADDRESS: dcon->value = (intptr_t) ((address_fn_t)dcon->value_fn)(); break;
 272       default:        break;
 273       }
 274     }
 275   }
 276 }
 277 
 278 RegisterOrConstant AbstractAssembler::delayed_value(int(*value_fn)(), Register tmp, int offset) {
 279   intptr_t val = (intptr_t) (*value_fn)();
 280   if (val != 0)  return val + offset;
 281   return delayed_value_impl(delayed_value_addr(value_fn), tmp, offset);
 282 }
 283 RegisterOrConstant AbstractAssembler::delayed_value(address(*value_fn)(), Register tmp, int offset) {
 284   intptr_t val = (intptr_t) (*value_fn)();
 285   if (val != 0)  return val + offset;
 286   return delayed_value_impl(delayed_value_addr(value_fn), tmp, offset);
 287 }
 288 intptr_t* AbstractAssembler::delayed_value_addr(int(*value_fn)()) {
 289   DelayedConstant* dcon = DelayedConstant::add(T_INT, (DelayedConstant::value_fn_t) value_fn);
 290   return &dcon->value;
 291 }
 292 intptr_t* AbstractAssembler::delayed_value_addr(address(*value_fn)()) {
 293   DelayedConstant* dcon = DelayedConstant::add(T_ADDRESS, (DelayedConstant::value_fn_t) value_fn);
 294   return &dcon->value;
 295 }
 296 void AbstractAssembler::update_delayed_values() {
 297   DelayedConstant::update_all();
 298 }
 299 
 300 void AbstractAssembler::block_comment(const char* comment) {
 301   if (sect() == CodeBuffer::SECT_INSTS) {
 302     code_section()->outer()->block_comment(offset(), comment);
 303   }
 304 }
 305 
 306 const char* AbstractAssembler::code_string(const char* str) {
 307   if (sect() == CodeBuffer::SECT_INSTS || sect() == CodeBuffer::SECT_STUBS) {
 308     return code_section()->outer()->code_string(str);
 309   }
 310   return NULL;
 311 }
 312 
 313 bool MacroAssembler::uses_implicit_null_check(void* address) {
 314   // Exception handler checks the nmethod's implicit null checks table
 315   // only when this method returns false.
 316   uintptr_t addr = reinterpret_cast<uintptr_t>(address);
 317   uintptr_t page_size = (uintptr_t)os::vm_page_size();
 318 #ifdef _LP64
 319   if (UseCompressedOops && CompressedOops::base() != NULL) {
 320     // A SEGV can legitimately happen in C2 code at address
 321     // (heap_base + offset) if  Matcher::narrow_oop_use_complex_address
 322     // is configured to allow narrow oops field loads to be implicitly
 323     // null checked
 324     uintptr_t start = (uintptr_t)CompressedOops::base();
 325     uintptr_t end = start + page_size;
 326     if (addr >= start && addr < end) {
 327       return true;
 328     }
 329   }
 330 #endif
 331   return addr < page_size;
 332 }
 333 
 334 bool MacroAssembler::needs_explicit_null_check(intptr_t offset) {
 335   // The offset -1 is used (hardcoded) in a number of places in C1 and MacroAssembler
 336   // to indicate an unknown offset. For example, TemplateTable::pop_and_check_object(Register r)
 337   // calls MacroAssembler::null_check(Register reg, int offset = -1) which gets here
 338   // with -1. Another example is GraphBuilder::access_field(...) which uses -1 as placeholder
 339   // for offsets to be patched in later. The -1 there means the offset is not yet known
 340   // and may lie outside of the zero-trapping page, and thus we need to ensure we're forcing
 341   // an explicit null check for -1.
 342 
 343   // Check if offset is outside of [0, os::vm_page_size()]
 344   return offset < 0 || offset >= os::vm_page_size();
 345 }