1 /*
   2  * Copyright (c) 1999, 2016, 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 // no precompiled headers
  26 #include "asm/macroAssembler.hpp"
  27 #include "classfile/classLoader.hpp"
  28 #include "classfile/systemDictionary.hpp"
  29 #include "classfile/vmSymbols.hpp"
  30 #include "code/codeCache.hpp"
  31 #include "code/icBuffer.hpp"
  32 #include "code/vtableStubs.hpp"
  33 #include "interpreter/interpreter.hpp"
  34 #include "jvm_linux.h"
  35 #include "memory/allocation.inline.hpp"
  36 #include "mutex_linux.inline.hpp"
  37 #include "nativeInst_sparc.hpp"
  38 #include "os_share_linux.hpp"
  39 #include "prims/jniFastGetField.hpp"
  40 #include "prims/jvm.h"
  41 #include "prims/jvm_misc.hpp"
  42 #include "runtime/arguments.hpp"
  43 #include "runtime/extendedPC.hpp"
  44 #include "runtime/frame.inline.hpp"
  45 #include "runtime/interfaceSupport.hpp"
  46 #include "runtime/java.hpp"
  47 #include "runtime/javaCalls.hpp"
  48 #include "runtime/mutexLocker.hpp"
  49 #include "runtime/osThread.hpp"
  50 #include "runtime/sharedRuntime.hpp"
  51 #include "runtime/stubRoutines.hpp"
  52 #include "runtime/thread.inline.hpp"
  53 #include "runtime/timer.hpp"
  54 #include "utilities/events.hpp"
  55 #include "utilities/vmError.hpp"
  56 
  57 // Linux/Sparc has rather obscure naming of registers in sigcontext
  58 // different between 32 and 64 bits
  59 #ifdef _LP64
  60 #define SIG_PC(x) ((x)->sigc_regs.tpc)
  61 #define SIG_NPC(x) ((x)->sigc_regs.tnpc)
  62 #define SIG_REGS(x) ((x)->sigc_regs)
  63 #else
  64 #define SIG_PC(x) ((x)->si_regs.pc)
  65 #define SIG_NPC(x) ((x)->si_regs.npc)
  66 #define SIG_REGS(x) ((x)->si_regs)
  67 #endif
  68 
  69 // those are to reference registers in sigcontext
  70 enum {
  71   CON_G0 = 0,
  72   CON_G1,
  73   CON_G2,
  74   CON_G3,
  75   CON_G4,
  76   CON_G5,
  77   CON_G6,
  78   CON_G7,
  79   CON_O0,
  80   CON_O1,
  81   CON_O2,
  82   CON_O3,
  83   CON_O4,
  84   CON_O5,
  85   CON_O6,
  86   CON_O7,
  87 };
  88 
  89 // For Forte Analyzer AsyncGetCallTrace profiling support - thread is
  90 // currently interrupted by SIGPROF.
  91 // os::Solaris::fetch_frame_from_ucontext() tries to skip nested
  92 // signal frames. Currently we don't do that on Linux, so it's the
  93 // same as os::fetch_frame_from_context().
  94 ExtendedPC os::Linux::fetch_frame_from_ucontext(Thread* thread,
  95                                                 const ucontext_t* uc,
  96                                                 intptr_t** ret_sp,
  97                                                 intptr_t** ret_fp) {
  98   assert(thread != NULL, "just checking");
  99   assert(ret_sp != NULL, "just checking");
 100   assert(ret_fp != NULL, "just checking");
 101 
 102   return os::fetch_frame_from_context(uc, ret_sp, ret_fp);
 103 }
 104 
 105 ExtendedPC os::fetch_frame_from_context(const void* ucVoid,
 106                                         intptr_t** ret_sp,
 107                                         intptr_t** ret_fp) {
 108   const ucontext_t* uc = (const ucontext_t*) ucVoid;
 109   ExtendedPC  epc;
 110 
 111   if (uc != NULL) {
 112     epc = ExtendedPC(os::Linux::ucontext_get_pc(uc));
 113     if (ret_sp) {
 114       *ret_sp = os::Linux::ucontext_get_sp(uc);
 115     }
 116     if (ret_fp) {
 117       *ret_fp = (intptr_t*)NULL;
 118     }
 119   } else {
 120     // construct empty ExtendedPC for return value checking
 121     epc = ExtendedPC(NULL);
 122     if (ret_sp) {
 123       *ret_sp = (intptr_t*) NULL;
 124     }
 125     if (ret_fp) {
 126       *ret_fp = (intptr_t*) NULL;
 127     }
 128   }
 129 
 130   return epc;
 131 }
 132 
 133 frame os::fetch_frame_from_context(const void* ucVoid) {
 134   intptr_t* sp;
 135   ExtendedPC epc = fetch_frame_from_context(ucVoid, &sp, NULL);
 136   return frame(sp, frame::unpatchable, epc.pc());
 137 }
 138 
 139 frame os::get_sender_for_C_frame(frame* fr) {
 140   return frame(fr->sender_sp(), frame::unpatchable, fr->sender_pc());
 141 }
 142 
 143 frame os::current_frame() {
 144   intptr_t* sp = StubRoutines::Sparc::flush_callers_register_windows_func()();
 145   frame myframe(sp, frame::unpatchable,
 146                 CAST_FROM_FN_PTR(address, os::current_frame));
 147   if (os::is_first_C_frame(&myframe)) {
 148     // stack is not walkable
 149     return frame(NULL, frame::unpatchable, NULL);
 150   } else {
 151     return os::get_sender_for_C_frame(&myframe);
 152   }
 153 }
 154 
 155 address os::current_stack_pointer() {
 156   register void *sp __asm__ ("sp");
 157   return (address)sp;
 158 }
 159 
 160 static void current_stack_region(address* bottom, size_t* size) {
 161   if (os::Linux::is_initial_thread()) {
 162     // initial thread needs special handling because pthread_getattr_np()
 163     // may return bogus value.
 164     *bottom = os::Linux::initial_thread_stack_bottom();
 165     *size = os::Linux::initial_thread_stack_size();
 166   } else {
 167     pthread_attr_t attr;
 168 
 169     int rslt = pthread_getattr_np(pthread_self(), &attr);
 170 
 171     // JVM needs to know exact stack location, abort if it fails
 172     if (rslt != 0) {
 173       if (rslt == ENOMEM) {
 174         vm_exit_out_of_memory(0, OOM_MMAP_ERROR, "pthread_getattr_np");
 175       } else {
 176         fatal("pthread_getattr_np failed with errno = %d", rslt);
 177       }
 178     }
 179 
 180     if (pthread_attr_getstack(&attr, (void**)bottom, size) != 0) {
 181       fatal("Can not locate current stack attributes!");
 182     }
 183 
 184     pthread_attr_destroy(&attr);
 185   }
 186   assert(os::current_stack_pointer() >= *bottom &&
 187          os::current_stack_pointer() < *bottom + *size, "just checking");
 188 }
 189 
 190 address os::current_stack_base() {
 191   address bottom;
 192   size_t size;
 193   current_stack_region(&bottom, &size);
 194   return bottom + size;
 195 }
 196 
 197 size_t os::current_stack_size() {
 198   // stack size includes normal stack and HotSpot guard pages
 199   address bottom;
 200   size_t size;
 201   current_stack_region(&bottom, &size);
 202   return size;
 203 }
 204 
 205 char* os::non_memory_address_word() {
 206   // Must never look like an address returned by reserve_memory,
 207   // even in its subfields (as defined by the CPU immediate fields,
 208   // if the CPU splits constants across multiple instructions).
 209   // On SPARC, 0 != %hi(any real address), because there is no
 210   // allocation in the first 1Kb of the virtual address space.
 211   return (char*) 0;
 212 }
 213 
 214 void os::initialize_thread(Thread* thr) {}
 215 
 216 void os::print_context(outputStream *st, const void *context) {
 217   if (context == NULL) return;
 218 
 219   const ucontext_t* uc = (const ucontext_t*)context;
 220   sigcontext* sc = (sigcontext*)context;
 221   st->print_cr("Registers:");
 222 
 223   st->print_cr(" G1=" INTPTR_FORMAT " G2=" INTPTR_FORMAT
 224                " G3=" INTPTR_FORMAT " G4=" INTPTR_FORMAT,
 225                SIG_REGS(sc).u_regs[CON_G1],
 226                SIG_REGS(sc).u_regs[CON_G2],
 227                SIG_REGS(sc).u_regs[CON_G3],
 228                SIG_REGS(sc).u_regs[CON_G4]);
 229   st->print_cr(" G5=" INTPTR_FORMAT " G6=" INTPTR_FORMAT
 230                " G7=" INTPTR_FORMAT " Y=0x%x",
 231                SIG_REGS(sc).u_regs[CON_G5],
 232                SIG_REGS(sc).u_regs[CON_G6],
 233                SIG_REGS(sc).u_regs[CON_G7],
 234                SIG_REGS(sc).y);
 235   st->print_cr(" O0=" INTPTR_FORMAT " O1=" INTPTR_FORMAT
 236                " O2=" INTPTR_FORMAT " O3=" INTPTR_FORMAT,
 237                SIG_REGS(sc).u_regs[CON_O0],
 238                SIG_REGS(sc).u_regs[CON_O1],
 239                SIG_REGS(sc).u_regs[CON_O2],
 240                SIG_REGS(sc).u_regs[CON_O3]);
 241   st->print_cr(" O4=" INTPTR_FORMAT " O5=" INTPTR_FORMAT
 242                " O6=" INTPTR_FORMAT " O7=" INTPTR_FORMAT,
 243                SIG_REGS(sc).u_regs[CON_O4],
 244                SIG_REGS(sc).u_regs[CON_O5],
 245                SIG_REGS(sc).u_regs[CON_O6],
 246                SIG_REGS(sc).u_regs[CON_O7]);
 247 
 248 
 249   intptr_t *sp = (intptr_t *)os::Linux::ucontext_get_sp(uc);
 250   st->print_cr(" L0=" INTPTR_FORMAT " L1=" INTPTR_FORMAT
 251                " L2=" INTPTR_FORMAT " L3=" INTPTR_FORMAT,
 252                sp[L0->sp_offset_in_saved_window()],
 253                sp[L1->sp_offset_in_saved_window()],
 254                sp[L2->sp_offset_in_saved_window()],
 255                sp[L3->sp_offset_in_saved_window()]);
 256   st->print_cr(" L4=" INTPTR_FORMAT " L5=" INTPTR_FORMAT
 257                " L6=" INTPTR_FORMAT " L7=" INTPTR_FORMAT,
 258                sp[L4->sp_offset_in_saved_window()],
 259                sp[L5->sp_offset_in_saved_window()],
 260                sp[L6->sp_offset_in_saved_window()],
 261                sp[L7->sp_offset_in_saved_window()]);
 262   st->print_cr(" I0=" INTPTR_FORMAT " I1=" INTPTR_FORMAT
 263                " I2=" INTPTR_FORMAT " I3=" INTPTR_FORMAT,
 264                sp[I0->sp_offset_in_saved_window()],
 265                sp[I1->sp_offset_in_saved_window()],
 266                sp[I2->sp_offset_in_saved_window()],
 267                sp[I3->sp_offset_in_saved_window()]);
 268   st->print_cr(" I4=" INTPTR_FORMAT " I5=" INTPTR_FORMAT
 269                " I6=" INTPTR_FORMAT " I7=" INTPTR_FORMAT,
 270                sp[I4->sp_offset_in_saved_window()],
 271                sp[I5->sp_offset_in_saved_window()],
 272                sp[I6->sp_offset_in_saved_window()],
 273                sp[I7->sp_offset_in_saved_window()]);
 274 
 275   st->print_cr(" PC=" INTPTR_FORMAT " nPC=" INTPTR_FORMAT,
 276                SIG_PC(sc),
 277                SIG_NPC(sc));
 278   st->cr();
 279   st->cr();
 280 
 281   st->print_cr("Top of Stack: (sp=" INTPTR_FORMAT ")", p2i(sp));
 282   print_hex_dump(st, (address)sp, (address)(sp + 32), sizeof(intptr_t));
 283   st->cr();
 284 
 285   // Note: it may be unsafe to inspect memory near pc. For example, pc may
 286   // point to garbage if entry point in an nmethod is corrupted. Leave
 287   // this at the end, and hope for the best.
 288   address pc = os::Linux::ucontext_get_pc(uc);
 289   st->print_cr("Instructions: (pc=" INTPTR_FORMAT ")", p2i(pc));
 290   print_hex_dump(st, pc - 32, pc + 32, sizeof(char));
 291 }
 292 
 293 
 294 void os::print_register_info(outputStream *st, const void *context) {
 295   if (context == NULL) return;
 296 
 297   const ucontext_t *uc = (const ucontext_t*)context;
 298   const sigcontext* sc = (const sigcontext*)context;
 299   intptr_t *sp = (intptr_t *)os::Linux::ucontext_get_sp(uc);
 300 
 301   st->print_cr("Register to memory mapping:");
 302   st->cr();
 303 
 304   // this is only for the "general purpose" registers
 305   st->print("G1="); print_location(st, SIG_REGS(sc).u_regs[CON_G1]);
 306   st->print("G2="); print_location(st, SIG_REGS(sc).u_regs[CON_G2]);
 307   st->print("G3="); print_location(st, SIG_REGS(sc).u_regs[CON_G3]);
 308   st->print("G4="); print_location(st, SIG_REGS(sc).u_regs[CON_G4]);
 309   st->print("G5="); print_location(st, SIG_REGS(sc).u_regs[CON_G5]);
 310   st->print("G6="); print_location(st, SIG_REGS(sc).u_regs[CON_G6]);
 311   st->print("G7="); print_location(st, SIG_REGS(sc).u_regs[CON_G7]);
 312   st->cr();
 313 
 314   st->print("O0="); print_location(st, SIG_REGS(sc).u_regs[CON_O0]);
 315   st->print("O1="); print_location(st, SIG_REGS(sc).u_regs[CON_O1]);
 316   st->print("O2="); print_location(st, SIG_REGS(sc).u_regs[CON_O2]);
 317   st->print("O3="); print_location(st, SIG_REGS(sc).u_regs[CON_O3]);
 318   st->print("O4="); print_location(st, SIG_REGS(sc).u_regs[CON_O4]);
 319   st->print("O5="); print_location(st, SIG_REGS(sc).u_regs[CON_O5]);
 320   st->print("O6="); print_location(st, SIG_REGS(sc).u_regs[CON_O6]);
 321   st->print("O7="); print_location(st, SIG_REGS(sc).u_regs[CON_O7]);
 322   st->cr();
 323 
 324   st->print("L0="); print_location(st, sp[L0->sp_offset_in_saved_window()]);
 325   st->print("L1="); print_location(st, sp[L1->sp_offset_in_saved_window()]);
 326   st->print("L2="); print_location(st, sp[L2->sp_offset_in_saved_window()]);
 327   st->print("L3="); print_location(st, sp[L3->sp_offset_in_saved_window()]);
 328   st->print("L4="); print_location(st, sp[L4->sp_offset_in_saved_window()]);
 329   st->print("L5="); print_location(st, sp[L5->sp_offset_in_saved_window()]);
 330   st->print("L6="); print_location(st, sp[L6->sp_offset_in_saved_window()]);
 331   st->print("L7="); print_location(st, sp[L7->sp_offset_in_saved_window()]);
 332   st->cr();
 333 
 334   st->print("I0="); print_location(st, sp[I0->sp_offset_in_saved_window()]);
 335   st->print("I1="); print_location(st, sp[I1->sp_offset_in_saved_window()]);
 336   st->print("I2="); print_location(st, sp[I2->sp_offset_in_saved_window()]);
 337   st->print("I3="); print_location(st, sp[I3->sp_offset_in_saved_window()]);
 338   st->print("I4="); print_location(st, sp[I4->sp_offset_in_saved_window()]);
 339   st->print("I5="); print_location(st, sp[I5->sp_offset_in_saved_window()]);
 340   st->print("I6="); print_location(st, sp[I6->sp_offset_in_saved_window()]);
 341   st->print("I7="); print_location(st, sp[I7->sp_offset_in_saved_window()]);
 342   st->cr();
 343 }
 344 
 345 
 346 address os::Linux::ucontext_get_pc(const ucontext_t* uc) {
 347   return (address) SIG_PC((sigcontext*)uc);
 348 }
 349 
 350 void os::Linux::ucontext_set_pc(ucontext_t* uc, address pc) {
 351   sigcontext* ctx = (sigcontext*) uc;
 352   SIG_PC(ctx)  = (intptr_t)pc;
 353   SIG_NPC(ctx) = (intptr_t)(pc+4);
 354 }
 355 
 356 intptr_t* os::Linux::ucontext_get_sp(const ucontext_t *uc) {
 357   return (intptr_t*)
 358     ((intptr_t)SIG_REGS((sigcontext*)uc).u_regs[CON_O6] + STACK_BIAS);
 359 }
 360 
 361 // not used on Sparc
 362 intptr_t* os::Linux::ucontext_get_fp(const ucontext_t *uc) {
 363   ShouldNotReachHere();
 364   return NULL;
 365 }
 366 
 367 // Utility functions
 368 
 369 inline static bool checkPrefetch(sigcontext* uc, address pc) {
 370   if (StubRoutines::is_safefetch_fault(pc)) {
 371     os::Linux::ucontext_set_pc((ucontext_t*)uc, StubRoutines::continuation_for_safefetch_fault(pc));
 372     return true;
 373   }
 374   return false;
 375 }
 376 
 377 inline static bool checkOverflow(sigcontext* uc,
 378                                  address pc,
 379                                  address addr,
 380                                  JavaThread* thread,
 381                                  address* stub) {
 382   // check if fault address is within thread stack
 383   if (thread->on_local_stack(addr)) {
 384     // stack overflow
 385     if (thread->in_stack_yellow_reserved_zone(addr)) {
 386       thread->disable_stack_yellow_reserved_zone();
 387       if (thread->thread_state() == _thread_in_Java) {
 388         // Throw a stack overflow exception.  Guard pages will be reenabled
 389         // while unwinding the stack.
 390         *stub =
 391           SharedRuntime::continuation_for_implicit_exception(thread,
 392                                                              pc,
 393                                                              SharedRuntime::STACK_OVERFLOW);
 394       } else {
 395         // Thread was in the vm or native code.  Return and try to finish.
 396         return true;
 397       }
 398     } else if (thread->in_stack_red_zone(addr)) {
 399       // Fatal red zone violation.  Disable the guard pages and fall through
 400       // to handle_unexpected_exception way down below.
 401       thread->disable_stack_red_zone();
 402       tty->print_raw_cr("An irrecoverable stack overflow has occurred.");
 403 
 404       // This is a likely cause, but hard to verify. Let's just print
 405       // it as a hint.
 406       tty->print_raw_cr("Please check if any of your loaded .so files has "
 407                         "enabled executable stack (see man page execstack(8))");
 408     } else {
 409       // Accessing stack address below sp may cause SEGV if current
 410       // thread has MAP_GROWSDOWN stack. This should only happen when
 411       // current thread was created by user code with MAP_GROWSDOWN flag
 412       // and then attached to VM. See notes in os_linux.cpp.
 413       if (thread->osthread()->expanding_stack() == 0) {
 414         thread->osthread()->set_expanding_stack();
 415         if (os::Linux::manually_expand_stack(thread, addr)) {
 416           thread->osthread()->clear_expanding_stack();
 417           return true;
 418         }
 419         thread->osthread()->clear_expanding_stack();
 420       } else {
 421         fatal("recursive segv. expanding stack.");
 422       }
 423     }
 424   }
 425   return false;
 426 }
 427 
 428 inline static bool checkPollingPage(address pc, address fault, address* stub) {
 429   if (fault == os::get_polling_page()) {
 430     *stub = SharedRuntime::get_poll_stub(pc);
 431     return true;
 432   }
 433   return false;
 434 }
 435 
 436 inline static bool checkByteBuffer(address pc, address npc, address* stub) {
 437   // BugId 4454115: A read from a MappedByteBuffer can fault
 438   // here if the underlying file has been truncated.
 439   // Do not crash the VM in such a case.
 440   CodeBlob* cb = CodeCache::find_blob_unsafe(pc);
 441   CompiledMethod* nm = cb->as_compiled_method_or_null();
 442   if (nm != NULL && nm->has_unsafe_access()) {
 443     *stub = SharedRuntime::handle_unsafe_access(thread, npc);
 444     return true;
 445   }
 446   return false;
 447 }
 448 
 449 inline static bool checkVerifyOops(address pc, address fault, address* stub) {
 450   if (pc >= MacroAssembler::_verify_oop_implicit_branch[0]
 451       && pc <  MacroAssembler::_verify_oop_implicit_branch[1] ) {
 452     *stub     =  MacroAssembler::_verify_oop_implicit_branch[2];
 453     warning("fixed up memory fault in +VerifyOops at address "
 454             INTPTR_FORMAT, p2i(fault));
 455     return true;
 456   }
 457   return false;
 458 }
 459 
 460 inline static bool checkFPFault(address pc, int code,
 461                                 JavaThread* thread, address* stub) {
 462   if (code == FPE_INTDIV || code == FPE_FLTDIV) {
 463     *stub =
 464       SharedRuntime::
 465       continuation_for_implicit_exception(thread,
 466                                           pc,
 467                                           SharedRuntime::IMPLICIT_DIVIDE_BY_ZERO);
 468     return true;
 469   }
 470   return false;
 471 }
 472 
 473 inline static bool checkNullPointer(address pc, intptr_t fault,
 474                                     JavaThread* thread, address* stub) {
 475   if (!MacroAssembler::needs_explicit_null_check(fault)) {
 476     // Determination of interpreter/vtable stub/compiled code null
 477     // exception
 478     *stub =
 479       SharedRuntime::
 480       continuation_for_implicit_exception(thread, pc,
 481                                           SharedRuntime::IMPLICIT_NULL);
 482     return true;
 483   }
 484   return false;
 485 }
 486 
 487 inline static bool checkFastJNIAccess(address pc, address* stub) {
 488   address addr = JNI_FastGetField::find_slowcase_pc(pc);
 489   if (addr != (address)-1) {
 490     *stub = addr;
 491     return true;
 492   }
 493   return false;
 494 }
 495 
 496 inline static bool checkSerializePage(JavaThread* thread, address addr) {
 497   return os::is_memory_serialize_page(thread, addr);
 498 }
 499 
 500 inline static bool checkZombie(sigcontext* uc, address* pc, address* stub) {
 501   if (nativeInstruction_at(*pc)->is_zombie()) {
 502     // zombie method (ld [%g0],%o7 instruction)
 503     *stub = SharedRuntime::get_handle_wrong_method_stub();
 504 
 505     // At the stub it needs to look like a call from the caller of this
 506     // method (not a call from the segv site).
 507     *pc = (address)SIG_REGS(uc).u_regs[CON_O7];
 508     return true;
 509   }
 510   return false;
 511 }
 512 
 513 inline static bool checkICMiss(sigcontext* uc, address* pc, address* stub) {
 514 #ifdef COMPILER2
 515   if (nativeInstruction_at(*pc)->is_ic_miss_trap()) {
 516 #ifdef ASSERT
 517 #ifdef TIERED
 518     CodeBlob* cb = CodeCache::find_blob_unsafe(*pc);
 519     assert(cb->is_compiled_by_c2(), "Wrong compiler");
 520 #endif // TIERED
 521 #endif // ASSERT
 522     // Inline cache missed and user trap "Tne G0+ST_RESERVED_FOR_USER_0+2" taken.
 523     *stub = SharedRuntime::get_ic_miss_stub();
 524     // At the stub it needs to look like a call from the caller of this
 525     // method (not a call from the segv site).
 526     *pc = (address)SIG_REGS(uc).u_regs[CON_O7];
 527     return true;
 528   }
 529 #endif  // COMPILER2
 530   return false;
 531 }
 532 
 533 extern "C" JNIEXPORT int
 534 JVM_handle_linux_signal(int sig,
 535                         siginfo_t* info,
 536                         void* ucVoid,
 537                         int abort_if_unrecognized) {
 538   // in fact this isn't ucontext_t* at all, but struct sigcontext*
 539   // but Linux porting layer uses ucontext_t, so to minimize code change
 540   // we cast as needed
 541   ucontext_t* ucFake = (ucontext_t*) ucVoid;
 542   sigcontext* uc = (sigcontext*)ucVoid;
 543 
 544   Thread* t = Thread::current_or_null_safe();
 545 
 546   // Must do this before SignalHandlerMark, if crash protection installed we will longjmp away
 547   // (no destructors can be run)
 548   os::WatcherThreadCrashProtection::check_crash_protection(sig, t);
 549 
 550   SignalHandlerMark shm(t);
 551 
 552   // Note: it's not uncommon that JNI code uses signal/sigset to install
 553   // then restore certain signal handler (e.g. to temporarily block SIGPIPE,
 554   // or have a SIGILL handler when detecting CPU type). When that happens,
 555   // JVM_handle_linux_signal() might be invoked with junk info/ucVoid. To
 556   // avoid unnecessary crash when libjsig is not preloaded, try handle signals
 557   // that do not require siginfo/ucontext first.
 558 
 559   if (sig == SIGPIPE || sig == SIGXFSZ) {
 560     // allow chained handler to go first
 561     if (os::Linux::chained_handler(sig, info, ucVoid)) {
 562       return true;
 563     } else {
 564       // Ignoring SIGPIPE/SIGXFSZ - see bugs 4229104 or 6499219
 565       return true;
 566     }
 567   }
 568 
 569   JavaThread* thread = NULL;
 570   VMThread* vmthread = NULL;
 571   if (os::Linux::signal_handlers_are_installed) {
 572     if (t != NULL ){
 573       if(t->is_Java_thread()) {
 574         thread = (JavaThread*)t;
 575       }
 576       else if(t->is_VM_thread()){
 577         vmthread = (VMThread *)t;
 578       }
 579     }
 580   }
 581 
 582   // decide if this trap can be handled by a stub
 583   address stub = NULL;
 584   address pc = NULL;
 585   address npc = NULL;
 586 
 587   //%note os_trap_1
 588   if (info != NULL && uc != NULL && thread != NULL) {
 589     pc = address(SIG_PC(uc));
 590     npc = address(SIG_NPC(uc));
 591 
 592     // Check to see if we caught the safepoint code in the
 593     // process of write protecting the memory serialization page.
 594     // It write enables the page immediately after protecting it
 595     // so we can just return to retry the write.
 596     if ((sig == SIGSEGV) && checkSerializePage(thread, (address)info->si_addr)) {
 597       // Block current thread until the memory serialize page permission restored.
 598       os::block_on_serialize_page_trap();
 599       return 1;
 600     }
 601 
 602     if (checkPrefetch(uc, pc)) {
 603       return 1;
 604     }
 605 
 606     // Handle ALL stack overflow variations here
 607     if (sig == SIGSEGV) {
 608       if (checkOverflow(uc, pc, (address)info->si_addr, thread, &stub)) {
 609         return 1;
 610       }
 611     }
 612 
 613     if (sig == SIGBUS &&
 614         thread->thread_state() == _thread_in_vm &&
 615         thread->doing_unsafe_access()) {
 616       stub = SharedRuntime::handle_unsafe_access(thread, npc);
 617     }
 618 
 619     if (thread->thread_state() == _thread_in_Java) {
 620       do {
 621         // Java thread running in Java code => find exception handler if any
 622         // a fault inside compiled code, the interpreter, or a stub
 623 
 624         if ((sig == SIGSEGV) && checkPollingPage(pc, (address)info->si_addr, &stub)) {
 625           break;
 626         }
 627 
 628         if ((sig == SIGBUS) && checkByteBuffer(pc, npc, &stub)) {
 629           break;
 630         }
 631 
 632         if ((sig == SIGSEGV || sig == SIGBUS) &&
 633             checkVerifyOops(pc, (address)info->si_addr, &stub)) {
 634           break;
 635         }
 636 
 637         if ((sig == SIGSEGV) && checkZombie(uc, &pc, &stub)) {
 638           break;
 639         }
 640 
 641         if ((sig == SIGILL) && checkICMiss(uc, &pc, &stub)) {
 642           break;
 643         }
 644 
 645         if ((sig == SIGFPE) && checkFPFault(pc, info->si_code, thread, &stub)) {
 646           break;
 647         }
 648 
 649         if ((sig == SIGSEGV) &&
 650             checkNullPointer(pc, (intptr_t)info->si_addr, thread, &stub)) {
 651           break;
 652         }
 653       } while (0);
 654 
 655       // jni_fast_Get<Primitive>Field can trap at certain pc's if a GC kicks in
 656       // and the heap gets shrunk before the field access.
 657       if ((sig == SIGSEGV) || (sig == SIGBUS)) {
 658         checkFastJNIAccess(pc, &stub);
 659       }
 660     }
 661 
 662     if (stub != NULL) {
 663       // save all thread context in case we need to restore it
 664       thread->set_saved_exception_pc(pc);
 665       thread->set_saved_exception_npc(npc);
 666       os::Linux::ucontext_set_pc((ucontext_t*)uc, stub);
 667       return true;
 668     }
 669   }
 670 
 671   // signal-chaining
 672   if (os::Linux::chained_handler(sig, info, ucVoid)) {
 673     return true;
 674   }
 675 
 676   if (!abort_if_unrecognized) {
 677     // caller wants another chance, so give it to him
 678     return false;
 679   }
 680 
 681   if (pc == NULL && uc != NULL) {
 682     pc = os::Linux::ucontext_get_pc((const ucontext_t*)uc);
 683   }
 684 
 685   // unmask current signal
 686   sigset_t newset;
 687   sigemptyset(&newset);
 688   sigaddset(&newset, sig);
 689   sigprocmask(SIG_UNBLOCK, &newset, NULL);
 690 
 691   VMError::report_and_die(t, sig, pc, info, ucVoid);
 692 
 693   ShouldNotReachHere();
 694   return false;
 695 }
 696 
 697 void os::Linux::init_thread_fpu_state(void) {
 698   // Nothing to do
 699 }
 700 
 701 int os::Linux::get_fpu_control_word() {
 702   return 0;
 703 }
 704 
 705 void os::Linux::set_fpu_control_word(int fpu) {
 706   // nothing
 707 }
 708 
 709 bool os::is_allocatable(size_t bytes) {
 710 #ifdef _LP64
 711   return true;
 712 #else
 713   if (bytes < 2 * G) {
 714     return true;
 715   }
 716 
 717   char* addr = reserve_memory(bytes, NULL);
 718 
 719   if (addr != NULL) {
 720     release_memory(addr, bytes);
 721   }
 722 
 723   return addr != NULL;
 724 #endif // _LP64
 725 }
 726 
 727 ///////////////////////////////////////////////////////////////////////////////
 728 // thread stack
 729 
 730 size_t os::Linux::min_stack_allowed  = 128 * K;
 731 
 732 // return default stack size for thr_type
 733 size_t os::Linux::default_stack_size(os::ThreadType thr_type) {
 734   // default stack size (compiler thread needs larger stack)
 735   size_t s = (thr_type == os::compiler_thread ? 4 * M : 1 * M);
 736   return s;
 737 }
 738 
 739 size_t os::Linux::default_guard_size(os::ThreadType thr_type) {
 740   // Creating guard page is very expensive. Java thread has HotSpot
 741   // guard page, only enable glibc guard page for non-Java threads.
 742   return (thr_type == java_thread ? 0 : page_size());
 743 }
 744 
 745 #ifndef PRODUCT
 746 void os::verify_stack_alignment() {
 747 }
 748 #endif
 749 
 750 int os::extra_bang_size_in_bytes() {
 751   // SPARC does not require the additional stack bang.
 752   return 0;
 753 }