1 /*
   2  * Copyright (c) 1999, 2018, 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/icBuffer.hpp"
  31 #include "code/vtableStubs.hpp"
  32 #include "interpreter/interpreter.hpp"
  33 #include "jvm_linux.h"
  34 #include "memory/allocation.inline.hpp"
  35 #include "mutex_linux.inline.hpp"
  36 #include "nativeInst_sparc.hpp"
  37 #include "os_share_linux.hpp"
  38 #include "prims/jniFastGetField.hpp"
  39 #include "prims/jvm.h"
  40 #include "prims/jvm_misc.hpp"
  41 #include "runtime/arguments.hpp"
  42 #include "runtime/extendedPC.hpp"
  43 #include "runtime/frame.inline.hpp"
  44 #include "runtime/interfaceSupport.hpp"
  45 #include "runtime/java.hpp"
  46 #include "runtime/javaCalls.hpp"
  47 #include "runtime/mutexLocker.hpp"
  48 #include "runtime/osThread.hpp"
  49 #include "runtime/sharedRuntime.hpp"
  50 #include "runtime/stubRoutines.hpp"
  51 #include "runtime/thread.inline.hpp"
  52 #include "runtime/timer.hpp"
  53 #include "utilities/events.hpp"
  54 #include "utilities/vmError.hpp"
  55 
  56 // Linux/Sparc has rather obscure naming of registers in sigcontext
  57 // different between 32 and 64 bits
  58 #ifdef _LP64
  59 #define SIG_PC(x) ((x)->sigc_regs.tpc)
  60 #define SIG_NPC(x) ((x)->sigc_regs.tnpc)
  61 #define SIG_REGS(x) ((x)->sigc_regs)
  62 #else
  63 #define SIG_PC(x) ((x)->si_regs.pc)
  64 #define SIG_NPC(x) ((x)->si_regs.npc)
  65 #define SIG_REGS(x) ((x)->si_regs)
  66 #endif
  67 
  68 // those are to reference registers in sigcontext
  69 enum {
  70   CON_G0 = 0,
  71   CON_G1,
  72   CON_G2,
  73   CON_G3,
  74   CON_G4,
  75   CON_G5,
  76   CON_G6,
  77   CON_G7,
  78   CON_O0,
  79   CON_O1,
  80   CON_O2,
  81   CON_O3,
  82   CON_O4,
  83   CON_O5,
  84   CON_O6,
  85   CON_O7,
  86 };
  87 
  88 static inline void set_cont_address(sigcontext* ctx, address addr) {
  89   SIG_PC(ctx)  = (intptr_t)addr;
  90   SIG_NPC(ctx) = (intptr_t)(addr+4);
  91 }
  92 
  93 // For Forte Analyzer AsyncGetCallTrace profiling support - thread is
  94 // currently interrupted by SIGPROF.
  95 // os::Solaris::fetch_frame_from_ucontext() tries to skip nested
  96 // signal frames. Currently we don't do that on Linux, so it's the
  97 // same as os::fetch_frame_from_context().
  98 ExtendedPC os::Linux::fetch_frame_from_ucontext(Thread* thread,
  99                                                 ucontext_t* uc,
 100                                                 intptr_t** ret_sp,
 101                                                 intptr_t** ret_fp) {
 102   assert(thread != NULL, "just checking");
 103   assert(ret_sp != NULL, "just checking");
 104   assert(ret_fp != NULL, "just checking");
 105 
 106   return os::fetch_frame_from_context(uc, ret_sp, ret_fp);
 107 }
 108 
 109 ExtendedPC os::fetch_frame_from_context(void* ucVoid,
 110                                         intptr_t** ret_sp,
 111                                         intptr_t** ret_fp) {
 112   ucontext_t* uc = (ucontext_t*) ucVoid;
 113   ExtendedPC  epc;
 114 
 115   if (uc != NULL) {
 116     epc = ExtendedPC(os::Linux::ucontext_get_pc(uc));
 117     if (ret_sp) {
 118       *ret_sp = os::Linux::ucontext_get_sp(uc);
 119     }
 120     if (ret_fp) {
 121       *ret_fp = (intptr_t*)NULL;
 122     }
 123   } else {
 124     // construct empty ExtendedPC for return value checking
 125     epc = ExtendedPC(NULL);
 126     if (ret_sp) {
 127       *ret_sp = (intptr_t*) NULL;
 128     }
 129     if (ret_fp) {
 130       *ret_fp = (intptr_t*) NULL;
 131     }
 132   }
 133 
 134   return epc;
 135 }
 136 
 137 frame os::fetch_frame_from_context(void* ucVoid) {
 138   intptr_t* sp;
 139   ExtendedPC epc = fetch_frame_from_context(ucVoid, &sp, NULL);
 140   return frame(sp, frame::unpatchable, epc.pc());
 141 }
 142 
 143 frame os::get_sender_for_C_frame(frame* fr) {
 144   return frame(fr->sender_sp(), frame::unpatchable, fr->sender_pc());
 145 }
 146 
 147 frame os::current_frame() {
 148   intptr_t* sp = StubRoutines::Sparc::flush_callers_register_windows_func()();
 149   frame myframe(sp, frame::unpatchable,
 150                 CAST_FROM_FN_PTR(address, os::current_frame));
 151   if (os::is_first_C_frame(&myframe)) {
 152     // stack is not walkable
 153     return frame(NULL, frame::unpatchable, NULL);
 154   } else {
 155     return os::get_sender_for_C_frame(&myframe);
 156   }
 157 }
 158 
 159 address os::current_stack_pointer() {
 160   register void *sp __asm__ ("sp");
 161   return (address)sp;
 162 }
 163 
 164 static void current_stack_region(address* bottom, size_t* size) {
 165   if (os::is_primordial_thread()) {
 166     // primordial thread needs special handling because pthread_getattr_np()
 167     // may return bogus value.
 168     *bottom = os::Linux::initial_thread_stack_bottom();
 169     *size = os::Linux::initial_thread_stack_size();
 170   } else {
 171     pthread_attr_t attr;
 172 
 173     int rslt = pthread_getattr_np(pthread_self(), &attr);
 174 
 175     // JVM needs to know exact stack location, abort if it fails
 176     if (rslt != 0) {
 177       if (rslt == ENOMEM) {
 178         vm_exit_out_of_memory(0, OOM_MMAP_ERROR, "pthread_getattr_np");
 179       } else {
 180         fatal(err_msg("pthread_getattr_np failed with errno = %d", rslt));
 181       }
 182     }
 183 
 184     if (pthread_attr_getstack(&attr, (void**)bottom, size) != 0) {
 185       fatal("Can not locate current stack attributes!");
 186     }
 187 
 188     pthread_attr_destroy(&attr);
 189   }
 190   assert(os::current_stack_pointer() >= *bottom &&
 191          os::current_stack_pointer() < *bottom + *size, "just checking");
 192 }
 193 
 194 address os::current_stack_base() {
 195   address bottom;
 196   size_t size;
 197   current_stack_region(&bottom, &size);
 198   return bottom + size;
 199 }
 200 
 201 size_t os::current_stack_size() {
 202   // stack size includes normal stack and HotSpot guard pages
 203   address bottom;
 204   size_t size;
 205   current_stack_region(&bottom, &size);
 206   return size;
 207 }
 208 
 209 char* os::non_memory_address_word() {
 210   // Must never look like an address returned by reserve_memory,
 211   // even in its subfields (as defined by the CPU immediate fields,
 212   // if the CPU splits constants across multiple instructions).
 213   // On SPARC, 0 != %hi(any real address), because there is no
 214   // allocation in the first 1Kb of the virtual address space.
 215   return (char*) 0;
 216 }
 217 
 218 void os::initialize_thread(Thread* thr) {}
 219 
 220 void os::print_context(outputStream *st, void *context) {
 221   if (context == NULL) return;
 222 
 223   ucontext_t* uc = (ucontext_t*)context;
 224   sigcontext* sc = (sigcontext*)context;
 225   st->print_cr("Registers:");
 226 
 227   st->print_cr(" G1=" INTPTR_FORMAT " G2=" INTPTR_FORMAT
 228                " G3=" INTPTR_FORMAT " G4=" INTPTR_FORMAT,
 229                SIG_REGS(sc).u_regs[CON_G1],
 230                SIG_REGS(sc).u_regs[CON_G2],
 231                SIG_REGS(sc).u_regs[CON_G3],
 232                SIG_REGS(sc).u_regs[CON_G4]);
 233   st->print_cr(" G5=" INTPTR_FORMAT " G6=" INTPTR_FORMAT
 234                " G7=" INTPTR_FORMAT " Y=" INTPTR_FORMAT,
 235                SIG_REGS(sc).u_regs[CON_G5],
 236                SIG_REGS(sc).u_regs[CON_G6],
 237                SIG_REGS(sc).u_regs[CON_G7],
 238                SIG_REGS(sc).y);
 239   st->print_cr(" O0=" INTPTR_FORMAT " O1=" INTPTR_FORMAT
 240                " O2=" INTPTR_FORMAT " O3=" INTPTR_FORMAT,
 241                SIG_REGS(sc).u_regs[CON_O0],
 242                SIG_REGS(sc).u_regs[CON_O1],
 243                SIG_REGS(sc).u_regs[CON_O2],
 244                SIG_REGS(sc).u_regs[CON_O3]);
 245   st->print_cr(" O4=" INTPTR_FORMAT " O5=" INTPTR_FORMAT
 246                " O6=" INTPTR_FORMAT " O7=" INTPTR_FORMAT,
 247                SIG_REGS(sc).u_regs[CON_O4],
 248                SIG_REGS(sc).u_regs[CON_O5],
 249                SIG_REGS(sc).u_regs[CON_O6],
 250                SIG_REGS(sc).u_regs[CON_O7]);
 251 
 252 
 253   intptr_t *sp = (intptr_t *)os::Linux::ucontext_get_sp(uc);
 254   st->print_cr(" L0=" INTPTR_FORMAT " L1=" INTPTR_FORMAT
 255                " L2=" INTPTR_FORMAT " L3=" INTPTR_FORMAT,
 256                sp[L0->sp_offset_in_saved_window()],
 257                sp[L1->sp_offset_in_saved_window()],
 258                sp[L2->sp_offset_in_saved_window()],
 259                sp[L3->sp_offset_in_saved_window()]);
 260   st->print_cr(" L4=" INTPTR_FORMAT " L5=" INTPTR_FORMAT
 261                " L6=" INTPTR_FORMAT " L7=" INTPTR_FORMAT,
 262                sp[L4->sp_offset_in_saved_window()],
 263                sp[L5->sp_offset_in_saved_window()],
 264                sp[L6->sp_offset_in_saved_window()],
 265                sp[L7->sp_offset_in_saved_window()]);
 266   st->print_cr(" I0=" INTPTR_FORMAT " I1=" INTPTR_FORMAT
 267                " I2=" INTPTR_FORMAT " I3=" INTPTR_FORMAT,
 268                sp[I0->sp_offset_in_saved_window()],
 269                sp[I1->sp_offset_in_saved_window()],
 270                sp[I2->sp_offset_in_saved_window()],
 271                sp[I3->sp_offset_in_saved_window()]);
 272   st->print_cr(" I4=" INTPTR_FORMAT " I5=" INTPTR_FORMAT
 273                " I6=" INTPTR_FORMAT " I7=" INTPTR_FORMAT,
 274                sp[I4->sp_offset_in_saved_window()],
 275                sp[I5->sp_offset_in_saved_window()],
 276                sp[I6->sp_offset_in_saved_window()],
 277                sp[I7->sp_offset_in_saved_window()]);
 278 
 279   st->print_cr(" PC=" INTPTR_FORMAT " nPC=" INTPTR_FORMAT,
 280                SIG_PC(sc),
 281                SIG_NPC(sc));
 282   st->cr();
 283   st->cr();
 284 
 285   st->print_cr("Top of Stack: (sp=" PTR_FORMAT ")", sp);
 286   print_hex_dump(st, (address)sp, (address)(sp + 32), sizeof(intptr_t));
 287   st->cr();
 288 
 289   // Note: it may be unsafe to inspect memory near pc. For example, pc may
 290   // point to garbage if entry point in an nmethod is corrupted. Leave
 291   // this at the end, and hope for the best.
 292   address pc = os::Linux::ucontext_get_pc(uc);
 293   st->print_cr("Instructions: (pc=" PTR_FORMAT ")", pc);
 294   print_hex_dump(st, pc - 32, pc + 32, sizeof(char));
 295 }
 296 
 297 
 298 void os::print_register_info(outputStream *st, void *context) {
 299   if (context == NULL) return;
 300 
 301   ucontext_t *uc = (ucontext_t*)context;
 302   sigcontext* sc = (sigcontext*)context;
 303   intptr_t *sp = (intptr_t *)os::Linux::ucontext_get_sp(uc);
 304 
 305   st->print_cr("Register to memory mapping:");
 306   st->cr();
 307 
 308   // this is only for the "general purpose" registers
 309   st->print("G1="); print_location(st, SIG_REGS(sc).u_regs[CON_G1]);
 310   st->print("G2="); print_location(st, SIG_REGS(sc).u_regs[CON_G2]);
 311   st->print("G3="); print_location(st, SIG_REGS(sc).u_regs[CON_G3]);
 312   st->print("G4="); print_location(st, SIG_REGS(sc).u_regs[CON_G4]);
 313   st->print("G5="); print_location(st, SIG_REGS(sc).u_regs[CON_G5]);
 314   st->print("G6="); print_location(st, SIG_REGS(sc).u_regs[CON_G6]);
 315   st->print("G7="); print_location(st, SIG_REGS(sc).u_regs[CON_G7]);
 316   st->cr();
 317 
 318   st->print("O0="); print_location(st, SIG_REGS(sc).u_regs[CON_O0]);
 319   st->print("O1="); print_location(st, SIG_REGS(sc).u_regs[CON_O1]);
 320   st->print("O2="); print_location(st, SIG_REGS(sc).u_regs[CON_O2]);
 321   st->print("O3="); print_location(st, SIG_REGS(sc).u_regs[CON_O3]);
 322   st->print("O4="); print_location(st, SIG_REGS(sc).u_regs[CON_O4]);
 323   st->print("O5="); print_location(st, SIG_REGS(sc).u_regs[CON_O5]);
 324   st->print("O6="); print_location(st, SIG_REGS(sc).u_regs[CON_O6]);
 325   st->print("O7="); print_location(st, SIG_REGS(sc).u_regs[CON_O7]);
 326   st->cr();
 327 
 328   st->print("L0="); print_location(st, sp[L0->sp_offset_in_saved_window()]);
 329   st->print("L1="); print_location(st, sp[L1->sp_offset_in_saved_window()]);
 330   st->print("L2="); print_location(st, sp[L2->sp_offset_in_saved_window()]);
 331   st->print("L3="); print_location(st, sp[L3->sp_offset_in_saved_window()]);
 332   st->print("L4="); print_location(st, sp[L4->sp_offset_in_saved_window()]);
 333   st->print("L5="); print_location(st, sp[L5->sp_offset_in_saved_window()]);
 334   st->print("L6="); print_location(st, sp[L6->sp_offset_in_saved_window()]);
 335   st->print("L7="); print_location(st, sp[L7->sp_offset_in_saved_window()]);
 336   st->cr();
 337 
 338   st->print("I0="); print_location(st, sp[I0->sp_offset_in_saved_window()]);
 339   st->print("I1="); print_location(st, sp[I1->sp_offset_in_saved_window()]);
 340   st->print("I2="); print_location(st, sp[I2->sp_offset_in_saved_window()]);
 341   st->print("I3="); print_location(st, sp[I3->sp_offset_in_saved_window()]);
 342   st->print("I4="); print_location(st, sp[I4->sp_offset_in_saved_window()]);
 343   st->print("I5="); print_location(st, sp[I5->sp_offset_in_saved_window()]);
 344   st->print("I6="); print_location(st, sp[I6->sp_offset_in_saved_window()]);
 345   st->print("I7="); print_location(st, sp[I7->sp_offset_in_saved_window()]);
 346   st->cr();
 347 }
 348 
 349 
 350 address os::Linux::ucontext_get_pc(ucontext_t* uc) {
 351   return (address) SIG_PC((sigcontext*)uc);
 352 }
 353 
 354 intptr_t* os::Linux::ucontext_get_sp(ucontext_t *uc) {
 355   return (intptr_t*)
 356     ((intptr_t)SIG_REGS((sigcontext*)uc).u_regs[CON_O6] + STACK_BIAS);
 357 }
 358 
 359 // not used on Sparc
 360 intptr_t* os::Linux::ucontext_get_fp(ucontext_t *uc) {
 361   ShouldNotReachHere();
 362   return NULL;
 363 }
 364 
 365 // Utility functions
 366 
 367 inline static bool checkPrefetch(sigcontext* uc, address pc) {
 368   if (StubRoutines::is_safefetch_fault(pc)) {
 369     set_cont_address(uc, address(StubRoutines::continuation_for_safefetch_fault(pc)));
 370     return true;
 371   }
 372   return false;
 373 }
 374 
 375 inline static bool checkOverflow(sigcontext* uc,
 376                                  address pc,
 377                                  address addr,
 378                                  JavaThread* thread,
 379                                  address* stub) {
 380   // check if fault address is within thread stack
 381   if (addr < thread->stack_base() &&
 382       addr >= thread->stack_base() - thread->stack_size()) {
 383     // stack overflow
 384     if (thread->in_stack_yellow_zone(addr)) {
 385       thread->disable_stack_yellow_zone();
 386       if (thread->thread_state() == _thread_in_Java) {
 387         // Throw a stack overflow exception.  Guard pages will be reenabled
 388         // while unwinding the stack.
 389         *stub =
 390           SharedRuntime::continuation_for_implicit_exception(thread,
 391                                                              pc,
 392                                                              SharedRuntime::STACK_OVERFLOW);
 393       } else {
 394         // Thread was in the vm or native code.  Return and try to finish.
 395         return true;
 396       }
 397     } else if (thread->in_stack_red_zone(addr)) {
 398       // Fatal red zone violation.  Disable the guard pages and fall through
 399       // to handle_unexpected_exception way down below.
 400       thread->disable_stack_red_zone();
 401       tty->print_raw_cr("An irrecoverable stack overflow has occurred.");
 402 
 403       // This is a likely cause, but hard to verify. Let's just print
 404       // it as a hint.
 405       tty->print_raw_cr("Please check if any of your loaded .so files has "
 406                         "enabled executable stack (see man page execstack(8))");
 407     } else {
 408       // Accessing stack address below sp may cause SEGV if current
 409       // thread has MAP_GROWSDOWN stack. This should only happen when
 410       // current thread was created by user code with MAP_GROWSDOWN flag
 411       // and then attached to VM. See notes in os_linux.cpp.
 412       if (thread->osthread()->expanding_stack() == 0) {
 413         thread->osthread()->set_expanding_stack();
 414         if (os::Linux::manually_expand_stack(thread, addr)) {
 415           thread->osthread()->clear_expanding_stack();
 416           return true;
 417         }
 418         thread->osthread()->clear_expanding_stack();
 419       } else {
 420         fatal("recursive segv. expanding stack.");
 421       }
 422     }
 423   }
 424   return false;
 425 }
 426 
 427 inline static bool checkPollingPage(address pc, address fault, address* stub) {
 428   if (fault == os::get_polling_page()) {
 429     *stub = SharedRuntime::get_poll_stub(pc);
 430     return true;
 431   }
 432   return false;
 433 }
 434 
 435 inline static bool checkByteBuffer(address pc, address* stub) {
 436   // BugId 4454115: A read from a MappedByteBuffer can fault
 437   // here if the underlying file has been truncated.
 438   // Do not crash the VM in such a case.
 439   CodeBlob* cb = CodeCache::find_blob_unsafe(pc);
 440   nmethod* nm = cb->is_nmethod() ? (nmethod*)cb : NULL;
 441   if (nm != NULL && nm->has_unsafe_access()) {
 442     *stub = StubRoutines::handler_for_unsafe_access();
 443     return true;
 444   }
 445   return false;
 446 }
 447 
 448 inline static bool checkVerifyOops(address pc, address fault, address* stub) {
 449   if (pc >= MacroAssembler::_verify_oop_implicit_branch[0]
 450       && pc <  MacroAssembler::_verify_oop_implicit_branch[1] ) {
 451     *stub     =  MacroAssembler::_verify_oop_implicit_branch[2];
 452     warning("fixed up memory fault in +VerifyOops at address "
 453             INTPTR_FORMAT, fault);
 454     return true;
 455   }
 456   return false;
 457 }
 458 
 459 inline static bool checkFPFault(address pc, int code,
 460                                 JavaThread* thread, address* stub) {
 461   if (code == FPE_INTDIV || code == FPE_FLTDIV) {
 462     *stub =
 463       SharedRuntime::
 464       continuation_for_implicit_exception(thread,
 465                                           pc,
 466                                           SharedRuntime::IMPLICIT_DIVIDE_BY_ZERO);
 467     return true;
 468   }
 469   return false;
 470 }
 471 
 472 inline static bool checkNullPointer(address pc, intptr_t fault,
 473                                     JavaThread* thread, address* stub) {
 474   if (!MacroAssembler::needs_explicit_null_check(fault)) {
 475     // Determination of interpreter/vtable stub/compiled code null
 476     // exception
 477     *stub =
 478       SharedRuntime::
 479       continuation_for_implicit_exception(thread, pc,
 480                                           SharedRuntime::IMPLICIT_NULL);
 481     return true;
 482   }
 483   return false;
 484 }
 485 
 486 inline static bool checkFastJNIAccess(address pc, address* stub) {
 487   address addr = JNI_FastGetField::find_slowcase_pc(pc);
 488   if (addr != (address)-1) {
 489     *stub = addr;
 490     return true;
 491   }
 492   return false;
 493 }
 494 
 495 inline static bool checkSerializePage(JavaThread* thread, address addr) {
 496   return os::is_memory_serialize_page(thread, addr);
 497 }
 498 
 499 inline static bool checkZombie(sigcontext* uc, address* pc, address* stub) {
 500   if (nativeInstruction_at(*pc)->is_zombie()) {
 501     // zombie method (ld [%g0],%o7 instruction)
 502     *stub = SharedRuntime::get_handle_wrong_method_stub();
 503 
 504     // At the stub it needs to look like a call from the caller of this
 505     // method (not a call from the segv site).
 506     *pc = (address)SIG_REGS(uc).u_regs[CON_O7];
 507     return true;
 508   }
 509   return false;
 510 }
 511 
 512 inline static bool checkICMiss(sigcontext* uc, address* pc, address* stub) {
 513 #ifdef COMPILER2
 514   if (nativeInstruction_at(*pc)->is_ic_miss_trap()) {
 515 #ifdef ASSERT
 516 #ifdef TIERED
 517     CodeBlob* cb = CodeCache::find_blob_unsafe(*pc);
 518     assert(cb->is_compiled_by_c2(), "Wrong compiler");
 519 #endif // TIERED
 520 #endif // ASSERT
 521     // Inline cache missed and user trap "Tne G0+ST_RESERVED_FOR_USER_0+2" taken.
 522     *stub = SharedRuntime::get_ic_miss_stub();
 523     // At the stub it needs to look like a call from the caller of this
 524     // method (not a call from the segv site).
 525     *pc = (address)SIG_REGS(uc).u_regs[CON_O7];
 526     return true;
 527   }
 528 #endif  // COMPILER2
 529   return false;
 530 }
 531 
 532 extern "C" JNIEXPORT int
 533 JVM_handle_linux_signal(int sig,
 534                         siginfo_t* info,
 535                         void* ucVoid,
 536                         int abort_if_unrecognized) {
 537   // in fact this isn't ucontext_t* at all, but struct sigcontext*
 538   // but Linux porting layer uses ucontext_t, so to minimize code change
 539   // we cast as needed
 540   ucontext_t* ucFake = (ucontext_t*) ucVoid;
 541   sigcontext* uc = (sigcontext*)ucVoid;
 542 
 543   Thread* t = ThreadLocalStorage::get_thread_slow();
 544 
 545   // Must do this before SignalHandlerMark, if crash protection installed we will longjmp away
 546   // (no destructors can be run)
 547   os::ThreadCrashProtection::check_crash_protection(sig, t);
 548 
 549   SignalHandlerMark shm(t);
 550 
 551   // Note: it's not uncommon that JNI code uses signal/sigset to install
 552   // then restore certain signal handler (e.g. to temporarily block SIGPIPE,
 553   // or have a SIGILL handler when detecting CPU type). When that happens,
 554   // JVM_handle_linux_signal() might be invoked with junk info/ucVoid. To
 555   // avoid unnecessary crash when libjsig is not preloaded, try handle signals
 556   // that do not require siginfo/ucontext first.
 557 
 558   if (sig == SIGPIPE || sig == SIGXFSZ) {
 559     // allow chained handler to go first
 560     if (os::Linux::chained_handler(sig, info, ucVoid)) {
 561       return true;
 562     } else {
 563       if (PrintMiscellaneous && (WizardMode || Verbose)) {
 564         char buf[64];
 565         warning("Ignoring %s - see bugs 4229104 or 646499219",
 566                 os::exception_name(sig, buf, sizeof(buf)));
 567       }
 568       return true;
 569     }
 570   }
 571 
 572   JavaThread* thread = NULL;
 573   VMThread* vmthread = NULL;
 574   if (os::Linux::signal_handlers_are_installed) {
 575     if (t != NULL ){
 576       if(t->is_Java_thread()) {
 577         thread = (JavaThread*)t;
 578       }
 579       else if(t->is_VM_thread()){
 580         vmthread = (VMThread *)t;
 581       }
 582     }
 583   }
 584 
 585   // decide if this trap can be handled by a stub
 586   address stub = NULL;
 587   address pc = NULL;
 588   address npc = NULL;
 589 
 590   //%note os_trap_1
 591   if (info != NULL && uc != NULL && thread != NULL) {
 592     pc = address(SIG_PC(uc));
 593     npc = address(SIG_NPC(uc));
 594 
 595     // Check to see if we caught the safepoint code in the
 596     // process of write protecting the memory serialization page.
 597     // It write enables the page immediately after protecting it
 598     // so we can just return to retry the write.
 599     if ((sig == SIGSEGV) && checkSerializePage(thread, (address)info->si_addr)) {
 600       // Block current thread until the memory serialize page permission restored.
 601       os::block_on_serialize_page_trap();
 602       return 1;
 603     }
 604 
 605     if (checkPrefetch(uc, pc)) {
 606       return 1;
 607     }
 608 
 609     // Handle ALL stack overflow variations here
 610     if (sig == SIGSEGV) {
 611       if (checkOverflow(uc, pc, (address)info->si_addr, thread, &stub)) {
 612         return 1;
 613       }
 614     }
 615 
 616     if (sig == SIGBUS &&
 617         thread->thread_state() == _thread_in_vm &&
 618         thread->doing_unsafe_access()) {
 619       stub = StubRoutines::handler_for_unsafe_access();
 620     }
 621 
 622     if (thread->thread_state() == _thread_in_Java) {
 623       do {
 624         // Java thread running in Java code => find exception handler if any
 625         // a fault inside compiled code, the interpreter, or a stub
 626 
 627         if ((sig == SIGSEGV) && checkPollingPage(pc, (address)info->si_addr, &stub)) {
 628           break;
 629         }
 630 
 631         if ((sig == SIGBUS) && checkByteBuffer(pc, &stub)) {
 632           break;
 633         }
 634 
 635         if ((sig == SIGSEGV || sig == SIGBUS) &&
 636             checkVerifyOops(pc, (address)info->si_addr, &stub)) {
 637           break;
 638         }
 639 
 640         if ((sig == SIGSEGV) && checkZombie(uc, &pc, &stub)) {
 641           break;
 642         }
 643 
 644         if ((sig == SIGILL) && checkICMiss(uc, &pc, &stub)) {
 645           break;
 646         }
 647 
 648         if ((sig == SIGFPE) && checkFPFault(pc, info->si_code, thread, &stub)) {
 649           break;
 650         }
 651 
 652         if ((sig == SIGSEGV) &&
 653             checkNullPointer(pc, (intptr_t)info->si_addr, thread, &stub)) {
 654           break;
 655         }
 656       } while (0);
 657 
 658       // jni_fast_Get<Primitive>Field can trap at certain pc's if a GC kicks in
 659       // and the heap gets shrunk before the field access.
 660       if ((sig == SIGSEGV) || (sig == SIGBUS)) {
 661         checkFastJNIAccess(pc, &stub);
 662       }
 663     }
 664 
 665     if (stub != NULL) {
 666       // save all thread context in case we need to restore it
 667       thread->set_saved_exception_pc(pc);
 668       thread->set_saved_exception_npc(npc);
 669       set_cont_address(uc, stub);
 670       return true;
 671     }
 672   }
 673 
 674   // signal-chaining
 675   if (os::Linux::chained_handler(sig, info, ucVoid)) {
 676     return true;
 677   }
 678 
 679   if (!abort_if_unrecognized) {
 680     // caller wants another chance, so give it to him
 681     return false;
 682   }
 683 
 684   if (pc == NULL && uc != NULL) {
 685     pc = os::Linux::ucontext_get_pc((ucontext_t*)uc);
 686   }
 687 
 688   // unmask current signal
 689   sigset_t newset;
 690   sigemptyset(&newset);
 691   sigaddset(&newset, sig);
 692   sigprocmask(SIG_UNBLOCK, &newset, NULL);
 693 
 694   VMError err(t, sig, pc, info, ucVoid);
 695   err.report_and_die();
 696 
 697   ShouldNotReachHere();
 698 }
 699 
 700 void os::Linux::init_thread_fpu_state(void) {
 701   // Nothing to do
 702 }
 703 
 704 int os::Linux::get_fpu_control_word() {
 705   return 0;
 706 }
 707 
 708 void os::Linux::set_fpu_control_word(int fpu) {
 709   // nothing
 710 }
 711 
 712 bool os::is_allocatable(size_t bytes) {
 713 #ifdef _LP64
 714   return true;
 715 #else
 716   if (bytes < 2 * G) {
 717     return true;
 718   }
 719 
 720   char* addr = reserve_memory(bytes, NULL);
 721 
 722   if (addr != NULL) {
 723     release_memory(addr, bytes);
 724   }
 725 
 726   return addr != NULL;
 727 #endif // _LP64
 728 }
 729 
 730 ///////////////////////////////////////////////////////////////////////////////
 731 // thread stack
 732 
 733 size_t os::Linux::min_stack_allowed  = 128 * K;
 734 
 735 // pthread on Ubuntu is always in floating stack mode
 736 bool os::Linux::supports_variable_stack_size() {  return true; }
 737 
 738 // return default stack size for thr_type
 739 size_t os::Linux::default_stack_size(os::ThreadType thr_type) {
 740   // default stack size (compiler thread needs larger stack)
 741   size_t s = (thr_type == os::compiler_thread ? 4 * M : 1 * M);
 742   return s;
 743 }
 744 
 745 size_t os::Linux::default_guard_size(os::ThreadType thr_type) {
 746   // Creating guard page is very expensive. Java thread has HotSpot
 747   // guard page, only enable glibc guard page for non-Java threads.
 748   return (thr_type == java_thread ? 0 : page_size());
 749 }
 750 
 751 #ifndef PRODUCT
 752 void os::verify_stack_alignment() {
 753 }
 754 #endif