src/os_cpu/linux_sparc/vm/os_linux_sparc.cpp

Wed, 02 Jul 2008 12:55:16 -0700

author
xdono
date
Wed, 02 Jul 2008 12:55:16 -0700
changeset 631
d1605aabd0a1
parent 568
435e64505015
child 1845
f03d0a26bf83
permissions
-rw-r--r--

6719955: Update copyright year
Summary: Update copyright year for files that have been modified in 2008
Reviewed-by: ohair, tbell

     1 /*
     2  * Copyright 1999-2008 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
    20  * CA 95054 USA or visit www.sun.com if you need additional information or
    21  * have any questions.
    22  *
    23  */
    25 // do not include  precompiled  header file
    27 #include "incls/_os_linux_sparc.cpp.incl"
    29 // Linux/Sparc has rather obscure naming of registers in sigcontext
    30 // different between 32 and 64 bits
    31 #ifdef _LP64
    32 #define SIG_PC(x) ((x)->sigc_regs.tpc)
    33 #define SIG_NPC(x) ((x)->sigc_regs.tnpc)
    34 #define SIG_REGS(x) ((x)->sigc_regs)
    35 #else
    36 #define SIG_PC(x) ((x)->si_regs.pc)
    37 #define SIG_NPC(x) ((x)->si_regs.npc)
    38 #define SIG_REGS(x) ((x)->si_regs)
    39 #endif
    41 // those are to reference registers in sigcontext
    42 enum {
    43   CON_G0 = 0,
    44   CON_G1,
    45   CON_G2,
    46   CON_G3,
    47   CON_G4,
    48   CON_G5,
    49   CON_G6,
    50   CON_G7,
    51   CON_O0,
    52   CON_O1,
    53   CON_O2,
    54   CON_O3,
    55   CON_O4,
    56   CON_O5,
    57   CON_O6,
    58   CON_O7,
    59 };
    61 static inline void set_cont_address(sigcontext* ctx, address addr) {
    62   SIG_PC(ctx)  = (intptr_t)addr;
    63   SIG_NPC(ctx) = (intptr_t)(addr+4);
    64 }
    66 // For Forte Analyzer AsyncGetCallTrace profiling support - thread is
    67 // currently interrupted by SIGPROF.
    68 // os::Solaris::fetch_frame_from_ucontext() tries to skip nested
    69 // signal frames. Currently we don't do that on Linux, so it's the
    70 // same as os::fetch_frame_from_context().
    71 ExtendedPC os::Linux::fetch_frame_from_ucontext(Thread* thread,
    72                                                 ucontext_t* uc,
    73                                                 intptr_t** ret_sp,
    74                                                 intptr_t** ret_fp) {
    75   assert(thread != NULL, "just checking");
    76   assert(ret_sp != NULL, "just checking");
    77   assert(ret_fp != NULL, "just checking");
    79   return os::fetch_frame_from_context(uc, ret_sp, ret_fp);
    80 }
    82 ExtendedPC os::fetch_frame_from_context(void* ucVoid,
    83                                         intptr_t** ret_sp,
    84                                         intptr_t** ret_fp) {
    85   ucontext_t* uc = (ucontext_t*) ucVoid;
    86   ExtendedPC  epc;
    88   if (uc != NULL) {
    89     epc = ExtendedPC(os::Linux::ucontext_get_pc(uc));
    90     if (ret_sp) {
    91       *ret_sp = os::Linux::ucontext_get_sp(uc);
    92     }
    93     if (ret_fp) {
    94       *ret_fp = os::Linux::ucontext_get_fp(uc);
    95     }
    96   } else {
    97     // construct empty ExtendedPC for return value checking
    98     epc = ExtendedPC(NULL);
    99     if (ret_sp) {
   100       *ret_sp = (intptr_t*) NULL;
   101     }
   102     if (ret_fp) {
   103       *ret_fp = (intptr_t*) NULL;
   104     }
   105   }
   107   return epc;
   108 }
   110 frame os::fetch_frame_from_context(void* ucVoid) {
   111   intptr_t* sp;
   112   intptr_t* fp;
   113   ExtendedPC epc = fetch_frame_from_context(ucVoid, &sp, &fp);
   114   return frame(sp, fp, epc.pc());
   115 }
   117 frame os::get_sender_for_C_frame(frame* fr) {
   118   return frame(fr->sender_sp(), fr->link(), fr->sender_pc());
   119 }
   121 frame os::current_frame() {
   122   fprintf(stderr, "current_frame()");
   124   intptr_t* sp = StubRoutines::Sparc::flush_callers_register_windows_func()();
   125   frame myframe(sp, frame::unpatchable,
   126                 CAST_FROM_FN_PTR(address, os::current_frame));
   127   if (os::is_first_C_frame(&myframe)) {
   128     // stack is not walkable
   129     return frame(NULL, frame::unpatchable, NULL);
   130   } else {
   131     return os::get_sender_for_C_frame(&myframe);
   132   }
   133 }
   135 address os::current_stack_pointer() {
   136   register void *sp __asm__ ("sp");
   137   return (address)sp;
   138 }
   140 static void current_stack_region(address* bottom, size_t* size) {
   141   if (os::Linux::is_initial_thread()) {
   142     // initial thread needs special handling because pthread_getattr_np()
   143     // may return bogus value.
   144     *bottom = os::Linux::initial_thread_stack_bottom();
   145     *size = os::Linux::initial_thread_stack_size();
   146   } else {
   147     pthread_attr_t attr;
   149     int rslt = pthread_getattr_np(pthread_self(), &attr);
   151     // JVM needs to know exact stack location, abort if it fails
   152     if (rslt != 0) {
   153       if (rslt == ENOMEM) {
   154         vm_exit_out_of_memory(0, "pthread_getattr_np");
   155       } else {
   156         fatal1("pthread_getattr_np failed with errno = %d", rslt);
   157       }
   158     }
   160     if (pthread_attr_getstack(&attr, (void**)bottom, size) != 0) {
   161       fatal("Can not locate current stack attributes!");
   162     }
   164     pthread_attr_destroy(&attr);
   165   }
   166   assert(os::current_stack_pointer() >= *bottom &&
   167          os::current_stack_pointer() < *bottom + *size, "just checking");
   168 }
   170 address os::current_stack_base() {
   171   address bottom;
   172   size_t size;
   173   current_stack_region(&bottom, &size);
   174   return bottom + size;
   175 }
   177 size_t os::current_stack_size() {
   178   // stack size includes normal stack and HotSpot guard pages
   179   address bottom;
   180   size_t size;
   181   current_stack_region(&bottom, &size);
   182   return size;
   183 }
   185 char* os::non_memory_address_word() {
   186   // Must never look like an address returned by reserve_memory,
   187   // even in its subfields (as defined by the CPU immediate fields,
   188   // if the CPU splits constants across multiple instructions).
   189   // On SPARC, 0 != %hi(any real address), because there is no
   190   // allocation in the first 1Kb of the virtual address space.
   191   return (char*) 0;
   192 }
   194 void os::initialize_thread() {}
   196 void os::print_context(outputStream *st, void *context) {
   197   if (context == NULL) return;
   199   ucontext_t* uc = (ucontext_t*)context;
   200   sigcontext* sc = (sigcontext*)context;
   201   st->print_cr("Registers:");
   203   st->print_cr(" O0=" INTPTR_FORMAT " O1=" INTPTR_FORMAT
   204                " O2=" INTPTR_FORMAT " O3=" INTPTR_FORMAT,
   205                SIG_REGS(sc).u_regs[CON_O0],
   206                SIG_REGS(sc).u_regs[CON_O1],
   207                SIG_REGS(sc).u_regs[CON_O2],
   208                SIG_REGS(sc).u_regs[CON_O3]);
   209   st->print_cr(" O4=" INTPTR_FORMAT " O5=" INTPTR_FORMAT
   210                " O6=" INTPTR_FORMAT " O7=" INTPTR_FORMAT,
   211                SIG_REGS(sc).u_regs[CON_O4],
   212                SIG_REGS(sc).u_regs[CON_O5],
   213                SIG_REGS(sc).u_regs[CON_O6],
   214                SIG_REGS(sc).u_regs[CON_O7]);
   216   st->print_cr(" G1=" INTPTR_FORMAT " G2=" INTPTR_FORMAT
   217                " G3=" INTPTR_FORMAT " G4=" INTPTR_FORMAT,
   218                SIG_REGS(sc).u_regs[CON_G1],
   219                SIG_REGS(sc).u_regs[CON_G2],
   220                SIG_REGS(sc).u_regs[CON_G3],
   221                SIG_REGS(sc).u_regs[CON_G4]);
   222   st->print_cr(" G5=" INTPTR_FORMAT " G6=" INTPTR_FORMAT
   223                " G7=" INTPTR_FORMAT " Y=" INTPTR_FORMAT,
   224                SIG_REGS(sc).u_regs[CON_G5],
   225                SIG_REGS(sc).u_regs[CON_G6],
   226                SIG_REGS(sc).u_regs[CON_G7],
   227                SIG_REGS(sc).y);
   229   st->print_cr(" PC=" INTPTR_FORMAT " nPC=" INTPTR_FORMAT,
   230                SIG_PC(sc),
   231                SIG_NPC(sc));
   232   st->cr();
   233   st->cr();
   235   intptr_t *sp = (intptr_t *)os::Linux::ucontext_get_sp(uc);
   236   st->print_cr("Top of Stack: (sp=" PTR_FORMAT ")", sp);
   237   print_hex_dump(st, (address)sp, (address)(sp + 32), sizeof(intptr_t));
   238   st->cr();
   240   // Note: it may be unsafe to inspect memory near pc. For example, pc may
   241   // point to garbage if entry point in an nmethod is corrupted. Leave
   242   // this at the end, and hope for the best.
   243   address pc = os::Linux::ucontext_get_pc(uc);
   244   st->print_cr("Instructions: (pc=" PTR_FORMAT ")", pc);
   245   print_hex_dump(st, pc - 16, pc + 16, sizeof(char));
   246 }
   249 address os::Linux::ucontext_get_pc(ucontext_t* uc) {
   250   return (address) SIG_PC((sigcontext*)uc);
   251 }
   253 intptr_t* os::Linux::ucontext_get_sp(ucontext_t *uc) {
   254   return (intptr_t*)
   255     ((intptr_t)SIG_REGS((sigcontext*)uc).u_regs[CON_O6] + STACK_BIAS);
   256 }
   258 // not used on Sparc
   259 intptr_t* os::Linux::ucontext_get_fp(ucontext_t *uc) {
   260   ShouldNotReachHere();
   261   return NULL;
   262 }
   264 // Utility functions
   266 extern "C" void Fetch32PFI();
   267 extern "C" void Fetch32Resume();
   268 extern "C" void FetchNPFI();
   269 extern "C" void FetchNResume();
   271 inline static bool checkPrefetch(sigcontext* uc, address pc) {
   272   if (pc == (address) Fetch32PFI) {
   273     set_cont_address(uc, address(Fetch32Resume));
   274     return true;
   275   }
   276   if (pc == (address) FetchNPFI) {
   277     set_cont_address(uc, address(FetchNResume));
   278     return true;
   279   }
   280   return false;
   281 }
   283 inline static bool checkOverflow(sigcontext* uc,
   284                                  address pc,
   285                                  address addr,
   286                                  JavaThread* thread,
   287                                  address* stub) {
   288   // check if fault address is within thread stack
   289   if (addr < thread->stack_base() &&
   290       addr >= thread->stack_base() - thread->stack_size()) {
   291     // stack overflow
   292     if (thread->in_stack_yellow_zone(addr)) {
   293       thread->disable_stack_yellow_zone();
   294       if (thread->thread_state() == _thread_in_Java) {
   295         // Throw a stack overflow exception.  Guard pages will be reenabled
   296         // while unwinding the stack.
   297         *stub =
   298           SharedRuntime::continuation_for_implicit_exception(thread,
   299                                                              pc,
   300                                                              SharedRuntime::STACK_OVERFLOW);
   301       } else {
   302         // Thread was in the vm or native code.  Return and try to finish.
   303         return true;
   304       }
   305     } else if (thread->in_stack_red_zone(addr)) {
   306       // Fatal red zone violation.  Disable the guard pages and fall through
   307       // to handle_unexpected_exception way down below.
   308       thread->disable_stack_red_zone();
   309       tty->print_raw_cr("An irrecoverable stack overflow has occurred.");
   310     } else {
   311       // Accessing stack address below sp may cause SEGV if current
   312       // thread has MAP_GROWSDOWN stack. This should only happen when
   313       // current thread was created by user code with MAP_GROWSDOWN flag
   314       // and then attached to VM. See notes in os_linux.cpp.
   315       if (thread->osthread()->expanding_stack() == 0) {
   316         thread->osthread()->set_expanding_stack();
   317         if (os::Linux::manually_expand_stack(thread, addr)) {
   318           thread->osthread()->clear_expanding_stack();
   319           return true;
   320         }
   321         thread->osthread()->clear_expanding_stack();
   322       } else {
   323         fatal("recursive segv. expanding stack.");
   324       }
   325     }
   326   }
   327   return false;
   328 }
   330 inline static bool checkPollingPage(address pc, address fault, address* stub) {
   331   if (fault == os::get_polling_page()) {
   332     *stub = SharedRuntime::get_poll_stub(pc);
   333     return true;
   334   }
   335   return false;
   336 }
   338 inline static bool checkByteBuffer(address pc, address* stub) {
   339   // BugId 4454115: A read from a MappedByteBuffer can fault
   340   // here if the underlying file has been truncated.
   341   // Do not crash the VM in such a case.
   342   CodeBlob* cb = CodeCache::find_blob_unsafe(pc);
   343   nmethod* nm = cb->is_nmethod() ? (nmethod*)cb : NULL;
   344   if (nm != NULL && nm->has_unsafe_access()) {
   345     *stub = StubRoutines::handler_for_unsafe_access();
   346     return true;
   347   }
   348   return false;
   349 }
   351 inline static bool checkVerifyOops(address pc, address fault, address* stub) {
   352   if (pc >= MacroAssembler::_verify_oop_implicit_branch[0]
   353       && pc <  MacroAssembler::_verify_oop_implicit_branch[1] ) {
   354     *stub     =  MacroAssembler::_verify_oop_implicit_branch[2];
   355     warning("fixed up memory fault in +VerifyOops at address "
   356             INTPTR_FORMAT, fault);
   357     return true;
   358   }
   359   return false;
   360 }
   362 inline static bool checkFPFault(address pc, int code,
   363                                 JavaThread* thread, address* stub) {
   364   if (code == FPE_INTDIV || code == FPE_FLTDIV) {
   365     *stub =
   366       SharedRuntime::
   367       continuation_for_implicit_exception(thread,
   368                                           pc,
   369                                           SharedRuntime::IMPLICIT_DIVIDE_BY_ZERO);
   370     return true;
   371   }
   372   return false;
   373 }
   375 inline static bool checkNullPointer(address pc, intptr_t fault,
   376                                     JavaThread* thread, address* stub) {
   377   if (!MacroAssembler::needs_explicit_null_check(fault)) {
   378     // Determination of interpreter/vtable stub/compiled code null
   379     // exception
   380     *stub =
   381       SharedRuntime::
   382       continuation_for_implicit_exception(thread, pc,
   383                                           SharedRuntime::IMPLICIT_NULL);
   384     return true;
   385   }
   386   return false;
   387 }
   389 inline static bool checkFastJNIAccess(address pc, address* stub) {
   390   address addr = JNI_FastGetField::find_slowcase_pc(pc);
   391   if (addr != (address)-1) {
   392     *stub = addr;
   393     return true;
   394   }
   395   return false;
   396 }
   398 inline static bool checkSerializePage(JavaThread* thread, address addr) {
   399   return os::is_memory_serialize_page(thread, addr);
   400 }
   402 inline static bool checkZombie(sigcontext* uc, address* pc, address* stub) {
   403   if (nativeInstruction_at(*pc)->is_zombie()) {
   404     // zombie method (ld [%g0],%o7 instruction)
   405     *stub = SharedRuntime::get_handle_wrong_method_stub();
   407     // At the stub it needs to look like a call from the caller of this
   408     // method (not a call from the segv site).
   409     *pc = (address)SIG_REGS(uc).u_regs[CON_O7];
   410     return true;
   411   }
   412   return false;
   413 }
   415 inline static bool checkICMiss(sigcontext* uc, address* pc, address* stub) {
   416 #ifdef COMPILER2
   417   if (nativeInstruction_at(*pc)->is_ic_miss_trap()) {
   418 #ifdef ASSERT
   419 #ifdef TIERED
   420     CodeBlob* cb = CodeCache::find_blob_unsafe(pc);
   421     assert(cb->is_compiled_by_c2(), "Wrong compiler");
   422 #endif // TIERED
   423 #endif // ASSERT
   424     // Inline cache missed and user trap "Tne G0+ST_RESERVED_FOR_USER_0+2" taken.
   425     *stub = SharedRuntime::get_ic_miss_stub();
   426     // At the stub it needs to look like a call from the caller of this
   427     // method (not a call from the segv site).
   428     *pc = (address)SIG_REGS(uc).u_regs[CON_O7];
   429     return true;
   430   }
   431 #endif  // COMPILER2
   432   return false;
   433 }
   435 extern "C" int
   436 JVM_handle_linux_signal(int sig,
   437                         siginfo_t* info,
   438                         void* ucVoid,
   439                         int abort_if_unrecognized) {
   440   // in fact this isn't ucontext_t* at all, but struct sigcontext*
   441   // but Linux porting layer uses ucontext_t, so to minimize code change
   442   // we cast as needed
   443   ucontext_t* ucFake = (ucontext_t*) ucVoid;
   444   sigcontext* uc = (sigcontext*)ucVoid;
   446   Thread* t = ThreadLocalStorage::get_thread_slow();
   448   SignalHandlerMark shm(t);
   450   // Note: it's not uncommon that JNI code uses signal/sigset to install
   451   // then restore certain signal handler (e.g. to temporarily block SIGPIPE,
   452   // or have a SIGILL handler when detecting CPU type). When that happens,
   453   // JVM_handle_linux_signal() might be invoked with junk info/ucVoid. To
   454   // avoid unnecessary crash when libjsig is not preloaded, try handle signals
   455   // that do not require siginfo/ucontext first.
   457   if (sig == SIGPIPE || sig == SIGXFSZ) {
   458     // allow chained handler to go first
   459     if (os::Linux::chained_handler(sig, info, ucVoid)) {
   460       return true;
   461     } else {
   462       if (PrintMiscellaneous && (WizardMode || Verbose)) {
   463         char buf[64];
   464         warning("Ignoring %s - see bugs 4229104 or 646499219",
   465                 os::exception_name(sig, buf, sizeof(buf)));
   466       }
   467       return true;
   468     }
   469   }
   471   JavaThread* thread = NULL;
   472   VMThread* vmthread = NULL;
   473   if (os::Linux::signal_handlers_are_installed) {
   474     if (t != NULL ){
   475       if(t->is_Java_thread()) {
   476         thread = (JavaThread*)t;
   477       }
   478       else if(t->is_VM_thread()){
   479         vmthread = (VMThread *)t;
   480       }
   481     }
   482   }
   484   // decide if this trap can be handled by a stub
   485   address stub = NULL;
   486   address pc = NULL;
   487   address npc = NULL;
   489   //%note os_trap_1
   490   if (info != NULL && uc != NULL && thread != NULL) {
   491     pc = address(SIG_PC(uc));
   492     npc = address(SIG_NPC(uc));
   494     // Check to see if we caught the safepoint code in the
   495     // process of write protecting the memory serialization page.
   496     // It write enables the page immediately after protecting it
   497     // so we can just return to retry the write.
   498     if ((sig == SIGSEGV) && checkSerializePage(thread, (address)info->si_addr)) {
   499       // Block current thread until the memory serialize page permission restored.
   500       os::block_on_serialize_page_trap();
   501       return 1;
   502     }
   504     if (checkPrefetch(uc, pc)) {
   505       return 1;
   506     }
   508     // Handle ALL stack overflow variations here
   509     if (sig == SIGSEGV) {
   510       if (checkOverflow(uc, pc, (address)info->si_addr, thread, &stub)) {
   511         return 1;
   512       }
   513     }
   515     if (sig == SIGBUS &&
   516         thread->thread_state() == _thread_in_vm &&
   517         thread->doing_unsafe_access()) {
   518       stub = StubRoutines::handler_for_unsafe_access();
   519     }
   521     if (thread->thread_state() == _thread_in_Java) {
   522       do {
   523         // Java thread running in Java code => find exception handler if any
   524         // a fault inside compiled code, the interpreter, or a stub
   526         if ((sig == SIGSEGV) && checkPollingPage(pc, (address)info->si_addr, &stub)) {
   527           break;
   528         }
   530         if ((sig == SIGBUS) && checkByteBuffer(pc, &stub)) {
   531           break;
   532         }
   534         if ((sig == SIGSEGV || sig == SIGBUS) &&
   535             checkVerifyOops(pc, (address)info->si_addr, &stub)) {
   536           break;
   537         }
   539         if ((sig == SIGSEGV) && checkZombie(uc, &pc, &stub)) {
   540           break;
   541         }
   543         if ((sig == SIGILL) && checkICMiss(uc, &pc, &stub)) {
   544           break;
   545         }
   547         if ((sig == SIGFPE) && checkFPFault(pc, info->si_code, thread, &stub)) {
   548           break;
   549         }
   551         if ((sig == SIGSEGV) &&
   552             checkNullPointer(pc, (intptr_t)info->si_addr, thread, &stub)) {
   553           break;
   554         }
   555       } while (0);
   557       // jni_fast_Get<Primitive>Field can trap at certain pc's if a GC kicks in
   558       // and the heap gets shrunk before the field access.
   559       if ((sig == SIGSEGV) || (sig == SIGBUS)) {
   560         checkFastJNIAccess(pc, &stub);
   561       }
   562     }
   564     if (stub != NULL) {
   565       // save all thread context in case we need to restore it
   566       thread->set_saved_exception_pc(pc);
   567       thread->set_saved_exception_npc(npc);
   568       set_cont_address(uc, stub);
   569       return true;
   570     }
   571   }
   573   // signal-chaining
   574   if (os::Linux::chained_handler(sig, info, ucVoid)) {
   575     return true;
   576   }
   578   if (!abort_if_unrecognized) {
   579     // caller wants another chance, so give it to him
   580     return false;
   581   }
   583   if (pc == NULL && uc != NULL) {
   584     pc = os::Linux::ucontext_get_pc((ucontext_t*)uc);
   585   }
   587   // unmask current signal
   588   sigset_t newset;
   589   sigemptyset(&newset);
   590   sigaddset(&newset, sig);
   591   sigprocmask(SIG_UNBLOCK, &newset, NULL);
   593   VMError err(t, sig, pc, info, ucVoid);
   594   err.report_and_die();
   596   ShouldNotReachHere();
   597 }
   599 void os::Linux::init_thread_fpu_state(void) {
   600   // Nothing to do
   601 }
   603 int os::Linux::get_fpu_control_word() {
   604   return 0;
   605 }
   607 void os::Linux::set_fpu_control_word(int fpu) {
   608   // nothing
   609 }
   611 bool os::is_allocatable(size_t bytes) {
   612 #ifdef _LP64
   613   return true;
   614 #else
   615   if (bytes < 2 * G) {
   616     return true;
   617   }
   619   char* addr = reserve_memory(bytes, NULL);
   621   if (addr != NULL) {
   622     release_memory(addr, bytes);
   623   }
   625   return addr != NULL;
   626 #endif // _LP64
   627 }
   629 ///////////////////////////////////////////////////////////////////////////////
   630 // thread stack
   632 size_t os::Linux::min_stack_allowed  = 128 * K;
   634 // pthread on Ubuntu is always in floating stack mode
   635 bool os::Linux::supports_variable_stack_size() {  return true; }
   637 // return default stack size for thr_type
   638 size_t os::Linux::default_stack_size(os::ThreadType thr_type) {
   639   // default stack size (compiler thread needs larger stack)
   640   size_t s = (thr_type == os::compiler_thread ? 4 * M : 1 * M);
   641   return s;
   642 }
   644 size_t os::Linux::default_guard_size(os::ThreadType thr_type) {
   645   // Creating guard page is very expensive. Java thread has HotSpot
   646   // guard page, only enable glibc guard page for non-Java threads.
   647   return (thr_type == java_thread ? 0 : page_size());
   648 }

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