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 "jvm.h"
  27 #include "asm/macroAssembler.hpp"
  28 #include "classfile/classLoader.hpp"
  29 #include "classfile/systemDictionary.hpp"
  30 #include "classfile/vmSymbols.hpp"
  31 #include "code/codeCache.hpp"
  32 #include "code/icBuffer.hpp"
  33 #include "code/vtableStubs.hpp"
  34 #include "interpreter/interpreter.hpp"
  35 #include "logging/log.hpp"
  36 #include "memory/allocation.inline.hpp"
  37 #include "os_share_linux.hpp"
  38 #include "prims/jniFastGetField.hpp"
  39 #include "prims/jvm_misc.hpp"
  40 #include "runtime/arguments.hpp"
  41 #include "runtime/extendedPC.hpp"
  42 #include "runtime/frame.inline.hpp"
  43 #include "runtime/interfaceSupport.inline.hpp"
  44 #include "runtime/java.hpp"
  45 #include "runtime/javaCalls.hpp"
  46 #include "runtime/mutexLocker.hpp"
  47 #include "runtime/osThread.hpp"
  48 #include "runtime/sharedRuntime.hpp"
  49 #include "runtime/stubRoutines.hpp"
  50 #include "runtime/thread.inline.hpp"
  51 #include "runtime/timer.hpp"
  52 #include "services/memTracker.hpp"
  53 #include "utilities/align.hpp"
  54 #include "utilities/debug.hpp"
  55 #include "utilities/events.hpp"
  56 #include "utilities/vmError.hpp"
  57 
  58 // put OS-includes here
  59 # include <sys/types.h>
  60 # include <sys/mman.h>
  61 # include <pthread.h>
  62 # include <signal.h>
  63 # include <errno.h>
  64 # include <dlfcn.h>
  65 # include <stdlib.h>
  66 # include <stdio.h>
  67 # include <unistd.h>
  68 # include <sys/resource.h>
  69 # include <pthread.h>
  70 # include <sys/stat.h>
  71 # include <sys/time.h>
  72 # include <sys/utsname.h>
  73 # include <sys/socket.h>
  74 # include <sys/wait.h>
  75 # include <pwd.h>
  76 # include <poll.h>
  77 # include <ucontext.h>
  78 #ifndef AMD64
  79 # include <fpu_control.h>
  80 #endif
  81 
  82 #ifdef AMD64
  83 #define REG_SP REG_RSP
  84 #define REG_PC REG_RIP
  85 #define REG_FP REG_RBP
  86 #define SPELL_REG_SP "rsp"
  87 #define SPELL_REG_FP "rbp"
  88 #else
  89 #define REG_SP REG_UESP
  90 #define REG_PC REG_EIP
  91 #define REG_FP REG_EBP
  92 #define SPELL_REG_SP "esp"
  93 #define SPELL_REG_FP "ebp"
  94 #endif // AMD64
  95 
  96 address os::current_stack_pointer() {
  97 #ifdef SPARC_WORKS
  98   register void *esp;
  99   __asm__("mov %%" SPELL_REG_SP ", %0":"=r"(esp));
 100   return (address) ((char*)esp + sizeof(long)*2);
 101 #elif defined(__clang__)
 102   intptr_t* esp;
 103   __asm__ __volatile__ ("mov %%" SPELL_REG_SP ", %0":"=r"(esp):);
 104   return (address) esp;
 105 #else
 106   register void *esp __asm__ (SPELL_REG_SP);
 107   return (address) esp;
 108 #endif
 109 }
 110 
 111 char* os::non_memory_address_word() {
 112   // Must never look like an address returned by reserve_memory,
 113   // even in its subfields (as defined by the CPU immediate fields,
 114   // if the CPU splits constants across multiple instructions).
 115 
 116   return (char*) -1;
 117 }
 118 
 119 void os::initialize_thread(Thread* thr) {
 120 // Nothing to do.
 121 }
 122 
 123 address os::Linux::ucontext_get_pc(const ucontext_t * uc) {
 124   return (address)uc->uc_mcontext.gregs[REG_PC];
 125 }
 126 
 127 void os::Linux::ucontext_set_pc(ucontext_t * uc, address pc) {
 128   uc->uc_mcontext.gregs[REG_PC] = (intptr_t)pc;
 129 }
 130 
 131 intptr_t* os::Linux::ucontext_get_sp(const ucontext_t * uc) {
 132   return (intptr_t*)uc->uc_mcontext.gregs[REG_SP];
 133 }
 134 
 135 intptr_t* os::Linux::ucontext_get_fp(const ucontext_t * uc) {
 136   return (intptr_t*)uc->uc_mcontext.gregs[REG_FP];
 137 }
 138 
 139 // For Forte Analyzer AsyncGetCallTrace profiling support - thread
 140 // is currently interrupted by SIGPROF.
 141 // os::Solaris::fetch_frame_from_ucontext() tries to skip nested signal
 142 // frames. Currently we don't do that on Linux, so it's the same as
 143 // os::fetch_frame_from_context().
 144 // This method is also used for stack overflow signal handling.
 145 ExtendedPC os::Linux::fetch_frame_from_ucontext(Thread* thread,
 146   const ucontext_t* uc, intptr_t** ret_sp, intptr_t** ret_fp) {
 147 
 148   assert(thread != NULL, "just checking");
 149   assert(ret_sp != NULL, "just checking");
 150   assert(ret_fp != NULL, "just checking");
 151 
 152   return os::fetch_frame_from_context(uc, ret_sp, ret_fp);
 153 }
 154 
 155 ExtendedPC os::fetch_frame_from_context(const void* ucVoid,
 156                     intptr_t** ret_sp, intptr_t** ret_fp) {
 157 
 158   ExtendedPC  epc;
 159   const ucontext_t* uc = (const ucontext_t*)ucVoid;
 160 
 161   if (uc != NULL) {
 162     epc = ExtendedPC(os::Linux::ucontext_get_pc(uc));
 163     if (ret_sp) *ret_sp = os::Linux::ucontext_get_sp(uc);
 164     if (ret_fp) *ret_fp = os::Linux::ucontext_get_fp(uc);
 165   } else {
 166     // construct empty ExtendedPC for return value checking
 167     epc = ExtendedPC(NULL);
 168     if (ret_sp) *ret_sp = (intptr_t *)NULL;
 169     if (ret_fp) *ret_fp = (intptr_t *)NULL;
 170   }
 171 
 172   return epc;
 173 }
 174 
 175 frame os::fetch_frame_from_context(const void* ucVoid) {
 176   intptr_t* sp;
 177   intptr_t* fp;
 178   ExtendedPC epc = fetch_frame_from_context(ucVoid, &sp, &fp);
 179   return frame(sp, fp, epc.pc());
 180 }
 181 
 182 frame os::fetch_frame_from_ucontext(Thread* thread, void* ucVoid) {
 183   intptr_t* sp;
 184   intptr_t* fp;
 185   ExtendedPC epc = os::Linux::fetch_frame_from_ucontext(thread, (ucontext_t*)ucVoid, &sp, &fp);
 186   return frame(sp, fp, epc.pc());
 187 }
 188 
 189 bool os::Linux::get_frame_at_stack_banging_point(JavaThread* thread, ucontext_t* uc, frame* fr) {
 190   address pc = (address) os::Linux::ucontext_get_pc(uc);
 191   if (Interpreter::contains(pc)) {
 192     // interpreter performs stack banging after the fixed frame header has
 193     // been generated while the compilers perform it before. To maintain
 194     // semantic consistency between interpreted and compiled frames, the
 195     // method returns the Java sender of the current frame.
 196     *fr = os::fetch_frame_from_ucontext(thread, uc);
 197     if (!fr->is_first_java_frame()) {
 198       // get_frame_at_stack_banging_point() is only called when we
 199       // have well defined stacks so java_sender() calls do not need
 200       // to assert safe_for_sender() first.
 201       *fr = fr->java_sender();
 202     }
 203   } else {
 204     // more complex code with compiled code
 205     assert(!Interpreter::contains(pc), "Interpreted methods should have been handled above");
 206     CodeBlob* cb = CodeCache::find_blob(pc);
 207     if (cb == NULL || !cb->is_nmethod() || cb->is_frame_complete_at(pc)) {
 208       // Not sure where the pc points to, fallback to default
 209       // stack overflow handling
 210       return false;
 211     } else {
 212       // in compiled code, the stack banging is performed just after the return pc
 213       // has been pushed on the stack
 214       intptr_t* fp = os::Linux::ucontext_get_fp(uc);
 215       intptr_t* sp = os::Linux::ucontext_get_sp(uc);
 216       *fr = frame(sp + 1, fp, (address)*sp);
 217       if (!fr->is_java_frame()) {
 218         assert(!fr->is_first_frame(), "Safety check");
 219         // See java_sender() comment above.
 220         *fr = fr->java_sender();
 221       }
 222     }
 223   }
 224   assert(fr->is_java_frame(), "Safety check");
 225   return true;
 226 }
 227 
 228 // By default, gcc always save frame pointer (%ebp/%rbp) on stack. It may get
 229 // turned off by -fomit-frame-pointer,
 230 frame os::get_sender_for_C_frame(frame* fr) {
 231   return frame(fr->sender_sp(), fr->link(), fr->sender_pc());
 232 }
 233 
 234 intptr_t* _get_previous_fp() {
 235 #ifdef SPARC_WORKS
 236   register intptr_t **ebp;
 237   __asm__("mov %%" SPELL_REG_FP ", %0":"=r"(ebp));
 238 #elif defined(__clang__)
 239   intptr_t **ebp;
 240   __asm__ __volatile__ ("mov %%" SPELL_REG_FP ", %0":"=r"(ebp):);
 241 #else
 242   register intptr_t **ebp __asm__ (SPELL_REG_FP);
 243 #endif
 244   // ebp is for this frame (_get_previous_fp). We want the ebp for the
 245   // caller of os::current_frame*(), so go up two frames. However, for
 246   // optimized builds, _get_previous_fp() will be inlined, so only go
 247   // up 1 frame in that case.
 248 #ifdef _NMT_NOINLINE_
 249   return **(intptr_t***)ebp;
 250 #else
 251   return *ebp;
 252 #endif
 253 }
 254 
 255 
 256 frame os::current_frame() {
 257   intptr_t* fp = _get_previous_fp();
 258   frame myframe((intptr_t*)os::current_stack_pointer(),
 259                 (intptr_t*)fp,
 260                 CAST_FROM_FN_PTR(address, os::current_frame));
 261   if (os::is_first_C_frame(&myframe)) {
 262     // stack is not walkable
 263     return frame();
 264   } else {
 265     return os::get_sender_for_C_frame(&myframe);
 266   }
 267 }
 268 
 269 // Utility functions
 270 
 271 // From IA32 System Programming Guide
 272 enum {
 273   trap_page_fault = 0xE
 274 };
 275 
 276 extern "C" JNIEXPORT int
 277 JVM_handle_linux_signal(int sig,
 278                         siginfo_t* info,
 279                         void* ucVoid,
 280                         int abort_if_unrecognized) {
 281   ucontext_t* uc = (ucontext_t*) ucVoid;
 282 
 283   Thread* t = Thread::current_or_null_safe();
 284 
 285   // Must do this before SignalHandlerMark, if crash protection installed we will longjmp away
 286   // (no destructors can be run)
 287   os::ThreadCrashProtection::check_crash_protection(sig, t);
 288 
 289   SignalHandlerMark shm(t);
 290 
 291   // Note: it's not uncommon that JNI code uses signal/sigset to install
 292   // then restore certain signal handler (e.g. to temporarily block SIGPIPE,
 293   // or have a SIGILL handler when detecting CPU type). When that happens,
 294   // JVM_handle_linux_signal() might be invoked with junk info/ucVoid. To
 295   // avoid unnecessary crash when libjsig is not preloaded, try handle signals
 296   // that do not require siginfo/ucontext first.
 297 
 298   if (sig == SIGPIPE || sig == SIGXFSZ) {
 299     // allow chained handler to go first
 300     if (os::Linux::chained_handler(sig, info, ucVoid)) {
 301       return true;
 302     } else {
 303       // Ignoring SIGPIPE/SIGXFSZ - see bugs 4229104 or 6499219
 304       return true;
 305     }
 306   }
 307 
 308 #ifdef CAN_SHOW_REGISTERS_ON_ASSERT
 309   if ((sig == SIGSEGV || sig == SIGBUS) && info != NULL && info->si_addr == g_assert_poison) {
 310     handle_assert_poison_fault(ucVoid, info->si_addr);
 311     return 1;
 312   }
 313 #endif
 314 
 315   JavaThread* thread = NULL;
 316   VMThread* vmthread = NULL;
 317   if (os::Linux::signal_handlers_are_installed) {
 318     if (t != NULL ){
 319       if(t->is_Java_thread()) {
 320         thread = (JavaThread*)t;
 321       }
 322       else if(t->is_VM_thread()){
 323         vmthread = (VMThread *)t;
 324       }
 325     }
 326   }
 327 /*
 328   NOTE: does not seem to work on linux.
 329   if (info == NULL || info->si_code <= 0 || info->si_code == SI_NOINFO) {
 330     // can't decode this kind of signal
 331     info = NULL;
 332   } else {
 333     assert(sig == info->si_signo, "bad siginfo");
 334   }
 335 */
 336   // decide if this trap can be handled by a stub
 337   address stub = NULL;
 338 
 339   address pc          = NULL;
 340 
 341   //%note os_trap_1
 342   if (info != NULL && uc != NULL && thread != NULL) {
 343     pc = (address) os::Linux::ucontext_get_pc(uc);
 344 
 345     if (StubRoutines::is_safefetch_fault(pc)) {
 346       os::Linux::ucontext_set_pc(uc, StubRoutines::continuation_for_safefetch_fault(pc));
 347       return 1;
 348     }
 349 
 350 #ifndef AMD64
 351     // Halt if SI_KERNEL before more crashes get misdiagnosed as Java bugs
 352     // This can happen in any running code (currently more frequently in
 353     // interpreter code but has been seen in compiled code)
 354     if (sig == SIGSEGV && info->si_addr == 0 && info->si_code == SI_KERNEL) {
 355       fatal("An irrecoverable SI_KERNEL SIGSEGV has occurred due "
 356             "to unstable signal handling in this distribution.");
 357     }
 358 #endif // AMD64
 359 
 360     // Handle ALL stack overflow variations here
 361     if (sig == SIGSEGV) {
 362       address addr = (address) info->si_addr;
 363 
 364       // check if fault address is within thread stack
 365       if (thread->on_local_stack(addr)) {
 366         // stack overflow
 367         if (thread->in_stack_yellow_reserved_zone(addr)) {
 368           if (thread->thread_state() == _thread_in_Java) {
 369             if (thread->in_stack_reserved_zone(addr)) {
 370               frame fr;
 371               if (os::Linux::get_frame_at_stack_banging_point(thread, uc, &fr)) {
 372                 assert(fr.is_java_frame(), "Must be a Java frame");
 373                 frame activation =
 374                   SharedRuntime::look_for_reserved_stack_annotated_method(thread, fr);
 375                 if (activation.sp() != NULL) {
 376                   thread->disable_stack_reserved_zone();
 377                   if (activation.is_interpreted_frame()) {
 378                     thread->set_reserved_stack_activation((address)(
 379                       activation.fp() + frame::interpreter_frame_initial_sp_offset));
 380                   } else {
 381                     thread->set_reserved_stack_activation((address)activation.unextended_sp());
 382                   }
 383                   return 1;
 384                 }
 385               }
 386             }
 387             // Throw a stack overflow exception.  Guard pages will be reenabled
 388             // while unwinding the stack.
 389             thread->disable_stack_yellow_reserved_zone();
 390             stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::STACK_OVERFLOW);
 391           } else {
 392             // Thread was in the vm or native code.  Return and try to finish.
 393             thread->disable_stack_yellow_reserved_zone();
 394             return 1;
 395           }
 396         } else if (thread->in_stack_red_zone(addr)) {
 397           // Fatal red zone violation.  Disable the guard pages and fall through
 398           // to handle_unexpected_exception way down below.
 399           thread->disable_stack_red_zone();
 400           tty->print_raw_cr("An irrecoverable stack overflow has occurred.");
 401 
 402           // This is a likely cause, but hard to verify. Let's just print
 403           // it as a hint.
 404           tty->print_raw_cr("Please check if any of your loaded .so files has "
 405                             "enabled executable stack (see man page execstack(8))");
 406         } else {
 407           // Accessing stack address below sp may cause SEGV if current
 408           // thread has MAP_GROWSDOWN stack. This should only happen when
 409           // current thread was created by user code with MAP_GROWSDOWN flag
 410           // and then attached to VM. See notes in os_linux.cpp.
 411           if (thread->osthread()->expanding_stack() == 0) {
 412              thread->osthread()->set_expanding_stack();
 413              if (os::Linux::manually_expand_stack(thread, addr)) {
 414                thread->osthread()->clear_expanding_stack();
 415                return 1;
 416              }
 417              thread->osthread()->clear_expanding_stack();
 418           } else {
 419              fatal("recursive segv. expanding stack.");
 420           }
 421         }
 422       }
 423     }
 424 
 425     if ((sig == SIGSEGV) && VM_Version::is_cpuinfo_segv_addr(pc)) {
 426       // Verify that OS save/restore AVX registers.
 427       stub = VM_Version::cpuinfo_cont_addr();
 428     }
 429 
 430     if (thread->thread_state() == _thread_in_Java) {
 431       // Java thread running in Java code => find exception handler if any
 432       // a fault inside compiled code, the interpreter, or a stub
 433 
 434       if (sig == SIGSEGV && os::is_poll_address((address)info->si_addr)) {
 435         stub = SharedRuntime::get_poll_stub(pc);
 436       } else if (sig == SIGBUS /* && info->si_code == BUS_OBJERR */) {
 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 != NULL) ? cb->as_compiled_method_or_null() : NULL;
 442         if (nm != NULL && nm->has_unsafe_access()) {
 443           address next_pc = Assembler::locate_next_instruction(pc);
 444           stub = SharedRuntime::handle_unsafe_access(thread, next_pc);
 445         }
 446       }
 447       else
 448 
 449 #ifdef AMD64
 450       if (sig == SIGFPE  &&
 451           (info->si_code == FPE_INTDIV || info->si_code == FPE_FLTDIV)) {
 452         stub =
 453           SharedRuntime::
 454           continuation_for_implicit_exception(thread,
 455                                               pc,
 456                                               SharedRuntime::
 457                                               IMPLICIT_DIVIDE_BY_ZERO);
 458 #else
 459       if (sig == SIGFPE /* && info->si_code == FPE_INTDIV */) {
 460         // HACK: si_code does not work on linux 2.2.12-20!!!
 461         int op = pc[0];
 462         if (op == 0xDB) {
 463           // FIST
 464           // TODO: The encoding of D2I in i486.ad can cause an exception
 465           // prior to the fist instruction if there was an invalid operation
 466           // pending. We want to dismiss that exception. From the win_32
 467           // side it also seems that if it really was the fist causing
 468           // the exception that we do the d2i by hand with different
 469           // rounding. Seems kind of weird.
 470           // NOTE: that we take the exception at the NEXT floating point instruction.
 471           assert(pc[0] == 0xDB, "not a FIST opcode");
 472           assert(pc[1] == 0x14, "not a FIST opcode");
 473           assert(pc[2] == 0x24, "not a FIST opcode");
 474           return true;
 475         } else if (op == 0xF7) {
 476           // IDIV
 477           stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_DIVIDE_BY_ZERO);
 478         } else {
 479           // TODO: handle more cases if we are using other x86 instructions
 480           //   that can generate SIGFPE signal on linux.
 481           tty->print_cr("unknown opcode 0x%X with SIGFPE.", op);
 482           fatal("please update this code.");
 483         }
 484 #endif // AMD64
 485       } else if (sig == SIGSEGV &&
 486                !MacroAssembler::needs_explicit_null_check((intptr_t)info->si_addr)) {
 487           // Determination of interpreter/vtable stub/compiled code null exception
 488           stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_NULL);
 489       }
 490     } else if (thread->thread_state() == _thread_in_vm &&
 491                sig == SIGBUS && /* info->si_code == BUS_OBJERR && */
 492                thread->doing_unsafe_access()) {
 493         address next_pc = Assembler::locate_next_instruction(pc);
 494         stub = SharedRuntime::handle_unsafe_access(thread, next_pc);
 495     }
 496 
 497     // jni_fast_Get<Primitive>Field can trap at certain pc's if a GC kicks in
 498     // and the heap gets shrunk before the field access.
 499     if ((sig == SIGSEGV) || (sig == SIGBUS)) {
 500       address addr = JNI_FastGetField::find_slowcase_pc(pc);
 501       if (addr != (address)-1) {
 502         stub = addr;
 503       }
 504     }
 505 
 506     // Check to see if we caught the safepoint code in the
 507     // process of write protecting the memory serialization page.
 508     // It write enables the page immediately after protecting it
 509     // so we can just return to retry the write.
 510     if ((sig == SIGSEGV) &&
 511         os::is_memory_serialize_page(thread, (address) info->si_addr)) {
 512       // Block current thread until the memory serialize page permission restored.
 513       os::block_on_serialize_page_trap();
 514       return true;
 515     }
 516   }
 517 
 518 #ifndef AMD64
 519   // Execution protection violation
 520   //
 521   // This should be kept as the last step in the triage.  We don't
 522   // have a dedicated trap number for a no-execute fault, so be
 523   // conservative and allow other handlers the first shot.
 524   //
 525   // Note: We don't test that info->si_code == SEGV_ACCERR here.
 526   // this si_code is so generic that it is almost meaningless; and
 527   // the si_code for this condition may change in the future.
 528   // Furthermore, a false-positive should be harmless.
 529   if (UnguardOnExecutionViolation > 0 &&
 530       (sig == SIGSEGV || sig == SIGBUS) &&
 531       uc->uc_mcontext.gregs[REG_TRAPNO] == trap_page_fault) {
 532     int page_size = os::vm_page_size();
 533     address addr = (address) info->si_addr;
 534     address pc = os::Linux::ucontext_get_pc(uc);
 535     // Make sure the pc and the faulting address are sane.
 536     //
 537     // If an instruction spans a page boundary, and the page containing
 538     // the beginning of the instruction is executable but the following
 539     // page is not, the pc and the faulting address might be slightly
 540     // different - we still want to unguard the 2nd page in this case.
 541     //
 542     // 15 bytes seems to be a (very) safe value for max instruction size.
 543     bool pc_is_near_addr =
 544       (pointer_delta((void*) addr, (void*) pc, sizeof(char)) < 15);
 545     bool instr_spans_page_boundary =
 546       (align_down((intptr_t) pc ^ (intptr_t) addr,
 547                        (intptr_t) page_size) > 0);
 548 
 549     if (pc == addr || (pc_is_near_addr && instr_spans_page_boundary)) {
 550       static volatile address last_addr =
 551         (address) os::non_memory_address_word();
 552 
 553       // In conservative mode, don't unguard unless the address is in the VM
 554       if (addr != last_addr &&
 555           (UnguardOnExecutionViolation > 1 || os::address_is_in_vm(addr))) {
 556 
 557         // Set memory to RWX and retry
 558         address page_start = align_down(addr, page_size);
 559         bool res = os::protect_memory((char*) page_start, page_size,
 560                                       os::MEM_PROT_RWX);
 561 
 562         log_debug(os)("Execution protection violation "
 563                       "at " INTPTR_FORMAT
 564                       ", unguarding " INTPTR_FORMAT ": %s, errno=%d", p2i(addr),
 565                       p2i(page_start), (res ? "success" : "failed"), errno);
 566         stub = pc;
 567 
 568         // Set last_addr so if we fault again at the same address, we don't end
 569         // up in an endless loop.
 570         //
 571         // There are two potential complications here.  Two threads trapping at
 572         // the same address at the same time could cause one of the threads to
 573         // think it already unguarded, and abort the VM.  Likely very rare.
 574         //
 575         // The other race involves two threads alternately trapping at
 576         // different addresses and failing to unguard the page, resulting in
 577         // an endless loop.  This condition is probably even more unlikely than
 578         // the first.
 579         //
 580         // Although both cases could be avoided by using locks or thread local
 581         // last_addr, these solutions are unnecessary complication: this
 582         // handler is a best-effort safety net, not a complete solution.  It is
 583         // disabled by default and should only be used as a workaround in case
 584         // we missed any no-execute-unsafe VM code.
 585 
 586         last_addr = addr;
 587       }
 588     }
 589   }
 590 #endif // !AMD64
 591 
 592   if (stub != NULL) {
 593     // save all thread context in case we need to restore it
 594     if (thread != NULL) thread->set_saved_exception_pc(pc);
 595 
 596     os::Linux::ucontext_set_pc(uc, stub);
 597     return true;
 598   }
 599 
 600   // signal-chaining
 601   if (os::Linux::chained_handler(sig, info, ucVoid)) {
 602      return true;
 603   }
 604 
 605   if (!abort_if_unrecognized) {
 606     // caller wants another chance, so give it to him
 607     return false;
 608   }
 609 
 610   if (pc == NULL && uc != NULL) {
 611     pc = os::Linux::ucontext_get_pc(uc);
 612   }
 613 
 614   // unmask current signal
 615   sigset_t newset;
 616   sigemptyset(&newset);
 617   sigaddset(&newset, sig);
 618   sigprocmask(SIG_UNBLOCK, &newset, NULL);
 619 
 620   VMError::report_and_die(t, sig, pc, info, ucVoid);
 621 
 622   ShouldNotReachHere();
 623   return true; // Mute compiler
 624 }
 625 
 626 void os::Linux::init_thread_fpu_state(void) {
 627 #ifndef AMD64
 628   // set fpu to 53 bit precision
 629   set_fpu_control_word(0x27f);
 630 #endif // !AMD64
 631 }
 632 
 633 int os::Linux::get_fpu_control_word(void) {
 634 #ifdef AMD64
 635   return 0;
 636 #else
 637   int fpu_control;
 638   _FPU_GETCW(fpu_control);
 639   return fpu_control & 0xffff;
 640 #endif // AMD64
 641 }
 642 
 643 void os::Linux::set_fpu_control_word(int fpu_control) {
 644 #ifndef AMD64
 645   _FPU_SETCW(fpu_control);
 646 #endif // !AMD64
 647 }
 648 
 649 // Check that the linux kernel version is 2.4 or higher since earlier
 650 // versions do not support SSE without patches.
 651 bool os::supports_sse() {
 652 #ifdef AMD64
 653   return true;
 654 #else
 655   struct utsname uts;
 656   if( uname(&uts) != 0 ) return false; // uname fails?
 657   char *minor_string;
 658   int major = strtol(uts.release,&minor_string,10);
 659   int minor = strtol(minor_string+1,NULL,10);
 660   bool result = (major > 2 || (major==2 && minor >= 4));
 661   log_info(os)("OS version is %d.%d, which %s support SSE/SSE2",
 662                major,minor, result ? "DOES" : "does NOT");
 663   return result;
 664 #endif // AMD64
 665 }
 666 
 667 bool os::is_allocatable(size_t bytes) {
 668 #ifdef AMD64
 669   // unused on amd64?
 670   return true;
 671 #else
 672 
 673   if (bytes < 2 * G) {
 674     return true;
 675   }
 676 
 677   char* addr = reserve_memory(bytes, NULL);
 678 
 679   if (addr != NULL) {
 680     release_memory(addr, bytes);
 681   }
 682 
 683   return addr != NULL;
 684 #endif // AMD64
 685 }
 686 
 687 ////////////////////////////////////////////////////////////////////////////////
 688 // thread stack
 689 
 690 // Minimum usable stack sizes required to get to user code. Space for
 691 // HotSpot guard pages is added later.
 692 size_t os::Posix::_compiler_thread_min_stack_allowed = 48 * K;
 693 size_t os::Posix::_java_thread_min_stack_allowed = 40 * K;
 694 #ifdef _LP64
 695 size_t os::Posix::_vm_internal_thread_min_stack_allowed = 64 * K;
 696 #else
 697 size_t os::Posix::_vm_internal_thread_min_stack_allowed = (48 DEBUG_ONLY(+ 4)) * K;
 698 #endif // _LP64
 699 
 700 // return default stack size for thr_type
 701 size_t os::Posix::default_stack_size(os::ThreadType thr_type) {
 702   // default stack size (compiler thread needs larger stack)
 703 #ifdef AMD64
 704   size_t s = (thr_type == os::compiler_thread ? 4 * M : 1 * M);
 705 #else
 706   size_t s = (thr_type == os::compiler_thread ? 2 * M : 512 * K);
 707 #endif // AMD64
 708   return s;
 709 }
 710 
 711 /////////////////////////////////////////////////////////////////////////////
 712 // helper functions for fatal error handler
 713 
 714 void os::print_context(outputStream *st, const void *context) {
 715   if (context == NULL) return;
 716 
 717   const ucontext_t *uc = (const ucontext_t*)context;
 718   st->print_cr("Registers:");
 719 #ifdef AMD64
 720   st->print(  "RAX=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RAX]);
 721   st->print(", RBX=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RBX]);
 722   st->print(", RCX=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RCX]);
 723   st->print(", RDX=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RDX]);
 724   st->cr();
 725   st->print(  "RSP=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RSP]);
 726   st->print(", RBP=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RBP]);
 727   st->print(", RSI=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RSI]);
 728   st->print(", RDI=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RDI]);
 729   st->cr();
 730   st->print(  "R8 =" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R8]);
 731   st->print(", R9 =" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R9]);
 732   st->print(", R10=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R10]);
 733   st->print(", R11=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R11]);
 734   st->cr();
 735   st->print(  "R12=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R12]);
 736   st->print(", R13=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R13]);
 737   st->print(", R14=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R14]);
 738   st->print(", R15=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R15]);
 739   st->cr();
 740   st->print(  "RIP=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RIP]);
 741   st->print(", EFLAGS=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_EFL]);
 742   st->print(", CSGSFS=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_CSGSFS]);
 743   st->print(", ERR=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_ERR]);
 744   st->cr();
 745   st->print("  TRAPNO=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_TRAPNO]);
 746 #else
 747   st->print(  "EAX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EAX]);
 748   st->print(", EBX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EBX]);
 749   st->print(", ECX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_ECX]);
 750   st->print(", EDX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EDX]);
 751   st->cr();
 752   st->print(  "ESP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_UESP]);
 753   st->print(", EBP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EBP]);
 754   st->print(", ESI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_ESI]);
 755   st->print(", EDI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EDI]);
 756   st->cr();
 757   st->print(  "EIP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EIP]);
 758   st->print(", EFLAGS=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EFL]);
 759   st->print(", CR2=" PTR64_FORMAT, (uint64_t)uc->uc_mcontext.cr2);
 760 #endif // AMD64
 761   st->cr();
 762   st->cr();
 763 
 764   intptr_t *sp = (intptr_t *)os::Linux::ucontext_get_sp(uc);
 765   st->print_cr("Top of Stack: (sp=" PTR_FORMAT ")", p2i(sp));
 766   print_hex_dump(st, (address)sp, (address)(sp + 8), sizeof(intptr_t));
 767   st->cr();
 768 
 769   // Note: it may be unsafe to inspect memory near pc. For example, pc may
 770   // point to garbage if entry point in an nmethod is corrupted. Leave
 771   // this at the end, and hope for the best.
 772   address pc = os::Linux::ucontext_get_pc(uc);
 773   st->print_cr("Instructions: (pc=" PTR_FORMAT ")", p2i(pc));
 774   print_hex_dump(st, pc - 32, pc + 32, sizeof(char));
 775 }
 776 
 777 void os::print_register_info(outputStream *st, const void *context) {
 778   if (context == NULL) return;
 779 
 780   const ucontext_t *uc = (const ucontext_t*)context;
 781 
 782   st->print_cr("Register to memory mapping:");
 783   st->cr();
 784 
 785   // this is horrendously verbose but the layout of the registers in the
 786   // context does not match how we defined our abstract Register set, so
 787   // we can't just iterate through the gregs area
 788 
 789   // this is only for the "general purpose" registers
 790 
 791 #ifdef AMD64
 792   st->print("RAX="); print_location(st, uc->uc_mcontext.gregs[REG_RAX]);
 793   st->print("RBX="); print_location(st, uc->uc_mcontext.gregs[REG_RBX]);
 794   st->print("RCX="); print_location(st, uc->uc_mcontext.gregs[REG_RCX]);
 795   st->print("RDX="); print_location(st, uc->uc_mcontext.gregs[REG_RDX]);
 796   st->print("RSP="); print_location(st, uc->uc_mcontext.gregs[REG_RSP]);
 797   st->print("RBP="); print_location(st, uc->uc_mcontext.gregs[REG_RBP]);
 798   st->print("RSI="); print_location(st, uc->uc_mcontext.gregs[REG_RSI]);
 799   st->print("RDI="); print_location(st, uc->uc_mcontext.gregs[REG_RDI]);
 800   st->print("R8 ="); print_location(st, uc->uc_mcontext.gregs[REG_R8]);
 801   st->print("R9 ="); print_location(st, uc->uc_mcontext.gregs[REG_R9]);
 802   st->print("R10="); print_location(st, uc->uc_mcontext.gregs[REG_R10]);
 803   st->print("R11="); print_location(st, uc->uc_mcontext.gregs[REG_R11]);
 804   st->print("R12="); print_location(st, uc->uc_mcontext.gregs[REG_R12]);
 805   st->print("R13="); print_location(st, uc->uc_mcontext.gregs[REG_R13]);
 806   st->print("R14="); print_location(st, uc->uc_mcontext.gregs[REG_R14]);
 807   st->print("R15="); print_location(st, uc->uc_mcontext.gregs[REG_R15]);
 808 #else
 809   st->print("EAX="); print_location(st, uc->uc_mcontext.gregs[REG_EAX]);
 810   st->print("EBX="); print_location(st, uc->uc_mcontext.gregs[REG_EBX]);
 811   st->print("ECX="); print_location(st, uc->uc_mcontext.gregs[REG_ECX]);
 812   st->print("EDX="); print_location(st, uc->uc_mcontext.gregs[REG_EDX]);
 813   st->print("ESP="); print_location(st, uc->uc_mcontext.gregs[REG_ESP]);
 814   st->print("EBP="); print_location(st, uc->uc_mcontext.gregs[REG_EBP]);
 815   st->print("ESI="); print_location(st, uc->uc_mcontext.gregs[REG_ESI]);
 816   st->print("EDI="); print_location(st, uc->uc_mcontext.gregs[REG_EDI]);
 817 #endif // AMD64
 818 
 819   st->cr();
 820 }
 821 
 822 void os::setup_fpu() {
 823 #ifndef AMD64
 824   address fpu_cntrl = StubRoutines::addr_fpu_cntrl_wrd_std();
 825   __asm__ volatile (  "fldcw (%0)" :
 826                       : "r" (fpu_cntrl) : "memory");
 827 #endif // !AMD64
 828 }
 829 
 830 #ifndef PRODUCT
 831 void os::verify_stack_alignment() {
 832 #ifdef AMD64
 833   assert(((intptr_t)os::current_stack_pointer() & (StackAlignmentInBytes-1)) == 0, "incorrect stack alignment");
 834 #endif
 835 }
 836 #endif
 837 
 838 
 839 /*
 840  * IA32 only: execute code at a high address in case buggy NX emulation is present. I.e. avoid CS limit
 841  * updates (JDK-8023956).
 842  */
 843 void os::workaround_expand_exec_shield_cs_limit() {
 844 #if defined(IA32)
 845   size_t page_size = os::vm_page_size();
 846 
 847   /*
 848    * JDK-8197429
 849    *
 850    * Expand the stack mapping to the end of the initial stack before
 851    * attempting to install the codebuf.  This is needed because newer
 852    * Linux kernels impose a distance of a megabyte between stack
 853    * memory and other memory regions.  If we try to install the
 854    * codebuf before expanding the stack the installation will appear
 855    * to succeed but we'll get a segfault later if we expand the stack
 856    * in Java code.
 857    *
 858    */
 859   if (os::is_primordial_thread()) {
 860     address limit = Linux::initial_thread_stack_bottom();
 861     if (! DisablePrimordialThreadGuardPages) {
 862       limit += JavaThread::stack_red_zone_size() +
 863         JavaThread::stack_yellow_zone_size();
 864     }
 865     os::Linux::expand_stack_to(limit);
 866   }
 867 
 868   /*
 869    * Take the highest VA the OS will give us and exec
 870    *
 871    * Although using -(pagesz) as mmap hint works on newer kernel as you would
 872    * think, older variants affected by this work-around don't (search forward only).
 873    *
 874    * On the affected distributions, we understand the memory layout to be:
 875    *
 876    *   TASK_LIMIT= 3G, main stack base close to TASK_LIMT.
 877    *
 878    * A few pages south main stack will do it.
 879    *
 880    * If we are embedded in an app other than launcher (initial != main stack),
 881    * we don't have much control or understanding of the address space, just let it slide.
 882    */
 883   char* hint = (char*)(Linux::initial_thread_stack_bottom() -
 884                        (JavaThread::stack_guard_zone_size() + page_size));
 885   char* codebuf = os::attempt_reserve_memory_at(page_size, hint);
 886 
 887   if (codebuf == NULL) {
 888     // JDK-8197429: There may be a stack gap of one megabyte between
 889     // the limit of the stack and the nearest memory region: this is a
 890     // Linux kernel workaround for CVE-2017-1000364.  If we failed to
 891     // map our codebuf, try again at an address one megabyte lower.
 892     hint -= 1 * M;
 893     codebuf = os::attempt_reserve_memory_at(page_size, hint);
 894   }
 895 
 896   if ((codebuf == NULL) || (!os::commit_memory(codebuf, page_size, true))) {
 897     return; // No matter, we tried, best effort.
 898   }
 899 
 900   MemTracker::record_virtual_memory_type((address)codebuf, mtInternal);
 901 
 902   log_info(os)("[CS limit NX emulation work-around, exec code at: %p]", codebuf);
 903 
 904   // Some code to exec: the 'ret' instruction
 905   codebuf[0] = 0xC3;
 906 
 907   // Call the code in the codebuf
 908   __asm__ volatile("call *%0" : : "r"(codebuf));
 909 
 910   // keep the page mapped so CS limit isn't reduced.
 911 #endif
 912 }
 913 
 914 int os::extra_bang_size_in_bytes() {
 915   // JDK-8050147 requires the full cache line bang for x86.
 916   return VM_Version::L1_line_size();
 917 }