1 /*
   2  * Copyright (c) 1999, 2016, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 // no precompiled headers
  26 #include "asm/macroAssembler.hpp"
  27 #include "classfile/classLoader.hpp"
  28 #include "classfile/systemDictionary.hpp"
  29 #include "classfile/vmSymbols.hpp"
  30 #include "code/codeCache.hpp"
  31 #include "code/icBuffer.hpp"
  32 #include "code/vtableStubs.hpp"
  33 #include "interpreter/interpreter.hpp"
  34 #include "jvm_linux.h"
  35 #include "memory/allocation.inline.hpp"
  36 #include "os_share_linux.hpp"
  37 #include "prims/jniFastGetField.hpp"
  38 #include "prims/jvm.h"
  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.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/events.hpp"
  54 #include "utilities/vmError.hpp"
  55 
  56 // put OS-includes here
  57 # include <sys/types.h>
  58 # include <sys/mman.h>
  59 # include <pthread.h>
  60 # include <signal.h>
  61 # include <errno.h>
  62 # include <dlfcn.h>
  63 # include <stdlib.h>
  64 # include <stdio.h>
  65 # include <unistd.h>
  66 # include <sys/resource.h>
  67 # include <pthread.h>
  68 # include <sys/stat.h>
  69 # include <sys/time.h>
  70 # include <sys/utsname.h>
  71 # include <sys/socket.h>
  72 # include <sys/wait.h>
  73 # include <pwd.h>
  74 # include <poll.h>
  75 # include <ucontext.h>
  76 #ifndef AMD64
  77 # include <fpu_control.h>
  78 #endif
  79 
  80 #ifdef AMD64
  81 #define REG_SP REG_RSP
  82 #define REG_PC REG_RIP
  83 #define REG_FP REG_RBP
  84 #define SPELL_REG_SP "rsp"
  85 #define SPELL_REG_FP "rbp"
  86 #else
  87 #define REG_SP REG_UESP
  88 #define REG_PC REG_EIP
  89 #define REG_FP REG_EBP
  90 #define SPELL_REG_SP "esp"
  91 #define SPELL_REG_FP "ebp"
  92 #endif // AMD64
  93 
  94 address os::current_stack_pointer() {
  95 #ifdef SPARC_WORKS
  96   register void *esp;
  97   __asm__("mov %%"SPELL_REG_SP", %0":"=r"(esp));
  98   return (address) ((char*)esp + sizeof(long)*2);
  99 #elif defined(__clang__)
 100   intptr_t* esp;
 101   __asm__ __volatile__ ("mov %%"SPELL_REG_SP", %0":"=r"(esp):);
 102   return (address) esp;
 103 #else
 104   register void *esp __asm__ (SPELL_REG_SP);
 105   return (address) esp;
 106 #endif
 107 }
 108 
 109 char* os::non_memory_address_word() {
 110   // Must never look like an address returned by reserve_memory,
 111   // even in its subfields (as defined by the CPU immediate fields,
 112   // if the CPU splits constants across multiple instructions).
 113 
 114   return (char*) -1;
 115 }
 116 
 117 void os::initialize_thread(Thread* thr) {
 118 // Nothing to do.
 119 }
 120 
 121 address os::Linux::ucontext_get_pc(const ucontext_t * uc) {
 122   return (address)uc->uc_mcontext.gregs[REG_PC];
 123 }
 124 
 125 void os::Linux::ucontext_set_pc(ucontext_t * uc, address pc) {
 126   uc->uc_mcontext.gregs[REG_PC] = (intptr_t)pc;
 127 }
 128 
 129 intptr_t* os::Linux::ucontext_get_sp(const ucontext_t * uc) {
 130   return (intptr_t*)uc->uc_mcontext.gregs[REG_SP];
 131 }
 132 
 133 intptr_t* os::Linux::ucontext_get_fp(const ucontext_t * uc) {
 134   return (intptr_t*)uc->uc_mcontext.gregs[REG_FP];
 135 }
 136 
 137 // For Forte Analyzer AsyncGetCallTrace profiling support - thread
 138 // is currently interrupted by SIGPROF.
 139 // os::Solaris::fetch_frame_from_ucontext() tries to skip nested signal
 140 // frames. Currently we don't do that on Linux, so it's the same as
 141 // os::fetch_frame_from_context().
 142 // This method is also used for stack overflow signal handling.
 143 ExtendedPC os::Linux::fetch_frame_from_ucontext(Thread* thread,
 144   const ucontext_t* uc, intptr_t** ret_sp, intptr_t** ret_fp) {
 145 
 146   assert(thread != NULL, "just checking");
 147   assert(ret_sp != NULL, "just checking");
 148   assert(ret_fp != NULL, "just checking");
 149 
 150   return os::fetch_frame_from_context(uc, ret_sp, ret_fp);
 151 }
 152 
 153 ExtendedPC os::fetch_frame_from_context(const void* ucVoid,
 154                     intptr_t** ret_sp, intptr_t** ret_fp) {
 155 
 156   ExtendedPC  epc;
 157   const ucontext_t* uc = (const ucontext_t*)ucVoid;
 158 
 159   if (uc != NULL) {
 160     epc = ExtendedPC(os::Linux::ucontext_get_pc(uc));
 161     if (ret_sp) *ret_sp = os::Linux::ucontext_get_sp(uc);
 162     if (ret_fp) *ret_fp = os::Linux::ucontext_get_fp(uc);
 163   } else {
 164     // construct empty ExtendedPC for return value checking
 165     epc = ExtendedPC(NULL);
 166     if (ret_sp) *ret_sp = (intptr_t *)NULL;
 167     if (ret_fp) *ret_fp = (intptr_t *)NULL;
 168   }
 169 
 170   return epc;
 171 }
 172 
 173 frame os::fetch_frame_from_context(const void* ucVoid) {
 174   intptr_t* sp;
 175   intptr_t* fp;
 176   ExtendedPC epc = fetch_frame_from_context(ucVoid, &sp, &fp);
 177   return frame(sp, fp, epc.pc());
 178 }
 179 
 180 frame os::fetch_frame_from_ucontext(Thread* thread, void* ucVoid) {
 181   intptr_t* sp;
 182   intptr_t* fp;
 183   ExtendedPC epc = os::Linux::fetch_frame_from_ucontext(thread, (ucontext_t*)ucVoid, &sp, &fp);
 184   return frame(sp, fp, epc.pc());
 185 }
 186 
 187 bool os::Linux::get_frame_at_stack_banging_point(JavaThread* thread, ucontext_t* uc, frame* fr) {
 188   address pc = (address) os::Linux::ucontext_get_pc(uc);
 189   if (Interpreter::contains(pc)) {
 190     // interpreter performs stack banging after the fixed frame header has
 191     // been generated while the compilers perform it before. To maintain
 192     // semantic consistency between interpreted and compiled frames, the
 193     // method returns the Java sender of the current frame.
 194     *fr = os::fetch_frame_from_ucontext(thread, uc);
 195     if (!fr->is_first_java_frame()) {
 196       // get_frame_at_stack_banging_point() is only called when we
 197       // have well defined stacks so java_sender() calls do not need
 198       // to assert safe_for_sender() first.
 199       *fr = fr->java_sender();
 200     }
 201   } else {
 202     // more complex code with compiled code
 203     assert(!Interpreter::contains(pc), "Interpreted methods should have been handled above");
 204     CodeBlob* cb = CodeCache::find_blob(pc);
 205     if (cb == NULL || !cb->is_nmethod() || cb->is_frame_complete_at(pc)) {
 206       // Not sure where the pc points to, fallback to default
 207       // stack overflow handling
 208       return false;
 209     } else {
 210       // in compiled code, the stack banging is performed just after the return pc
 211       // has been pushed on the stack
 212       intptr_t* fp = os::Linux::ucontext_get_fp(uc);
 213       intptr_t* sp = os::Linux::ucontext_get_sp(uc);
 214       *fr = frame(sp + 1, fp, (address)*sp);
 215       if (!fr->is_java_frame()) {
 216         assert(!fr->is_first_frame(), "Safety check");
 217         // See java_sender() comment above.
 218         *fr = fr->java_sender();
 219       }
 220     }
 221   }
 222   assert(fr->is_java_frame(), "Safety check");
 223   return true;
 224 }
 225 
 226 // By default, gcc always save frame pointer (%ebp/%rbp) on stack. It may get
 227 // turned off by -fomit-frame-pointer,
 228 frame os::get_sender_for_C_frame(frame* fr) {
 229   return frame(fr->sender_sp(), fr->link(), fr->sender_pc());
 230 }
 231 
 232 intptr_t* _get_previous_fp() {
 233 #ifdef SPARC_WORKS
 234   register intptr_t **ebp;
 235   __asm__("mov %%"SPELL_REG_FP", %0":"=r"(ebp));
 236 #elif defined(__clang__)
 237   intptr_t **ebp;
 238   __asm__ __volatile__ ("mov %%"SPELL_REG_FP", %0":"=r"(ebp):);
 239 #else
 240   register intptr_t **ebp __asm__ (SPELL_REG_FP);
 241 #endif
 242   // ebp is for this frame (_get_previous_fp). We want the ebp for the
 243   // caller of os::current_frame*(), so go up two frames. However, for
 244   // optimized builds, _get_previous_fp() will be inlined, so only go
 245   // up 1 frame in that case.
 246 #ifdef _NMT_NOINLINE_
 247   return **(intptr_t***)ebp;
 248 #else
 249   return *ebp;
 250 #endif
 251 }
 252 
 253 
 254 frame os::current_frame() {
 255   intptr_t* fp = _get_previous_fp();
 256   frame myframe((intptr_t*)os::current_stack_pointer(),
 257                 (intptr_t*)fp,
 258                 CAST_FROM_FN_PTR(address, os::current_frame));
 259   if (os::is_first_C_frame(&myframe)) {
 260     // stack is not walkable
 261     return frame();
 262   } else {
 263     return os::get_sender_for_C_frame(&myframe);
 264   }
 265 }
 266 
 267 // Utility functions
 268 
 269 // From IA32 System Programming Guide
 270 enum {
 271   trap_page_fault = 0xE
 272 };
 273 
 274 extern "C" JNIEXPORT int
 275 JVM_handle_linux_signal(int sig,
 276                         siginfo_t* info,
 277                         void* ucVoid,
 278                         int abort_if_unrecognized) {
 279   ucontext_t* uc = (ucontext_t*) ucVoid;
 280 
 281   Thread* t = Thread::current_or_null_safe();
 282 
 283   // Must do this before SignalHandlerMark, if crash protection installed we will longjmp away
 284   // (no destructors can be run)
 285   os::WatcherThreadCrashProtection::check_crash_protection(sig, t);
 286 
 287   SignalHandlerMark shm(t);
 288 
 289   // Note: it's not uncommon that JNI code uses signal/sigset to install
 290   // then restore certain signal handler (e.g. to temporarily block SIGPIPE,
 291   // or have a SIGILL handler when detecting CPU type). When that happens,
 292   // JVM_handle_linux_signal() might be invoked with junk info/ucVoid. To
 293   // avoid unnecessary crash when libjsig is not preloaded, try handle signals
 294   // that do not require siginfo/ucontext first.
 295 
 296   if (sig == SIGPIPE || sig == SIGXFSZ) {
 297     // allow chained handler to go first
 298     if (os::Linux::chained_handler(sig, info, ucVoid)) {
 299       return true;
 300     } else {
 301       // Ignoring SIGPIPE/SIGXFSZ - see bugs 4229104 or 6499219
 302       return true;
 303     }
 304   }
 305 
 306   JavaThread* thread = NULL;
 307   VMThread* vmthread = NULL;
 308   if (os::Linux::signal_handlers_are_installed) {
 309     if (t != NULL ){
 310       if(t->is_Java_thread()) {
 311         thread = (JavaThread*)t;
 312       }
 313       else if(t->is_VM_thread()){
 314         vmthread = (VMThread *)t;
 315       }
 316     }
 317   }
 318 /*
 319   NOTE: does not seem to work on linux.
 320   if (info == NULL || info->si_code <= 0 || info->si_code == SI_NOINFO) {
 321     // can't decode this kind of signal
 322     info = NULL;
 323   } else {
 324     assert(sig == info->si_signo, "bad siginfo");
 325   }
 326 */
 327   // decide if this trap can be handled by a stub
 328   address stub = NULL;
 329 
 330   address pc          = NULL;
 331 
 332   //%note os_trap_1
 333   if (info != NULL && uc != NULL && thread != NULL) {
 334     pc = (address) os::Linux::ucontext_get_pc(uc);
 335 
 336     if (StubRoutines::is_safefetch_fault(pc)) {
 337       os::Linux::ucontext_set_pc(uc, StubRoutines::continuation_for_safefetch_fault(pc));
 338       return 1;
 339     }
 340 
 341 #ifndef AMD64
 342     // Halt if SI_KERNEL before more crashes get misdiagnosed as Java bugs
 343     // This can happen in any running code (currently more frequently in
 344     // interpreter code but has been seen in compiled code)
 345     if (sig == SIGSEGV && info->si_addr == 0 && info->si_code == SI_KERNEL) {
 346       fatal("An irrecoverable SI_KERNEL SIGSEGV has occurred due "
 347             "to unstable signal handling in this distribution.");
 348     }
 349 #endif // AMD64
 350 
 351     // Handle ALL stack overflow variations here
 352     if (sig == SIGSEGV) {
 353       address addr = (address) info->si_addr;
 354 
 355       // check if fault address is within thread stack
 356       if (thread->on_local_stack(addr)) {
 357         // stack overflow
 358         if (thread->in_stack_yellow_reserved_zone(addr)) {
 359           if (thread->thread_state() == _thread_in_Java) {
 360             if (thread->in_stack_reserved_zone(addr)) {
 361               frame fr;
 362               if (os::Linux::get_frame_at_stack_banging_point(thread, uc, &fr)) {
 363                 assert(fr.is_java_frame(), "Must be a Java frame");
 364                 frame activation =
 365                   SharedRuntime::look_for_reserved_stack_annotated_method(thread, fr);
 366                 if (activation.sp() != NULL) {
 367                   thread->disable_stack_reserved_zone();
 368                   if (activation.is_interpreted_frame()) {
 369                     thread->set_reserved_stack_activation((address)(
 370                       activation.fp() + frame::interpreter_frame_initial_sp_offset));
 371                   } else {
 372                     thread->set_reserved_stack_activation((address)activation.unextended_sp());
 373                   }
 374                   return 1;
 375                 }
 376               }
 377             }
 378             // Throw a stack overflow exception.  Guard pages will be reenabled
 379             // while unwinding the stack.
 380             thread->disable_stack_yellow_reserved_zone();
 381             stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::STACK_OVERFLOW);
 382           } else {
 383             // Thread was in the vm or native code.  Return and try to finish.
 384             thread->disable_stack_yellow_reserved_zone();
 385             return 1;
 386           }
 387         } else if (thread->in_stack_red_zone(addr)) {
 388           // Fatal red zone violation.  Disable the guard pages and fall through
 389           // to handle_unexpected_exception way down below.
 390           thread->disable_stack_red_zone();
 391           tty->print_raw_cr("An irrecoverable stack overflow has occurred.");
 392 
 393           // This is a likely cause, but hard to verify. Let's just print
 394           // it as a hint.
 395           tty->print_raw_cr("Please check if any of your loaded .so files has "
 396                             "enabled executable stack (see man page execstack(8))");
 397         } else {
 398           // Accessing stack address below sp may cause SEGV if current
 399           // thread has MAP_GROWSDOWN stack. This should only happen when
 400           // current thread was created by user code with MAP_GROWSDOWN flag
 401           // and then attached to VM. See notes in os_linux.cpp.
 402           if (thread->osthread()->expanding_stack() == 0) {
 403              thread->osthread()->set_expanding_stack();
 404              if (os::Linux::manually_expand_stack(thread, addr)) {
 405                thread->osthread()->clear_expanding_stack();
 406                return 1;
 407              }
 408              thread->osthread()->clear_expanding_stack();
 409           } else {
 410              fatal("recursive segv. expanding stack.");
 411           }
 412         }
 413       }
 414     }
 415 
 416     if ((sig == SIGSEGV) && VM_Version::is_cpuinfo_segv_addr(pc)) {
 417       // Verify that OS save/restore AVX registers.
 418       stub = VM_Version::cpuinfo_cont_addr();
 419     }
 420 
 421     if (thread->thread_state() == _thread_in_Java) {
 422       // Java thread running in Java code => find exception handler if any
 423       // a fault inside compiled code, the interpreter, or a stub
 424 
 425       if (sig == SIGSEGV && os::is_poll_address((address)info->si_addr)) {
 426         stub = SharedRuntime::get_poll_stub(pc);
 427       } else if (sig == SIGBUS /* && info->si_code == BUS_OBJERR */) {
 428         // BugId 4454115: A read from a MappedByteBuffer can fault
 429         // here if the underlying file has been truncated.
 430         // Do not crash the VM in such a case.
 431         CodeBlob* cb = CodeCache::find_blob_unsafe(pc);
 432         CompiledMethod* nm = (cb != NULL) ? cb->as_compiled_method_or_null() : NULL;
 433         if (nm != NULL && nm->has_unsafe_access()) {
 434           address next_pc = Assembler::locate_next_instruction(pc);
 435           stub = SharedRuntime::handle_unsafe_access(thread, next_pc);
 436         }
 437       }
 438       else
 439 
 440 #ifdef AMD64
 441       if (sig == SIGFPE  &&
 442           (info->si_code == FPE_INTDIV || info->si_code == FPE_FLTDIV)) {
 443         stub =
 444           SharedRuntime::
 445           continuation_for_implicit_exception(thread,
 446                                               pc,
 447                                               SharedRuntime::
 448                                               IMPLICIT_DIVIDE_BY_ZERO);
 449 #else
 450       if (sig == SIGFPE /* && info->si_code == FPE_INTDIV */) {
 451         // HACK: si_code does not work on linux 2.2.12-20!!!
 452         int op = pc[0];
 453         if (op == 0xDB) {
 454           // FIST
 455           // TODO: The encoding of D2I in i486.ad can cause an exception
 456           // prior to the fist instruction if there was an invalid operation
 457           // pending. We want to dismiss that exception. From the win_32
 458           // side it also seems that if it really was the fist causing
 459           // the exception that we do the d2i by hand with different
 460           // rounding. Seems kind of weird.
 461           // NOTE: that we take the exception at the NEXT floating point instruction.
 462           assert(pc[0] == 0xDB, "not a FIST opcode");
 463           assert(pc[1] == 0x14, "not a FIST opcode");
 464           assert(pc[2] == 0x24, "not a FIST opcode");
 465           return true;
 466         } else if (op == 0xF7) {
 467           // IDIV
 468           stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_DIVIDE_BY_ZERO);
 469         } else {
 470           // TODO: handle more cases if we are using other x86 instructions
 471           //   that can generate SIGFPE signal on linux.
 472           tty->print_cr("unknown opcode 0x%X with SIGFPE.", op);
 473           fatal("please update this code.");
 474         }
 475 #endif // AMD64
 476       } else if (sig == SIGSEGV &&
 477                !MacroAssembler::needs_explicit_null_check((intptr_t)info->si_addr)) {
 478           // Determination of interpreter/vtable stub/compiled code null exception
 479           stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_NULL);
 480       }
 481     } else if (thread->thread_state() == _thread_in_vm &&
 482                sig == SIGBUS && /* info->si_code == BUS_OBJERR && */
 483                thread->doing_unsafe_access()) {
 484         address next_pc = Assembler::locate_next_instruction(pc);
 485         stub = SharedRuntime::handle_unsafe_access(thread, next_pc);
 486     }
 487 
 488     // jni_fast_Get<Primitive>Field can trap at certain pc's if a GC kicks in
 489     // and the heap gets shrunk before the field access.
 490     if ((sig == SIGSEGV) || (sig == SIGBUS)) {
 491       address addr = JNI_FastGetField::find_slowcase_pc(pc);
 492       if (addr != (address)-1) {
 493         stub = addr;
 494       }
 495     }
 496 
 497     // Check to see if we caught the safepoint code in the
 498     // process of write protecting the memory serialization page.
 499     // It write enables the page immediately after protecting it
 500     // so we can just return to retry the write.
 501     if ((sig == SIGSEGV) &&
 502         os::is_memory_serialize_page(thread, (address) info->si_addr)) {
 503       // Block current thread until the memory serialize page permission restored.
 504       os::block_on_serialize_page_trap();
 505       return true;
 506     }
 507   }
 508 
 509 #ifndef AMD64
 510   // Execution protection violation
 511   //
 512   // This should be kept as the last step in the triage.  We don't
 513   // have a dedicated trap number for a no-execute fault, so be
 514   // conservative and allow other handlers the first shot.
 515   //
 516   // Note: We don't test that info->si_code == SEGV_ACCERR here.
 517   // this si_code is so generic that it is almost meaningless; and
 518   // the si_code for this condition may change in the future.
 519   // Furthermore, a false-positive should be harmless.
 520   if (UnguardOnExecutionViolation > 0 &&
 521       (sig == SIGSEGV || sig == SIGBUS) &&
 522       uc->uc_mcontext.gregs[REG_TRAPNO] == trap_page_fault) {
 523     int page_size = os::vm_page_size();
 524     address addr = (address) info->si_addr;
 525     address pc = os::Linux::ucontext_get_pc(uc);
 526     // Make sure the pc and the faulting address are sane.
 527     //
 528     // If an instruction spans a page boundary, and the page containing
 529     // the beginning of the instruction is executable but the following
 530     // page is not, the pc and the faulting address might be slightly
 531     // different - we still want to unguard the 2nd page in this case.
 532     //
 533     // 15 bytes seems to be a (very) safe value for max instruction size.
 534     bool pc_is_near_addr =
 535       (pointer_delta((void*) addr, (void*) pc, sizeof(char)) < 15);
 536     bool instr_spans_page_boundary =
 537       (align_size_down((intptr_t) pc ^ (intptr_t) addr,
 538                        (intptr_t) page_size) > 0);
 539 
 540     if (pc == addr || (pc_is_near_addr && instr_spans_page_boundary)) {
 541       static volatile address last_addr =
 542         (address) os::non_memory_address_word();
 543 
 544       // In conservative mode, don't unguard unless the address is in the VM
 545       if (addr != last_addr &&
 546           (UnguardOnExecutionViolation > 1 || os::address_is_in_vm(addr))) {
 547 
 548         // Set memory to RWX and retry
 549         address page_start = align_ptr_down(addr, page_size);
 550         bool res = os::protect_memory((char*) page_start, page_size,
 551                                       os::MEM_PROT_RWX);
 552 
 553         log_debug(os)("Execution protection violation "
 554                       "at " INTPTR_FORMAT
 555                       ", unguarding " INTPTR_FORMAT ": %s, errno=%d", p2i(addr),
 556                       p2i(page_start), (res ? "success" : "failed"), errno);
 557         stub = pc;
 558 
 559         // Set last_addr so if we fault again at the same address, we don't end
 560         // up in an endless loop.
 561         //
 562         // There are two potential complications here.  Two threads trapping at
 563         // the same address at the same time could cause one of the threads to
 564         // think it already unguarded, and abort the VM.  Likely very rare.
 565         //
 566         // The other race involves two threads alternately trapping at
 567         // different addresses and failing to unguard the page, resulting in
 568         // an endless loop.  This condition is probably even more unlikely than
 569         // the first.
 570         //
 571         // Although both cases could be avoided by using locks or thread local
 572         // last_addr, these solutions are unnecessary complication: this
 573         // handler is a best-effort safety net, not a complete solution.  It is
 574         // disabled by default and should only be used as a workaround in case
 575         // we missed any no-execute-unsafe VM code.
 576 
 577         last_addr = addr;
 578       }
 579     }
 580   }
 581 #endif // !AMD64
 582 
 583   if (stub != NULL) {
 584     // save all thread context in case we need to restore it
 585     if (thread != NULL) thread->set_saved_exception_pc(pc);
 586 
 587     os::Linux::ucontext_set_pc(uc, stub);
 588     return true;
 589   }
 590 
 591   // signal-chaining
 592   if (os::Linux::chained_handler(sig, info, ucVoid)) {
 593      return true;
 594   }
 595 
 596   if (!abort_if_unrecognized) {
 597     // caller wants another chance, so give it to him
 598     return false;
 599   }
 600 
 601   if (pc == NULL && uc != NULL) {
 602     pc = os::Linux::ucontext_get_pc(uc);
 603   }
 604 
 605   // unmask current signal
 606   sigset_t newset;
 607   sigemptyset(&newset);
 608   sigaddset(&newset, sig);
 609   sigprocmask(SIG_UNBLOCK, &newset, NULL);
 610 
 611   VMError::report_and_die(t, sig, pc, info, ucVoid);
 612 
 613   ShouldNotReachHere();
 614   return true; // Mute compiler
 615 }
 616 
 617 void os::Linux::init_thread_fpu_state(void) {
 618 #ifndef AMD64
 619   // set fpu to 53 bit precision
 620   set_fpu_control_word(0x27f);
 621 #endif // !AMD64
 622 }
 623 
 624 int os::Linux::get_fpu_control_word(void) {
 625 #ifdef AMD64
 626   return 0;
 627 #else
 628   int fpu_control;
 629   _FPU_GETCW(fpu_control);
 630   return fpu_control & 0xffff;
 631 #endif // AMD64
 632 }
 633 
 634 void os::Linux::set_fpu_control_word(int fpu_control) {
 635 #ifndef AMD64
 636   _FPU_SETCW(fpu_control);
 637 #endif // !AMD64
 638 }
 639 
 640 // Check that the linux kernel version is 2.4 or higher since earlier
 641 // versions do not support SSE without patches.
 642 bool os::supports_sse() {
 643 #ifdef AMD64
 644   return true;
 645 #else
 646   struct utsname uts;
 647   if( uname(&uts) != 0 ) return false; // uname fails?
 648   char *minor_string;
 649   int major = strtol(uts.release,&minor_string,10);
 650   int minor = strtol(minor_string+1,NULL,10);
 651   bool result = (major > 2 || (major==2 && minor >= 4));
 652   log_info(os)("OS version is %d.%d, which %s support SSE/SSE2",
 653                major,minor, result ? "DOES" : "does NOT");
 654   return result;
 655 #endif // AMD64
 656 }
 657 
 658 bool os::is_allocatable(size_t bytes) {
 659 #ifdef AMD64
 660   // unused on amd64?
 661   return true;
 662 #else
 663 
 664   if (bytes < 2 * G) {
 665     return true;
 666   }
 667 
 668   char* addr = reserve_memory(bytes, NULL);
 669 
 670   if (addr != NULL) {
 671     release_memory(addr, bytes);
 672   }
 673 
 674   return addr != NULL;
 675 #endif // AMD64
 676 }
 677 
 678 ////////////////////////////////////////////////////////////////////////////////
 679 // thread stack
 680 
 681 // Minimum usable stack sizes required to get to user code. Space for
 682 // HotSpot guard pages is added later.
 683 size_t os::Posix::_compiler_thread_min_stack_allowed = 48 * K;
 684 size_t os::Posix::_java_thread_min_stack_allowed = 40 * K;
 685 #ifdef _LP64
 686 size_t os::Posix::_vm_internal_thread_min_stack_allowed = 64 * K;
 687 #else
 688 size_t os::Posix::_vm_internal_thread_min_stack_allowed = (48 DEBUG_ONLY(+ 4)) * K;
 689 #endif // _LP64
 690 
 691 // return default stack size for thr_type
 692 size_t os::Posix::default_stack_size(os::ThreadType thr_type) {
 693   // default stack size (compiler thread needs larger stack)
 694 #ifdef AMD64
 695   size_t s = (thr_type == os::compiler_thread ? 4 * M : 1 * M);
 696 #else
 697   size_t s = (thr_type == os::compiler_thread ? 2 * M : 512 * K);
 698 #endif // AMD64
 699   return s;
 700 }
 701 
 702 /////////////////////////////////////////////////////////////////////////////
 703 // helper functions for fatal error handler
 704 
 705 void os::print_context(outputStream *st, const void *context) {
 706   if (context == NULL) return;
 707 
 708   const ucontext_t *uc = (const ucontext_t*)context;
 709   st->print_cr("Registers:");
 710 #ifdef AMD64
 711   st->print(  "RAX=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RAX]);
 712   st->print(", RBX=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RBX]);
 713   st->print(", RCX=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RCX]);
 714   st->print(", RDX=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RDX]);
 715   st->cr();
 716   st->print(  "RSP=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RSP]);
 717   st->print(", RBP=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RBP]);
 718   st->print(", RSI=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RSI]);
 719   st->print(", RDI=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RDI]);
 720   st->cr();
 721   st->print(  "R8 =" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R8]);
 722   st->print(", R9 =" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R9]);
 723   st->print(", R10=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R10]);
 724   st->print(", R11=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R11]);
 725   st->cr();
 726   st->print(  "R12=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R12]);
 727   st->print(", R13=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R13]);
 728   st->print(", R14=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R14]);
 729   st->print(", R15=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R15]);
 730   st->cr();
 731   st->print(  "RIP=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RIP]);
 732   st->print(", EFLAGS=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_EFL]);
 733   st->print(", CSGSFS=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_CSGSFS]);
 734   st->print(", ERR=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_ERR]);
 735   st->cr();
 736   st->print("  TRAPNO=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_TRAPNO]);
 737 #else
 738   st->print(  "EAX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EAX]);
 739   st->print(", EBX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EBX]);
 740   st->print(", ECX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_ECX]);
 741   st->print(", EDX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EDX]);
 742   st->cr();
 743   st->print(  "ESP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_UESP]);
 744   st->print(", EBP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EBP]);
 745   st->print(", ESI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_ESI]);
 746   st->print(", EDI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EDI]);
 747   st->cr();
 748   st->print(  "EIP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EIP]);
 749   st->print(", EFLAGS=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EFL]);
 750   st->print(", CR2=" PTR64_FORMAT, (uint64_t)uc->uc_mcontext.cr2);
 751 #endif // AMD64
 752   st->cr();
 753   st->cr();
 754 
 755   intptr_t *sp = (intptr_t *)os::Linux::ucontext_get_sp(uc);
 756   st->print_cr("Top of Stack: (sp=" PTR_FORMAT ")", p2i(sp));
 757   print_hex_dump(st, (address)sp, (address)(sp + 8), sizeof(intptr_t));
 758   st->cr();
 759 
 760   // Note: it may be unsafe to inspect memory near pc. For example, pc may
 761   // point to garbage if entry point in an nmethod is corrupted. Leave
 762   // this at the end, and hope for the best.
 763   address pc = os::Linux::ucontext_get_pc(uc);
 764   st->print_cr("Instructions: (pc=" PTR_FORMAT ")", p2i(pc));
 765   print_hex_dump(st, pc - 32, pc + 32, sizeof(char));
 766 }
 767 
 768 void os::print_register_info(outputStream *st, const void *context) {
 769   if (context == NULL) return;
 770 
 771   const ucontext_t *uc = (const ucontext_t*)context;
 772 
 773   st->print_cr("Register to memory mapping:");
 774   st->cr();
 775 
 776   // this is horrendously verbose but the layout of the registers in the
 777   // context does not match how we defined our abstract Register set, so
 778   // we can't just iterate through the gregs area
 779 
 780   // this is only for the "general purpose" registers
 781 
 782 #ifdef AMD64
 783   st->print("RAX="); print_location(st, uc->uc_mcontext.gregs[REG_RAX]);
 784   st->print("RBX="); print_location(st, uc->uc_mcontext.gregs[REG_RBX]);
 785   st->print("RCX="); print_location(st, uc->uc_mcontext.gregs[REG_RCX]);
 786   st->print("RDX="); print_location(st, uc->uc_mcontext.gregs[REG_RDX]);
 787   st->print("RSP="); print_location(st, uc->uc_mcontext.gregs[REG_RSP]);
 788   st->print("RBP="); print_location(st, uc->uc_mcontext.gregs[REG_RBP]);
 789   st->print("RSI="); print_location(st, uc->uc_mcontext.gregs[REG_RSI]);
 790   st->print("RDI="); print_location(st, uc->uc_mcontext.gregs[REG_RDI]);
 791   st->print("R8 ="); print_location(st, uc->uc_mcontext.gregs[REG_R8]);
 792   st->print("R9 ="); print_location(st, uc->uc_mcontext.gregs[REG_R9]);
 793   st->print("R10="); print_location(st, uc->uc_mcontext.gregs[REG_R10]);
 794   st->print("R11="); print_location(st, uc->uc_mcontext.gregs[REG_R11]);
 795   st->print("R12="); print_location(st, uc->uc_mcontext.gregs[REG_R12]);
 796   st->print("R13="); print_location(st, uc->uc_mcontext.gregs[REG_R13]);
 797   st->print("R14="); print_location(st, uc->uc_mcontext.gregs[REG_R14]);
 798   st->print("R15="); print_location(st, uc->uc_mcontext.gregs[REG_R15]);
 799 #else
 800   st->print("EAX="); print_location(st, uc->uc_mcontext.gregs[REG_EAX]);
 801   st->print("EBX="); print_location(st, uc->uc_mcontext.gregs[REG_EBX]);
 802   st->print("ECX="); print_location(st, uc->uc_mcontext.gregs[REG_ECX]);
 803   st->print("EDX="); print_location(st, uc->uc_mcontext.gregs[REG_EDX]);
 804   st->print("ESP="); print_location(st, uc->uc_mcontext.gregs[REG_ESP]);
 805   st->print("EBP="); print_location(st, uc->uc_mcontext.gregs[REG_EBP]);
 806   st->print("ESI="); print_location(st, uc->uc_mcontext.gregs[REG_ESI]);
 807   st->print("EDI="); print_location(st, uc->uc_mcontext.gregs[REG_EDI]);
 808 #endif // AMD64
 809 
 810   st->cr();
 811 }
 812 
 813 void os::setup_fpu() {
 814 #ifndef AMD64
 815   address fpu_cntrl = StubRoutines::addr_fpu_cntrl_wrd_std();
 816   __asm__ volatile (  "fldcw (%0)" :
 817                       : "r" (fpu_cntrl) : "memory");
 818 #endif // !AMD64
 819 }
 820 
 821 #ifndef PRODUCT
 822 void os::verify_stack_alignment() {
 823 #ifdef AMD64
 824   assert(((intptr_t)os::current_stack_pointer() & (StackAlignmentInBytes-1)) == 0, "incorrect stack alignment");
 825 #endif
 826 }
 827 #endif
 828 
 829 
 830 /*
 831  * IA32 only: execute code at a high address in case buggy NX emulation is present. I.e. avoid CS limit
 832  * updates (JDK-8023956).
 833  */
 834 void os::workaround_expand_exec_shield_cs_limit() {
 835 #if defined(IA32)
 836   size_t page_size = os::vm_page_size();
 837   /*
 838    * Take the highest VA the OS will give us and exec
 839    *
 840    * Although using -(pagesz) as mmap hint works on newer kernel as you would
 841    * think, older variants affected by this work-around don't (search forward only).
 842    *
 843    * On the affected distributions, we understand the memory layout to be:
 844    *
 845    *   TASK_LIMIT= 3G, main stack base close to TASK_LIMT.
 846    *
 847    * A few pages south main stack will do it.
 848    *
 849    * If we are embedded in an app other than launcher (initial != main stack),
 850    * we don't have much control or understanding of the address space, just let it slide.
 851    */
 852   char* hint = (char*)(Linux::initial_thread_stack_bottom() -
 853                        (JavaThread::stack_guard_zone_size() + page_size));
 854   char* codebuf = os::attempt_reserve_memory_at(page_size, hint);
 855   if ((codebuf == NULL) || (!os::commit_memory(codebuf, page_size, true))) {
 856     return; // No matter, we tried, best effort.
 857   }
 858 
 859   MemTracker::record_virtual_memory_type((address)codebuf, mtInternal);
 860 
 861   log_info(os)("[CS limit NX emulation work-around, exec code at: %p]", codebuf);
 862 
 863   // Some code to exec: the 'ret' instruction
 864   codebuf[0] = 0xC3;
 865 
 866   // Call the code in the codebuf
 867   __asm__ volatile("call *%0" : : "r"(codebuf));
 868 
 869   // keep the page mapped so CS limit isn't reduced.
 870 #endif
 871 }
 872 
 873 int os::extra_bang_size_in_bytes() {
 874   // JDK-8050147 requires the full cache line bang for x86.
 875   return VM_Version::L1_line_size();
 876 }