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/events.hpp"
  55 #include "utilities/vmError.hpp"
  56 
  57 // put OS-includes here
  58 # include <sys/types.h>
  59 # include <sys/mman.h>
  60 # include <pthread.h>
  61 # include <signal.h>
  62 # include <errno.h>
  63 # include <dlfcn.h>
  64 # include <stdlib.h>
  65 # include <stdio.h>
  66 # include <unistd.h>
  67 # include <sys/resource.h>
  68 # include <pthread.h>
  69 # include <sys/stat.h>
  70 # include <sys/time.h>
  71 # include <sys/utsname.h>
  72 # include <sys/socket.h>
  73 # include <sys/wait.h>
  74 # include <pwd.h>
  75 # include <poll.h>
  76 # include <ucontext.h>
  77 #ifndef AMD64
  78 # include <fpu_control.h>
  79 #endif
  80 
  81 #ifdef AMD64
  82 #define REG_SP REG_RSP
  83 #define REG_PC REG_RIP
  84 #define REG_FP REG_RBP
  85 #define SPELL_REG_SP "rsp"
  86 #define SPELL_REG_FP "rbp"
  87 #else
  88 #define REG_SP REG_UESP
  89 #define REG_PC REG_EIP
  90 #define REG_FP REG_EBP
  91 #define SPELL_REG_SP "esp"
  92 #define SPELL_REG_FP "ebp"
  93 #endif // AMD64
  94 
  95 address os::current_stack_pointer() {
  96 #ifdef SPARC_WORKS
  97   register void *esp;
  98   __asm__("mov %%"SPELL_REG_SP", %0":"=r"(esp));
  99   return (address) ((char*)esp + sizeof(long)*2);
 100 #elif defined(__clang__)
 101   intptr_t* esp;
 102   __asm__ __volatile__ ("mov %%"SPELL_REG_SP", %0":"=r"(esp):);
 103   return (address) esp;
 104 #else
 105   register void *esp __asm__ (SPELL_REG_SP);
 106   return (address) esp;
 107 #endif
 108 }
 109 
 110 char* os::non_memory_address_word() {
 111   // Must never look like an address returned by reserve_memory,
 112   // even in its subfields (as defined by the CPU immediate fields,
 113   // if the CPU splits constants across multiple instructions).
 114 
 115   return (char*) -1;
 116 }
 117 
 118 void os::initialize_thread(Thread* thr) {
 119 // Nothing to do.
 120 }
 121 
 122 address os::Linux::ucontext_get_pc(const ucontext_t * uc) {
 123   return (address)uc->uc_mcontext.gregs[REG_PC];
 124 }
 125 
 126 void os::Linux::ucontext_set_pc(ucontext_t * uc, address pc) {
 127   uc->uc_mcontext.gregs[REG_PC] = (intptr_t)pc;
 128 }
 129 
 130 intptr_t* os::Linux::ucontext_get_sp(const ucontext_t * uc) {
 131   return (intptr_t*)uc->uc_mcontext.gregs[REG_SP];
 132 }
 133 
 134 intptr_t* os::Linux::ucontext_get_fp(const ucontext_t * uc) {
 135   return (intptr_t*)uc->uc_mcontext.gregs[REG_FP];
 136 }
 137 
 138 // For Forte Analyzer AsyncGetCallTrace profiling support - thread
 139 // is currently interrupted by SIGPROF.
 140 // os::Solaris::fetch_frame_from_ucontext() tries to skip nested signal
 141 // frames. Currently we don't do that on Linux, so it's the same as
 142 // os::fetch_frame_from_context().
 143 // This method is also used for stack overflow signal handling.
 144 ExtendedPC os::Linux::fetch_frame_from_ucontext(Thread* thread,
 145   const ucontext_t* uc, intptr_t** ret_sp, intptr_t** ret_fp) {
 146 
 147   assert(thread != NULL, "just checking");
 148   assert(ret_sp != NULL, "just checking");
 149   assert(ret_fp != NULL, "just checking");
 150 
 151   return os::fetch_frame_from_context(uc, ret_sp, ret_fp);
 152 }
 153 
 154 ExtendedPC os::fetch_frame_from_context(const void* ucVoid,
 155                     intptr_t** ret_sp, intptr_t** ret_fp) {
 156 
 157   ExtendedPC  epc;
 158   const ucontext_t* uc = (const ucontext_t*)ucVoid;
 159 
 160   if (uc != NULL) {
 161     epc = ExtendedPC(os::Linux::ucontext_get_pc(uc));
 162     if (ret_sp) *ret_sp = os::Linux::ucontext_get_sp(uc);
 163     if (ret_fp) *ret_fp = os::Linux::ucontext_get_fp(uc);
 164   } else {
 165     // construct empty ExtendedPC for return value checking
 166     epc = ExtendedPC(NULL);
 167     if (ret_sp) *ret_sp = (intptr_t *)NULL;
 168     if (ret_fp) *ret_fp = (intptr_t *)NULL;
 169   }
 170 
 171   return epc;
 172 }
 173 
 174 frame os::fetch_frame_from_context(const void* ucVoid) {
 175   intptr_t* sp;
 176   intptr_t* fp;
 177   ExtendedPC epc = fetch_frame_from_context(ucVoid, &sp, &fp);
 178   return frame(sp, fp, epc.pc());
 179 }
 180 
 181 frame os::fetch_frame_from_ucontext(Thread* thread, void* ucVoid) {
 182   intptr_t* sp;
 183   intptr_t* fp;
 184   ExtendedPC epc = os::Linux::fetch_frame_from_ucontext(thread, (ucontext_t*)ucVoid, &sp, &fp);
 185   return frame(sp, fp, epc.pc());
 186 }
 187 
 188 bool os::Linux::get_frame_at_stack_banging_point(JavaThread* thread, ucontext_t* uc, frame* fr) {
 189   address pc = (address) os::Linux::ucontext_get_pc(uc);
 190   if (Interpreter::contains(pc)) {
 191     // interpreter performs stack banging after the fixed frame header has
 192     // been generated while the compilers perform it before. To maintain
 193     // semantic consistency between interpreted and compiled frames, the
 194     // method returns the Java sender of the current frame.
 195     *fr = os::fetch_frame_from_ucontext(thread, uc);
 196     if (!fr->is_first_java_frame()) {
 197       // get_frame_at_stack_banging_point() is only called when we
 198       // have well defined stacks so java_sender() calls do not need
 199       // to assert safe_for_sender() first.
 200       *fr = fr->java_sender();
 201     }
 202   } else {
 203     // more complex code with compiled code
 204     assert(!Interpreter::contains(pc), "Interpreted methods should have been handled above");
 205     CodeBlob* cb = CodeCache::find_blob(pc);
 206     if (cb == NULL || !cb->is_nmethod() || cb->is_frame_complete_at(pc)) {
 207       // Not sure where the pc points to, fallback to default
 208       // stack overflow handling
 209       return false;
 210     } else {
 211       // in compiled code, the stack banging is performed just after the return pc
 212       // has been pushed on the stack
 213       intptr_t* fp = os::Linux::ucontext_get_fp(uc);
 214       intptr_t* sp = os::Linux::ucontext_get_sp(uc);
 215       *fr = frame(sp + 1, fp, (address)*sp);
 216       if (!fr->is_java_frame()) {
 217         assert(!fr->is_first_frame(), "Safety check");
 218         // See java_sender() comment above.
 219         *fr = fr->java_sender();
 220       }
 221     }
 222   }
 223   assert(fr->is_java_frame(), "Safety check");
 224   return true;
 225 }
 226 
 227 // By default, gcc always save frame pointer (%ebp/%rbp) on stack. It may get
 228 // turned off by -fomit-frame-pointer,
 229 frame os::get_sender_for_C_frame(frame* fr) {
 230   return frame(fr->sender_sp(), fr->link(), fr->sender_pc());
 231 }
 232 
 233 intptr_t* _get_previous_fp() {
 234 #ifdef SPARC_WORKS
 235   register intptr_t **ebp;
 236   __asm__("mov %%"SPELL_REG_FP", %0":"=r"(ebp));
 237 #elif defined(__clang__)
 238   intptr_t **ebp;
 239   __asm__ __volatile__ ("mov %%"SPELL_REG_FP", %0":"=r"(ebp):);
 240 #else
 241   register intptr_t **ebp __asm__ (SPELL_REG_FP);
 242 #endif
 243   // ebp is for this frame (_get_previous_fp). We want the ebp for the
 244   // caller of os::current_frame*(), so go up two frames. However, for
 245   // optimized builds, _get_previous_fp() will be inlined, so only go
 246   // up 1 frame in that case.
 247 #ifdef _NMT_NOINLINE_
 248   return **(intptr_t***)ebp;
 249 #else
 250   return *ebp;
 251 #endif
 252 }
 253 
 254 
 255 frame os::current_frame() {
 256   intptr_t* fp = _get_previous_fp();
 257   frame myframe((intptr_t*)os::current_stack_pointer(),
 258                 (intptr_t*)fp,
 259                 CAST_FROM_FN_PTR(address, os::current_frame));
 260   if (os::is_first_C_frame(&myframe)) {
 261     // stack is not walkable
 262     return frame();
 263   } else {
 264     return os::get_sender_for_C_frame(&myframe);
 265   }
 266 }
 267 
 268 // Utility functions
 269 
 270 // From IA32 System Programming Guide
 271 enum {
 272   trap_page_fault = 0xE
 273 };
 274 
 275 extern "C" JNIEXPORT int
 276 JVM_handle_linux_signal(int sig,
 277                         siginfo_t* info,
 278                         void* ucVoid,
 279                         int abort_if_unrecognized) {
 280   ucontext_t* uc = (ucontext_t*) ucVoid;
 281 
 282   Thread* t = Thread::current_or_null_safe();
 283 
 284   // Must do this before SignalHandlerMark, if crash protection installed we will longjmp away
 285   // (no destructors can be run)
 286   os::ThreadCrashProtection::check_crash_protection(sig, t);
 287 
 288   SignalHandlerMark shm(t);
 289 
 290   // Note: it's not uncommon that JNI code uses signal/sigset to install
 291   // then restore certain signal handler (e.g. to temporarily block SIGPIPE,
 292   // or have a SIGILL handler when detecting CPU type). When that happens,
 293   // JVM_handle_linux_signal() might be invoked with junk info/ucVoid. To
 294   // avoid unnecessary crash when libjsig is not preloaded, try handle signals
 295   // that do not require siginfo/ucontext first.
 296 
 297   if (sig == SIGPIPE || sig == SIGXFSZ) {
 298     // allow chained handler to go first
 299     if (os::Linux::chained_handler(sig, info, ucVoid)) {
 300       return true;
 301     } else {
 302       // Ignoring SIGPIPE/SIGXFSZ - see bugs 4229104 or 6499219
 303       return true;
 304     }
 305   }
 306 
 307   JavaThread* thread = NULL;
 308   VMThread* vmthread = NULL;
 309   if (os::Linux::signal_handlers_are_installed) {
 310     if (t != NULL ){
 311       if(t->is_Java_thread()) {
 312         thread = (JavaThread*)t;
 313       }
 314       else if(t->is_VM_thread()){
 315         vmthread = (VMThread *)t;
 316       }
 317     }
 318   }
 319 /*
 320   NOTE: does not seem to work on linux.
 321   if (info == NULL || info->si_code <= 0 || info->si_code == SI_NOINFO) {
 322     // can't decode this kind of signal
 323     info = NULL;
 324   } else {
 325     assert(sig == info->si_signo, "bad siginfo");
 326   }
 327 */
 328   // decide if this trap can be handled by a stub
 329   address stub = NULL;
 330 
 331   address pc          = NULL;
 332 
 333   //%note os_trap_1
 334   if (info != NULL && uc != NULL && thread != NULL) {
 335     pc = (address) os::Linux::ucontext_get_pc(uc);
 336 
 337     if (StubRoutines::is_safefetch_fault(pc)) {
 338       os::Linux::ucontext_set_pc(uc, StubRoutines::continuation_for_safefetch_fault(pc));
 339       return 1;
 340     }
 341 
 342 #ifndef AMD64
 343     // Halt if SI_KERNEL before more crashes get misdiagnosed as Java bugs
 344     // This can happen in any running code (currently more frequently in
 345     // interpreter code but has been seen in compiled code)
 346     if (sig == SIGSEGV && info->si_addr == 0 && info->si_code == SI_KERNEL) {
 347       fatal("An irrecoverable SI_KERNEL SIGSEGV has occurred due "
 348             "to unstable signal handling in this distribution.");
 349     }
 350 #endif // AMD64
 351 
 352     // Handle ALL stack overflow variations here
 353     if (sig == SIGSEGV) {
 354       address addr = (address) info->si_addr;
 355 
 356       // check if fault address is within thread stack
 357       if (thread->on_local_stack(addr)) {
 358         // stack overflow
 359         if (thread->in_stack_yellow_reserved_zone(addr)) {
 360           if (thread->thread_state() == _thread_in_Java) {
 361             if (thread->in_stack_reserved_zone(addr)) {
 362               frame fr;
 363               if (os::Linux::get_frame_at_stack_banging_point(thread, uc, &fr)) {
 364                 assert(fr.is_java_frame(), "Must be a Java frame");
 365                 frame activation =
 366                   SharedRuntime::look_for_reserved_stack_annotated_method(thread, fr);
 367                 if (activation.sp() != NULL) {
 368                   thread->disable_stack_reserved_zone();
 369                   if (activation.is_interpreted_frame()) {
 370                     thread->set_reserved_stack_activation((address)(
 371                       activation.fp() + frame::interpreter_frame_initial_sp_offset));
 372                   } else {
 373                     thread->set_reserved_stack_activation((address)activation.unextended_sp());
 374                   }
 375                   return 1;
 376                 }
 377               }
 378             }
 379             // Throw a stack overflow exception.  Guard pages will be reenabled
 380             // while unwinding the stack.
 381             thread->disable_stack_yellow_reserved_zone();
 382             stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::STACK_OVERFLOW);
 383           } else {
 384             // Thread was in the vm or native code.  Return and try to finish.
 385             thread->disable_stack_yellow_reserved_zone();
 386             return 1;
 387           }
 388         } else if (thread->in_stack_red_zone(addr)) {
 389           // Fatal red zone violation.  Disable the guard pages and fall through
 390           // to handle_unexpected_exception way down below.
 391           thread->disable_stack_red_zone();
 392           tty->print_raw_cr("An irrecoverable stack overflow has occurred.");
 393 
 394           // This is a likely cause, but hard to verify. Let's just print
 395           // it as a hint.
 396           tty->print_raw_cr("Please check if any of your loaded .so files has "
 397                             "enabled executable stack (see man page execstack(8))");
 398         } else {
 399           // Accessing stack address below sp may cause SEGV if current
 400           // thread has MAP_GROWSDOWN stack. This should only happen when
 401           // current thread was created by user code with MAP_GROWSDOWN flag
 402           // and then attached to VM. See notes in os_linux.cpp.
 403           if (thread->osthread()->expanding_stack() == 0) {
 404              thread->osthread()->set_expanding_stack();
 405              if (os::Linux::manually_expand_stack(thread, addr)) {
 406                thread->osthread()->clear_expanding_stack();
 407                return 1;
 408              }
 409              thread->osthread()->clear_expanding_stack();
 410           } else {
 411              fatal("recursive segv. expanding stack.");
 412           }
 413         }
 414       }
 415     }
 416 
 417     if ((sig == SIGSEGV) && VM_Version::is_cpuinfo_segv_addr(pc)) {
 418       // Verify that OS save/restore AVX registers.
 419       stub = VM_Version::cpuinfo_cont_addr();
 420     }
 421 
 422     if (thread->thread_state() == _thread_in_Java) {
 423       // Java thread running in Java code => find exception handler if any
 424       // a fault inside compiled code, the interpreter, or a stub
 425 
 426       if (sig == SIGSEGV && os::is_poll_address((address)info->si_addr)) {
 427         stub = SharedRuntime::get_poll_stub(pc);
 428       } else if (sig == SIGBUS /* && info->si_code == BUS_OBJERR */) {
 429         // BugId 4454115: A read from a MappedByteBuffer can fault
 430         // here if the underlying file has been truncated.
 431         // Do not crash the VM in such a case.
 432         CodeBlob* cb = CodeCache::find_blob_unsafe(pc);
 433         CompiledMethod* nm = (cb != NULL) ? cb->as_compiled_method_or_null() : NULL;
 434         if (nm != NULL && nm->has_unsafe_access()) {
 435           address next_pc = Assembler::locate_next_instruction(pc);
 436           stub = SharedRuntime::handle_unsafe_access(thread, next_pc);
 437         }
 438       }
 439       else
 440 
 441 #ifdef AMD64
 442       if (sig == SIGFPE  &&
 443           (info->si_code == FPE_INTDIV || info->si_code == FPE_FLTDIV)) {
 444         stub =
 445           SharedRuntime::
 446           continuation_for_implicit_exception(thread,
 447                                               pc,
 448                                               SharedRuntime::
 449                                               IMPLICIT_DIVIDE_BY_ZERO);
 450 #else
 451       if (sig == SIGFPE /* && info->si_code == FPE_INTDIV */) {
 452         // HACK: si_code does not work on linux 2.2.12-20!!!
 453         int op = pc[0];
 454         if (op == 0xDB) {
 455           // FIST
 456           // TODO: The encoding of D2I in i486.ad can cause an exception
 457           // prior to the fist instruction if there was an invalid operation
 458           // pending. We want to dismiss that exception. From the win_32
 459           // side it also seems that if it really was the fist causing
 460           // the exception that we do the d2i by hand with different
 461           // rounding. Seems kind of weird.
 462           // NOTE: that we take the exception at the NEXT floating point instruction.
 463           assert(pc[0] == 0xDB, "not a FIST opcode");
 464           assert(pc[1] == 0x14, "not a FIST opcode");
 465           assert(pc[2] == 0x24, "not a FIST opcode");
 466           return true;
 467         } else if (op == 0xF7) {
 468           // IDIV
 469           stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_DIVIDE_BY_ZERO);
 470         } else {
 471           // TODO: handle more cases if we are using other x86 instructions
 472           //   that can generate SIGFPE signal on linux.
 473           tty->print_cr("unknown opcode 0x%X with SIGFPE.", op);
 474           fatal("please update this code.");
 475         }
 476 #endif // AMD64
 477       } else if (sig == SIGSEGV &&
 478                !MacroAssembler::needs_explicit_null_check((intptr_t)info->si_addr)) {
 479           // Determination of interpreter/vtable stub/compiled code null exception
 480           stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_NULL);
 481       }
 482     } else if (thread->thread_state() == _thread_in_vm &&
 483                sig == SIGBUS && /* info->si_code == BUS_OBJERR && */
 484                thread->doing_unsafe_access()) {
 485         address next_pc = Assembler::locate_next_instruction(pc);
 486         stub = SharedRuntime::handle_unsafe_access(thread, next_pc);
 487     }
 488 
 489     // jni_fast_Get<Primitive>Field can trap at certain pc's if a GC kicks in
 490     // and the heap gets shrunk before the field access.
 491     if ((sig == SIGSEGV) || (sig == SIGBUS)) {
 492       address addr = JNI_FastGetField::find_slowcase_pc(pc);
 493       if (addr != (address)-1) {
 494         stub = addr;
 495       }
 496     }
 497 
 498     // Check to see if we caught the safepoint code in the
 499     // process of write protecting the memory serialization page.
 500     // It write enables the page immediately after protecting it
 501     // so we can just return to retry the write.
 502     if ((sig == SIGSEGV) &&
 503         os::is_memory_serialize_page(thread, (address) info->si_addr)) {
 504       // Block current thread until the memory serialize page permission restored.
 505       os::block_on_serialize_page_trap();
 506       return true;
 507     }
 508   }
 509 
 510 #ifndef AMD64
 511   // Execution protection violation
 512   //
 513   // This should be kept as the last step in the triage.  We don't
 514   // have a dedicated trap number for a no-execute fault, so be
 515   // conservative and allow other handlers the first shot.
 516   //
 517   // Note: We don't test that info->si_code == SEGV_ACCERR here.
 518   // this si_code is so generic that it is almost meaningless; and
 519   // the si_code for this condition may change in the future.
 520   // Furthermore, a false-positive should be harmless.
 521   if (UnguardOnExecutionViolation > 0 &&
 522       (sig == SIGSEGV || sig == SIGBUS) &&
 523       uc->uc_mcontext.gregs[REG_TRAPNO] == trap_page_fault) {
 524     int page_size = os::vm_page_size();
 525     address addr = (address) info->si_addr;
 526     address pc = os::Linux::ucontext_get_pc(uc);
 527     // Make sure the pc and the faulting address are sane.
 528     //
 529     // If an instruction spans a page boundary, and the page containing
 530     // the beginning of the instruction is executable but the following
 531     // page is not, the pc and the faulting address might be slightly
 532     // different - we still want to unguard the 2nd page in this case.
 533     //
 534     // 15 bytes seems to be a (very) safe value for max instruction size.
 535     bool pc_is_near_addr =
 536       (pointer_delta((void*) addr, (void*) pc, sizeof(char)) < 15);
 537     bool instr_spans_page_boundary =
 538       (align_down((intptr_t) pc ^ (intptr_t) addr,
 539                        (intptr_t) page_size) > 0);
 540 
 541     if (pc == addr || (pc_is_near_addr && instr_spans_page_boundary)) {
 542       static volatile address last_addr =
 543         (address) os::non_memory_address_word();
 544 
 545       // In conservative mode, don't unguard unless the address is in the VM
 546       if (addr != last_addr &&
 547           (UnguardOnExecutionViolation > 1 || os::address_is_in_vm(addr))) {
 548 
 549         // Set memory to RWX and retry
 550         address page_start = align_down(addr, page_size);
 551         bool res = os::protect_memory((char*) page_start, page_size,
 552                                       os::MEM_PROT_RWX);
 553 
 554         log_debug(os)("Execution protection violation "
 555                       "at " INTPTR_FORMAT
 556                       ", unguarding " INTPTR_FORMAT ": %s, errno=%d", p2i(addr),
 557                       p2i(page_start), (res ? "success" : "failed"), errno);
 558         stub = pc;
 559 
 560         // Set last_addr so if we fault again at the same address, we don't end
 561         // up in an endless loop.
 562         //
 563         // There are two potential complications here.  Two threads trapping at
 564         // the same address at the same time could cause one of the threads to
 565         // think it already unguarded, and abort the VM.  Likely very rare.
 566         //
 567         // The other race involves two threads alternately trapping at
 568         // different addresses and failing to unguard the page, resulting in
 569         // an endless loop.  This condition is probably even more unlikely than
 570         // the first.
 571         //
 572         // Although both cases could be avoided by using locks or thread local
 573         // last_addr, these solutions are unnecessary complication: this
 574         // handler is a best-effort safety net, not a complete solution.  It is
 575         // disabled by default and should only be used as a workaround in case
 576         // we missed any no-execute-unsafe VM code.
 577 
 578         last_addr = addr;
 579       }
 580     }
 581   }
 582 #endif // !AMD64
 583 
 584   if (stub != NULL) {
 585     // save all thread context in case we need to restore it
 586     if (thread != NULL) thread->set_saved_exception_pc(pc);
 587 
 588     os::Linux::ucontext_set_pc(uc, stub);
 589     return true;
 590   }
 591 
 592   // signal-chaining
 593   if (os::Linux::chained_handler(sig, info, ucVoid)) {
 594      return true;
 595   }
 596 
 597   if (!abort_if_unrecognized) {
 598     // caller wants another chance, so give it to him
 599     return false;
 600   }
 601 
 602   if (pc == NULL && uc != NULL) {
 603     pc = os::Linux::ucontext_get_pc(uc);
 604   }
 605 
 606   // unmask current signal
 607   sigset_t newset;
 608   sigemptyset(&newset);
 609   sigaddset(&newset, sig);
 610   sigprocmask(SIG_UNBLOCK, &newset, NULL);
 611 
 612   VMError::report_and_die(t, sig, pc, info, ucVoid);
 613 
 614   ShouldNotReachHere();
 615   return true; // Mute compiler
 616 }
 617 
 618 void os::Linux::init_thread_fpu_state(void) {
 619 #ifndef AMD64
 620   // set fpu to 53 bit precision
 621   set_fpu_control_word(0x27f);
 622 #endif // !AMD64
 623 }
 624 
 625 int os::Linux::get_fpu_control_word(void) {
 626 #ifdef AMD64
 627   return 0;
 628 #else
 629   int fpu_control;
 630   _FPU_GETCW(fpu_control);
 631   return fpu_control & 0xffff;
 632 #endif // AMD64
 633 }
 634 
 635 void os::Linux::set_fpu_control_word(int fpu_control) {
 636 #ifndef AMD64
 637   _FPU_SETCW(fpu_control);
 638 #endif // !AMD64
 639 }
 640 
 641 // Check that the linux kernel version is 2.4 or higher since earlier
 642 // versions do not support SSE without patches.
 643 bool os::supports_sse() {
 644 #ifdef AMD64
 645   return true;
 646 #else
 647   struct utsname uts;
 648   if( uname(&uts) != 0 ) return false; // uname fails?
 649   char *minor_string;
 650   int major = strtol(uts.release,&minor_string,10);
 651   int minor = strtol(minor_string+1,NULL,10);
 652   bool result = (major > 2 || (major==2 && minor >= 4));
 653   log_info(os)("OS version is %d.%d, which %s support SSE/SSE2",
 654                major,minor, result ? "DOES" : "does NOT");
 655   return result;
 656 #endif // AMD64
 657 }
 658 
 659 bool os::is_allocatable(size_t bytes) {
 660 #ifdef AMD64
 661   // unused on amd64?
 662   return true;
 663 #else
 664 
 665   if (bytes < 2 * G) {
 666     return true;
 667   }
 668 
 669   char* addr = reserve_memory(bytes, NULL);
 670 
 671   if (addr != NULL) {
 672     release_memory(addr, bytes);
 673   }
 674 
 675   return addr != NULL;
 676 #endif // AMD64
 677 }
 678 
 679 ////////////////////////////////////////////////////////////////////////////////
 680 // thread stack
 681 
 682 // Minimum usable stack sizes required to get to user code. Space for
 683 // HotSpot guard pages is added later.
 684 size_t os::Posix::_compiler_thread_min_stack_allowed = 48 * K;
 685 size_t os::Posix::_java_thread_min_stack_allowed = 40 * K;
 686 #ifdef _LP64
 687 size_t os::Posix::_vm_internal_thread_min_stack_allowed = 64 * K;
 688 #else
 689 size_t os::Posix::_vm_internal_thread_min_stack_allowed = (48 DEBUG_ONLY(+ 4)) * K;
 690 #endif // _LP64
 691 
 692 // return default stack size for thr_type
 693 size_t os::Posix::default_stack_size(os::ThreadType thr_type) {
 694   // default stack size (compiler thread needs larger stack)
 695 #ifdef AMD64
 696   size_t s = (thr_type == os::compiler_thread ? 4 * M : 1 * M);
 697 #else
 698   size_t s = (thr_type == os::compiler_thread ? 2 * M : 512 * K);
 699 #endif // AMD64
 700   return s;
 701 }
 702 
 703 /////////////////////////////////////////////////////////////////////////////
 704 // helper functions for fatal error handler
 705 
 706 void os::print_context(outputStream *st, const void *context) {
 707   if (context == NULL) return;
 708 
 709   const ucontext_t *uc = (const ucontext_t*)context;
 710   st->print_cr("Registers:");
 711 #ifdef AMD64
 712   st->print(  "RAX=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RAX]);
 713   st->print(", RBX=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RBX]);
 714   st->print(", RCX=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RCX]);
 715   st->print(", RDX=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RDX]);
 716   st->cr();
 717   st->print(  "RSP=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RSP]);
 718   st->print(", RBP=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RBP]);
 719   st->print(", RSI=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RSI]);
 720   st->print(", RDI=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RDI]);
 721   st->cr();
 722   st->print(  "R8 =" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R8]);
 723   st->print(", R9 =" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R9]);
 724   st->print(", R10=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R10]);
 725   st->print(", R11=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R11]);
 726   st->cr();
 727   st->print(  "R12=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R12]);
 728   st->print(", R13=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R13]);
 729   st->print(", R14=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R14]);
 730   st->print(", R15=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R15]);
 731   st->cr();
 732   st->print(  "RIP=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RIP]);
 733   st->print(", EFLAGS=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_EFL]);
 734   st->print(", CSGSFS=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_CSGSFS]);
 735   st->print(", ERR=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_ERR]);
 736   st->cr();
 737   st->print("  TRAPNO=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_TRAPNO]);
 738 #else
 739   st->print(  "EAX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EAX]);
 740   st->print(", EBX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EBX]);
 741   st->print(", ECX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_ECX]);
 742   st->print(", EDX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EDX]);
 743   st->cr();
 744   st->print(  "ESP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_UESP]);
 745   st->print(", EBP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EBP]);
 746   st->print(", ESI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_ESI]);
 747   st->print(", EDI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EDI]);
 748   st->cr();
 749   st->print(  "EIP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EIP]);
 750   st->print(", EFLAGS=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EFL]);
 751   st->print(", CR2=" PTR64_FORMAT, (uint64_t)uc->uc_mcontext.cr2);
 752 #endif // AMD64
 753   st->cr();
 754   st->cr();
 755 
 756   intptr_t *sp = (intptr_t *)os::Linux::ucontext_get_sp(uc);
 757   st->print_cr("Top of Stack: (sp=" PTR_FORMAT ")", p2i(sp));
 758   print_hex_dump(st, (address)sp, (address)(sp + 8), sizeof(intptr_t));
 759   st->cr();
 760 
 761   // Note: it may be unsafe to inspect memory near pc. For example, pc may
 762   // point to garbage if entry point in an nmethod is corrupted. Leave
 763   // this at the end, and hope for the best.
 764   address pc = os::Linux::ucontext_get_pc(uc);
 765   st->print_cr("Instructions: (pc=" PTR_FORMAT ")", p2i(pc));
 766   print_hex_dump(st, pc - 32, pc + 32, sizeof(char));
 767 }
 768 
 769 void os::print_register_info(outputStream *st, const void *context) {
 770   if (context == NULL) return;
 771 
 772   const ucontext_t *uc = (const ucontext_t*)context;
 773 
 774   st->print_cr("Register to memory mapping:");
 775   st->cr();
 776 
 777   // this is horrendously verbose but the layout of the registers in the
 778   // context does not match how we defined our abstract Register set, so
 779   // we can't just iterate through the gregs area
 780 
 781   // this is only for the "general purpose" registers
 782 
 783 #ifdef AMD64
 784   st->print("RAX="); print_location(st, uc->uc_mcontext.gregs[REG_RAX]);
 785   st->print("RBX="); print_location(st, uc->uc_mcontext.gregs[REG_RBX]);
 786   st->print("RCX="); print_location(st, uc->uc_mcontext.gregs[REG_RCX]);
 787   st->print("RDX="); print_location(st, uc->uc_mcontext.gregs[REG_RDX]);
 788   st->print("RSP="); print_location(st, uc->uc_mcontext.gregs[REG_RSP]);
 789   st->print("RBP="); print_location(st, uc->uc_mcontext.gregs[REG_RBP]);
 790   st->print("RSI="); print_location(st, uc->uc_mcontext.gregs[REG_RSI]);
 791   st->print("RDI="); print_location(st, uc->uc_mcontext.gregs[REG_RDI]);
 792   st->print("R8 ="); print_location(st, uc->uc_mcontext.gregs[REG_R8]);
 793   st->print("R9 ="); print_location(st, uc->uc_mcontext.gregs[REG_R9]);
 794   st->print("R10="); print_location(st, uc->uc_mcontext.gregs[REG_R10]);
 795   st->print("R11="); print_location(st, uc->uc_mcontext.gregs[REG_R11]);
 796   st->print("R12="); print_location(st, uc->uc_mcontext.gregs[REG_R12]);
 797   st->print("R13="); print_location(st, uc->uc_mcontext.gregs[REG_R13]);
 798   st->print("R14="); print_location(st, uc->uc_mcontext.gregs[REG_R14]);
 799   st->print("R15="); print_location(st, uc->uc_mcontext.gregs[REG_R15]);
 800 #else
 801   st->print("EAX="); print_location(st, uc->uc_mcontext.gregs[REG_EAX]);
 802   st->print("EBX="); print_location(st, uc->uc_mcontext.gregs[REG_EBX]);
 803   st->print("ECX="); print_location(st, uc->uc_mcontext.gregs[REG_ECX]);
 804   st->print("EDX="); print_location(st, uc->uc_mcontext.gregs[REG_EDX]);
 805   st->print("ESP="); print_location(st, uc->uc_mcontext.gregs[REG_ESP]);
 806   st->print("EBP="); print_location(st, uc->uc_mcontext.gregs[REG_EBP]);
 807   st->print("ESI="); print_location(st, uc->uc_mcontext.gregs[REG_ESI]);
 808   st->print("EDI="); print_location(st, uc->uc_mcontext.gregs[REG_EDI]);
 809 #endif // AMD64
 810 
 811   st->cr();
 812 }
 813 
 814 void os::setup_fpu() {
 815 #ifndef AMD64
 816   address fpu_cntrl = StubRoutines::addr_fpu_cntrl_wrd_std();
 817   __asm__ volatile (  "fldcw (%0)" :
 818                       : "r" (fpu_cntrl) : "memory");
 819 #endif // !AMD64
 820 }
 821 
 822 #ifndef PRODUCT
 823 void os::verify_stack_alignment() {
 824 #ifdef AMD64
 825   assert(((intptr_t)os::current_stack_pointer() & (StackAlignmentInBytes-1)) == 0, "incorrect stack alignment");
 826 #endif
 827 }
 828 #endif
 829 
 830 
 831 /*
 832  * IA32 only: execute code at a high address in case buggy NX emulation is present. I.e. avoid CS limit
 833  * updates (JDK-8023956).
 834  */
 835 void os::workaround_expand_exec_shield_cs_limit() {
 836 #if defined(IA32)
 837   size_t page_size = os::vm_page_size();
 838 
 839   /*
 840    * JDK-8197429
 841    *
 842    * Expand the stack mapping to the end of the initial stack before
 843    * attempting to install the codebuf.  This is needed because newer
 844    * Linux kernels impose a distance of a megabyte between stack
 845    * memory and other memory regions.  If we try to install the
 846    * codebuf before expanding the stack the installation will appear
 847    * to succeed but we'll get a segfault later if we expand the stack
 848    * in Java code.
 849    *
 850    */
 851   if (os::is_primordial_thread()) {
 852     address limit = Linux::initial_thread_stack_bottom();
 853     if (! DisablePrimordialThreadGuardPages) {
 854       limit += JavaThread::stack_red_zone_size() +
 855         JavaThread::stack_yellow_zone_size();
 856     }
 857     os::Linux::expand_stack_to(limit);
 858   }
 859 
 860   /*
 861    * Take the highest VA the OS will give us and exec
 862    *
 863    * Although using -(pagesz) as mmap hint works on newer kernel as you would
 864    * think, older variants affected by this work-around don't (search forward only).
 865    *
 866    * On the affected distributions, we understand the memory layout to be:
 867    *
 868    *   TASK_LIMIT= 3G, main stack base close to TASK_LIMT.
 869    *
 870    * A few pages south main stack will do it.
 871    *
 872    * If we are embedded in an app other than launcher (initial != main stack),
 873    * we don't have much control or understanding of the address space, just let it slide.
 874    */
 875   char* hint = (char*)(Linux::initial_thread_stack_bottom() -
 876                        (JavaThread::stack_guard_zone_size() + page_size));
 877   char* codebuf = os::attempt_reserve_memory_at(page_size, hint);
 878 
 879   if (codebuf == NULL) {
 880     // JDK-8197429: There may be a stack gap of one megabyte between
 881     // the limit of the stack and the nearest memory region: this is a
 882     // Linux kernel workaround for CVE-2017-1000364.  If we failed to
 883     // map our codebuf, try again at an address one megabyte lower.
 884     hint -= 1 * M;
 885     codebuf = os::attempt_reserve_memory_at(page_size, hint);
 886   }
 887 
 888   if ((codebuf == NULL) || (!os::commit_memory(codebuf, page_size, true))) {
 889     return; // No matter, we tried, best effort.
 890   }
 891 
 892   MemTracker::record_virtual_memory_type((address)codebuf, mtInternal);
 893 
 894   log_info(os)("[CS limit NX emulation work-around, exec code at: %p]", codebuf);
 895 
 896   // Some code to exec: the 'ret' instruction
 897   codebuf[0] = 0xC3;
 898 
 899   // Call the code in the codebuf
 900   __asm__ volatile("call *%0" : : "r"(codebuf));
 901 
 902   // keep the page mapped so CS limit isn't reduced.
 903 #endif
 904 }
 905 
 906 int os::extra_bang_size_in_bytes() {
 907   // JDK-8050147 requires the full cache line bang for x86.
 908   return VM_Version::L1_line_size();
 909 }