1 /*
   2  * Copyright (c) 1999, 2020, 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   void *esp;
  99   __asm__("mov %%" SPELL_REG_SP ", %0":"=r"(esp));
 100   return (address) ((char*)esp + sizeof(long)*2);
 101 #elif defined(__clang__)
 102   void* 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 address os::Linux::ucontext_get_pc(const ucontext_t * uc) {
 120   return (address)uc->uc_mcontext.gregs[REG_PC];
 121 }
 122 
 123 void os::Linux::ucontext_set_pc(ucontext_t * uc, address pc) {
 124   uc->uc_mcontext.gregs[REG_PC] = (intptr_t)pc;
 125 }
 126 
 127 intptr_t* os::Linux::ucontext_get_sp(const ucontext_t * uc) {
 128   return (intptr_t*)uc->uc_mcontext.gregs[REG_SP];
 129 }
 130 
 131 intptr_t* os::Linux::ucontext_get_fp(const ucontext_t * uc) {
 132   return (intptr_t*)uc->uc_mcontext.gregs[REG_FP];
 133 }
 134 
 135 // For Forte Analyzer AsyncGetCallTrace profiling support - thread
 136 // is currently interrupted by SIGPROF.
 137 // os::Solaris::fetch_frame_from_ucontext() tries to skip nested signal
 138 // frames. Currently we don't do that on Linux, so it's the same as
 139 // os::fetch_frame_from_context().
 140 // This method is also used for stack overflow signal handling.
 141 ExtendedPC os::Linux::fetch_frame_from_ucontext(Thread* thread,
 142   const ucontext_t* uc, intptr_t** ret_sp, intptr_t** ret_fp) {
 143 
 144   assert(thread != NULL, "just checking");
 145   assert(ret_sp != NULL, "just checking");
 146   assert(ret_fp != NULL, "just checking");
 147 
 148   return os::fetch_frame_from_context(uc, ret_sp, ret_fp);
 149 }
 150 
 151 ExtendedPC os::fetch_frame_from_context(const void* ucVoid,
 152                     intptr_t** ret_sp, intptr_t** ret_fp) {
 153 
 154   ExtendedPC  epc;
 155   const ucontext_t* uc = (const ucontext_t*)ucVoid;
 156 
 157   if (uc != NULL) {
 158     epc = ExtendedPC(os::Linux::ucontext_get_pc(uc));
 159     if (ret_sp) *ret_sp = os::Linux::ucontext_get_sp(uc);
 160     if (ret_fp) *ret_fp = os::Linux::ucontext_get_fp(uc);
 161   } else {
 162     // construct empty ExtendedPC for return value checking
 163     epc = ExtendedPC(NULL);
 164     if (ret_sp) *ret_sp = (intptr_t *)NULL;
 165     if (ret_fp) *ret_fp = (intptr_t *)NULL;
 166   }
 167 
 168   return epc;
 169 }
 170 
 171 frame os::fetch_frame_from_context(const void* ucVoid) {
 172   intptr_t* sp;
 173   intptr_t* fp;
 174   ExtendedPC epc = fetch_frame_from_context(ucVoid, &sp, &fp);
 175   return frame(sp, fp, epc.pc());
 176 }
 177 
 178 frame os::fetch_frame_from_ucontext(Thread* thread, void* ucVoid) {
 179   intptr_t* sp;
 180   intptr_t* fp;
 181   ExtendedPC epc = os::Linux::fetch_frame_from_ucontext(thread, (ucontext_t*)ucVoid, &sp, &fp);
 182   return frame(sp, fp, epc.pc());
 183 }
 184 
 185 bool os::Linux::get_frame_at_stack_banging_point(JavaThread* thread, ucontext_t* uc, frame* fr) {
 186   address pc = (address) os::Linux::ucontext_get_pc(uc);
 187   if (Interpreter::contains(pc)) {
 188     // interpreter performs stack banging after the fixed frame header has
 189     // been generated while the compilers perform it before. To maintain
 190     // semantic consistency between interpreted and compiled frames, the
 191     // method returns the Java sender of the current frame.
 192     *fr = os::fetch_frame_from_ucontext(thread, uc);
 193     if (!fr->is_first_java_frame()) {
 194       // get_frame_at_stack_banging_point() is only called when we
 195       // have well defined stacks so java_sender() calls do not need
 196       // to assert safe_for_sender() first.
 197       *fr = fr->java_sender();
 198     }
 199   } else {
 200     // more complex code with compiled code
 201     assert(!Interpreter::contains(pc), "Interpreted methods should have been handled above");
 202     CodeBlob* cb = CodeCache::find_blob(pc);
 203     if (cb == NULL || !cb->is_nmethod() || cb->is_frame_complete_at(pc)) {
 204       // Not sure where the pc points to, fallback to default
 205       // stack overflow handling
 206       return false;
 207     } else {
 208       // in compiled code, the stack banging is performed just after the return pc
 209       // has been pushed on the stack
 210       intptr_t* fp = os::Linux::ucontext_get_fp(uc);
 211       intptr_t* sp = os::Linux::ucontext_get_sp(uc);
 212       *fr = frame(sp + 1, fp, (address)*sp);
 213       if (!fr->is_java_frame()) {
 214         assert(!fr->is_first_frame(), "Safety check");
 215         // See java_sender() comment above.
 216         *fr = fr->java_sender();
 217       }
 218     }
 219   }
 220   assert(fr->is_java_frame(), "Safety check");
 221   return true;
 222 }
 223 
 224 // By default, gcc always save frame pointer (%ebp/%rbp) on stack. It may get
 225 // turned off by -fomit-frame-pointer,
 226 frame os::get_sender_for_C_frame(frame* fr) {
 227   return frame(fr->sender_sp(), fr->link(), fr->sender_pc());
 228 }
 229 
 230 intptr_t* _get_previous_fp() {
 231 #ifdef SPARC_WORKS
 232   intptr_t **ebp;
 233   __asm__("mov %%" SPELL_REG_FP ", %0":"=r"(ebp));
 234 #elif defined(__clang__)
 235   intptr_t **ebp;
 236   __asm__ __volatile__ ("mov %%" SPELL_REG_FP ", %0":"=r"(ebp):);
 237 #else
 238   register intptr_t **ebp __asm__ (SPELL_REG_FP);
 239 #endif
 240   // ebp is for this frame (_get_previous_fp). We want the ebp for the
 241   // caller of os::current_frame*(), so go up two frames. However, for
 242   // optimized builds, _get_previous_fp() will be inlined, so only go
 243   // up 1 frame in that case.
 244 #ifdef _NMT_NOINLINE_
 245   return **(intptr_t***)ebp;
 246 #else
 247   return *ebp;
 248 #endif
 249 }
 250 
 251 
 252 frame os::current_frame() {
 253   intptr_t* fp = _get_previous_fp();
 254   frame myframe((intptr_t*)os::current_stack_pointer(),
 255                 (intptr_t*)fp,
 256                 CAST_FROM_FN_PTR(address, os::current_frame));
 257   if (os::is_first_C_frame(&myframe)) {
 258     // stack is not walkable
 259     return frame();
 260   } else {
 261     return os::get_sender_for_C_frame(&myframe);
 262   }
 263 }
 264 
 265 // Utility functions
 266 
 267 // From IA32 System Programming Guide
 268 enum {
 269   trap_page_fault = 0xE
 270 };
 271 
 272 extern "C" JNIEXPORT int
 273 JVM_handle_linux_signal(int sig,
 274                         siginfo_t* info,
 275                         void* ucVoid,
 276                         int abort_if_unrecognized) {
 277   ucontext_t* uc = (ucontext_t*) ucVoid;
 278 
 279   Thread* t = Thread::current_or_null_safe();
 280 
 281   // Must do this before SignalHandlerMark, if crash protection installed we will longjmp away
 282   // (no destructors can be run)
 283   os::ThreadCrashProtection::check_crash_protection(sig, t);
 284 
 285   SignalHandlerMark shm(t);
 286 
 287   // Note: it's not uncommon that JNI code uses signal/sigset to install
 288   // then restore certain signal handler (e.g. to temporarily block SIGPIPE,
 289   // or have a SIGILL handler when detecting CPU type). When that happens,
 290   // JVM_handle_linux_signal() might be invoked with junk info/ucVoid. To
 291   // avoid unnecessary crash when libjsig is not preloaded, try handle signals
 292   // that do not require siginfo/ucontext first.
 293 
 294   if (sig == SIGPIPE || sig == SIGXFSZ) {
 295     // allow chained handler to go first
 296     if (os::Linux::chained_handler(sig, info, ucVoid)) {
 297       return true;
 298     } else {
 299       // Ignoring SIGPIPE/SIGXFSZ - see bugs 4229104 or 6499219
 300       return true;
 301     }
 302   }
 303 
 304 #ifdef CAN_SHOW_REGISTERS_ON_ASSERT
 305   if ((sig == SIGSEGV || sig == SIGBUS) && info != NULL && info->si_addr == g_assert_poison) {
 306     if (handle_assert_poison_fault(ucVoid, info->si_addr)) {
 307       return 1;
 308     }
 309   }
 310 #endif
 311 
 312   JavaThread* thread = NULL;
 313   VMThread* vmthread = NULL;
 314   if (os::Linux::signal_handlers_are_installed) {
 315     if (t != NULL ){
 316       if(t->is_Java_thread()) {
 317         thread = (JavaThread*)t;
 318       }
 319       else if(t->is_VM_thread()){
 320         vmthread = (VMThread *)t;
 321       }
 322     }
 323   }
 324 /*
 325   NOTE: does not seem to work on linux.
 326   if (info == NULL || info->si_code <= 0 || info->si_code == SI_NOINFO) {
 327     // can't decode this kind of signal
 328     info = NULL;
 329   } else {
 330     assert(sig == info->si_signo, "bad siginfo");
 331   }
 332 */
 333   // decide if this trap can be handled by a stub
 334   address stub = NULL;
 335 
 336   address pc          = NULL;
 337 
 338   //%note os_trap_1
 339   if (info != NULL && uc != NULL && thread != NULL) {
 340     pc = (address) os::Linux::ucontext_get_pc(uc);
 341 
 342     if (StubRoutines::is_safefetch_fault(pc)) {
 343       os::Linux::ucontext_set_pc(uc, StubRoutines::continuation_for_safefetch_fault(pc));
 344       return 1;
 345     }
 346 
 347 #ifndef AMD64
 348     // Halt if SI_KERNEL before more crashes get misdiagnosed as Java bugs
 349     // This can happen in any running code (currently more frequently in
 350     // interpreter code but has been seen in compiled code)
 351     if (sig == SIGSEGV && info->si_addr == 0 && info->si_code == SI_KERNEL) {
 352       fatal("An irrecoverable SI_KERNEL SIGSEGV has occurred due "
 353             "to unstable signal handling in this distribution.");
 354     }
 355 #endif // AMD64
 356 
 357     // Handle ALL stack overflow variations here
 358     if (sig == SIGSEGV) {
 359       address addr = (address) info->si_addr;
 360 
 361       // check if fault address is within thread stack
 362       if (thread->is_in_full_stack(addr)) {
 363         // stack overflow
 364         if (thread->in_stack_yellow_reserved_zone(addr)) {
 365           if (thread->thread_state() == _thread_in_Java) {
 366             if (thread->in_stack_reserved_zone(addr)) {
 367               frame fr;
 368               if (os::Linux::get_frame_at_stack_banging_point(thread, uc, &fr)) {
 369                 assert(fr.is_java_frame(), "Must be a Java frame");
 370                 frame activation =
 371                   SharedRuntime::look_for_reserved_stack_annotated_method(thread, fr);
 372                 if (activation.sp() != NULL) {
 373                   thread->disable_stack_reserved_zone();
 374                   if (activation.is_interpreted_frame()) {
 375                     thread->set_reserved_stack_activation((address)(
 376                       activation.fp() + frame::interpreter_frame_initial_sp_offset));
 377                   } else {
 378                     thread->set_reserved_stack_activation((address)activation.unextended_sp());
 379                   }
 380                   return 1;
 381                 }
 382               }
 383             }
 384             // Throw a stack overflow exception.  Guard pages will be reenabled
 385             // while unwinding the stack.
 386             thread->disable_stack_yellow_reserved_zone();
 387             stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::STACK_OVERFLOW);
 388           } else {
 389             // Thread was in the vm or native code.  Return and try to finish.
 390             thread->disable_stack_yellow_reserved_zone();
 391             return 1;
 392           }
 393         } else if (thread->in_stack_red_zone(addr)) {
 394           // Fatal red zone violation.  Disable the guard pages and fall through
 395           // to handle_unexpected_exception way down below.
 396           thread->disable_stack_red_zone();
 397           tty->print_raw_cr("An irrecoverable stack overflow has occurred.");
 398 
 399           // This is a likely cause, but hard to verify. Let's just print
 400           // it as a hint.
 401           tty->print_raw_cr("Please check if any of your loaded .so files has "
 402                             "enabled executable stack (see man page execstack(8))");
 403         } else {
 404           // Accessing stack address below sp may cause SEGV if current
 405           // thread has MAP_GROWSDOWN stack. This should only happen when
 406           // current thread was created by user code with MAP_GROWSDOWN flag
 407           // and then attached to VM. See notes in os_linux.cpp.
 408           if (thread->osthread()->expanding_stack() == 0) {
 409              thread->osthread()->set_expanding_stack();
 410              if (os::Linux::manually_expand_stack(thread, addr)) {
 411                thread->osthread()->clear_expanding_stack();
 412                return 1;
 413              }
 414              thread->osthread()->clear_expanding_stack();
 415           } else {
 416              fatal("recursive segv. expanding stack.");
 417           }
 418         }
 419       }
 420     }
 421 
 422     if ((sig == SIGSEGV) && VM_Version::is_cpuinfo_segv_addr(pc)) {
 423       // Verify that OS save/restore AVX registers.
 424       stub = VM_Version::cpuinfo_cont_addr();
 425     }
 426 
 427     if (thread->thread_state() == _thread_in_Java) {
 428       // Java thread running in Java code => find exception handler if any
 429       // a fault inside compiled code, the interpreter, or a stub
 430 
 431       if (sig == SIGSEGV && os::is_poll_address((address)info->si_addr)) {
 432         stub = SharedRuntime::get_poll_stub(pc);
 433       } else if (sig == SIGBUS /* && info->si_code == BUS_OBJERR */) {
 434         // BugId 4454115: A read from a MappedByteBuffer can fault
 435         // here if the underlying file has been truncated.
 436         // Do not crash the VM in such a case.
 437         CodeBlob* cb = CodeCache::find_blob_unsafe(pc);
 438         CompiledMethod* nm = (cb != NULL) ? cb->as_compiled_method_or_null() : NULL;
 439         bool is_unsafe_arraycopy = thread->doing_unsafe_access() && UnsafeCopyMemory::contains_pc(pc);
 440         if ((nm != NULL && nm->has_unsafe_access()) || is_unsafe_arraycopy) {
 441           address next_pc = Assembler::locate_next_instruction(pc);
 442           if (is_unsafe_arraycopy) {
 443             next_pc = UnsafeCopyMemory::page_error_continue_pc(pc);
 444           }
 445           stub = SharedRuntime::handle_unsafe_access(thread, next_pc);
 446         }
 447       }
 448       else
 449 
 450 #ifdef AMD64
 451       if (sig == SIGFPE  &&
 452           (info->si_code == FPE_INTDIV || info->si_code == FPE_FLTDIV)) {
 453         stub =
 454           SharedRuntime::
 455           continuation_for_implicit_exception(thread,
 456                                               pc,
 457                                               SharedRuntime::
 458                                               IMPLICIT_DIVIDE_BY_ZERO);
 459 #else
 460       if (sig == SIGFPE /* && info->si_code == FPE_INTDIV */) {
 461         // HACK: si_code does not work on linux 2.2.12-20!!!
 462         int op = pc[0];
 463         if (op == 0xDB) {
 464           // FIST
 465           // TODO: The encoding of D2I in i486.ad can cause an exception
 466           // prior to the fist instruction if there was an invalid operation
 467           // pending. We want to dismiss that exception. From the win_32
 468           // side it also seems that if it really was the fist causing
 469           // the exception that we do the d2i by hand with different
 470           // rounding. Seems kind of weird.
 471           // NOTE: that we take the exception at the NEXT floating point instruction.
 472           assert(pc[0] == 0xDB, "not a FIST opcode");
 473           assert(pc[1] == 0x14, "not a FIST opcode");
 474           assert(pc[2] == 0x24, "not a FIST opcode");
 475           return true;
 476         } else if (op == 0xF7) {
 477           // IDIV
 478           stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_DIVIDE_BY_ZERO);
 479         } else {
 480           // TODO: handle more cases if we are using other x86 instructions
 481           //   that can generate SIGFPE signal on linux.
 482           tty->print_cr("unknown opcode 0x%X with SIGFPE.", op);
 483           fatal("please update this code.");
 484         }
 485 #endif // AMD64
 486       } else if (sig == SIGSEGV &&
 487                  MacroAssembler::uses_implicit_null_check(info->si_addr)) {
 488           // Determination of interpreter/vtable stub/compiled code null exception
 489           stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_NULL);
 490       }
 491     } else if ((thread->thread_state() == _thread_in_vm ||
 492                 thread->thread_state() == _thread_in_native) &&
 493                (sig == SIGBUS && /* info->si_code == BUS_OBJERR && */
 494                thread->doing_unsafe_access())) {
 495         address next_pc = Assembler::locate_next_instruction(pc);
 496         if (UnsafeCopyMemory::contains_pc(pc)) {
 497           next_pc = UnsafeCopyMemory::page_error_continue_pc(pc);
 498         }
 499         stub = SharedRuntime::handle_unsafe_access(thread, next_pc);
 500     }
 501 
 502     // jni_fast_Get<Primitive>Field can trap at certain pc's if a GC kicks in
 503     // and the heap gets shrunk before the field access.
 504     if ((sig == SIGSEGV) || (sig == SIGBUS)) {
 505       address addr = JNI_FastGetField::find_slowcase_pc(pc);
 506       if (addr != (address)-1) {
 507         stub = addr;
 508       }
 509     }
 510   }
 511 
 512 #ifndef AMD64
 513   // Execution protection violation
 514   //
 515   // This should be kept as the last step in the triage.  We don't
 516   // have a dedicated trap number for a no-execute fault, so be
 517   // conservative and allow other handlers the first shot.
 518   //
 519   // Note: We don't test that info->si_code == SEGV_ACCERR here.
 520   // this si_code is so generic that it is almost meaningless; and
 521   // the si_code for this condition may change in the future.
 522   // Furthermore, a false-positive should be harmless.
 523   if (UnguardOnExecutionViolation > 0 &&
 524       (sig == SIGSEGV || sig == SIGBUS) &&
 525       uc->uc_mcontext.gregs[REG_TRAPNO] == trap_page_fault) {
 526     int page_size = os::vm_page_size();
 527     address addr = (address) info->si_addr;
 528     address pc = os::Linux::ucontext_get_pc(uc);
 529     // Make sure the pc and the faulting address are sane.
 530     //
 531     // If an instruction spans a page boundary, and the page containing
 532     // the beginning of the instruction is executable but the following
 533     // page is not, the pc and the faulting address might be slightly
 534     // different - we still want to unguard the 2nd page in this case.
 535     //
 536     // 15 bytes seems to be a (very) safe value for max instruction size.
 537     bool pc_is_near_addr =
 538       (pointer_delta((void*) addr, (void*) pc, sizeof(char)) < 15);
 539     bool instr_spans_page_boundary =
 540       (align_down((intptr_t) pc ^ (intptr_t) addr,
 541                        (intptr_t) page_size) > 0);
 542 
 543     if (pc == addr || (pc_is_near_addr && instr_spans_page_boundary)) {
 544       static volatile address last_addr =
 545         (address) os::non_memory_address_word();
 546 
 547       // In conservative mode, don't unguard unless the address is in the VM
 548       if (addr != last_addr &&
 549           (UnguardOnExecutionViolation > 1 || os::address_is_in_vm(addr))) {
 550 
 551         // Set memory to RWX and retry
 552         address page_start = align_down(addr, page_size);
 553         bool res = os::protect_memory((char*) page_start, page_size,
 554                                       os::MEM_PROT_RWX);
 555 
 556         log_debug(os)("Execution protection violation "
 557                       "at " INTPTR_FORMAT
 558                       ", unguarding " INTPTR_FORMAT ": %s, errno=%d", p2i(addr),
 559                       p2i(page_start), (res ? "success" : "failed"), errno);
 560         stub = pc;
 561 
 562         // Set last_addr so if we fault again at the same address, we don't end
 563         // up in an endless loop.
 564         //
 565         // There are two potential complications here.  Two threads trapping at
 566         // the same address at the same time could cause one of the threads to
 567         // think it already unguarded, and abort the VM.  Likely very rare.
 568         //
 569         // The other race involves two threads alternately trapping at
 570         // different addresses and failing to unguard the page, resulting in
 571         // an endless loop.  This condition is probably even more unlikely than
 572         // the first.
 573         //
 574         // Although both cases could be avoided by using locks or thread local
 575         // last_addr, these solutions are unnecessary complication: this
 576         // handler is a best-effort safety net, not a complete solution.  It is
 577         // disabled by default and should only be used as a workaround in case
 578         // we missed any no-execute-unsafe VM code.
 579 
 580         last_addr = addr;
 581       }
 582     }
 583   }
 584 #endif // !AMD64
 585 
 586   if (stub != NULL) {
 587     // save all thread context in case we need to restore it
 588     if (thread != NULL) thread->set_saved_exception_pc(pc);
 589 
 590     os::Linux::ucontext_set_pc(uc, stub);
 591     return true;
 592   }
 593 
 594   // signal-chaining
 595   if (os::Linux::chained_handler(sig, info, ucVoid)) {
 596      return true;
 597   }
 598 
 599   if (!abort_if_unrecognized) {
 600     // caller wants another chance, so give it to him
 601     return false;
 602   }
 603 
 604   if (pc == NULL && uc != NULL) {
 605     pc = os::Linux::ucontext_get_pc(uc);
 606   }
 607 
 608   // unmask current signal
 609   sigset_t newset;
 610   sigemptyset(&newset);
 611   sigaddset(&newset, sig);
 612   sigprocmask(SIG_UNBLOCK, &newset, NULL);
 613 
 614   VMError::report_and_die(t, sig, pc, info, ucVoid);
 615 
 616   ShouldNotReachHere();
 617   return true; // Mute compiler
 618 }
 619 
 620 void os::Linux::init_thread_fpu_state(void) {
 621 #ifndef AMD64
 622   // set fpu to 53 bit precision
 623   set_fpu_control_word(0x27f);
 624 #endif // !AMD64
 625 }
 626 
 627 int os::Linux::get_fpu_control_word(void) {
 628 #ifdef AMD64
 629   return 0;
 630 #else
 631   int fpu_control;
 632   _FPU_GETCW(fpu_control);
 633   return fpu_control & 0xffff;
 634 #endif // AMD64
 635 }
 636 
 637 void os::Linux::set_fpu_control_word(int fpu_control) {
 638 #ifndef AMD64
 639   _FPU_SETCW(fpu_control);
 640 #endif // !AMD64
 641 }
 642 
 643 // Check that the linux kernel version is 2.4 or higher since earlier
 644 // versions do not support SSE without patches.
 645 bool os::supports_sse() {
 646 #ifdef AMD64
 647   return true;
 648 #else
 649   struct utsname uts;
 650   if( uname(&uts) != 0 ) return false; // uname fails?
 651   char *minor_string;
 652   int major = strtol(uts.release,&minor_string,10);
 653   int minor = strtol(minor_string+1,NULL,10);
 654   bool result = (major > 2 || (major==2 && minor >= 4));
 655   log_info(os)("OS version is %d.%d, which %s support SSE/SSE2",
 656                major,minor, result ? "DOES" : "does NOT");
 657   return result;
 658 #endif // AMD64
 659 }
 660 
 661 bool os::is_allocatable(size_t bytes) {
 662 #ifdef AMD64
 663   // unused on amd64?
 664   return true;
 665 #else
 666 
 667   if (bytes < 2 * G) {
 668     return true;
 669   }
 670 
 671   char* addr = reserve_memory(bytes, NULL);
 672 
 673   if (addr != NULL) {
 674     release_memory(addr, bytes);
 675   }
 676 
 677   return addr != NULL;
 678 #endif // AMD64
 679 }
 680 
 681 ////////////////////////////////////////////////////////////////////////////////
 682 // thread stack
 683 
 684 // Minimum usable stack sizes required to get to user code. Space for
 685 // HotSpot guard pages is added later.
 686 size_t os::Posix::_compiler_thread_min_stack_allowed = 48 * K;
 687 size_t os::Posix::_java_thread_min_stack_allowed = 40 * K;
 688 #ifdef _LP64
 689 size_t os::Posix::_vm_internal_thread_min_stack_allowed = 64 * K;
 690 #else
 691 size_t os::Posix::_vm_internal_thread_min_stack_allowed = (48 DEBUG_ONLY(+ 4)) * K;
 692 #endif // _LP64
 693 
 694 // return default stack size for thr_type
 695 size_t os::Posix::default_stack_size(os::ThreadType thr_type) {
 696   // default stack size (compiler thread needs larger stack)
 697 #ifdef AMD64
 698   size_t s = (thr_type == os::compiler_thread ? 4 * M : 1 * M);
 699 #else
 700   size_t s = (thr_type == os::compiler_thread ? 2 * M : 512 * K);
 701 #endif // AMD64
 702   return s;
 703 }
 704 
 705 /////////////////////////////////////////////////////////////////////////////
 706 // helper functions for fatal error handler
 707 
 708 void os::print_context(outputStream *st, const void *context) {
 709   if (context == NULL) return;
 710 
 711   const ucontext_t *uc = (const ucontext_t*)context;
 712   st->print_cr("Registers:");
 713 #ifdef AMD64
 714   st->print(  "RAX=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RAX]);
 715   st->print(", RBX=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RBX]);
 716   st->print(", RCX=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RCX]);
 717   st->print(", RDX=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RDX]);
 718   st->cr();
 719   st->print(  "RSP=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RSP]);
 720   st->print(", RBP=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RBP]);
 721   st->print(", RSI=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RSI]);
 722   st->print(", RDI=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RDI]);
 723   st->cr();
 724   st->print(  "R8 =" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R8]);
 725   st->print(", R9 =" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R9]);
 726   st->print(", R10=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R10]);
 727   st->print(", R11=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R11]);
 728   st->cr();
 729   st->print(  "R12=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R12]);
 730   st->print(", R13=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R13]);
 731   st->print(", R14=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R14]);
 732   st->print(", R15=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R15]);
 733   st->cr();
 734   st->print(  "RIP=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RIP]);
 735   st->print(", EFLAGS=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_EFL]);
 736   st->print(", CSGSFS=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_CSGSFS]);
 737   st->print(", ERR=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_ERR]);
 738   st->cr();
 739   st->print("  TRAPNO=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_TRAPNO]);
 740 #else
 741   st->print(  "EAX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EAX]);
 742   st->print(", EBX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EBX]);
 743   st->print(", ECX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_ECX]);
 744   st->print(", EDX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EDX]);
 745   st->cr();
 746   st->print(  "ESP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_UESP]);
 747   st->print(", EBP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EBP]);
 748   st->print(", ESI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_ESI]);
 749   st->print(", EDI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EDI]);
 750   st->cr();
 751   st->print(  "EIP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EIP]);
 752   st->print(", EFLAGS=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EFL]);
 753   st->print(", CR2=" PTR64_FORMAT, (uint64_t)uc->uc_mcontext.cr2);
 754 #endif // AMD64
 755   st->cr();
 756   st->cr();
 757 
 758   intptr_t *sp = (intptr_t *)os::Linux::ucontext_get_sp(uc);
 759   st->print_cr("Top of Stack: (sp=" PTR_FORMAT ")", p2i(sp));
 760   print_hex_dump(st, (address)sp, (address)(sp + 8), sizeof(intptr_t));
 761   st->cr();
 762 
 763   // Note: it may be unsafe to inspect memory near pc. For example, pc may
 764   // point to garbage if entry point in an nmethod is corrupted. Leave
 765   // this at the end, and hope for the best.
 766   address pc = os::Linux::ucontext_get_pc(uc);
 767   print_instructions(st, pc, sizeof(char));
 768   st->cr();
 769 }
 770 
 771 void os::print_register_info(outputStream *st, const void *context) {
 772   if (context == NULL) return;
 773 
 774   const ucontext_t *uc = (const ucontext_t*)context;
 775 
 776   st->print_cr("Register to memory mapping:");
 777   st->cr();
 778 
 779   // this is horrendously verbose but the layout of the registers in the
 780   // context does not match how we defined our abstract Register set, so
 781   // we can't just iterate through the gregs area
 782 
 783   // this is only for the "general purpose" registers
 784 
 785 #ifdef AMD64
 786   st->print("RAX="); print_location(st, uc->uc_mcontext.gregs[REG_RAX]);
 787   st->print("RBX="); print_location(st, uc->uc_mcontext.gregs[REG_RBX]);
 788   st->print("RCX="); print_location(st, uc->uc_mcontext.gregs[REG_RCX]);
 789   st->print("RDX="); print_location(st, uc->uc_mcontext.gregs[REG_RDX]);
 790   st->print("RSP="); print_location(st, uc->uc_mcontext.gregs[REG_RSP]);
 791   st->print("RBP="); print_location(st, uc->uc_mcontext.gregs[REG_RBP]);
 792   st->print("RSI="); print_location(st, uc->uc_mcontext.gregs[REG_RSI]);
 793   st->print("RDI="); print_location(st, uc->uc_mcontext.gregs[REG_RDI]);
 794   st->print("R8 ="); print_location(st, uc->uc_mcontext.gregs[REG_R8]);
 795   st->print("R9 ="); print_location(st, uc->uc_mcontext.gregs[REG_R9]);
 796   st->print("R10="); print_location(st, uc->uc_mcontext.gregs[REG_R10]);
 797   st->print("R11="); print_location(st, uc->uc_mcontext.gregs[REG_R11]);
 798   st->print("R12="); print_location(st, uc->uc_mcontext.gregs[REG_R12]);
 799   st->print("R13="); print_location(st, uc->uc_mcontext.gregs[REG_R13]);
 800   st->print("R14="); print_location(st, uc->uc_mcontext.gregs[REG_R14]);
 801   st->print("R15="); print_location(st, uc->uc_mcontext.gregs[REG_R15]);
 802 #else
 803   st->print("EAX="); print_location(st, uc->uc_mcontext.gregs[REG_EAX]);
 804   st->print("EBX="); print_location(st, uc->uc_mcontext.gregs[REG_EBX]);
 805   st->print("ECX="); print_location(st, uc->uc_mcontext.gregs[REG_ECX]);
 806   st->print("EDX="); print_location(st, uc->uc_mcontext.gregs[REG_EDX]);
 807   st->print("ESP="); print_location(st, uc->uc_mcontext.gregs[REG_ESP]);
 808   st->print("EBP="); print_location(st, uc->uc_mcontext.gregs[REG_EBP]);
 809   st->print("ESI="); print_location(st, uc->uc_mcontext.gregs[REG_ESI]);
 810   st->print("EDI="); print_location(st, uc->uc_mcontext.gregs[REG_EDI]);
 811 #endif // AMD64
 812 
 813   st->cr();
 814 }
 815 
 816 void os::setup_fpu() {
 817 #ifndef AMD64
 818   address fpu_cntrl = StubRoutines::addr_fpu_cntrl_wrd_std();
 819   __asm__ volatile (  "fldcw (%0)" :
 820                       : "r" (fpu_cntrl) : "memory");
 821 #endif // !AMD64
 822 }
 823 
 824 #ifndef PRODUCT
 825 void os::verify_stack_alignment() {
 826 #ifdef AMD64
 827   assert(((intptr_t)os::current_stack_pointer() & (StackAlignmentInBytes-1)) == 0, "incorrect stack alignment");
 828 #endif
 829 }
 830 #endif
 831 
 832 
 833 /*
 834  * IA32 only: execute code at a high address in case buggy NX emulation is present. I.e. avoid CS limit
 835  * updates (JDK-8023956).
 836  */
 837 void os::workaround_expand_exec_shield_cs_limit() {
 838 #if defined(IA32)
 839   assert(Linux::initial_thread_stack_bottom() != NULL, "sanity");
 840   size_t page_size = os::vm_page_size();
 841 
 842   /*
 843    * JDK-8197429
 844    *
 845    * Expand the stack mapping to the end of the initial stack before
 846    * attempting to install the codebuf.  This is needed because newer
 847    * Linux kernels impose a distance of a megabyte between stack
 848    * memory and other memory regions.  If we try to install the
 849    * codebuf before expanding the stack the installation will appear
 850    * to succeed but we'll get a segfault later if we expand the stack
 851    * in Java code.
 852    *
 853    */
 854   if (os::is_primordial_thread()) {
 855     address limit = Linux::initial_thread_stack_bottom();
 856     if (! DisablePrimordialThreadGuardPages) {
 857       limit += JavaThread::stack_red_zone_size() +
 858         JavaThread::stack_yellow_zone_size();
 859     }
 860     os::Linux::expand_stack_to(limit);
 861   }
 862 
 863   /*
 864    * Take the highest VA the OS will give us and exec
 865    *
 866    * Although using -(pagesz) as mmap hint works on newer kernel as you would
 867    * think, older variants affected by this work-around don't (search forward only).
 868    *
 869    * On the affected distributions, we understand the memory layout to be:
 870    *
 871    *   TASK_LIMIT= 3G, main stack base close to TASK_LIMT.
 872    *
 873    * A few pages south main stack will do it.
 874    *
 875    * If we are embedded in an app other than launcher (initial != main stack),
 876    * we don't have much control or understanding of the address space, just let it slide.
 877    */
 878   char* hint = (char*)(Linux::initial_thread_stack_bottom() -
 879                        (JavaThread::stack_guard_zone_size() + page_size));
 880   char* codebuf = os::attempt_reserve_memory_at(page_size, hint);
 881 
 882   if (codebuf == NULL) {
 883     // JDK-8197429: There may be a stack gap of one megabyte between
 884     // the limit of the stack and the nearest memory region: this is a
 885     // Linux kernel workaround for CVE-2017-1000364.  If we failed to
 886     // map our codebuf, try again at an address one megabyte lower.
 887     hint -= 1 * M;
 888     codebuf = os::attempt_reserve_memory_at(page_size, hint);
 889   }
 890 
 891   if ((codebuf == NULL) || (!os::commit_memory(codebuf, page_size, true))) {
 892     return; // No matter, we tried, best effort.
 893   }
 894 
 895   MemTracker::record_virtual_memory_type((address)codebuf, mtInternal);
 896 
 897   log_info(os)("[CS limit NX emulation work-around, exec code at: %p]", codebuf);
 898 
 899   // Some code to exec: the 'ret' instruction
 900   codebuf[0] = 0xC3;
 901 
 902   // Call the code in the codebuf
 903   __asm__ volatile("call *%0" : : "r"(codebuf));
 904 
 905   // keep the page mapped so CS limit isn't reduced.
 906 #endif
 907 }
 908 
 909 int os::extra_bang_size_in_bytes() {
 910   // JDK-8050147 requires the full cache line bang for x86.
 911   return VM_Version::L1_line_size();
 912 }