1 /*
   2  * Copyright (c) 1999, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 // no precompiled headers
  26 #include "jvm.h"
  27 #include "asm/macroAssembler.hpp"
  28 #include "classfile/classLoader.hpp"
  29 #include "classfile/systemDictionary.hpp"
  30 #include "classfile/vmSymbols.hpp"
  31 #include "code/codeCache.hpp"
  32 #include "code/icBuffer.hpp"
  33 #include "code/vtableStubs.hpp"
  34 #include "interpreter/interpreter.hpp"
  35 #include "logging/log.hpp"
  36 #include "memory/allocation.inline.hpp"
  37 #include "os_share_linux.hpp"
  38 #include "prims/jniFastGetField.hpp"
  39 #include "prims/jvm_misc.hpp"
  40 #include "runtime/arguments.hpp"
  41 #include "runtime/extendedPC.hpp"
  42 #include "runtime/frame.inline.hpp"
  43 #include "runtime/interfaceSupport.inline.hpp"
  44 #include "runtime/java.hpp"
  45 #include "runtime/javaCalls.hpp"
  46 #include "runtime/mutexLocker.hpp"
  47 #include "runtime/osThread.hpp"
  48 #include "runtime/sharedRuntime.hpp"
  49 #include "runtime/stubRoutines.hpp"
  50 #include "runtime/thread.inline.hpp"
  51 #include "runtime/timer.hpp"
  52 #include "services/memTracker.hpp"
  53 #include "utilities/align.hpp"
  54 #include "utilities/debug.hpp"
  55 #include "utilities/events.hpp"
  56 #include "utilities/vmError.hpp"
  57 
  58 // put OS-includes here
  59 # include <sys/types.h>
  60 # include <sys/mman.h>
  61 # include <pthread.h>
  62 # include <signal.h>
  63 # include <errno.h>
  64 # include <dlfcn.h>
  65 # include <stdlib.h>
  66 # include <stdio.h>
  67 # include <unistd.h>
  68 # include <sys/resource.h>
  69 # include <pthread.h>
  70 # include <sys/stat.h>
  71 # include <sys/time.h>
  72 # include <sys/utsname.h>
  73 # include <sys/socket.h>
  74 # include <sys/wait.h>
  75 # include <pwd.h>
  76 # include <poll.h>
  77 # include <ucontext.h>
  78 #ifndef AMD64
  79 # include <fpu_control.h>
  80 #endif
  81 
  82 #ifdef AMD64
  83 #define REG_SP REG_RSP
  84 #define REG_PC REG_RIP
  85 #define REG_FP REG_RBP
  86 #define SPELL_REG_SP "rsp"
  87 #define SPELL_REG_FP "rbp"
  88 #else
  89 #define REG_SP REG_UESP
  90 #define REG_PC REG_EIP
  91 #define REG_FP REG_EBP
  92 #define SPELL_REG_SP "esp"
  93 #define SPELL_REG_FP "ebp"
  94 #endif // AMD64
  95 
  96 address os::current_stack_pointer() {
  97 #ifdef SPARC_WORKS
  98   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     handle_assert_poison_fault(ucVoid, info->si_addr);
 307     return 1;
 308   }
 309 #endif
 310 
 311   JavaThread* thread = NULL;
 312   VMThread* vmthread = NULL;
 313   if (os::Linux::signal_handlers_are_installed) {
 314     if (t != NULL ){
 315       if(t->is_Java_thread()) {
 316         thread = (JavaThread*)t;
 317       }
 318       else if(t->is_VM_thread()){
 319         vmthread = (VMThread *)t;
 320       }
 321     }
 322   }
 323 /*
 324   NOTE: does not seem to work on linux.
 325   if (info == NULL || info->si_code <= 0 || info->si_code == SI_NOINFO) {
 326     // can't decode this kind of signal
 327     info = NULL;
 328   } else {
 329     assert(sig == info->si_signo, "bad siginfo");
 330   }
 331 */
 332   // decide if this trap can be handled by a stub
 333   address stub = NULL;
 334 
 335   address pc          = NULL;
 336 
 337   //%note os_trap_1
 338   if (info != NULL && uc != NULL && thread != NULL) {
 339     pc = (address) os::Linux::ucontext_get_pc(uc);
 340 
 341     if (StubRoutines::is_safefetch_fault(pc)) {
 342       os::Linux::ucontext_set_pc(uc, StubRoutines::continuation_for_safefetch_fault(pc));
 343       return 1;
 344     }
 345 
 346 #ifndef AMD64
 347     // Halt if SI_KERNEL before more crashes get misdiagnosed as Java bugs
 348     // This can happen in any running code (currently more frequently in
 349     // interpreter code but has been seen in compiled code)
 350     if (sig == SIGSEGV && info->si_addr == 0 && info->si_code == SI_KERNEL) {
 351       fatal("An irrecoverable SI_KERNEL SIGSEGV has occurred due "
 352             "to unstable signal handling in this distribution.");
 353     }
 354 #endif // AMD64
 355 
 356     // Handle ALL stack overflow variations here
 357     if (sig == SIGSEGV) {
 358       address addr = (address) info->si_addr;
 359 
 360       // check if fault address is within thread stack
 361       if (thread->on_local_stack(addr)) {
 362         // stack overflow
 363         if (thread->in_stack_yellow_reserved_zone(addr)) {
 364           if (thread->thread_state() == _thread_in_Java) {
 365             if (thread->in_stack_reserved_zone(addr)) {
 366               frame fr;
 367               if (os::Linux::get_frame_at_stack_banging_point(thread, uc, &fr)) {
 368                 assert(fr.is_java_frame(), "Must be a Java frame");
 369                 frame activation =
 370                   SharedRuntime::look_for_reserved_stack_annotated_method(thread, fr);
 371                 if (activation.sp() != NULL) {
 372                   thread->disable_stack_reserved_zone();
 373                   if (activation.is_interpreted_frame()) {
 374                     thread->set_reserved_stack_activation((address)(
 375                       activation.fp() + frame::interpreter_frame_initial_sp_offset));
 376                   } else {
 377                     thread->set_reserved_stack_activation((address)activation.unextended_sp());
 378                   }
 379                   return 1;
 380                 }
 381               }
 382             }
 383             // Throw a stack overflow exception.  Guard pages will be reenabled
 384             // while unwinding the stack.
 385             thread->disable_stack_yellow_reserved_zone();
 386             stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::STACK_OVERFLOW);
 387           } else {
 388             // Thread was in the vm or native code.  Return and try to finish.
 389             thread->disable_stack_yellow_reserved_zone();
 390             return 1;
 391           }
 392         } else if (thread->in_stack_red_zone(addr)) {
 393           // Fatal red zone violation.  Disable the guard pages and fall through
 394           // to handle_unexpected_exception way down below.
 395           thread->disable_stack_red_zone();
 396           tty->print_raw_cr("An irrecoverable stack overflow has occurred.");
 397 
 398           // This is a likely cause, but hard to verify. Let's just print
 399           // it as a hint.
 400           tty->print_raw_cr("Please check if any of your loaded .so files has "
 401                             "enabled executable stack (see man page execstack(8))");
 402         } else {
 403           // Accessing stack address below sp may cause SEGV if current
 404           // thread has MAP_GROWSDOWN stack. This should only happen when
 405           // current thread was created by user code with MAP_GROWSDOWN flag
 406           // and then attached to VM. See notes in os_linux.cpp.
 407           if (thread->osthread()->expanding_stack() == 0) {
 408              thread->osthread()->set_expanding_stack();
 409              if (os::Linux::manually_expand_stack(thread, addr)) {
 410                thread->osthread()->clear_expanding_stack();
 411                return 1;
 412              }
 413              thread->osthread()->clear_expanding_stack();
 414           } else {
 415              fatal("recursive segv. expanding stack.");
 416           }
 417         }
 418       }
 419     }
 420 
 421     if ((sig == SIGSEGV) && VM_Version::is_cpuinfo_segv_addr(pc)) {
 422       // Verify that OS save/restore AVX registers.
 423       stub = VM_Version::cpuinfo_cont_addr();
 424     }
 425 
 426     if (thread->thread_state() == _thread_in_Java) {
 427       // Java thread running in Java code => find exception handler if any
 428       // a fault inside compiled code, the interpreter, or a stub
 429 
 430       if (sig == SIGSEGV && os::is_poll_address((address)info->si_addr)) {
 431         stub = SharedRuntime::get_poll_stub(pc);
 432       } else if (sig == SIGBUS /* && info->si_code == BUS_OBJERR */) {
 433         // BugId 4454115: A read from a MappedByteBuffer can fault
 434         // here if the underlying file has been truncated.
 435         // Do not crash the VM in such a case.
 436         CodeBlob* cb = CodeCache::find_blob_unsafe(pc);
 437         CompiledMethod* nm = (cb != NULL) ? cb->as_compiled_method_or_null() : NULL;
 438         if (nm != NULL && nm->has_unsafe_access()) {
 439           address next_pc = Assembler::locate_next_instruction(pc);
 440           stub = SharedRuntime::handle_unsafe_access(thread, next_pc);
 441         }
 442       }
 443       else
 444 
 445 #ifdef AMD64
 446       if (sig == SIGFPE  &&
 447           (info->si_code == FPE_INTDIV || info->si_code == FPE_FLTDIV)) {
 448         stub =
 449           SharedRuntime::
 450           continuation_for_implicit_exception(thread,
 451                                               pc,
 452                                               SharedRuntime::
 453                                               IMPLICIT_DIVIDE_BY_ZERO);
 454 #else
 455       if (sig == SIGFPE /* && info->si_code == FPE_INTDIV */) {
 456         // HACK: si_code does not work on linux 2.2.12-20!!!
 457         int op = pc[0];
 458         if (op == 0xDB) {
 459           // FIST
 460           // TODO: The encoding of D2I in i486.ad can cause an exception
 461           // prior to the fist instruction if there was an invalid operation
 462           // pending. We want to dismiss that exception. From the win_32
 463           // side it also seems that if it really was the fist causing
 464           // the exception that we do the d2i by hand with different
 465           // rounding. Seems kind of weird.
 466           // NOTE: that we take the exception at the NEXT floating point instruction.
 467           assert(pc[0] == 0xDB, "not a FIST opcode");
 468           assert(pc[1] == 0x14, "not a FIST opcode");
 469           assert(pc[2] == 0x24, "not a FIST opcode");
 470           return true;
 471         } else if (op == 0xF7) {
 472           // IDIV
 473           stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_DIVIDE_BY_ZERO);
 474         } else {
 475           // TODO: handle more cases if we are using other x86 instructions
 476           //   that can generate SIGFPE signal on linux.
 477           tty->print_cr("unknown opcode 0x%X with SIGFPE.", op);
 478           fatal("please update this code.");
 479         }
 480 #endif // AMD64
 481       } else if (sig == SIGSEGV &&
 482                  MacroAssembler::uses_implicit_null_check(info->si_addr)) {
 483           // Determination of interpreter/vtable stub/compiled code null exception
 484           stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_NULL);
 485       }
 486     } else if (thread->thread_state() == _thread_in_vm &&
 487                sig == SIGBUS && /* info->si_code == BUS_OBJERR && */
 488                thread->doing_unsafe_access()) {
 489         address next_pc = Assembler::locate_next_instruction(pc);
 490         stub = SharedRuntime::handle_unsafe_access(thread, next_pc);
 491     }
 492 
 493     // jni_fast_Get<Primitive>Field can trap at certain pc's if a GC kicks in
 494     // and the heap gets shrunk before the field access.
 495     if ((sig == SIGSEGV) || (sig == SIGBUS)) {
 496       address addr = JNI_FastGetField::find_slowcase_pc(pc);
 497       if (addr != (address)-1) {
 498         stub = addr;
 499       }
 500     }
 501 
 502     // Check to see if we caught the safepoint code in the
 503     // process of write protecting the memory serialization page.
 504     // It write enables the page immediately after protecting it
 505     // so we can just return to retry the write.
 506     if ((sig == SIGSEGV) &&
 507         os::is_memory_serialize_page(thread, (address) info->si_addr)) {
 508       // Block current thread until the memory serialize page permission restored.
 509       os::block_on_serialize_page_trap();
 510       return true;
 511     }
 512   }
 513 
 514 #ifndef AMD64
 515   // Execution protection violation
 516   //
 517   // This should be kept as the last step in the triage.  We don't
 518   // have a dedicated trap number for a no-execute fault, so be
 519   // conservative and allow other handlers the first shot.
 520   //
 521   // Note: We don't test that info->si_code == SEGV_ACCERR here.
 522   // this si_code is so generic that it is almost meaningless; and
 523   // the si_code for this condition may change in the future.
 524   // Furthermore, a false-positive should be harmless.
 525   if (UnguardOnExecutionViolation > 0 &&
 526       (sig == SIGSEGV || sig == SIGBUS) &&
 527       uc->uc_mcontext.gregs[REG_TRAPNO] == trap_page_fault) {
 528     int page_size = os::vm_page_size();
 529     address addr = (address) info->si_addr;
 530     address pc = os::Linux::ucontext_get_pc(uc);
 531     // Make sure the pc and the faulting address are sane.
 532     //
 533     // If an instruction spans a page boundary, and the page containing
 534     // the beginning of the instruction is executable but the following
 535     // page is not, the pc and the faulting address might be slightly
 536     // different - we still want to unguard the 2nd page in this case.
 537     //
 538     // 15 bytes seems to be a (very) safe value for max instruction size.
 539     bool pc_is_near_addr =
 540       (pointer_delta((void*) addr, (void*) pc, sizeof(char)) < 15);
 541     bool instr_spans_page_boundary =
 542       (align_down((intptr_t) pc ^ (intptr_t) addr,
 543                        (intptr_t) page_size) > 0);
 544 
 545     if (pc == addr || (pc_is_near_addr && instr_spans_page_boundary)) {
 546       static volatile address last_addr =
 547         (address) os::non_memory_address_word();
 548 
 549       // In conservative mode, don't unguard unless the address is in the VM
 550       if (addr != last_addr &&
 551           (UnguardOnExecutionViolation > 1 || os::address_is_in_vm(addr))) {
 552 
 553         // Set memory to RWX and retry
 554         address page_start = align_down(addr, page_size);
 555         bool res = os::protect_memory((char*) page_start, page_size,
 556                                       os::MEM_PROT_RWX);
 557 
 558         log_debug(os)("Execution protection violation "
 559                       "at " INTPTR_FORMAT
 560                       ", unguarding " INTPTR_FORMAT ": %s, errno=%d", p2i(addr),
 561                       p2i(page_start), (res ? "success" : "failed"), errno);
 562         stub = pc;
 563 
 564         // Set last_addr so if we fault again at the same address, we don't end
 565         // up in an endless loop.
 566         //
 567         // There are two potential complications here.  Two threads trapping at
 568         // the same address at the same time could cause one of the threads to
 569         // think it already unguarded, and abort the VM.  Likely very rare.
 570         //
 571         // The other race involves two threads alternately trapping at
 572         // different addresses and failing to unguard the page, resulting in
 573         // an endless loop.  This condition is probably even more unlikely than
 574         // the first.
 575         //
 576         // Although both cases could be avoided by using locks or thread local
 577         // last_addr, these solutions are unnecessary complication: this
 578         // handler is a best-effort safety net, not a complete solution.  It is
 579         // disabled by default and should only be used as a workaround in case
 580         // we missed any no-execute-unsafe VM code.
 581 
 582         last_addr = addr;
 583       }
 584     }
 585   }
 586 #endif // !AMD64
 587 
 588   if (stub != NULL) {
 589     // save all thread context in case we need to restore it
 590     if (thread != NULL) thread->set_saved_exception_pc(pc);
 591 
 592     os::Linux::ucontext_set_pc(uc, stub);
 593     return true;
 594   }
 595 
 596   // signal-chaining
 597   if (os::Linux::chained_handler(sig, info, ucVoid)) {
 598      return true;
 599   }
 600 
 601   if (!abort_if_unrecognized) {
 602     // caller wants another chance, so give it to him
 603     return false;
 604   }
 605 
 606   if (pc == NULL && uc != NULL) {
 607     pc = os::Linux::ucontext_get_pc(uc);
 608   }
 609 
 610   // unmask current signal
 611   sigset_t newset;
 612   sigemptyset(&newset);
 613   sigaddset(&newset, sig);
 614   sigprocmask(SIG_UNBLOCK, &newset, NULL);
 615 
 616   VMError::report_and_die(t, sig, pc, info, ucVoid);
 617 
 618   ShouldNotReachHere();
 619   return true; // Mute compiler
 620 }
 621 
 622 void os::Linux::init_thread_fpu_state(void) {
 623 #ifndef AMD64
 624   // set fpu to 53 bit precision
 625   set_fpu_control_word(0x27f);
 626 #endif // !AMD64
 627 }
 628 
 629 int os::Linux::get_fpu_control_word(void) {
 630 #ifdef AMD64
 631   return 0;
 632 #else
 633   int fpu_control;
 634   _FPU_GETCW(fpu_control);
 635   return fpu_control & 0xffff;
 636 #endif // AMD64
 637 }
 638 
 639 void os::Linux::set_fpu_control_word(int fpu_control) {
 640 #ifndef AMD64
 641   _FPU_SETCW(fpu_control);
 642 #endif // !AMD64
 643 }
 644 
 645 // Check that the linux kernel version is 2.4 or higher since earlier
 646 // versions do not support SSE without patches.
 647 bool os::supports_sse() {
 648 #ifdef AMD64
 649   return true;
 650 #else
 651   struct utsname uts;
 652   if( uname(&uts) != 0 ) return false; // uname fails?
 653   char *minor_string;
 654   int major = strtol(uts.release,&minor_string,10);
 655   int minor = strtol(minor_string+1,NULL,10);
 656   bool result = (major > 2 || (major==2 && minor >= 4));
 657   log_info(os)("OS version is %d.%d, which %s support SSE/SSE2",
 658                major,minor, result ? "DOES" : "does NOT");
 659   return result;
 660 #endif // AMD64
 661 }
 662 
 663 bool os::is_allocatable(size_t bytes) {
 664 #ifdef AMD64
 665   // unused on amd64?
 666   return true;
 667 #else
 668 
 669   if (bytes < 2 * G) {
 670     return true;
 671   }
 672 
 673   char* addr = reserve_memory(bytes, NULL);
 674 
 675   if (addr != NULL) {
 676     release_memory(addr, bytes);
 677   }
 678 
 679   return addr != NULL;
 680 #endif // AMD64
 681 }
 682 
 683 ////////////////////////////////////////////////////////////////////////////////
 684 // thread stack
 685 
 686 // Minimum usable stack sizes required to get to user code. Space for
 687 // HotSpot guard pages is added later.
 688 size_t os::Posix::_compiler_thread_min_stack_allowed = 48 * K;
 689 size_t os::Posix::_java_thread_min_stack_allowed = 40 * K;
 690 #ifdef _LP64
 691 size_t os::Posix::_vm_internal_thread_min_stack_allowed = 64 * K;
 692 #else
 693 size_t os::Posix::_vm_internal_thread_min_stack_allowed = (48 DEBUG_ONLY(+ 4)) * K;
 694 #endif // _LP64
 695 
 696 // return default stack size for thr_type
 697 size_t os::Posix::default_stack_size(os::ThreadType thr_type) {
 698   // default stack size (compiler thread needs larger stack)
 699 #ifdef AMD64
 700   size_t s = (thr_type == os::compiler_thread ? 4 * M : 1 * M);
 701 #else
 702   size_t s = (thr_type == os::compiler_thread ? 2 * M : 512 * K);
 703 #endif // AMD64
 704   return s;
 705 }
 706 
 707 /////////////////////////////////////////////////////////////////////////////
 708 // helper functions for fatal error handler
 709 
 710 void os::print_context(outputStream *st, const void *context) {
 711   if (context == NULL) return;
 712 
 713   const ucontext_t *uc = (const ucontext_t*)context;
 714   st->print_cr("Registers:");
 715 #ifdef AMD64
 716   st->print(  "RAX=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RAX]);
 717   st->print(", RBX=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RBX]);
 718   st->print(", RCX=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RCX]);
 719   st->print(", RDX=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RDX]);
 720   st->cr();
 721   st->print(  "RSP=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RSP]);
 722   st->print(", RBP=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RBP]);
 723   st->print(", RSI=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RSI]);
 724   st->print(", RDI=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RDI]);
 725   st->cr();
 726   st->print(  "R8 =" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R8]);
 727   st->print(", R9 =" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R9]);
 728   st->print(", R10=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R10]);
 729   st->print(", R11=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R11]);
 730   st->cr();
 731   st->print(  "R12=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R12]);
 732   st->print(", R13=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R13]);
 733   st->print(", R14=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R14]);
 734   st->print(", R15=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R15]);
 735   st->cr();
 736   st->print(  "RIP=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RIP]);
 737   st->print(", EFLAGS=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_EFL]);
 738   st->print(", CSGSFS=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_CSGSFS]);
 739   st->print(", ERR=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_ERR]);
 740   st->cr();
 741   st->print("  TRAPNO=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_TRAPNO]);
 742 #else
 743   st->print(  "EAX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EAX]);
 744   st->print(", EBX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EBX]);
 745   st->print(", ECX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_ECX]);
 746   st->print(", EDX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EDX]);
 747   st->cr();
 748   st->print(  "ESP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_UESP]);
 749   st->print(", EBP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EBP]);
 750   st->print(", ESI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_ESI]);
 751   st->print(", EDI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EDI]);
 752   st->cr();
 753   st->print(  "EIP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EIP]);
 754   st->print(", EFLAGS=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EFL]);
 755   st->print(", CR2=" PTR64_FORMAT, (uint64_t)uc->uc_mcontext.cr2);
 756 #endif // AMD64
 757   st->cr();
 758   st->cr();
 759 
 760   intptr_t *sp = (intptr_t *)os::Linux::ucontext_get_sp(uc);
 761   st->print_cr("Top of Stack: (sp=" PTR_FORMAT ")", p2i(sp));
 762   print_hex_dump(st, (address)sp, (address)(sp + 8), sizeof(intptr_t));
 763   st->cr();
 764 
 765   // Note: it may be unsafe to inspect memory near pc. For example, pc may
 766   // point to garbage if entry point in an nmethod is corrupted. Leave
 767   // this at the end, and hope for the best.
 768   address pc = os::Linux::ucontext_get_pc(uc);
 769   st->print_cr("Instructions: (pc=" PTR_FORMAT ")", p2i(pc));
 770   print_hex_dump(st, pc - 32, pc + 32, sizeof(char));
 771 }
 772 
 773 void os::print_register_info(outputStream *st, const void *context) {
 774   if (context == NULL) return;
 775 
 776   const ucontext_t *uc = (const ucontext_t*)context;
 777 
 778   st->print_cr("Register to memory mapping:");
 779   st->cr();
 780 
 781   // this is horrendously verbose but the layout of the registers in the
 782   // context does not match how we defined our abstract Register set, so
 783   // we can't just iterate through the gregs area
 784 
 785   // this is only for the "general purpose" registers
 786 
 787 #ifdef AMD64
 788   st->print("RAX="); print_location(st, uc->uc_mcontext.gregs[REG_RAX]);
 789   st->print("RBX="); print_location(st, uc->uc_mcontext.gregs[REG_RBX]);
 790   st->print("RCX="); print_location(st, uc->uc_mcontext.gregs[REG_RCX]);
 791   st->print("RDX="); print_location(st, uc->uc_mcontext.gregs[REG_RDX]);
 792   st->print("RSP="); print_location(st, uc->uc_mcontext.gregs[REG_RSP]);
 793   st->print("RBP="); print_location(st, uc->uc_mcontext.gregs[REG_RBP]);
 794   st->print("RSI="); print_location(st, uc->uc_mcontext.gregs[REG_RSI]);
 795   st->print("RDI="); print_location(st, uc->uc_mcontext.gregs[REG_RDI]);
 796   st->print("R8 ="); print_location(st, uc->uc_mcontext.gregs[REG_R8]);
 797   st->print("R9 ="); print_location(st, uc->uc_mcontext.gregs[REG_R9]);
 798   st->print("R10="); print_location(st, uc->uc_mcontext.gregs[REG_R10]);
 799   st->print("R11="); print_location(st, uc->uc_mcontext.gregs[REG_R11]);
 800   st->print("R12="); print_location(st, uc->uc_mcontext.gregs[REG_R12]);
 801   st->print("R13="); print_location(st, uc->uc_mcontext.gregs[REG_R13]);
 802   st->print("R14="); print_location(st, uc->uc_mcontext.gregs[REG_R14]);
 803   st->print("R15="); print_location(st, uc->uc_mcontext.gregs[REG_R15]);
 804 #else
 805   st->print("EAX="); print_location(st, uc->uc_mcontext.gregs[REG_EAX]);
 806   st->print("EBX="); print_location(st, uc->uc_mcontext.gregs[REG_EBX]);
 807   st->print("ECX="); print_location(st, uc->uc_mcontext.gregs[REG_ECX]);
 808   st->print("EDX="); print_location(st, uc->uc_mcontext.gregs[REG_EDX]);
 809   st->print("ESP="); print_location(st, uc->uc_mcontext.gregs[REG_ESP]);
 810   st->print("EBP="); print_location(st, uc->uc_mcontext.gregs[REG_EBP]);
 811   st->print("ESI="); print_location(st, uc->uc_mcontext.gregs[REG_ESI]);
 812   st->print("EDI="); print_location(st, uc->uc_mcontext.gregs[REG_EDI]);
 813 #endif // AMD64
 814 
 815   st->cr();
 816 }
 817 
 818 void os::setup_fpu() {
 819 #ifndef AMD64
 820   address fpu_cntrl = StubRoutines::addr_fpu_cntrl_wrd_std();
 821   __asm__ volatile (  "fldcw (%0)" :
 822                       : "r" (fpu_cntrl) : "memory");
 823 #endif // !AMD64
 824 }
 825 
 826 #ifndef PRODUCT
 827 void os::verify_stack_alignment() {
 828 #ifdef AMD64
 829   assert(((intptr_t)os::current_stack_pointer() & (StackAlignmentInBytes-1)) == 0, "incorrect stack alignment");
 830 #endif
 831 }
 832 #endif
 833 
 834 
 835 /*
 836  * IA32 only: execute code at a high address in case buggy NX emulation is present. I.e. avoid CS limit
 837  * updates (JDK-8023956).
 838  */
 839 void os::workaround_expand_exec_shield_cs_limit() {
 840 #if defined(IA32)
 841   size_t page_size = os::vm_page_size();
 842 
 843   /*
 844    * JDK-8197429
 845    *
 846    * Expand the stack mapping to the end of the initial stack before
 847    * attempting to install the codebuf.  This is needed because newer
 848    * Linux kernels impose a distance of a megabyte between stack
 849    * memory and other memory regions.  If we try to install the
 850    * codebuf before expanding the stack the installation will appear
 851    * to succeed but we'll get a segfault later if we expand the stack
 852    * in Java code.
 853    *
 854    */
 855   if (os::is_primordial_thread()) {
 856     address limit = Linux::initial_thread_stack_bottom();
 857     if (! DisablePrimordialThreadGuardPages) {
 858       limit += JavaThread::stack_red_zone_size() +
 859         JavaThread::stack_yellow_zone_size();
 860     }
 861     os::Linux::expand_stack_to(limit);
 862   }
 863 
 864   /*
 865    * Take the highest VA the OS will give us and exec
 866    *
 867    * Although using -(pagesz) as mmap hint works on newer kernel as you would
 868    * think, older variants affected by this work-around don't (search forward only).
 869    *
 870    * On the affected distributions, we understand the memory layout to be:
 871    *
 872    *   TASK_LIMIT= 3G, main stack base close to TASK_LIMT.
 873    *
 874    * A few pages south main stack will do it.
 875    *
 876    * If we are embedded in an app other than launcher (initial != main stack),
 877    * we don't have much control or understanding of the address space, just let it slide.
 878    */
 879   char* hint = (char*)(Linux::initial_thread_stack_bottom() -
 880                        (JavaThread::stack_guard_zone_size() + page_size));
 881   char* codebuf = os::attempt_reserve_memory_at(page_size, hint);
 882 
 883   if (codebuf == NULL) {
 884     // JDK-8197429: There may be a stack gap of one megabyte between
 885     // the limit of the stack and the nearest memory region: this is a
 886     // Linux kernel workaround for CVE-2017-1000364.  If we failed to
 887     // map our codebuf, try again at an address one megabyte lower.
 888     hint -= 1 * M;
 889     codebuf = os::attempt_reserve_memory_at(page_size, hint);
 890   }
 891 
 892   if ((codebuf == NULL) || (!os::commit_memory(codebuf, page_size, true))) {
 893     return; // No matter, we tried, best effort.
 894   }
 895 
 896   MemTracker::record_virtual_memory_type((address)codebuf, mtInternal);
 897 
 898   log_info(os)("[CS limit NX emulation work-around, exec code at: %p]", codebuf);
 899 
 900   // Some code to exec: the 'ret' instruction
 901   codebuf[0] = 0xC3;
 902 
 903   // Call the code in the codebuf
 904   __asm__ volatile("call *%0" : : "r"(codebuf));
 905 
 906   // keep the page mapped so CS limit isn't reduced.
 907 #endif
 908 }
 909 
 910 int os::extra_bang_size_in_bytes() {
 911   // JDK-8050147 requires the full cache line bang for x86.
 912   return VM_Version::L1_line_size();
 913 }