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/frame.inline.hpp"
  42 #include "runtime/interfaceSupport.inline.hpp"
  43 #include "runtime/java.hpp"
  44 #include "runtime/javaCalls.hpp"
  45 #include "runtime/mutexLocker.hpp"
  46 #include "runtime/osThread.hpp"
  47 #include "runtime/safepointMechanism.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   return (address)__builtin_frame_address(0);
  98 }
  99 
 100 char* os::non_memory_address_word() {
 101   // Must never look like an address returned by reserve_memory,
 102   // even in its subfields (as defined by the CPU immediate fields,
 103   // if the CPU splits constants across multiple instructions).
 104 
 105   return (char*) -1;
 106 }
 107 
 108 address os::Linux::ucontext_get_pc(const ucontext_t * uc) {
 109   return (address)uc->uc_mcontext.gregs[REG_PC];
 110 }
 111 
 112 void os::Linux::ucontext_set_pc(ucontext_t * uc, address pc) {
 113   uc->uc_mcontext.gregs[REG_PC] = (intptr_t)pc;
 114 }
 115 
 116 intptr_t* os::Linux::ucontext_get_sp(const ucontext_t * uc) {
 117   return (intptr_t*)uc->uc_mcontext.gregs[REG_SP];
 118 }
 119 
 120 intptr_t* os::Linux::ucontext_get_fp(const ucontext_t * uc) {
 121   return (intptr_t*)uc->uc_mcontext.gregs[REG_FP];
 122 }
 123 
 124 address os::fetch_frame_from_context(const void* ucVoid,
 125                     intptr_t** ret_sp, intptr_t** ret_fp) {
 126 
 127   address epc;
 128   const ucontext_t* uc = (const ucontext_t*)ucVoid;
 129 
 130   if (uc != NULL) {
 131     epc = os::Linux::ucontext_get_pc(uc);
 132     if (ret_sp) *ret_sp = os::Linux::ucontext_get_sp(uc);
 133     if (ret_fp) *ret_fp = os::Linux::ucontext_get_fp(uc);
 134   } else {
 135     epc = NULL;
 136     if (ret_sp) *ret_sp = (intptr_t *)NULL;
 137     if (ret_fp) *ret_fp = (intptr_t *)NULL;
 138   }
 139 
 140   return epc;
 141 }
 142 
 143 frame os::fetch_frame_from_context(const void* ucVoid) {
 144   intptr_t* sp;
 145   intptr_t* fp;
 146   address epc = fetch_frame_from_context(ucVoid, &sp, &fp);
 147   return frame(sp, fp, epc);
 148 }
 149 
 150 bool os::Linux::get_frame_at_stack_banging_point(JavaThread* thread, ucontext_t* uc, frame* fr) {
 151   address pc = (address) os::Linux::ucontext_get_pc(uc);
 152   if (Interpreter::contains(pc)) {
 153     // interpreter performs stack banging after the fixed frame header has
 154     // been generated while the compilers perform it before. To maintain
 155     // semantic consistency between interpreted and compiled frames, the
 156     // method returns the Java sender of the current frame.
 157     *fr = os::fetch_frame_from_context(uc);
 158     if (!fr->is_first_java_frame()) {
 159       // get_frame_at_stack_banging_point() is only called when we
 160       // have well defined stacks so java_sender() calls do not need
 161       // to assert safe_for_sender() first.
 162       *fr = fr->java_sender();
 163     }
 164   } else {
 165     // more complex code with compiled code
 166     assert(!Interpreter::contains(pc), "Interpreted methods should have been handled above");
 167     CodeBlob* cb = CodeCache::find_blob(pc);
 168     if (cb == NULL || !cb->is_nmethod() || cb->is_frame_complete_at(pc)) {
 169       // Not sure where the pc points to, fallback to default
 170       // stack overflow handling
 171       return false;
 172     } else {
 173       // in compiled code, the stack banging is performed just after the return pc
 174       // has been pushed on the stack
 175       intptr_t* fp = os::Linux::ucontext_get_fp(uc);
 176       intptr_t* sp = os::Linux::ucontext_get_sp(uc);
 177       *fr = frame(sp + 1, fp, (address)*sp);
 178       if (!fr->is_java_frame()) {
 179         assert(!fr->is_first_frame(), "Safety check");
 180         // See java_sender() comment above.
 181         *fr = fr->java_sender();
 182       }
 183     }
 184   }
 185   assert(fr->is_java_frame(), "Safety check");
 186   return true;
 187 }
 188 
 189 // By default, gcc always save frame pointer (%ebp/%rbp) on stack. It may get
 190 // turned off by -fomit-frame-pointer,
 191 frame os::get_sender_for_C_frame(frame* fr) {
 192   return frame(fr->sender_sp(), fr->link(), fr->sender_pc());
 193 }
 194 
 195 intptr_t* _get_previous_fp() {
 196 #if defined(__clang__)
 197   intptr_t **ebp;
 198   __asm__ __volatile__ ("mov %%" SPELL_REG_FP ", %0":"=r"(ebp):);
 199 #else
 200   register intptr_t **ebp __asm__ (SPELL_REG_FP);
 201 #endif
 202   // ebp is for this frame (_get_previous_fp). We want the ebp for the
 203   // caller of os::current_frame*(), so go up two frames. However, for
 204   // optimized builds, _get_previous_fp() will be inlined, so only go
 205   // up 1 frame in that case.
 206 #ifdef _NMT_NOINLINE_
 207   return **(intptr_t***)ebp;
 208 #else
 209   return *ebp;
 210 #endif
 211 }
 212 
 213 
 214 frame os::current_frame() {
 215   intptr_t* fp = _get_previous_fp();
 216   frame myframe((intptr_t*)os::current_stack_pointer(),
 217                 (intptr_t*)fp,
 218                 CAST_FROM_FN_PTR(address, os::current_frame));
 219   if (os::is_first_C_frame(&myframe)) {
 220     // stack is not walkable
 221     return frame();
 222   } else {
 223     return os::get_sender_for_C_frame(&myframe);
 224   }
 225 }
 226 
 227 // Utility functions
 228 
 229 // From IA32 System Programming Guide
 230 enum {
 231   trap_page_fault = 0xE
 232 };
 233 
 234 extern "C" JNIEXPORT int
 235 JVM_handle_linux_signal(int sig,
 236                         siginfo_t* info,
 237                         void* ucVoid,
 238                         int abort_if_unrecognized) {
 239   ucontext_t* uc = (ucontext_t*) ucVoid;
 240 
 241   Thread* t = Thread::current_or_null_safe();
 242 
 243   // Must do this before SignalHandlerMark, if crash protection installed we will longjmp away
 244   // (no destructors can be run)
 245   os::ThreadCrashProtection::check_crash_protection(sig, t);
 246 
 247   SignalHandlerMark shm(t);
 248 
 249   // Note: it's not uncommon that JNI code uses signal/sigset to install
 250   // then restore certain signal handler (e.g. to temporarily block SIGPIPE,
 251   // or have a SIGILL handler when detecting CPU type). When that happens,
 252   // JVM_handle_linux_signal() might be invoked with junk info/ucVoid. To
 253   // avoid unnecessary crash when libjsig is not preloaded, try handle signals
 254   // that do not require siginfo/ucontext first.
 255 
 256   if (sig == SIGPIPE || sig == SIGXFSZ) {
 257     // allow chained handler to go first
 258     if (os::Linux::chained_handler(sig, info, ucVoid)) {
 259       return true;
 260     } else {
 261       // Ignoring SIGPIPE/SIGXFSZ - see bugs 4229104 or 6499219
 262       return true;
 263     }
 264   }
 265 
 266 #ifdef CAN_SHOW_REGISTERS_ON_ASSERT
 267   if ((sig == SIGSEGV || sig == SIGBUS) && info != NULL && info->si_addr == g_assert_poison) {
 268     if (handle_assert_poison_fault(ucVoid, info->si_addr)) {
 269       return 1;
 270     }
 271   }
 272 #endif
 273 
 274   JavaThread* thread = NULL;
 275   VMThread* vmthread = NULL;
 276   if (os::Linux::signal_handlers_are_installed) {
 277     if (t != NULL ){
 278       if(t->is_Java_thread()) {
 279         thread = (JavaThread*)t;
 280       }
 281       else if(t->is_VM_thread()){
 282         vmthread = (VMThread *)t;
 283       }
 284     }
 285   }
 286 /*
 287   NOTE: does not seem to work on linux.
 288   if (info == NULL || info->si_code <= 0 || info->si_code == SI_NOINFO) {
 289     // can't decode this kind of signal
 290     info = NULL;
 291   } else {
 292     assert(sig == info->si_signo, "bad siginfo");
 293   }
 294 */
 295   // decide if this trap can be handled by a stub
 296   address stub = NULL;
 297 
 298   address pc          = NULL;
 299 
 300   //%note os_trap_1
 301   if (info != NULL && uc != NULL && thread != NULL) {
 302     pc = (address) os::Linux::ucontext_get_pc(uc);
 303 
 304     if (StubRoutines::is_safefetch_fault(pc)) {
 305       os::Linux::ucontext_set_pc(uc, StubRoutines::continuation_for_safefetch_fault(pc));
 306       return 1;
 307     }
 308 
 309 #ifndef AMD64
 310     // Halt if SI_KERNEL before more crashes get misdiagnosed as Java bugs
 311     // This can happen in any running code (currently more frequently in
 312     // interpreter code but has been seen in compiled code)
 313     if (sig == SIGSEGV && info->si_addr == 0 && info->si_code == SI_KERNEL) {
 314       fatal("An irrecoverable SI_KERNEL SIGSEGV has occurred due "
 315             "to unstable signal handling in this distribution.");
 316     }
 317 #endif // AMD64
 318 
 319     // Handle ALL stack overflow variations here
 320     if (sig == SIGSEGV) {
 321       address addr = (address) info->si_addr;
 322 
 323       // check if fault address is within thread stack
 324       if (thread->is_in_full_stack(addr)) {
 325         // stack overflow
 326         if (thread->in_stack_yellow_reserved_zone(addr)) {
 327           if (thread->thread_state() == _thread_in_Java) {
 328             if (thread->in_stack_reserved_zone(addr)) {
 329               frame fr;
 330               if (os::Linux::get_frame_at_stack_banging_point(thread, uc, &fr)) {
 331                 assert(fr.is_java_frame(), "Must be a Java frame");
 332                 frame activation =
 333                   SharedRuntime::look_for_reserved_stack_annotated_method(thread, fr);
 334                 if (activation.sp() != NULL) {
 335                   thread->disable_stack_reserved_zone();
 336                   if (activation.is_interpreted_frame()) {
 337                     thread->set_reserved_stack_activation((address)(
 338                       activation.fp() + frame::interpreter_frame_initial_sp_offset));
 339                   } else {
 340                     thread->set_reserved_stack_activation((address)activation.unextended_sp());
 341                   }
 342                   return 1;
 343                 }
 344               }
 345             }
 346             // Throw a stack overflow exception.  Guard pages will be reenabled
 347             // while unwinding the stack.
 348             thread->disable_stack_yellow_reserved_zone();
 349             stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::STACK_OVERFLOW);
 350           } else {
 351             // Thread was in the vm or native code.  Return and try to finish.
 352             thread->disable_stack_yellow_reserved_zone();
 353             return 1;
 354           }
 355         } else if (thread->in_stack_red_zone(addr)) {
 356           // Fatal red zone violation.  Disable the guard pages and fall through
 357           // to handle_unexpected_exception way down below.
 358           thread->disable_stack_red_zone();
 359           tty->print_raw_cr("An irrecoverable stack overflow has occurred.");
 360 
 361           // This is a likely cause, but hard to verify. Let's just print
 362           // it as a hint.
 363           tty->print_raw_cr("Please check if any of your loaded .so files has "
 364                             "enabled executable stack (see man page execstack(8))");
 365         } else {
 366           // Accessing stack address below sp may cause SEGV if current
 367           // thread has MAP_GROWSDOWN stack. This should only happen when
 368           // current thread was created by user code with MAP_GROWSDOWN flag
 369           // and then attached to VM. See notes in os_linux.cpp.
 370           if (thread->osthread()->expanding_stack() == 0) {
 371              thread->osthread()->set_expanding_stack();
 372              if (os::Linux::manually_expand_stack(thread, addr)) {
 373                thread->osthread()->clear_expanding_stack();
 374                return 1;
 375              }
 376              thread->osthread()->clear_expanding_stack();
 377           } else {
 378              fatal("recursive segv. expanding stack.");
 379           }
 380         }
 381       }
 382     }
 383 
 384     if ((sig == SIGSEGV) && VM_Version::is_cpuinfo_segv_addr(pc)) {
 385       // Verify that OS save/restore AVX registers.
 386       stub = VM_Version::cpuinfo_cont_addr();
 387     }
 388 
 389     if (thread->thread_state() == _thread_in_Java) {
 390       // Java thread running in Java code => find exception handler if any
 391       // a fault inside compiled code, the interpreter, or a stub
 392 
 393       if (sig == SIGSEGV && SafepointMechanism::is_poll_address((address)info->si_addr)) {
 394         stub = SharedRuntime::get_poll_stub(pc);
 395       } else if (sig == SIGBUS /* && info->si_code == BUS_OBJERR */) {
 396         // BugId 4454115: A read from a MappedByteBuffer can fault
 397         // here if the underlying file has been truncated.
 398         // Do not crash the VM in such a case.
 399         CodeBlob* cb = CodeCache::find_blob_unsafe(pc);
 400         CompiledMethod* nm = (cb != NULL) ? cb->as_compiled_method_or_null() : NULL;
 401         bool is_unsafe_arraycopy = thread->doing_unsafe_access() && UnsafeCopyMemory::contains_pc(pc);
 402         if ((nm != NULL && nm->has_unsafe_access()) || is_unsafe_arraycopy) {
 403           address next_pc = Assembler::locate_next_instruction(pc);
 404           if (is_unsafe_arraycopy) {
 405             next_pc = UnsafeCopyMemory::page_error_continue_pc(pc);
 406           }
 407           stub = SharedRuntime::handle_unsafe_access(thread, next_pc);
 408         }
 409       }
 410       else
 411 
 412 #ifdef AMD64
 413       if (sig == SIGFPE  &&
 414           (info->si_code == FPE_INTDIV || info->si_code == FPE_FLTDIV)) {
 415         stub =
 416           SharedRuntime::
 417           continuation_for_implicit_exception(thread,
 418                                               pc,
 419                                               SharedRuntime::
 420                                               IMPLICIT_DIVIDE_BY_ZERO);
 421 #else
 422       if (sig == SIGFPE /* && info->si_code == FPE_INTDIV */) {
 423         // HACK: si_code does not work on linux 2.2.12-20!!!
 424         int op = pc[0];
 425         if (op == 0xDB) {
 426           // FIST
 427           // TODO: The encoding of D2I in i486.ad can cause an exception
 428           // prior to the fist instruction if there was an invalid operation
 429           // pending. We want to dismiss that exception. From the win_32
 430           // side it also seems that if it really was the fist causing
 431           // the exception that we do the d2i by hand with different
 432           // rounding. Seems kind of weird.
 433           // NOTE: that we take the exception at the NEXT floating point instruction.
 434           assert(pc[0] == 0xDB, "not a FIST opcode");
 435           assert(pc[1] == 0x14, "not a FIST opcode");
 436           assert(pc[2] == 0x24, "not a FIST opcode");
 437           return true;
 438         } else if (op == 0xF7) {
 439           // IDIV
 440           stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_DIVIDE_BY_ZERO);
 441         } else {
 442           // TODO: handle more cases if we are using other x86 instructions
 443           //   that can generate SIGFPE signal on linux.
 444           tty->print_cr("unknown opcode 0x%X with SIGFPE.", op);
 445           fatal("please update this code.");
 446         }
 447 #endif // AMD64
 448       } else if (sig == SIGSEGV &&
 449                  MacroAssembler::uses_implicit_null_check(info->si_addr)) {
 450           // Determination of interpreter/vtable stub/compiled code null exception
 451           stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_NULL);
 452       }
 453     } else if ((thread->thread_state() == _thread_in_vm ||
 454                 thread->thread_state() == _thread_in_native) &&
 455                (sig == SIGBUS && /* info->si_code == BUS_OBJERR && */
 456                thread->doing_unsafe_access())) {
 457         address next_pc = Assembler::locate_next_instruction(pc);
 458         if (UnsafeCopyMemory::contains_pc(pc)) {
 459           next_pc = UnsafeCopyMemory::page_error_continue_pc(pc);
 460         }
 461         stub = SharedRuntime::handle_unsafe_access(thread, next_pc);
 462     }
 463 
 464     // jni_fast_Get<Primitive>Field can trap at certain pc's if a GC kicks in
 465     // and the heap gets shrunk before the field access.
 466     if ((sig == SIGSEGV) || (sig == SIGBUS)) {
 467       address addr = JNI_FastGetField::find_slowcase_pc(pc);
 468       if (addr != (address)-1) {
 469         stub = addr;
 470       }
 471     }
 472   }
 473 
 474 #ifndef AMD64
 475   // Execution protection violation
 476   //
 477   // This should be kept as the last step in the triage.  We don't
 478   // have a dedicated trap number for a no-execute fault, so be
 479   // conservative and allow other handlers the first shot.
 480   //
 481   // Note: We don't test that info->si_code == SEGV_ACCERR here.
 482   // this si_code is so generic that it is almost meaningless; and
 483   // the si_code for this condition may change in the future.
 484   // Furthermore, a false-positive should be harmless.
 485   if (UnguardOnExecutionViolation > 0 &&
 486       (sig == SIGSEGV || sig == SIGBUS) &&
 487       uc->uc_mcontext.gregs[REG_TRAPNO] == trap_page_fault) {
 488     int page_size = os::vm_page_size();
 489     address addr = (address) info->si_addr;
 490     address pc = os::Linux::ucontext_get_pc(uc);
 491     // Make sure the pc and the faulting address are sane.
 492     //
 493     // If an instruction spans a page boundary, and the page containing
 494     // the beginning of the instruction is executable but the following
 495     // page is not, the pc and the faulting address might be slightly
 496     // different - we still want to unguard the 2nd page in this case.
 497     //
 498     // 15 bytes seems to be a (very) safe value for max instruction size.
 499     bool pc_is_near_addr =
 500       (pointer_delta((void*) addr, (void*) pc, sizeof(char)) < 15);
 501     bool instr_spans_page_boundary =
 502       (align_down((intptr_t) pc ^ (intptr_t) addr,
 503                        (intptr_t) page_size) > 0);
 504 
 505     if (pc == addr || (pc_is_near_addr && instr_spans_page_boundary)) {
 506       static volatile address last_addr =
 507         (address) os::non_memory_address_word();
 508 
 509       // In conservative mode, don't unguard unless the address is in the VM
 510       if (addr != last_addr &&
 511           (UnguardOnExecutionViolation > 1 || os::address_is_in_vm(addr))) {
 512 
 513         // Set memory to RWX and retry
 514         address page_start = align_down(addr, page_size);
 515         bool res = os::protect_memory((char*) page_start, page_size,
 516                                       os::MEM_PROT_RWX);
 517 
 518         log_debug(os)("Execution protection violation "
 519                       "at " INTPTR_FORMAT
 520                       ", unguarding " INTPTR_FORMAT ": %s, errno=%d", p2i(addr),
 521                       p2i(page_start), (res ? "success" : "failed"), errno);
 522         stub = pc;
 523 
 524         // Set last_addr so if we fault again at the same address, we don't end
 525         // up in an endless loop.
 526         //
 527         // There are two potential complications here.  Two threads trapping at
 528         // the same address at the same time could cause one of the threads to
 529         // think it already unguarded, and abort the VM.  Likely very rare.
 530         //
 531         // The other race involves two threads alternately trapping at
 532         // different addresses and failing to unguard the page, resulting in
 533         // an endless loop.  This condition is probably even more unlikely than
 534         // the first.
 535         //
 536         // Although both cases could be avoided by using locks or thread local
 537         // last_addr, these solutions are unnecessary complication: this
 538         // handler is a best-effort safety net, not a complete solution.  It is
 539         // disabled by default and should only be used as a workaround in case
 540         // we missed any no-execute-unsafe VM code.
 541 
 542         last_addr = addr;
 543       }
 544     }
 545   }
 546 #endif // !AMD64
 547 
 548   if (stub != NULL) {
 549     // save all thread context in case we need to restore it
 550     if (thread != NULL) thread->set_saved_exception_pc(pc);
 551 
 552     os::Linux::ucontext_set_pc(uc, stub);
 553     return true;
 554   }
 555 
 556   // signal-chaining
 557   if (os::Linux::chained_handler(sig, info, ucVoid)) {
 558      return true;
 559   }
 560 
 561   if (!abort_if_unrecognized) {
 562     // caller wants another chance, so give it to him
 563     return false;
 564   }
 565 
 566   if (pc == NULL && uc != NULL) {
 567     pc = os::Linux::ucontext_get_pc(uc);
 568   }
 569 
 570   // unmask current signal
 571   sigset_t newset;
 572   sigemptyset(&newset);
 573   sigaddset(&newset, sig);
 574   sigprocmask(SIG_UNBLOCK, &newset, NULL);
 575 
 576   VMError::report_and_die(t, sig, pc, info, ucVoid);
 577 
 578   ShouldNotReachHere();
 579   return true; // Mute compiler
 580 }
 581 
 582 void os::Linux::init_thread_fpu_state(void) {
 583 #ifndef AMD64
 584   // set fpu to 53 bit precision
 585   set_fpu_control_word(0x27f);
 586 #endif // !AMD64
 587 }
 588 
 589 int os::Linux::get_fpu_control_word(void) {
 590 #ifdef AMD64
 591   return 0;
 592 #else
 593   int fpu_control;
 594   _FPU_GETCW(fpu_control);
 595   return fpu_control & 0xffff;
 596 #endif // AMD64
 597 }
 598 
 599 void os::Linux::set_fpu_control_word(int fpu_control) {
 600 #ifndef AMD64
 601   _FPU_SETCW(fpu_control);
 602 #endif // !AMD64
 603 }
 604 
 605 // Check that the linux kernel version is 2.4 or higher since earlier
 606 // versions do not support SSE without patches.
 607 bool os::supports_sse() {
 608 #ifdef AMD64
 609   return true;
 610 #else
 611   struct utsname uts;
 612   if( uname(&uts) != 0 ) return false; // uname fails?
 613   char *minor_string;
 614   int major = strtol(uts.release,&minor_string,10);
 615   int minor = strtol(minor_string+1,NULL,10);
 616   bool result = (major > 2 || (major==2 && minor >= 4));
 617   log_info(os)("OS version is %d.%d, which %s support SSE/SSE2",
 618                major,minor, result ? "DOES" : "does NOT");
 619   return result;
 620 #endif // AMD64
 621 }
 622 




















 623 bool os::is_allocatable(size_t bytes) {
 624 #ifdef AMD64
 625   // unused on amd64?
 626   return true;
 627 #else
 628 
 629   if (bytes < 2 * G) {
 630     return true;
 631   }
 632 
 633   char* addr = reserve_memory(bytes, NULL);
 634 
 635   if (addr != NULL) {
 636     release_memory(addr, bytes);
 637   }
 638 
 639   return addr != NULL;
 640 #endif // AMD64
 641 }
 642 
 643 ////////////////////////////////////////////////////////////////////////////////
 644 // thread stack
 645 
 646 // Minimum usable stack sizes required to get to user code. Space for
 647 // HotSpot guard pages is added later.
 648 size_t os::Posix::_compiler_thread_min_stack_allowed = 48 * K;
 649 size_t os::Posix::_java_thread_min_stack_allowed = 40 * K;
 650 #ifdef _LP64
 651 size_t os::Posix::_vm_internal_thread_min_stack_allowed = 64 * K;
 652 #else
 653 size_t os::Posix::_vm_internal_thread_min_stack_allowed = (48 DEBUG_ONLY(+ 4)) * K;
 654 #endif // _LP64
 655 
 656 // return default stack size for thr_type
 657 size_t os::Posix::default_stack_size(os::ThreadType thr_type) {
 658   // default stack size (compiler thread needs larger stack)
 659 #ifdef AMD64
 660   size_t s = (thr_type == os::compiler_thread ? 4 * M : 1 * M);
 661 #else
 662   size_t s = (thr_type == os::compiler_thread ? 2 * M : 512 * K);
 663 #endif // AMD64
 664   return s;
 665 }
 666 
 667 /////////////////////////////////////////////////////////////////////////////
 668 // helper functions for fatal error handler
 669 
 670 void os::print_context(outputStream *st, const void *context) {
 671   if (context == NULL) return;
 672 
 673   const ucontext_t *uc = (const ucontext_t*)context;
 674   st->print_cr("Registers:");
 675 #ifdef AMD64
 676   st->print(  "RAX=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RAX]);
 677   st->print(", RBX=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RBX]);
 678   st->print(", RCX=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RCX]);
 679   st->print(", RDX=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RDX]);
 680   st->cr();
 681   st->print(  "RSP=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RSP]);
 682   st->print(", RBP=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RBP]);
 683   st->print(", RSI=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RSI]);
 684   st->print(", RDI=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RDI]);
 685   st->cr();
 686   st->print(  "R8 =" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R8]);
 687   st->print(", R9 =" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R9]);
 688   st->print(", R10=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R10]);
 689   st->print(", R11=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R11]);
 690   st->cr();
 691   st->print(  "R12=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R12]);
 692   st->print(", R13=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R13]);
 693   st->print(", R14=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R14]);
 694   st->print(", R15=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_R15]);
 695   st->cr();
 696   st->print(  "RIP=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_RIP]);
 697   st->print(", EFLAGS=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_EFL]);
 698   st->print(", CSGSFS=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_CSGSFS]);
 699   st->print(", ERR=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_ERR]);
 700   st->cr();
 701   st->print("  TRAPNO=" INTPTR_FORMAT, (intptr_t)uc->uc_mcontext.gregs[REG_TRAPNO]);
 702 #else
 703   st->print(  "EAX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EAX]);
 704   st->print(", EBX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EBX]);
 705   st->print(", ECX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_ECX]);
 706   st->print(", EDX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EDX]);
 707   st->cr();
 708   st->print(  "ESP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_UESP]);
 709   st->print(", EBP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EBP]);
 710   st->print(", ESI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_ESI]);
 711   st->print(", EDI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EDI]);
 712   st->cr();
 713   st->print(  "EIP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EIP]);
 714   st->print(", EFLAGS=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EFL]);
 715   st->print(", CR2=" PTR64_FORMAT, (uint64_t)uc->uc_mcontext.cr2);
 716 #endif // AMD64
 717   st->cr();
 718   st->cr();
 719 
 720   intptr_t *sp = (intptr_t *)os::Linux::ucontext_get_sp(uc);
 721   st->print_cr("Top of Stack: (sp=" PTR_FORMAT ")", p2i(sp));
 722   print_hex_dump(st, (address)sp, (address)(sp + 8), sizeof(intptr_t));
 723   st->cr();
 724 
 725   // Note: it may be unsafe to inspect memory near pc. For example, pc may
 726   // point to garbage if entry point in an nmethod is corrupted. Leave
 727   // this at the end, and hope for the best.
 728   address pc = os::Linux::ucontext_get_pc(uc);
 729   print_instructions(st, pc, sizeof(char));
 730   st->cr();
 731 }
 732 
 733 void os::print_register_info(outputStream *st, const void *context) {
 734   if (context == NULL) return;
 735 
 736   const ucontext_t *uc = (const ucontext_t*)context;
 737 
 738   st->print_cr("Register to memory mapping:");
 739   st->cr();
 740 
 741   // this is horrendously verbose but the layout of the registers in the
 742   // context does not match how we defined our abstract Register set, so
 743   // we can't just iterate through the gregs area
 744 
 745   // this is only for the "general purpose" registers
 746 
 747 #ifdef AMD64
 748   st->print("RAX="); print_location(st, uc->uc_mcontext.gregs[REG_RAX]);
 749   st->print("RBX="); print_location(st, uc->uc_mcontext.gregs[REG_RBX]);
 750   st->print("RCX="); print_location(st, uc->uc_mcontext.gregs[REG_RCX]);
 751   st->print("RDX="); print_location(st, uc->uc_mcontext.gregs[REG_RDX]);
 752   st->print("RSP="); print_location(st, uc->uc_mcontext.gregs[REG_RSP]);
 753   st->print("RBP="); print_location(st, uc->uc_mcontext.gregs[REG_RBP]);
 754   st->print("RSI="); print_location(st, uc->uc_mcontext.gregs[REG_RSI]);
 755   st->print("RDI="); print_location(st, uc->uc_mcontext.gregs[REG_RDI]);
 756   st->print("R8 ="); print_location(st, uc->uc_mcontext.gregs[REG_R8]);
 757   st->print("R9 ="); print_location(st, uc->uc_mcontext.gregs[REG_R9]);
 758   st->print("R10="); print_location(st, uc->uc_mcontext.gregs[REG_R10]);
 759   st->print("R11="); print_location(st, uc->uc_mcontext.gregs[REG_R11]);
 760   st->print("R12="); print_location(st, uc->uc_mcontext.gregs[REG_R12]);
 761   st->print("R13="); print_location(st, uc->uc_mcontext.gregs[REG_R13]);
 762   st->print("R14="); print_location(st, uc->uc_mcontext.gregs[REG_R14]);
 763   st->print("R15="); print_location(st, uc->uc_mcontext.gregs[REG_R15]);
 764 #else
 765   st->print("EAX="); print_location(st, uc->uc_mcontext.gregs[REG_EAX]);
 766   st->print("EBX="); print_location(st, uc->uc_mcontext.gregs[REG_EBX]);
 767   st->print("ECX="); print_location(st, uc->uc_mcontext.gregs[REG_ECX]);
 768   st->print("EDX="); print_location(st, uc->uc_mcontext.gregs[REG_EDX]);
 769   st->print("ESP="); print_location(st, uc->uc_mcontext.gregs[REG_ESP]);
 770   st->print("EBP="); print_location(st, uc->uc_mcontext.gregs[REG_EBP]);
 771   st->print("ESI="); print_location(st, uc->uc_mcontext.gregs[REG_ESI]);
 772   st->print("EDI="); print_location(st, uc->uc_mcontext.gregs[REG_EDI]);
 773 #endif // AMD64
 774 
 775   st->cr();
 776 }
 777 
 778 void os::setup_fpu() {
 779 #ifndef AMD64
 780   address fpu_cntrl = StubRoutines::addr_fpu_cntrl_wrd_std();
 781   __asm__ volatile (  "fldcw (%0)" :
 782                       : "r" (fpu_cntrl) : "memory");
 783 #endif // !AMD64
 784 }
 785 
 786 #ifndef PRODUCT
 787 void os::verify_stack_alignment() {
 788 #ifdef AMD64
 789   assert(((intptr_t)os::current_stack_pointer() & (StackAlignmentInBytes-1)) == 0, "incorrect stack alignment");
 790 #endif
 791 }
 792 #endif
 793 
 794 
 795 /*
 796  * IA32 only: execute code at a high address in case buggy NX emulation is present. I.e. avoid CS limit
 797  * updates (JDK-8023956).
 798  */
 799 void os::workaround_expand_exec_shield_cs_limit() {
 800 #if defined(IA32)
 801   assert(Linux::initial_thread_stack_bottom() != NULL, "sanity");
 802   size_t page_size = os::vm_page_size();
 803 
 804   /*
 805    * JDK-8197429
 806    *
 807    * Expand the stack mapping to the end of the initial stack before
 808    * attempting to install the codebuf.  This is needed because newer
 809    * Linux kernels impose a distance of a megabyte between stack
 810    * memory and other memory regions.  If we try to install the
 811    * codebuf before expanding the stack the installation will appear
 812    * to succeed but we'll get a segfault later if we expand the stack
 813    * in Java code.
 814    *
 815    */
 816   if (os::is_primordial_thread()) {
 817     address limit = Linux::initial_thread_stack_bottom();
 818     if (! DisablePrimordialThreadGuardPages) {
 819       limit += JavaThread::stack_red_zone_size() +
 820         JavaThread::stack_yellow_zone_size();
 821     }
 822     os::Linux::expand_stack_to(limit);
 823   }
 824 
 825   /*
 826    * Take the highest VA the OS will give us and exec
 827    *
 828    * Although using -(pagesz) as mmap hint works on newer kernel as you would
 829    * think, older variants affected by this work-around don't (search forward only).
 830    *
 831    * On the affected distributions, we understand the memory layout to be:
 832    *
 833    *   TASK_LIMIT= 3G, main stack base close to TASK_LIMT.
 834    *
 835    * A few pages south main stack will do it.
 836    *
 837    * If we are embedded in an app other than launcher (initial != main stack),
 838    * we don't have much control or understanding of the address space, just let it slide.
 839    */
 840   char* hint = (char*)(Linux::initial_thread_stack_bottom() -
 841                        (JavaThread::stack_guard_zone_size() + page_size));
 842   char* codebuf = os::attempt_reserve_memory_at(page_size, hint);
 843 
 844   if (codebuf == NULL) {
 845     // JDK-8197429: There may be a stack gap of one megabyte between
 846     // the limit of the stack and the nearest memory region: this is a
 847     // Linux kernel workaround for CVE-2017-1000364.  If we failed to
 848     // map our codebuf, try again at an address one megabyte lower.
 849     hint -= 1 * M;
 850     codebuf = os::attempt_reserve_memory_at(page_size, hint);
 851   }
 852 
 853   if ((codebuf == NULL) || (!os::commit_memory(codebuf, page_size, true))) {
 854     return; // No matter, we tried, best effort.
 855   }
 856 
 857   MemTracker::record_virtual_memory_type((address)codebuf, mtInternal);
 858 
 859   log_info(os)("[CS limit NX emulation work-around, exec code at: %p]", codebuf);
 860 
 861   // Some code to exec: the 'ret' instruction
 862   codebuf[0] = 0xC3;
 863 
 864   // Call the code in the codebuf
 865   __asm__ volatile("call *%0" : : "r"(codebuf));
 866 
 867   // keep the page mapped so CS limit isn't reduced.
 868 #endif
 869 }
 870 
 871 int os::extra_bang_size_in_bytes() {
 872   // JDK-8050147 requires the full cache line bang for x86.
 873   return VM_Version::L1_line_size();
 874 }
--- EOF ---