1 /*
   2  * Copyright (c) 1999, 2014, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 // no precompiled headers
  26 #include "asm/macroAssembler.hpp"
  27 #include "classfile/classLoader.hpp"
  28 #include "classfile/systemDictionary.hpp"
  29 #include "classfile/vmSymbols.hpp"
  30 #include "code/icBuffer.hpp"
  31 #include "code/vtableStubs.hpp"
  32 #include "interpreter/interpreter.hpp"
  33 #include "jvm_linux.h"
  34 #include "memory/allocation.inline.hpp"
  35 #include "mutex_linux.inline.hpp"
  36 #include "os_share_linux.hpp"
  37 #include "prims/jniFastGetField.hpp"
  38 #include "prims/jvm.h"
  39 #include "prims/jvm_misc.hpp"
  40 #include "runtime/arguments.hpp"
  41 #include "runtime/extendedPC.hpp"
  42 #include "runtime/frame.inline.hpp"
  43 #include "runtime/interfaceSupport.hpp"
  44 #include "runtime/java.hpp"
  45 #include "runtime/javaCalls.hpp"
  46 #include "runtime/mutexLocker.hpp"
  47 #include "runtime/osThread.hpp"
  48 #include "runtime/sharedRuntime.hpp"
  49 #include "runtime/stubRoutines.hpp"
  50 #include "runtime/thread.inline.hpp"
  51 #include "runtime/timer.hpp"
  52 #include "services/memTracker.hpp"
  53 #include "utilities/events.hpp"
  54 #include "utilities/vmError.hpp"
  55 
  56 // put OS-includes here
  57 # include <sys/types.h>
  58 # include <sys/mman.h>
  59 # include <pthread.h>
  60 # include <signal.h>
  61 # include <errno.h>
  62 # include <dlfcn.h>
  63 # include <stdlib.h>
  64 # include <stdio.h>
  65 # include <unistd.h>
  66 # include <sys/resource.h>
  67 # include <pthread.h>
  68 # include <sys/stat.h>
  69 # include <sys/time.h>
  70 # include <sys/utsname.h>
  71 # include <sys/socket.h>
  72 # include <sys/wait.h>
  73 # include <pwd.h>
  74 # include <poll.h>
  75 # include <ucontext.h>
  76 # include <fpu_control.h>
  77 
  78 #ifdef AMD64
  79 #define REG_SP REG_RSP
  80 #define REG_PC REG_RIP
  81 #define REG_FP REG_RBP
  82 #define SPELL_REG_SP "rsp"
  83 #define SPELL_REG_FP "rbp"
  84 #else
  85 #define REG_SP REG_UESP
  86 #define REG_PC REG_EIP
  87 #define REG_FP REG_EBP
  88 #define SPELL_REG_SP "esp"
  89 #define SPELL_REG_FP "ebp"
  90 #endif // AMD64
  91 
  92 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
  93 
  94 address os::current_stack_pointer() {
  95 #ifdef SPARC_WORKS
  96   register void *esp;
  97   __asm__("mov %%"SPELL_REG_SP", %0":"=r"(esp));
  98   return (address) ((char*)esp + sizeof(long)*2);
  99 #elif defined(__clang__)
 100   intptr_t* esp;
 101   __asm__ __volatile__ ("mov %%"SPELL_REG_SP", %0":"=r"(esp):);
 102   return (address) esp;
 103 #else
 104   register void *esp __asm__ (SPELL_REG_SP);
 105   return (address) esp;
 106 #endif
 107 }
 108 
 109 char* os::non_memory_address_word() {
 110   // Must never look like an address returned by reserve_memory,
 111   // even in its subfields (as defined by the CPU immediate fields,
 112   // if the CPU splits constants across multiple instructions).
 113 
 114   return (char*) -1;
 115 }
 116 
 117 void os::initialize_thread(Thread* thr) {
 118 // Nothing to do.
 119 }
 120 
 121 address os::Linux::ucontext_get_pc(ucontext_t * uc) {
 122   return (address)uc->uc_mcontext.gregs[REG_PC];
 123 }
 124 
 125 intptr_t* os::Linux::ucontext_get_sp(ucontext_t * uc) {
 126   return (intptr_t*)uc->uc_mcontext.gregs[REG_SP];
 127 }
 128 
 129 intptr_t* os::Linux::ucontext_get_fp(ucontext_t * uc) {
 130   return (intptr_t*)uc->uc_mcontext.gregs[REG_FP];
 131 }
 132 
 133 // For Forte Analyzer AsyncGetCallTrace profiling support - thread
 134 // is currently interrupted by SIGPROF.
 135 // os::Solaris::fetch_frame_from_ucontext() tries to skip nested signal
 136 // frames. Currently we don't do that on Linux, so it's the same as
 137 // os::fetch_frame_from_context().
 138 ExtendedPC os::Linux::fetch_frame_from_ucontext(Thread* thread,
 139   ucontext_t* uc, intptr_t** ret_sp, intptr_t** ret_fp) {
 140 
 141   assert(thread != NULL, "just checking");
 142   assert(ret_sp != NULL, "just checking");
 143   assert(ret_fp != NULL, "just checking");
 144 
 145   return os::fetch_frame_from_context(uc, ret_sp, ret_fp);
 146 }
 147 
 148 ExtendedPC os::fetch_frame_from_context(void* ucVoid,
 149                     intptr_t** ret_sp, intptr_t** ret_fp) {
 150 
 151   ExtendedPC  epc;
 152   ucontext_t* uc = (ucontext_t*)ucVoid;
 153 
 154   if (uc != NULL) {
 155     epc = ExtendedPC(os::Linux::ucontext_get_pc(uc));
 156     if (ret_sp) *ret_sp = os::Linux::ucontext_get_sp(uc);
 157     if (ret_fp) *ret_fp = os::Linux::ucontext_get_fp(uc);
 158   } else {
 159     // construct empty ExtendedPC for return value checking
 160     epc = ExtendedPC(NULL);
 161     if (ret_sp) *ret_sp = (intptr_t *)NULL;
 162     if (ret_fp) *ret_fp = (intptr_t *)NULL;
 163   }
 164 
 165   return epc;
 166 }
 167 
 168 frame os::fetch_frame_from_context(void* ucVoid) {
 169   intptr_t* sp;
 170   intptr_t* fp;
 171   ExtendedPC epc = fetch_frame_from_context(ucVoid, &sp, &fp);
 172   return frame(sp, fp, epc.pc());
 173 }
 174 
 175 // By default, gcc always save frame pointer (%ebp/%rbp) on stack. It may get
 176 // turned off by -fomit-frame-pointer,
 177 frame os::get_sender_for_C_frame(frame* fr) {
 178   return frame(fr->sender_sp(), fr->link(), fr->sender_pc());
 179 }
 180 
 181 intptr_t* _get_previous_fp() {
 182 #ifdef SPARC_WORKS
 183   register intptr_t **ebp;
 184   __asm__("mov %%"SPELL_REG_FP", %0":"=r"(ebp));
 185 #elif defined(__clang__)
 186   intptr_t **ebp;
 187   __asm__ __volatile__ ("mov %%"SPELL_REG_FP", %0":"=r"(ebp):);
 188 #else
 189   register intptr_t **ebp __asm__ (SPELL_REG_FP);
 190 #endif
 191   return (intptr_t*) *ebp;   // we want what it points to.
 192 }
 193 
 194 
 195 frame os::current_frame() {
 196   intptr_t* fp = _get_previous_fp();
 197   frame myframe((intptr_t*)os::current_stack_pointer(),
 198                 (intptr_t*)fp,
 199                 CAST_FROM_FN_PTR(address, os::current_frame));
 200   if (os::is_first_C_frame(&myframe)) {
 201     // stack is not walkable
 202     return frame();
 203   } else {
 204     return os::get_sender_for_C_frame(&myframe);
 205   }
 206 }
 207 
 208 // Utility functions
 209 
 210 // From IA32 System Programming Guide
 211 enum {
 212   trap_page_fault = 0xE
 213 };
 214 
 215 extern "C" JNIEXPORT int
 216 JVM_handle_linux_signal(int sig,
 217                         siginfo_t* info,
 218                         void* ucVoid,
 219                         int abort_if_unrecognized) {
 220   ucontext_t* uc = (ucontext_t*) ucVoid;
 221 
 222   Thread* t = ThreadLocalStorage::get_thread_slow();
 223 
 224   // Must do this before SignalHandlerMark, if crash protection installed we will longjmp away
 225   // (no destructors can be run)
 226   os::WatcherThreadCrashProtection::check_crash_protection(sig, t);
 227 
 228   SignalHandlerMark shm(t);
 229 
 230   // Note: it's not uncommon that JNI code uses signal/sigset to install
 231   // then restore certain signal handler (e.g. to temporarily block SIGPIPE,
 232   // or have a SIGILL handler when detecting CPU type). When that happens,
 233   // JVM_handle_linux_signal() might be invoked with junk info/ucVoid. To
 234   // avoid unnecessary crash when libjsig is not preloaded, try handle signals
 235   // that do not require siginfo/ucontext first.
 236 
 237   if (sig == SIGPIPE || sig == SIGXFSZ) {
 238     // allow chained handler to go first
 239     if (os::Linux::chained_handler(sig, info, ucVoid)) {
 240       return true;
 241     } else {
 242       if (PrintMiscellaneous && (WizardMode || Verbose)) {
 243         char buf[64];
 244         warning("Ignoring %s - see bugs 4229104 or 646499219",
 245                 os::exception_name(sig, buf, sizeof(buf)));
 246       }
 247       return true;
 248     }
 249   }
 250 
 251   JavaThread* thread = NULL;
 252   VMThread* vmthread = NULL;
 253   if (os::Linux::signal_handlers_are_installed) {
 254     if (t != NULL ){
 255       if(t->is_Java_thread()) {
 256         thread = (JavaThread*)t;
 257       }
 258       else if(t->is_VM_thread()){
 259         vmthread = (VMThread *)t;
 260       }
 261     }
 262   }
 263 /*
 264   NOTE: does not seem to work on linux.
 265   if (info == NULL || info->si_code <= 0 || info->si_code == SI_NOINFO) {
 266     // can't decode this kind of signal
 267     info = NULL;
 268   } else {
 269     assert(sig == info->si_signo, "bad siginfo");
 270   }
 271 */
 272   // decide if this trap can be handled by a stub
 273   address stub = NULL;
 274 
 275   address pc          = NULL;
 276 
 277   //%note os_trap_1
 278   if (info != NULL && uc != NULL && thread != NULL) {
 279     pc = (address) os::Linux::ucontext_get_pc(uc);
 280 
 281     if (StubRoutines::is_safefetch_fault(pc)) {
 282       uc->uc_mcontext.gregs[REG_PC] = intptr_t(StubRoutines::continuation_for_safefetch_fault(pc));
 283       return 1;
 284     }
 285 
 286 #ifndef AMD64
 287     // Halt if SI_KERNEL before more crashes get misdiagnosed as Java bugs
 288     // This can happen in any running code (currently more frequently in
 289     // interpreter code but has been seen in compiled code)
 290     if (sig == SIGSEGV && info->si_addr == 0 && info->si_code == SI_KERNEL) {
 291       fatal("An irrecoverable SI_KERNEL SIGSEGV has occurred due "
 292             "to unstable signal handling in this distribution.");
 293     }
 294 #endif // AMD64
 295 
 296     // Handle ALL stack overflow variations here
 297     if (sig == SIGSEGV) {
 298       address addr = (address) info->si_addr;
 299 
 300       // check if fault address is within thread stack
 301       if (addr < thread->stack_base() &&
 302           addr >= thread->stack_base() - thread->stack_size()) {
 303         // stack overflow
 304         if (thread->in_stack_yellow_zone(addr)) {
 305           thread->disable_stack_yellow_zone();
 306           if (thread->thread_state() == _thread_in_Java) {
 307             // Throw a stack overflow exception.  Guard pages will be reenabled
 308             // while unwinding the stack.
 309             stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::STACK_OVERFLOW);
 310           } else {
 311             // Thread was in the vm or native code.  Return and try to finish.
 312             return 1;
 313           }
 314         } else if (thread->in_stack_red_zone(addr)) {
 315           // Fatal red zone violation.  Disable the guard pages and fall through
 316           // to handle_unexpected_exception way down below.
 317           thread->disable_stack_red_zone();
 318           tty->print_raw_cr("An irrecoverable stack overflow has occurred.");
 319 
 320           // This is a likely cause, but hard to verify. Let's just print
 321           // it as a hint.
 322           tty->print_raw_cr("Please check if any of your loaded .so files has "
 323                             "enabled executable stack (see man page execstack(8))");
 324         } else {
 325           // Accessing stack address below sp may cause SEGV if current
 326           // thread has MAP_GROWSDOWN stack. This should only happen when
 327           // current thread was created by user code with MAP_GROWSDOWN flag
 328           // and then attached to VM. See notes in os_linux.cpp.
 329           if (thread->osthread()->expanding_stack() == 0) {
 330              thread->osthread()->set_expanding_stack();
 331              if (os::Linux::manually_expand_stack(thread, addr)) {
 332                thread->osthread()->clear_expanding_stack();
 333                return 1;
 334              }
 335              thread->osthread()->clear_expanding_stack();
 336           } else {
 337              fatal("recursive segv. expanding stack.");
 338           }
 339         }
 340       }
 341     }
 342 
 343     if ((sig == SIGSEGV) && VM_Version::is_cpuinfo_segv_addr(pc)) {
 344       // Verify that OS save/restore AVX registers.
 345       stub = VM_Version::cpuinfo_cont_addr();
 346     }
 347 
 348     if (thread->thread_state() == _thread_in_Java) {
 349       // Java thread running in Java code => find exception handler if any
 350       // a fault inside compiled code, the interpreter, or a stub
 351 
 352       if (sig == SIGSEGV && os::is_poll_address((address)info->si_addr)) {
 353         stub = SharedRuntime::get_poll_stub(pc);
 354       } else if (sig == SIGBUS /* && info->si_code == BUS_OBJERR */) {
 355         // BugId 4454115: A read from a MappedByteBuffer can fault
 356         // here if the underlying file has been truncated.
 357         // Do not crash the VM in such a case.
 358         CodeBlob* cb = CodeCache::find_blob_unsafe(pc);
 359         nmethod* nm = (cb != NULL && cb->is_nmethod()) ? (nmethod*)cb : NULL;
 360         if (nm != NULL && nm->has_unsafe_access()) {
 361           stub = StubRoutines::handler_for_unsafe_access();
 362         }
 363       }
 364       else
 365 
 366 #ifdef AMD64
 367       if (sig == SIGFPE  &&
 368           (info->si_code == FPE_INTDIV || info->si_code == FPE_FLTDIV)) {
 369         stub =
 370           SharedRuntime::
 371           continuation_for_implicit_exception(thread,
 372                                               pc,
 373                                               SharedRuntime::
 374                                               IMPLICIT_DIVIDE_BY_ZERO);
 375 #else
 376       if (sig == SIGFPE /* && info->si_code == FPE_INTDIV */) {
 377         // HACK: si_code does not work on linux 2.2.12-20!!!
 378         int op = pc[0];
 379         if (op == 0xDB) {
 380           // FIST
 381           // TODO: The encoding of D2I in i486.ad can cause an exception
 382           // prior to the fist instruction if there was an invalid operation
 383           // pending. We want to dismiss that exception. From the win_32
 384           // side it also seems that if it really was the fist causing
 385           // the exception that we do the d2i by hand with different
 386           // rounding. Seems kind of weird.
 387           // NOTE: that we take the exception at the NEXT floating point instruction.
 388           assert(pc[0] == 0xDB, "not a FIST opcode");
 389           assert(pc[1] == 0x14, "not a FIST opcode");
 390           assert(pc[2] == 0x24, "not a FIST opcode");
 391           return true;
 392         } else if (op == 0xF7) {
 393           // IDIV
 394           stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_DIVIDE_BY_ZERO);
 395         } else {
 396           // TODO: handle more cases if we are using other x86 instructions
 397           //   that can generate SIGFPE signal on linux.
 398           tty->print_cr("unknown opcode 0x%X with SIGFPE.", op);
 399           fatal("please update this code.");
 400         }
 401 #endif // AMD64
 402       } else if (sig == SIGSEGV &&
 403                !MacroAssembler::needs_explicit_null_check((intptr_t)info->si_addr)) {
 404           // Determination of interpreter/vtable stub/compiled code null exception
 405           stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_NULL);
 406       }
 407     } else if (thread->thread_state() == _thread_in_vm &&
 408                sig == SIGBUS && /* info->si_code == BUS_OBJERR && */
 409                thread->doing_unsafe_access()) {
 410         stub = StubRoutines::handler_for_unsafe_access();
 411     }
 412 
 413     // jni_fast_Get<Primitive>Field can trap at certain pc's if a GC kicks in
 414     // and the heap gets shrunk before the field access.
 415     if ((sig == SIGSEGV) || (sig == SIGBUS)) {
 416       address addr = JNI_FastGetField::find_slowcase_pc(pc);
 417       if (addr != (address)-1) {
 418         stub = addr;
 419       }
 420     }
 421 
 422     // Check to see if we caught the safepoint code in the
 423     // process of write protecting the memory serialization page.
 424     // It write enables the page immediately after protecting it
 425     // so we can just return to retry the write.
 426     if ((sig == SIGSEGV) &&
 427         os::is_memory_serialize_page(thread, (address) info->si_addr)) {
 428       // Block current thread until the memory serialize page permission restored.
 429       os::block_on_serialize_page_trap();
 430       return true;
 431     }
 432   }
 433 
 434 #ifndef AMD64
 435   // Execution protection violation
 436   //
 437   // This should be kept as the last step in the triage.  We don't
 438   // have a dedicated trap number for a no-execute fault, so be
 439   // conservative and allow other handlers the first shot.
 440   //
 441   // Note: We don't test that info->si_code == SEGV_ACCERR here.
 442   // this si_code is so generic that it is almost meaningless; and
 443   // the si_code for this condition may change in the future.
 444   // Furthermore, a false-positive should be harmless.
 445   if (UnguardOnExecutionViolation > 0 &&
 446       (sig == SIGSEGV || sig == SIGBUS) &&
 447       uc->uc_mcontext.gregs[REG_TRAPNO] == trap_page_fault) {
 448     int page_size = os::vm_page_size();
 449     address addr = (address) info->si_addr;
 450     address pc = os::Linux::ucontext_get_pc(uc);
 451     // Make sure the pc and the faulting address are sane.
 452     //
 453     // If an instruction spans a page boundary, and the page containing
 454     // the beginning of the instruction is executable but the following
 455     // page is not, the pc and the faulting address might be slightly
 456     // different - we still want to unguard the 2nd page in this case.
 457     //
 458     // 15 bytes seems to be a (very) safe value for max instruction size.
 459     bool pc_is_near_addr =
 460       (pointer_delta((void*) addr, (void*) pc, sizeof(char)) < 15);
 461     bool instr_spans_page_boundary =
 462       (align_size_down((intptr_t) pc ^ (intptr_t) addr,
 463                        (intptr_t) page_size) > 0);
 464 
 465     if (pc == addr || (pc_is_near_addr && instr_spans_page_boundary)) {
 466       static volatile address last_addr =
 467         (address) os::non_memory_address_word();
 468 
 469       // In conservative mode, don't unguard unless the address is in the VM
 470       if (addr != last_addr &&
 471           (UnguardOnExecutionViolation > 1 || os::address_is_in_vm(addr))) {
 472 
 473         // Set memory to RWX and retry
 474         address page_start =
 475           (address) align_size_down((intptr_t) addr, (intptr_t) page_size);
 476         bool res = os::protect_memory((char*) page_start, page_size,
 477                                       os::MEM_PROT_RWX);
 478 
 479         if (PrintMiscellaneous && Verbose) {
 480           char buf[256];
 481           jio_snprintf(buf, sizeof(buf), "Execution protection violation "
 482                        "at " INTPTR_FORMAT
 483                        ", unguarding " INTPTR_FORMAT ": %s, errno=%d", addr,
 484                        page_start, (res ? "success" : "failed"), errno);
 485           tty->print_raw_cr(buf);
 486         }
 487         stub = pc;
 488 
 489         // Set last_addr so if we fault again at the same address, we don't end
 490         // up in an endless loop.
 491         //
 492         // There are two potential complications here.  Two threads trapping at
 493         // the same address at the same time could cause one of the threads to
 494         // think it already unguarded, and abort the VM.  Likely very rare.
 495         //
 496         // The other race involves two threads alternately trapping at
 497         // different addresses and failing to unguard the page, resulting in
 498         // an endless loop.  This condition is probably even more unlikely than
 499         // the first.
 500         //
 501         // Although both cases could be avoided by using locks or thread local
 502         // last_addr, these solutions are unnecessary complication: this
 503         // handler is a best-effort safety net, not a complete solution.  It is
 504         // disabled by default and should only be used as a workaround in case
 505         // we missed any no-execute-unsafe VM code.
 506 
 507         last_addr = addr;
 508       }
 509     }
 510   }
 511 #endif // !AMD64
 512 
 513   if (stub != NULL) {
 514     // save all thread context in case we need to restore it
 515     if (thread != NULL) thread->set_saved_exception_pc(pc);
 516 
 517     uc->uc_mcontext.gregs[REG_PC] = (greg_t)stub;
 518     return true;
 519   }
 520 
 521   // signal-chaining
 522   if (os::Linux::chained_handler(sig, info, ucVoid)) {
 523      return true;
 524   }
 525 
 526   if (!abort_if_unrecognized) {
 527     // caller wants another chance, so give it to him
 528     return false;
 529   }
 530 
 531   if (pc == NULL && uc != NULL) {
 532     pc = os::Linux::ucontext_get_pc(uc);
 533   }
 534 
 535   // unmask current signal
 536   sigset_t newset;
 537   sigemptyset(&newset);
 538   sigaddset(&newset, sig);
 539   sigprocmask(SIG_UNBLOCK, &newset, NULL);
 540 
 541   VMError err(t, sig, pc, info, ucVoid);
 542   err.report_and_die();
 543 
 544   ShouldNotReachHere();
 545 }
 546 
 547 void os::Linux::init_thread_fpu_state(void) {
 548 #ifndef AMD64
 549   // set fpu to 53 bit precision
 550   set_fpu_control_word(0x27f);
 551 #endif // !AMD64
 552 }
 553 
 554 int os::Linux::get_fpu_control_word(void) {
 555 #ifdef AMD64
 556   return 0;
 557 #else
 558   int fpu_control;
 559   _FPU_GETCW(fpu_control);
 560   return fpu_control & 0xffff;
 561 #endif // AMD64
 562 }
 563 
 564 void os::Linux::set_fpu_control_word(int fpu_control) {
 565 #ifndef AMD64
 566   _FPU_SETCW(fpu_control);
 567 #endif // !AMD64
 568 }
 569 
 570 // Check that the linux kernel version is 2.4 or higher since earlier
 571 // versions do not support SSE without patches.
 572 bool os::supports_sse() {
 573 #ifdef AMD64
 574   return true;
 575 #else
 576   struct utsname uts;
 577   if( uname(&uts) != 0 ) return false; // uname fails?
 578   char *minor_string;
 579   int major = strtol(uts.release,&minor_string,10);
 580   int minor = strtol(minor_string+1,NULL,10);
 581   bool result = (major > 2 || (major==2 && minor >= 4));
 582 #ifndef PRODUCT
 583   if (PrintMiscellaneous && Verbose) {
 584     tty->print("OS version is %d.%d, which %s support SSE/SSE2\n",
 585                major,minor, result ? "DOES" : "does NOT");
 586   }
 587 #endif
 588   return result;
 589 #endif // AMD64
 590 }
 591 
 592 bool os::is_allocatable(size_t bytes) {
 593 #ifdef AMD64
 594   // unused on amd64?
 595   return true;
 596 #else
 597 
 598   if (bytes < 2 * G) {
 599     return true;
 600   }
 601 
 602   char* addr = reserve_memory(bytes, NULL);
 603 
 604   if (addr != NULL) {
 605     release_memory(addr, bytes);
 606   }
 607 
 608   return addr != NULL;
 609 #endif // AMD64
 610 }
 611 
 612 ////////////////////////////////////////////////////////////////////////////////
 613 // thread stack
 614 
 615 #ifdef AMD64
 616 size_t os::Linux::min_stack_allowed  = 64 * K;
 617 
 618 // amd64: pthread on amd64 is always in floating stack mode
 619 bool os::Linux::supports_variable_stack_size() {  return true; }
 620 #else
 621 size_t os::Linux::min_stack_allowed  =  (48 DEBUG_ONLY(+4))*K;
 622 
 623 #ifdef __GNUC__
 624 #define GET_GS() ({int gs; __asm__ volatile("movw %%gs, %w0":"=q"(gs)); gs&0xffff;})
 625 #endif
 626 
 627 // Test if pthread library can support variable thread stack size. LinuxThreads
 628 // in fixed stack mode allocates 2M fixed slot for each thread. LinuxThreads
 629 // in floating stack mode and NPTL support variable stack size.
 630 bool os::Linux::supports_variable_stack_size() {
 631   if (os::Linux::is_NPTL()) {
 632      // NPTL, yes
 633      return true;
 634 
 635   } else {
 636     // Note: We can't control default stack size when creating a thread.
 637     // If we use non-default stack size (pthread_attr_setstacksize), both
 638     // floating stack and non-floating stack LinuxThreads will return the
 639     // same value. This makes it impossible to implement this function by
 640     // detecting thread stack size directly.
 641     //
 642     // An alternative approach is to check %gs. Fixed-stack LinuxThreads
 643     // do not use %gs, so its value is 0. Floating-stack LinuxThreads use
 644     // %gs (either as LDT selector or GDT selector, depending on kernel)
 645     // to access thread specific data.
 646     //
 647     // Note that %gs is a reserved glibc register since early 2001, so
 648     // applications are not allowed to change its value (Ulrich Drepper from
 649     // Redhat confirmed that all known offenders have been modified to use
 650     // either %fs or TSD). In the worst case scenario, when VM is embedded in
 651     // a native application that plays with %gs, we might see non-zero %gs
 652     // even LinuxThreads is running in fixed stack mode. As the result, we'll
 653     // return true and skip _thread_safety_check(), so we may not be able to
 654     // detect stack-heap collisions. But otherwise it's harmless.
 655     //
 656 #ifdef __GNUC__
 657     return (GET_GS() != 0);
 658 #else
 659     return false;
 660 #endif
 661   }
 662 }
 663 #endif // AMD64
 664 
 665 // return default stack size for thr_type
 666 size_t os::Linux::default_stack_size(os::ThreadType thr_type) {
 667   // default stack size (compiler thread needs larger stack)
 668 #ifdef AMD64
 669   size_t s = (thr_type == os::compiler_thread ? 4 * M : 1 * M);
 670 #else
 671   size_t s = (thr_type == os::compiler_thread ? 2 * M : 512 * K);
 672 #endif // AMD64
 673   return s;
 674 }
 675 
 676 size_t os::Linux::default_guard_size(os::ThreadType thr_type) {
 677   // Creating guard page is very expensive. Java thread has HotSpot
 678   // guard page, only enable glibc guard page for non-Java threads.
 679   return (thr_type == java_thread ? 0 : page_size());
 680 }
 681 
 682 // Java thread:
 683 //
 684 //   Low memory addresses
 685 //    +------------------------+
 686 //    |                        |\  JavaThread created by VM does not have glibc
 687 //    |    glibc guard page    | - guard, attached Java thread usually has
 688 //    |                        |/  1 page glibc guard.
 689 // P1 +------------------------+ Thread::stack_base() - Thread::stack_size()
 690 //    |                        |\
 691 //    |  HotSpot Guard Pages   | - red and yellow pages
 692 //    |                        |/
 693 //    +------------------------+ JavaThread::stack_yellow_zone_base()
 694 //    |                        |\
 695 //    |      Normal Stack      | -
 696 //    |                        |/
 697 // P2 +------------------------+ Thread::stack_base()
 698 //
 699 // Non-Java thread:
 700 //
 701 //   Low memory addresses
 702 //    +------------------------+
 703 //    |                        |\
 704 //    |  glibc guard page      | - usually 1 page
 705 //    |                        |/
 706 // P1 +------------------------+ Thread::stack_base() - Thread::stack_size()
 707 //    |                        |\
 708 //    |      Normal Stack      | -
 709 //    |                        |/
 710 // P2 +------------------------+ Thread::stack_base()
 711 //
 712 // ** P1 (aka bottom) and size ( P2 = P1 - size) are the address and stack size returned from
 713 //    pthread_attr_getstack()
 714 
 715 static void current_stack_region(address * bottom, size_t * size) {
 716   if (os::Linux::is_initial_thread()) {
 717      // initial thread needs special handling because pthread_getattr_np()
 718      // may return bogus value.
 719      *bottom = os::Linux::initial_thread_stack_bottom();
 720      *size   = os::Linux::initial_thread_stack_size();
 721   } else {
 722      pthread_attr_t attr;
 723 
 724      int rslt = pthread_getattr_np(pthread_self(), &attr);
 725 
 726      // JVM needs to know exact stack location, abort if it fails
 727      if (rslt != 0) {
 728        if (rslt == ENOMEM) {
 729          vm_exit_out_of_memory(0, OOM_MMAP_ERROR, "pthread_getattr_np");
 730        } else {
 731          fatal(err_msg("pthread_getattr_np failed with errno = %d", rslt));
 732        }
 733      }
 734 
 735      if (pthread_attr_getstack(&attr, (void **)bottom, size) != 0) {
 736          fatal("Can not locate current stack attributes!");
 737      }
 738 
 739      pthread_attr_destroy(&attr);
 740 
 741   }
 742   assert(os::current_stack_pointer() >= *bottom &&
 743          os::current_stack_pointer() < *bottom + *size, "just checking");
 744 }
 745 
 746 address os::current_stack_base() {
 747   address bottom;
 748   size_t size;
 749   current_stack_region(&bottom, &size);
 750   return (bottom + size);
 751 }
 752 
 753 size_t os::current_stack_size() {
 754   // stack size includes normal stack and HotSpot guard pages
 755   address bottom;
 756   size_t size;
 757   current_stack_region(&bottom, &size);
 758   return size;
 759 }
 760 
 761 /////////////////////////////////////////////////////////////////////////////
 762 // helper functions for fatal error handler
 763 
 764 void os::print_context(outputStream *st, void *context) {
 765   if (context == NULL) return;
 766 
 767   ucontext_t *uc = (ucontext_t*)context;
 768   st->print_cr("Registers:");
 769 #ifdef AMD64
 770   st->print(  "RAX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RAX]);
 771   st->print(", RBX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RBX]);
 772   st->print(", RCX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RCX]);
 773   st->print(", RDX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RDX]);
 774   st->cr();
 775   st->print(  "RSP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RSP]);
 776   st->print(", RBP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RBP]);
 777   st->print(", RSI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RSI]);
 778   st->print(", RDI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RDI]);
 779   st->cr();
 780   st->print(  "R8 =" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R8]);
 781   st->print(", R9 =" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R9]);
 782   st->print(", R10=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R10]);
 783   st->print(", R11=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R11]);
 784   st->cr();
 785   st->print(  "R12=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R12]);
 786   st->print(", R13=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R13]);
 787   st->print(", R14=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R14]);
 788   st->print(", R15=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R15]);
 789   st->cr();
 790   st->print(  "RIP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RIP]);
 791   st->print(", EFLAGS=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EFL]);
 792   st->print(", CSGSFS=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_CSGSFS]);
 793   st->print(", ERR=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_ERR]);
 794   st->cr();
 795   st->print("  TRAPNO=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_TRAPNO]);
 796 #else
 797   st->print(  "EAX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EAX]);
 798   st->print(", EBX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EBX]);
 799   st->print(", ECX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_ECX]);
 800   st->print(", EDX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EDX]);
 801   st->cr();
 802   st->print(  "ESP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_UESP]);
 803   st->print(", EBP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EBP]);
 804   st->print(", ESI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_ESI]);
 805   st->print(", EDI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EDI]);
 806   st->cr();
 807   st->print(  "EIP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EIP]);
 808   st->print(", EFLAGS=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EFL]);
 809   st->print(", CR2=" INTPTR_FORMAT, uc->uc_mcontext.cr2);
 810 #endif // AMD64
 811   st->cr();
 812   st->cr();
 813 
 814   intptr_t *sp = (intptr_t *)os::Linux::ucontext_get_sp(uc);
 815   st->print_cr("Top of Stack: (sp=" PTR_FORMAT ")", sp);
 816   print_hex_dump(st, (address)sp, (address)(sp + 8*sizeof(intptr_t)), sizeof(intptr_t));
 817   st->cr();
 818 
 819   // Note: it may be unsafe to inspect memory near pc. For example, pc may
 820   // point to garbage if entry point in an nmethod is corrupted. Leave
 821   // this at the end, and hope for the best.
 822   address pc = os::Linux::ucontext_get_pc(uc);
 823   st->print_cr("Instructions: (pc=" PTR_FORMAT ")", pc);
 824   print_hex_dump(st, pc - 32, pc + 32, sizeof(char));
 825 }
 826 
 827 void os::print_register_info(outputStream *st, void *context) {
 828   if (context == NULL) return;
 829 
 830   ucontext_t *uc = (ucontext_t*)context;
 831 
 832   st->print_cr("Register to memory mapping:");
 833   st->cr();
 834 
 835   // this is horrendously verbose but the layout of the registers in the
 836   // context does not match how we defined our abstract Register set, so
 837   // we can't just iterate through the gregs area
 838 
 839   // this is only for the "general purpose" registers
 840 
 841 #ifdef AMD64
 842   st->print("RAX="); print_location(st, uc->uc_mcontext.gregs[REG_RAX]);
 843   st->print("RBX="); print_location(st, uc->uc_mcontext.gregs[REG_RBX]);
 844   st->print("RCX="); print_location(st, uc->uc_mcontext.gregs[REG_RCX]);
 845   st->print("RDX="); print_location(st, uc->uc_mcontext.gregs[REG_RDX]);
 846   st->print("RSP="); print_location(st, uc->uc_mcontext.gregs[REG_RSP]);
 847   st->print("RBP="); print_location(st, uc->uc_mcontext.gregs[REG_RBP]);
 848   st->print("RSI="); print_location(st, uc->uc_mcontext.gregs[REG_RSI]);
 849   st->print("RDI="); print_location(st, uc->uc_mcontext.gregs[REG_RDI]);
 850   st->print("R8 ="); print_location(st, uc->uc_mcontext.gregs[REG_R8]);
 851   st->print("R9 ="); print_location(st, uc->uc_mcontext.gregs[REG_R9]);
 852   st->print("R10="); print_location(st, uc->uc_mcontext.gregs[REG_R10]);
 853   st->print("R11="); print_location(st, uc->uc_mcontext.gregs[REG_R11]);
 854   st->print("R12="); print_location(st, uc->uc_mcontext.gregs[REG_R12]);
 855   st->print("R13="); print_location(st, uc->uc_mcontext.gregs[REG_R13]);
 856   st->print("R14="); print_location(st, uc->uc_mcontext.gregs[REG_R14]);
 857   st->print("R15="); print_location(st, uc->uc_mcontext.gregs[REG_R15]);
 858 #else
 859   st->print("EAX="); print_location(st, uc->uc_mcontext.gregs[REG_EAX]);
 860   st->print("EBX="); print_location(st, uc->uc_mcontext.gregs[REG_EBX]);
 861   st->print("ECX="); print_location(st, uc->uc_mcontext.gregs[REG_ECX]);
 862   st->print("EDX="); print_location(st, uc->uc_mcontext.gregs[REG_EDX]);
 863   st->print("ESP="); print_location(st, uc->uc_mcontext.gregs[REG_ESP]);
 864   st->print("EBP="); print_location(st, uc->uc_mcontext.gregs[REG_EBP]);
 865   st->print("ESI="); print_location(st, uc->uc_mcontext.gregs[REG_ESI]);
 866   st->print("EDI="); print_location(st, uc->uc_mcontext.gregs[REG_EDI]);
 867 #endif // AMD64
 868 
 869   st->cr();
 870 }
 871 
 872 void os::setup_fpu() {
 873 #ifndef AMD64
 874   address fpu_cntrl = StubRoutines::addr_fpu_cntrl_wrd_std();
 875   __asm__ volatile (  "fldcw (%0)" :
 876                       : "r" (fpu_cntrl) : "memory");
 877 #endif // !AMD64
 878 }
 879 
 880 #ifndef PRODUCT
 881 void os::verify_stack_alignment() {
 882 #ifdef AMD64
 883   assert(((intptr_t)os::current_stack_pointer() & (StackAlignmentInBytes-1)) == 0, "incorrect stack alignment");
 884 #endif
 885 }
 886 #endif
 887 
 888 
 889 /*
 890  * IA32 only: execute code at a high address in case buggy NX emulation is present. I.e. avoid CS limit
 891  * updates (JDK-8023956).
 892  */
 893 void os::workaround_expand_exec_shield_cs_limit() {
 894 #if defined(IA32)
 895   size_t page_size = os::vm_page_size();
 896   /*
 897    * Take the highest VA the OS will give us and exec
 898    *
 899    * Although using -(pagesz) as mmap hint works on newer kernel as you would
 900    * think, older variants affected by this work-around don't (search forward only).
 901    *
 902    * On the affected distributions, we understand the memory layout to be:
 903    *
 904    *   TASK_LIMIT= 3G, main stack base close to TASK_LIMT.
 905    *
 906    * A few pages south main stack will do it.
 907    *
 908    * If we are embedded in an app other than launcher (initial != main stack),
 909    * we don't have much control or understanding of the address space, just let it slide.
 910    */
 911   char* hint = (char*) (Linux::initial_thread_stack_bottom() -
 912                         ((StackYellowPages + StackRedPages + 1) * page_size));
 913   char* codebuf = os::reserve_memory(page_size, hint);
 914   if ( (codebuf == NULL) || (!os::commit_memory(codebuf, page_size, true)) ) {
 915     return; // No matter, we tried, best effort.
 916   }
 917 
 918   MemTracker::record_virtual_memory_type((address)codebuf, mtInternal);
 919 
 920   if (PrintMiscellaneous && (Verbose || WizardMode)) {
 921      tty->print_cr("[CS limit NX emulation work-around, exec code at: %p]", codebuf);
 922   }
 923 
 924   // Some code to exec: the 'ret' instruction
 925   codebuf[0] = 0xC3;
 926 
 927   // Call the code in the codebuf
 928   __asm__ volatile("call *%0" : : "r"(codebuf));
 929 
 930   // keep the page mapped so CS limit isn't reduced.
 931 #endif
 932 }
 933 
 934 int os::extra_bang_size_in_bytes() {
 935   // JDK-8050147 requires the full cache line bang for x86.
 936   return VM_Version::L1_line_size();
 937 }
--- EOF ---