os_linux_x86.cpp revision 5346:899ecf76b570
1/* 2 * Copyright (c) 1999, 2012, 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 "utilities/events.hpp" 53#include "utilities/vmError.hpp" 54 55// put OS-includes here 56# include <sys/types.h> 57# include <sys/mman.h> 58# include <pthread.h> 59# include <signal.h> 60# include <errno.h> 61# include <dlfcn.h> 62# include <stdlib.h> 63# include <stdio.h> 64# include <unistd.h> 65# include <sys/resource.h> 66# include <pthread.h> 67# include <sys/stat.h> 68# include <sys/time.h> 69# include <sys/utsname.h> 70# include <sys/socket.h> 71# include <sys/wait.h> 72# include <pwd.h> 73# include <poll.h> 74# include <ucontext.h> 75# include <fpu_control.h> 76 77#ifdef AMD64 78#define REG_SP REG_RSP 79#define REG_PC REG_RIP 80#define REG_FP REG_RBP 81#define SPELL_REG_SP "rsp" 82#define SPELL_REG_FP "rbp" 83#else 84#define REG_SP REG_UESP 85#define REG_PC REG_EIP 86#define REG_FP REG_EBP 87#define SPELL_REG_SP "esp" 88#define SPELL_REG_FP "ebp" 89#endif // AMD64 90 91address os::current_stack_pointer() { 92#ifdef SPARC_WORKS 93 register void *esp; 94 __asm__("mov %%"SPELL_REG_SP", %0":"=r"(esp)); 95 return (address) ((char*)esp + sizeof(long)*2); 96#elif defined(__clang__) 97 intptr_t* esp; 98 __asm__ __volatile__ ("mov %%"SPELL_REG_SP", %0":"=r"(esp):); 99 return (address) esp; 100#else 101 register void *esp __asm__ (SPELL_REG_SP); 102 return (address) esp; 103#endif 104} 105 106char* os::non_memory_address_word() { 107 // Must never look like an address returned by reserve_memory, 108 // even in its subfields (as defined by the CPU immediate fields, 109 // if the CPU splits constants across multiple instructions). 110 111 return (char*) -1; 112} 113 114void os::initialize_thread(Thread* thr) { 115// Nothing to do. 116} 117 118address os::Linux::ucontext_get_pc(ucontext_t * uc) { 119 return (address)uc->uc_mcontext.gregs[REG_PC]; 120} 121 122intptr_t* os::Linux::ucontext_get_sp(ucontext_t * uc) { 123 return (intptr_t*)uc->uc_mcontext.gregs[REG_SP]; 124} 125 126intptr_t* os::Linux::ucontext_get_fp(ucontext_t * uc) { 127 return (intptr_t*)uc->uc_mcontext.gregs[REG_FP]; 128} 129 130// For Forte Analyzer AsyncGetCallTrace profiling support - thread 131// is currently interrupted by SIGPROF. 132// os::Solaris::fetch_frame_from_ucontext() tries to skip nested signal 133// frames. Currently we don't do that on Linux, so it's the same as 134// os::fetch_frame_from_context(). 135ExtendedPC os::Linux::fetch_frame_from_ucontext(Thread* thread, 136 ucontext_t* uc, intptr_t** ret_sp, intptr_t** ret_fp) { 137 138 assert(thread != NULL, "just checking"); 139 assert(ret_sp != NULL, "just checking"); 140 assert(ret_fp != NULL, "just checking"); 141 142 return os::fetch_frame_from_context(uc, ret_sp, ret_fp); 143} 144 145ExtendedPC os::fetch_frame_from_context(void* ucVoid, 146 intptr_t** ret_sp, intptr_t** ret_fp) { 147 148 ExtendedPC epc; 149 ucontext_t* uc = (ucontext_t*)ucVoid; 150 151 if (uc != NULL) { 152 epc = ExtendedPC(os::Linux::ucontext_get_pc(uc)); 153 if (ret_sp) *ret_sp = os::Linux::ucontext_get_sp(uc); 154 if (ret_fp) *ret_fp = os::Linux::ucontext_get_fp(uc); 155 } else { 156 // construct empty ExtendedPC for return value checking 157 epc = ExtendedPC(NULL); 158 if (ret_sp) *ret_sp = (intptr_t *)NULL; 159 if (ret_fp) *ret_fp = (intptr_t *)NULL; 160 } 161 162 return epc; 163} 164 165frame os::fetch_frame_from_context(void* ucVoid) { 166 intptr_t* sp; 167 intptr_t* fp; 168 ExtendedPC epc = fetch_frame_from_context(ucVoid, &sp, &fp); 169 return frame(sp, fp, epc.pc()); 170} 171 172// By default, gcc always save frame pointer (%ebp/%rbp) on stack. It may get 173// turned off by -fomit-frame-pointer, 174frame os::get_sender_for_C_frame(frame* fr) { 175 return frame(fr->sender_sp(), fr->link(), fr->sender_pc()); 176} 177 178intptr_t* _get_previous_fp() { 179#ifdef SPARC_WORKS 180 register intptr_t **ebp; 181 __asm__("mov %%"SPELL_REG_FP", %0":"=r"(ebp)); 182#elif defined(__clang__) 183 intptr_t **ebp; 184 __asm__ __volatile__ ("mov %%"SPELL_REG_FP", %0":"=r"(ebp):); 185#else 186 register intptr_t **ebp __asm__ (SPELL_REG_FP); 187#endif 188 return (intptr_t*) *ebp; // we want what it points to. 189} 190 191 192frame os::current_frame() { 193 intptr_t* fp = _get_previous_fp(); 194 frame myframe((intptr_t*)os::current_stack_pointer(), 195 (intptr_t*)fp, 196 CAST_FROM_FN_PTR(address, os::current_frame)); 197 if (os::is_first_C_frame(&myframe)) { 198 // stack is not walkable 199 return frame(); 200 } else { 201 return os::get_sender_for_C_frame(&myframe); 202 } 203} 204 205// Utility functions 206 207// From IA32 System Programming Guide 208enum { 209 trap_page_fault = 0xE 210}; 211 212extern "C" JNIEXPORT int 213JVM_handle_linux_signal(int sig, 214 siginfo_t* info, 215 void* ucVoid, 216 int abort_if_unrecognized) { 217 ucontext_t* uc = (ucontext_t*) ucVoid; 218 219 Thread* t = ThreadLocalStorage::get_thread_slow(); 220 221 // Must do this before SignalHandlerMark, if crash protection installed we will longjmp away 222 // (no destructors can be run) 223 os::WatcherThreadCrashProtection::check_crash_protection(sig, t); 224 225 SignalHandlerMark shm(t); 226 227 // Note: it's not uncommon that JNI code uses signal/sigset to install 228 // then restore certain signal handler (e.g. to temporarily block SIGPIPE, 229 // or have a SIGILL handler when detecting CPU type). When that happens, 230 // JVM_handle_linux_signal() might be invoked with junk info/ucVoid. To 231 // avoid unnecessary crash when libjsig is not preloaded, try handle signals 232 // that do not require siginfo/ucontext first. 233 234 if (sig == SIGPIPE || sig == SIGXFSZ) { 235 // allow chained handler to go first 236 if (os::Linux::chained_handler(sig, info, ucVoid)) { 237 return true; 238 } else { 239 if (PrintMiscellaneous && (WizardMode || Verbose)) { 240 char buf[64]; 241 warning("Ignoring %s - see bugs 4229104 or 646499219", 242 os::exception_name(sig, buf, sizeof(buf))); 243 } 244 return true; 245 } 246 } 247 248 JavaThread* thread = NULL; 249 VMThread* vmthread = NULL; 250 if (os::Linux::signal_handlers_are_installed) { 251 if (t != NULL ){ 252 if(t->is_Java_thread()) { 253 thread = (JavaThread*)t; 254 } 255 else if(t->is_VM_thread()){ 256 vmthread = (VMThread *)t; 257 } 258 } 259 } 260/* 261 NOTE: does not seem to work on linux. 262 if (info == NULL || info->si_code <= 0 || info->si_code == SI_NOINFO) { 263 // can't decode this kind of signal 264 info = NULL; 265 } else { 266 assert(sig == info->si_signo, "bad siginfo"); 267 } 268*/ 269 // decide if this trap can be handled by a stub 270 address stub = NULL; 271 272 address pc = NULL; 273 274 //%note os_trap_1 275 if (info != NULL && uc != NULL && thread != NULL) { 276 pc = (address) os::Linux::ucontext_get_pc(uc); 277 278 if (StubRoutines::is_safefetch_fault(pc)) { 279 uc->uc_mcontext.gregs[REG_PC] = intptr_t(StubRoutines::continuation_for_safefetch_fault(pc)); 280 return 1; 281 } 282 283#ifndef AMD64 284 // Halt if SI_KERNEL before more crashes get misdiagnosed as Java bugs 285 // This can happen in any running code (currently more frequently in 286 // interpreter code but has been seen in compiled code) 287 if (sig == SIGSEGV && info->si_addr == 0 && info->si_code == SI_KERNEL) { 288 fatal("An irrecoverable SI_KERNEL SIGSEGV has occurred due " 289 "to unstable signal handling in this distribution."); 290 } 291#endif // AMD64 292 293 // Handle ALL stack overflow variations here 294 if (sig == SIGSEGV) { 295 address addr = (address) info->si_addr; 296 297 // check if fault address is within thread stack 298 if (addr < thread->stack_base() && 299 addr >= thread->stack_base() - thread->stack_size()) { 300 // stack overflow 301 if (thread->in_stack_yellow_zone(addr)) { 302 thread->disable_stack_yellow_zone(); 303 if (thread->thread_state() == _thread_in_Java) { 304 // Throw a stack overflow exception. Guard pages will be reenabled 305 // while unwinding the stack. 306 stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::STACK_OVERFLOW); 307 } else { 308 // Thread was in the vm or native code. Return and try to finish. 309 return 1; 310 } 311 } else if (thread->in_stack_red_zone(addr)) { 312 // Fatal red zone violation. Disable the guard pages and fall through 313 // to handle_unexpected_exception way down below. 314 thread->disable_stack_red_zone(); 315 tty->print_raw_cr("An irrecoverable stack overflow has occurred."); 316 317 // This is a likely cause, but hard to verify. Let's just print 318 // it as a hint. 319 tty->print_raw_cr("Please check if any of your loaded .so files has " 320 "enabled executable stack (see man page execstack(8))"); 321 } else { 322 // Accessing stack address below sp may cause SEGV if current 323 // thread has MAP_GROWSDOWN stack. This should only happen when 324 // current thread was created by user code with MAP_GROWSDOWN flag 325 // and then attached to VM. See notes in os_linux.cpp. 326 if (thread->osthread()->expanding_stack() == 0) { 327 thread->osthread()->set_expanding_stack(); 328 if (os::Linux::manually_expand_stack(thread, addr)) { 329 thread->osthread()->clear_expanding_stack(); 330 return 1; 331 } 332 thread->osthread()->clear_expanding_stack(); 333 } else { 334 fatal("recursive segv. expanding stack."); 335 } 336 } 337 } 338 } 339 340 if (thread->thread_state() == _thread_in_Java) { 341 // Java thread running in Java code => find exception handler if any 342 // a fault inside compiled code, the interpreter, or a stub 343 344 if (sig == SIGSEGV && os::is_poll_address((address)info->si_addr)) { 345 stub = SharedRuntime::get_poll_stub(pc); 346 } else if (sig == SIGBUS /* && info->si_code == BUS_OBJERR */) { 347 // BugId 4454115: A read from a MappedByteBuffer can fault 348 // here if the underlying file has been truncated. 349 // Do not crash the VM in such a case. 350 CodeBlob* cb = CodeCache::find_blob_unsafe(pc); 351 nmethod* nm = (cb != NULL && cb->is_nmethod()) ? (nmethod*)cb : NULL; 352 if (nm != NULL && nm->has_unsafe_access()) { 353 stub = StubRoutines::handler_for_unsafe_access(); 354 } 355 } 356 else 357 358#ifdef AMD64 359 if (sig == SIGFPE && 360 (info->si_code == FPE_INTDIV || info->si_code == FPE_FLTDIV)) { 361 stub = 362 SharedRuntime:: 363 continuation_for_implicit_exception(thread, 364 pc, 365 SharedRuntime:: 366 IMPLICIT_DIVIDE_BY_ZERO); 367#else 368 if (sig == SIGFPE /* && info->si_code == FPE_INTDIV */) { 369 // HACK: si_code does not work on linux 2.2.12-20!!! 370 int op = pc[0]; 371 if (op == 0xDB) { 372 // FIST 373 // TODO: The encoding of D2I in i486.ad can cause an exception 374 // prior to the fist instruction if there was an invalid operation 375 // pending. We want to dismiss that exception. From the win_32 376 // side it also seems that if it really was the fist causing 377 // the exception that we do the d2i by hand with different 378 // rounding. Seems kind of weird. 379 // NOTE: that we take the exception at the NEXT floating point instruction. 380 assert(pc[0] == 0xDB, "not a FIST opcode"); 381 assert(pc[1] == 0x14, "not a FIST opcode"); 382 assert(pc[2] == 0x24, "not a FIST opcode"); 383 return true; 384 } else if (op == 0xF7) { 385 // IDIV 386 stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_DIVIDE_BY_ZERO); 387 } else { 388 // TODO: handle more cases if we are using other x86 instructions 389 // that can generate SIGFPE signal on linux. 390 tty->print_cr("unknown opcode 0x%X with SIGFPE.", op); 391 fatal("please update this code."); 392 } 393#endif // AMD64 394 } else if (sig == SIGSEGV && 395 !MacroAssembler::needs_explicit_null_check((intptr_t)info->si_addr)) { 396 // Determination of interpreter/vtable stub/compiled code null exception 397 stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_NULL); 398 } 399 } else if (thread->thread_state() == _thread_in_vm && 400 sig == SIGBUS && /* info->si_code == BUS_OBJERR && */ 401 thread->doing_unsafe_access()) { 402 stub = StubRoutines::handler_for_unsafe_access(); 403 } 404 405 // jni_fast_Get<Primitive>Field can trap at certain pc's if a GC kicks in 406 // and the heap gets shrunk before the field access. 407 if ((sig == SIGSEGV) || (sig == SIGBUS)) { 408 address addr = JNI_FastGetField::find_slowcase_pc(pc); 409 if (addr != (address)-1) { 410 stub = addr; 411 } 412 } 413 414 // Check to see if we caught the safepoint code in the 415 // process of write protecting the memory serialization page. 416 // It write enables the page immediately after protecting it 417 // so we can just return to retry the write. 418 if ((sig == SIGSEGV) && 419 os::is_memory_serialize_page(thread, (address) info->si_addr)) { 420 // Block current thread until the memory serialize page permission restored. 421 os::block_on_serialize_page_trap(); 422 return true; 423 } 424 } 425 426#ifndef AMD64 427 // Execution protection violation 428 // 429 // This should be kept as the last step in the triage. We don't 430 // have a dedicated trap number for a no-execute fault, so be 431 // conservative and allow other handlers the first shot. 432 // 433 // Note: We don't test that info->si_code == SEGV_ACCERR here. 434 // this si_code is so generic that it is almost meaningless; and 435 // the si_code for this condition may change in the future. 436 // Furthermore, a false-positive should be harmless. 437 if (UnguardOnExecutionViolation > 0 && 438 (sig == SIGSEGV || sig == SIGBUS) && 439 uc->uc_mcontext.gregs[REG_TRAPNO] == trap_page_fault) { 440 int page_size = os::vm_page_size(); 441 address addr = (address) info->si_addr; 442 address pc = os::Linux::ucontext_get_pc(uc); 443 // Make sure the pc and the faulting address are sane. 444 // 445 // If an instruction spans a page boundary, and the page containing 446 // the beginning of the instruction is executable but the following 447 // page is not, the pc and the faulting address might be slightly 448 // different - we still want to unguard the 2nd page in this case. 449 // 450 // 15 bytes seems to be a (very) safe value for max instruction size. 451 bool pc_is_near_addr = 452 (pointer_delta((void*) addr, (void*) pc, sizeof(char)) < 15); 453 bool instr_spans_page_boundary = 454 (align_size_down((intptr_t) pc ^ (intptr_t) addr, 455 (intptr_t) page_size) > 0); 456 457 if (pc == addr || (pc_is_near_addr && instr_spans_page_boundary)) { 458 static volatile address last_addr = 459 (address) os::non_memory_address_word(); 460 461 // In conservative mode, don't unguard unless the address is in the VM 462 if (addr != last_addr && 463 (UnguardOnExecutionViolation > 1 || os::address_is_in_vm(addr))) { 464 465 // Set memory to RWX and retry 466 address page_start = 467 (address) align_size_down((intptr_t) addr, (intptr_t) page_size); 468 bool res = os::protect_memory((char*) page_start, page_size, 469 os::MEM_PROT_RWX); 470 471 if (PrintMiscellaneous && Verbose) { 472 char buf[256]; 473 jio_snprintf(buf, sizeof(buf), "Execution protection violation " 474 "at " INTPTR_FORMAT 475 ", unguarding " INTPTR_FORMAT ": %s, errno=%d", addr, 476 page_start, (res ? "success" : "failed"), errno); 477 tty->print_raw_cr(buf); 478 } 479 stub = pc; 480 481 // Set last_addr so if we fault again at the same address, we don't end 482 // up in an endless loop. 483 // 484 // There are two potential complications here. Two threads trapping at 485 // the same address at the same time could cause one of the threads to 486 // think it already unguarded, and abort the VM. Likely very rare. 487 // 488 // The other race involves two threads alternately trapping at 489 // different addresses and failing to unguard the page, resulting in 490 // an endless loop. This condition is probably even more unlikely than 491 // the first. 492 // 493 // Although both cases could be avoided by using locks or thread local 494 // last_addr, these solutions are unnecessary complication: this 495 // handler is a best-effort safety net, not a complete solution. It is 496 // disabled by default and should only be used as a workaround in case 497 // we missed any no-execute-unsafe VM code. 498 499 last_addr = addr; 500 } 501 } 502 } 503#endif // !AMD64 504 505 if (stub != NULL) { 506 // save all thread context in case we need to restore it 507 if (thread != NULL) thread->set_saved_exception_pc(pc); 508 509 uc->uc_mcontext.gregs[REG_PC] = (greg_t)stub; 510 return true; 511 } 512 513 // signal-chaining 514 if (os::Linux::chained_handler(sig, info, ucVoid)) { 515 return true; 516 } 517 518 if (!abort_if_unrecognized) { 519 // caller wants another chance, so give it to him 520 return false; 521 } 522 523 if (pc == NULL && uc != NULL) { 524 pc = os::Linux::ucontext_get_pc(uc); 525 } 526 527 // unmask current signal 528 sigset_t newset; 529 sigemptyset(&newset); 530 sigaddset(&newset, sig); 531 sigprocmask(SIG_UNBLOCK, &newset, NULL); 532 533 VMError err(t, sig, pc, info, ucVoid); 534 err.report_and_die(); 535 536 ShouldNotReachHere(); 537} 538 539void os::Linux::init_thread_fpu_state(void) { 540#ifndef AMD64 541 // set fpu to 53 bit precision 542 set_fpu_control_word(0x27f); 543#endif // !AMD64 544} 545 546int os::Linux::get_fpu_control_word(void) { 547#ifdef AMD64 548 return 0; 549#else 550 int fpu_control; 551 _FPU_GETCW(fpu_control); 552 return fpu_control & 0xffff; 553#endif // AMD64 554} 555 556void os::Linux::set_fpu_control_word(int fpu_control) { 557#ifndef AMD64 558 _FPU_SETCW(fpu_control); 559#endif // !AMD64 560} 561 562// Check that the linux kernel version is 2.4 or higher since earlier 563// versions do not support SSE without patches. 564bool os::supports_sse() { 565#ifdef AMD64 566 return true; 567#else 568 struct utsname uts; 569 if( uname(&uts) != 0 ) return false; // uname fails? 570 char *minor_string; 571 int major = strtol(uts.release,&minor_string,10); 572 int minor = strtol(minor_string+1,NULL,10); 573 bool result = (major > 2 || (major==2 && minor >= 4)); 574#ifndef PRODUCT 575 if (PrintMiscellaneous && Verbose) { 576 tty->print("OS version is %d.%d, which %s support SSE/SSE2\n", 577 major,minor, result ? "DOES" : "does NOT"); 578 } 579#endif 580 return result; 581#endif // AMD64 582} 583 584bool os::is_allocatable(size_t bytes) { 585#ifdef AMD64 586 // unused on amd64? 587 return true; 588#else 589 590 if (bytes < 2 * G) { 591 return true; 592 } 593 594 char* addr = reserve_memory(bytes, NULL); 595 596 if (addr != NULL) { 597 release_memory(addr, bytes); 598 } 599 600 return addr != NULL; 601#endif // AMD64 602} 603 604//////////////////////////////////////////////////////////////////////////////// 605// thread stack 606 607#ifdef AMD64 608size_t os::Linux::min_stack_allowed = 64 * K; 609 610// amd64: pthread on amd64 is always in floating stack mode 611bool os::Linux::supports_variable_stack_size() { return true; } 612#else 613size_t os::Linux::min_stack_allowed = (48 DEBUG_ONLY(+4))*K; 614 615#ifdef __GNUC__ 616#define GET_GS() ({int gs; __asm__ volatile("movw %%gs, %w0":"=q"(gs)); gs&0xffff;}) 617#endif 618 619// Test if pthread library can support variable thread stack size. LinuxThreads 620// in fixed stack mode allocates 2M fixed slot for each thread. LinuxThreads 621// in floating stack mode and NPTL support variable stack size. 622bool os::Linux::supports_variable_stack_size() { 623 if (os::Linux::is_NPTL()) { 624 // NPTL, yes 625 return true; 626 627 } else { 628 // Note: We can't control default stack size when creating a thread. 629 // If we use non-default stack size (pthread_attr_setstacksize), both 630 // floating stack and non-floating stack LinuxThreads will return the 631 // same value. This makes it impossible to implement this function by 632 // detecting thread stack size directly. 633 // 634 // An alternative approach is to check %gs. Fixed-stack LinuxThreads 635 // do not use %gs, so its value is 0. Floating-stack LinuxThreads use 636 // %gs (either as LDT selector or GDT selector, depending on kernel) 637 // to access thread specific data. 638 // 639 // Note that %gs is a reserved glibc register since early 2001, so 640 // applications are not allowed to change its value (Ulrich Drepper from 641 // Redhat confirmed that all known offenders have been modified to use 642 // either %fs or TSD). In the worst case scenario, when VM is embedded in 643 // a native application that plays with %gs, we might see non-zero %gs 644 // even LinuxThreads is running in fixed stack mode. As the result, we'll 645 // return true and skip _thread_safety_check(), so we may not be able to 646 // detect stack-heap collisions. But otherwise it's harmless. 647 // 648#ifdef __GNUC__ 649 return (GET_GS() != 0); 650#else 651 return false; 652#endif 653 } 654} 655#endif // AMD64 656 657// return default stack size for thr_type 658size_t os::Linux::default_stack_size(os::ThreadType thr_type) { 659 // default stack size (compiler thread needs larger stack) 660#ifdef AMD64 661 size_t s = (thr_type == os::compiler_thread ? 4 * M : 1 * M); 662#else 663 size_t s = (thr_type == os::compiler_thread ? 2 * M : 512 * K); 664#endif // AMD64 665 return s; 666} 667 668size_t os::Linux::default_guard_size(os::ThreadType thr_type) { 669 // Creating guard page is very expensive. Java thread has HotSpot 670 // guard page, only enable glibc guard page for non-Java threads. 671 return (thr_type == java_thread ? 0 : page_size()); 672} 673 674// Java thread: 675// 676// Low memory addresses 677// +------------------------+ 678// | |\ JavaThread created by VM does not have glibc 679// | glibc guard page | - guard, attached Java thread usually has 680// | |/ 1 page glibc guard. 681// P1 +------------------------+ Thread::stack_base() - Thread::stack_size() 682// | |\ 683// | HotSpot Guard Pages | - red and yellow pages 684// | |/ 685// +------------------------+ JavaThread::stack_yellow_zone_base() 686// | |\ 687// | Normal Stack | - 688// | |/ 689// P2 +------------------------+ Thread::stack_base() 690// 691// Non-Java thread: 692// 693// Low memory addresses 694// +------------------------+ 695// | |\ 696// | glibc guard page | - usually 1 page 697// | |/ 698// P1 +------------------------+ Thread::stack_base() - Thread::stack_size() 699// | |\ 700// | Normal Stack | - 701// | |/ 702// P2 +------------------------+ Thread::stack_base() 703// 704// ** P1 (aka bottom) and size ( P2 = P1 - size) are the address and stack size returned from 705// pthread_attr_getstack() 706 707static void current_stack_region(address * bottom, size_t * size) { 708 if (os::Linux::is_initial_thread()) { 709 // initial thread needs special handling because pthread_getattr_np() 710 // may return bogus value. 711 *bottom = os::Linux::initial_thread_stack_bottom(); 712 *size = os::Linux::initial_thread_stack_size(); 713 } else { 714 pthread_attr_t attr; 715 716 int rslt = pthread_getattr_np(pthread_self(), &attr); 717 718 // JVM needs to know exact stack location, abort if it fails 719 if (rslt != 0) { 720 if (rslt == ENOMEM) { 721 vm_exit_out_of_memory(0, OOM_MMAP_ERROR, "pthread_getattr_np"); 722 } else { 723 fatal(err_msg("pthread_getattr_np failed with errno = %d", rslt)); 724 } 725 } 726 727 if (pthread_attr_getstack(&attr, (void **)bottom, size) != 0) { 728 fatal("Can not locate current stack attributes!"); 729 } 730 731 pthread_attr_destroy(&attr); 732 733 } 734 assert(os::current_stack_pointer() >= *bottom && 735 os::current_stack_pointer() < *bottom + *size, "just checking"); 736} 737 738address os::current_stack_base() { 739 address bottom; 740 size_t size; 741 current_stack_region(&bottom, &size); 742 return (bottom + size); 743} 744 745size_t os::current_stack_size() { 746 // stack size includes normal stack and HotSpot guard pages 747 address bottom; 748 size_t size; 749 current_stack_region(&bottom, &size); 750 return size; 751} 752 753///////////////////////////////////////////////////////////////////////////// 754// helper functions for fatal error handler 755 756void os::print_context(outputStream *st, void *context) { 757 if (context == NULL) return; 758 759 ucontext_t *uc = (ucontext_t*)context; 760 st->print_cr("Registers:"); 761#ifdef AMD64 762 st->print( "RAX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RAX]); 763 st->print(", RBX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RBX]); 764 st->print(", RCX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RCX]); 765 st->print(", RDX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RDX]); 766 st->cr(); 767 st->print( "RSP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RSP]); 768 st->print(", RBP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RBP]); 769 st->print(", RSI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RSI]); 770 st->print(", RDI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RDI]); 771 st->cr(); 772 st->print( "R8 =" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R8]); 773 st->print(", R9 =" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R9]); 774 st->print(", R10=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R10]); 775 st->print(", R11=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R11]); 776 st->cr(); 777 st->print( "R12=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R12]); 778 st->print(", R13=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R13]); 779 st->print(", R14=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R14]); 780 st->print(", R15=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R15]); 781 st->cr(); 782 st->print( "RIP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RIP]); 783 st->print(", EFLAGS=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EFL]); 784 st->print(", CSGSFS=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_CSGSFS]); 785 st->print(", ERR=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_ERR]); 786 st->cr(); 787 st->print(" TRAPNO=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_TRAPNO]); 788#else 789 st->print( "EAX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EAX]); 790 st->print(", EBX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EBX]); 791 st->print(", ECX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_ECX]); 792 st->print(", EDX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EDX]); 793 st->cr(); 794 st->print( "ESP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_UESP]); 795 st->print(", EBP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EBP]); 796 st->print(", ESI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_ESI]); 797 st->print(", EDI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EDI]); 798 st->cr(); 799 st->print( "EIP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EIP]); 800 st->print(", EFLAGS=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EFL]); 801 st->print(", CR2=" INTPTR_FORMAT, uc->uc_mcontext.cr2); 802#endif // AMD64 803 st->cr(); 804 st->cr(); 805 806 intptr_t *sp = (intptr_t *)os::Linux::ucontext_get_sp(uc); 807 st->print_cr("Top of Stack: (sp=" PTR_FORMAT ")", sp); 808 print_hex_dump(st, (address)sp, (address)(sp + 8*sizeof(intptr_t)), sizeof(intptr_t)); 809 st->cr(); 810 811 // Note: it may be unsafe to inspect memory near pc. For example, pc may 812 // point to garbage if entry point in an nmethod is corrupted. Leave 813 // this at the end, and hope for the best. 814 address pc = os::Linux::ucontext_get_pc(uc); 815 st->print_cr("Instructions: (pc=" PTR_FORMAT ")", pc); 816 print_hex_dump(st, pc - 32, pc + 32, sizeof(char)); 817} 818 819void os::print_register_info(outputStream *st, void *context) { 820 if (context == NULL) return; 821 822 ucontext_t *uc = (ucontext_t*)context; 823 824 st->print_cr("Register to memory mapping:"); 825 st->cr(); 826 827 // this is horrendously verbose but the layout of the registers in the 828 // context does not match how we defined our abstract Register set, so 829 // we can't just iterate through the gregs area 830 831 // this is only for the "general purpose" registers 832 833#ifdef AMD64 834 st->print("RAX="); print_location(st, uc->uc_mcontext.gregs[REG_RAX]); 835 st->print("RBX="); print_location(st, uc->uc_mcontext.gregs[REG_RBX]); 836 st->print("RCX="); print_location(st, uc->uc_mcontext.gregs[REG_RCX]); 837 st->print("RDX="); print_location(st, uc->uc_mcontext.gregs[REG_RDX]); 838 st->print("RSP="); print_location(st, uc->uc_mcontext.gregs[REG_RSP]); 839 st->print("RBP="); print_location(st, uc->uc_mcontext.gregs[REG_RBP]); 840 st->print("RSI="); print_location(st, uc->uc_mcontext.gregs[REG_RSI]); 841 st->print("RDI="); print_location(st, uc->uc_mcontext.gregs[REG_RDI]); 842 st->print("R8 ="); print_location(st, uc->uc_mcontext.gregs[REG_R8]); 843 st->print("R9 ="); print_location(st, uc->uc_mcontext.gregs[REG_R9]); 844 st->print("R10="); print_location(st, uc->uc_mcontext.gregs[REG_R10]); 845 st->print("R11="); print_location(st, uc->uc_mcontext.gregs[REG_R11]); 846 st->print("R12="); print_location(st, uc->uc_mcontext.gregs[REG_R12]); 847 st->print("R13="); print_location(st, uc->uc_mcontext.gregs[REG_R13]); 848 st->print("R14="); print_location(st, uc->uc_mcontext.gregs[REG_R14]); 849 st->print("R15="); print_location(st, uc->uc_mcontext.gregs[REG_R15]); 850#else 851 st->print("EAX="); print_location(st, uc->uc_mcontext.gregs[REG_EAX]); 852 st->print("EBX="); print_location(st, uc->uc_mcontext.gregs[REG_EBX]); 853 st->print("ECX="); print_location(st, uc->uc_mcontext.gregs[REG_ECX]); 854 st->print("EDX="); print_location(st, uc->uc_mcontext.gregs[REG_EDX]); 855 st->print("ESP="); print_location(st, uc->uc_mcontext.gregs[REG_ESP]); 856 st->print("EBP="); print_location(st, uc->uc_mcontext.gregs[REG_EBP]); 857 st->print("ESI="); print_location(st, uc->uc_mcontext.gregs[REG_ESI]); 858 st->print("EDI="); print_location(st, uc->uc_mcontext.gregs[REG_EDI]); 859#endif // AMD64 860 861 st->cr(); 862} 863 864void os::setup_fpu() { 865#ifndef AMD64 866 address fpu_cntrl = StubRoutines::addr_fpu_cntrl_wrd_std(); 867 __asm__ volatile ( "fldcw (%0)" : 868 : "r" (fpu_cntrl) : "memory"); 869#endif // !AMD64 870} 871 872#ifndef PRODUCT 873void os::verify_stack_alignment() { 874#ifdef AMD64 875 assert(((intptr_t)os::current_stack_pointer() & (StackAlignmentInBytes-1)) == 0, "incorrect stack alignment"); 876#endif 877} 878#endif 879 880 881/* 882 * IA32 only: execute code at a high address in case buggy NX emulation is present. I.e. avoid CS limit 883 * updates (JDK-8023956). 884 */ 885void os::workaround_expand_exec_shield_cs_limit() { 886#if defined(IA32) 887 size_t page_size = os::vm_page_size(); 888 /* 889 * Take the highest VA the OS will give us and exec 890 * 891 * Although using -(pagesz) as mmap hint works on newer kernel as you would 892 * think, older variants affected by this work-around don't (search forward only). 893 * 894 * On the affected distributions, we understand the memory layout to be: 895 * 896 * TASK_LIMIT= 3G, main stack base close to TASK_LIMT. 897 * 898 * A few pages south main stack will do it. 899 * 900 * If we are embedded in an app other than launcher (initial != main stack), 901 * we don't have much control or understanding of the address space, just let it slide. 902 */ 903 char* hint = (char*) (Linux::initial_thread_stack_bottom() - 904 ((StackYellowPages + StackRedPages + 1) * page_size)); 905 char* codebuf = os::reserve_memory(page_size, hint); 906 if ( (codebuf == NULL) || (!os::commit_memory(codebuf, page_size, true)) ) { 907 return; // No matter, we tried, best effort. 908 } 909 if (PrintMiscellaneous && (Verbose || WizardMode)) { 910 tty->print_cr("[CS limit NX emulation work-around, exec code at: %p]", codebuf); 911 } 912 913 // Some code to exec: the 'ret' instruction 914 codebuf[0] = 0xC3; 915 916 // Call the code in the codebuf 917 __asm__ volatile("call *%0" : : "r"(codebuf)); 918 919 // keep the page mapped so CS limit isn't reduced. 920#endif 921} 922