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 }