1 /*
2 * Copyright (c) 1999, 2019, 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
91 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
92
93 address os::current_stack_pointer() {
94 #ifdef SPARC_WORKS
95 register void *esp;
96 __asm__("mov %%"SPELL_REG_SP", %0":"=r"(esp));
97 return (address) ((char*)esp + sizeof(long)*2);
98 #elif defined(__clang__)
99 intptr_t* esp;
100 __asm__ __volatile__ ("mov %%"SPELL_REG_SP", %0":"=r"(esp):);
101 return (address) esp;
102 #else
103 register void *esp __asm__ (SPELL_REG_SP);
104 return (address) esp;
105 #endif
106 }
107
108 char* os::non_memory_address_word() {
109 // Must never look like an address returned by reserve_memory,
110 // even in its subfields (as defined by the CPU immediate fields,
111 // if the CPU splits constants across multiple instructions).
112
113 return (char*) -1;
114 }
115
116 void os::initialize_thread(Thread* thr) {
117 // Nothing to do.
118 }
119
120 address os::Linux::ucontext_get_pc(ucontext_t * uc) {
121 return (address)uc->uc_mcontext.gregs[REG_PC];
122 }
123
124 intptr_t* os::Linux::ucontext_get_sp(ucontext_t * uc) {
125 return (intptr_t*)uc->uc_mcontext.gregs[REG_SP];
126 }
127
128 intptr_t* os::Linux::ucontext_get_fp(ucontext_t * uc) {
129 return (intptr_t*)uc->uc_mcontext.gregs[REG_FP];
130 }
131
132 // For Forte Analyzer AsyncGetCallTrace profiling support - thread
133 // is currently interrupted by SIGPROF.
134 // os::Solaris::fetch_frame_from_ucontext() tries to skip nested signal
135 // frames. Currently we don't do that on Linux, so it's the same as
136 // os::fetch_frame_from_context().
137 ExtendedPC os::Linux::fetch_frame_from_ucontext(Thread* thread,
138 ucontext_t* uc, intptr_t** ret_sp, intptr_t** ret_fp) {
139
140 assert(thread != NULL, "just checking");
141 assert(ret_sp != NULL, "just checking");
142 assert(ret_fp != NULL, "just checking");
143
144 return os::fetch_frame_from_context(uc, ret_sp, ret_fp);
145 }
146
147 ExtendedPC os::fetch_frame_from_context(void* ucVoid,
148 intptr_t** ret_sp, intptr_t** ret_fp) {
149
150 ExtendedPC epc;
151 ucontext_t* uc = (ucontext_t*)ucVoid;
152
153 if (uc != NULL) {
154 epc = ExtendedPC(os::Linux::ucontext_get_pc(uc));
155 if (ret_sp) *ret_sp = os::Linux::ucontext_get_sp(uc);
156 if (ret_fp) *ret_fp = os::Linux::ucontext_get_fp(uc);
157 } else {
158 // construct empty ExtendedPC for return value checking
159 epc = ExtendedPC(NULL);
160 if (ret_sp) *ret_sp = (intptr_t *)NULL;
161 if (ret_fp) *ret_fp = (intptr_t *)NULL;
162 }
163
164 return epc;
165 }
166
167 frame os::fetch_frame_from_context(void* ucVoid) {
168 intptr_t* sp;
169 intptr_t* fp;
170 ExtendedPC epc = fetch_frame_from_context(ucVoid, &sp, &fp);
171 return frame(sp, fp, epc.pc());
172 }
173
174 // By default, gcc always save frame pointer (%ebp/%rbp) on stack. It may get
175 // turned off by -fomit-frame-pointer,
176 frame os::get_sender_for_C_frame(frame* fr) {
177 return frame(fr->sender_sp(), fr->link(), fr->sender_pc());
178 }
179
180 intptr_t* _get_previous_fp() {
181 #ifdef SPARC_WORKS
182 register intptr_t **ebp;
183 __asm__("mov %%"SPELL_REG_FP", %0":"=r"(ebp));
184 #elif defined(__clang__)
185 intptr_t **ebp;
186 __asm__ __volatile__ ("mov %%"SPELL_REG_FP", %0":"=r"(ebp):);
187 #else
188 register intptr_t **ebp __asm__ (SPELL_REG_FP);
189 #endif
190 return (intptr_t*) *ebp; // we want what it points to.
191 }
192
193
194 frame os::current_frame() {
195 intptr_t* fp = _get_previous_fp();
196 frame myframe((intptr_t*)os::current_stack_pointer(),
197 (intptr_t*)fp,
198 CAST_FROM_FN_PTR(address, os::current_frame));
199 if (os::is_first_C_frame(&myframe)) {
200 // stack is not walkable
201 return frame();
202 } else {
203 return os::get_sender_for_C_frame(&myframe);
204 }
205 }
206
207 // Utility functions
208
209 // From IA32 System Programming Guide
210 enum {
211 trap_page_fault = 0xE
212 };
213
214 extern "C" JNIEXPORT int
215 JVM_handle_linux_signal(int sig,
216 siginfo_t* info,
217 void* ucVoid,
218 int abort_if_unrecognized) {
219 ucontext_t* uc = (ucontext_t*) ucVoid;
220
221 Thread* t = ThreadLocalStorage::get_thread_slow();
222
223 // Must do this before SignalHandlerMark, if crash protection installed we will longjmp away
224 // (no destructors can be run)
225 os::WatcherThreadCrashProtection::check_crash_protection(sig, t);
226
227 os::ThreadCrashProtection::check_crash_protection(sig, t);
228
229 SignalHandlerMark shm(t);
230
231 // Note: it's not uncommon that JNI code uses signal/sigset to install
232 // then restore certain signal handler (e.g. to temporarily block SIGPIPE,
233 // or have a SIGILL handler when detecting CPU type). When that happens,
234 // JVM_handle_linux_signal() might be invoked with junk info/ucVoid. To
235 // avoid unnecessary crash when libjsig is not preloaded, try handle signals
236 // that do not require siginfo/ucontext first.
237
238 if (sig == SIGPIPE || sig == SIGXFSZ) {
239 // allow chained handler to go first
240 if (os::Linux::chained_handler(sig, info, ucVoid)) {
241 return true;
242 } else {
243 if (PrintMiscellaneous && (WizardMode || Verbose)) {
244 char buf[64];
245 warning("Ignoring %s - see bugs 4229104 or 646499219",
246 os::exception_name(sig, buf, sizeof(buf)));
247 }
248 return true;
249 }
250 }
251
252 JavaThread* thread = NULL;
253 VMThread* vmthread = NULL;
254 if (os::Linux::signal_handlers_are_installed) {
255 if (t != NULL ){
256 if(t->is_Java_thread()) {
257 thread = (JavaThread*)t;
258 }
259 else if(t->is_VM_thread()){
260 vmthread = (VMThread *)t;
261 }
262 }
263 }
264 /*
265 NOTE: does not seem to work on linux.
266 if (info == NULL || info->si_code <= 0 || info->si_code == SI_NOINFO) {
267 // can't decode this kind of signal
268 info = NULL;
269 } else {
270 assert(sig == info->si_signo, "bad siginfo");
271 }
272 */
273 // decide if this trap can be handled by a stub
274 address stub = NULL;
275
276 address pc = NULL;
277
278 //%note os_trap_1
279 if (info != NULL && uc != NULL && thread != NULL) {
280 pc = (address) os::Linux::ucontext_get_pc(uc);
281
282 if (StubRoutines::is_safefetch_fault(pc)) {
283 uc->uc_mcontext.gregs[REG_PC] = intptr_t(StubRoutines::continuation_for_safefetch_fault(pc));
284 return 1;
285 }
286
287 #ifndef AMD64
288 // Halt if SI_KERNEL before more crashes get misdiagnosed as Java bugs
289 // This can happen in any running code (currently more frequently in
290 // interpreter code but has been seen in compiled code)
291 if (sig == SIGSEGV && info->si_addr == 0 && info->si_code == SI_KERNEL) {
292 fatal("An irrecoverable SI_KERNEL SIGSEGV has occurred due "
293 "to unstable signal handling in this distribution.");
294 }
295 #endif // AMD64
296
297 // Handle ALL stack overflow variations here
298 if (sig == SIGSEGV) {
299 address addr = (address) info->si_addr;
300
301 // check if fault address is within thread stack
302 if (addr < thread->stack_base() &&
303 addr >= thread->stack_base() - thread->stack_size()) {
304 // stack overflow
305 if (thread->in_stack_yellow_zone(addr)) {
306 thread->disable_stack_yellow_zone();
307 if (thread->thread_state() == _thread_in_Java) {
308 // Throw a stack overflow exception. Guard pages will be reenabled
309 // while unwinding the stack.
310 stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::STACK_OVERFLOW);
311 } else {
312 // Thread was in the vm or native code. Return and try to finish.
313 return 1;
314 }
315 } else if (thread->in_stack_red_zone(addr)) {
316 // Fatal red zone violation. Disable the guard pages and fall through
317 // to handle_unexpected_exception way down below.
318 thread->disable_stack_red_zone();
319 tty->print_raw_cr("An irrecoverable stack overflow has occurred.");
320
321 // This is a likely cause, but hard to verify. Let's just print
322 // it as a hint.
323 tty->print_raw_cr("Please check if any of your loaded .so files has "
324 "enabled executable stack (see man page execstack(8))");
325 } else {
326 // Accessing stack address below sp may cause SEGV if current
327 // thread has MAP_GROWSDOWN stack. This should only happen when
328 // current thread was created by user code with MAP_GROWSDOWN flag
329 // and then attached to VM. See notes in os_linux.cpp.
330 if (thread->osthread()->expanding_stack() == 0) {
331 thread->osthread()->set_expanding_stack();
332 if (os::Linux::manually_expand_stack(thread, addr)) {
333 thread->osthread()->clear_expanding_stack();
334 return 1;
335 }
336 thread->osthread()->clear_expanding_stack();
337 } else {
338 fatal("recursive segv. expanding stack.");
339 }
340 }
341 }
342 }
343
344 if ((sig == SIGSEGV) && VM_Version::is_cpuinfo_segv_addr(pc)) {
345 // Verify that OS save/restore AVX registers.
346 stub = VM_Version::cpuinfo_cont_addr();
347 }
348
349 if (thread->thread_state() == _thread_in_Java) {
350 // Java thread running in Java code => find exception handler if any
351 // a fault inside compiled code, the interpreter, or a stub
352
353 if (sig == SIGSEGV && os::is_poll_address((address)info->si_addr)) {
354 stub = SharedRuntime::get_poll_stub(pc);
355 } else if (sig == SIGBUS /* && info->si_code == BUS_OBJERR */) {
356 // BugId 4454115: A read from a MappedByteBuffer can fault
357 // here if the underlying file has been truncated.
358 // Do not crash the VM in such a case.
359 CodeBlob* cb = CodeCache::find_blob_unsafe(pc);
360 nmethod* nm = (cb != NULL && cb->is_nmethod()) ? (nmethod*)cb : NULL;
361 if (nm != NULL && nm->has_unsafe_access()) {
362 stub = StubRoutines::handler_for_unsafe_access();
363 }
364 }
365 else
366
367 #ifdef AMD64
368 if (sig == SIGFPE &&
369 (info->si_code == FPE_INTDIV || info->si_code == FPE_FLTDIV)) {
370 stub =
371 SharedRuntime::
372 continuation_for_implicit_exception(thread,
373 pc,
374 SharedRuntime::
375 IMPLICIT_DIVIDE_BY_ZERO);
376 #else
377 if (sig == SIGFPE /* && info->si_code == FPE_INTDIV */) {
378 // HACK: si_code does not work on linux 2.2.12-20!!!
379 int op = pc[0];
380 if (op == 0xDB) {
381 // FIST
382 // TODO: The encoding of D2I in i486.ad can cause an exception
383 // prior to the fist instruction if there was an invalid operation
384 // pending. We want to dismiss that exception. From the win_32
385 // side it also seems that if it really was the fist causing
386 // the exception that we do the d2i by hand with different
387 // rounding. Seems kind of weird.
388 // NOTE: that we take the exception at the NEXT floating point instruction.
389 assert(pc[0] == 0xDB, "not a FIST opcode");
390 assert(pc[1] == 0x14, "not a FIST opcode");
391 assert(pc[2] == 0x24, "not a FIST opcode");
392 return true;
393 } else if (op == 0xF7) {
394 // IDIV
395 stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_DIVIDE_BY_ZERO);
396 } else {
397 // TODO: handle more cases if we are using other x86 instructions
398 // that can generate SIGFPE signal on linux.
399 tty->print_cr("unknown opcode 0x%X with SIGFPE.", op);
400 fatal("please update this code.");
401 }
402 #endif // AMD64
403 } else if (sig == SIGSEGV &&
404 !MacroAssembler::needs_explicit_null_check((intptr_t)info->si_addr)) {
405 // Determination of interpreter/vtable stub/compiled code null exception
406 stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_NULL);
407 }
408 } else if (thread->thread_state() == _thread_in_vm &&
409 sig == SIGBUS && /* info->si_code == BUS_OBJERR && */
410 thread->doing_unsafe_access()) {
411 stub = StubRoutines::handler_for_unsafe_access();
412 }
413
414 // jni_fast_Get<Primitive>Field can trap at certain pc's if a GC kicks in
415 // and the heap gets shrunk before the field access.
416 if ((sig == SIGSEGV) || (sig == SIGBUS)) {
417 address addr = JNI_FastGetField::find_slowcase_pc(pc);
418 if (addr != (address)-1) {
419 stub = addr;
420 }
421 }
422
423 // Check to see if we caught the safepoint code in the
424 // process of write protecting the memory serialization page.
425 // It write enables the page immediately after protecting it
426 // so we can just return to retry the write.
427 if ((sig == SIGSEGV) &&
428 os::is_memory_serialize_page(thread, (address) info->si_addr)) {
429 // Block current thread until the memory serialize page permission restored.
430 os::block_on_serialize_page_trap();
431 return true;
432 }
433 }
434
435 #ifndef AMD64
436 // Execution protection violation
437 //
438 // This should be kept as the last step in the triage. We don't
439 // have a dedicated trap number for a no-execute fault, so be
440 // conservative and allow other handlers the first shot.
441 //
442 // Note: We don't test that info->si_code == SEGV_ACCERR here.
443 // this si_code is so generic that it is almost meaningless; and
444 // the si_code for this condition may change in the future.
445 // Furthermore, a false-positive should be harmless.
446 if (UnguardOnExecutionViolation > 0 &&
447 (sig == SIGSEGV || sig == SIGBUS) &&
448 uc->uc_mcontext.gregs[REG_TRAPNO] == trap_page_fault) {
449 int page_size = os::vm_page_size();
450 address addr = (address) info->si_addr;
451 address pc = os::Linux::ucontext_get_pc(uc);
452 // Make sure the pc and the faulting address are sane.
453 //
454 // If an instruction spans a page boundary, and the page containing
455 // the beginning of the instruction is executable but the following
456 // page is not, the pc and the faulting address might be slightly
457 // different - we still want to unguard the 2nd page in this case.
458 //
459 // 15 bytes seems to be a (very) safe value for max instruction size.
460 bool pc_is_near_addr =
461 (pointer_delta((void*) addr, (void*) pc, sizeof(char)) < 15);
462 bool instr_spans_page_boundary =
463 (align_size_down((intptr_t) pc ^ (intptr_t) addr,
464 (intptr_t) page_size) > 0);
465
466 if (pc == addr || (pc_is_near_addr && instr_spans_page_boundary)) {
467 static volatile address last_addr =
468 (address) os::non_memory_address_word();
469
470 // In conservative mode, don't unguard unless the address is in the VM
471 if (addr != last_addr &&
472 (UnguardOnExecutionViolation > 1 || os::address_is_in_vm(addr))) {
473
474 // Set memory to RWX and retry
475 address page_start =
476 (address) align_size_down((intptr_t) addr, (intptr_t) page_size);
477 bool res = os::protect_memory((char*) page_start, page_size,
478 os::MEM_PROT_RWX);
479
480 if (PrintMiscellaneous && Verbose) {
481 char buf[256];
482 jio_snprintf(buf, sizeof(buf), "Execution protection violation "
483 "at " INTPTR_FORMAT
484 ", unguarding " INTPTR_FORMAT ": %s, errno=%d", addr,
485 page_start, (res ? "success" : "failed"), errno);
486 tty->print_raw_cr(buf);
487 }
488 stub = pc;
489
490 // Set last_addr so if we fault again at the same address, we don't end
491 // up in an endless loop.
492 //
493 // There are two potential complications here. Two threads trapping at
494 // the same address at the same time could cause one of the threads to
495 // think it already unguarded, and abort the VM. Likely very rare.
496 //
497 // The other race involves two threads alternately trapping at
498 // different addresses and failing to unguard the page, resulting in
499 // an endless loop. This condition is probably even more unlikely than
500 // the first.
501 //
502 // Although both cases could be avoided by using locks or thread local
503 // last_addr, these solutions are unnecessary complication: this
504 // handler is a best-effort safety net, not a complete solution. It is
505 // disabled by default and should only be used as a workaround in case
506 // we missed any no-execute-unsafe VM code.
507
508 last_addr = addr;
509 }
510 }
511 }
512 #endif // !AMD64
513
514 if (stub != NULL) {
515 // save all thread context in case we need to restore it
516 if (thread != NULL) thread->set_saved_exception_pc(pc);
517
518 uc->uc_mcontext.gregs[REG_PC] = (greg_t)stub;
519 return true;
520 }
521
522 // signal-chaining
523 if (os::Linux::chained_handler(sig, info, ucVoid)) {
524 return true;
525 }
526
527 if (!abort_if_unrecognized) {
528 // caller wants another chance, so give it to him
529 return false;
530 }
531
532 if (pc == NULL && uc != NULL) {
533 pc = os::Linux::ucontext_get_pc(uc);
534 }
535
536 // unmask current signal
537 sigset_t newset;
538 sigemptyset(&newset);
539 sigaddset(&newset, sig);
540 sigprocmask(SIG_UNBLOCK, &newset, NULL);
541
542 VMError err(t, sig, pc, info, ucVoid);
543 err.report_and_die();
544
545 ShouldNotReachHere();
546 }
547
548 void os::Linux::init_thread_fpu_state(void) {
549 #ifndef AMD64
550 // set fpu to 53 bit precision
551 set_fpu_control_word(0x27f);
552 #endif // !AMD64
553 }
554
555 int os::Linux::get_fpu_control_word(void) {
556 #ifdef AMD64
557 return 0;
558 #else
559 int fpu_control;
560 _FPU_GETCW(fpu_control);
561 return fpu_control & 0xffff;
562 #endif // AMD64
563 }
564
565 void os::Linux::set_fpu_control_word(int fpu_control) {
566 #ifndef AMD64
567 _FPU_SETCW(fpu_control);
568 #endif // !AMD64
569 }
570
571 // Check that the linux kernel version is 2.4 or higher since earlier
572 // versions do not support SSE without patches.
573 bool os::supports_sse() {
574 #ifdef AMD64
575 return true;
576 #else
577 struct utsname uts;
578 if( uname(&uts) != 0 ) return false; // uname fails?
579 char *minor_string;
580 int major = strtol(uts.release,&minor_string,10);
581 int minor = strtol(minor_string+1,NULL,10);
582 bool result = (major > 2 || (major==2 && minor >= 4));
583 #ifndef PRODUCT
584 if (PrintMiscellaneous && Verbose) {
585 tty->print("OS version is %d.%d, which %s support SSE/SSE2\n",
586 major,minor, result ? "DOES" : "does NOT");
587 }
588 #endif
589 return result;
590 #endif // AMD64
591 }
592
593 bool os::is_allocatable(size_t bytes) {
594 #ifdef AMD64
595 // unused on amd64?
596 return true;
597 #else
598
599 if (bytes < 2 * G) {
600 return true;
601 }
602
603 char* addr = reserve_memory(bytes, NULL);
604
605 if (addr != NULL) {
606 release_memory(addr, bytes);
607 }
608
609 return addr != NULL;
610 #endif // AMD64
611 }
612
613 ////////////////////////////////////////////////////////////////////////////////
614 // thread stack
615
616 #ifdef AMD64
617 size_t os::Linux::min_stack_allowed = 64 * K;
618
619 // amd64: pthread on amd64 is always in floating stack mode
620 bool os::Linux::supports_variable_stack_size() { return true; }
621 #else
622 size_t os::Linux::min_stack_allowed = (48 DEBUG_ONLY(+4))*K;
623
624 #ifdef __GNUC__
625 #define GET_GS() ({int gs; __asm__ volatile("movw %%gs, %w0":"=q"(gs)); gs&0xffff;})
626 #endif
627
628 // Test if pthread library can support variable thread stack size. LinuxThreads
629 // in fixed stack mode allocates 2M fixed slot for each thread. LinuxThreads
630 // in floating stack mode and NPTL support variable stack size.
631 bool os::Linux::supports_variable_stack_size() {
632 if (os::Linux::is_NPTL()) {
633 // NPTL, yes
634 return true;
635
636 } else {
637 // Note: We can't control default stack size when creating a thread.
638 // If we use non-default stack size (pthread_attr_setstacksize), both
639 // floating stack and non-floating stack LinuxThreads will return the
640 // same value. This makes it impossible to implement this function by
641 // detecting thread stack size directly.
642 //
643 // An alternative approach is to check %gs. Fixed-stack LinuxThreads
644 // do not use %gs, so its value is 0. Floating-stack LinuxThreads use
645 // %gs (either as LDT selector or GDT selector, depending on kernel)
646 // to access thread specific data.
647 //
648 // Note that %gs is a reserved glibc register since early 2001, so
649 // applications are not allowed to change its value (Ulrich Drepper from
650 // Redhat confirmed that all known offenders have been modified to use
651 // either %fs or TSD). In the worst case scenario, when VM is embedded in
652 // a native application that plays with %gs, we might see non-zero %gs
653 // even LinuxThreads is running in fixed stack mode. As the result, we'll
654 // return true and skip _thread_safety_check(), so we may not be able to
655 // detect stack-heap collisions. But otherwise it's harmless.
656 //
657 #ifdef __GNUC__
658 return (GET_GS() != 0);
659 #else
660 return false;
661 #endif
662 }
663 }
664 #endif // AMD64
665
666 // return default stack size for thr_type
667 size_t os::Linux::default_stack_size(os::ThreadType thr_type) {
668 // default stack size (compiler thread needs larger stack)
669 #ifdef AMD64
670 size_t s = (thr_type == os::compiler_thread ? 4 * M : 1 * M);
671 #else
672 size_t s = (thr_type == os::compiler_thread ? 2 * M : 512 * K);
673 #endif // AMD64
674 return s;
675 }
676
677 size_t os::Linux::default_guard_size(os::ThreadType thr_type) {
678 // Creating guard page is very expensive. Java thread has HotSpot
679 // guard page, only enable glibc guard page for non-Java threads.
680 return (thr_type == java_thread ? 0 : page_size());
681 }
682
683 // Java thread:
684 //
685 // Low memory addresses
686 // +------------------------+
687 // | |\ JavaThread created by VM does not have glibc
688 // | glibc guard page | - guard, attached Java thread usually has
689 // | |/ 1 page glibc guard.
690 // P1 +------------------------+ Thread::stack_base() - Thread::stack_size()
691 // | |\
692 // | HotSpot Guard Pages | - red and yellow pages
693 // | |/
694 // +------------------------+ JavaThread::stack_yellow_zone_base()
695 // | |\
696 // | Normal Stack | -
697 // | |/
698 // P2 +------------------------+ Thread::stack_base()
699 //
700 // Non-Java thread:
701 //
702 // Low memory addresses
703 // +------------------------+
704 // | |\
705 // | glibc guard page | - usually 1 page
706 // | |/
707 // P1 +------------------------+ Thread::stack_base() - Thread::stack_size()
708 // | |\
709 // | Normal Stack | -
710 // | |/
711 // P2 +------------------------+ Thread::stack_base()
712 //
713 // ** P1 (aka bottom) and size ( P2 = P1 - size) are the address and stack size returned from
714 // pthread_attr_getstack()
715
716 static void current_stack_region(address * bottom, size_t * size) {
717 if (os::is_primordial_thread()) {
718 // primordial thread needs special handling because pthread_getattr_np()
719 // may return bogus value.
720 *bottom = os::Linux::initial_thread_stack_bottom();
721 *size = os::Linux::initial_thread_stack_size();
722 } else {
723 pthread_attr_t attr;
724
725 int rslt = pthread_getattr_np(pthread_self(), &attr);
726
727 // JVM needs to know exact stack location, abort if it fails
728 if (rslt != 0) {
729 if (rslt == ENOMEM) {
730 vm_exit_out_of_memory(0, OOM_MMAP_ERROR, "pthread_getattr_np");
731 } else {
732 fatal(err_msg("pthread_getattr_np failed with errno = %d", rslt));
733 }
734 }
735
736 if (pthread_attr_getstack(&attr, (void **)bottom, size) != 0) {
737 fatal("Can not locate current stack attributes!");
738 }
739
740 pthread_attr_destroy(&attr);
741
742 }
743 assert(os::current_stack_pointer() >= *bottom &&
744 os::current_stack_pointer() < *bottom + *size, "just checking");
745 }
746
747 address os::current_stack_base() {
748 address bottom;
749 size_t size;
750 current_stack_region(&bottom, &size);
751 return (bottom + size);
752 }
753
754 size_t os::current_stack_size() {
755 // stack size includes normal stack and HotSpot guard pages
756 address bottom;
757 size_t size;
758 current_stack_region(&bottom, &size);
759 return size;
760 }
761
762 /////////////////////////////////////////////////////////////////////////////
763 // helper functions for fatal error handler
764
765 void os::print_context(outputStream *st, void *context) {
766 if (context == NULL) return;
767
768 ucontext_t *uc = (ucontext_t*)context;
769 st->print_cr("Registers:");
770 #ifdef AMD64
771 st->print( "RAX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RAX]);
772 st->print(", RBX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RBX]);
773 st->print(", RCX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RCX]);
774 st->print(", RDX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RDX]);
775 st->cr();
776 st->print( "RSP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RSP]);
777 st->print(", RBP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RBP]);
778 st->print(", RSI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RSI]);
779 st->print(", RDI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RDI]);
780 st->cr();
781 st->print( "R8 =" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R8]);
782 st->print(", R9 =" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R9]);
783 st->print(", R10=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R10]);
784 st->print(", R11=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R11]);
785 st->cr();
786 st->print( "R12=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R12]);
787 st->print(", R13=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R13]);
788 st->print(", R14=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R14]);
789 st->print(", R15=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R15]);
790 st->cr();
791 st->print( "RIP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RIP]);
792 st->print(", EFLAGS=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EFL]);
793 st->print(", CSGSFS=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_CSGSFS]);
794 st->print(", ERR=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_ERR]);
795 st->cr();
796 st->print(" TRAPNO=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_TRAPNO]);
797 #else
798 st->print( "EAX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EAX]);
799 st->print(", EBX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EBX]);
800 st->print(", ECX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_ECX]);
801 st->print(", EDX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EDX]);
802 st->cr();
803 st->print( "ESP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_UESP]);
804 st->print(", EBP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EBP]);
805 st->print(", ESI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_ESI]);
806 st->print(", EDI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EDI]);
807 st->cr();
808 st->print( "EIP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EIP]);
809 st->print(", EFLAGS=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EFL]);
810 st->print(", CR2=" INTPTR_FORMAT, uc->uc_mcontext.cr2);
811 #endif // AMD64
812 st->cr();
813 st->cr();
814
815 intptr_t *sp = (intptr_t *)os::Linux::ucontext_get_sp(uc);
816 st->print_cr("Top of Stack: (sp=" PTR_FORMAT ")", sp);
817 print_hex_dump(st, (address)sp, (address)(sp + 8*sizeof(intptr_t)), sizeof(intptr_t));
818 st->cr();
819
820 // Note: it may be unsafe to inspect memory near pc. For example, pc may
821 // point to garbage if entry point in an nmethod is corrupted. Leave
822 // this at the end, and hope for the best.
823 address pc = os::Linux::ucontext_get_pc(uc);
824 st->print_cr("Instructions: (pc=" PTR_FORMAT ")", pc);
825 print_hex_dump(st, pc - 32, pc + 32, sizeof(char));
826 }
827
828 void os::print_register_info(outputStream *st, void *context) {
829 if (context == NULL) return;
830
831 ucontext_t *uc = (ucontext_t*)context;
832
833 st->print_cr("Register to memory mapping:");
834 st->cr();
835
836 // this is horrendously verbose but the layout of the registers in the
837 // context does not match how we defined our abstract Register set, so
838 // we can't just iterate through the gregs area
839
840 // this is only for the "general purpose" registers
841
842 #ifdef AMD64
843 st->print("RAX="); print_location(st, uc->uc_mcontext.gregs[REG_RAX]);
844 st->print("RBX="); print_location(st, uc->uc_mcontext.gregs[REG_RBX]);
845 st->print("RCX="); print_location(st, uc->uc_mcontext.gregs[REG_RCX]);
846 st->print("RDX="); print_location(st, uc->uc_mcontext.gregs[REG_RDX]);
847 st->print("RSP="); print_location(st, uc->uc_mcontext.gregs[REG_RSP]);
848 st->print("RBP="); print_location(st, uc->uc_mcontext.gregs[REG_RBP]);
849 st->print("RSI="); print_location(st, uc->uc_mcontext.gregs[REG_RSI]);
850 st->print("RDI="); print_location(st, uc->uc_mcontext.gregs[REG_RDI]);
851 st->print("R8 ="); print_location(st, uc->uc_mcontext.gregs[REG_R8]);
852 st->print("R9 ="); print_location(st, uc->uc_mcontext.gregs[REG_R9]);
853 st->print("R10="); print_location(st, uc->uc_mcontext.gregs[REG_R10]);
854 st->print("R11="); print_location(st, uc->uc_mcontext.gregs[REG_R11]);
855 st->print("R12="); print_location(st, uc->uc_mcontext.gregs[REG_R12]);
856 st->print("R13="); print_location(st, uc->uc_mcontext.gregs[REG_R13]);
857 st->print("R14="); print_location(st, uc->uc_mcontext.gregs[REG_R14]);
858 st->print("R15="); print_location(st, uc->uc_mcontext.gregs[REG_R15]);
859 #else
860 st->print("EAX="); print_location(st, uc->uc_mcontext.gregs[REG_EAX]);
861 st->print("EBX="); print_location(st, uc->uc_mcontext.gregs[REG_EBX]);
862 st->print("ECX="); print_location(st, uc->uc_mcontext.gregs[REG_ECX]);
863 st->print("EDX="); print_location(st, uc->uc_mcontext.gregs[REG_EDX]);
864 st->print("ESP="); print_location(st, uc->uc_mcontext.gregs[REG_ESP]);
865 st->print("EBP="); print_location(st, uc->uc_mcontext.gregs[REG_EBP]);
866 st->print("ESI="); print_location(st, uc->uc_mcontext.gregs[REG_ESI]);
867 st->print("EDI="); print_location(st, uc->uc_mcontext.gregs[REG_EDI]);
868 #endif // AMD64
869
870 st->cr();
871 }
872
873 void os::setup_fpu() {
874 #ifndef AMD64
875 address fpu_cntrl = StubRoutines::addr_fpu_cntrl_wrd_std();
876 __asm__ volatile ( "fldcw (%0)" :
877 : "r" (fpu_cntrl) : "memory");
878 #endif // !AMD64
879 }
880
881 #ifndef PRODUCT
882 void os::verify_stack_alignment() {
883 #ifdef AMD64
884 assert(((intptr_t)os::current_stack_pointer() & (StackAlignmentInBytes-1)) == 0, "incorrect stack alignment");
885 #endif
886 }
887 #endif
888
889
890 /*
891 * IA32 only: execute code at a high address in case buggy NX emulation is present. I.e. avoid CS limit
892 * updates (JDK-8023956).
893 */
894 void os::workaround_expand_exec_shield_cs_limit() {
895 #if defined(IA32)
896 size_t page_size = os::vm_page_size();
897 /*
898 * Take the highest VA the OS will give us and exec
899 *
900 * Although using -(pagesz) as mmap hint works on newer kernel as you would
901 * think, older variants affected by this work-around don't (search forward only).
902 *
903 * On the affected distributions, we understand the memory layout to be:
904 *
905 * TASK_LIMIT= 3G, main stack base close to TASK_LIMT.
906 *
907 * A few pages south main stack will do it.
908 *
909 * If we are embedded in an app other than launcher (initial != main stack),
910 * we don't have much control or understanding of the address space, just let it slide.
911 */
912 char* hint = (char*) (Linux::initial_thread_stack_bottom() -
913 ((StackYellowPages + StackRedPages + 1) * page_size));
914 char* codebuf = os::attempt_reserve_memory_at(page_size, hint);
915 if ( (codebuf == NULL) || (!os::commit_memory(codebuf, page_size, true)) ) {
916 return; // No matter, we tried, best effort.
917 }
918 if (PrintMiscellaneous && (Verbose || WizardMode)) {
919 tty->print_cr("[CS limit NX emulation work-around, exec code at: %p]", codebuf);
920 }
921
922 // Some code to exec: the 'ret' instruction
923 codebuf[0] = 0xC3;
924
925 // Call the code in the codebuf
926 __asm__ volatile("call *%0" : : "r"(codebuf));
927
928 // keep the page mapped so CS limit isn't reduced.
929 #endif
930 }