1 /*
2 * Copyright (c) 1999, 2013, 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 address os::current_stack_pointer() {
93 #ifdef SPARC_WORKS
94 register void *esp;
95 __asm__("mov %%"SPELL_REG_SP", %0":"=r"(esp));
96 return (address) ((char*)esp + sizeof(long)*2);
97 #elif defined(__clang__)
98 intptr_t* esp;
99 __asm__ __volatile__ ("mov %%"SPELL_REG_SP", %0":"=r"(esp):);
100 return (address) esp;
101 #else
102 register void *esp __asm__ (SPELL_REG_SP);
103 return (address) esp;
104 #endif
105 }
106
107 char* os::non_memory_address_word() {
108 // Must never look like an address returned by reserve_memory,
109 // even in its subfields (as defined by the CPU immediate fields,
110 // if the CPU splits constants across multiple instructions).
111
112 return (char*) -1;
113 }
114
115 void os::initialize_thread(Thread* thr) {
116 // Nothing to do.
117 }
118
119 address os::Linux::ucontext_get_pc(ucontext_t * uc) {
120 return (address)uc->uc_mcontext.gregs[REG_PC];
121 }
122
123 intptr_t* os::Linux::ucontext_get_sp(ucontext_t * uc) {
124 return (intptr_t*)uc->uc_mcontext.gregs[REG_SP];
125 }
126
127 intptr_t* os::Linux::ucontext_get_fp(ucontext_t * uc) {
128 return (intptr_t*)uc->uc_mcontext.gregs[REG_FP];
129 }
130
131 // For Forte Analyzer AsyncGetCallTrace profiling support - thread
132 // is currently interrupted by SIGPROF.
133 // os::Solaris::fetch_frame_from_ucontext() tries to skip nested signal
134 // frames. Currently we don't do that on Linux, so it's the same as
135 // os::fetch_frame_from_context().
136 ExtendedPC os::Linux::fetch_frame_from_ucontext(Thread* thread,
137 ucontext_t* uc, intptr_t** ret_sp, intptr_t** ret_fp) {
138
139 assert(thread != NULL, "just checking");
140 assert(ret_sp != NULL, "just checking");
141 assert(ret_fp != NULL, "just checking");
142
143 return os::fetch_frame_from_context(uc, ret_sp, ret_fp);
144 }
145
146 ExtendedPC os::fetch_frame_from_context(void* ucVoid,
147 intptr_t** ret_sp, intptr_t** ret_fp) {
148
149 ExtendedPC epc;
150 ucontext_t* uc = (ucontext_t*)ucVoid;
151
152 if (uc != NULL) {
153 epc = ExtendedPC(os::Linux::ucontext_get_pc(uc));
154 if (ret_sp) *ret_sp = os::Linux::ucontext_get_sp(uc);
155 if (ret_fp) *ret_fp = os::Linux::ucontext_get_fp(uc);
156 } else {
157 // construct empty ExtendedPC for return value checking
158 epc = ExtendedPC(NULL);
159 if (ret_sp) *ret_sp = (intptr_t *)NULL;
160 if (ret_fp) *ret_fp = (intptr_t *)NULL;
161 }
162
163 return epc;
164 }
165
166 frame os::fetch_frame_from_context(void* ucVoid) {
167 intptr_t* sp;
168 intptr_t* fp;
169 ExtendedPC epc = fetch_frame_from_context(ucVoid, &sp, &fp);
170 return frame(sp, fp, epc.pc());
171 }
172
173 // By default, gcc always save frame pointer (%ebp/%rbp) on stack. It may get
174 // turned off by -fomit-frame-pointer,
175 frame os::get_sender_for_C_frame(frame* fr) {
176 return frame(fr->sender_sp(), fr->link(), fr->sender_pc());
177 }
178
179 intptr_t* _get_previous_fp() {
180 #ifdef SPARC_WORKS
181 register intptr_t **ebp;
182 __asm__("mov %%"SPELL_REG_FP", %0":"=r"(ebp));
183 #elif defined(__clang__)
184 intptr_t **ebp;
185 __asm__ __volatile__ ("mov %%"SPELL_REG_FP", %0":"=r"(ebp):);
186 #else
187 register intptr_t **ebp __asm__ (SPELL_REG_FP);
188 #endif
189 return (intptr_t*) *ebp; // we want what it points to.
190 }
191
192
193 frame os::current_frame() {
194 intptr_t* fp = _get_previous_fp();
195 frame myframe((intptr_t*)os::current_stack_pointer(),
196 (intptr_t*)fp,
197 CAST_FROM_FN_PTR(address, os::current_frame));
198 if (os::is_first_C_frame(&myframe)) {
199 // stack is not walkable
200 return frame();
201 } else {
202 return os::get_sender_for_C_frame(&myframe);
203 }
204 }
205
206 // Utility functions
207
208 // From IA32 System Programming Guide
209 enum {
210 trap_page_fault = 0xE
211 };
212
213 extern "C" JNIEXPORT int
214 JVM_handle_linux_signal(int sig,
215 siginfo_t* info,
216 void* ucVoid,
217 int abort_if_unrecognized) {
218 ucontext_t* uc = (ucontext_t*) ucVoid;
219
220 Thread* t = ThreadLocalStorage::get_thread_slow();
221
222 // Must do this before SignalHandlerMark, if crash protection installed we will longjmp away
223 // (no destructors can be run)
224 os::WatcherThreadCrashProtection::check_crash_protection(sig, t);
225
226 SignalHandlerMark shm(t);
227
228 // Note: it's not uncommon that JNI code uses signal/sigset to install
229 // then restore certain signal handler (e.g. to temporarily block SIGPIPE,
230 // or have a SIGILL handler when detecting CPU type). When that happens,
231 // JVM_handle_linux_signal() might be invoked with junk info/ucVoid. To
232 // avoid unnecessary crash when libjsig is not preloaded, try handle signals
233 // that do not require siginfo/ucontext first.
234
235 if (sig == SIGPIPE || sig == SIGXFSZ) {
236 // allow chained handler to go first
237 if (os::Linux::chained_handler(sig, info, ucVoid)) {
238 return true;
239 } else {
240 if (PrintMiscellaneous && (WizardMode || Verbose)) {
241 char buf[64];
242 warning("Ignoring %s - see bugs 4229104 or 646499219",
243 os::exception_name(sig, buf, sizeof(buf)));
244 }
245 return true;
246 }
247 }
248
249 JavaThread* thread = NULL;
250 VMThread* vmthread = NULL;
251 if (os::Linux::signal_handlers_are_installed) {
252 if (t != NULL ){
253 if(t->is_Java_thread()) {
254 thread = (JavaThread*)t;
255 }
256 else if(t->is_VM_thread()){
257 vmthread = (VMThread *)t;
258 }
259 }
260 }
261 /*
262 NOTE: does not seem to work on linux.
263 if (info == NULL || info->si_code <= 0 || info->si_code == SI_NOINFO) {
264 // can't decode this kind of signal
265 info = NULL;
266 } else {
267 assert(sig == info->si_signo, "bad siginfo");
268 }
269 */
270 // decide if this trap can be handled by a stub
271 address stub = NULL;
272
273 address pc = NULL;
274
275 //%note os_trap_1
276 if (info != NULL && uc != NULL && thread != NULL) {
277 pc = (address) os::Linux::ucontext_get_pc(uc);
278
279 if (StubRoutines::is_safefetch_fault(pc)) {
280 uc->uc_mcontext.gregs[REG_PC] = intptr_t(StubRoutines::continuation_for_safefetch_fault(pc));
281 return 1;
282 }
283
284 #ifndef AMD64
285 // Halt if SI_KERNEL before more crashes get misdiagnosed as Java bugs
286 // This can happen in any running code (currently more frequently in
287 // interpreter code but has been seen in compiled code)
288 if (sig == SIGSEGV && info->si_addr == 0 && info->si_code == SI_KERNEL) {
289 fatal("An irrecoverable SI_KERNEL SIGSEGV has occurred due "
290 "to unstable signal handling in this distribution.");
291 }
292 #endif // AMD64
293
294 // Handle ALL stack overflow variations here
295 if (sig == SIGSEGV) {
296 address addr = (address) info->si_addr;
297
298 // check if fault address is within thread stack
299 if (addr < thread->stack_base() &&
300 addr >= thread->stack_base() - thread->stack_size()) {
301 // stack overflow
302 if (thread->in_stack_yellow_zone(addr)) {
303 thread->disable_stack_yellow_zone();
304 if (thread->thread_state() == _thread_in_Java) {
305 // Throw a stack overflow exception. Guard pages will be reenabled
306 // while unwinding the stack.
307 stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::STACK_OVERFLOW);
308 } else {
309 // Thread was in the vm or native code. Return and try to finish.
310 return 1;
311 }
312 } else if (thread->in_stack_red_zone(addr)) {
313 // Fatal red zone violation. Disable the guard pages and fall through
314 // to handle_unexpected_exception way down below.
315 thread->disable_stack_red_zone();
316 tty->print_raw_cr("An irrecoverable stack overflow has occurred.");
317
318 // This is a likely cause, but hard to verify. Let's just print
319 // it as a hint.
320 tty->print_raw_cr("Please check if any of your loaded .so files has "
321 "enabled executable stack (see man page execstack(8))");
322 } else {
323 // Accessing stack address below sp may cause SEGV if current
324 // thread has MAP_GROWSDOWN stack. This should only happen when
325 // current thread was created by user code with MAP_GROWSDOWN flag
326 // and then attached to VM. See notes in os_linux.cpp.
327 if (thread->osthread()->expanding_stack() == 0) {
328 thread->osthread()->set_expanding_stack();
329 if (os::Linux::manually_expand_stack(thread, addr)) {
330 thread->osthread()->clear_expanding_stack();
331 return 1;
332 }
333 thread->osthread()->clear_expanding_stack();
334 } else {
335 fatal("recursive segv. expanding stack.");
336 }
337 }
338 }
339 }
340
341 if ((sig == SIGSEGV) && VM_Version::is_cpuinfo_segv_addr(pc)) {
342 // Verify that OS save/restore AVX registers.
343 stub = VM_Version::cpuinfo_cont_addr();
344 }
345
346 if (thread->thread_state() == _thread_in_Java) {
347 // Java thread running in Java code => find exception handler if any
348 // a fault inside compiled code, the interpreter, or a stub
349
350 if (sig == SIGSEGV && os::is_poll_address((address)info->si_addr)) {
351 stub = SharedRuntime::get_poll_stub(pc);
352 } else if (sig == SIGBUS /* && info->si_code == BUS_OBJERR */) {
353 // BugId 4454115: A read from a MappedByteBuffer can fault
354 // here if the underlying file has been truncated.
355 // Do not crash the VM in such a case.
356 CodeBlob* cb = CodeCache::find_blob_unsafe(pc);
357 nmethod* nm = (cb != NULL && cb->is_nmethod()) ? (nmethod*)cb : NULL;
358 if (nm != NULL && nm->has_unsafe_access()) {
359 stub = StubRoutines::handler_for_unsafe_access();
360 }
361 }
362 else
363
364 #ifdef AMD64
365 if (sig == SIGFPE &&
366 (info->si_code == FPE_INTDIV || info->si_code == FPE_FLTDIV)) {
367 stub =
368 SharedRuntime::
369 continuation_for_implicit_exception(thread,
370 pc,
371 SharedRuntime::
372 IMPLICIT_DIVIDE_BY_ZERO);
373 #else
374 if (sig == SIGFPE /* && info->si_code == FPE_INTDIV */) {
375 // HACK: si_code does not work on linux 2.2.12-20!!!
376 int op = pc[0];
377 if (op == 0xDB) {
378 // FIST
379 // TODO: The encoding of D2I in i486.ad can cause an exception
380 // prior to the fist instruction if there was an invalid operation
381 // pending. We want to dismiss that exception. From the win_32
382 // side it also seems that if it really was the fist causing
383 // the exception that we do the d2i by hand with different
384 // rounding. Seems kind of weird.
385 // NOTE: that we take the exception at the NEXT floating point instruction.
386 assert(pc[0] == 0xDB, "not a FIST opcode");
387 assert(pc[1] == 0x14, "not a FIST opcode");
388 assert(pc[2] == 0x24, "not a FIST opcode");
389 return true;
390 } else if (op == 0xF7) {
391 // IDIV
392 stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_DIVIDE_BY_ZERO);
393 } else {
394 // TODO: handle more cases if we are using other x86 instructions
395 // that can generate SIGFPE signal on linux.
396 tty->print_cr("unknown opcode 0x%X with SIGFPE.", op);
397 fatal("please update this code.");
398 }
399 #endif // AMD64
400 } else if (sig == SIGSEGV &&
401 !MacroAssembler::needs_explicit_null_check((intptr_t)info->si_addr)) {
402 // Determination of interpreter/vtable stub/compiled code null exception
403 stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_NULL);
404 }
405 } else if (thread->thread_state() == _thread_in_vm &&
406 sig == SIGBUS && /* info->si_code == BUS_OBJERR && */
407 thread->doing_unsafe_access()) {
408 stub = StubRoutines::handler_for_unsafe_access();
409 }
410
411 // jni_fast_Get<Primitive>Field can trap at certain pc's if a GC kicks in
412 // and the heap gets shrunk before the field access.
413 if ((sig == SIGSEGV) || (sig == SIGBUS)) {
414 address addr = JNI_FastGetField::find_slowcase_pc(pc);
415 if (addr != (address)-1) {
416 stub = addr;
417 }
418 }
419
420 // Check to see if we caught the safepoint code in the
421 // process of write protecting the memory serialization page.
422 // It write enables the page immediately after protecting it
423 // so we can just return to retry the write.
424 if ((sig == SIGSEGV) &&
425 os::is_memory_serialize_page(thread, (address) info->si_addr)) {
426 // Block current thread until the memory serialize page permission restored.
427 os::block_on_serialize_page_trap();
428 return true;
429 }
430 }
431
432 #ifndef AMD64
433 // Execution protection violation
434 //
435 // This should be kept as the last step in the triage. We don't
436 // have a dedicated trap number for a no-execute fault, so be
437 // conservative and allow other handlers the first shot.
438 //
439 // Note: We don't test that info->si_code == SEGV_ACCERR here.
440 // this si_code is so generic that it is almost meaningless; and
441 // the si_code for this condition may change in the future.
442 // Furthermore, a false-positive should be harmless.
443 if (UnguardOnExecutionViolation > 0 &&
444 (sig == SIGSEGV || sig == SIGBUS) &&
445 uc->uc_mcontext.gregs[REG_TRAPNO] == trap_page_fault) {
446 int page_size = os::vm_page_size();
447 address addr = (address) info->si_addr;
448 address pc = os::Linux::ucontext_get_pc(uc);
449 // Make sure the pc and the faulting address are sane.
450 //
451 // If an instruction spans a page boundary, and the page containing
452 // the beginning of the instruction is executable but the following
453 // page is not, the pc and the faulting address might be slightly
454 // different - we still want to unguard the 2nd page in this case.
455 //
456 // 15 bytes seems to be a (very) safe value for max instruction size.
457 bool pc_is_near_addr =
458 (pointer_delta((void*) addr, (void*) pc, sizeof(char)) < 15);
459 bool instr_spans_page_boundary =
460 (align_size_down((intptr_t) pc ^ (intptr_t) addr,
461 (intptr_t) page_size) > 0);
462
463 if (pc == addr || (pc_is_near_addr && instr_spans_page_boundary)) {
464 static volatile address last_addr =
465 (address) os::non_memory_address_word();
466
467 // In conservative mode, don't unguard unless the address is in the VM
468 if (addr != last_addr &&
469 (UnguardOnExecutionViolation > 1 || os::address_is_in_vm(addr))) {
470
471 // Set memory to RWX and retry
472 address page_start =
473 (address) align_size_down((intptr_t) addr, (intptr_t) page_size);
474 bool res = os::protect_memory((char*) page_start, page_size,
475 os::MEM_PROT_RWX);
476
477 if (PrintMiscellaneous && Verbose) {
478 char buf[256];
479 jio_snprintf(buf, sizeof(buf), "Execution protection violation "
480 "at " INTPTR_FORMAT
481 ", unguarding " INTPTR_FORMAT ": %s, errno=%d", addr,
482 page_start, (res ? "success" : "failed"), errno);
483 tty->print_raw_cr(buf);
484 }
485 stub = pc;
486
487 // Set last_addr so if we fault again at the same address, we don't end
488 // up in an endless loop.
489 //
490 // There are two potential complications here. Two threads trapping at
491 // the same address at the same time could cause one of the threads to
492 // think it already unguarded, and abort the VM. Likely very rare.
493 //
494 // The other race involves two threads alternately trapping at
495 // different addresses and failing to unguard the page, resulting in
496 // an endless loop. This condition is probably even more unlikely than
497 // the first.
498 //
499 // Although both cases could be avoided by using locks or thread local
500 // last_addr, these solutions are unnecessary complication: this
501 // handler is a best-effort safety net, not a complete solution. It is
502 // disabled by default and should only be used as a workaround in case
503 // we missed any no-execute-unsafe VM code.
504
505 last_addr = addr;
506 }
507 }
508 }
509 #endif // !AMD64
510
511 if (stub != NULL) {
512 // save all thread context in case we need to restore it
513 if (thread != NULL) thread->set_saved_exception_pc(pc);
514
515 uc->uc_mcontext.gregs[REG_PC] = (greg_t)stub;
516 return true;
517 }
518
519 // signal-chaining
520 if (os::Linux::chained_handler(sig, info, ucVoid)) {
521 return true;
522 }
523
524 if (!abort_if_unrecognized) {
525 // caller wants another chance, so give it to him
526 return false;
527 }
528
529 if (pc == NULL && uc != NULL) {
530 pc = os::Linux::ucontext_get_pc(uc);
531 }
532
533 // unmask current signal
534 sigset_t newset;
535 sigemptyset(&newset);
536 sigaddset(&newset, sig);
537 sigprocmask(SIG_UNBLOCK, &newset, NULL);
538
539 VMError err(t, sig, pc, info, ucVoid);
540 err.report_and_die();
541
542 ShouldNotReachHere();
543 }
544
545 void os::Linux::init_thread_fpu_state(void) {
546 #ifndef AMD64
547 // set fpu to 53 bit precision
548 set_fpu_control_word(0x27f);
549 #endif // !AMD64
550 }
551
552 int os::Linux::get_fpu_control_word(void) {
553 #ifdef AMD64
554 return 0;
555 #else
556 int fpu_control;
557 _FPU_GETCW(fpu_control);
558 return fpu_control & 0xffff;
559 #endif // AMD64
560 }
561
562 void os::Linux::set_fpu_control_word(int fpu_control) {
563 #ifndef AMD64
564 _FPU_SETCW(fpu_control);
565 #endif // !AMD64
566 }
567
568 // Check that the linux kernel version is 2.4 or higher since earlier
569 // versions do not support SSE without patches.
570 bool os::supports_sse() {
571 #ifdef AMD64
572 return true;
573 #else
574 struct utsname uts;
575 if( uname(&uts) != 0 ) return false; // uname fails?
576 char *minor_string;
577 int major = strtol(uts.release,&minor_string,10);
578 int minor = strtol(minor_string+1,NULL,10);
579 bool result = (major > 2 || (major==2 && minor >= 4));
580 #ifndef PRODUCT
581 if (PrintMiscellaneous && Verbose) {
582 tty->print("OS version is %d.%d, which %s support SSE/SSE2\n",
583 major,minor, result ? "DOES" : "does NOT");
584 }
585 #endif
586 return result;
587 #endif // AMD64
588 }
589
590 bool os::is_allocatable(size_t bytes) {
591 #ifdef AMD64
592 // unused on amd64?
593 return true;
594 #else
595
596 if (bytes < 2 * G) {
597 return true;
598 }
599
600 char* addr = reserve_memory(bytes, NULL);
601
602 if (addr != NULL) {
603 release_memory(addr, bytes);
604 }
605
606 return addr != NULL;
607 #endif // AMD64
608 }
609
610 ////////////////////////////////////////////////////////////////////////////////
611 // thread stack
612
613 #ifdef AMD64
614 size_t os::Linux::min_stack_allowed = 64 * K;
615
616 // amd64: pthread on amd64 is always in floating stack mode
617 bool os::Linux::supports_variable_stack_size() { return true; }
618 #else
619 size_t os::Linux::min_stack_allowed = (48 DEBUG_ONLY(+4))*K;
620
621 #ifdef __GNUC__
622 #define GET_GS() ({int gs; __asm__ volatile("movw %%gs, %w0":"=q"(gs)); gs&0xffff;})
623 #endif
624
625 // Test if pthread library can support variable thread stack size. LinuxThreads
626 // in fixed stack mode allocates 2M fixed slot for each thread. LinuxThreads
627 // in floating stack mode and NPTL support variable stack size.
628 bool os::Linux::supports_variable_stack_size() {
629 if (os::Linux::is_NPTL()) {
630 // NPTL, yes
631 return true;
632
633 } else {
634 // Note: We can't control default stack size when creating a thread.
635 // If we use non-default stack size (pthread_attr_setstacksize), both
636 // floating stack and non-floating stack LinuxThreads will return the
637 // same value. This makes it impossible to implement this function by
638 // detecting thread stack size directly.
639 //
640 // An alternative approach is to check %gs. Fixed-stack LinuxThreads
641 // do not use %gs, so its value is 0. Floating-stack LinuxThreads use
642 // %gs (either as LDT selector or GDT selector, depending on kernel)
643 // to access thread specific data.
644 //
645 // Note that %gs is a reserved glibc register since early 2001, so
646 // applications are not allowed to change its value (Ulrich Drepper from
647 // Redhat confirmed that all known offenders have been modified to use
648 // either %fs or TSD). In the worst case scenario, when VM is embedded in
649 // a native application that plays with %gs, we might see non-zero %gs
650 // even LinuxThreads is running in fixed stack mode. As the result, we'll
651 // return true and skip _thread_safety_check(), so we may not be able to
652 // detect stack-heap collisions. But otherwise it's harmless.
653 //
654 #ifdef __GNUC__
655 return (GET_GS() != 0);
656 #else
657 return false;
658 #endif
659 }
660 }
661 #endif // AMD64
662
663 // return default stack size for thr_type
664 size_t os::Linux::default_stack_size(os::ThreadType thr_type) {
665 // default stack size (compiler thread needs larger stack)
666 #ifdef AMD64
667 size_t s = (thr_type == os::compiler_thread ? 4 * M : 1 * M);
668 #else
669 size_t s = (thr_type == os::compiler_thread ? 2 * M : 512 * K);
670 #endif // AMD64
671 return s;
672 }
673
674 size_t os::Linux::default_guard_size(os::ThreadType thr_type) {
675 // Creating guard page is very expensive. Java thread has HotSpot
676 // guard page, only enable glibc guard page for non-Java threads.
677 return (thr_type == java_thread ? 0 : page_size());
678 }
679
680 // Java thread:
681 //
682 // Low memory addresses
683 // +------------------------+
684 // | |\ JavaThread created by VM does not have glibc
685 // | glibc guard page | - guard, attached Java thread usually has
686 // | |/ 1 page glibc guard.
687 // P1 +------------------------+ Thread::stack_base() - Thread::stack_size()
688 // | |\
689 // | HotSpot Guard Pages | - red and yellow pages
690 // | |/
691 // +------------------------+ JavaThread::stack_yellow_zone_base()
692 // | |\
693 // | Normal Stack | -
694 // | |/
695 // P2 +------------------------+ Thread::stack_base()
696 //
697 // Non-Java thread:
698 //
699 // Low memory addresses
700 // +------------------------+
701 // | |\
702 // | glibc guard page | - usually 1 page
703 // | |/
704 // P1 +------------------------+ Thread::stack_base() - Thread::stack_size()
705 // | |\
706 // | Normal Stack | -
707 // | |/
708 // P2 +------------------------+ Thread::stack_base()
709 //
710 // ** P1 (aka bottom) and size ( P2 = P1 - size) are the address and stack size returned from
711 // pthread_attr_getstack()
712
713 static void current_stack_region(address * bottom, size_t * size) {
714 if (os::Linux::is_initial_thread()) {
715 // initial thread needs special handling because pthread_getattr_np()
716 // may return bogus value.
717 *bottom = os::Linux::initial_thread_stack_bottom();
718 *size = os::Linux::initial_thread_stack_size();
719 } else {
720 pthread_attr_t attr;
721
722 int rslt = pthread_getattr_np(pthread_self(), &attr);
723
724 // JVM needs to know exact stack location, abort if it fails
725 if (rslt != 0) {
726 if (rslt == ENOMEM) {
727 vm_exit_out_of_memory(0, OOM_MMAP_ERROR, "pthread_getattr_np");
728 } else {
729 fatal(err_msg("pthread_getattr_np failed with errno = %d", rslt));
730 }
731 }
732
733 if (pthread_attr_getstack(&attr, (void **)bottom, size) != 0) {
734 fatal("Can not locate current stack attributes!");
735 }
736
737 pthread_attr_destroy(&attr);
738
739 }
740 assert(os::current_stack_pointer() >= *bottom &&
741 os::current_stack_pointer() < *bottom + *size, "just checking");
742 }
743
744 address os::current_stack_base() {
745 address bottom;
746 size_t size;
747 current_stack_region(&bottom, &size);
748 return (bottom + size);
749 }
750
751 size_t os::current_stack_size() {
752 // stack size includes normal stack and HotSpot guard pages
753 address bottom;
754 size_t size;
755 current_stack_region(&bottom, &size);
756 return size;
757 }
758
759 /////////////////////////////////////////////////////////////////////////////
760 // helper functions for fatal error handler
761
762 void os::print_context(outputStream *st, void *context) {
763 if (context == NULL) return;
764
765 ucontext_t *uc = (ucontext_t*)context;
766 st->print_cr("Registers:");
767 #ifdef AMD64
768 st->print( "RAX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RAX]);
769 st->print(", RBX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RBX]);
770 st->print(", RCX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RCX]);
771 st->print(", RDX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RDX]);
772 st->cr();
773 st->print( "RSP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RSP]);
774 st->print(", RBP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RBP]);
775 st->print(", RSI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RSI]);
776 st->print(", RDI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RDI]);
777 st->cr();
778 st->print( "R8 =" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R8]);
779 st->print(", R9 =" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R9]);
780 st->print(", R10=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R10]);
781 st->print(", R11=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R11]);
782 st->cr();
783 st->print( "R12=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R12]);
784 st->print(", R13=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R13]);
785 st->print(", R14=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R14]);
786 st->print(", R15=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R15]);
787 st->cr();
788 st->print( "RIP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RIP]);
789 st->print(", EFLAGS=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EFL]);
790 st->print(", CSGSFS=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_CSGSFS]);
791 st->print(", ERR=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_ERR]);
792 st->cr();
793 st->print(" TRAPNO=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_TRAPNO]);
794 #else
795 st->print( "EAX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EAX]);
796 st->print(", EBX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EBX]);
797 st->print(", ECX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_ECX]);
798 st->print(", EDX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EDX]);
799 st->cr();
800 st->print( "ESP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_UESP]);
801 st->print(", EBP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EBP]);
802 st->print(", ESI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_ESI]);
803 st->print(", EDI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EDI]);
804 st->cr();
805 st->print( "EIP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EIP]);
806 st->print(", EFLAGS=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EFL]);
807 st->print(", CR2=" INTPTR_FORMAT, uc->uc_mcontext.cr2);
808 #endif // AMD64
809 st->cr();
810 st->cr();
811
812 intptr_t *sp = (intptr_t *)os::Linux::ucontext_get_sp(uc);
813 st->print_cr("Top of Stack: (sp=" PTR_FORMAT ")", sp);
814 print_hex_dump(st, (address)sp, (address)(sp + 8*sizeof(intptr_t)), sizeof(intptr_t));
815 st->cr();
816
817 // Note: it may be unsafe to inspect memory near pc. For example, pc may
818 // point to garbage if entry point in an nmethod is corrupted. Leave
819 // this at the end, and hope for the best.
820 address pc = os::Linux::ucontext_get_pc(uc);
821 st->print_cr("Instructions: (pc=" PTR_FORMAT ")", pc);
822 print_hex_dump(st, pc - 32, pc + 32, sizeof(char));
823 }
824
825 void os::print_register_info(outputStream *st, void *context) {
826 if (context == NULL) return;
827
828 ucontext_t *uc = (ucontext_t*)context;
829
830 st->print_cr("Register to memory mapping:");
831 st->cr();
832
833 // this is horrendously verbose but the layout of the registers in the
834 // context does not match how we defined our abstract Register set, so
835 // we can't just iterate through the gregs area
836
837 // this is only for the "general purpose" registers
838
839 #ifdef AMD64
840 st->print("RAX="); print_location(st, uc->uc_mcontext.gregs[REG_RAX]);
841 st->print("RBX="); print_location(st, uc->uc_mcontext.gregs[REG_RBX]);
842 st->print("RCX="); print_location(st, uc->uc_mcontext.gregs[REG_RCX]);
843 st->print("RDX="); print_location(st, uc->uc_mcontext.gregs[REG_RDX]);
844 st->print("RSP="); print_location(st, uc->uc_mcontext.gregs[REG_RSP]);
845 st->print("RBP="); print_location(st, uc->uc_mcontext.gregs[REG_RBP]);
846 st->print("RSI="); print_location(st, uc->uc_mcontext.gregs[REG_RSI]);
847 st->print("RDI="); print_location(st, uc->uc_mcontext.gregs[REG_RDI]);
848 st->print("R8 ="); print_location(st, uc->uc_mcontext.gregs[REG_R8]);
849 st->print("R9 ="); print_location(st, uc->uc_mcontext.gregs[REG_R9]);
850 st->print("R10="); print_location(st, uc->uc_mcontext.gregs[REG_R10]);
851 st->print("R11="); print_location(st, uc->uc_mcontext.gregs[REG_R11]);
852 st->print("R12="); print_location(st, uc->uc_mcontext.gregs[REG_R12]);
853 st->print("R13="); print_location(st, uc->uc_mcontext.gregs[REG_R13]);
854 st->print("R14="); print_location(st, uc->uc_mcontext.gregs[REG_R14]);
855 st->print("R15="); print_location(st, uc->uc_mcontext.gregs[REG_R15]);
856 #else
857 st->print("EAX="); print_location(st, uc->uc_mcontext.gregs[REG_EAX]);
858 st->print("EBX="); print_location(st, uc->uc_mcontext.gregs[REG_EBX]);
859 st->print("ECX="); print_location(st, uc->uc_mcontext.gregs[REG_ECX]);
860 st->print("EDX="); print_location(st, uc->uc_mcontext.gregs[REG_EDX]);
861 st->print("ESP="); print_location(st, uc->uc_mcontext.gregs[REG_ESP]);
862 st->print("EBP="); print_location(st, uc->uc_mcontext.gregs[REG_EBP]);
863 st->print("ESI="); print_location(st, uc->uc_mcontext.gregs[REG_ESI]);
864 st->print("EDI="); print_location(st, uc->uc_mcontext.gregs[REG_EDI]);
865 #endif // AMD64
866
867 st->cr();
868 }
869
870 void os::setup_fpu() {
871 #ifndef AMD64
872 address fpu_cntrl = StubRoutines::addr_fpu_cntrl_wrd_std();
873 __asm__ volatile ( "fldcw (%0)" :
874 : "r" (fpu_cntrl) : "memory");
875 #endif // !AMD64
876 }
877
878 #ifndef PRODUCT
879 void os::verify_stack_alignment() {
880 #ifdef AMD64
881 assert(((intptr_t)os::current_stack_pointer() & (StackAlignmentInBytes-1)) == 0, "incorrect stack alignment");
882 #endif
883 }
884 #endif
885
886
887 /*
888 * IA32 only: execute code at a high address in case buggy NX emulation is present. I.e. avoid CS limit
889 * updates (JDK-8023956).
890 */
891 void os::workaround_expand_exec_shield_cs_limit() {
892 #if defined(IA32)
893 size_t page_size = os::vm_page_size();
894 /*
895 * Take the highest VA the OS will give us and exec
896 *
897 * Although using -(pagesz) as mmap hint works on newer kernel as you would
898 * think, older variants affected by this work-around don't (search forward only).
899 *
900 * On the affected distributions, we understand the memory layout to be:
901 *
902 * TASK_LIMIT= 3G, main stack base close to TASK_LIMT.
903 *
904 * A few pages south main stack will do it.
905 *
906 * If we are embedded in an app other than launcher (initial != main stack),
907 * we don't have much control or understanding of the address space, just let it slide.
908 */
909 char* hint = (char*) (Linux::initial_thread_stack_bottom() -
910 ((StackYellowPages + StackRedPages + 1) * page_size));
911 char* codebuf = os::reserve_memory(page_size, hint);
912 if ( (codebuf == NULL) || (!os::commit_memory(codebuf, page_size, true)) ) {
913 return; // No matter, we tried, best effort.
914 }
915
916 MemTracker::record_virtual_memory_type((address)codebuf, mtInternal);
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 }