Wed, 17 Jul 2013 13:48:15 +0200
8020701: Avoid crashes in WatcherThread
Reviewed-by: acorn, dcubed, dsimms
1 /*
2 * Copyright (c) 1999, 2012, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
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"
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>
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
91 address os::current_stack_pointer() {
92 #ifdef SPARC_WORKS
93 register void *esp;
94 __asm__("mov %%"SPELL_REG_SP", %0":"=r"(esp));
95 return (address) ((char*)esp + sizeof(long)*2);
96 #elif defined(__clang__)
97 intptr_t* esp;
98 __asm__ __volatile__ ("mov %%"SPELL_REG_SP", %0":"=r"(esp):);
99 return (address) esp;
100 #else
101 register void *esp __asm__ (SPELL_REG_SP);
102 return (address) esp;
103 #endif
104 }
106 char* os::non_memory_address_word() {
107 // Must never look like an address returned by reserve_memory,
108 // even in its subfields (as defined by the CPU immediate fields,
109 // if the CPU splits constants across multiple instructions).
111 return (char*) -1;
112 }
114 void os::initialize_thread(Thread* thr) {
115 // Nothing to do.
116 }
118 address os::Linux::ucontext_get_pc(ucontext_t * uc) {
119 return (address)uc->uc_mcontext.gregs[REG_PC];
120 }
122 intptr_t* os::Linux::ucontext_get_sp(ucontext_t * uc) {
123 return (intptr_t*)uc->uc_mcontext.gregs[REG_SP];
124 }
126 intptr_t* os::Linux::ucontext_get_fp(ucontext_t * uc) {
127 return (intptr_t*)uc->uc_mcontext.gregs[REG_FP];
128 }
130 // For Forte Analyzer AsyncGetCallTrace profiling support - thread
131 // is currently interrupted by SIGPROF.
132 // os::Solaris::fetch_frame_from_ucontext() tries to skip nested signal
133 // frames. Currently we don't do that on Linux, so it's the same as
134 // os::fetch_frame_from_context().
135 ExtendedPC os::Linux::fetch_frame_from_ucontext(Thread* thread,
136 ucontext_t* uc, intptr_t** ret_sp, intptr_t** ret_fp) {
138 assert(thread != NULL, "just checking");
139 assert(ret_sp != NULL, "just checking");
140 assert(ret_fp != NULL, "just checking");
142 return os::fetch_frame_from_context(uc, ret_sp, ret_fp);
143 }
145 ExtendedPC os::fetch_frame_from_context(void* ucVoid,
146 intptr_t** ret_sp, intptr_t** ret_fp) {
148 ExtendedPC epc;
149 ucontext_t* uc = (ucontext_t*)ucVoid;
151 if (uc != NULL) {
152 epc = ExtendedPC(os::Linux::ucontext_get_pc(uc));
153 if (ret_sp) *ret_sp = os::Linux::ucontext_get_sp(uc);
154 if (ret_fp) *ret_fp = os::Linux::ucontext_get_fp(uc);
155 } else {
156 // construct empty ExtendedPC for return value checking
157 epc = ExtendedPC(NULL);
158 if (ret_sp) *ret_sp = (intptr_t *)NULL;
159 if (ret_fp) *ret_fp = (intptr_t *)NULL;
160 }
162 return epc;
163 }
165 frame os::fetch_frame_from_context(void* ucVoid) {
166 intptr_t* sp;
167 intptr_t* fp;
168 ExtendedPC epc = fetch_frame_from_context(ucVoid, &sp, &fp);
169 return frame(sp, fp, epc.pc());
170 }
172 // By default, gcc always save frame pointer (%ebp/%rbp) on stack. It may get
173 // turned off by -fomit-frame-pointer,
174 frame os::get_sender_for_C_frame(frame* fr) {
175 return frame(fr->sender_sp(), fr->link(), fr->sender_pc());
176 }
178 intptr_t* _get_previous_fp() {
179 #ifdef SPARC_WORKS
180 register intptr_t **ebp;
181 __asm__("mov %%"SPELL_REG_FP", %0":"=r"(ebp));
182 #elif defined(__clang__)
183 intptr_t **ebp;
184 __asm__ __volatile__ ("mov %%"SPELL_REG_FP", %0":"=r"(ebp):);
185 #else
186 register intptr_t **ebp __asm__ (SPELL_REG_FP);
187 #endif
188 return (intptr_t*) *ebp; // we want what it points to.
189 }
192 frame os::current_frame() {
193 intptr_t* fp = _get_previous_fp();
194 frame myframe((intptr_t*)os::current_stack_pointer(),
195 (intptr_t*)fp,
196 CAST_FROM_FN_PTR(address, os::current_frame));
197 if (os::is_first_C_frame(&myframe)) {
198 // stack is not walkable
199 return frame();
200 } else {
201 return os::get_sender_for_C_frame(&myframe);
202 }
203 }
205 // Utility functions
207 // From IA32 System Programming Guide
208 enum {
209 trap_page_fault = 0xE
210 };
212 extern "C" void Fetch32PFI () ;
213 extern "C" void Fetch32Resume () ;
214 #ifdef AMD64
215 extern "C" void FetchNPFI () ;
216 extern "C" void FetchNResume () ;
217 #endif // AMD64
219 extern "C" JNIEXPORT int
220 JVM_handle_linux_signal(int sig,
221 siginfo_t* info,
222 void* ucVoid,
223 int abort_if_unrecognized) {
224 ucontext_t* uc = (ucontext_t*) ucVoid;
226 Thread* t = ThreadLocalStorage::get_thread_slow();
228 // Must do this before SignalHandlerMark, if crash protection installed we will longjmp away
229 // (no destructors can be run)
230 os::WatcherThreadCrashProtection::check_crash_protection(sig, t);
232 SignalHandlerMark shm(t);
234 // Note: it's not uncommon that JNI code uses signal/sigset to install
235 // then restore certain signal handler (e.g. to temporarily block SIGPIPE,
236 // or have a SIGILL handler when detecting CPU type). When that happens,
237 // JVM_handle_linux_signal() might be invoked with junk info/ucVoid. To
238 // avoid unnecessary crash when libjsig is not preloaded, try handle signals
239 // that do not require siginfo/ucontext first.
241 if (sig == SIGPIPE || sig == SIGXFSZ) {
242 // allow chained handler to go first
243 if (os::Linux::chained_handler(sig, info, ucVoid)) {
244 return true;
245 } else {
246 if (PrintMiscellaneous && (WizardMode || Verbose)) {
247 char buf[64];
248 warning("Ignoring %s - see bugs 4229104 or 646499219",
249 os::exception_name(sig, buf, sizeof(buf)));
250 }
251 return true;
252 }
253 }
255 JavaThread* thread = NULL;
256 VMThread* vmthread = NULL;
257 if (os::Linux::signal_handlers_are_installed) {
258 if (t != NULL ){
259 if(t->is_Java_thread()) {
260 thread = (JavaThread*)t;
261 }
262 else if(t->is_VM_thread()){
263 vmthread = (VMThread *)t;
264 }
265 }
266 }
267 /*
268 NOTE: does not seem to work on linux.
269 if (info == NULL || info->si_code <= 0 || info->si_code == SI_NOINFO) {
270 // can't decode this kind of signal
271 info = NULL;
272 } else {
273 assert(sig == info->si_signo, "bad siginfo");
274 }
275 */
276 // decide if this trap can be handled by a stub
277 address stub = NULL;
279 address pc = NULL;
281 //%note os_trap_1
282 if (info != NULL && uc != NULL && thread != NULL) {
283 pc = (address) os::Linux::ucontext_get_pc(uc);
285 if (pc == (address) Fetch32PFI) {
286 uc->uc_mcontext.gregs[REG_PC] = intptr_t(Fetch32Resume) ;
287 return 1 ;
288 }
289 #ifdef AMD64
290 if (pc == (address) FetchNPFI) {
291 uc->uc_mcontext.gregs[REG_PC] = intptr_t (FetchNResume) ;
292 return 1 ;
293 }
294 #endif // AMD64
296 #ifndef AMD64
297 // Halt if SI_KERNEL before more crashes get misdiagnosed as Java bugs
298 // This can happen in any running code (currently more frequently in
299 // interpreter code but has been seen in compiled code)
300 if (sig == SIGSEGV && info->si_addr == 0 && info->si_code == SI_KERNEL) {
301 fatal("An irrecoverable SI_KERNEL SIGSEGV has occurred due "
302 "to unstable signal handling in this distribution.");
303 }
304 #endif // AMD64
306 // Handle ALL stack overflow variations here
307 if (sig == SIGSEGV) {
308 address addr = (address) info->si_addr;
310 // check if fault address is within thread stack
311 if (addr < thread->stack_base() &&
312 addr >= thread->stack_base() - thread->stack_size()) {
313 // stack overflow
314 if (thread->in_stack_yellow_zone(addr)) {
315 thread->disable_stack_yellow_zone();
316 if (thread->thread_state() == _thread_in_Java) {
317 // Throw a stack overflow exception. Guard pages will be reenabled
318 // while unwinding the stack.
319 stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::STACK_OVERFLOW);
320 } else {
321 // Thread was in the vm or native code. Return and try to finish.
322 return 1;
323 }
324 } else if (thread->in_stack_red_zone(addr)) {
325 // Fatal red zone violation. Disable the guard pages and fall through
326 // to handle_unexpected_exception way down below.
327 thread->disable_stack_red_zone();
328 tty->print_raw_cr("An irrecoverable stack overflow has occurred.");
330 // This is a likely cause, but hard to verify. Let's just print
331 // it as a hint.
332 tty->print_raw_cr("Please check if any of your loaded .so files has "
333 "enabled executable stack (see man page execstack(8))");
334 } else {
335 // Accessing stack address below sp may cause SEGV if current
336 // thread has MAP_GROWSDOWN stack. This should only happen when
337 // current thread was created by user code with MAP_GROWSDOWN flag
338 // and then attached to VM. See notes in os_linux.cpp.
339 if (thread->osthread()->expanding_stack() == 0) {
340 thread->osthread()->set_expanding_stack();
341 if (os::Linux::manually_expand_stack(thread, addr)) {
342 thread->osthread()->clear_expanding_stack();
343 return 1;
344 }
345 thread->osthread()->clear_expanding_stack();
346 } else {
347 fatal("recursive segv. expanding stack.");
348 }
349 }
350 }
351 }
353 if (thread->thread_state() == _thread_in_Java) {
354 // Java thread running in Java code => find exception handler if any
355 // a fault inside compiled code, the interpreter, or a stub
357 if (sig == SIGSEGV && os::is_poll_address((address)info->si_addr)) {
358 stub = SharedRuntime::get_poll_stub(pc);
359 } else if (sig == SIGBUS /* && info->si_code == BUS_OBJERR */) {
360 // BugId 4454115: A read from a MappedByteBuffer can fault
361 // here if the underlying file has been truncated.
362 // Do not crash the VM in such a case.
363 CodeBlob* cb = CodeCache::find_blob_unsafe(pc);
364 nmethod* nm = (cb != NULL && cb->is_nmethod()) ? (nmethod*)cb : NULL;
365 if (nm != NULL && nm->has_unsafe_access()) {
366 stub = StubRoutines::handler_for_unsafe_access();
367 }
368 }
369 else
371 #ifdef AMD64
372 if (sig == SIGFPE &&
373 (info->si_code == FPE_INTDIV || info->si_code == FPE_FLTDIV)) {
374 stub =
375 SharedRuntime::
376 continuation_for_implicit_exception(thread,
377 pc,
378 SharedRuntime::
379 IMPLICIT_DIVIDE_BY_ZERO);
380 #else
381 if (sig == SIGFPE /* && info->si_code == FPE_INTDIV */) {
382 // HACK: si_code does not work on linux 2.2.12-20!!!
383 int op = pc[0];
384 if (op == 0xDB) {
385 // FIST
386 // TODO: The encoding of D2I in i486.ad can cause an exception
387 // prior to the fist instruction if there was an invalid operation
388 // pending. We want to dismiss that exception. From the win_32
389 // side it also seems that if it really was the fist causing
390 // the exception that we do the d2i by hand with different
391 // rounding. Seems kind of weird.
392 // NOTE: that we take the exception at the NEXT floating point instruction.
393 assert(pc[0] == 0xDB, "not a FIST opcode");
394 assert(pc[1] == 0x14, "not a FIST opcode");
395 assert(pc[2] == 0x24, "not a FIST opcode");
396 return true;
397 } else if (op == 0xF7) {
398 // IDIV
399 stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_DIVIDE_BY_ZERO);
400 } else {
401 // TODO: handle more cases if we are using other x86 instructions
402 // that can generate SIGFPE signal on linux.
403 tty->print_cr("unknown opcode 0x%X with SIGFPE.", op);
404 fatal("please update this code.");
405 }
406 #endif // AMD64
407 } else if (sig == SIGSEGV &&
408 !MacroAssembler::needs_explicit_null_check((intptr_t)info->si_addr)) {
409 // Determination of interpreter/vtable stub/compiled code null exception
410 stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_NULL);
411 }
412 } else if (thread->thread_state() == _thread_in_vm &&
413 sig == SIGBUS && /* info->si_code == BUS_OBJERR && */
414 thread->doing_unsafe_access()) {
415 stub = StubRoutines::handler_for_unsafe_access();
416 }
418 // jni_fast_Get<Primitive>Field can trap at certain pc's if a GC kicks in
419 // and the heap gets shrunk before the field access.
420 if ((sig == SIGSEGV) || (sig == SIGBUS)) {
421 address addr = JNI_FastGetField::find_slowcase_pc(pc);
422 if (addr != (address)-1) {
423 stub = addr;
424 }
425 }
427 // Check to see if we caught the safepoint code in the
428 // process of write protecting the memory serialization page.
429 // It write enables the page immediately after protecting it
430 // so we can just return to retry the write.
431 if ((sig == SIGSEGV) &&
432 os::is_memory_serialize_page(thread, (address) info->si_addr)) {
433 // Block current thread until the memory serialize page permission restored.
434 os::block_on_serialize_page_trap();
435 return true;
436 }
437 }
439 #ifndef AMD64
440 // Execution protection violation
441 //
442 // This should be kept as the last step in the triage. We don't
443 // have a dedicated trap number for a no-execute fault, so be
444 // conservative and allow other handlers the first shot.
445 //
446 // Note: We don't test that info->si_code == SEGV_ACCERR here.
447 // this si_code is so generic that it is almost meaningless; and
448 // the si_code for this condition may change in the future.
449 // Furthermore, a false-positive should be harmless.
450 if (UnguardOnExecutionViolation > 0 &&
451 (sig == SIGSEGV || sig == SIGBUS) &&
452 uc->uc_mcontext.gregs[REG_TRAPNO] == trap_page_fault) {
453 int page_size = os::vm_page_size();
454 address addr = (address) info->si_addr;
455 address pc = os::Linux::ucontext_get_pc(uc);
456 // Make sure the pc and the faulting address are sane.
457 //
458 // If an instruction spans a page boundary, and the page containing
459 // the beginning of the instruction is executable but the following
460 // page is not, the pc and the faulting address might be slightly
461 // different - we still want to unguard the 2nd page in this case.
462 //
463 // 15 bytes seems to be a (very) safe value for max instruction size.
464 bool pc_is_near_addr =
465 (pointer_delta((void*) addr, (void*) pc, sizeof(char)) < 15);
466 bool instr_spans_page_boundary =
467 (align_size_down((intptr_t) pc ^ (intptr_t) addr,
468 (intptr_t) page_size) > 0);
470 if (pc == addr || (pc_is_near_addr && instr_spans_page_boundary)) {
471 static volatile address last_addr =
472 (address) os::non_memory_address_word();
474 // In conservative mode, don't unguard unless the address is in the VM
475 if (addr != last_addr &&
476 (UnguardOnExecutionViolation > 1 || os::address_is_in_vm(addr))) {
478 // Set memory to RWX and retry
479 address page_start =
480 (address) align_size_down((intptr_t) addr, (intptr_t) page_size);
481 bool res = os::protect_memory((char*) page_start, page_size,
482 os::MEM_PROT_RWX);
484 if (PrintMiscellaneous && Verbose) {
485 char buf[256];
486 jio_snprintf(buf, sizeof(buf), "Execution protection violation "
487 "at " INTPTR_FORMAT
488 ", unguarding " INTPTR_FORMAT ": %s, errno=%d", addr,
489 page_start, (res ? "success" : "failed"), errno);
490 tty->print_raw_cr(buf);
491 }
492 stub = pc;
494 // Set last_addr so if we fault again at the same address, we don't end
495 // up in an endless loop.
496 //
497 // There are two potential complications here. Two threads trapping at
498 // the same address at the same time could cause one of the threads to
499 // think it already unguarded, and abort the VM. Likely very rare.
500 //
501 // The other race involves two threads alternately trapping at
502 // different addresses and failing to unguard the page, resulting in
503 // an endless loop. This condition is probably even more unlikely than
504 // the first.
505 //
506 // Although both cases could be avoided by using locks or thread local
507 // last_addr, these solutions are unnecessary complication: this
508 // handler is a best-effort safety net, not a complete solution. It is
509 // disabled by default and should only be used as a workaround in case
510 // we missed any no-execute-unsafe VM code.
512 last_addr = addr;
513 }
514 }
515 }
516 #endif // !AMD64
518 if (stub != NULL) {
519 // save all thread context in case we need to restore it
520 if (thread != NULL) thread->set_saved_exception_pc(pc);
522 uc->uc_mcontext.gregs[REG_PC] = (greg_t)stub;
523 return true;
524 }
526 // signal-chaining
527 if (os::Linux::chained_handler(sig, info, ucVoid)) {
528 return true;
529 }
531 if (!abort_if_unrecognized) {
532 // caller wants another chance, so give it to him
533 return false;
534 }
536 if (pc == NULL && uc != NULL) {
537 pc = os::Linux::ucontext_get_pc(uc);
538 }
540 // unmask current signal
541 sigset_t newset;
542 sigemptyset(&newset);
543 sigaddset(&newset, sig);
544 sigprocmask(SIG_UNBLOCK, &newset, NULL);
546 VMError err(t, sig, pc, info, ucVoid);
547 err.report_and_die();
549 ShouldNotReachHere();
550 }
552 void os::Linux::init_thread_fpu_state(void) {
553 #ifndef AMD64
554 // set fpu to 53 bit precision
555 set_fpu_control_word(0x27f);
556 #endif // !AMD64
557 }
559 int os::Linux::get_fpu_control_word(void) {
560 #ifdef AMD64
561 return 0;
562 #else
563 int fpu_control;
564 _FPU_GETCW(fpu_control);
565 return fpu_control & 0xffff;
566 #endif // AMD64
567 }
569 void os::Linux::set_fpu_control_word(int fpu_control) {
570 #ifndef AMD64
571 _FPU_SETCW(fpu_control);
572 #endif // !AMD64
573 }
575 // Check that the linux kernel version is 2.4 or higher since earlier
576 // versions do not support SSE without patches.
577 bool os::supports_sse() {
578 #ifdef AMD64
579 return true;
580 #else
581 struct utsname uts;
582 if( uname(&uts) != 0 ) return false; // uname fails?
583 char *minor_string;
584 int major = strtol(uts.release,&minor_string,10);
585 int minor = strtol(minor_string+1,NULL,10);
586 bool result = (major > 2 || (major==2 && minor >= 4));
587 #ifndef PRODUCT
588 if (PrintMiscellaneous && Verbose) {
589 tty->print("OS version is %d.%d, which %s support SSE/SSE2\n",
590 major,minor, result ? "DOES" : "does NOT");
591 }
592 #endif
593 return result;
594 #endif // AMD64
595 }
597 bool os::is_allocatable(size_t bytes) {
598 #ifdef AMD64
599 // unused on amd64?
600 return true;
601 #else
603 if (bytes < 2 * G) {
604 return true;
605 }
607 char* addr = reserve_memory(bytes, NULL);
609 if (addr != NULL) {
610 release_memory(addr, bytes);
611 }
613 return addr != NULL;
614 #endif // AMD64
615 }
617 ////////////////////////////////////////////////////////////////////////////////
618 // thread stack
620 #ifdef AMD64
621 size_t os::Linux::min_stack_allowed = 64 * K;
623 // amd64: pthread on amd64 is always in floating stack mode
624 bool os::Linux::supports_variable_stack_size() { return true; }
625 #else
626 size_t os::Linux::min_stack_allowed = (48 DEBUG_ONLY(+4))*K;
628 #ifdef __GNUC__
629 #define GET_GS() ({int gs; __asm__ volatile("movw %%gs, %w0":"=q"(gs)); gs&0xffff;})
630 #endif
632 // Test if pthread library can support variable thread stack size. LinuxThreads
633 // in fixed stack mode allocates 2M fixed slot for each thread. LinuxThreads
634 // in floating stack mode and NPTL support variable stack size.
635 bool os::Linux::supports_variable_stack_size() {
636 if (os::Linux::is_NPTL()) {
637 // NPTL, yes
638 return true;
640 } else {
641 // Note: We can't control default stack size when creating a thread.
642 // If we use non-default stack size (pthread_attr_setstacksize), both
643 // floating stack and non-floating stack LinuxThreads will return the
644 // same value. This makes it impossible to implement this function by
645 // detecting thread stack size directly.
646 //
647 // An alternative approach is to check %gs. Fixed-stack LinuxThreads
648 // do not use %gs, so its value is 0. Floating-stack LinuxThreads use
649 // %gs (either as LDT selector or GDT selector, depending on kernel)
650 // to access thread specific data.
651 //
652 // Note that %gs is a reserved glibc register since early 2001, so
653 // applications are not allowed to change its value (Ulrich Drepper from
654 // Redhat confirmed that all known offenders have been modified to use
655 // either %fs or TSD). In the worst case scenario, when VM is embedded in
656 // a native application that plays with %gs, we might see non-zero %gs
657 // even LinuxThreads is running in fixed stack mode. As the result, we'll
658 // return true and skip _thread_safety_check(), so we may not be able to
659 // detect stack-heap collisions. But otherwise it's harmless.
660 //
661 #ifdef __GNUC__
662 return (GET_GS() != 0);
663 #else
664 return false;
665 #endif
666 }
667 }
668 #endif // AMD64
670 // return default stack size for thr_type
671 size_t os::Linux::default_stack_size(os::ThreadType thr_type) {
672 // default stack size (compiler thread needs larger stack)
673 #ifdef AMD64
674 size_t s = (thr_type == os::compiler_thread ? 4 * M : 1 * M);
675 #else
676 size_t s = (thr_type == os::compiler_thread ? 2 * M : 512 * K);
677 #endif // AMD64
678 return s;
679 }
681 size_t os::Linux::default_guard_size(os::ThreadType thr_type) {
682 // Creating guard page is very expensive. Java thread has HotSpot
683 // guard page, only enable glibc guard page for non-Java threads.
684 return (thr_type == java_thread ? 0 : page_size());
685 }
687 // Java thread:
688 //
689 // Low memory addresses
690 // +------------------------+
691 // | |\ JavaThread created by VM does not have glibc
692 // | glibc guard page | - guard, attached Java thread usually has
693 // | |/ 1 page glibc guard.
694 // P1 +------------------------+ Thread::stack_base() - Thread::stack_size()
695 // | |\
696 // | HotSpot Guard Pages | - red and yellow pages
697 // | |/
698 // +------------------------+ JavaThread::stack_yellow_zone_base()
699 // | |\
700 // | Normal Stack | -
701 // | |/
702 // P2 +------------------------+ Thread::stack_base()
703 //
704 // Non-Java thread:
705 //
706 // Low memory addresses
707 // +------------------------+
708 // | |\
709 // | glibc guard page | - usually 1 page
710 // | |/
711 // P1 +------------------------+ Thread::stack_base() - Thread::stack_size()
712 // | |\
713 // | Normal Stack | -
714 // | |/
715 // P2 +------------------------+ Thread::stack_base()
716 //
717 // ** P1 (aka bottom) and size ( P2 = P1 - size) are the address and stack size returned from
718 // pthread_attr_getstack()
720 static void current_stack_region(address * bottom, size_t * size) {
721 if (os::Linux::is_initial_thread()) {
722 // initial thread needs special handling because pthread_getattr_np()
723 // may return bogus value.
724 *bottom = os::Linux::initial_thread_stack_bottom();
725 *size = os::Linux::initial_thread_stack_size();
726 } else {
727 pthread_attr_t attr;
729 int rslt = pthread_getattr_np(pthread_self(), &attr);
731 // JVM needs to know exact stack location, abort if it fails
732 if (rslt != 0) {
733 if (rslt == ENOMEM) {
734 vm_exit_out_of_memory(0, OOM_MMAP_ERROR, "pthread_getattr_np");
735 } else {
736 fatal(err_msg("pthread_getattr_np failed with errno = %d", rslt));
737 }
738 }
740 if (pthread_attr_getstack(&attr, (void **)bottom, size) != 0) {
741 fatal("Can not locate current stack attributes!");
742 }
744 pthread_attr_destroy(&attr);
746 }
747 assert(os::current_stack_pointer() >= *bottom &&
748 os::current_stack_pointer() < *bottom + *size, "just checking");
749 }
751 address os::current_stack_base() {
752 address bottom;
753 size_t size;
754 current_stack_region(&bottom, &size);
755 return (bottom + size);
756 }
758 size_t os::current_stack_size() {
759 // stack size includes normal stack and HotSpot guard pages
760 address bottom;
761 size_t size;
762 current_stack_region(&bottom, &size);
763 return size;
764 }
766 /////////////////////////////////////////////////////////////////////////////
767 // helper functions for fatal error handler
769 void os::print_context(outputStream *st, void *context) {
770 if (context == NULL) return;
772 ucontext_t *uc = (ucontext_t*)context;
773 st->print_cr("Registers:");
774 #ifdef AMD64
775 st->print( "RAX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RAX]);
776 st->print(", RBX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RBX]);
777 st->print(", RCX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RCX]);
778 st->print(", RDX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RDX]);
779 st->cr();
780 st->print( "RSP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RSP]);
781 st->print(", RBP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RBP]);
782 st->print(", RSI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RSI]);
783 st->print(", RDI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RDI]);
784 st->cr();
785 st->print( "R8 =" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R8]);
786 st->print(", R9 =" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R9]);
787 st->print(", R10=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R10]);
788 st->print(", R11=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R11]);
789 st->cr();
790 st->print( "R12=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R12]);
791 st->print(", R13=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R13]);
792 st->print(", R14=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R14]);
793 st->print(", R15=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R15]);
794 st->cr();
795 st->print( "RIP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RIP]);
796 st->print(", EFLAGS=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EFL]);
797 st->print(", CSGSFS=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_CSGSFS]);
798 st->print(", ERR=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_ERR]);
799 st->cr();
800 st->print(" TRAPNO=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_TRAPNO]);
801 #else
802 st->print( "EAX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EAX]);
803 st->print(", EBX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EBX]);
804 st->print(", ECX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_ECX]);
805 st->print(", EDX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EDX]);
806 st->cr();
807 st->print( "ESP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_UESP]);
808 st->print(", EBP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EBP]);
809 st->print(", ESI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_ESI]);
810 st->print(", EDI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EDI]);
811 st->cr();
812 st->print( "EIP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EIP]);
813 st->print(", EFLAGS=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EFL]);
814 st->print(", CR2=" INTPTR_FORMAT, uc->uc_mcontext.cr2);
815 #endif // AMD64
816 st->cr();
817 st->cr();
819 intptr_t *sp = (intptr_t *)os::Linux::ucontext_get_sp(uc);
820 st->print_cr("Top of Stack: (sp=" PTR_FORMAT ")", sp);
821 print_hex_dump(st, (address)sp, (address)(sp + 8*sizeof(intptr_t)), sizeof(intptr_t));
822 st->cr();
824 // Note: it may be unsafe to inspect memory near pc. For example, pc may
825 // point to garbage if entry point in an nmethod is corrupted. Leave
826 // this at the end, and hope for the best.
827 address pc = os::Linux::ucontext_get_pc(uc);
828 st->print_cr("Instructions: (pc=" PTR_FORMAT ")", pc);
829 print_hex_dump(st, pc - 32, pc + 32, sizeof(char));
830 }
832 void os::print_register_info(outputStream *st, void *context) {
833 if (context == NULL) return;
835 ucontext_t *uc = (ucontext_t*)context;
837 st->print_cr("Register to memory mapping:");
838 st->cr();
840 // this is horrendously verbose but the layout of the registers in the
841 // context does not match how we defined our abstract Register set, so
842 // we can't just iterate through the gregs area
844 // this is only for the "general purpose" registers
846 #ifdef AMD64
847 st->print("RAX="); print_location(st, uc->uc_mcontext.gregs[REG_RAX]);
848 st->print("RBX="); print_location(st, uc->uc_mcontext.gregs[REG_RBX]);
849 st->print("RCX="); print_location(st, uc->uc_mcontext.gregs[REG_RCX]);
850 st->print("RDX="); print_location(st, uc->uc_mcontext.gregs[REG_RDX]);
851 st->print("RSP="); print_location(st, uc->uc_mcontext.gregs[REG_RSP]);
852 st->print("RBP="); print_location(st, uc->uc_mcontext.gregs[REG_RBP]);
853 st->print("RSI="); print_location(st, uc->uc_mcontext.gregs[REG_RSI]);
854 st->print("RDI="); print_location(st, uc->uc_mcontext.gregs[REG_RDI]);
855 st->print("R8 ="); print_location(st, uc->uc_mcontext.gregs[REG_R8]);
856 st->print("R9 ="); print_location(st, uc->uc_mcontext.gregs[REG_R9]);
857 st->print("R10="); print_location(st, uc->uc_mcontext.gregs[REG_R10]);
858 st->print("R11="); print_location(st, uc->uc_mcontext.gregs[REG_R11]);
859 st->print("R12="); print_location(st, uc->uc_mcontext.gregs[REG_R12]);
860 st->print("R13="); print_location(st, uc->uc_mcontext.gregs[REG_R13]);
861 st->print("R14="); print_location(st, uc->uc_mcontext.gregs[REG_R14]);
862 st->print("R15="); print_location(st, uc->uc_mcontext.gregs[REG_R15]);
863 #else
864 st->print("EAX="); print_location(st, uc->uc_mcontext.gregs[REG_EAX]);
865 st->print("EBX="); print_location(st, uc->uc_mcontext.gregs[REG_EBX]);
866 st->print("ECX="); print_location(st, uc->uc_mcontext.gregs[REG_ECX]);
867 st->print("EDX="); print_location(st, uc->uc_mcontext.gregs[REG_EDX]);
868 st->print("ESP="); print_location(st, uc->uc_mcontext.gregs[REG_ESP]);
869 st->print("EBP="); print_location(st, uc->uc_mcontext.gregs[REG_EBP]);
870 st->print("ESI="); print_location(st, uc->uc_mcontext.gregs[REG_ESI]);
871 st->print("EDI="); print_location(st, uc->uc_mcontext.gregs[REG_EDI]);
872 #endif // AMD64
874 st->cr();
875 }
877 void os::setup_fpu() {
878 #ifndef AMD64
879 address fpu_cntrl = StubRoutines::addr_fpu_cntrl_wrd_std();
880 __asm__ volatile ( "fldcw (%0)" :
881 : "r" (fpu_cntrl) : "memory");
882 #endif // !AMD64
883 }
885 #ifndef PRODUCT
886 void os::verify_stack_alignment() {
887 #ifdef AMD64
888 assert(((intptr_t)os::current_stack_pointer() & (StackAlignmentInBytes-1)) == 0, "incorrect stack alignment");
889 #endif
890 }
891 #endif