1 /*
2 * Copyright (c) 1999, 2018, 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 SignalHandlerMark shm(t);
228
229 // Note: it's not uncommon that JNI code uses signal/sigset to install
230 // then restore certain signal handler (e.g. to temporarily block SIGPIPE,
231 // or have a SIGILL handler when detecting CPU type). When that happens,
232 // JVM_handle_linux_signal() might be invoked with junk info/ucVoid. To
233 // avoid unnecessary crash when libjsig is not preloaded, try handle signals
234 // that do not require siginfo/ucontext first.
235
236 if (sig == SIGPIPE || sig == SIGXFSZ) {
237 // allow chained handler to go first
238 if (os::Linux::chained_handler(sig, info, ucVoid)) {
239 return true;
240 } else {
241 if (PrintMiscellaneous && (WizardMode || Verbose)) {
242 char buf[64];
243 warning("Ignoring %s - see bugs 4229104 or 646499219",
244 os::exception_name(sig, buf, sizeof(buf)));
245 }
246 return true;
247 }
248 }
249
250 JavaThread* thread = NULL;
251 VMThread* vmthread = NULL;
252 if (os::Linux::signal_handlers_are_installed) {
253 if (t != NULL ){
254 if(t->is_Java_thread()) {
255 thread = (JavaThread*)t;
256 }
257 else if(t->is_VM_thread()){
258 vmthread = (VMThread *)t;
259 }
260 }
261 }
262 /*
263 NOTE: does not seem to work on linux.
264 if (info == NULL || info->si_code <= 0 || info->si_code == SI_NOINFO) {
265 // can't decode this kind of signal
266 info = NULL;
267 } else {
268 assert(sig == info->si_signo, "bad siginfo");
269 }
270 */
271 // decide if this trap can be handled by a stub
272 address stub = NULL;
273
274 address pc = NULL;
275
276 //%note os_trap_1
277 if (info != NULL && uc != NULL && thread != NULL) {
278 pc = (address) os::Linux::ucontext_get_pc(uc);
279
280 if (StubRoutines::is_safefetch_fault(pc)) {
281 uc->uc_mcontext.gregs[REG_PC] = intptr_t(StubRoutines::continuation_for_safefetch_fault(pc));
282 return 1;
283 }
284
285 #ifndef AMD64
286 // Halt if SI_KERNEL before more crashes get misdiagnosed as Java bugs
287 // This can happen in any running code (currently more frequently in
288 // interpreter code but has been seen in compiled code)
289 if (sig == SIGSEGV && info->si_addr == 0 && info->si_code == SI_KERNEL) {
290 fatal("An irrecoverable SI_KERNEL SIGSEGV has occurred due "
291 "to unstable signal handling in this distribution.");
292 }
293 #endif // AMD64
294
295 // Handle ALL stack overflow variations here
296 if (sig == SIGSEGV) {
297 address addr = (address) info->si_addr;
298
299 // check if fault address is within thread stack
300 if (addr < thread->stack_base() &&
301 addr >= thread->stack_base() - thread->stack_size()) {
302 // stack overflow
303 if (thread->in_stack_yellow_zone(addr)) {
304 thread->disable_stack_yellow_zone();
305 if (thread->thread_state() == _thread_in_Java) {
306 // Throw a stack overflow exception. Guard pages will be reenabled
307 // while unwinding the stack.
308 stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::STACK_OVERFLOW);
309 } else {
310 // Thread was in the vm or native code. Return and try to finish.
311 return 1;
312 }
313 } else if (thread->in_stack_red_zone(addr)) {
314 // Fatal red zone violation. Disable the guard pages and fall through
315 // to handle_unexpected_exception way down below.
316 thread->disable_stack_red_zone();
317 tty->print_raw_cr("An irrecoverable stack overflow has occurred.");
318
319 // This is a likely cause, but hard to verify. Let's just print
320 // it as a hint.
321 tty->print_raw_cr("Please check if any of your loaded .so files has "
322 "enabled executable stack (see man page execstack(8))");
323 } else {
324 // Accessing stack address below sp may cause SEGV if current
325 // thread has MAP_GROWSDOWN stack. This should only happen when
326 // current thread was created by user code with MAP_GROWSDOWN flag
327 // and then attached to VM. See notes in os_linux.cpp.
328 if (thread->osthread()->expanding_stack() == 0) {
329 thread->osthread()->set_expanding_stack();
330 if (os::Linux::manually_expand_stack(thread, addr)) {
331 thread->osthread()->clear_expanding_stack();
332 return 1;
333 }
334 thread->osthread()->clear_expanding_stack();
335 } else {
336 fatal("recursive segv. expanding stack.");
337 }
338 }
339 }
340 }
341
342 if ((sig == SIGSEGV) && VM_Version::is_cpuinfo_segv_addr(pc)) {
343 // Verify that OS save/restore AVX registers.
344 stub = VM_Version::cpuinfo_cont_addr();
345 }
346
347 if (thread->thread_state() == _thread_in_Java) {
348 // Java thread running in Java code => find exception handler if any
349 // a fault inside compiled code, the interpreter, or a stub
350
351 if (sig == SIGSEGV && os::is_poll_address((address)info->si_addr)) {
352 stub = SharedRuntime::get_poll_stub(pc);
353 } else if (sig == SIGBUS /* && info->si_code == BUS_OBJERR */) {
354 // BugId 4454115: A read from a MappedByteBuffer can fault
355 // here if the underlying file has been truncated.
356 // Do not crash the VM in such a case.
357 CodeBlob* cb = CodeCache::find_blob_unsafe(pc);
358 nmethod* nm = (cb != NULL && cb->is_nmethod()) ? (nmethod*)cb : NULL;
359 if (nm != NULL && nm->has_unsafe_access()) {
360 stub = StubRoutines::handler_for_unsafe_access();
361 }
362 }
363 else
364
365 #ifdef AMD64
366 if (sig == SIGFPE &&
367 (info->si_code == FPE_INTDIV || info->si_code == FPE_FLTDIV)) {
368 stub =
369 SharedRuntime::
370 continuation_for_implicit_exception(thread,
371 pc,
372 SharedRuntime::
373 IMPLICIT_DIVIDE_BY_ZERO);
374 #else
375 if (sig == SIGFPE /* && info->si_code == FPE_INTDIV */) {
376 // HACK: si_code does not work on linux 2.2.12-20!!!
377 int op = pc[0];
378 if (op == 0xDB) {
379 // FIST
380 // TODO: The encoding of D2I in i486.ad can cause an exception
381 // prior to the fist instruction if there was an invalid operation
382 // pending. We want to dismiss that exception. From the win_32
383 // side it also seems that if it really was the fist causing
384 // the exception that we do the d2i by hand with different
385 // rounding. Seems kind of weird.
386 // NOTE: that we take the exception at the NEXT floating point instruction.
387 assert(pc[0] == 0xDB, "not a FIST opcode");
388 assert(pc[1] == 0x14, "not a FIST opcode");
389 assert(pc[2] == 0x24, "not a FIST opcode");
390 return true;
391 } else if (op == 0xF7) {
392 // IDIV
393 stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_DIVIDE_BY_ZERO);
394 } else {
395 // TODO: handle more cases if we are using other x86 instructions
396 // that can generate SIGFPE signal on linux.
397 tty->print_cr("unknown opcode 0x%X with SIGFPE.", op);
398 fatal("please update this code.");
399 }
400 #endif // AMD64
401 } else if (sig == SIGSEGV &&
402 !MacroAssembler::needs_explicit_null_check((intptr_t)info->si_addr)) {
403 // Determination of interpreter/vtable stub/compiled code null exception
404 stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_NULL);
405 }
406 } else if (thread->thread_state() == _thread_in_vm &&
407 sig == SIGBUS && /* info->si_code == BUS_OBJERR && */
408 thread->doing_unsafe_access()) {
409 stub = StubRoutines::handler_for_unsafe_access();
410 }
411
412 // jni_fast_Get<Primitive>Field can trap at certain pc's if a GC kicks in
413 // and the heap gets shrunk before the field access.
414 if ((sig == SIGSEGV) || (sig == SIGBUS)) {
415 address addr = JNI_FastGetField::find_slowcase_pc(pc);
416 if (addr != (address)-1) {
417 stub = addr;
418 }
419 }
420
421 // Check to see if we caught the safepoint code in the
422 // process of write protecting the memory serialization page.
423 // It write enables the page immediately after protecting it
424 // so we can just return to retry the write.
425 if ((sig == SIGSEGV) &&
426 os::is_memory_serialize_page(thread, (address) info->si_addr)) {
427 // Block current thread until the memory serialize page permission restored.
428 os::block_on_serialize_page_trap();
429 return true;
430 }
431 }
432
433 #ifndef AMD64
434 // Execution protection violation
435 //
436 // This should be kept as the last step in the triage. We don't
437 // have a dedicated trap number for a no-execute fault, so be
438 // conservative and allow other handlers the first shot.
439 //
440 // Note: We don't test that info->si_code == SEGV_ACCERR here.
441 // this si_code is so generic that it is almost meaningless; and
442 // the si_code for this condition may change in the future.
443 // Furthermore, a false-positive should be harmless.
444 if (UnguardOnExecutionViolation > 0 &&
445 (sig == SIGSEGV || sig == SIGBUS) &&
446 uc->uc_mcontext.gregs[REG_TRAPNO] == trap_page_fault) {
447 int page_size = os::vm_page_size();
448 address addr = (address) info->si_addr;
449 address pc = os::Linux::ucontext_get_pc(uc);
450 // Make sure the pc and the faulting address are sane.
451 //
452 // If an instruction spans a page boundary, and the page containing
453 // the beginning of the instruction is executable but the following
454 // page is not, the pc and the faulting address might be slightly
455 // different - we still want to unguard the 2nd page in this case.
456 //
457 // 15 bytes seems to be a (very) safe value for max instruction size.
458 bool pc_is_near_addr =
459 (pointer_delta((void*) addr, (void*) pc, sizeof(char)) < 15);
460 bool instr_spans_page_boundary =
461 (align_size_down((intptr_t) pc ^ (intptr_t) addr,
462 (intptr_t) page_size) > 0);
463
464 if (pc == addr || (pc_is_near_addr && instr_spans_page_boundary)) {
465 static volatile address last_addr =
466 (address) os::non_memory_address_word();
467
468 // In conservative mode, don't unguard unless the address is in the VM
469 if (addr != last_addr &&
470 (UnguardOnExecutionViolation > 1 || os::address_is_in_vm(addr))) {
471
472 // Set memory to RWX and retry
473 address page_start =
474 (address) align_size_down((intptr_t) addr, (intptr_t) page_size);
475 bool res = os::protect_memory((char*) page_start, page_size,
476 os::MEM_PROT_RWX);
477
478 if (PrintMiscellaneous && Verbose) {
479 char buf[256];
480 jio_snprintf(buf, sizeof(buf), "Execution protection violation "
481 "at " INTPTR_FORMAT
482 ", unguarding " INTPTR_FORMAT ": %s, errno=%d", addr,
483 page_start, (res ? "success" : "failed"), errno);
484 tty->print_raw_cr(buf);
485 }
486 stub = pc;
487
488 // Set last_addr so if we fault again at the same address, we don't end
489 // up in an endless loop.
490 //
491 // There are two potential complications here. Two threads trapping at
492 // the same address at the same time could cause one of the threads to
493 // think it already unguarded, and abort the VM. Likely very rare.
494 //
495 // The other race involves two threads alternately trapping at
496 // different addresses and failing to unguard the page, resulting in
497 // an endless loop. This condition is probably even more unlikely than
498 // the first.
499 //
500 // Although both cases could be avoided by using locks or thread local
501 // last_addr, these solutions are unnecessary complication: this
502 // handler is a best-effort safety net, not a complete solution. It is
503 // disabled by default and should only be used as a workaround in case
504 // we missed any no-execute-unsafe VM code.
505
506 last_addr = addr;
507 }
508 }
509 }
510 #endif // !AMD64
511
512 if (stub != NULL) {
513 // save all thread context in case we need to restore it
514 if (thread != NULL) thread->set_saved_exception_pc(pc);
515
516 uc->uc_mcontext.gregs[REG_PC] = (greg_t)stub;
517 return true;
518 }
519
520 // signal-chaining
521 if (os::Linux::chained_handler(sig, info, ucVoid)) {
522 return true;
523 }
524
525 if (!abort_if_unrecognized) {
526 // caller wants another chance, so give it to him
527 return false;
528 }
529
530 if (pc == NULL && uc != NULL) {
531 pc = os::Linux::ucontext_get_pc(uc);
532 }
533
534 // unmask current signal
535 sigset_t newset;
536 sigemptyset(&newset);
537 sigaddset(&newset, sig);
538 sigprocmask(SIG_UNBLOCK, &newset, NULL);
539
540 VMError err(t, sig, pc, info, ucVoid);
541 err.report_and_die();
542
543 ShouldNotReachHere();
544 return true; // Mute compiler
545 }
546
547 void os::Linux::init_thread_fpu_state(void) {
548 #ifndef AMD64
549 // set fpu to 53 bit precision
550 set_fpu_control_word(0x27f);
551 #endif // !AMD64
552 }
553
554 int os::Linux::get_fpu_control_word(void) {
555 #ifdef AMD64
556 return 0;
557 #else
558 int fpu_control;
559 _FPU_GETCW(fpu_control);
560 return fpu_control & 0xffff;
561 #endif // AMD64
562 }
563
564 void os::Linux::set_fpu_control_word(int fpu_control) {
565 #ifndef AMD64
566 _FPU_SETCW(fpu_control);
567 #endif // !AMD64
568 }
569
570 // Check that the linux kernel version is 2.4 or higher since earlier
571 // versions do not support SSE without patches.
572 bool os::supports_sse() {
573 #ifdef AMD64
574 return true;
575 #else
576 struct utsname uts;
577 if( uname(&uts) != 0 ) return false; // uname fails?
578 char *minor_string;
579 int major = strtol(uts.release,&minor_string,10);
580 int minor = strtol(minor_string+1,NULL,10);
581 bool result = (major > 2 || (major==2 && minor >= 4));
582 #ifndef PRODUCT
583 if (PrintMiscellaneous && Verbose) {
584 tty->print("OS version is %d.%d, which %s support SSE/SSE2\n",
585 major,minor, result ? "DOES" : "does NOT");
586 }
587 #endif
588 return result;
589 #endif // AMD64
590 }
591
592 bool os::is_allocatable(size_t bytes) {
593 #ifdef AMD64
594 // unused on amd64?
595 return true;
596 #else
597
598 if (bytes < 2 * G) {
599 return true;
600 }
601
602 char* addr = reserve_memory(bytes, NULL);
603
604 if (addr != NULL) {
605 release_memory(addr, bytes);
606 }
607
608 return addr != NULL;
609 #endif // AMD64
610 }
611
612 ////////////////////////////////////////////////////////////////////////////////
613 // thread stack
614
615 #ifdef AMD64
616 size_t os::Linux::min_stack_allowed = 64 * K;
617
618 // amd64: pthread on amd64 is always in floating stack mode
619 bool os::Linux::supports_variable_stack_size() { return true; }
620 #else
621 size_t os::Linux::min_stack_allowed = (48 DEBUG_ONLY(+4))*K;
622
623 #ifdef __GNUC__
624 #define GET_GS() ({int gs; __asm__ volatile("movw %%gs, %w0":"=q"(gs)); gs&0xffff;})
625 #endif
626
627 // Test if pthread library can support variable thread stack size. LinuxThreads
628 // in fixed stack mode allocates 2M fixed slot for each thread. LinuxThreads
629 // in floating stack mode and NPTL support variable stack size.
630 bool os::Linux::supports_variable_stack_size() {
631 if (os::Linux::is_NPTL()) {
632 // NPTL, yes
633 return true;
634
635 } else {
636 // Note: We can't control default stack size when creating a thread.
637 // If we use non-default stack size (pthread_attr_setstacksize), both
638 // floating stack and non-floating stack LinuxThreads will return the
639 // same value. This makes it impossible to implement this function by
640 // detecting thread stack size directly.
641 //
642 // An alternative approach is to check %gs. Fixed-stack LinuxThreads
643 // do not use %gs, so its value is 0. Floating-stack LinuxThreads use
644 // %gs (either as LDT selector or GDT selector, depending on kernel)
645 // to access thread specific data.
646 //
647 // Note that %gs is a reserved glibc register since early 2001, so
648 // applications are not allowed to change its value (Ulrich Drepper from
649 // Redhat confirmed that all known offenders have been modified to use
650 // either %fs or TSD). In the worst case scenario, when VM is embedded in
651 // a native application that plays with %gs, we might see non-zero %gs
652 // even LinuxThreads is running in fixed stack mode. As the result, we'll
653 // return true and skip _thread_safety_check(), so we may not be able to
654 // detect stack-heap collisions. But otherwise it's harmless.
655 //
656 #ifdef __GNUC__
657 return (GET_GS() != 0);
658 #else
659 return false;
660 #endif
661 }
662 }
663 #endif // AMD64
664
665 // return default stack size for thr_type
666 size_t os::Linux::default_stack_size(os::ThreadType thr_type) {
667 // default stack size (compiler thread needs larger stack)
668 #ifdef AMD64
669 size_t s = (thr_type == os::compiler_thread ? 4 * M : 1 * M);
670 #else
671 size_t s = (thr_type == os::compiler_thread ? 2 * M : 512 * K);
672 #endif // AMD64
673 return s;
674 }
675
676 size_t os::Linux::default_guard_size(os::ThreadType thr_type) {
677 // Creating guard page is very expensive. Java thread has HotSpot
678 // guard page, only enable glibc guard page for non-Java threads.
679 return (thr_type == java_thread ? 0 : page_size());
680 }
681
682 // Java thread:
683 //
684 // Low memory addresses
685 // +------------------------+
686 // | |\ JavaThread created by VM does not have glibc
687 // | glibc guard page | - guard, attached Java thread usually has
688 // | |/ 1 page glibc guard.
689 // P1 +------------------------+ Thread::stack_base() - Thread::stack_size()
690 // | |\
691 // | HotSpot Guard Pages | - red and yellow pages
692 // | |/
693 // +------------------------+ JavaThread::stack_yellow_zone_base()
694 // | |\
695 // | Normal Stack | -
696 // | |/
697 // P2 +------------------------+ Thread::stack_base()
698 //
699 // Non-Java thread:
700 //
701 // Low memory addresses
702 // +------------------------+
703 // | |\
704 // | glibc guard page | - usually 1 page
705 // | |/
706 // P1 +------------------------+ Thread::stack_base() - Thread::stack_size()
707 // | |\
708 // | Normal Stack | -
709 // | |/
710 // P2 +------------------------+ Thread::stack_base()
711 //
712 // ** P1 (aka bottom) and size ( P2 = P1 - size) are the address and stack size returned from
713 // pthread_attr_getstack()
714
715 static void current_stack_region(address * bottom, size_t * size) {
716 if (os::is_primordial_thread()) {
717 // primordial thread needs special handling because pthread_getattr_np()
718 // may return bogus value.
719 *bottom = os::Linux::initial_thread_stack_bottom();
720 *size = os::Linux::initial_thread_stack_size();
721 } else {
722 pthread_attr_t attr;
723
724 int rslt = pthread_getattr_np(pthread_self(), &attr);
725
726 // JVM needs to know exact stack location, abort if it fails
727 if (rslt != 0) {
728 if (rslt == ENOMEM) {
729 vm_exit_out_of_memory(0, OOM_MMAP_ERROR, "pthread_getattr_np");
730 } else {
731 fatal(err_msg("pthread_getattr_np failed with errno = %d", rslt));
732 }
733 }
734
735 if (pthread_attr_getstack(&attr, (void **)bottom, size) != 0) {
736 fatal("Can not locate current stack attributes!");
737 }
738
739 pthread_attr_destroy(&attr);
740
741 }
742 assert(os::current_stack_pointer() >= *bottom &&
743 os::current_stack_pointer() < *bottom + *size, "just checking");
744 }
745
746 address os::current_stack_base() {
747 address bottom;
748 size_t size;
749 current_stack_region(&bottom, &size);
750 return (bottom + size);
751 }
752
753 size_t os::current_stack_size() {
754 // stack size includes normal stack and HotSpot guard pages
755 address bottom;
756 size_t size;
757 current_stack_region(&bottom, &size);
758 return size;
759 }
760
761 /////////////////////////////////////////////////////////////////////////////
762 // helper functions for fatal error handler
763
764 void os::print_context(outputStream *st, void *context) {
765 if (context == NULL) return;
766
767 ucontext_t *uc = (ucontext_t*)context;
768 st->print_cr("Registers:");
769 #ifdef AMD64
770 st->print( "RAX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RAX]);
771 st->print(", RBX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RBX]);
772 st->print(", RCX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RCX]);
773 st->print(", RDX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RDX]);
774 st->cr();
775 st->print( "RSP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RSP]);
776 st->print(", RBP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RBP]);
777 st->print(", RSI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RSI]);
778 st->print(", RDI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RDI]);
779 st->cr();
780 st->print( "R8 =" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R8]);
781 st->print(", R9 =" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R9]);
782 st->print(", R10=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R10]);
783 st->print(", R11=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R11]);
784 st->cr();
785 st->print( "R12=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R12]);
786 st->print(", R13=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R13]);
787 st->print(", R14=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R14]);
788 st->print(", R15=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R15]);
789 st->cr();
790 st->print( "RIP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RIP]);
791 st->print(", EFLAGS=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EFL]);
792 st->print(", CSGSFS=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_CSGSFS]);
793 st->print(", ERR=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_ERR]);
794 st->cr();
795 st->print(" TRAPNO=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_TRAPNO]);
796 #else
797 st->print( "EAX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EAX]);
798 st->print(", EBX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EBX]);
799 st->print(", ECX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_ECX]);
800 st->print(", EDX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EDX]);
801 st->cr();
802 st->print( "ESP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_UESP]);
803 st->print(", EBP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EBP]);
804 st->print(", ESI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_ESI]);
805 st->print(", EDI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EDI]);
806 st->cr();
807 st->print( "EIP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EIP]);
808 st->print(", EFLAGS=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_EFL]);
809 st->print(", CR2=" INTPTR_FORMAT, uc->uc_mcontext.cr2);
810 #endif // AMD64
811 st->cr();
812 st->cr();
813
814 intptr_t *sp = (intptr_t *)os::Linux::ucontext_get_sp(uc);
815 st->print_cr("Top of Stack: (sp=" PTR_FORMAT ")", sp);
816 print_hex_dump(st, (address)sp, (address)(sp + 8*sizeof(intptr_t)), sizeof(intptr_t));
817 st->cr();
818
819 // Note: it may be unsafe to inspect memory near pc. For example, pc may
820 // point to garbage if entry point in an nmethod is corrupted. Leave
821 // this at the end, and hope for the best.
822 address pc = os::Linux::ucontext_get_pc(uc);
823 st->print_cr("Instructions: (pc=" PTR_FORMAT ")", pc);
824 print_hex_dump(st, pc - 32, pc + 32, sizeof(char));
825 }
826
827 void os::print_register_info(outputStream *st, void *context) {
828 if (context == NULL) return;
829
830 ucontext_t *uc = (ucontext_t*)context;
831
832 st->print_cr("Register to memory mapping:");
833 st->cr();
834
835 // this is horrendously verbose but the layout of the registers in the
836 // context does not match how we defined our abstract Register set, so
837 // we can't just iterate through the gregs area
838
839 // this is only for the "general purpose" registers
840
841 #ifdef AMD64
842 st->print("RAX="); print_location(st, uc->uc_mcontext.gregs[REG_RAX]);
843 st->print("RBX="); print_location(st, uc->uc_mcontext.gregs[REG_RBX]);
844 st->print("RCX="); print_location(st, uc->uc_mcontext.gregs[REG_RCX]);
845 st->print("RDX="); print_location(st, uc->uc_mcontext.gregs[REG_RDX]);
846 st->print("RSP="); print_location(st, uc->uc_mcontext.gregs[REG_RSP]);
847 st->print("RBP="); print_location(st, uc->uc_mcontext.gregs[REG_RBP]);
848 st->print("RSI="); print_location(st, uc->uc_mcontext.gregs[REG_RSI]);
849 st->print("RDI="); print_location(st, uc->uc_mcontext.gregs[REG_RDI]);
850 st->print("R8 ="); print_location(st, uc->uc_mcontext.gregs[REG_R8]);
851 st->print("R9 ="); print_location(st, uc->uc_mcontext.gregs[REG_R9]);
852 st->print("R10="); print_location(st, uc->uc_mcontext.gregs[REG_R10]);
853 st->print("R11="); print_location(st, uc->uc_mcontext.gregs[REG_R11]);
854 st->print("R12="); print_location(st, uc->uc_mcontext.gregs[REG_R12]);
855 st->print("R13="); print_location(st, uc->uc_mcontext.gregs[REG_R13]);
856 st->print("R14="); print_location(st, uc->uc_mcontext.gregs[REG_R14]);
857 st->print("R15="); print_location(st, uc->uc_mcontext.gregs[REG_R15]);
858 #else
859 st->print("EAX="); print_location(st, uc->uc_mcontext.gregs[REG_EAX]);
860 st->print("EBX="); print_location(st, uc->uc_mcontext.gregs[REG_EBX]);
861 st->print("ECX="); print_location(st, uc->uc_mcontext.gregs[REG_ECX]);
862 st->print("EDX="); print_location(st, uc->uc_mcontext.gregs[REG_EDX]);
863 st->print("ESP="); print_location(st, uc->uc_mcontext.gregs[REG_ESP]);
864 st->print("EBP="); print_location(st, uc->uc_mcontext.gregs[REG_EBP]);
865 st->print("ESI="); print_location(st, uc->uc_mcontext.gregs[REG_ESI]);
866 st->print("EDI="); print_location(st, uc->uc_mcontext.gregs[REG_EDI]);
867 #endif // AMD64
868
869 st->cr();
870 }
871
872 void os::setup_fpu() {
873 #ifndef AMD64
874 address fpu_cntrl = StubRoutines::addr_fpu_cntrl_wrd_std();
875 __asm__ volatile ( "fldcw (%0)" :
876 : "r" (fpu_cntrl) : "memory");
877 #endif // !AMD64
878 }
879
880 #ifndef PRODUCT
881 void os::verify_stack_alignment() {
882 #ifdef AMD64
883 assert(((intptr_t)os::current_stack_pointer() & (StackAlignmentInBytes-1)) == 0, "incorrect stack alignment");
884 #endif
885 }
886 #endif
887
888
889 /*
890 * IA32 only: execute code at a high address in case buggy NX emulation is present. I.e. avoid CS limit
891 * updates (JDK-8023956).
892 */
893 void os::workaround_expand_exec_shield_cs_limit() {
894 #if defined(IA32)
895 size_t page_size = os::vm_page_size();
896
897 /*
898 * JDK-8197429
899 *
900 * Expand the stack mapping to the end of the initial stack before
901 * attempting to install the codebuf. This is needed because newer
902 * Linux kernels impose a distance of a megabyte between stack
903 * memory and other memory regions. If we try to install the
904 * codebuf before expanding the stack the installation will appear
905 * to succeed but we'll get a segfault later if we expand the stack
906 * in Java code.
907 *
908 */
909 if (os::is_primordial_thread()) {
910 address limit = Linux::initial_thread_stack_bottom();
911 if (! DisablePrimordialThreadGuardPages) {
912 limit += (StackYellowPages + StackRedPages) * page_size;
913 }
914 os::Linux::expand_stack_to(limit);
915 }
916
917 /*
918 * Take the highest VA the OS will give us and exec
919 *
920 * Although using -(pagesz) as mmap hint works on newer kernel as you would
921 * think, older variants affected by this work-around don't (search forward only).
922 *
923 * On the affected distributions, we understand the memory layout to be:
924 *
925 * TASK_LIMIT= 3G, main stack base close to TASK_LIMT.
926 *
927 * A few pages south main stack will do it.
928 *
929 * If we are embedded in an app other than launcher (initial != main stack),
930 * we don't have much control or understanding of the address space, just let it slide.
931 */
932 char* hint = (char*) (Linux::initial_thread_stack_bottom() -
933 ((StackYellowPages + StackRedPages + 1) * page_size));
934 char* codebuf = os::attempt_reserve_memory_at(page_size, hint);
935
936 if (codebuf == NULL) {
937 // JDK-8197429: There may be a stack gap of one megabyte between
938 // the limit of the stack and the nearest memory region: this is a
939 // Linux kernel workaround for CVE-2017-1000364. If we failed to
940 // map our codebuf, try again at an address one megabyte lower.
941 hint -= 1 * M;
942 codebuf = os::attempt_reserve_memory_at(page_size, hint);
943 }
944
945 if ( (codebuf == NULL) || (!os::commit_memory(codebuf, page_size, true)) ) {
946 return; // No matter, we tried, best effort.
947 }
948 if (PrintMiscellaneous && (Verbose || WizardMode)) {
949 tty->print_cr("[CS limit NX emulation work-around, exec code at: %p]", codebuf);
950 }
951
952 // Some code to exec: the 'ret' instruction
953 codebuf[0] = 0xC3;
954
955 // Call the code in the codebuf
956 __asm__ volatile("call *%0" : : "r"(codebuf));
957
958 // keep the page mapped so CS limit isn't reduced.
959 #endif
960 }