Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * Copyright (c) 1999, 2013, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

  * questions.

  *

  */

 // no precompiled headers

 #include "asm/macroAssembler.hpp"

 #include "classfile/classLoader.hpp"

 #include "classfile/systemDictionary.hpp"

 #include "classfile/vmSymbols.hpp"

 #include "code/icBuffer.hpp"

 #include "code/vtableStubs.hpp"

 #include "interpreter/interpreter.hpp"

 #include "jvm_solaris.h"

 #include "memory/allocation.inline.hpp"

 #include "mutex_solaris.inline.hpp"

 #include "os_share_solaris.hpp"

 #include "prims/jniFastGetField.hpp"

 #include "prims/jvm.h"

 #include "prims/jvm_misc.hpp"

 #include "runtime/arguments.hpp"

 #include "runtime/extendedPC.hpp"

 #include "runtime/frame.inline.hpp"

 #include "runtime/interfaceSupport.hpp"

 #include "runtime/java.hpp"

 #include "runtime/javaCalls.hpp"

 #include "runtime/mutexLocker.hpp"

 #include "runtime/osThread.hpp"

 #include "runtime/sharedRuntime.hpp"

 #include "runtime/stubRoutines.hpp"

 #include "runtime/thread.inline.hpp"

 #include "runtime/timer.hpp"

 #include "utilities/events.hpp"

 #include "utilities/vmError.hpp"

 // put OS-includes here

 # include <sys/types.h>

 # include <sys/mman.h>

 # include <pthread.h>

 # include <signal.h>

 # include <setjmp.h>

 # include <errno.h>

 # include <dlfcn.h>

 # include <stdio.h>

 # include <unistd.h>

 # include <sys/resource.h>

 # include <thread.h>

 # include <sys/stat.h>

 # include <sys/time.h>

 # include <sys/filio.h>

 # include <sys/utsname.h>

 # include <sys/systeminfo.h>

 # include <sys/socket.h>

 # include <sys/trap.h>

 # include <sys/lwp.h>

 # include <pwd.h>

 # include <poll.h>

 # include <sys/lwp.h>

 # include <procfs.h>     //  see comment in <sys/procfs.h>

 #ifndef AMD64

 // QQQ seems useless at this point

 # define _STRUCTURED_PROC 1  //  this gets us the new structured proc interfaces of 5.6 & later

 #endif // AMD64

 # include <sys/procfs.h>     //  see comment in <sys/procfs.h>

 #define MAX_PATH (2 * K)

 // Minimum stack size for the VM.  It's easier to document a constant value

 // but it's different for x86 and sparc because the page sizes are different.

 #ifdef AMD64

 size_t os::Solaris::min_stack_allowed = 224*K;

 #define REG_SP REG_RSP

 #define REG_PC REG_RIP

 #define REG_FP REG_RBP

 #else

 size_t os::Solaris::min_stack_allowed = 64*K;

 #define REG_SP UESP

 #define REG_PC EIP

 #define REG_FP EBP

 // 4900493 counter to prevent runaway LDTR refresh attempt

 static volatile int ldtr_refresh = 0;

 // the libthread instruction that faults because of the stale LDTR

 static const unsigned char movlfs[] = { 0x8e, 0xe0    // movl %eax,%fs

                        };

 #endif // AMD64

 char* os::non_memory_address_word() {

   // Must never look like an address returned by reserve_memory,

   // even in its subfields (as defined by the CPU immediate fields,

   // if the CPU splits constants across multiple instructions).

   return (char*) -1;

 }

 //

 // Validate a ucontext retrieved from walking a uc_link of a ucontext.

 // There are issues with libthread giving out uc_links for different threads

 // on the same uc_link chain and bad or circular links.

 //

 bool os::Solaris::valid_ucontext(Thread* thread, ucontext_t* valid, ucontext_t* suspect) {

   if (valid >= suspect ||

       valid->uc_stack.ss_flags != suspect->uc_stack.ss_flags ||

       valid->uc_stack.ss_sp    != suspect->uc_stack.ss_sp    ||

       valid->uc_stack.ss_size  != suspect->uc_stack.ss_size) {

     DEBUG_ONLY(tty->print_cr("valid_ucontext: failed test 1");)

     return false;

   }

   if (thread->is_Java_thread()) {

     if (!valid_stack_address(thread, (address)suspect)) {

       DEBUG_ONLY(tty->print_cr("valid_ucontext: uc_link not in thread stack");)

       return false;

     }

     if (!valid_stack_address(thread,  (address) suspect->uc_mcontext.gregs[REG_SP])) {

       DEBUG_ONLY(tty->print_cr("valid_ucontext: stackpointer not in thread stack");)

       return false;

     }

   }

   return true;

 }

 // We will only follow one level of uc_link since there are libthread

 // issues with ucontext linking and it is better to be safe and just

 // let caller retry later.

 ucontext_t* os::Solaris::get_valid_uc_in_signal_handler(Thread *thread,

   ucontext_t *uc) {

   ucontext_t *retuc = NULL;

   if (uc != NULL) {

     if (uc->uc_link == NULL) {

       // cannot validate without uc_link so accept current ucontext

       retuc = uc;

     } else if (os::Solaris::valid_ucontext(thread, uc, uc->uc_link)) {

       // first ucontext is valid so try the next one

       uc = uc->uc_link;

       if (uc->uc_link == NULL) {

         // cannot validate without uc_link so accept current ucontext

         retuc = uc;

       } else if (os::Solaris::valid_ucontext(thread, uc, uc->uc_link)) {

         // the ucontext one level down is also valid so return it

         retuc = uc;

       }

     }

   }

   return retuc;

 }

 // Assumes ucontext is valid

 ExtendedPC os::Solaris::ucontext_get_ExtendedPC(ucontext_t *uc) {

   return ExtendedPC((address)uc->uc_mcontext.gregs[REG_PC]);

 }

 // Assumes ucontext is valid

 intptr_t* os::Solaris::ucontext_get_sp(ucontext_t *uc) {

   return (intptr_t*)uc->uc_mcontext.gregs[REG_SP];

 }

 // Assumes ucontext is valid

 intptr_t* os::Solaris::ucontext_get_fp(ucontext_t *uc) {

   return (intptr_t*)uc->uc_mcontext.gregs[REG_FP];

 }

 address os::Solaris::ucontext_get_pc(ucontext_t *uc) {

   return (address) uc->uc_mcontext.gregs[REG_PC];

 }

 // For Forte Analyzer AsyncGetCallTrace profiling support - thread

 // is currently interrupted by SIGPROF.

 //

 // The difference between this and os::fetch_frame_from_context() is that

 // here we try to skip nested signal frames.

 ExtendedPC os::Solaris::fetch_frame_from_ucontext(Thread* thread,

   ucontext_t* uc, intptr_t** ret_sp, intptr_t** ret_fp) {

   assert(thread != NULL, "just checking");

   assert(ret_sp != NULL, "just checking");

   assert(ret_fp != NULL, "just checking");

   ucontext_t *luc = os::Solaris::get_valid_uc_in_signal_handler(thread, uc);

   return os::fetch_frame_from_context(luc, ret_sp, ret_fp);

 }

 ExtendedPC os::fetch_frame_from_context(void* ucVoid,

                     intptr_t** ret_sp, intptr_t** ret_fp) {

   ExtendedPC  epc;

   ucontext_t *uc = (ucontext_t*)ucVoid;

   if (uc != NULL) {

     epc = os::Solaris::ucontext_get_ExtendedPC(uc);

     if (ret_sp) *ret_sp = os::Solaris::ucontext_get_sp(uc);

     if (ret_fp) *ret_fp = os::Solaris::ucontext_get_fp(uc);

   } else {

     // construct empty ExtendedPC for return value checking

     epc = ExtendedPC(NULL);

     if (ret_sp) *ret_sp = (intptr_t *)NULL;

     if (ret_fp) *ret_fp = (intptr_t *)NULL;

   }

   return epc;

 }

 frame os::fetch_frame_from_context(void* ucVoid) {

   intptr_t* sp;

   intptr_t* fp;

   ExtendedPC epc = fetch_frame_from_context(ucVoid, &sp, &fp);

   return frame(sp, fp, epc.pc());

 }

 frame os::get_sender_for_C_frame(frame* fr) {

   return frame(fr->sender_sp(), fr->link(), fr->sender_pc());

 }

 extern "C" intptr_t *_get_current_sp();  // in .il file

 address os::current_stack_pointer() {

   return (address)_get_current_sp();

 }

 extern "C" intptr_t *_get_current_fp();  // in .il file

 frame os::current_frame() {

   intptr_t* fp = _get_current_fp();  // it's inlined so want current fp

   frame myframe((intptr_t*)os::current_stack_pointer(),

                 (intptr_t*)fp,

                 CAST_FROM_FN_PTR(address, os::current_frame));

   if (os::is_first_C_frame(&myframe)) {

     // stack is not walkable

     frame ret; // This will be a null useless frame

     return ret;

   } else {

     return os::get_sender_for_C_frame(&myframe);

   }

 }

 static int threadgetstate(thread_t tid, int *flags, lwpid_t *lwp, stack_t *ss, gregset_t rs, lwpstatus_t *lwpstatus) {

   char lwpstatusfile[PROCFILE_LENGTH];

   int lwpfd, err;

   if (err = os::Solaris::thr_getstate(tid, flags, lwp, ss, rs))

     return (err);

   if (*flags == TRS_LWPID) {

     sprintf(lwpstatusfile, "/proc/%d/lwp/%d/lwpstatus", getpid(),

             *lwp);

     if ((lwpfd = open(lwpstatusfile, O_RDONLY)) < 0) {

       perror("thr_mutator_status: open lwpstatus");

       return (EINVAL);

     }

     if (pread(lwpfd, lwpstatus, sizeof (lwpstatus_t), (off_t)0) !=

         sizeof (lwpstatus_t)) {

       perror("thr_mutator_status: read lwpstatus");

       (void) close(lwpfd);

       return (EINVAL);

     }

     (void) close(lwpfd);

   }

   return (0);

 }

 #ifndef AMD64

 // Detecting SSE support by OS

 // From solaris_i486.s

 extern "C" bool sse_check();

 extern "C" bool sse_unavailable();

 enum { SSE_UNKNOWN, SSE_NOT_SUPPORTED, SSE_SUPPORTED};

 static int sse_status = SSE_UNKNOWN;

 static void  check_for_sse_support() {

   if (!VM_Version::supports_sse()) {

     sse_status = SSE_NOT_SUPPORTED;

     return;

   }

   // looking for _sse_hw in libc.so, if it does not exist or

   // the value (int) is 0, OS has no support for SSE

   int *sse_hwp;

   void *h;

   if ((h=dlopen("/usr/lib/libc.so", RTLD_LAZY)) == NULL) {

     //open failed, presume no support for SSE

     sse_status = SSE_NOT_SUPPORTED;

     return;

   }

   if ((sse_hwp = (int *)dlsym(h, "_sse_hw")) == NULL) {

     sse_status = SSE_NOT_SUPPORTED;

   } else if (*sse_hwp == 0) {

     sse_status = SSE_NOT_SUPPORTED;

   }

   dlclose(h);

   if (sse_status == SSE_UNKNOWN) {

     bool (*try_sse)() = (bool (*)())sse_check;

     sse_status = (*try_sse)() ? SSE_SUPPORTED : SSE_NOT_SUPPORTED;

   }

 }

 #endif // AMD64

 bool os::supports_sse() {

 #ifdef AMD64

   return true;

 #else

   if (sse_status == SSE_UNKNOWN)

     check_for_sse_support();

   return sse_status == SSE_SUPPORTED;

 #endif // AMD64

 }

 bool os::is_allocatable(size_t bytes) {

 #ifdef AMD64

   return true;

 #else

   if (bytes < 2 * G) {

     return true;

   }

   char* addr = reserve_memory(bytes, NULL);

   if (addr != NULL) {

     release_memory(addr, bytes);

   }

   return addr != NULL;

 #endif // AMD64

 }

 extern "C" JNIEXPORT int

 JVM_handle_solaris_signal(int sig, siginfo_t* info, void* ucVoid,

                           int abort_if_unrecognized) {

   ucontext_t* uc = (ucontext_t*) ucVoid;

 #ifndef AMD64

   if (sig == SIGILL && info->si_addr == (caddr_t)sse_check) {

     // the SSE instruction faulted. supports_sse() need return false.

     uc->uc_mcontext.gregs[EIP] = (greg_t)sse_unavailable;

     return true;

   }

 #endif // !AMD64

   Thread* t = ThreadLocalStorage::get_thread_slow();  // slow & steady

   SignalHandlerMark shm(t);

   if(sig == SIGPIPE || sig == SIGXFSZ) {

     if (os::Solaris::chained_handler(sig, info, ucVoid)) {

       return true;

     } else {

       if (PrintMiscellaneous && (WizardMode || Verbose)) {

         char buf[64];

         warning("Ignoring %s - see 4229104 or 6499219",

                 os::exception_name(sig, buf, sizeof(buf)));

       }

       return true;

     }

   }

   JavaThread* thread = NULL;

   VMThread* vmthread = NULL;

   if (os::Solaris::signal_handlers_are_installed) {

     if (t != NULL ){

       if(t->is_Java_thread()) {

         thread = (JavaThread*)t;

       }

       else if(t->is_VM_thread()){

         vmthread = (VMThread *)t;

       }

     }

   }

   guarantee(sig != os::Solaris::SIGinterrupt(), "Can not chain VM interrupt signal, try -XX:+UseAltSigs");

   if (sig == os::Solaris::SIGasync()) {

     if(thread || vmthread){

       OSThread::SR_handler(t, uc);

       return true;

     } else if (os::Solaris::chained_handler(sig, info, ucVoid)) {

       return true;

     } else {

       // If os::Solaris::SIGasync not chained, and this is a non-vm and

       // non-java thread

       return true;

     }

   }

   if (info == NULL || info->si_code <= 0 || info->si_code == SI_NOINFO) {

     // can't decode this kind of signal

     info = NULL;

   } else {

     assert(sig == info->si_signo, "bad siginfo");

   }

   // decide if this trap can be handled by a stub

   address stub = NULL;

   address pc          = NULL;

   //%note os_trap_1

   if (info != NULL && uc != NULL && thread != NULL) {

     // factor me: getPCfromContext

     pc = (address) uc->uc_mcontext.gregs[REG_PC];

     if (StubRoutines::is_safefetch_fault(pc)) {

       uc->uc_mcontext.gregs[REG_PC] = intptr_t(StubRoutines::continuation_for_safefetch_fault(pc));

       return true;

     }

     // Handle ALL stack overflow variations here

     if (sig == SIGSEGV && info->si_code == SEGV_ACCERR) {

       address addr = (address) info->si_addr;

       if (thread->in_stack_yellow_zone(addr)) {

         thread->disable_stack_yellow_zone();

         if (thread->thread_state() == _thread_in_Java) {

           // Throw a stack overflow exception.  Guard pages will be reenabled

           // while unwinding the stack.

           stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::STACK_OVERFLOW);

         } else {

           // Thread was in the vm or native code.  Return and try to finish.

           return true;

         }

       } else if (thread->in_stack_red_zone(addr)) {

         // Fatal red zone violation.  Disable the guard pages and fall through

         // to handle_unexpected_exception way down below.

         thread->disable_stack_red_zone();

         tty->print_raw_cr("An irrecoverable stack overflow has occurred.");

       }

     }

     if (thread->thread_state() == _thread_in_vm) {

       if (sig == SIGBUS && info->si_code == BUS_OBJERR && thread->doing_unsafe_access()) {

         stub = StubRoutines::handler_for_unsafe_access();

       }

     }

     if (thread->thread_state() == _thread_in_Java) {

       // Support Safepoint Polling

       if ( sig == SIGSEGV && os::is_poll_address((address)info->si_addr)) {

         stub = SharedRuntime::get_poll_stub(pc);

       }

       else if (sig == SIGBUS && info->si_code == BUS_OBJERR) {

         // BugId 4454115: A read from a MappedByteBuffer can fault

         // here if the underlying file has been truncated.

         // Do not crash the VM in such a case.

         CodeBlob* cb = CodeCache::find_blob_unsafe(pc);

         nmethod* nm = cb->is_nmethod() ? (nmethod*)cb : NULL;

         if (nm != NULL && nm->has_unsafe_access()) {

           stub = StubRoutines::handler_for_unsafe_access();

         }

       }

       else

       if (sig == SIGFPE && info->si_code == FPE_INTDIV) {

         // integer divide by zero

         stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_DIVIDE_BY_ZERO);

       }

 #ifndef AMD64

       else if (sig == SIGFPE && info->si_code == FPE_FLTDIV) {

         // floating-point divide by zero

         stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_DIVIDE_BY_ZERO);

       }

       else if (sig == SIGFPE && info->si_code == FPE_FLTINV) {

         // The encoding of D2I in i486.ad can cause an exception prior

         // to the fist instruction if there was an invalid operation

         // pending. We want to dismiss that exception. From the win_32

         // side it also seems that if it really was the fist causing

         // the exception that we do the d2i by hand with different

         // rounding. Seems kind of weird. QQQ TODO

         // Note that we take the exception at the NEXT floating point instruction.

         if (pc[0] == 0xDB) {

             assert(pc[0] == 0xDB, "not a FIST opcode");

             assert(pc[1] == 0x14, "not a FIST opcode");

             assert(pc[2] == 0x24, "not a FIST opcode");

             return true;

         } else {

             assert(pc[-3] == 0xDB, "not an flt invalid opcode");

             assert(pc[-2] == 0x14, "not an flt invalid opcode");

             assert(pc[-1] == 0x24, "not an flt invalid opcode");

         }

       }

       else if (sig == SIGFPE ) {

         tty->print_cr("caught SIGFPE, info 0x%x.", info->si_code);

       }

 #endif // !AMD64

         // QQQ It doesn't seem that we need to do this on x86 because we should be able

         // to return properly from the handler without this extra stuff on the back side.

       else if (sig == SIGSEGV && info->si_code > 0 && !MacroAssembler::needs_explicit_null_check((intptr_t)info->si_addr)) {

         // Determination of interpreter/vtable stub/compiled code null exception

         stub = SharedRuntime::continuation_for_implicit_exception(thread, pc, SharedRuntime::IMPLICIT_NULL);

       }

     }

     // jni_fast_Get<Primitive>Field can trap at certain pc's if a GC kicks in

     // and the heap gets shrunk before the field access.

     if ((sig == SIGSEGV) || (sig == SIGBUS)) {

       address addr = JNI_FastGetField::find_slowcase_pc(pc);

       if (addr != (address)-1) {

         stub = addr;

       }

     }

     // Check to see if we caught the safepoint code in the

     // process of write protecting the memory serialization page.

     // It write enables the page immediately after protecting it

     // so we can just return to retry the write.

     if ((sig == SIGSEGV) &&

         os::is_memory_serialize_page(thread, (address)info->si_addr)) {

       // Block current thread until the memory serialize page permission restored.

       os::block_on_serialize_page_trap();

       return true;

     }

   }

   // Execution protection violation

   //

   // Preventative code for future versions of Solaris which may

   // enable execution protection when running the 32-bit VM on AMD64.

   //

   // This should be kept as the last step in the triage.  We don't

   // have a dedicated trap number for a no-execute fault, so be

   // conservative and allow other handlers the first shot.

   //

   // Note: We don't test that info->si_code == SEGV_ACCERR here.

   // this si_code is so generic that it is almost meaningless; and

   // the si_code for this condition may change in the future.

   // Furthermore, a false-positive should be harmless.

   if (UnguardOnExecutionViolation > 0 &&

       (sig == SIGSEGV || sig == SIGBUS) &&

       uc->uc_mcontext.gregs[TRAPNO] == T_PGFLT) {  // page fault

     int page_size = os::vm_page_size();

     address addr = (address) info->si_addr;

     address pc = (address) uc->uc_mcontext.gregs[REG_PC];

     // Make sure the pc and the faulting address are sane.

     //

     // If an instruction spans a page boundary, and the page containing

     // the beginning of the instruction is executable but the following

     // page is not, the pc and the faulting address might be slightly

     // different - we still want to unguard the 2nd page in this case.

     //

     // 15 bytes seems to be a (very) safe value for max instruction size.

     bool pc_is_near_addr =

       (pointer_delta((void*) addr, (void*) pc, sizeof(char)) < 15);

     bool instr_spans_page_boundary =

       (align_size_down((intptr_t) pc ^ (intptr_t) addr,

                        (intptr_t) page_size) > 0);

     if (pc == addr || (pc_is_near_addr && instr_spans_page_boundary)) {

       static volatile address last_addr =

         (address) os::non_memory_address_word();

       // In conservative mode, don't unguard unless the address is in the VM

       if (addr != last_addr &&

           (UnguardOnExecutionViolation > 1 || os::address_is_in_vm(addr))) {

         // Make memory rwx and retry

         address page_start =

           (address) align_size_down((intptr_t) addr, (intptr_t) page_size);

         bool res = os::protect_memory((char*) page_start, page_size,

                                       os::MEM_PROT_RWX);

         if (PrintMiscellaneous && Verbose) {

           char buf[256];

           jio_snprintf(buf, sizeof(buf), "Execution protection violation "

                        "at " INTPTR_FORMAT

                        ", unguarding " INTPTR_FORMAT ": %s, errno=%d", addr,

                        page_start, (res ? "success" : "failed"), errno);

           tty->print_raw_cr(buf);

         }

         stub = pc;

         // Set last_addr so if we fault again at the same address, we don't end

         // up in an endless loop.

         //

         // There are two potential complications here.  Two threads trapping at

         // the same address at the same time could cause one of the threads to

         // think it already unguarded, and abort the VM.  Likely very rare.

         //

         // The other race involves two threads alternately trapping at

         // different addresses and failing to unguard the page, resulting in

         // an endless loop.  This condition is probably even more unlikely than

         // the first.

         //

         // Although both cases could be avoided by using locks or thread local

         // last_addr, these solutions are unnecessary complication: this

         // handler is a best-effort safety net, not a complete solution.  It is

         // disabled by default and should only be used as a workaround in case

         // we missed any no-execute-unsafe VM code.

         last_addr = addr;

       }

     }

   }

   if (stub != NULL) {

     // save all thread context in case we need to restore it

     if (thread != NULL) thread->set_saved_exception_pc(pc);

     // 12/02/99: On Sparc it appears that the full context is also saved

     // but as yet, no one looks at or restores that saved context

     // factor me: setPC

     uc->uc_mcontext.gregs[REG_PC] = (greg_t)stub;

     return true;

   }

   // signal-chaining

   if (os::Solaris::chained_handler(sig, info, ucVoid)) {

     return true;

   }

 #ifndef AMD64

   // Workaround (bug 4900493) for Solaris kernel bug 4966651.

   // Handle an undefined selector caused by an attempt to assign

   // fs in libthread getipriptr(). With the current libthread design every 512

   // thread creations the LDT for a private thread data structure is extended

   // and thre is a hazard that and another thread attempting a thread creation

   // will use a stale LDTR that doesn't reflect the structure's growth,

   // causing a GP fault.

   // Enforce the probable limit of passes through here to guard against an

   // infinite loop if some other move to fs caused the GP fault. Note that

   // this loop counter is ultimately a heuristic as it is possible for

   // more than one thread to generate this fault at a time in an MP system.

   // In the case of the loop count being exceeded or if the poll fails

   // just fall through to a fatal error.

   // If there is some other source of T_GPFLT traps and the text at EIP is

   // unreadable this code will loop infinitely until the stack is exausted.

   // The key to diagnosis in this case is to look for the bottom signal handler

   // frame.

   if(! IgnoreLibthreadGPFault) {

     if (sig == SIGSEGV && uc->uc_mcontext.gregs[TRAPNO] == T_GPFLT) {

       const unsigned char *p =

                         (unsigned const char *) uc->uc_mcontext.gregs[EIP];

       // Expected instruction?

       if(p[0] == movlfs[0] && p[1] == movlfs[1]) {

         Atomic::inc(&ldtr_refresh);

         // Infinite loop?

         if(ldtr_refresh < ((2 << 16) / PAGESIZE)) {

           // No, force scheduling to get a fresh view of the LDTR

           if(poll(NULL, 0, 10) == 0) {

             // Retry the move

             return false;

           }

         }

       }

     }

   }

 #endif // !AMD64

   if (!abort_if_unrecognized) {

     // caller wants another chance, so give it to him

     return false;

   }

   if (!os::Solaris::libjsig_is_loaded) {

     struct sigaction oldAct;

     sigaction(sig, (struct sigaction *)0, &oldAct);

     if (oldAct.sa_sigaction != signalHandler) {

       void* sighand = oldAct.sa_sigaction ? CAST_FROM_FN_PTR(void*,  oldAct.sa_sigaction)

                                           : CAST_FROM_FN_PTR(void*, oldAct.sa_handler);

       warning("Unexpected Signal %d occurred under user-defined signal handler %#lx", sig, (long)sighand);

     }

   }

   if (pc == NULL && uc != NULL) {

     pc = (address) uc->uc_mcontext.gregs[REG_PC];

   }

   // unmask current signal

   sigset_t newset;

   sigemptyset(&newset);

   sigaddset(&newset, sig);

   sigprocmask(SIG_UNBLOCK, &newset, NULL);

   // Determine which sort of error to throw.  Out of swap may signal

   // on the thread stack, which could get a mapping error when touched.

   address addr = (address) info->si_addr;

   if (sig == SIGBUS && info->si_code == BUS_OBJERR && info->si_errno == ENOMEM) {

     vm_exit_out_of_memory(0, OOM_MMAP_ERROR, "Out of swap space to map in thread stack.");

   }

   VMError err(t, sig, pc, info, ucVoid);

   err.report_and_die();

   ShouldNotReachHere();

 }

 void os::print_context(outputStream *st, void *context) {

   if (context == NULL) return;

   ucontext_t *uc = (ucontext_t*)context;

   st->print_cr("Registers:");

 #ifdef AMD64

   st->print(  "RAX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RAX]);

   st->print(", RBX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RBX]);

   st->print(", RCX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RCX]);

   st->print(", RDX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RDX]);

   st->cr();

   st->print(  "RSP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RSP]);

   st->print(", RBP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RBP]);

   st->print(", RSI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RSI]);

   st->print(", RDI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RDI]);

   st->cr();

   st->print(  "R8 =" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R8]);

   st->print(", R9 =" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R9]);

   st->print(", R10=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R10]);

   st->print(", R11=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R11]);

   st->cr();

   st->print(  "R12=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R12]);

   st->print(", R13=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R13]);

   st->print(", R14=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R14]);

   st->print(", R15=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_R15]);

   st->cr();

   st->print(  "RIP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RIP]);

   st->print(", RFLAGS=" INTPTR_FORMAT, uc->uc_mcontext.gregs[REG_RFL]);

 #else

   st->print(  "EAX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[EAX]);

   st->print(", EBX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[EBX]);

   st->print(", ECX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[ECX]);

   st->print(", EDX=" INTPTR_FORMAT, uc->uc_mcontext.gregs[EDX]);

   st->cr();

   st->print(  "ESP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[UESP]);

   st->print(", EBP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[EBP]);

   st->print(", ESI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[ESI]);

   st->print(", EDI=" INTPTR_FORMAT, uc->uc_mcontext.gregs[EDI]);

   st->cr();

   st->print(  "EIP=" INTPTR_FORMAT, uc->uc_mcontext.gregs[EIP]);

   st->print(", EFLAGS=" INTPTR_FORMAT, uc->uc_mcontext.gregs[EFL]);

 #endif // AMD64

   st->cr();

   st->cr();

   intptr_t *sp = (intptr_t *)os::Solaris::ucontext_get_sp(uc);

   st->print_cr("Top of Stack: (sp=" PTR_FORMAT ")", sp);

   print_hex_dump(st, (address)sp, (address)(sp + 8*sizeof(intptr_t)), sizeof(intptr_t));

   st->cr();

   // Note: it may be unsafe to inspect memory near pc. For example, pc may

   // point to garbage if entry point in an nmethod is corrupted. Leave

   // this at the end, and hope for the best.

   ExtendedPC epc = os::Solaris::ucontext_get_ExtendedPC(uc);

   address pc = epc.pc();

   st->print_cr("Instructions: (pc=" PTR_FORMAT ")", pc);

   print_hex_dump(st, pc - 32, pc + 32, sizeof(char));

 }

 void os::print_register_info(outputStream *st, void *context) {

   if (context == NULL) return;

   ucontext_t *uc = (ucontext_t*)context;

   st->print_cr("Register to memory mapping:");

   st->cr();

   // this is horrendously verbose but the layout of the registers in the

   // context does not match how we defined our abstract Register set, so

   // we can't just iterate through the gregs area

   // this is only for the "general purpose" registers

 #ifdef AMD64

   st->print("RAX="); print_location(st, uc->uc_mcontext.gregs[REG_RAX]);

   st->print("RBX="); print_location(st, uc->uc_mcontext.gregs[REG_RBX]);

   st->print("RCX="); print_location(st, uc->uc_mcontext.gregs[REG_RCX]);

   st->print("RDX="); print_location(st, uc->uc_mcontext.gregs[REG_RDX]);

   st->print("RSP="); print_location(st, uc->uc_mcontext.gregs[REG_RSP]);

   st->print("RBP="); print_location(st, uc->uc_mcontext.gregs[REG_RBP]);

   st->print("RSI="); print_location(st, uc->uc_mcontext.gregs[REG_RSI]);

   st->print("RDI="); print_location(st, uc->uc_mcontext.gregs[REG_RDI]);

   st->print("R8 ="); print_location(st, uc->uc_mcontext.gregs[REG_R8]);

   st->print("R9 ="); print_location(st, uc->uc_mcontext.gregs[REG_R9]);

   st->print("R10="); print_location(st, uc->uc_mcontext.gregs[REG_R10]);

   st->print("R11="); print_location(st, uc->uc_mcontext.gregs[REG_R11]);

   st->print("R12="); print_location(st, uc->uc_mcontext.gregs[REG_R12]);

   st->print("R13="); print_location(st, uc->uc_mcontext.gregs[REG_R13]);

   st->print("R14="); print_location(st, uc->uc_mcontext.gregs[REG_R14]);

   st->print("R15="); print_location(st, uc->uc_mcontext.gregs[REG_R15]);

 #else

   st->print("EAX="); print_location(st, uc->uc_mcontext.gregs[EAX]);

   st->print("EBX="); print_location(st, uc->uc_mcontext.gregs[EBX]);

   st->print("ECX="); print_location(st, uc->uc_mcontext.gregs[ECX]);

   st->print("EDX="); print_location(st, uc->uc_mcontext.gregs[EDX]);

   st->print("ESP="); print_location(st, uc->uc_mcontext.gregs[UESP]);

   st->print("EBP="); print_location(st, uc->uc_mcontext.gregs[EBP]);

   st->print("ESI="); print_location(st, uc->uc_mcontext.gregs[ESI]);

   st->print("EDI="); print_location(st, uc->uc_mcontext.gregs[EDI]);

 #endif

   st->cr();

 }

 #ifdef AMD64

 void os::Solaris::init_thread_fpu_state(void) {

   // Nothing to do

 }

 #else

 // From solaris_i486.s

 extern "C" void fixcw();

 void os::Solaris::init_thread_fpu_state(void) {

   // Set fpu to 53 bit precision. This happens too early to use a stub.

   fixcw();

 }

 // These routines are the initial value of atomic_xchg_entry(),

 // atomic_cmpxchg_entry(), atomic_inc_entry() and fence_entry()

 // until initialization is complete.

 // TODO - replace with .il implementation when compiler supports it.

 typedef jint  xchg_func_t        (jint,  volatile jint*);

 typedef jint  cmpxchg_func_t     (jint,  volatile jint*,  jint);

 typedef jlong cmpxchg_long_func_t(jlong, volatile jlong*, jlong);

 typedef jint  add_func_t         (jint,  volatile jint*);

 jint os::atomic_xchg_bootstrap(jint exchange_value, volatile jint* dest) {

   // try to use the stub:

   xchg_func_t* func = CAST_TO_FN_PTR(xchg_func_t*, StubRoutines::atomic_xchg_entry());

   if (func != NULL) {

     os::atomic_xchg_func = func;

     return (*func)(exchange_value, dest);

   }

   assert(Threads::number_of_threads() == 0, "for bootstrap only");

   jint old_value = *dest;

   *dest = exchange_value;

   return old_value;

 }

 jint os::atomic_cmpxchg_bootstrap(jint exchange_value, volatile jint* dest, jint compare_value) {

   // try to use the stub:

   cmpxchg_func_t* func = CAST_TO_FN_PTR(cmpxchg_func_t*, StubRoutines::atomic_cmpxchg_entry());

   if (func != NULL) {

     os::atomic_cmpxchg_func = func;

     return (*func)(exchange_value, dest, compare_value);

   }

   assert(Threads::number_of_threads() == 0, "for bootstrap only");

   jint old_value = *dest;

   if (old_value == compare_value)

     *dest = exchange_value;

   return old_value;

 }

 jlong os::atomic_cmpxchg_long_bootstrap(jlong exchange_value, volatile jlong* dest, jlong compare_value) {

   // try to use the stub:

   cmpxchg_long_func_t* func = CAST_TO_FN_PTR(cmpxchg_long_func_t*, StubRoutines::atomic_cmpxchg_long_entry());

   if (func != NULL) {

     os::atomic_cmpxchg_long_func = func;

     return (*func)(exchange_value, dest, compare_value);

   }

   assert(Threads::number_of_threads() == 0, "for bootstrap only");

   jlong old_value = *dest;

   if (old_value == compare_value)

     *dest = exchange_value;

   return old_value;

 }

 jint os::atomic_add_bootstrap(jint add_value, volatile jint* dest) {

   // try to use the stub:

   add_func_t* func = CAST_TO_FN_PTR(add_func_t*, StubRoutines::atomic_add_entry());

   if (func != NULL) {

     os::atomic_add_func = func;

     return (*func)(add_value, dest);

   }

   assert(Threads::number_of_threads() == 0, "for bootstrap only");

   return (*dest) += add_value;

 }

 xchg_func_t*         os::atomic_xchg_func         = os::atomic_xchg_bootstrap;

 cmpxchg_func_t*      os::atomic_cmpxchg_func      = os::atomic_cmpxchg_bootstrap;

 cmpxchg_long_func_t* os::atomic_cmpxchg_long_func = os::atomic_cmpxchg_long_bootstrap;

 add_func_t*          os::atomic_add_func          = os::atomic_add_bootstrap;

 extern "C" void _solaris_raw_setup_fpu(address ptr);

 void os::setup_fpu() {

   address fpu_cntrl = StubRoutines::addr_fpu_cntrl_wrd_std();

   _solaris_raw_setup_fpu(fpu_cntrl);

 }

 #endif // AMD64

 #ifndef PRODUCT

 void os::verify_stack_alignment() {

 #ifdef AMD64

   assert(((intptr_t)os::current_stack_pointer() & (StackAlignmentInBytes-1)) == 0, "incorrect stack alignment");

 #endif

 }

 #endif