1 /*

     2  * Copyright (c) 1999, 2017, 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 #include "runtime/os.hpp"

    26 

    27 #ifndef OS_POSIX_VM_OS_POSIX_HPP

    28 #define OS_POSIX_VM_OS_POSIX_HPP

    29 

    30 // File conventions

    31 static const char* file_separator() { return "/"; }

    32 static const char* line_separator() { return "\n"; }

    33 static const char* path_separator() { return ":"; }

    34 

    35 class Posix {

    36   friend class os;

    37 

    38 protected:

    39   static void print_distro_info(outputStream* st);

    40   static void print_rlimit_info(outputStream* st);

    41   static void print_uname_info(outputStream* st);

    42   static void print_libversion_info(outputStream* st);

    43   static void print_load_average(outputStream* st);

    44 

    45   // Minimum stack size a thread can be created with (allowing

    46   // the VM to completely create the thread and enter user code).

    47   // The initial values exclude any guard pages (by HotSpot or libc).

    48   // set_minimum_stack_sizes() will add the size required for

    49   // HotSpot guard pages depending on page size and flag settings.

    50   // Libc guard pages are never considered by these values.

    51   static size_t _compiler_thread_min_stack_allowed;

    52   static size_t _java_thread_min_stack_allowed;

    53   static size_t _vm_internal_thread_min_stack_allowed;

    54 

    55 public:

    56   static void init(void);  // early initialization - no logging available

    57   static void init_2(void);// later initialization - logging available

    58 

    59   // Return default stack size for the specified thread type

    60   static size_t default_stack_size(os::ThreadType thr_type);

    61   // Check and sets minimum stack sizes

    62   static jint set_minimum_stack_sizes();

    63   static size_t get_initial_stack_size(ThreadType thr_type, size_t req_stack_size);

    64 

    65   // Returns true if signal is valid.

    66   static bool is_valid_signal(int sig);

    67 

    68   // Helper function, returns a string (e.g. "SIGILL") for a signal.

    69   // Returned string is a constant. For unknown signals "UNKNOWN" is returned.

    70   static const char* get_signal_name(int sig, char* out, size_t outlen);

    71 

    72   // Helper function, returns a signal number for a given signal name, e.g. 11

    73   // for "SIGSEGV". Name can be given with or without "SIG" prefix, so both

    74   // "SEGV" or "SIGSEGV" work. Name must be uppercase.

    75   // Returns -1 for an unknown signal name.

    76   static int get_signal_number(const char* signal_name);

    77 

    78   // Returns one-line short description of a signal set in a user provided buffer.

    79   static const char* describe_signal_set_short(const sigset_t* set, char* buffer, size_t size);

    80 

    81   // Prints a short one-line description of a signal set.

    82   static void print_signal_set_short(outputStream* st, const sigset_t* set);

    83 

    84   // unblocks the signal masks for current thread

    85   static int unblock_thread_signal_mask(const sigset_t *set);

    86 

    87   // Writes a one-line description of a combination of sigaction.sa_flags

    88   // into a user provided buffer. Returns that buffer.

    89   static const char* describe_sa_flags(int flags, char* buffer, size_t size);

    90 

    91   // Prints a one-line description of a combination of sigaction.sa_flags.

    92   static void print_sa_flags(outputStream* st, int flags);

    93 

    94   static address ucontext_get_pc(const ucontext_t* ctx);

    95   // Set PC into context. Needed for continuation after signal.

    96   static void ucontext_set_pc(ucontext_t* ctx, address pc);

    97 

    98   // Helper function; describes pthread attributes as short string. String is written

    99   // to buf with len buflen; buf is returned.

   100   static char* describe_pthread_attr(char* buf, size_t buflen, const pthread_attr_t* attr);

   101 

   102   // A safe implementation of realpath which will not cause a buffer overflow if the resolved path

   103   //   is longer than PATH_MAX.

   104   // On success, returns 'outbuf', which now contains the path.

   105   // On error, it will return NULL and set errno. The content of 'outbuf' is undefined.

   106   // On truncation error ('outbuf' too small), it will return NULL and set errno to ENAMETOOLONG.

   107   static char* realpath(const char* filename, char* outbuf, size_t outbuflen);

   108 };

   109 

   110 // On POSIX platforms the signal handler is global so we just do the write.

   111 static void write_memory_serialize_page_with_handler(JavaThread* thread) {

   112   write_memory_serialize_page(thread);

   113 }

   114 

   115 /*

   116  * Crash protection for the watcher thread. Wrap the callback

   117  * with a sigsetjmp and in case of a SIGSEGV/SIGBUS we siglongjmp

   118  * back.

   119  * To be able to use this - don't take locks, don't rely on destructors,

   120  * don't make OS library calls, don't allocate memory, don't print,

   121  * don't call code that could leave the heap / memory in an inconsistent state,

   122  * or anything else where we are not in control if we suddenly jump out.

   123  */

   124 class ThreadCrashProtection : public StackObj {

   125 public:

   126   static bool is_crash_protected(Thread* thr) {

   127     return _crash_protection != NULL && _protected_thread == thr;

   128   }

   129 

   130   ThreadCrashProtection();

   131   bool call(os::CrashProtectionCallback& cb);

   132 

   133   static void check_crash_protection(int signal, Thread* thread);

   134 private:

   135   static Thread* _protected_thread;

   136   static ThreadCrashProtection* _crash_protection;

   137   static volatile intptr_t _crash_mux;

   138   void restore();

   139   sigjmp_buf _jmpbuf;

   140 };

   141 

   142 #ifndef SOLARIS

   143 

   144 /*

   145  * This is the platform-specific implementation underpinning

   146  * the ParkEvent class, which itself underpins Java-level monitor

   147  * operations. See park.hpp for details.

   148  * These event objects are type-stable and immortal - we never delete them.

   149  * Events are associated with a thread for the lifetime of the thread.

   150  */

   151 class PlatformEvent : public CHeapObj<mtInternal> {

   152  private:

   153   double cachePad[4];        // Increase odds that _mutex is sole occupant of cache line

   154   volatile int _event;       // Event count/permit: -1, 0 or 1

   155   volatile int _nParked;     // Indicates if associated thread is blocked: 0 or 1

   156   pthread_mutex_t _mutex[1]; // Native mutex for locking

   157   pthread_cond_t  _cond[1];  // Native condition variable for blocking

   158   double postPad[2];

   159 

   160  protected:       // TODO-FIXME: make dtor private

   161   ~PlatformEvent() { guarantee(false, "invariant"); } // immortal so can't delete

   162 

   163  public:

   164   PlatformEvent();

   165   void park();

   166   int  park(jlong millis);

   167   void unpark();

   168 

   169   // Use caution with reset() and fired() -- they may require MEMBARs

   170   void reset() { _event = 0; }

   171   int  fired() { return _event; }

   172 };

   173 

   174 // JSR166 support

   175 // PlatformParker provides the platform dependent base class for the

   176 // Parker class. It basically provides the internal data structures:

   177 // - mutex and convars

   178 // which are then used directly by the Parker methods defined in the OS

   179 // specific implementation files.

   180 // There is significant overlap between the funcionality supported in the

   181 // combination of Parker+PlatformParker and PlatformEvent (above). If Parker

   182 // were more like ObjectMonitor we could use PlatformEvent in both (with some

   183 // API updates of course). But Parker methods use fastpaths that break that

   184 // level of encapsulation - so combining the two remains a future project.

   185 

   186 class PlatformParker : public CHeapObj<mtInternal> {

   187  protected:

   188   enum {

   189     REL_INDEX = 0,

   190     ABS_INDEX = 1

   191   };

   192   int _cur_index;  // which cond is in use: -1, 0, 1

   193   pthread_mutex_t _mutex[1];

   194   pthread_cond_t  _cond[2]; // one for relative times and one for absolute

   195 

   196  public:       // TODO-FIXME: make dtor private

   197   ~PlatformParker() { guarantee(false, "invariant"); }

   198 

   199  public:

   200   PlatformParker();

   201 };

   202 

   203 #endif // !SOLARIS

   204 

   205 #endif // OS_POSIX_VM_OS_POSIX_HPP