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
--- EOF ---