1 /*
   2  * Copyright (c) 1999, 2019, 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_OS_POSIX_HPP
  28 #define OS_POSIX_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   static bool is_sig_ignored(int sig);
  68 
  69   // Helper function, returns a string (e.g. "SIGILL") for a signal.
  70   // Returned string is a constant. For unknown signals "UNKNOWN" is returned.
  71   static const char* get_signal_name(int sig, char* out, size_t outlen);
  72 
  73   // Helper function, returns a signal number for a given signal name, e.g. 11
  74   // for "SIGSEGV". Name can be given with or without "SIG" prefix, so both
  75   // "SEGV" or "SIGSEGV" work. Name must be uppercase.
  76   // Returns -1 for an unknown signal name.
  77   static int get_signal_number(const char* signal_name);
  78 
  79   // Returns one-line short description of a signal set in a user provided buffer.
  80   static const char* describe_signal_set_short(const sigset_t* set, char* buffer, size_t size);
  81 
  82   // Prints a short one-line description of a signal set.
  83   static void print_signal_set_short(outputStream* st, const sigset_t* set);
  84 
  85   // unblocks the signal masks for current thread
  86   static int unblock_thread_signal_mask(const sigset_t *set);
  87 
  88   // Writes a one-line description of a combination of sigaction.sa_flags
  89   // into a user provided buffer. Returns that buffer.
  90   static const char* describe_sa_flags(int flags, char* buffer, size_t size);
  91 
  92   // Prints a one-line description of a combination of sigaction.sa_flags.
  93   static void print_sa_flags(outputStream* st, int flags);
  94 
  95   static address ucontext_get_pc(const ucontext_t* ctx);
  96   // Set PC into context. Needed for continuation after signal.
  97   static void ucontext_set_pc(ucontext_t* ctx, address pc);
  98 
  99   // Helper function; describes pthread attributes as short string. String is written
 100   // to buf with len buflen; buf is returned.
 101   static char* describe_pthread_attr(char* buf, size_t buflen, const pthread_attr_t* attr);
 102 
 103   // A safe implementation of realpath which will not cause a buffer overflow if the resolved path
 104   //   is longer than PATH_MAX.
 105   // On success, returns 'outbuf', which now contains the path.
 106   // On error, it will return NULL and set errno. The content of 'outbuf' is undefined.
 107   // On truncation error ('outbuf' too small), it will return NULL and set errno to ENAMETOOLONG.
 108   static char* realpath(const char* filename, char* outbuf, size_t outbuflen);
 109 
 110   // Returns true if given uid is root.
 111   static bool is_root(uid_t uid);
 112 
 113   // Returns true if given uid is effective or root uid.
 114   static bool matches_effective_uid_or_root(uid_t uid);
 115 
 116   // Returns true if either given uid is effective uid and given gid is
 117   // effective gid, or if given uid is root.
 118   static bool matches_effective_uid_and_gid_or_root(uid_t uid, gid_t gid);
 119 
 120   static struct sigaction *get_preinstalled_handler(int);
 121   static void save_preinstalled_handler(int, struct sigaction&);
 122 
 123   static void print_umask(outputStream* st, mode_t umsk);
 124 
 125   static void print_user_info(outputStream* st);
 126 
 127 #ifdef SUPPORTS_CLOCK_MONOTONIC
 128 
 129 private:
 130   // These need to be members so we can access them from inline functions
 131   static int (*_clock_gettime)(clockid_t, struct timespec *);
 132   static int (*_clock_getres)(clockid_t, struct timespec *);
 133 public:
 134   static bool supports_monotonic_clock();
 135   static int clock_gettime(clockid_t clock_id, struct timespec *tp);
 136   static int clock_getres(clockid_t clock_id, struct timespec *tp);
 137 
 138 #else
 139 
 140   static bool supports_monotonic_clock() { return false; }
 141 
 142 #endif
 143 
 144   static void to_RTC_abstime(timespec* abstime, int64_t millis);
 145 };
 146 
 147 /*
 148  * Crash protection for the watcher thread. Wrap the callback
 149  * with a sigsetjmp and in case of a SIGSEGV/SIGBUS we siglongjmp
 150  * back.
 151  * To be able to use this - don't take locks, don't rely on destructors,
 152  * don't make OS library calls, don't allocate memory, don't print,
 153  * don't call code that could leave the heap / memory in an inconsistent state,
 154  * or anything else where we are not in control if we suddenly jump out.
 155  */
 156 class ThreadCrashProtection : public StackObj {
 157 public:
 158   static bool is_crash_protected(Thread* thr) {
 159     return _crash_protection != NULL && _protected_thread == thr;
 160   }
 161 
 162   ThreadCrashProtection();
 163   bool call(os::CrashProtectionCallback& cb);
 164 
 165   static void check_crash_protection(int signal, Thread* thread);
 166 private:
 167   static Thread* _protected_thread;
 168   static ThreadCrashProtection* _crash_protection;
 169   static volatile intptr_t _crash_mux;
 170   void restore();
 171   sigjmp_buf _jmpbuf;
 172 };
 173 
 174 #ifndef SOLARIS
 175 
 176 /*
 177  * This is the platform-specific implementation underpinning
 178  * the ParkEvent class, which itself underpins Java-level monitor
 179  * operations. See park.hpp for details.
 180  * These event objects are type-stable and immortal - we never delete them.
 181  * Events are associated with a thread for the lifetime of the thread.
 182  */
 183 class PlatformEvent : public CHeapObj<mtSynchronizer> {
 184  private:
 185   double cachePad[4];        // Increase odds that _mutex is sole occupant of cache line
 186   volatile int _event;       // Event count/permit: -1, 0 or 1
 187   volatile int _nParked;     // Indicates if associated thread is blocked: 0 or 1
 188   pthread_mutex_t _mutex[1]; // Native mutex for locking
 189   pthread_cond_t  _cond[1];  // Native condition variable for blocking
 190   double postPad[2];
 191 
 192  protected:       // TODO-FIXME: make dtor private
 193   ~PlatformEvent() { guarantee(false, "invariant"); } // immortal so can't delete
 194 
 195  public:
 196   PlatformEvent();
 197   void park();
 198   int  park(jlong millis);
 199   void unpark();
 200 
 201   // Use caution with reset() and fired() -- they may require MEMBARs
 202   void reset() { _event = 0; }
 203   int  fired() { return _event; }
 204 };
 205 
 206 // JSR166 support
 207 // PlatformParker provides the platform dependent base class for the
 208 // Parker class. It basically provides the internal data structures:
 209 // - mutex and convars
 210 // which are then used directly by the Parker methods defined in the OS
 211 // specific implementation files.
 212 // There is significant overlap between the funcionality supported in the
 213 // combination of Parker+PlatformParker and PlatformEvent (above). If Parker
 214 // were more like ObjectMonitor we could use PlatformEvent in both (with some
 215 // API updates of course). But Parker methods use fastpaths that break that
 216 // level of encapsulation - so combining the two remains a future project.
 217 
 218 class PlatformParker : public CHeapObj<mtSynchronizer> {
 219  protected:
 220   enum {
 221     REL_INDEX = 0,
 222     ABS_INDEX = 1
 223   };
 224   int _cur_index;  // which cond is in use: -1, 0, 1
 225   pthread_mutex_t _mutex[1];
 226   pthread_cond_t  _cond[2]; // one for relative times and one for absolute
 227 
 228  public:       // TODO-FIXME: make dtor private
 229   ~PlatformParker() { guarantee(false, "invariant"); }
 230 
 231  public:
 232   PlatformParker();
 233 };
 234 
 235 // Workaround for a bug in macOSX kernel's pthread support (fixed in Mojave?).
 236 // Avoid ever allocating a pthread_mutex_t at the same address as one of our
 237 // former pthread_cond_t, by using a freelist of mutex/condvar pairs.
 238 // Conditional to avoid extra indirection and padding loss on other platforms.
 239 #ifdef __APPLE__
 240 #define PLATFORM_MONITOR_IMPL_INDIRECT 1
 241 #else
 242 #define PLATFORM_MONITOR_IMPL_INDIRECT 0
 243 #endif
 244 
 245 // Platform specific implementation that underpins VM Monitor/Mutex class
 246 class PlatformMonitor : public CHeapObj<mtSynchronizer> {
 247   class Impl : public CHeapObj<mtSynchronizer> {
 248   public:
 249     pthread_mutex_t _mutex;
 250     pthread_cond_t _cond;
 251     Impl* _next;
 252 
 253     Impl();
 254     ~Impl();
 255   };
 256 
 257 #if PLATFORM_MONITOR_IMPL_INDIRECT
 258 
 259   Impl* _impl;
 260 
 261   pthread_mutex_t* mutex() { return &(_impl->_mutex); }
 262   pthread_cond_t* cond() { return &(_impl->_cond); }
 263 
 264   class WithFreeListLocked;
 265   static pthread_mutex_t _freelist_lock;
 266   static Impl* _freelist;
 267 
 268  public:
 269   PlatformMonitor();            // Use freelist allocation of impl.
 270   ~PlatformMonitor();
 271 
 272   static void init();           // Initialize the freelist.
 273 
 274 #else
 275 
 276   Impl _impl;
 277 
 278   pthread_mutex_t* mutex() { return &(_impl._mutex); }
 279   pthread_cond_t* cond() { return &(_impl._cond); }
 280 
 281  public:
 282   static void init() {}         // Nothing needed for the non-indirect case.
 283 
 284   // Default constructor and destructor.
 285 
 286 #endif // PLATFORM_MONITOR_IMPL_INDIRECT
 287 
 288  public:
 289   void lock();
 290   void unlock();
 291   bool try_lock();
 292   int wait(jlong millis);
 293   void notify();
 294   void notify_all();
 295 };
 296 
 297 #endif // !SOLARIS
 298 
 299 #endif // OS_POSIX_OS_POSIX_HPP