/*

 * Copyright (c) 1999, 2018, 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.

 *

 */

#include "runtime/os.hpp"

#ifndef OS_POSIX_VM_OS_POSIX_HPP

#define OS_POSIX_VM_OS_POSIX_HPP

// File conventions

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

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

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

class Posix {

  friend class os;

protected:

  static void print_distro_info(outputStream* st);

  static void print_rlimit_info(outputStream* st);

  static void print_uname_info(outputStream* st);

  static void print_libversion_info(outputStream* st);

  static void print_load_average(outputStream* st);

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

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

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

  // set_minimum_stack_sizes() will add the size required for

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

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

  static size_t _compiler_thread_min_stack_allowed;

  static size_t _java_thread_min_stack_allowed;

  static size_t _vm_internal_thread_min_stack_allowed;

public:

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

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

  // Return default stack size for the specified thread type

  static size_t default_stack_size(os::ThreadType thr_type);

  // Check and sets minimum stack sizes

  static jint set_minimum_stack_sizes();

  static size_t get_initial_stack_size(ThreadType thr_type, size_t req_stack_size);

  // Returns true if signal is valid.

  static bool is_valid_signal(int sig);

  static bool is_sig_ignored(int sig);

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

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

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

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

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

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

  // Returns -1 for an unknown signal name.

  static int get_signal_number(const char* signal_name);

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

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

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

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

  // unblocks the signal masks for current thread

  static int unblock_thread_signal_mask(const sigset_t *set);

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

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

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

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

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

  static address ucontext_get_pc(const ucontext_t* ctx);

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

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

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

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

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

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

  //   is longer than PATH_MAX.

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

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

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

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

  // Returns true if given uid is root.

  static bool is_root(uid_t uid);

  // Returns true if given uid is effective or root uid.

  static bool matches_effective_uid_or_root(uid_t uid);

  // Returns true if either given uid is effective uid and given gid is

  // effective gid, or if given uid is root.

  static bool matches_effective_uid_and_gid_or_root(uid_t uid, gid_t gid);

#ifdef SUPPORTS_CLOCK_MONOTONIC

  static bool supports_monotonic_clock();

  static int clock_gettime(clockid_t clock_id, struct timespec *tp);

  static int clock_getres(clockid_t clock_id, struct timespec *tp);

#else

  static bool supports_monotonic_clock() { return false; }

#endif

};

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

static void write_memory_serialize_page_with_handler(JavaThread* thread) {

  write_memory_serialize_page(thread);

}

/*

 * Crash protection for the watcher thread. Wrap the callback

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

 * back.

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

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

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

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

 */

class ThreadCrashProtection : public StackObj {

public:

  static bool is_crash_protected(Thread* thr) {

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

  }

  ThreadCrashProtection();

  bool call(os::CrashProtectionCallback& cb);

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

private:

  static Thread* _protected_thread;

  static ThreadCrashProtection* _crash_protection;

  static volatile intptr_t _crash_mux;

  void restore();

  sigjmp_buf _jmpbuf;

};

#ifndef SOLARIS

/*

 * This is the platform-specific implementation underpinning

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

 * operations. See park.hpp for details.

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

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

 */

class PlatformEvent : public CHeapObj<mtInternal> {

 private:

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

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

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

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

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

  double postPad[2];

 protected:       // TODO-FIXME: make dtor private

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

 public:

  PlatformEvent();

  void park();

  int  park(jlong millis);

  void unpark();

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

  void reset() { _event = 0; }

  int  fired() { return _event; }

};

// JSR166 support

// PlatformParker provides the platform dependent base class for the

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

// - mutex and convars

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

// specific implementation files.

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

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

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

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

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

class PlatformParker : public CHeapObj<mtInternal> {

 protected:

  enum {

    REL_INDEX = 0,

    ABS_INDEX = 1

  };

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

  pthread_mutex_t _mutex[1];

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

 public:       // TODO-FIXME: make dtor private

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

 public:

  PlatformParker();

};

#endif // !SOLARIS

#endif // OS_POSIX_VM_OS_POSIX_HPP