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
31static const char* file_separator() { return "/"; }
32static const char* line_separator() { return "\n"; }
33static const char* path_separator() { return ":"; }
34
35class Posix {
36 friend class os;
37
38protected:
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
55public:
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
129private:
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 *);
133public:
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 */
156class ThreadCrashProtection : public StackObj {
157public:
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);
166private:
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 */
183class 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
218class 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
246class 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
300