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 static void print_uptime_info(outputStream* st);
45
46 // Minimum stack size a thread can be created with (allowing
47 // the VM to completely create the thread and enter user code).
48 // The initial values exclude any guard pages (by HotSpot or libc).
49 // set_minimum_stack_sizes() will add the size required for
50 // HotSpot guard pages depending on page size and flag settings.
51 // Libc guard pages are never considered by these values.
52 static size_t _compiler_thread_min_stack_allowed;
53 static size_t _java_thread_min_stack_allowed;
54 static size_t _vm_internal_thread_min_stack_allowed;
55
56 public:
57 static void init(void); // early initialization - no logging available
58 static void init_2(void);// later initialization - logging available
59
60 // Return default stack size for the specified thread type
61 static size_t default_stack_size(os::ThreadType thr_type);
62 // Check and sets minimum stack sizes
63 static jint set_minimum_stack_sizes();
64 static size_t get_initial_stack_size(ThreadType thr_type, size_t req_stack_size);
65
66 // Returns true if signal is valid.
67 static bool is_valid_signal(int sig);
68 static bool is_sig_ignored(int sig);
69
70 // Helper function, returns a string (e.g. "SIGILL") for a signal.
71 // Returned string is a constant. For unknown signals "UNKNOWN" is returned.
72 static const char* get_signal_name(int sig, char* out, size_t outlen);
73
74 // Helper function, returns a signal number for a given signal name, e.g. 11
75 // for "SIGSEGV". Name can be given with or without "SIG" prefix, so both
76 // "SEGV" or "SIGSEGV" work. Name must be uppercase.
77 // Returns -1 for an unknown signal name.
78 static int get_signal_number(const char* signal_name);
79
80 // Returns one-line short description of a signal set in a user provided buffer.
81 static const char* describe_signal_set_short(const sigset_t* set, char* buffer, size_t size);
82
83 // Prints a short one-line description of a signal set.
84 static void print_signal_set_short(outputStream* st, const sigset_t* set);
85
86 // unblocks the signal masks for current thread
87 static int unblock_thread_signal_mask(const sigset_t *set);
88
89 // Writes a one-line description of a combination of sigaction.sa_flags
90 // into a user provided buffer. Returns that buffer.
91 static const char* describe_sa_flags(int flags, char* buffer, size_t size);
92
93 // Prints a one-line description of a combination of sigaction.sa_flags.
94 static void print_sa_flags(outputStream* st, int flags);
95
96 static address ucontext_get_pc(const ucontext_t* ctx);
97 // Set PC into context. Needed for continuation after signal.
98 static void ucontext_set_pc(ucontext_t* ctx, address pc);
99
100 // Helper function; describes pthread attributes as short string. String is written
101 // to buf with len buflen; buf is returned.
102 static char* describe_pthread_attr(char* buf, size_t buflen, const pthread_attr_t* attr);
103
104 // A safe implementation of realpath which will not cause a buffer overflow if the resolved path
105 // is longer than PATH_MAX.
106 // On success, returns 'outbuf', which now contains the path.
107 // On error, it will return NULL and set errno. The content of 'outbuf' is undefined.
108 // On truncation error ('outbuf' too small), it will return NULL and set errno to ENAMETOOLONG.
109 static char* realpath(const char* filename, char* outbuf, size_t outbuflen);
110
111 // Returns true if given uid is root.
112 static bool is_root(uid_t uid);
113
114 // Returns true if given uid is effective or root uid.
115 static bool matches_effective_uid_or_root(uid_t uid);
116
117 // Returns true if either given uid is effective uid and given gid is
118 // effective gid, or if given uid is root.
119 static bool matches_effective_uid_and_gid_or_root(uid_t uid, gid_t gid);
120
121 static struct sigaction *get_preinstalled_handler(int);
122 static void save_preinstalled_handler(int, struct sigaction&);
123
124 static void print_umask(outputStream* st, mode_t umsk);
125
126 static void print_user_info(outputStream* st);
127
128 #ifdef SUPPORTS_CLOCK_MONOTONIC
129
130 private:
131 // These need to be members so we can access them from inline functions
132 static int (*_clock_gettime)(clockid_t, struct timespec *);
133 static int (*_clock_getres)(clockid_t, struct timespec *);
134 public:
135 static bool supports_monotonic_clock();
136 static int clock_gettime(clockid_t clock_id, struct timespec *tp);
137 static int clock_getres(clockid_t clock_id, struct timespec *tp);
138
139 #else
140
141 static bool supports_monotonic_clock() { return false; }
142
143 #endif
144
145 static void to_RTC_abstime(timespec* abstime, int64_t millis);
146 };
147
148 /*
149 * Crash protection for the watcher thread. Wrap the callback
150 * with a sigsetjmp and in case of a SIGSEGV/SIGBUS we siglongjmp
151 * back.
152 * To be able to use this - don't take locks, don't rely on destructors,
153 * don't make OS library calls, don't allocate memory, don't print,
154 * don't call code that could leave the heap / memory in an inconsistent state,
155 * or anything else where we are not in control if we suddenly jump out.
156 */
157 class ThreadCrashProtection : public StackObj {
158 public:
159 static bool is_crash_protected(Thread* thr) {
160 return _crash_protection != NULL && _protected_thread == thr;
161 }
162
163 ThreadCrashProtection();
164 bool call(os::CrashProtectionCallback& cb);
165
166 static void check_crash_protection(int signal, Thread* thread);
167 private:
168 static Thread* _protected_thread;
169 static ThreadCrashProtection* _crash_protection;
170 static volatile intptr_t _crash_mux;
171 void restore();
172 sigjmp_buf _jmpbuf;
173 };
174
175 #ifndef SOLARIS
176
177 /*
178 * This is the platform-specific implementation underpinning
179 * the ParkEvent class, which itself underpins Java-level monitor
180 * operations. See park.hpp for details.
181 * These event objects are type-stable and immortal - we never delete them.
182 * Events are associated with a thread for the lifetime of the thread.
183 */
184 class PlatformEvent : public CHeapObj<mtSynchronizer> {
185 private:
186 double cachePad[4]; // Increase odds that _mutex is sole occupant of cache line
187 volatile int _event; // Event count/permit: -1, 0 or 1
188 volatile int _nParked; // Indicates if associated thread is blocked: 0 or 1
189 pthread_mutex_t _mutex[1]; // Native mutex for locking
190 pthread_cond_t _cond[1]; // Native condition variable for blocking
191 double postPad[2];
192
193 protected: // TODO-FIXME: make dtor private
194 ~PlatformEvent() { guarantee(false, "invariant"); } // immortal so can't delete
195
196 public:
197 PlatformEvent();
198 void park();
199 int park(jlong millis);
200 void unpark();
201
202 // Use caution with reset() and fired() -- they may require MEMBARs
203 void reset() { _event = 0; }
204 int fired() { return _event; }
205 };
206
207 // JSR166 support
208 // PlatformParker provides the platform dependent base class for the
209 // Parker class. It basically provides the internal data structures:
210 // - mutex and convars
211 // which are then used directly by the Parker methods defined in the OS
212 // specific implementation files.
213 // There is significant overlap between the funcionality supported in the
214 // combination of Parker+PlatformParker and PlatformEvent (above). If Parker
215 // were more like ObjectMonitor we could use PlatformEvent in both (with some
216 // API updates of course). But Parker methods use fastpaths that break that
217 // level of encapsulation - so combining the two remains a future project.
218
219 class PlatformParker : public CHeapObj<mtSynchronizer> {
220 protected:
221 enum {
222 REL_INDEX = 0,
223 ABS_INDEX = 1
224 };
225 int _cur_index; // which cond is in use: -1, 0, 1
226 pthread_mutex_t _mutex[1];
227 pthread_cond_t _cond[2]; // one for relative times and one for absolute
228
229 public: // TODO-FIXME: make dtor private
230 ~PlatformParker() { guarantee(false, "invariant"); }
231
232 public:
233 PlatformParker();
234 };
235
236 // Workaround for a bug in macOSX kernel's pthread support (fixed in Mojave?).
237 // Avoid ever allocating a pthread_mutex_t at the same address as one of our
238 // former pthread_cond_t, by using freelists of mutexes and condvars.
239 // Conditional to avoid extra indirection and padding loss on other platforms.
240 #ifdef __APPLE__
241 #define PLATFORM_MONITOR_IMPL_INDIRECT 1
242 #else
243 #define PLATFORM_MONITOR_IMPL_INDIRECT 0
244 #endif
245
246 // Platform specific implementations that underpin VM Mutex/Monitor classes
247
248 class PlatformMutex : public CHeapObj<mtSynchronizer> {
249 #if PLATFORM_MONITOR_IMPL_INDIRECT
250 class Mutex : public CHeapObj<mtSynchronizer> {
251 public:
252 pthread_mutex_t _mutex;
253 Mutex* _next;
254
255 Mutex();
256 ~Mutex();
257 };
258
259 Mutex* _impl;
260
261 static pthread_mutex_t _freelist_lock; // used for mutex and cond freelists
262 static Mutex* _mutex_freelist;
263
264 protected:
265 class WithFreeListLocked;
266 pthread_mutex_t* mutex() { return &(_impl->_mutex); }
267
268 public:
269 PlatformMutex(); // Use freelist allocation of impl.
270 ~PlatformMutex();
271
272 static void init(); // Initialize the freelist.
273
274 #else
275
276 pthread_mutex_t _mutex;
277
278 protected:
279 pthread_mutex_t* mutex() { return &_mutex; }
280
281 public:
282 static void init() {} // Nothing needed for the non-indirect case.
283
284 PlatformMutex();
285 ~PlatformMutex();
286
287 #endif // PLATFORM_MONITOR_IMPL_INDIRECT
288
289 private:
290 NONCOPYABLE(PlatformMutex);
291
292 public:
293 void lock();
294 void unlock();
295 bool try_lock();
296 };
297
298 class PlatformMonitor : public PlatformMutex {
299 #if PLATFORM_MONITOR_IMPL_INDIRECT
300 class Cond : public CHeapObj<mtSynchronizer> {
301 public:
302 pthread_cond_t _cond;
303 Cond* _next;
304
305 Cond();
306 ~Cond();
307 };
308
309 Cond* _impl;
310
311 static Cond* _cond_freelist;
312
313 pthread_cond_t* cond() { return &(_impl->_cond); }
314
315 public:
316 PlatformMonitor(); // Use freelist allocation of impl.
317 ~PlatformMonitor();
318
319 #else
320
321 pthread_cond_t _cond;
322 pthread_cond_t* cond() { return &_cond; }
323
324 public:
325 PlatformMonitor();
326 ~PlatformMonitor();
327
328 #endif // PLATFORM_MONITOR_IMPL_INDIRECT
329
330 private:
331 NONCOPYABLE(PlatformMonitor);
332
333 public:
334 int wait(jlong millis);
335 void notify();
336 void notify_all();
337 };
338
339 #endif // !SOLARIS
340
341 #endif // OS_POSIX_OS_POSIX_HPP