1/* Copyright (C) 2002-2023 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <https://www.gnu.org/licenses/>. */
17
18#ifndef _DESCR_H
19#define _DESCR_H 1
20
21#include <limits.h>
22#include <sched.h>
23#include <setjmp.h>
24#include <stdbool.h>
25#include <sys/types.h>
26#include <hp-timing.h>
27#include <list_t.h>
28#include <lowlevellock.h>
29#include <pthreaddef.h>
30#include <dl-sysdep.h>
31#include <thread_db.h>
32#include <tls.h>
33#include <unwind.h>
34#include <bits/types/res_state.h>
35#include <kernel-features.h>
36#include <tls-internal-struct.h>
37#include <sys/rseq.h>
38#include <internal-sigset.h>
39
40#ifndef TCB_ALIGNMENT
41# define TCB_ALIGNMENT 32
42#elif TCB_ALIGNMENT < 32
43# error TCB_ALIGNMENT must be at least 32
44#endif
45
46
47/* We keep thread specific data in a special data structure, a two-level
48 array. The top-level array contains pointers to dynamically allocated
49 arrays of a certain number of data pointers. So we can implement a
50 sparse array. Each dynamic second-level array has
51 PTHREAD_KEY_2NDLEVEL_SIZE
52 entries. This value shouldn't be too large. */
53#define PTHREAD_KEY_2NDLEVEL_SIZE 32
54
55/* We need to address PTHREAD_KEYS_MAX key with PTHREAD_KEY_2NDLEVEL_SIZE
56 keys in each subarray. */
57#define PTHREAD_KEY_1STLEVEL_SIZE \
58 ((PTHREAD_KEYS_MAX + PTHREAD_KEY_2NDLEVEL_SIZE - 1) \
59 / PTHREAD_KEY_2NDLEVEL_SIZE)
60
61
62
63
64/* Internal version of the buffer to store cancellation handler
65 information. */
66struct pthread_unwind_buf
67{
68 struct
69 {
70 __jmp_buf jmp_buf;
71 int mask_was_saved;
72 } cancel_jmp_buf[1];
73
74 union
75 {
76 /* This is the placeholder of the public version. */
77 void *pad[4];
78
79 struct
80 {
81 /* Pointer to the previous cleanup buffer. */
82 struct pthread_unwind_buf *prev;
83
84 /* Backward compatibility: state of the old-style cleanup
85 handler at the time of the previous new-style cleanup handler
86 installment. */
87 struct _pthread_cleanup_buffer *cleanup;
88
89 /* Cancellation type before the push call. */
90 int canceltype;
91 } data;
92 } priv;
93};
94
95
96/* Opcodes and data types for communication with the signal handler to
97 change user/group IDs. */
98struct xid_command
99{
100 int syscall_no;
101 /* Enforce zero-extension for the pointer argument in
102
103 int setgroups (size_t size, const gid_t *list);
104
105 The kernel XID arguments are unsigned and do not require sign
106 extension. */
107 unsigned long int id[3];
108 volatile int cntr;
109 volatile int error; /* -1: no call yet, 0: success seen, >0: error seen. */
110};
111
112
113/* Data structure used by the kernel to find robust futexes. */
114struct robust_list_head
115{
116 void *list;
117 long int futex_offset;
118 void *list_op_pending;
119};
120
121
122/* Data strcture used to handle thread priority protection. */
123struct priority_protection_data
124{
125 int priomax;
126 unsigned int priomap[];
127};
128
129
130/* Thread descriptor data structure. */
131struct pthread
132{
133 union
134 {
135#if !TLS_DTV_AT_TP
136 /* This overlaps the TCB as used for TLS without threads (see tls.h). */
137 tcbhead_t header;
138#else
139 struct
140 {
141 /* multiple_threads is enabled either when the process has spawned at
142 least one thread or when a single-threaded process cancels itself.
143 This enables additional code to introduce locking before doing some
144 compare_and_exchange operations and also enable cancellation points.
145 The concepts of multiple threads and cancellation points ideally
146 should be separate, since it is not necessary for multiple threads to
147 have been created for cancellation points to be enabled, as is the
148 case is when single-threaded process cancels itself.
149
150 Since enabling multiple_threads enables additional code in
151 cancellation points and compare_and_exchange operations, there is a
152 potential for an unneeded performance hit when it is enabled in a
153 single-threaded, self-canceling process. This is OK though, since a
154 single-threaded process will enable async cancellation only when it
155 looks to cancel itself and is hence going to end anyway. */
156 int multiple_threads;
157 int gscope_flag;
158 } header;
159#endif
160
161 /* This extra padding has no special purpose, and this structure layout
162 is private and subject to change without affecting the official ABI.
163 We just have it here in case it might be convenient for some
164 implementation-specific instrumentation hack or suchlike. */
165 void *__padding[24];
166 };
167
168 /* This descriptor's link on the GL (dl_stack_used) or
169 GL (dl_stack_user) list. */
170 list_t list;
171
172 /* Thread ID - which is also a 'is this thread descriptor (and
173 therefore stack) used' flag. */
174 pid_t tid;
175
176 /* List of robust mutexes the thread is holding. */
177#if __PTHREAD_MUTEX_HAVE_PREV
178 void *robust_prev;
179 struct robust_list_head robust_head;
180
181 /* The list above is strange. It is basically a double linked list
182 but the pointer to the next/previous element of the list points
183 in the middle of the object, the __next element. Whenever
184 casting to __pthread_list_t we need to adjust the pointer
185 first.
186 These operations are effectively concurrent code in that the thread
187 can get killed at any point in time and the kernel takes over. Thus,
188 the __next elements are a kind of concurrent list and we need to
189 enforce using compiler barriers that the individual operations happen
190 in such a way that the kernel always sees a consistent list. The
191 backward links (ie, the __prev elements) are not used by the kernel.
192 FIXME We should use relaxed MO atomic operations here and signal fences
193 because this kind of concurrency is similar to synchronizing with a
194 signal handler. */
195# define QUEUE_PTR_ADJUST (offsetof (__pthread_list_t, __next))
196
197# define ENQUEUE_MUTEX_BOTH(mutex, val) \
198 do { \
199 __pthread_list_t *next = (__pthread_list_t *) \
200 ((((uintptr_t) THREAD_GETMEM (THREAD_SELF, robust_head.list)) & ~1ul) \
201 - QUEUE_PTR_ADJUST); \
202 next->__prev = (void *) &mutex->__data.__list.__next; \
203 mutex->__data.__list.__next = THREAD_GETMEM (THREAD_SELF, \
204 robust_head.list); \
205 mutex->__data.__list.__prev = (void *) &THREAD_SELF->robust_head; \
206 /* Ensure that the new list entry is ready before we insert it. */ \
207 __asm ("" ::: "memory"); \
208 THREAD_SETMEM (THREAD_SELF, robust_head.list, \
209 (void *) (((uintptr_t) &mutex->__data.__list.__next) \
210 | val)); \
211 } while (0)
212# define DEQUEUE_MUTEX(mutex) \
213 do { \
214 __pthread_list_t *next = (__pthread_list_t *) \
215 ((char *) (((uintptr_t) mutex->__data.__list.__next) & ~1ul) \
216 - QUEUE_PTR_ADJUST); \
217 next->__prev = mutex->__data.__list.__prev; \
218 __pthread_list_t *prev = (__pthread_list_t *) \
219 ((char *) (((uintptr_t) mutex->__data.__list.__prev) & ~1ul) \
220 - QUEUE_PTR_ADJUST); \
221 prev->__next = mutex->__data.__list.__next; \
222 /* Ensure that we remove the entry from the list before we change the \
223 __next pointer of the entry, which is read by the kernel. */ \
224 __asm ("" ::: "memory"); \
225 mutex->__data.__list.__prev = NULL; \
226 mutex->__data.__list.__next = NULL; \
227 } while (0)
228#else
229 union
230 {
231 __pthread_slist_t robust_list;
232 struct robust_list_head robust_head;
233 };
234
235# define ENQUEUE_MUTEX_BOTH(mutex, val) \
236 do { \
237 mutex->__data.__list.__next \
238 = THREAD_GETMEM (THREAD_SELF, robust_list.__next); \
239 /* Ensure that the new list entry is ready before we insert it. */ \
240 __asm ("" ::: "memory"); \
241 THREAD_SETMEM (THREAD_SELF, robust_list.__next, \
242 (void *) (((uintptr_t) &mutex->__data.__list) | val)); \
243 } while (0)
244# define DEQUEUE_MUTEX(mutex) \
245 do { \
246 __pthread_slist_t *runp = (__pthread_slist_t *) \
247 (((uintptr_t) THREAD_GETMEM (THREAD_SELF, robust_list.__next)) & ~1ul); \
248 if (runp == &mutex->__data.__list) \
249 THREAD_SETMEM (THREAD_SELF, robust_list.__next, runp->__next); \
250 else \
251 { \
252 __pthread_slist_t *next = (__pthread_slist_t *) \
253 (((uintptr_t) runp->__next) & ~1ul); \
254 while (next != &mutex->__data.__list) \
255 { \
256 runp = next; \
257 next = (__pthread_slist_t *) (((uintptr_t) runp->__next) & ~1ul); \
258 } \
259 \
260 runp->__next = next->__next; \
261 /* Ensure that we remove the entry from the list before we change the \
262 __next pointer of the entry, which is read by the kernel. */ \
263 __asm ("" ::: "memory"); \
264 mutex->__data.__list.__next = NULL; \
265 } \
266 } while (0)
267#endif
268#define ENQUEUE_MUTEX(mutex) ENQUEUE_MUTEX_BOTH (mutex, 0)
269#define ENQUEUE_MUTEX_PI(mutex) ENQUEUE_MUTEX_BOTH (mutex, 1)
270
271 /* List of cleanup buffers. */
272 struct _pthread_cleanup_buffer *cleanup;
273
274 /* Unwind information. */
275 struct pthread_unwind_buf *cleanup_jmp_buf;
276#define HAVE_CLEANUP_JMP_BUF
277
278 /* Flags determining processing of cancellation. */
279 int cancelhandling;
280 /* Bit set if cancellation is disabled. */
281#define CANCELSTATE_BIT 0
282#define CANCELSTATE_BITMASK (1 << CANCELSTATE_BIT)
283 /* Bit set if asynchronous cancellation mode is selected. */
284#define CANCELTYPE_BIT 1
285#define CANCELTYPE_BITMASK (1 << CANCELTYPE_BIT)
286 /* Bit set if canceling has been initiated. */
287#define CANCELING_BIT 2
288#define CANCELING_BITMASK (1 << CANCELING_BIT)
289 /* Bit set if canceled. */
290#define CANCELED_BIT 3
291#define CANCELED_BITMASK (1 << CANCELED_BIT)
292 /* Bit set if thread is exiting. */
293#define EXITING_BIT 4
294#define EXITING_BITMASK (1 << EXITING_BIT)
295 /* Bit set if thread terminated and TCB is freed. */
296#define TERMINATED_BIT 5
297#define TERMINATED_BITMASK (1 << TERMINATED_BIT)
298 /* Bit set if thread is supposed to change XID. */
299#define SETXID_BIT 6
300#define SETXID_BITMASK (1 << SETXID_BIT)
301
302 /* Flags. Including those copied from the thread attribute. */
303 int flags;
304
305 /* We allocate one block of references here. This should be enough
306 to avoid allocating any memory dynamically for most applications. */
307 struct pthread_key_data
308 {
309 /* Sequence number. We use uintptr_t to not require padding on
310 32- and 64-bit machines. On 64-bit machines it helps to avoid
311 wrapping, too. */
312 uintptr_t seq;
313
314 /* Data pointer. */
315 void *data;
316 } specific_1stblock[PTHREAD_KEY_2NDLEVEL_SIZE];
317
318 /* Two-level array for the thread-specific data. */
319 struct pthread_key_data *specific[PTHREAD_KEY_1STLEVEL_SIZE];
320
321 /* Flag which is set when specific data is set. */
322 bool specific_used;
323
324 /* True if events must be reported. */
325 bool report_events;
326
327 /* True if the user provided the stack. */
328 bool user_stack;
329
330 /* True if thread must stop at startup time. */
331 bool stopped_start;
332
333 /* Indicate that a thread creation setup has failed (for instance the
334 scheduler or affinity). */
335 int setup_failed;
336
337 /* Lock to synchronize access to the descriptor. */
338 int lock;
339
340 /* Lock for synchronizing setxid calls. */
341 unsigned int setxid_futex;
342
343 /* If the thread waits to join another one the ID of the latter is
344 stored here.
345
346 In case a thread is detached this field contains a pointer of the
347 TCB if the thread itself. This is something which cannot happen
348 in normal operation. */
349 struct pthread *joinid;
350 /* Check whether a thread is detached. */
351#define IS_DETACHED(pd) ((pd)->joinid == (pd))
352
353 /* The result of the thread function. */
354 void *result;
355
356 /* Scheduling parameters for the new thread. */
357 struct sched_param schedparam;
358 int schedpolicy;
359
360 /* Start position of the code to be executed and the argument passed
361 to the function. */
362 void *(*start_routine) (void *);
363 void *arg;
364
365 /* Debug state. */
366 td_eventbuf_t eventbuf;
367 /* Next descriptor with a pending event. */
368 struct pthread *nextevent;
369
370 /* Machine-specific unwind info. */
371 struct _Unwind_Exception exc;
372
373 /* If nonzero, pointer to the area allocated for the stack and guard. */
374 void *stackblock;
375 /* Size of the stackblock area including the guard. */
376 size_t stackblock_size;
377 /* Size of the included guard area. */
378 size_t guardsize;
379 /* This is what the user specified and what we will report. */
380 size_t reported_guardsize;
381
382 /* Thread Priority Protection data. */
383 struct priority_protection_data *tpp;
384
385 /* Resolver state. */
386 struct __res_state res;
387
388 /* Signal mask for the new thread. Used during thread startup to
389 restore the signal mask. (Threads are launched with all signals
390 masked.) */
391 internal_sigset_t sigmask;
392
393 /* Used by the exception handling implementation in the dynamic loader. */
394 struct rtld_catch *rtld_catch;
395
396 /* Indicates whether is a C11 thread created by thrd_creat. */
397 bool c11;
398
399 /* Used in __pthread_kill_internal to detected a thread that has
400 exited or is about to exit. exit_lock must only be acquired
401 after blocking signals. */
402 bool exiting;
403 int exit_lock; /* A low-level lock (for use with __libc_lock_init etc). */
404
405 /* Used on strsignal. */
406 struct tls_internal_t tls_state;
407
408 /* rseq area registered with the kernel. */
409 struct rseq rseq_area;
410
411 /* This member must be last. */
412 char end_padding[];
413
414#define PTHREAD_STRUCT_END_PADDING \
415 (sizeof (struct pthread) - offsetof (struct pthread, end_padding))
416} __attribute ((aligned (TCB_ALIGNMENT)));
417
418static inline bool
419cancel_enabled_and_canceled (int value)
420{
421 return (value & (CANCELSTATE_BITMASK | CANCELED_BITMASK | EXITING_BITMASK
422 | TERMINATED_BITMASK))
423 == CANCELED_BITMASK;
424}
425
426static inline bool
427cancel_enabled_and_canceled_and_async (int value)
428{
429 return ((value) & (CANCELSTATE_BITMASK | CANCELTYPE_BITMASK | CANCELED_BITMASK
430 | EXITING_BITMASK | TERMINATED_BITMASK))
431 == (CANCELTYPE_BITMASK | CANCELED_BITMASK);
432}
433
434/* This yields the pointer that TLS support code calls the thread pointer. */
435#if TLS_TCB_AT_TP
436# define TLS_TPADJ(pd) (pd)
437#elif TLS_DTV_AT_TP
438# define TLS_TPADJ(pd) ((struct pthread *)((char *) (pd) + TLS_PRE_TCB_SIZE))
439#endif
440
441#endif /* descr.h */
442