nptl/descr.h

   1 /* Copyright (C) 2002-2022 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
  39 #ifndef TCB_ALIGNMENT
  40 # define TCB_ALIGNMENT 32
  41 #elif TCB_ALIGNMENT < 32
  42 # error TCB_ALIGNMENT must be at least 32
  43 #endif
  44
  45
  46 /* We keep thread specific data in a special data structure, a two-level
  47    array.  The top-level array contains pointers to dynamically allocated
  48    arrays of a certain number of data pointers.  So we can implement a
  49    sparse array.  Each dynamic second-level array has
  50         PTHREAD_KEY_2NDLEVEL_SIZE
  51    entries.  This value shouldn't be too large.  */
  52 #define PTHREAD_KEY_2NDLEVEL_SIZE       32
  53
  54 /* We need to address PTHREAD_KEYS_MAX key with PTHREAD_KEY_2NDLEVEL_SIZE
  55    keys in each subarray.  */
  56 #define PTHREAD_KEY_1STLEVEL_SIZE \
  57   ((PTHREAD_KEYS_MAX + PTHREAD_KEY_2NDLEVEL_SIZE - 1) \
  58    / PTHREAD_KEY_2NDLEVEL_SIZE)
  59
  60
  61
  62
  63 /* Internal version of the buffer to store cancellation handler
  64    information.  */
  65 struct pthread_unwind_buf
  66 {
  67   struct
  68   {
  69     __jmp_buf jmp_buf;
  70     int mask_was_saved;
  71   } cancel_jmp_buf[1];
  72
  73   union
  74   {
  75     /* This is the placeholder of the public version.  */
  76     void *pad[4];
  77
  78     struct
  79     {
  80       /* Pointer to the previous cleanup buffer.  */
  81       struct pthread_unwind_buf *prev;
  82
  83       /* Backward compatibility: state of the old-style cleanup
  84          handler at the time of the previous new-style cleanup handler
  85          installment.  */
  86       struct _pthread_cleanup_buffer *cleanup;
  87
  88       /* Cancellation type before the push call.  */
  89       int canceltype;
  90     } data;
  91   } priv;
  92 };
  93
  94
  95 /* Opcodes and data types for communication with the signal handler to
  96    change user/group IDs.  */
  97 struct xid_command
  98 {
  99   int syscall_no;
 100   /* Enforce zero-extension for the pointer argument in
 101
 102      int setgroups (size_t size, const gid_t *list);
 103
 104      The kernel XID arguments are unsigned and do not require sign
 105      extension.  */
 106   unsigned long int id[3];
 107   volatile int cntr;
 108   volatile int error; /* -1: no call yet, 0: success seen, >0: error seen.  */
 109 };
 110
 111
 112 /* Data structure used by the kernel to find robust futexes.  */
 113 struct robust_list_head
 114 {
 115   void *list;
 116   long int futex_offset;
 117   void *list_op_pending;
 118 };
 119
 120
 121 /* Data strcture used to handle thread priority protection.  */
 122 struct priority_protection_data
 123 {
 124   int priomax;
 125   unsigned int priomap[];
 126 };
 127
 128
 129 /* Thread descriptor data structure.  */
 130 struct pthread
 131 {
 132   union
 133   {
 134 #if !TLS_DTV_AT_TP
 135     /* This overlaps the TCB as used for TLS without threads (see tls.h).  */
 136     tcbhead_t header;
 137 #else
 138     struct
 139     {
 140       /* multiple_threads is enabled either when the process has spawned at
 141          least one thread or when a single-threaded process cancels itself.
 142          This enables additional code to introduce locking before doing some
 143          compare_and_exchange operations and also enable cancellation points.
 144          The concepts of multiple threads and cancellation points ideally
 145          should be separate, since it is not necessary for multiple threads to
 146          have been created for cancellation points to be enabled, as is the
 147          case is when single-threaded process cancels itself.
 148
 149          Since enabling multiple_threads enables additional code in
 150          cancellation points and compare_and_exchange operations, there is a
 151          potential for an unneeded performance hit when it is enabled in a
 152          single-threaded, self-canceling process.  This is OK though, since a
 153          single-threaded process will enable async cancellation only when it
 154          looks to cancel itself and is hence going to end anyway.  */
 155       int multiple_threads;
 156       int gscope_flag;
 157     } header;
 158 #endif
 159
 160     /* This extra padding has no special purpose, and this structure layout
 161        is private and subject to change without affecting the official ABI.
 162        We just have it here in case it might be convenient for some
 163        implementation-specific instrumentation hack or suchlike.  */
 164     void *__padding[24];
 165   };
 166
 167   /* This descriptor's link on the GL (dl_stack_used) or
 168      GL (dl_stack_user) list.  */
 169   list_t list;
 170
 171   /* Thread ID - which is also a 'is this thread descriptor (and
 172      therefore stack) used' flag.  */
 173   pid_t tid;
 174
 175   /* Ununsed.  */
 176   pid_t pid_ununsed;
 177
 178   /* List of robust mutexes the thread is holding.  */
 179 #if __PTHREAD_MUTEX_HAVE_PREV
 180   void *robust_prev;
 181   struct robust_list_head robust_head;
 182
 183   /* The list above is strange.  It is basically a double linked list
 184      but the pointer to the next/previous element of the list points
 185      in the middle of the object, the __next element.  Whenever
 186      casting to __pthread_list_t we need to adjust the pointer
 187      first.
 188      These operations are effectively concurrent code in that the thread
 189      can get killed at any point in time and the kernel takes over.  Thus,
 190      the __next elements are a kind of concurrent list and we need to
 191      enforce using compiler barriers that the individual operations happen
 192      in such a way that the kernel always sees a consistent list.  The
 193      backward links (ie, the __prev elements) are not used by the kernel.
 194      FIXME We should use relaxed MO atomic operations here and signal fences
 195      because this kind of concurrency is similar to synchronizing with a
 196      signal handler.  */
 197 # define QUEUE_PTR_ADJUST (offsetof (__pthread_list_t, __next))
 198
 199 # define ENQUEUE_MUTEX_BOTH(mutex, val)                                       \
 200   do {                                                                        \
 201     __pthread_list_t *next = (__pthread_list_t *)                             \
 202       ((((uintptr_t) THREAD_GETMEM (THREAD_SELF, robust_head.list)) & ~1ul)   \
 203        - QUEUE_PTR_ADJUST);                                                   \
 204     next->__prev = (void *) &mutex->__data.__list.__next;                     \
 205     mutex->__data.__list.__next = THREAD_GETMEM (THREAD_SELF,                 \
 206                                                  robust_head.list);           \
 207     mutex->__data.__list.__prev = (void *) &THREAD_SELF->robust_head;         \
 208     /* Ensure that the new list entry is ready before we insert it.  */       \
 209     __asm ("" ::: "memory");                                                  \
 210     THREAD_SETMEM (THREAD_SELF, robust_head.list,                             \
 211                    (void *) (((uintptr_t) &mutex->__data.__list.__next)       \
 212                              | val));                                         \
 213   } while (0)
 214 # define DEQUEUE_MUTEX(mutex) \
 215   do {                                                                        \
 216     __pthread_list_t *next = (__pthread_list_t *)                             \
 217       ((char *) (((uintptr_t) mutex->__data.__list.__next) & ~1ul)            \
 218        - QUEUE_PTR_ADJUST);                                                   \
 219     next->__prev = mutex->__data.__list.__prev;                               \
 220     __pthread_list_t *prev = (__pthread_list_t *)                             \
 221       ((char *) (((uintptr_t) mutex->__data.__list.__prev) & ~1ul)            \
 222        - QUEUE_PTR_ADJUST);                                                   \
 223     prev->__next = mutex->__data.__list.__next;                               \
 224     /* Ensure that we remove the entry from the list before we change the     \
 225        __next pointer of the entry, which is read by the kernel.  */          \
 226     __asm ("" ::: "memory");                                                  \
 227     mutex->__data.__list.__prev = NULL;                                       \
 228     mutex->__data.__list.__next = NULL;                                       \
 229   } while (0)
 230 #else
 231   union
 232   {
 233     __pthread_slist_t robust_list;
 234     struct robust_list_head robust_head;
 235   };
 236
 237 # define ENQUEUE_MUTEX_BOTH(mutex, val)                                       \
 238   do {                                                                        \
 239     mutex->__data.__list.__next                                               \
 240       = THREAD_GETMEM (THREAD_SELF, robust_list.__next);                      \
 241     /* Ensure that the new list entry is ready before we insert it.  */       \
 242     __asm ("" ::: "memory");                                                  \
 243     THREAD_SETMEM (THREAD_SELF, robust_list.__next,                           \
 244                    (void *) (((uintptr_t) &mutex->__data.__list) | val));     \
 245   } while (0)
 246 # define DEQUEUE_MUTEX(mutex) \
 247   do {                                                                        \
 248     __pthread_slist_t *runp = (__pthread_slist_t *)                           \
 249       (((uintptr_t) THREAD_GETMEM (THREAD_SELF, robust_list.__next)) & ~1ul); \
 250     if (runp == &mutex->__data.__list)                                        \
 251       THREAD_SETMEM (THREAD_SELF, robust_list.__next, runp->__next);          \
 252     else                                                                      \
 253       {                                                                       \
 254         __pthread_slist_t *next = (__pthread_slist_t *)               \
 255           (((uintptr_t) runp->__next) & ~1ul);                                \
 256         while (next != &mutex->__data.__list)                                 \
 257           {                                                                   \
 258             runp = next;                                                      \
 259             next = (__pthread_slist_t *) (((uintptr_t) runp->__next) & ~1ul); \
 260           }                                                                   \
 261                                                                               \
 262         runp->__next = next->__next;                                          \
 263         /* Ensure that we remove the entry from the list before we change the \
 264            __next pointer of the entry, which is read by the kernel.  */      \
 265             __asm ("" ::: "memory");                                          \
 266         mutex->__data.__list.__next = NULL;                                   \
 267       }                                                                       \
 268   } while (0)
 269 #endif
 270 #define ENQUEUE_MUTEX(mutex) ENQUEUE_MUTEX_BOTH (mutex, 0)
 271 #define ENQUEUE_MUTEX_PI(mutex) ENQUEUE_MUTEX_BOTH (mutex, 1)
 272
 273   /* List of cleanup buffers.  */
 274   struct _pthread_cleanup_buffer *cleanup;
 275
 276   /* Unwind information.  */
 277   struct pthread_unwind_buf *cleanup_jmp_buf;
 278 #define HAVE_CLEANUP_JMP_BUF
 279
 280   /* Flags determining processing of cancellation.  */
 281   int cancelhandling;
 282   /* Bit set if cancellation is disabled.  */
 283 #define CANCELSTATE_BIT         0
 284 #define CANCELSTATE_BITMASK     (1 << CANCELSTATE_BIT)
 285   /* Bit set if asynchronous cancellation mode is selected.  */
 286 #define CANCELTYPE_BIT          1
 287 #define CANCELTYPE_BITMASK      (1 << CANCELTYPE_BIT)
 288   /* Bit set if canceling has been initiated.  */
 289 #define CANCELING_BIT           2
 290 #define CANCELING_BITMASK       (1 << CANCELING_BIT)
 291   /* Bit set if canceled.  */
 292 #define CANCELED_BIT            3
 293 #define CANCELED_BITMASK        (1 << CANCELED_BIT)
 294   /* Bit set if thread is exiting.  */
 295 #define EXITING_BIT             4
 296 #define EXITING_BITMASK         (1 << EXITING_BIT)
 297   /* Bit set if thread terminated and TCB is freed.  */
 298 #define TERMINATED_BIT          5
 299 #define TERMINATED_BITMASK      (1 << TERMINATED_BIT)
 300   /* Bit set if thread is supposed to change XID.  */
 301 #define SETXID_BIT              6
 302 #define SETXID_BITMASK          (1 << SETXID_BIT)
 303
 304   /* Flags.  Including those copied from the thread attribute.  */
 305   int flags;
 306
 307   /* We allocate one block of references here.  This should be enough
 308      to avoid allocating any memory dynamically for most applications.  */
 309   struct pthread_key_data
 310   {
 311     /* Sequence number.  We use uintptr_t to not require padding on
 312        32- and 64-bit machines.  On 64-bit machines it helps to avoid
 313        wrapping, too.  */
 314     uintptr_t seq;
 315
 316     /* Data pointer.  */
 317     void *data;
 318   } specific_1stblock[PTHREAD_KEY_2NDLEVEL_SIZE];
 319
 320   /* Two-level array for the thread-specific data.  */
 321   struct pthread_key_data *specific[PTHREAD_KEY_1STLEVEL_SIZE];
 322
 323   /* Flag which is set when specific data is set.  */
 324   bool specific_used;
 325
 326   /* True if events must be reported.  */
 327   bool report_events;
 328
 329   /* True if the user provided the stack.  */
 330   bool user_stack;
 331
 332   /* True if thread must stop at startup time.  */
 333   bool stopped_start;
 334
 335   /* Indicate that a thread creation setup has failed (for instance the
 336      scheduler or affinity).  */
 337   int setup_failed;
 338
 339   /* Lock to synchronize access to the descriptor.  */
 340   int lock;
 341
 342   /* Lock for synchronizing setxid calls.  */
 343   unsigned int setxid_futex;
 344
 345 #if HP_TIMING_INLINE
 346   hp_timing_t cpuclock_offset_ununsed;
 347 #endif
 348
 349   /* If the thread waits to join another one the ID of the latter is
 350      stored here.
 351
 352      In case a thread is detached this field contains a pointer of the
 353      TCB if the thread itself.  This is something which cannot happen
 354      in normal operation.  */
 355   struct pthread *joinid;
 356   /* Check whether a thread is detached.  */
 357 #define IS_DETACHED(pd) ((pd)->joinid == (pd))
 358
 359   /* The result of the thread function.  */
 360   void *result;
 361
 362   /* Scheduling parameters for the new thread.  */
 363   struct sched_param schedparam;
 364   int schedpolicy;
 365
 366   /* Start position of the code to be executed and the argument passed
 367      to the function.  */
 368   void *(*start_routine) (void *);
 369   void *arg;
 370
 371   /* Debug state.  */
 372   td_eventbuf_t eventbuf;
 373   /* Next descriptor with a pending event.  */
 374   struct pthread *nextevent;
 375
 376   /* Machine-specific unwind info.  */
 377   struct _Unwind_Exception exc;
 378
 379   /* If nonzero, pointer to the area allocated for the stack and guard. */
 380   void *stackblock;
 381   /* Size of the stackblock area including the guard.  */
 382   size_t stackblock_size;
 383   /* Size of the included guard area.  */
 384   size_t guardsize;
 385   /* This is what the user specified and what we will report.  */
 386   size_t reported_guardsize;
 387
 388   /* Thread Priority Protection data.  */
 389   struct priority_protection_data *tpp;
 390
 391   /* Resolver state.  */
 392   struct __res_state res;
 393
 394   /* Signal mask for the new thread.  Used during thread startup to
 395      restore the signal mask.  (Threads are launched with all signals
 396      masked.)  */
 397   sigset_t sigmask;
 398
 399   /* Indicates whether is a C11 thread created by thrd_creat.  */
 400   bool c11;
 401
 402   /* Used in __pthread_kill_internal to detected a thread that has
 403      exited or is about to exit.  exit_lock must only be acquired
 404      after blocking signals.  */
 405   bool exiting;
 406   int exit_lock; /* A low-level lock (for use with __libc_lock_init etc).  */
 407
 408   /* Used on strsignal.  */
 409   struct tls_internal_t tls_state;
 410
 411   /* rseq area registered with the kernel.  */
 412   struct rseq rseq_area;
 413
 414   /* This member must be last.  */
 415   char end_padding[];
 416
 417 #define PTHREAD_STRUCT_END_PADDING \
 418   (sizeof (struct pthread) - offsetof (struct pthread, end_padding))
 419 } __attribute ((aligned (TCB_ALIGNMENT)));
 420
 421 static inline bool
 422 cancel_enabled_and_canceled (int value)
 423 {
 424   return (value & (CANCELSTATE_BITMASK | CANCELED_BITMASK | EXITING_BITMASK
 425                    | TERMINATED_BITMASK))
 426     == CANCELED_BITMASK;
 427 }
 428
 429 static inline bool
 430 cancel_enabled_and_canceled_and_async (int value)
 431 {
 432   return ((value) & (CANCELSTATE_BITMASK | CANCELTYPE_BITMASK | CANCELED_BITMASK
 433                      | EXITING_BITMASK | TERMINATED_BITMASK))
 434     == (CANCELTYPE_BITMASK | CANCELED_BITMASK);
 435 }
 436
 437 /* This yields the pointer that TLS support code calls the thread pointer.  */
 438 #if TLS_TCB_AT_TP
 439 # define TLS_TPADJ(pd) (pd)
 440 #elif TLS_DTV_AT_TP
 441 # define TLS_TPADJ(pd) ((struct pthread *)((char *) (pd) + TLS_PRE_TCB_SIZE))
 442 #endif
 443
 444 #endif  /* descr.h */