nptl/descr.h

   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 <internal-sigset.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 structure 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   /* List of robust mutexes the thread is holding.  */
 176 #if __PTHREAD_MUTEX_HAVE_PREV
 177   void *robust_prev;
 178   struct robust_list_head robust_head;
 179
 180   /* The list above is strange.  It is basically a double linked list
 181      but the pointer to the next/previous element of the list points
 182      in the middle of the object, the __next element.  Whenever
 183      casting to __pthread_list_t we need to adjust the pointer
 184      first.
 185      These operations are effectively concurrent code in that the thread
 186      can get killed at any point in time and the kernel takes over.  Thus,
 187      the __next elements are a kind of concurrent list and we need to
 188      enforce using compiler barriers that the individual operations happen
 189      in such a way that the kernel always sees a consistent list.  The
 190      backward links (ie, the __prev elements) are not used by the kernel.
 191      FIXME We should use relaxed MO atomic operations here and signal fences
 192      because this kind of concurrency is similar to synchronizing with a
 193      signal handler.  */
 194 # define QUEUE_PTR_ADJUST (offsetof (__pthread_list_t, __next))
 195
 196 # define ENQUEUE_MUTEX_BOTH(mutex, val)                                       \
 197   do {                                                                        \
 198     __pthread_list_t *next = (__pthread_list_t *)                             \
 199       ((((uintptr_t) THREAD_GETMEM (THREAD_SELF, robust_head.list)) & ~1ul)   \
 200        - QUEUE_PTR_ADJUST);                                                   \
 201     next->__prev = (void *) &mutex->__data.__list.__next;                     \
 202     mutex->__data.__list.__next = THREAD_GETMEM (THREAD_SELF,                 \
 203                                                  robust_head.list);           \
 204     mutex->__data.__list.__prev = (void *) &THREAD_SELF->robust_head;         \
 205     /* Ensure that the new list entry is ready before we insert it.  */       \
 206     __asm ("" ::: "memory");                                                  \
 207     THREAD_SETMEM (THREAD_SELF, robust_head.list,                             \
 208                    (void *) (((uintptr_t) &mutex->__data.__list.__next)       \
 209                              | val));                                         \
 210   } while (0)
 211 # define DEQUEUE_MUTEX(mutex) \
 212   do {                                                                        \
 213     __pthread_list_t *next = (__pthread_list_t *)                             \
 214       ((char *) (((uintptr_t) mutex->__data.__list.__next) & ~1ul)            \
 215        - QUEUE_PTR_ADJUST);                                                   \
 216     next->__prev = mutex->__data.__list.__prev;                               \
 217     __pthread_list_t *prev = (__pthread_list_t *)                             \
 218       ((char *) (((uintptr_t) mutex->__data.__list.__prev) & ~1ul)            \
 219        - QUEUE_PTR_ADJUST);                                                   \
 220     prev->__next = mutex->__data.__list.__next;                               \
 221     /* Ensure that we remove the entry from the list before we change the     \
 222        __next pointer of the entry, which is read by the kernel.  */          \
 223     __asm ("" ::: "memory");                                                  \
 224     mutex->__data.__list.__prev = NULL;                                       \
 225     mutex->__data.__list.__next = NULL;                                       \
 226   } while (0)
 227 #else
 228   union
 229   {
 230     __pthread_slist_t robust_list;
 231     struct robust_list_head robust_head;
 232   };
 233
 234 # define ENQUEUE_MUTEX_BOTH(mutex, val)                                       \
 235   do {                                                                        \
 236     mutex->__data.__list.__next                                               \
 237       = THREAD_GETMEM (THREAD_SELF, robust_list.__next);                      \
 238     /* Ensure that the new list entry is ready before we insert it.  */       \
 239     __asm ("" ::: "memory");                                                  \
 240     THREAD_SETMEM (THREAD_SELF, robust_list.__next,                           \
 241                    (void *) (((uintptr_t) &mutex->__data.__list) | val));     \
 242   } while (0)
 243 # define DEQUEUE_MUTEX(mutex) \
 244   do {                                                                        \
 245     __pthread_slist_t *runp = (__pthread_slist_t *)                           \
 246       (((uintptr_t) THREAD_GETMEM (THREAD_SELF, robust_list.__next)) & ~1ul); \
 247     if (runp == &mutex->__data.__list)                                        \
 248       THREAD_SETMEM (THREAD_SELF, robust_list.__next, runp->__next);          \
 249     else                                                                      \
 250       {                                                                       \
 251         __pthread_slist_t *next = (__pthread_slist_t *)               \
 252           (((uintptr_t) runp->__next) & ~1ul);                                \
 253         while (next != &mutex->__data.__list)                                 \
 254           {                                                                   \
 255             runp = next;                                                      \
 256             next = (__pthread_slist_t *) (((uintptr_t) runp->__next) & ~1ul); \
 257           }                                                                   \
 258                                                                               \
 259         runp->__next = next->__next;                                          \
 260         /* Ensure that we remove the entry from the list before we change the \
 261            __next pointer of the entry, which is read by the kernel.  */      \
 262             __asm ("" ::: "memory");                                          \
 263         mutex->__data.__list.__next = NULL;                                   \
 264       }                                                                       \
 265   } while (0)
 266 #endif
 267 #define ENQUEUE_MUTEX(mutex) ENQUEUE_MUTEX_BOTH (mutex, 0)
 268 #define ENQUEUE_MUTEX_PI(mutex) ENQUEUE_MUTEX_BOTH (mutex, 1)
 269
 270   /* List of cleanup buffers.  */
 271   struct _pthread_cleanup_buffer *cleanup;
 272
 273   /* Unwind information.  */
 274   struct pthread_unwind_buf *cleanup_jmp_buf;
 275 #define HAVE_CLEANUP_JMP_BUF
 276
 277   /* Flags determining processing of cancellation.  */
 278   int cancelhandling;
 279   /* Bit set if cancellation is disabled.  */
 280 #define CANCELSTATE_BIT         0
 281 #define CANCELSTATE_BITMASK     (1 << CANCELSTATE_BIT)
 282   /* Bit set if asynchronous cancellation mode is selected.  */
 283 #define CANCELTYPE_BIT          1
 284 #define CANCELTYPE_BITMASK      (1 << CANCELTYPE_BIT)
 285   /* Bit set if canceling has been initiated.  */
 286 #define CANCELING_BIT           2
 287 #define CANCELING_BITMASK       (1 << CANCELING_BIT)
 288   /* Bit set if canceled.  */
 289 #define CANCELED_BIT            3
 290 #define CANCELED_BITMASK        (1 << CANCELED_BIT)
 291   /* Bit set if thread is exiting.  */
 292 #define EXITING_BIT             4
 293 #define EXITING_BITMASK         (1 << EXITING_BIT)
 294   /* Bit set if thread terminated and TCB is freed.  */
 295 #define TERMINATED_BIT          5
 296 #define TERMINATED_BITMASK      (1 << TERMINATED_BIT)
 297   /* Bit set if thread is supposed to change XID.  */
 298 #define SETXID_BIT              6
 299 #define SETXID_BITMASK          (1 << SETXID_BIT)
 300
 301   /* Flags.  Including those copied from the thread attribute.  */
 302   int flags;
 303
 304   /* We allocate one block of references here.  This should be enough
 305      to avoid allocating any memory dynamically for most applications.  */
 306   struct pthread_key_data
 307   {
 308     /* Sequence number.  We use uintptr_t to not require padding on
 309        32- and 64-bit machines.  On 64-bit machines it helps to avoid
 310        wrapping, too.  */
 311     uintptr_t seq;
 312
 313     /* Data pointer.  */
 314     void *data;
 315   } specific_1stblock[PTHREAD_KEY_2NDLEVEL_SIZE];
 316
 317   /* Two-level array for the thread-specific data.  */
 318   struct pthread_key_data *specific[PTHREAD_KEY_1STLEVEL_SIZE];
 319
 320   /* Flag which is set when specific data is set.  */
 321   bool specific_used;
 322
 323   /* True if events must be reported.  */
 324   bool report_events;
 325
 326   /* True if the user provided the stack.  */
 327   bool user_stack;
 328
 329   /* True if thread must stop at startup time.  */
 330   bool stopped_start;
 331
 332   /* Indicate that a thread creation setup has failed (for instance the
 333      scheduler or affinity).  */
 334   int setup_failed;
 335
 336   /* Lock to synchronize access to the descriptor.  */
 337   int lock;
 338
 339   /* Lock for synchronizing setxid calls.  */
 340   unsigned int setxid_futex;
 341
 342   /* If the thread waits to join another one the ID of the latter is
 343      stored here.
 344
 345      In case a thread is detached this field contains a pointer of the
 346      TCB if the thread itself.  This is something which cannot happen
 347      in normal operation.  */
 348   struct pthread *joinid;
 349   /* Check whether a thread is detached.  */
 350 #define IS_DETACHED(pd) ((pd)->joinid == (pd))
 351
 352   /* The result of the thread function.  */
 353   void *result;
 354
 355   /* Scheduling parameters for the new thread.  */
 356   struct sched_param schedparam;
 357   int schedpolicy;
 358
 359   /* Start position of the code to be executed and the argument passed
 360      to the function.  */
 361   void *(*start_routine) (void *);
 362   void *arg;
 363
 364   /* Debug state.  */
 365   td_eventbuf_t eventbuf;
 366   /* Next descriptor with a pending event.  */
 367   struct pthread *nextevent;
 368
 369   /* Machine-specific unwind info.  */
 370   struct _Unwind_Exception exc;
 371
 372   /* If nonzero, pointer to the area allocated for the stack and guard. */
 373   void *stackblock;
 374   /* Size of the stackblock area including the guard.  */
 375   size_t stackblock_size;
 376   /* Size of the included guard area.  */
 377   size_t guardsize;
 378   /* This is what the user specified and what we will report.  */
 379   size_t reported_guardsize;
 380
 381   /* Thread Priority Protection data.  */
 382   struct priority_protection_data *tpp;
 383
 384   /* Resolver state.  */
 385   struct __res_state res;
 386
 387   /* Signal mask for the new thread.  Used during thread startup to
 388      restore the signal mask.  (Threads are launched with all signals
 389      masked.)  */
 390   internal_sigset_t sigmask;
 391
 392   /* Used by the exception handling implementation in the dynamic loader.  */
 393   struct rtld_catch *rtld_catch;
 394
 395   /* Indicates whether is a C11 thread created by thrd_creat.  */
 396   bool c11;
 397
 398   /* Used in __pthread_kill_internal to detected a thread that has
 399      exited or is about to exit.  exit_lock must only be acquired
 400      after blocking signals.  */
 401   bool exiting;
 402   int exit_lock; /* A low-level lock (for use with __libc_lock_init etc).  */
 403
 404   /* Used on strsignal.  */
 405   struct tls_internal_t tls_state;
 406
 407   /* rseq area registered with the kernel.  Use a custom definition
 408      here to isolate from kernel struct rseq changes.  The
 409      implementation of sched_getcpu needs acccess to the cpu_id field;
 410      the other fields are unused and not included here.  */
 411   union
 412   {
 413     struct
 414     {
 415       uint32_t cpu_id_start;
 416       uint32_t cpu_id;
 417     };
 418     char pad[32];               /* Original rseq area size.  */
 419   } rseq_area __attribute__ ((aligned (32)));
 420
 421   /* Amount of end padding, if any, in this structure.
 422      This definition relies on rseq_area being last.  */
 423 #define PTHREAD_STRUCT_END_PADDING \
 424   (sizeof (struct pthread) - offsetof (struct pthread, rseq_area) \
 425    + sizeof ((struct pthread) {}.rseq_area))
 426 } __attribute ((aligned (TCB_ALIGNMENT)));
 427
 428 static inline bool
 429 cancel_enabled_and_canceled (int value)
 430 {
 431   return (value & (CANCELSTATE_BITMASK | CANCELED_BITMASK | EXITING_BITMASK
 432                    | TERMINATED_BITMASK))
 433     == CANCELED_BITMASK;
 434 }
 435
 436 static inline bool
 437 cancel_enabled_and_canceled_and_async (int value)
 438 {
 439   return ((value) & (CANCELSTATE_BITMASK | CANCELTYPE_BITMASK | CANCELED_BITMASK
 440                      | EXITING_BITMASK | TERMINATED_BITMASK))
 441     == (CANCELTYPE_BITMASK | CANCELED_BITMASK);
 442 }
 443
 444 /* This yields the pointer that TLS support code calls the thread pointer.  */
 445 #if TLS_TCB_AT_TP
 446 # define TLS_TPADJ(pd) (pd)
 447 #elif TLS_DTV_AT_TP
 448 # define TLS_TPADJ(pd) ((struct pthread *)((char *) (pd) + TLS_PRE_TCB_SIZE))
 449 #endif
 450
 451 #endif  /* descr.h */