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 <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.  */
  66 struct 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.  */
  98 struct 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.  */
 114 struct robust_list_head
 115 {
 116   void *list;
 117   long int futex_offset;
 118   void *list_op_pending;
 119 };
 120
 121
 122 /* Data structure used to handle thread priority protection.  */
 123 struct priority_protection_data
 124 {
 125   int priomax;
 126   unsigned int priomap[];
 127 };
 128
 129
 130 /* Thread descriptor data structure.  */
 131 struct 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
 418 static inline bool
 419 cancel_enabled_and_canceled (int value)
 420 {
 421   return (value & (CANCELSTATE_BITMASK | CANCELED_BITMASK | EXITING_BITMASK
 422                    | TERMINATED_BITMASK))
 423     == CANCELED_BITMASK;
 424 }
 425
 426 static inline bool
 427 cancel_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 */