nptl/pthread_getspecific.c

   1 /* Copyright (C) 2002-2024 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 #include <stdlib.h>
  19 #include "pthreadP.h"
  20 #include <shlib-compat.h>
  21
  22 void *
  23 ___pthread_getspecific (pthread_key_t key)
  24 {
  25   struct pthread_key_data *data;
  26
  27   /* Special case access to the first 2nd-level block.  This is the
  28      usual case.  */
  29   if (__glibc_likely (key < PTHREAD_KEY_2NDLEVEL_SIZE))
  30     data = &THREAD_SELF->specific_1stblock[key];
  31   else
  32     {
  33       /* Verify the key is sane.  */
  34       if (key >= PTHREAD_KEYS_MAX)
  35         /* Not valid.  */
  36         return NULL;
  37
  38       unsigned int idx1st = key / PTHREAD_KEY_2NDLEVEL_SIZE;
  39       unsigned int idx2nd = key % PTHREAD_KEY_2NDLEVEL_SIZE;
  40
  41       /* If the sequence number doesn't match or the key cannot be defined
  42          for this thread since the second level array is not allocated
  43          return NULL, too.  */
  44       struct pthread_key_data *level2 = THREAD_GETMEM_NC (THREAD_SELF,
  45                                                           specific, idx1st);
  46       if (level2 == NULL)
  47         /* Not allocated, therefore no data.  */
  48         return NULL;
  49
  50       /* There is data.  */
  51       data = &level2[idx2nd];
  52     }
  53
  54   void *result = data->data;
  55   if (result != NULL)
  56     {
  57       uintptr_t seq = data->seq;
  58
  59       if (__glibc_unlikely (seq != __pthread_keys[key].seq))
  60         result = data->data = NULL;
  61     }
  62
  63   return result;
  64 }
  65 versioned_symbol (libc, ___pthread_getspecific, pthread_getspecific,
  66                   GLIBC_2_34);
  67 libc_hidden_ver (___pthread_getspecific, __pthread_getspecific)
  68 #ifndef SHARED
  69 strong_alias (___pthread_getspecific, __pthread_getspecific)
  70 #endif
  71
  72 #if OTHER_SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_34)
  73 compat_symbol (libpthread, ___pthread_getspecific, __pthread_getspecific,
  74                GLIBC_2_0);
  75 compat_symbol (libpthread, ___pthread_getspecific, pthread_getspecific,
  76                GLIBC_2_0);
  77 #endif