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7a887dd537
GCC 11 -Warray-bounds triggers invalid warnings when building
Linux timer_create.c:
../sysdeps/unix/sysv/linux/timer_create.c: In function '__timer_create_new':
../sysdeps/unix/sysv/linux/timer_create.c:83:17: warning: array subscript 'struct timer[0]' is partly outside array bounds of 'unsigned char[8]' [-Warray-bounds]
83 | newp->sigev_notify = (evp != NULL
| ^~
../sysdeps/unix/sysv/linux/timer_create.c:59:47: note: referencing an object of size 8 allocated by 'malloc'
59 | struct timer *newp = (struct timer *) malloc (offsetof (struct timer,
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
60 | thrfunc));
| ~~~~~~~~~
The struct allocated for !SIGEV_THREAD timers only requires two 'int'
fields (sigev_notify and ktimerid) and the offsetof trick tries minimize
the memory usage by only allocation the required size. However,
although the resulting size is suffice for !SIGEV_THREAD time, accessing
the partially allocated object is error-prone and UB.
This patch fixes both issues by embedding the information whether
the timer if a SIGEV_THREAD in the returned 'timer_t'. For
!SIGEV_THREAD, the resulting 'timer_t' is the returned kernel timer
identifer (kernel_timer_t), while for SIGEV_THREAD it uses the fact
malloc returns at least _Alignof (max_align_t) pointers plus that
valid kernel_timer_t are always positive to set MSB bit of the returned
'timer_t' to indicate the timer handles a SIGEV_THREAD.
It allows to remove the memory allocation for !SIGEV_THREAD and also
remove the 'sigev_notify' field from 'struct timer'.
Checked on x86_64-linux-gnu and i686-linux-gnu.
72 lines
1.9 KiB
C
72 lines
1.9 KiB
C
/* Copyright (C) 2003-2020 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper <drepper@redhat.com>, 2003.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public License as
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published by the Free Software Foundation; either version 2.1 of the
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License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; see the file COPYING.LIB. If
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not, see <https://www.gnu.org/licenses/>. */
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#include <errno.h>
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#include <stdlib.h>
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#include <time.h>
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#include <sysdep.h>
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#include "kernel-posix-timers.h"
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#ifdef timer_delete_alias
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# define timer_delete timer_delete_alias
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#endif
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int
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timer_delete (timer_t timerid)
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{
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#undef timer_delete
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kernel_timer_t ktimerid = timerid_to_kernel_timer (timerid);
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int res = INLINE_SYSCALL_CALL (timer_delete, ktimerid);
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if (res == 0)
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{
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if (timer_is_sigev_thread (timerid))
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{
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struct timer *kt = timerid_to_timer (timerid);
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/* Remove the timer from the list. */
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pthread_mutex_lock (&__active_timer_sigev_thread_lock);
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if (__active_timer_sigev_thread == kt)
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__active_timer_sigev_thread = kt->next;
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else
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{
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struct timer *prevp = __active_timer_sigev_thread;
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while (prevp->next != NULL)
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if (prevp->next == kt)
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{
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prevp->next = kt->next;
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break;
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}
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else
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prevp = prevp->next;
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}
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pthread_mutex_unlock (&__active_timer_sigev_thread_lock);
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free (kt);
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}
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return 0;
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}
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/* The kernel timer is not known or something else bad happened.
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Return the error. */
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return -1;
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}
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