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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.
68 lines
2.1 KiB
C
68 lines
2.1 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-features.h>
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#include "kernel-posix-timers.h"
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int
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__timer_gettime64 (timer_t timerid, struct __itimerspec64 *value)
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{
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kernel_timer_t ktimerid = timerid_to_kernel_timer (timerid);
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#ifndef __NR_timer_gettime64
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# define __NR_timer_gettime64 __NR_timer_gettime
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#endif
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int ret = INLINE_SYSCALL_CALL (timer_gettime64, ktimerid, value);
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#ifndef __ASSUME_TIME64_SYSCALLS
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if (ret == 0 || errno != ENOSYS)
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return ret;
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struct itimerspec its32;
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ret = INLINE_SYSCALL_CALL (timer_gettime, ktimerid, &its32);
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if (ret == 0)
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{
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value->it_interval = valid_timespec_to_timespec64 (its32.it_interval);
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value->it_value = valid_timespec_to_timespec64 (its32.it_value);
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}
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#endif
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return ret;
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}
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#if __TIMESIZE != 64
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librt_hidden_def (__timer_gettime64)
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int
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__timer_gettime (timer_t timerid, struct itimerspec *value)
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{
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struct __itimerspec64 its64;
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int retval = __timer_gettime64 (timerid, &its64);
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if (retval == 0)
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{
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value->it_interval = valid_timespec64_to_timespec (its64.it_interval);
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value->it_value = valid_timespec64_to_timespec (its64.it_value);
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}
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return retval;
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}
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#endif
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weak_alias (__timer_gettime, timer_gettime)
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