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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.
98 lines
2.9 KiB
C
98 lines
2.9 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 <pthread.h>
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#include <setjmp.h>
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#include <signal.h>
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#include <sys/types.h>
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/* Nonzero if the system calls are not available. */
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extern int __no_posix_timers attribute_hidden;
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/* Callback to start helper thread. */
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extern void __start_helper_thread (void) attribute_hidden;
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/* Control variable for helper thread creation. */
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extern pthread_once_t __helper_once attribute_hidden;
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/* TID of the helper thread. */
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extern pid_t __helper_tid attribute_hidden;
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/* List of active SIGEV_THREAD timers. */
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extern struct timer *__active_timer_sigev_thread attribute_hidden;
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/* Lock for the __active_timer_sigev_thread. */
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extern pthread_mutex_t __active_timer_sigev_thread_lock attribute_hidden;
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/* Type of timers in the kernel. */
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typedef int kernel_timer_t;
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/* Internal representation of SIGEV_THREAD timer. */
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struct timer
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{
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kernel_timer_t ktimerid;
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void (*thrfunc) (sigval_t);
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sigval_t sival;
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pthread_attr_t attr;
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/* Next element in list of active SIGEV_THREAD timers. */
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struct timer *next;
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};
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/* For !SIGEV_THREAD, the resulting 'timer_t' is the returned kernel timer
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identifer (kernel_timer_t), while for SIGEV_THREAD it uses the fact malloc
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returns at least _Alignof (max_align_t) pointers plus that valid
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kernel_timer_t are always positive to set the MSB bit of the returned
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'timer_t' to indicate the timer handles a SIGEV_THREAD. */
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static inline timer_t
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kernel_timer_to_timerid (kernel_timer_t ktimerid)
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{
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return (timer_t) ((intptr_t) ktimerid);
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}
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static inline timer_t
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timer_to_timerid (struct timer *ptr)
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{
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return (timer_t) (INTPTR_MIN | (uintptr_t) ptr >> 1);
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}
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static inline bool
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timer_is_sigev_thread (timer_t timerid)
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{
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return (intptr_t) timerid < 0;
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}
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static inline struct timer *
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timerid_to_timer (timer_t timerid)
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{
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return (struct timer *)((uintptr_t) timerid << 1);
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}
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static inline kernel_timer_t
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timerid_to_kernel_timer (timer_t timerid)
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{
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if (timer_is_sigev_thread (timerid))
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return timerid_to_timer (timerid)->ktimerid;
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else
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return (kernel_timer_t) ((uintptr_t) timerid);
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}
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