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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.
146 lines
4.3 KiB
C
146 lines
4.3 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 <pthread.h>
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#include <signal.h>
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#include <stdlib.h>
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#include <string.h>
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#include <time.h>
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#include <sysdep.h>
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#include <internaltypes.h>
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#include <nptl/pthreadP.h>
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#include "kernel-posix-timers.h"
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#include "kernel-posix-cpu-timers.h"
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#ifdef timer_create_alias
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# define timer_create timer_create_alias
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#endif
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int
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timer_create (clockid_t clock_id, struct sigevent *evp, timer_t *timerid)
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{
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#undef timer_create
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{
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clockid_t syscall_clockid = (clock_id == CLOCK_PROCESS_CPUTIME_ID
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? MAKE_PROCESS_CPUCLOCK (0, CPUCLOCK_SCHED)
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: clock_id == CLOCK_THREAD_CPUTIME_ID
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? MAKE_THREAD_CPUCLOCK (0, CPUCLOCK_SCHED)
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: clock_id);
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/* If the user wants notification via a thread we need to handle
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this special. */
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if (evp == NULL
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|| __builtin_expect (evp->sigev_notify != SIGEV_THREAD, 1))
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{
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struct sigevent local_evp;
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if (evp == NULL)
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{
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/* The kernel has to pass up the timer ID which is a
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userlevel object. Therefore we cannot leave it up to
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the kernel to determine it. */
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local_evp.sigev_notify = SIGEV_SIGNAL;
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local_evp.sigev_signo = SIGALRM;
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local_evp.sigev_value.sival_ptr = NULL;
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evp = &local_evp;
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}
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kernel_timer_t ktimerid;
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if (INLINE_SYSCALL_CALL (timer_create, syscall_clockid, evp,
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&ktimerid) == -1)
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return -1;
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*timerid = kernel_timer_to_timerid (ktimerid);
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}
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else
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{
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/* Create the helper thread. */
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pthread_once (&__helper_once, __start_helper_thread);
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if (__helper_tid == 0)
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{
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/* No resources to start the helper thread. */
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__set_errno (EAGAIN);
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return -1;
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}
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struct timer *newp = malloc (sizeof (struct timer));
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if (newp == NULL)
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return -1;
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/* Copy the thread parameters the user provided. */
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newp->sival = evp->sigev_value;
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newp->thrfunc = evp->sigev_notify_function;
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/* We cannot simply copy the thread attributes since the
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implementation might keep internal information for
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each instance. */
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pthread_attr_init (&newp->attr);
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if (evp->sigev_notify_attributes != NULL)
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{
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struct pthread_attr *nattr;
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struct pthread_attr *oattr;
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nattr = (struct pthread_attr *) &newp->attr;
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oattr = (struct pthread_attr *) evp->sigev_notify_attributes;
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nattr->schedparam = oattr->schedparam;
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nattr->schedpolicy = oattr->schedpolicy;
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nattr->flags = oattr->flags;
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nattr->guardsize = oattr->guardsize;
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nattr->stackaddr = oattr->stackaddr;
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nattr->stacksize = oattr->stacksize;
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}
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/* In any case set the detach flag. */
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pthread_attr_setdetachstate (&newp->attr, PTHREAD_CREATE_DETACHED);
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/* Create the event structure for the kernel timer. */
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struct sigevent sev =
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{ .sigev_value.sival_ptr = newp,
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.sigev_signo = SIGTIMER,
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.sigev_notify = SIGEV_SIGNAL | SIGEV_THREAD_ID,
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._sigev_un = { ._pad = { [0] = __helper_tid } } };
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/* Create the timer. */
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int res;
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res = INTERNAL_SYSCALL_CALL (timer_create, syscall_clockid, &sev,
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&newp->ktimerid);
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if (INTERNAL_SYSCALL_ERROR_P (res))
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{
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free (newp);
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__set_errno (INTERNAL_SYSCALL_ERRNO (res));
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return -1;
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}
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/* Add to the queue of active timers with thread delivery. */
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pthread_mutex_lock (&__active_timer_sigev_thread_lock);
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newp->next = __active_timer_sigev_thread;
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__active_timer_sigev_thread = newp;
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pthread_mutex_unlock (&__active_timer_sigev_thread_lock);
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*timerid = timer_to_timerid (newp);
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}
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}
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return 0;
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}
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