/**************************************************************************** * sched/signal/sig_action.c * * Copyright (C) 2007-2009, 2013 Gregory Nutt. All rights reserved. * Author: Gregory Nutt * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * 3. Neither the name NuttX nor the names of its contributors may be * used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. * ****************************************************************************/ /**************************************************************************** * Included Files ****************************************************************************/ #include #include #include #include #include #include #include "sched/sched.h" #include "group/group.h" #include "signal/signal.h" /**************************************************************************** * Pre-processor Definitions ****************************************************************************/ #define COPY_SIGACTION(t,f) \ { (t)->sa_sigaction = (f)->sa_sigaction; \ (t)->sa_mask = (f)->sa_mask; \ (t)->sa_flags = (f)->sa_flags; } /**************************************************************************** * Private Type Declarations ****************************************************************************/ /**************************************************************************** * Global Variables ****************************************************************************/ /**************************************************************************** * Private Variables ****************************************************************************/ /**************************************************************************** * Private Functions ****************************************************************************/ /**************************************************************************** * Name: sig_allocateaction * * Description: * Allocate a new element for a sigaction queue * ****************************************************************************/ static FAR sigactq_t *sig_allocateaction(void) { FAR sigactq_t *sigact; /* Try to get the signal action structure from the free list */ sigact = (FAR sigactq_t*)sq_remfirst(&g_sigfreeaction); /* Check if we got one. */ if (!sigact) { /* Add another block of signal actions to the list */ sig_allocateactionblock(); /* And try again */ sigact = (FAR sigactq_t*)sq_remfirst(&g_sigfreeaction); ASSERT(sigact); } return sigact; } /**************************************************************************** * Public Functions ****************************************************************************/ /**************************************************************************** * Name: sigaction * * Description: * This function allows the calling process to examine and/or specify the * action to be associated with a specific signal. * * The structure sigaction, used to describe an action to be taken, is * defined to include the following members: * * - sa_u.sa_handler: Pointer to a signal-catching function * - sa_u.sa_sigaction: Alternative form of the signal-catching function * - sa_mask: An additional set of signals to be blocked during execution * of a signal catching function * - sa_flags. Special flags to affect the behavior of a signal. * * If the argument 'act' is not NULL, it points to a structure specifying * the action to be associated with the specified signal. If the argument * 'oact' is not NULL, the action previously associated with the signal * is stored in the location pointed to by the argument 'oact.' * * When a signal is caught by a signal-catching function installed by * sigaction() function, a new signal mask is calculated and installed for * the duration of the signal-catching function. This mask is formed by * taking the union of the current signal mask and the value of the * sa_mask for the signal being delivered and then including the signal * being delivered. If and when the user's signal handler returns, the * original signal mask is restored. * * Once an action is installed for a specific signal, it remains installed * until another action is explicitly requested by another call to sigaction(). * * Parameters: * sig - Signal of interest * act - Location of new handler * oact - Location to store only handler * * Return Value: * 0 (OK), or -1 (ERROR) if the signal number is invalid. * (errno is not set) * * Assumptions: * * POSIX Compatibility: * - There are no default actions so the special value SIG_DFL is treated * like SIG_IGN. * - All sa_flags in struct sigaction of act input are ignored (all * treated like SA_SIGINFO). The one exception is if CONFIG_SCHED_CHILD_STATUS * is defined; then SA_NOCLDWAIT is supported but only for SIGCHLD * ****************************************************************************/ int sigaction(int signo, FAR const struct sigaction *act, FAR struct sigaction *oact) { FAR struct tcb_s *rtcb = (FAR struct tcb_s*)g_readytorun.head; FAR sigactq_t *sigact; /* Since sigactions can only be installed from the running thread of * execution, no special precautions should be necessary. */ /* Verify the signal number */ if (!GOOD_SIGNO(signo)) { set_errno(EINVAL); return ERROR; } /* Find the signal in the sigactionq */ sigact = sig_findaction(rtcb, signo); /* Return the old sigaction value if so requested */ if (oact) { if (sigact) { COPY_SIGACTION(oact, &sigact->act); } else { /* There isn't an old value */ oact->sa_u._sa_handler = NULL; oact->sa_mask = NULL_SIGNAL_SET; oact->sa_flags = 0; } } /* If the argument act is a null pointer, signal handling is unchanged; * thus, the call can be used to enquire about the current handling of * a given signal. */ if (!act) { return OK; } #if defined(CONFIG_SCHED_HAVE_PARENT) && defined(CONFIG_SCHED_CHILD_STATUS) /* Handle a special case. Retention of child status can be suppressed * if signo == SIGCHLD and sa_flags == SA_NOCLDWAIT. * * POSIX.1 leaves it unspecified whether a SIGCHLD signal is generated * when a child process terminates. In NuttX, a SIGCHLD signal is * generated in this case; but in some other implementations, it may not * be. */ if (signo == SIGCHLD && (act->sa_flags & SA_NOCLDWAIT) != 0) { irqstate_t flags; /* We do require a critical section to muck with the TCB values that * can be modified by the child thread. */ flags = irqsave(); /* Mark that status should be not be retained */ rtcb->group->tg_flags |= GROUP_FLAG_NOCLDWAIT; /* Free all pending exit status */ group_removechildren(rtcb->group); irqrestore(flags); } #endif /* Handle the case where no sigaction is supplied (SIG_IGN) */ if (act->sa_u._sa_handler == SIG_IGN) { /* Do we still have a sigaction container from the previous setting? */ if (sigact) { /* Yes.. Remove it from sigactionq */ sq_rem((FAR sq_entry_t*)sigact, &rtcb->sigactionq); /* And deallocate it */ sig_releaseaction(sigact); } } /* A sigaction has been supplied */ else { /* Do we still have a sigaction container from the previous setting? * If so, then re-use for the new signal action. */ if (!sigact) { /* No.. Then we need to allocate one for the new action. */ sigact = sig_allocateaction(); /* An error has occurred if we could not allocate the sigaction */ if (!sigact) { set_errno(ENOMEM); return ERROR; } /* Put the signal number in the queue entry */ sigact->signo = (uint8_t)signo; /* Add the new sigaction to sigactionq */ sq_addlast((FAR sq_entry_t*)sigact, &rtcb->sigactionq); } /* Set the new sigaction */ COPY_SIGACTION(&sigact->act, act); } return OK; } /**************************************************************************** * Name: sig_releaseaction * * Description: * Deallocate a sigaction Q entry * ****************************************************************************/ void sig_releaseaction(FAR sigactq_t *sigact) { /* Just put it back on the free list */ sq_addlast((FAR sq_entry_t*)sigact, &g_sigfreeaction); }