/****************************************************************************
* sched/sig_action.c
*
* Copyright (C) 2007-2009, 2013 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* 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 <nuttx/config.h>
#include <stdint.h>
#include <signal.h>
#include <queue.h>
#include <sched.h>
#include <errno.h>
#include "os_internal.h"
#include "group_internal.h"
#include "sig_internal.h"
/****************************************************************************
* 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_CHILDSTATUS
* 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);
}
