nuttx/arch/arm/src/armv7-a/arm_schedulesigaction.c

/****************************************************************************
 * arch/arm/src/armv7-a/arm_schedulesigaction.c
 *
 *   Copyright (C) 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 <sched.h>
#include <debug.h>

#include <nuttx/arch.h>

#include "arm.h"
#include "sched/sched.h"
#include "up_internal.h"
#include "up_arch.h"

#ifndef CONFIG_DISABLE_SIGNALS

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

/****************************************************************************
 * Private Data
 ****************************************************************************/

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: up_schedule_sigaction
 *
 * Description:
 *   This function is called by the OS when one or more
 *   signal handling actions have been queued for execution.
 *   The architecture specific code must configure things so
 *   that the 'igdeliver' callback is executed on the thread
 *   specified by 'tcb' as soon as possible.
 *
 *   This function may be called from interrupt handling logic.
 *
 *   This operation should not cause the task to be unblocked
 *   nor should it cause any immediate execution of sigdeliver.
 *   Typically, a few cases need to be considered:
 *
 *   (1) This function may be called from an interrupt handler
 *       During interrupt processing, all xcptcontext structures
 *       should be valid for all tasks.  That structure should
 *       be modified to invoke sigdeliver() either on return
 *       from (this) interrupt or on some subsequent context
 *       switch to the recipient task.
 *   (2) If not in an interrupt handler and the tcb is NOT
 *       the currently executing task, then again just modify
 *       the saved xcptcontext structure for the recipient
 *       task so it will invoke sigdeliver when that task is
 *       later resumed.
 *   (3) If not in an interrupt handler and the tcb IS the
 *       currently executing task -- just call the signal
 *       handler now.
 *
 ****************************************************************************/

void up_schedule_sigaction(struct tcb_s *tcb, sig_deliver_t sigdeliver)
{
  /* Refuse to handle nested signal actions */

  sdbg("tcb=0x%p sigdeliver=0x%p\n", tcb, sigdeliver);

  if (!tcb->xcp.sigdeliver)
    {
      irqstate_t flags;

      /* Make sure that interrupts are disabled */

      flags = irqsave();

      /* First, handle some special cases when the signal is being delivered
       * to the currently executing task.
       */

      sdbg("rtcb=0x%p current_regs=0x%p\n", g_readytorun.head, current_regs);

      if (tcb == (struct tcb_s*)g_readytorun.head)
        {
          /* CASE 1:  We are not in an interrupt handler and a task is
           * signalling itself for some reason.
           */

          if (!current_regs)
            {
              /* In this case just deliver the signal now. */

              sigdeliver(tcb);
            }

          /* CASE 2:  We are in an interrupt handler AND the interrupted
           * task is the same as the one that must receive the signal, then
           * we will have to modify the return state as well as the state
           * in the TCB.
           *
           * Hmmm... there looks like a latent bug here: The following logic
           * would fail in the strange case where we are in an interrupt
           * handler, the thread is signalling itself, but a context switch
           * to another task has occurred so that current_regs does not
           * refer to the thread at g_readytorun.head!
           */

          else
            {
              /* Save the return lr and cpsr and one scratch register
               * These will be restored by the signal trampoline after
               * the signals have been delivered.
               */

              tcb->xcp.sigdeliver       = sigdeliver;
              tcb->xcp.saved_pc         = current_regs[REG_PC];
              tcb->xcp.saved_cpsr       = current_regs[REG_CPSR];

              /* Then set up to vector to the trampoline with interrupts
               * disabled
               */

              current_regs[REG_PC]      = (uint32_t)up_sigdeliver;
              current_regs[REG_CPSR]    = (PSR_MODE_SVC | PSR_I_BIT | PSR_F_BIT);

              /* And make sure that the saved context in the TCB is the same
               * as the interrupt return context.
               */

              up_savestate(tcb->xcp.regs);
            }
        }

      /* Otherwise, we are (1) signaling a task is not running from an
       * interrupt handler or (2) we are not in an interrupt handler and the
       * running task is signalling some non-running task.
       */

      else
        {
          /* Save the return lr and cpsr and one scratch register.  These
           * will be restored by the signal trampoline after the signals
           * have been delivered.
           */

          tcb->xcp.sigdeliver       = sigdeliver;
          tcb->xcp.saved_pc         = tcb->xcp.regs[REG_PC];
          tcb->xcp.saved_cpsr       = tcb->xcp.regs[REG_CPSR];

          /* Then set up to vector to the trampoline with interrupts
           * disabled
           */

          tcb->xcp.regs[REG_PC]      = (uint32_t)up_sigdeliver;
          tcb->xcp.regs[REG_CPSR]    = (PSR_MODE_SVC | PSR_I_BIT | PSR_F_BIT);
        }

      irqrestore(flags);
    }
}

#endif /* !CONFIG_DISABLE_SIGNALS */