text: /****************************************************************************
   * arch/risc-v/src/rv32im/up_sigdeliver.c
   *
   *   Copyright (C) 2011, 2015, 2018-2018 Gregory Nutt. All rights reserved.
   *   Author: Gregory Nutt <gnutt@nuttx.org>
   *
   *   Modified for RISC-V:
   *
   *   Copyright (C) 2016 Ken Pettit. All rights reserved.
   *   Author: Ken Pettit <pettitkd@gmail.com>
   *
   * 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 <inttypes.h>
  #include <stdint.h>
  #include <sched.h>
  #include <syscall.h>
  #include <debug.h>
  
  #include <nuttx/irq.h>
  #include <nuttx/arch.h>
  #include <nuttx/board.h>
  #include <arch/board/board.h>
  
  #include "sched/sched.h"
  #include "riscv_internal.h"
  #include "riscv_arch.h"
  
  /****************************************************************************
   * Public Functions
   ****************************************************************************/
  
  /****************************************************************************
   * Name: up_sigdeliver
   *
   * Description:
   *   This is the a signal handling trampoline.  When a signal action was
   *   posted.  The task context was mucked with and forced to branch to this
   *   location with interrupts disabled.
   *
   ****************************************************************************/
  
  void up_sigdeliver(void)
  {
    struct tcb_s *rtcb = this_task();
    uint32_t regs[XCPTCONTEXT_REGS];
  
    /* Save the errno.  This must be preserved throughout the signal handling
     * so that the user code final gets the correct errno value (probably
     * EINTR).
     */
  
    int saved_errno = get_errno();
  
    board_autoled_on(LED_SIGNAL);
  
    sinfo("rtcb=%p sigdeliver=%p sigpendactionq.head=%p\n",
          rtcb, rtcb->xcp.sigdeliver, rtcb->sigpendactionq.head);
    DEBUGASSERT(rtcb->xcp.sigdeliver != NULL);
  
    /* Save the return state on the stack. */
  
    up_copystate(regs, rtcb->xcp.regs);
  
  #ifndef CONFIG_SUPPRESS_INTERRUPTS
    /* Then make sure that interrupts are enabled.  Signal handlers must always
     * run with interrupts enabled.
     */
  
    up_irq_enable();
  #endif
  
    /* Deliver the signals */
  
    ((sig_deliver_t)rtcb->xcp.sigdeliver)(rtcb);
  
    /* Output any debug messages BEFORE restoring errno (because they may
     * alter errno), then disable interrupts again and restore the original
     * errno that is needed by the user logic (it is probably EINTR).
     */
  
    sinfo("Resuming EPC: %08" PRIx32 " INT_CTX: %08" PRIx32 "\n",
          regs[REG_EPC], regs[REG_INT_CTX]);
  
    up_irq_save();
    set_errno(saved_errno);
  
    /* Modify the saved return state with the actual saved values in the
     * TCB.  This depends on the fact that nested signal handling is
     * not supported.  Therefore, these values will persist throughout the
     * signal handling action.
     *
     * Keeping this data in the TCB resolves a security problem in protected
     * and kernel mode:  The regs[] array is visible on the user stack and
     * could be modified by a hostile program.
     */
  
    regs[REG_EPC]        = rtcb->xcp.saved_epc;
    regs[REG_INT_CTX]    = rtcb->xcp.saved_int_ctx;
    rtcb->xcp.sigdeliver = NULL;  /* Allows next handler to be scheduled */
  
    /* Then restore the correct state for this thread of
     * execution.
     */
  
    board_autoled_off(LED_SIGNAL);
    up_fullcontextrestore(regs);
  
    /* up_fullcontextrestore() should not return but could if the software
     * interrupts are disabled.
     */
  
    DEBUGPANIC();
  }
  