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signal.c

/*
 * Common signal handling code for both 32 and 64 bits
 *
 *    Copyright (c) 2007 Benjamin Herrenschmidt, IBM Coproration
 *    Extracted from signal_32.c and signal_64.c
 *
 * This file is subject to the terms and conditions of the GNU General
 * Public License.  See the file README.legal in the main directory of
 * this archive for more details.
 */

#include <linux/tracehook.h>
#include <linux/signal.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>

#include "signal.h"

/* Log an error when sending an unhandled signal to a process. Controlled
 * through debug.exception-trace sysctl.
 */

int show_unhandled_signals = 0;

/*
 * Allocate space for the signal frame
 */
void __user * get_sigframe(struct k_sigaction *ka, struct pt_regs *regs,
                     size_t frame_size)
{
        unsigned long oldsp, newsp;

        /* Default to using normal stack */
        oldsp = regs->gpr[1];

      /* Check for alt stack */
      if ((ka->sa.sa_flags & SA_ONSTACK) &&
          current->sas_ss_size && !on_sig_stack(oldsp))
            oldsp = (current->sas_ss_sp + current->sas_ss_size);

      /* Get aligned frame */
      newsp = (oldsp - frame_size) & ~0xFUL;

      /* Check access */
      if (!access_ok(VERIFY_WRITE, (void __user *)newsp, oldsp - newsp))
            return NULL;

        return (void __user *)newsp;
}


/*
 * Restore the user process's signal mask
 */
void restore_sigmask(sigset_t *set)
{
      sigdelsetmask(set, ~_BLOCKABLE);
      spin_lock_irq(&current->sighand->siglock);
      current->blocked = *set;
      recalc_sigpending();
      spin_unlock_irq(&current->sighand->siglock);
}

static void check_syscall_restart(struct pt_regs *regs, struct k_sigaction *ka,
                          int has_handler)
{
      unsigned long ret = regs->gpr[3];
      int restart = 1;

      /* syscall ? */
      if (TRAP(regs) != 0x0C00)
            return;

      /* error signalled ? */
      if (!(regs->ccr & 0x10000000))
            return;

      switch (ret) {
      case ERESTART_RESTARTBLOCK:
      case ERESTARTNOHAND:
            /* ERESTARTNOHAND means that the syscall should only be
             * restarted if there was no handler for the signal, and since
             * we only get here if there is a handler, we dont restart.
             */
            restart = !has_handler;
            break;
      case ERESTARTSYS:
            /* ERESTARTSYS means to restart the syscall if there is no
             * handler or the handler was registered with SA_RESTART
             */
            restart = !has_handler || (ka->sa.sa_flags & SA_RESTART) != 0;
            break;
      case ERESTARTNOINTR:
            /* ERESTARTNOINTR means that the syscall should be
             * called again after the signal handler returns.
             */
            break;
      default:
            return;
      }
      if (restart) {
            if (ret == ERESTART_RESTARTBLOCK)
                  regs->gpr[0] = __NR_restart_syscall;
            else
                  regs->gpr[3] = regs->orig_gpr3;
            regs->nip -= 4;
            regs->result = 0;
      } else {
            regs->result = -EINTR;
            regs->gpr[3] = EINTR;
            regs->ccr |= 0x10000000;
      }
}

static int do_signal_pending(sigset_t *oldset, struct pt_regs *regs)
{
      siginfo_t info;
      int signr;
      struct k_sigaction ka;
      int ret;
      int is32 = is_32bit_task();

      if (current_thread_info()->local_flags & _TLF_RESTORE_SIGMASK)
            oldset = &current->saved_sigmask;
      else if (!oldset)
            oldset = &current->blocked;

      signr = get_signal_to_deliver(&info, &ka, regs, NULL);

      /* Is there any syscall restart business here ? */
      check_syscall_restart(regs, &ka, signr > 0);

      if (signr <= 0) {
            struct thread_info *ti = current_thread_info();
            /* No signal to deliver -- put the saved sigmask back */
            if (ti->local_flags & _TLF_RESTORE_SIGMASK) {
                  ti->local_flags &= ~_TLF_RESTORE_SIGMASK;
                  sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
            }
            return 0;               /* no signals delivered */
      }

        /*
       * Reenable the DABR before delivering the signal to
       * user space. The DABR will have been cleared if it
       * triggered inside the kernel.
       */
      if (current->thread.dabr) {
            set_dabr(current->thread.dabr);
#if defined(CONFIG_BOOKE)
            mtspr(SPRN_DBCR0, current->thread.dbcr0);
#endif
      }

      if (is32) {
            if (ka.sa.sa_flags & SA_SIGINFO)
                  ret = handle_rt_signal32(signr, &ka, &info, oldset,
                              regs);
            else
                  ret = handle_signal32(signr, &ka, &info, oldset,
                              regs);
      } else {
            ret = handle_rt_signal64(signr, &ka, &info, oldset, regs);
      }

      if (ret) {
            spin_lock_irq(&current->sighand->siglock);
            sigorsets(&current->blocked, &current->blocked,
                    &ka.sa.sa_mask);
            if (!(ka.sa.sa_flags & SA_NODEFER))
                  sigaddset(&current->blocked, signr);
            recalc_sigpending();
            spin_unlock_irq(&current->sighand->siglock);

            /*
             * A signal was successfully delivered; the saved sigmask is in
             * its frame, and we can clear the TLF_RESTORE_SIGMASK flag.
             */
            current_thread_info()->local_flags &= ~_TLF_RESTORE_SIGMASK;

            /*
             * Let tracing know that we've done the handler setup.
             */
            tracehook_signal_handler(signr, &info, &ka, regs,
                               test_thread_flag(TIF_SINGLESTEP));
      }

      return ret;
}

void do_signal(struct pt_regs *regs, unsigned long thread_info_flags)
{
      if (thread_info_flags & _TIF_SIGPENDING)
            do_signal_pending(NULL, regs);

      if (thread_info_flags & _TIF_NOTIFY_RESUME) {
            clear_thread_flag(TIF_NOTIFY_RESUME);
            tracehook_notify_resume(regs);
      }
}

long sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss,
            unsigned long r5, unsigned long r6, unsigned long r7,
            unsigned long r8, struct pt_regs *regs)
{
      return do_sigaltstack(uss, uoss, regs->gpr[1]);
}

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