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signal.c

/*
 * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 * Licensed under the GPL
 */

#include "linux/module.h"
#include "linux/ptrace.h"
#include "linux/sched.h"
#include "asm/siginfo.h"
#include "asm/signal.h"
#include "asm/unistd.h"
#include "frame_kern.h"
#include "kern_util.h"
#include "sigcontext.h"

EXPORT_SYMBOL(block_signals);
EXPORT_SYMBOL(unblock_signals);

#define _S(nr) (1<<((nr)-1))

#define _BLOCKABLE (~(_S(SIGKILL) | _S(SIGSTOP)))

/*
 * OK, we're invoking a handler
 */
static int handle_signal(struct pt_regs *regs, unsigned long signr,
                   struct k_sigaction *ka, siginfo_t *info,
                   sigset_t *oldset)
{
      unsigned long sp;
      int err;

      /* Always make any pending restarted system calls return -EINTR */
      current_thread_info()->restart_block.fn = do_no_restart_syscall;

      /* Did we come from a system call? */
      if (PT_REGS_SYSCALL_NR(regs) >= 0) {
            /* If so, check system call restarting.. */
            switch(PT_REGS_SYSCALL_RET(regs)) {
            case -ERESTART_RESTARTBLOCK:
            case -ERESTARTNOHAND:
                  PT_REGS_SYSCALL_RET(regs) = -EINTR;
                  break;

            case -ERESTARTSYS:
                  if (!(ka->sa.sa_flags & SA_RESTART)) {
                        PT_REGS_SYSCALL_RET(regs) = -EINTR;
                        break;
                  }
            /* fallthrough */
            case -ERESTARTNOINTR:
                  PT_REGS_RESTART_SYSCALL(regs);
                  PT_REGS_ORIG_SYSCALL(regs) = PT_REGS_SYSCALL_NR(regs);
                  break;
            }
      }

      sp = PT_REGS_SP(regs);
      if ((ka->sa.sa_flags & SA_ONSTACK) && (sas_ss_flags(sp) == 0))
            sp = current->sas_ss_sp + current->sas_ss_size;

#ifdef CONFIG_ARCH_HAS_SC_SIGNALS
      if (!(ka->sa.sa_flags & SA_SIGINFO))
            err = setup_signal_stack_sc(sp, signr, ka, regs, oldset);
      else
#endif
            err = setup_signal_stack_si(sp, signr, ka, regs, info, oldset);

      if (err) {
            spin_lock_irq(&current->sighand->siglock);
            current->blocked = *oldset;
            recalc_sigpending();
            spin_unlock_irq(&current->sighand->siglock);
            force_sigsegv(signr, current);
      } else {
            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);
      }

      return err;
}

static int kern_do_signal(struct pt_regs *regs)
{
      struct k_sigaction ka_copy;
      siginfo_t info;
      sigset_t *oldset;
      int sig, handled_sig = 0;

      if (test_thread_flag(TIF_RESTORE_SIGMASK))
            oldset = &current->saved_sigmask;
      else
            oldset = &current->blocked;

      while ((sig = get_signal_to_deliver(&info, &ka_copy, regs, NULL)) > 0) {
            handled_sig = 1;
            /* Whee!  Actually deliver the signal.  */
            if (!handle_signal(regs, sig, &ka_copy, &info, oldset)) {
                  /*
                   * a signal was successfully delivered; the saved
                   * sigmask will have been stored in the signal frame,
                   * and will be restored by sigreturn, so we can simply
                   * clear the TIF_RESTORE_SIGMASK flag
                   */
                  if (test_thread_flag(TIF_RESTORE_SIGMASK))
                        clear_thread_flag(TIF_RESTORE_SIGMASK);
                  break;
            }
      }

      /* Did we come from a system call? */
      if (!handled_sig && (PT_REGS_SYSCALL_NR(regs) >= 0)) {
            /* Restart the system call - no handlers present */
            switch(PT_REGS_SYSCALL_RET(regs)) {
            case -ERESTARTNOHAND:
            case -ERESTARTSYS:
            case -ERESTARTNOINTR:
                  PT_REGS_ORIG_SYSCALL(regs) = PT_REGS_SYSCALL_NR(regs);
                  PT_REGS_RESTART_SYSCALL(regs);
                  break;
            case -ERESTART_RESTARTBLOCK:
                  PT_REGS_ORIG_SYSCALL(regs) = __NR_restart_syscall;
                  PT_REGS_RESTART_SYSCALL(regs);
                  break;
            }
      }

      /*
       * This closes a way to execute a system call on the host.  If
       * you set a breakpoint on a system call instruction and singlestep
       * from it, the tracing thread used to PTRACE_SINGLESTEP the process
       * rather than PTRACE_SYSCALL it, allowing the system call to execute
       * on the host.  The tracing thread will check this flag and
       * PTRACE_SYSCALL if necessary.
       */
      if (current->ptrace & PT_DTRACE)
            current->thread.singlestep_syscall =
                  is_syscall(PT_REGS_IP(&current->thread.regs));

      /*
       * if there's no signal to deliver, we just put the saved sigmask
       * back
       */
      if (!handled_sig && test_thread_flag(TIF_RESTORE_SIGMASK)) {
            clear_thread_flag(TIF_RESTORE_SIGMASK);
            sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
      }
      return handled_sig;
}

int do_signal(void)
{
      return kern_do_signal(&current->thread.regs);
}

/*
 * Atomically swap in the new signal mask, and wait for a signal.
 */
long sys_sigsuspend(int history0, int history1, old_sigset_t mask)
{
      mask &= _BLOCKABLE;
      spin_lock_irq(&current->sighand->siglock);
      current->saved_sigmask = current->blocked;
      siginitset(&current->blocked, mask);
      recalc_sigpending();
      spin_unlock_irq(&current->sighand->siglock);

      current->state = TASK_INTERRUPTIBLE;
      schedule();
      set_thread_flag(TIF_RESTORE_SIGMASK);
      return -ERESTARTNOHAND;
}

long sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss)
{
      return do_sigaltstack(uss, uoss, PT_REGS_SP(&current->thread.regs));
}

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