/*
 * 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"

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));
}