/*
 *  linux/arch/cris/kernel/signal.c
 *
 *  Based on arch/i386/kernel/signal.c by
 *     Copyright (C) 1991, 1992  Linus Torvalds
 *     1997-11-28  Modified for POSIX.1b signals by Richard Henderson *
 *
 *  Ideas also taken from arch/arm.
 *
 *  Copyright (C) 2000-2007 Axis Communications AB
 *
 *  Authors:  Bjorn Wesen (bjornw@axis.com)
 *
 */

#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/errno.h>
#include <linux/wait.h>
#include <linux/ptrace.h>
#include <linux/unistd.h>
#include <linux/stddef.h>

#include <asm/processor.h>
#include <asm/ucontext.h>
#include <asm/uaccess.h>

#define DEBUG_SIG 0

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

/* a syscall in Linux/CRIS is a break 13 instruction which is 2 bytes */
/* manipulate regs so that upon return, it will be re-executed */

/* We rely on that pc points to the instruction after "break 13", so the
 * library must never do strange things like putting it in a delay slot.
 */
#define RESTART_CRIS_SYS(regs) regs->r10 = regs->orig_r10; regs->irp -= 2;

void do_signal(int canrestart, struct pt_regs *regs);

/*
 * Atomically swap in the new signal mask, and wait for a signal.  Define
 * dummy arguments to be able to reach the regs argument.  (Note that this
 * arrangement relies on old_sigset_t occupying one register.)
 */
int sys_sigsuspend(old_sigset_t mask, long r11, long r12, long r13, long mof,
        long srp, struct pt_regs *regs)
{
        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;
}

int sys_sigaction(int sig, const struct old_sigaction __user *act,
        struct old_sigaction *oact)
{
        struct k_sigaction new_ka, old_ka;
        int ret;

        if (act) {
                old_sigset_t mask;
                if (!access_ok(VERIFY_READ, act, sizeof(*act)) ||
                    __get_user(new_ka.sa.sa_handler, &act->sa_handler) ||
                    __get_user(new_ka.sa.sa_restorer, &act->sa_restorer))
                        return -EFAULT;
                __get_user(new_ka.sa.sa_flags, &act->sa_flags);
                __get_user(mask, &act->sa_mask);
                siginitset(&new_ka.sa.sa_mask, mask);
        }

        ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);

        if (!ret && oact) {
                if (!access_ok(VERIFY_WRITE, oact, sizeof(*oact)) ||
                    __put_user(old_ka.sa.sa_handler, &oact->sa_handler) ||
                    __put_user(old_ka.sa.sa_restorer, &oact->sa_restorer))
                        return -EFAULT;
                __put_user(old_ka.sa.sa_flags, &oact->sa_flags);
                __put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask);
        }

        return ret;
}

int sys_sigaltstack(const stack_t *uss, stack_t __user *uoss)
{
        return do_sigaltstack(uss, uoss, rdusp());
}


/*
 * Do a signal return; undo the signal stack.
 */

struct sigframe {
        struct sigcontext sc;
        unsigned long extramask[_NSIG_WORDS-1];
        unsigned char retcode[8];  /* trampoline code */
};

struct rt_sigframe {
        struct siginfo *pinfo;
        void *puc;
        struct siginfo info;
        struct ucontext uc;
        unsigned char retcode[8];  /* trampoline code */
};


static int
restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
{
        unsigned int err = 0;
        unsigned long old_usp;

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

        /* restore the regs from &sc->regs (same as sc, since regs is first)
         * (sc is already checked for VERIFY_READ since the sigframe was
         *  checked in sys_sigreturn previously)
         */

        if (__copy_from_user(regs, sc, sizeof(struct pt_regs)))
                goto badframe;

        /* make sure the U-flag is set so user-mode cannot fool us */

        regs->dccr |= 1 << 8;

        /* restore the old USP as it was before we stacked the sc etc.
         * (we cannot just pop the sigcontext since we aligned the sp and
         *  stuff after pushing it)
         */

        err |= __get_user(old_usp, &sc->usp);

        wrusp(old_usp);

        /* TODO: the other ports use regs->orig_XX to disable syscall checks
         * after this completes, but we don't use that mechanism. maybe we can
         * use it now ?
         */

        return err;

badframe:
        return 1;
}

/* Define dummy arguments to be able to reach the regs argument.  */

asmlinkage int sys_sigreturn(long r10, long r11, long r12, long r13, long mof,
                             long srp, struct pt_regs *regs)
{
        struct sigframe __user *frame = (struct sigframe *)rdusp();
        sigset_t set;

        /*
         * Since we stacked the signal on a dword boundary,
         * then frame should be dword aligned here.  If it's
         * not, then the user is trying to mess with us.
         */
        if (((long)frame) & 3)
                goto badframe;

        if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
                goto badframe;
        if (__get_user(set.sig[0], &frame->sc.oldmask)
            || (_NSIG_WORDS > 1
                && __copy_from_user(&set.sig[1], frame->extramask,
                                    sizeof(frame->extramask))))
                goto badframe;

        sigdelsetmask(&set, ~_BLOCKABLE);
        spin_lock_irq(&current->sighand->siglock);
        current->blocked = set;
        recalc_sigpending();
        spin_unlock_irq(&current->sighand->siglock);

        if (restore_sigcontext(regs, &frame->sc))
                goto badframe;

        /* TODO: SIGTRAP when single-stepping as in arm ? */

        return regs->r10;

badframe:
        force_sig(SIGSEGV, current);
        return 0;
}

/* Define dummy arguments to be able to reach the regs argument.  */

asmlinkage int sys_rt_sigreturn(long r10, long r11, long r12, long r13,
                                long mof, long srp, struct pt_regs *regs)
{
        struct rt_sigframe __user *frame = (struct rt_sigframe *)rdusp();
        sigset_t set;

        /*
         * Since we stacked the signal on a dword boundary,
         * then frame should be dword aligned here.  If it's
         * not, then the user is trying to mess with us.
         */
        if (((long)frame) & 3)
                goto badframe;

        if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
                goto badframe;
        if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
                goto badframe;

        sigdelsetmask(&set, ~_BLOCKABLE);
        spin_lock_irq(&current->sighand->siglock);
        current->blocked = set;
        recalc_sigpending();
        spin_unlock_irq(&current->sighand->siglock);

        if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
                goto badframe;

        if (do_sigaltstack(&frame->uc.uc_stack, NULL, rdusp()) == -EFAULT)
                goto badframe;

        return regs->r10;

badframe:
        force_sig(SIGSEGV, current);
        return 0;
}

/*
 * Set up a signal frame.
 */

static int setup_sigcontext(struct sigcontext __user *sc,
        struct pt_regs *regs, unsigned long mask)
{
        int err = 0;
        unsigned long usp = rdusp();

        /* copy the regs. they are first in sc so we can use sc directly */

        err |= __copy_to_user(sc, regs, sizeof(struct pt_regs));

        /* Set the frametype to CRIS_FRAME_NORMAL for the execution of
           the signal handler. The frametype will be restored to its previous
           value in restore_sigcontext. */
        regs->frametype = CRIS_FRAME_NORMAL;

        /* then some other stuff */

        err |= __put_user(mask, &sc->oldmask);

        err |= __put_user(usp, &sc->usp);

        return err;
}

/* Figure out where we want to put the new signal frame
 * - usually on the stack. */

static inline void __user *
get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size)
{
        unsigned long sp = rdusp();

        /* This is the X/Open sanctioned signal stack switching.  */
        if (ka->sa.sa_flags & SA_ONSTACK) {
                if (! on_sig_stack(sp))
                        sp = current->sas_ss_sp + current->sas_ss_size;
        }

        /* make sure the frame is dword-aligned */

        sp &= ~3;

        return (void __user*)(sp - frame_size);
}

/* grab and setup a signal frame.
 *
 * basically we stack a lot of state info, and arrange for the
 * user-mode program to return to the kernel using either a
 * trampoline which performs the syscall sigreturn, or a provided
 * user-mode trampoline.
 */

static int setup_frame(int sig, struct k_sigaction *ka,
                       sigset_t *set, struct pt_regs *regs)
{
        struct sigframe __user *frame;
        unsigned long return_ip;
        int err = 0;

        frame = get_sigframe(ka, regs, sizeof(*frame));

        if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
                goto give_sigsegv;

        err |= setup_sigcontext(&frame->sc, regs, set->sig[0]);
        if (err)
                goto give_sigsegv;

        if (_NSIG_WORDS > 1) {
                err |= __copy_to_user(frame->extramask, &set->sig[1],
                                      sizeof(frame->extramask));
        }
        if (err)
                goto give_sigsegv;

        /* Set up to return from userspace.  If provided, use a stub
           already in userspace.  */
        if (ka->sa.sa_flags & SA_RESTORER) {
                return_ip = (unsigned long)ka->sa.sa_restorer;
        } else {
                /* trampoline - the desired return ip is the retcode itself */
                return_ip = (unsigned long)&frame->retcode;
                /* This is movu.w __NR_sigreturn, r9; break 13; */
                err |= __put_user(0x9c5f,         (short __user*)(frame->retcode+0));
                err |= __put_user(__NR_sigreturn, (short __user*)(frame->retcode+2));
                err |= __put_user(0xe93d,         (short __user*)(frame->retcode+4));
        }

        if (err)
                goto give_sigsegv;

        /* Set up registers for signal handler */

        regs->irp = (unsigned long) ka->sa.sa_handler;  /* what we enter NOW   */
        regs->srp = return_ip;                          /* what we enter LATER */
        regs->r10 = sig;                                /* first argument is signo */

        /* actually move the usp to reflect the stacked frame */

        wrusp((unsigned long)frame);

        return 0;

give_sigsegv:
        force_sigsegv(sig, current);
        return -EFAULT;
}

static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
        sigset_t *set, struct pt_regs *regs)
{
        struct rt_sigframe __user *frame;
        unsigned long return_ip;
        int err = 0;

        frame = get_sigframe(ka, regs, sizeof(*frame));

        if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
                goto give_sigsegv;

        err |= __put_user(&frame->info, &frame->pinfo);
        err |= __put_user(&frame->uc, &frame->puc);
        err |= copy_siginfo_to_user(&frame->info, info);
        if (err)
                goto give_sigsegv;

        /* Clear all the bits of the ucontext we don't use.  */
        err |= __clear_user(&frame->uc, offsetof(struct ucontext, uc_mcontext));

        err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, set->sig[0]);

        err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));

        if (err)
                goto give_sigsegv;

        /* Set up to return from userspace.  If provided, use a stub
           already in userspace.  */
        if (ka->sa.sa_flags & SA_RESTORER) {
                return_ip = (unsigned long)ka->sa.sa_restorer;
        } else {
                /* trampoline - the desired return ip is the retcode itself */
                return_ip = (unsigned long)&frame->retcode;
                /* This is movu.w __NR_rt_sigreturn, r9; break 13; */
                err |= __put_user(0x9c5f, (short __user *)(frame->retcode+0));
                err |= __put_user(__NR_rt_sigreturn,
                        (short __user *)(frame->retcode+2));
                err |= __put_user(0xe93d, (short __user *)(frame->retcode+4));
        }

        if (err)
                goto give_sigsegv;

        /* TODO what is the current->exec_domain stuff and invmap ? */

        /* Set up registers for signal handler */

        /* What we enter NOW   */
        regs->irp = (unsigned long) ka->sa.sa_handler;
        /* What we enter LATER */
        regs->srp = return_ip;
        /* First argument is signo */
        regs->r10 = sig;
        /* Second argument is (siginfo_t *) */
        regs->r11 = (unsigned long)&frame->info;
        /* Third argument is unused */
        regs->r12 = 0;

        /* Actually move the usp to reflect the stacked frame */
        wrusp((unsigned long)frame);

        return 0;

give_sigsegv:
        force_sigsegv(sig, current);
        return -EFAULT;
}

/*
 * OK, we're invoking a handler
 */

static inline int handle_signal(int canrestart, unsigned long sig,
        siginfo_t *info, struct k_sigaction *ka,
        sigset_t *oldset, struct pt_regs *regs)
{
        int ret;

        /* Are we from a system call? */
        if (canrestart) {
                /* If so, check system call restarting.. */
                switch (regs->r10) {
                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 don't restart */
                        regs->r10 = -EINTR;
                        break;
                case -ERESTARTSYS:
                        /* ERESTARTSYS means to restart the syscall if
                         * there is no handler or the handler was
                         * registered with SA_RESTART */
                        if (!(ka->sa.sa_flags & SA_RESTART)) {
                                regs->r10 = -EINTR;
                                break;
                        }
                /* fallthrough */
                case -ERESTARTNOINTR:
                        /* ERESTARTNOINTR means that the syscall should
                         * be called again after the signal handler returns. */
                        RESTART_CRIS_SYS(regs);
                }
        }

        /* Set up the stack frame */
        if (ka->sa.sa_flags & SA_SIGINFO)
                ret = setup_rt_frame(sig, ka, info, oldset, regs);
        else
                ret = setup_frame(sig, ka, oldset, regs);

        if (ret == 0) {
                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, sig);
                recalc_sigpending();
                spin_unlock_irq(&current->sighand->siglock);
        }
        return ret;
}

/*
 * Note that 'init' is a special process: it doesn't get signals it doesn't
 * want to handle. Thus you cannot kill init even with a SIGKILL even by
 * mistake.
 *
 * Also note that the regs structure given here as an argument, is the latest
 * pushed pt_regs. It may or may not be the same as the first pushed registers
 * when the initial usermode->kernelmode transition took place. Therefore
 * we can use user_mode(regs) to see if we came directly from kernel or user
 * mode below.
 */

void do_signal(int canrestart, struct pt_regs *regs)
{
        siginfo_t info;
        int signr;
        struct k_sigaction ka;
        sigset_t *oldset;

        /*
         * We want the common case to go fast, which
         * is why we may in certain cases get here from
         * kernel mode. Just return without doing anything
         * if so.
         */
        if (!user_mode(regs))
                return;

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

        signr = get_signal_to_deliver(&info, &ka, regs, NULL);
        if (signr > 0) {
                /* Whee!  Actually deliver the signal.  */
                if (handle_signal(canrestart, signr, &info, &ka,
                                oldset, regs)) {
                        /* 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);
                }
                return;
        }

        /* Did we come from a system call? */
        if (canrestart) {
                /* Restart the system call - no handlers present */
                if (regs->r10 == -ERESTARTNOHAND ||
                    regs->r10 == -ERESTARTSYS ||
                    regs->r10 == -ERESTARTNOINTR) {
                        RESTART_CRIS_SYS(regs);
                }
                if (regs->r10 == -ERESTART_RESTARTBLOCK) {
                        regs->r10 = __NR_restart_syscall;
                        regs->irp -= 2;
                }
        }

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