/*
 * Copyright (C) 2003, Axis Communications AB.
 */

#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/slab.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 <linux/syscalls.h>
#include <linux/vmalloc.h>

#include <asm/io.h>
#include <asm/processor.h>
#include <asm/ucontext.h>
#include <asm/uaccess.h>
#include <arch/hwregs/cpu_vect.h>

extern unsigned long cris_signal_return_page;

/*
 * A syscall in CRIS is really a "break 13" instruction, which is 2
 * bytes. The registers is manipulated so upon return the instruction
 * will be executed again.
 *
 * This relies on that PC points to the instruction after the break call.
 */
#define RESTART_CRIS_SYS(regs) regs->r10 = regs->orig_r10; regs->erp -= 2;

/* Signal frames. */
struct signal_frame {
        struct sigcontext sc;
        unsigned long extramask[_NSIG_WORDS - 1];
        unsigned char retcode[8];       /* Trampoline code. */
};

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

void do_signal(int restart, struct pt_regs *regs);
void keep_debug_flags(unsigned long oldccs, unsigned long oldspc,
                      struct pt_regs *regs);

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->restart_block.fn = do_no_restart_syscall;

        /*
         * Restore the registers from &sc->regs. sc is already checked
         * for VERIFY_READ since the signal_frame was previously
         * checked in sys_sigreturn().
         */
        if (__copy_from_user(regs, sc, sizeof(struct pt_regs)))
                goto badframe;

        /* Make that the user-mode flag is set. */
        regs->ccs |= (1 << (U_CCS_BITNR + CCS_SHIFT));

        /* Don't perform syscall restarting */
        regs->exs = -1;

        /* Restore the old USP. */
        err |= __get_user(old_usp, &sc->usp);
        wrusp(old_usp);

        return err;

badframe:
        return 1;
}

asmlinkage int sys_sigreturn(void)
{
        struct pt_regs *regs = current_pt_regs();
        sigset_t set;
        struct signal_frame __user *frame;
        unsigned long oldspc = regs->spc;
        unsigned long oldccs = regs->ccs;

        frame = (struct signal_frame *) rdusp();

        /*
         * Since the signal is stacked on a dword boundary, the frame
         * should be dword aligned here as well. It it's not, then the
         * user is trying some funny business.
         */
        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;

        set_current_blocked(&set);

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

        keep_debug_flags(oldccs, oldspc, regs);

        return regs->r10;

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

asmlinkage int sys_rt_sigreturn(void)
{
        struct pt_regs *regs = current_pt_regs();
        sigset_t set;
        struct rt_signal_frame __user *frame;
        unsigned long oldspc = regs->spc;
        unsigned long oldccs = regs->ccs;

        frame = (struct rt_signal_frame *) rdusp();

        /*
         * Since the signal is stacked on a dword boundary, the frame
         * should be dword aligned here as well. It it's not, then the
         * user is trying some funny business.
         */
        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;

        set_current_blocked(&set);

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

        if (restore_altstack(&frame->uc.uc_stack))
                goto badframe;

        keep_debug_flags(oldccs, oldspc, regs);

        return regs->r10;

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

/* Setup a signal frame. */
static int
setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
                 unsigned long mask)
{
        int err;
        unsigned long usp;

        err = 0;
        usp = rdusp();

        /*
         * Copy the registers. They are located first in sc, so it's
         * possible to use sc directly.
         */
        err |= __copy_to_user(sc, regs, sizeof(struct pt_regs));

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

        return err;
}

/* Figure out where to put the new signal frame - usually on the stack. */
static inline void __user *
get_sigframe(struct ksignal *ksig, size_t frame_size)
{
        unsigned long sp = sigsp(rdusp(), ksig);

        /* Make sure the frame is dword-aligned. */
        sp &= ~3;

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

/* Grab and setup a signal frame.
 *
 * Basically a lot of state-info is stacked, and arranged for the
 * user-mode program to return to the kernel using either a trampiline
 * which performs the syscall sigreturn(), or a provided user-mode
 * trampoline.
  */
static int
setup_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
{
        int err;
        unsigned long return_ip;
        struct signal_frame __user *frame;

        err = 0;
        frame = get_sigframe(ksig, sizeof(*frame));

        if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
                return -EFAULT;

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

        if (err)
                return -EFAULT;

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

        if (err)
                return -EFAULT;

        /*
         * Set up to return from user-space. If provided, use a stub
         * already located in user-space.
         */
        if (ksig->ka.sa.sa_flags & SA_RESTORER) {
                return_ip = (unsigned long)ksig->ka.sa.sa_restorer;
        } else {
                /* Trampoline - the desired return ip is in the signal return page. */
                return_ip = cris_signal_return_page;

                /*
                 * This is movu.w __NR_sigreturn, r9; break 13;
                 *
                 * WE DO NOT USE IT ANY MORE! It's only left here for historical
                 * reasons and because gdb uses it as a signature to notice
                 * signal handler stack frames.
                 */
                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)
                return -EFAULT;

        /*
         * Set up registers for signal handler.
         *
         * Where the code enters now.
         * Where the code enter later.
         * First argument, signo.
         */
        regs->erp = (unsigned long) ksig->ka.sa.sa_handler;
        regs->srp = return_ip;
        regs->r10 = ksig->sig;

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

        return 0;
}

static int
setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
{
        int err;
        unsigned long return_ip;
        struct rt_signal_frame __user *frame;

        err = 0;
        frame = get_sigframe(ksig, sizeof(*frame));

        if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
                return -EFAULT;

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

        if (err)
                return -EFAULT;

        /* 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));
        err |= __save_altstack(&frame->uc.uc_stack, rdusp());

        if (err)
                return -EFAULT;

        /*
         * Set up to return from user-space. If provided, use a stub
         * already located in user-space.
         */
        if (ksig->ka.sa.sa_flags & SA_RESTORER) {
                return_ip = (unsigned long) ksig->ka.sa.sa_restorer;
        } else {
                /* Trampoline - the desired return ip is in the signal return page. */
                return_ip = cris_signal_return_page + 6;

                /*
                 * This is movu.w __NR_rt_sigreturn, r9; break 13;
                 *
                 * WE DO NOT USE IT ANY MORE! It's only left here for historical
                 * reasons and because gdb uses it as a signature to notice
                 * signal handler stack frames.
                 */
                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)
                return -EFAULT;

        /*
         * Set up registers for signal handler.
         *
         * Where the code enters now.
         * Where the code enters later.
         * First argument is signo.
         * Second argument is (siginfo_t *).
         * Third argument is unused.
         */
        regs->erp = (unsigned long) ksig->ka.sa.sa_handler;
        regs->srp = return_ip;
        regs->r10 = ksig->sig;
        regs->r11 = (unsigned long) &frame->info;
        regs->r12 = 0;

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

        return 0;
}

/* Invoke a signal handler to, well, handle the signal. */
static inline void
handle_signal(int canrestart, struct ksignal *ksig, struct pt_regs *regs)
{
        sigset_t *oldset = sigmask_to_save();
        int ret;

        /* Check if this got called from a system call. */
        if (canrestart) {
                /* If so, check system call restarting. */
                switch (regs->r10) {
                        case -ERESTART_RESTARTBLOCK:
                        case -ERESTARTNOHAND:
                                /*
                                 * This means that the syscall should
                                 * only be restarted if there was no
                                 * handler for the signal, and since
                                 * this point isn't reached unless
                                 * there is a handler, there's no need
                                 * to restart.
                                 */
                                regs->r10 = -EINTR;
                                break;

                        case -ERESTARTSYS:
                                /*
                                 * This means restart the syscall if
                                 * there is no handler, or the handler
                                 * was registered with SA_RESTART.
                                 */
                                if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
                                        regs->r10 = -EINTR;
                                        break;
                                }

                                /* Fall through. */

                        case -ERESTARTNOINTR:
                                /*
                                 * This means that the syscall should
                                 * be called again after the signal
                                 * handler returns.
                                 */
                                RESTART_CRIS_SYS(regs);
                                break;
                }
        }

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

        signal_setup_done(ret, ksig, 0);
}

/*
 * 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)
{
        struct ksignal ksig;

        canrestart = canrestart && ((int)regs->exs >= 0);

        /*
         * The common case should go fast, which is why this point is
         * reached from kernel-mode. If that's the case, just return
         * without doing anything.
         */
        if (!user_mode(regs))
                return;

        if (get_signal(&ksig)) {
                /* Whee!  Actually deliver the signal.  */
                handle_signal(canrestart, &ksig, regs);
                return;
        }

        /* Got here 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->r9 = __NR_restart_syscall;
                        regs->erp -= 2;
                }
        }

        /* if there's no signal to deliver, we just put the saved sigmask
         * back */
        restore_saved_sigmask();
}

asmlinkage void
ugdb_trap_user(struct thread_info *ti, int sig)
{
        if (((user_regs(ti)->exs & 0xff00) >> 8) != SINGLE_STEP_INTR_VECT) {
                /* Zero single-step PC if the reason we stopped wasn't a single
                   step exception. This is to avoid relying on it when it isn't
                   reliable. */
                user_regs(ti)->spc = 0;
        }
        /* FIXME: Filter out false h/w breakpoint hits (i.e. EDA
           not within any configured h/w breakpoint range). Synchronize with
           what already exists for kernel debugging.  */
        if (((user_regs(ti)->exs & 0xff00) >> 8) == BREAK_8_INTR_VECT) {
                /* Break 8: subtract 2 from ERP unless in a delay slot. */
                if (!(user_regs(ti)->erp & 0x1))
                        user_regs(ti)->erp -= 2;
        }
        sys_kill(ti->task->pid, sig);
}

void
keep_debug_flags(unsigned long oldccs, unsigned long oldspc,
                 struct pt_regs *regs)
{
        if (oldccs & (1 << Q_CCS_BITNR)) {
                /* Pending single step due to single-stepping the break 13
                   in the signal trampoline: keep the Q flag. */
                regs->ccs |= (1 << Q_CCS_BITNR);
                /* S flag should be set - complain if it's not. */
                if (!(oldccs & (1 << (S_CCS_BITNR + CCS_SHIFT)))) {
                        printk("Q flag but no S flag?");
                }
                regs->ccs |= (1 << (S_CCS_BITNR + CCS_SHIFT));
                /* Assume the SPC is valid and interesting. */
                regs->spc = oldspc;

        } else if (oldccs & (1 << (S_CCS_BITNR + CCS_SHIFT))) {
                /* If a h/w bp was set in the signal handler we need
                   to keep the S flag. */
                regs->ccs |= (1 << (S_CCS_BITNR + CCS_SHIFT));
                /* Don't keep the old SPC though; if we got here due to
                   a single-step, the Q flag should have been set. */
        } else if (regs->spc) {
                /* If we were single-stepping *before* the signal was taken,
                   we don't want to restore that state now, because GDB will
                   have forgotten all about it. */
                regs->spc = 0;
                regs->ccs &= ~(1 << (S_CCS_BITNR + CCS_SHIFT));
        }
}

/* Set up the trampolines on the signal return page. */
int __init
cris_init_signal(void)
{
        u16* data = kmalloc(PAGE_SIZE, GFP_KERNEL);

        /* This is movu.w __NR_sigreturn, r9; break 13; */
        data[0] = 0x9c5f;
        data[1] = __NR_sigreturn;
        data[2] = 0xe93d;
        /* This is movu.w __NR_rt_sigreturn, r9; break 13; */
        data[3] = 0x9c5f;
        data[4] = __NR_rt_sigreturn;
        data[5] = 0xe93d;

        /* Map to userspace with appropriate permissions (no write access...) */
        cris_signal_return_page = (unsigned long)
          __ioremap_prot(virt_to_phys(data), PAGE_SIZE, PAGE_SIGNAL_TRAMPOLINE);

        return 0;
}

__initcall(cris_init_signal);