/*
 * OpenRISC signal.c
 *
 * Linux architectural port borrowing liberally from similar works of
 * others.  All original copyrights apply as per the original source
 * declaration.
 *
 * Modifications for the OpenRISC architecture:
 * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
 * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
 *
 *      This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or (at your option) any later version.
 */

#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 <linux/tracehook.h>

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

#define DEBUG_SIG 0

asmlinkage long
_sys_sigaltstack(const stack_t *uss, stack_t *uoss, struct pt_regs *regs)
{
        return do_sigaltstack(uss, uoss, regs->sp);
}

struct rt_sigframe {
        struct siginfo *pinfo;
        void *puc;
        struct siginfo info;
        struct ucontext uc;
        unsigned char retcode[16];      /* trampoline code */
};

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

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

        /*
         * Restore the regs from &sc->regs.
         * (sc is already checked for VERIFY_READ since the sigframe was
         *  checked in sys_sigreturn previously)
         */
        if (__copy_from_user(regs, sc->regs.gpr, 32 * sizeof(unsigned long)))
                goto badframe;
        if (__copy_from_user(&regs->pc, &sc->regs.pc, sizeof(unsigned long)))
                goto badframe;
        if (__copy_from_user(&regs->sr, &sc->regs.sr, sizeof(unsigned long)))
                goto badframe;

        /* make sure the SM-bit is cleared so user-mode cannot fool us */
        regs->sr &= ~SPR_SR_SM;

        /* 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;
}

asmlinkage long _sys_rt_sigreturn(struct pt_regs *regs)
{
        struct rt_sigframe *frame = (struct rt_sigframe __user *)regs->sp;
        sigset_t set;
        stack_t st;

        /*
         * 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;

        set_current_blocked(&set);

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

        if (__copy_from_user(&st, &frame->uc.uc_stack, sizeof(st)))
                goto badframe;
        /* It is more difficult to avoid calling this function than to
           call it and ignore errors.  */
        do_sigaltstack(&st, NULL, regs->sp);

        return regs->gpr[11];

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

/*
 * Set up a signal frame.
 */

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

        /* copy the regs */

        err |= __copy_to_user(sc->regs.gpr, regs, 32 * sizeof(unsigned long));
        err |= __copy_to_user(&sc->regs.pc, &regs->pc, sizeof(unsigned long));
        err |= __copy_to_user(&sc->regs.sr, &regs->sr, sizeof(unsigned long));

        /* then some other stuff */

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

        return err;
}

static inline unsigned long align_sigframe(unsigned long sp)
{
        return sp & ~3UL;
}

/*
 * Work out where the signal frame should go.  It's either on the user stack
 * or the alternate stack.
 */

static inline void __user *get_sigframe(struct k_sigaction *ka,
                                        struct pt_regs *regs, size_t frame_size)
{
        unsigned long sp = regs->sp;
        int onsigstack = on_sig_stack(sp);

        /* redzone */
        sp -= STACK_FRAME_OVERHEAD;

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

        sp = align_sigframe(sp - frame_size);

        /*
         * If we are on the alternate signal stack and would overflow it, don't.
         * Return an always-bogus address instead so we will die with SIGSEGV.
         */
        if (onsigstack && !likely(on_sig_stack(sp)))
                return (void __user *)-1L;

        return (void __user *)sp;
}

/* 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_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
                          sigset_t *set, struct pt_regs *regs)
{
        struct rt_sigframe *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);

        if (ka->sa.sa_flags & SA_SIGINFO)
                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 |= __put_user(0, &frame->uc.uc_flags);
        err |= __put_user(NULL, &frame->uc.uc_link);
        err |= __put_user((void *)current->sas_ss_sp,
                          &frame->uc.uc_stack.ss_sp);
        err |= __put_user(sas_ss_flags(regs->sp), &frame->uc.uc_stack.ss_flags);
        err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
        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;

        /* trampoline - the desired return ip is the retcode itself */
        return_ip = (unsigned long)&frame->retcode;
        /* This is l.ori r11,r0,__NR_sigreturn, l.sys 1 */
        err |= __put_user(0xa960, (short *)(frame->retcode + 0));
        err |= __put_user(__NR_rt_sigreturn, (short *)(frame->retcode + 2));
        err |= __put_user(0x20000001, (unsigned long *)(frame->retcode + 4));
        err |= __put_user(0x15000000, (unsigned long *)(frame->retcode + 8));

        if (err)
                goto give_sigsegv;

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

        /* Set up registers for signal handler */
        regs->pc = (unsigned long)ka->sa.sa_handler; /* what we enter NOW */
        regs->gpr[9] = (unsigned long)return_ip;     /* what we enter LATER */
        regs->gpr[3] = (unsigned long)sig;           /* arg 1: signo */
        regs->gpr[4] = (unsigned long)&frame->info;  /* arg 2: (siginfo_t*) */
        regs->gpr[5] = (unsigned long)&frame->uc;    /* arg 3: ucontext */

        /* actually move the usp to reflect the stacked frame */
        regs->sp = (unsigned long)frame;

        return 0;

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

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

        ret = setup_rt_frame(sig, ka, info, sigmask_to_save(), regs);
        if (ret)
                return;

        signal_delivered(sig, info, ka, regs,
                                 test_thread_flag(TIF_SINGLESTEP));
}

/*
 * 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(struct pt_regs *regs)
{
        siginfo_t info;
        int signr;
        struct k_sigaction ka;

        /*
         * 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;

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

        /* If we are coming out of a syscall then we need
         * to check if the syscall was interrupted and wants to be
         * restarted after handling the signal.  If so, the original
         * syscall number is put back into r11 and the PC rewound to
         * point at the l.sys instruction that resulted in the
         * original syscall.  Syscall results other than the four
         * below mean that the syscall executed to completion and no
         * restart is necessary.
         */
        if (regs->orig_gpr11) {
                int restart = 0;

                switch (regs->gpr[11]) {
                case -ERESTART_RESTARTBLOCK:
                case -ERESTARTNOHAND:
                        /* Restart if there is no signal handler */
                        restart = (signr <= 0);
                        break;
                case -ERESTARTSYS:
                        /* Restart if there no signal handler or
                         * SA_RESTART flag is set */
                        restart = (signr <= 0 || (ka.sa.sa_flags & SA_RESTART));
                        break;
                case -ERESTARTNOINTR:
                        /* Always restart */
                        restart = 1;
                        break;
                }

                if (restart) {
                        if (regs->gpr[11] == -ERESTART_RESTARTBLOCK)
                                regs->gpr[11] = __NR_restart_syscall;
                        else
                                regs->gpr[11] = regs->orig_gpr11;
                        regs->pc -= 4;
                } else {
                        regs->gpr[11] = -EINTR;
                }
        }

        if (signr <= 0) {
                /* no signal to deliver so we just put the saved sigmask
                 * back */
                restore_saved_sigmask();
        } else {                /* signr > 0 */
                /* Whee!  Actually deliver the signal.  */
                handle_signal(signr, &info, &ka, regs);
        }

        return;
}

asmlinkage void do_notify_resume(struct pt_regs *regs)
{
        if (current_thread_info()->flags & _TIF_SIGPENDING)
                do_signal(regs);

        if (current_thread_info()->flags & _TIF_NOTIFY_RESUME) {
                clear_thread_flag(TIF_NOTIFY_RESUME);
                tracehook_notify_resume(regs);
        }
}