/*
 * Signal support for Hexagon processor
 *
 * Copyright (c) 2010-2012, The Linux Foundation. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 and
 * only version 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 */

#include <linux/linkage.h>
#include <linux/syscalls.h>
#include <linux/tracehook.h>
#include <linux/sched/task_stack.h>

#include <asm/registers.h>
#include <asm/thread_info.h>
#include <asm/unistd.h>
#include <linux/uaccess.h>
#include <asm/ucontext.h>
#include <asm/cacheflush.h>
#include <asm/signal.h>
#include <asm/vdso.h>

struct rt_sigframe {
        unsigned long tramp[2];
        struct siginfo info;
        struct ucontext uc;
};

static void __user *get_sigframe(struct ksignal *ksig, struct pt_regs *regs,
                          size_t frame_size)
{
        unsigned long sp = sigsp(regs->r29, ksig);

        return (void __user *)((sp - frame_size) & ~(sizeof(long long) - 1));
}

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

        err |= copy_to_user(&sc->sc_regs.r0, &regs->r00,
                            32*sizeof(unsigned long));

        err |= __put_user(regs->sa0, &sc->sc_regs.sa0);
        err |= __put_user(regs->lc0, &sc->sc_regs.lc0);
        err |= __put_user(regs->sa1, &sc->sc_regs.sa1);
        err |= __put_user(regs->lc1, &sc->sc_regs.lc1);
        err |= __put_user(regs->m0, &sc->sc_regs.m0);
        err |= __put_user(regs->m1, &sc->sc_regs.m1);
        err |= __put_user(regs->usr, &sc->sc_regs.usr);
        err |= __put_user(regs->preds, &sc->sc_regs.p3_0);
        err |= __put_user(regs->gp, &sc->sc_regs.gp);
        err |= __put_user(regs->ugp, &sc->sc_regs.ugp);
#if CONFIG_HEXAGON_ARCH_VERSION >= 4
        err |= __put_user(regs->cs0, &sc->sc_regs.cs0);
        err |= __put_user(regs->cs1, &sc->sc_regs.cs1);
#endif
        tmp = pt_elr(regs); err |= __put_user(tmp, &sc->sc_regs.pc);
        tmp = pt_cause(regs); err |= __put_user(tmp, &sc->sc_regs.cause);
        tmp = pt_badva(regs); err |= __put_user(tmp, &sc->sc_regs.badva);

        return err;
}

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

        err |= copy_from_user(&regs->r00, &sc->sc_regs.r0,
                              32 * sizeof(unsigned long));

        err |= __get_user(regs->sa0, &sc->sc_regs.sa0);
        err |= __get_user(regs->lc0, &sc->sc_regs.lc0);
        err |= __get_user(regs->sa1, &sc->sc_regs.sa1);
        err |= __get_user(regs->lc1, &sc->sc_regs.lc1);
        err |= __get_user(regs->m0, &sc->sc_regs.m0);
        err |= __get_user(regs->m1, &sc->sc_regs.m1);
        err |= __get_user(regs->usr, &sc->sc_regs.usr);
        err |= __get_user(regs->preds, &sc->sc_regs.p3_0);
        err |= __get_user(regs->gp, &sc->sc_regs.gp);
        err |= __get_user(regs->ugp, &sc->sc_regs.ugp);
#if CONFIG_HEXAGON_ARCH_VERSION >= 4
        err |= __get_user(regs->cs0, &sc->sc_regs.cs0);
        err |= __get_user(regs->cs1, &sc->sc_regs.cs1);
#endif
        err |= __get_user(tmp, &sc->sc_regs.pc); pt_set_elr(regs, tmp);

        return err;
}

/*
 * Setup signal stack frame with siginfo structure
 */
static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
                          struct pt_regs *regs)
{
        int err = 0;
        struct rt_sigframe __user *frame;
        struct hexagon_vdso *vdso = current->mm->context.vdso;

        frame = get_sigframe(ksig, regs, sizeof(struct rt_sigframe));

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

        if (copy_siginfo_to_user(&frame->info, &ksig->info))
                return -EFAULT;

        /* The on-stack signal trampoline is no longer executed;
         * however, the libgcc signal frame unwinding code checks for
         * the presence of these two numeric magic values.
         */
        err |= __put_user(0x7800d166, &frame->tramp[0]);
        err |= __put_user(0x5400c004, &frame->tramp[1]);
        err |= setup_sigcontext(regs, &frame->uc.uc_mcontext);
        err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
        err |= __save_altstack(&frame->uc.uc_stack, user_stack_pointer(regs));
        if (err)
                return -EFAULT;

        /* Load r0/r1 pair with signumber/siginfo pointer... */
        regs->r0100 = ((unsigned long long)((unsigned long)&frame->info) << 32)
                | (unsigned long long)ksig->sig;
        regs->r02 = (unsigned long) &frame->uc;
        regs->r31 = (unsigned long) vdso->rt_signal_trampoline;
        pt_psp(regs) = (unsigned long) frame;
        pt_set_elr(regs, (unsigned long)ksig->ka.sa.sa_handler);

        return 0;
}

/*
 * Setup invocation of signal handler
 */
static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
{
        int ret;

        /*
         * If we're handling a signal that aborted a system call,
         * set up the error return value before adding the signal
         * frame to the stack.
         */

        if (regs->syscall_nr >= 0) {
                switch (regs->r00) {
                case -ERESTART_RESTARTBLOCK:
                case -ERESTARTNOHAND:
                        regs->r00 = -EINTR;
                        break;
                case -ERESTARTSYS:
                        if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
                                regs->r00 = -EINTR;
                                break;
                        }
                        /* Fall through */
                case -ERESTARTNOINTR:
                        regs->r06 = regs->syscall_nr;
                        pt_set_elr(regs, pt_elr(regs) - 4);
                        regs->r00 = regs->restart_r0;
                        break;
                default:
                        break;
                }
        }

        /*
         * Set up the stack frame; not doing the SA_SIGINFO thing.  We
         * only set up the rt_frame flavor.
         */
        /* If there was an error on setup, no signal was delivered. */
        ret = setup_rt_frame(ksig, sigmask_to_save(), regs);

        signal_setup_done(ret, ksig, test_thread_flag(TIF_SINGLESTEP));
}

/*
 * Called from return-from-event code.
 */
void do_signal(struct pt_regs *regs)
{
        struct ksignal ksig;

        if (!user_mode(regs))
                return;

        if (get_signal(&ksig)) {
                handle_signal(&ksig, regs);
                return;
        }

        /*
         * No (more) signals; if we came from a system call, handle the restart.
         */

        if (regs->syscall_nr >= 0) {
                switch (regs->r00) {
                case -ERESTARTNOHAND:
                case -ERESTARTSYS:
                case -ERESTARTNOINTR:
                        regs->r06 = regs->syscall_nr;
                        break;
                case -ERESTART_RESTARTBLOCK:
                        regs->r06 = __NR_restart_syscall;
                        break;
                default:
                        goto no_restart;
                }
                pt_set_elr(regs, pt_elr(regs) - 4);
                regs->r00 = regs->restart_r0;
        }

no_restart:
        /* If there's no signal to deliver, put the saved sigmask back */
        restore_saved_sigmask();
}

/*
 * Architecture-specific wrappers for signal-related system calls
 */

asmlinkage int sys_rt_sigreturn(void)
{
        struct pt_regs *regs = current_pt_regs();
        struct rt_sigframe __user *frame;
        sigset_t blocked;

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

        frame = (struct rt_sigframe __user *)pt_psp(regs);
        if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
                goto badframe;
        if (__copy_from_user(&blocked, &frame->uc.uc_sigmask, sizeof(blocked)))
                goto badframe;

        set_current_blocked(&blocked);

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

        /* Restore the user's stack as well */
        pt_psp(regs) = regs->r29;

        regs->syscall_nr = -1;

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

        return regs->r00;

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