/*
 * Copyright (C) 2013-2014 Altera Corporation
 * Copyright (C) 2011-2012 Tobias Klauser <tklauser@distanz.ch>
 * Copyright (C) 2004 Microtronix Datacom Ltd
 * Copyright (C) 1991, 1992 Linus Torvalds
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file COPYING in the main directory of this archive
 * for more details.
 */

#include <linux/signal.h>
#include <linux/errno.h>
#include <linux/ptrace.h>
#include <linux/uaccess.h>
#include <linux/unistd.h>
#include <linux/personality.h>
#include <linux/resume_user_mode.h>

#include <asm/ucontext.h>
#include <asm/cacheflush.h>

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

/*
 * Do a signal return; undo the signal stack.
 *
 * Keep the return code on the stack quadword aligned!
 * That makes the cache flush below easier.
 */

struct rt_sigframe {
        struct siginfo info;
        struct ucontext uc;
};

static inline int rt_restore_ucontext(struct pt_regs *regs,
                                        struct switch_stack *sw,
                                        struct ucontext __user *uc, int *pr2)
{
        int temp;
        unsigned long __user *gregs = uc->uc_mcontext.gregs;
        int err;

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

        err = __get_user(temp, &uc->uc_mcontext.version);
        if (temp != MCONTEXT_VERSION)
                goto badframe;
        /* restore passed registers */
        err |= __get_user(regs->r1, &gregs[0]);
        err |= __get_user(regs->r2, &gregs[1]);
        err |= __get_user(regs->r3, &gregs[2]);
        err |= __get_user(regs->r4, &gregs[3]);
        err |= __get_user(regs->r5, &gregs[4]);
        err |= __get_user(regs->r6, &gregs[5]);
        err |= __get_user(regs->r7, &gregs[6]);
        err |= __get_user(regs->r8, &gregs[7]);
        err |= __get_user(regs->r9, &gregs[8]);
        err |= __get_user(regs->r10, &gregs[9]);
        err |= __get_user(regs->r11, &gregs[10]);
        err |= __get_user(regs->r12, &gregs[11]);
        err |= __get_user(regs->r13, &gregs[12]);
        err |= __get_user(regs->r14, &gregs[13]);
        err |= __get_user(regs->r15, &gregs[14]);
        err |= __get_user(sw->r16, &gregs[15]);
        err |= __get_user(sw->r17, &gregs[16]);
        err |= __get_user(sw->r18, &gregs[17]);
        err |= __get_user(sw->r19, &gregs[18]);
        err |= __get_user(sw->r20, &gregs[19]);
        err |= __get_user(sw->r21, &gregs[20]);
        err |= __get_user(sw->r22, &gregs[21]);
        err |= __get_user(sw->r23, &gregs[22]);
        /* gregs[23] is handled below */
        err |= __get_user(sw->fp, &gregs[24]);  /* Verify, should this be
                                                        settable */
        err |= __get_user(sw->gp, &gregs[25]);  /* Verify, should this be
                                                        settable */

        err |= __get_user(temp, &gregs[26]);  /* Not really necessary no user
                                                        settable bits */
        err |= __get_user(regs->ea, &gregs[27]);

        err |= __get_user(regs->ra, &gregs[23]);
        err |= __get_user(regs->sp, &gregs[28]);

        regs->orig_r2 = -1;             /* disable syscall checks */

        err |= restore_altstack(&uc->uc_stack);
        if (err)
                goto badframe;

        *pr2 = regs->r2;
        return err;

badframe:
        return 1;
}

asmlinkage int do_rt_sigreturn(struct switch_stack *sw)
{
        struct pt_regs *regs = (struct pt_regs *)(sw + 1);
        /* Verify, can we follow the stack back */
        struct rt_sigframe __user *frame;
        sigset_t set;
        int rval;

        frame = (struct rt_sigframe __user *) regs->sp;
        if (!access_ok(frame, sizeof(*frame)))
                goto badframe;

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

        set_current_blocked(&set);

        if (rt_restore_ucontext(regs, sw, &frame->uc, &rval))
                goto badframe;

        return rval;

badframe:
        force_sig(SIGSEGV);
        return 0;
}

static inline int rt_setup_ucontext(struct ucontext __user *uc, struct pt_regs *regs)
{
        struct switch_stack *sw = (struct switch_stack *)regs - 1;
        unsigned long __user *gregs = uc->uc_mcontext.gregs;
        int err = 0;

        err |= __put_user(MCONTEXT_VERSION, &uc->uc_mcontext.version);
        err |= __put_user(regs->r1, &gregs[0]);
        err |= __put_user(regs->r2, &gregs[1]);
        err |= __put_user(regs->r3, &gregs[2]);
        err |= __put_user(regs->r4, &gregs[3]);
        err |= __put_user(regs->r5, &gregs[4]);
        err |= __put_user(regs->r6, &gregs[5]);
        err |= __put_user(regs->r7, &gregs[6]);
        err |= __put_user(regs->r8, &gregs[7]);
        err |= __put_user(regs->r9, &gregs[8]);
        err |= __put_user(regs->r10, &gregs[9]);
        err |= __put_user(regs->r11, &gregs[10]);
        err |= __put_user(regs->r12, &gregs[11]);
        err |= __put_user(regs->r13, &gregs[12]);
        err |= __put_user(regs->r14, &gregs[13]);
        err |= __put_user(regs->r15, &gregs[14]);
        err |= __put_user(sw->r16, &gregs[15]);
        err |= __put_user(sw->r17, &gregs[16]);
        err |= __put_user(sw->r18, &gregs[17]);
        err |= __put_user(sw->r19, &gregs[18]);
        err |= __put_user(sw->r20, &gregs[19]);
        err |= __put_user(sw->r21, &gregs[20]);
        err |= __put_user(sw->r22, &gregs[21]);
        err |= __put_user(sw->r23, &gregs[22]);
        err |= __put_user(regs->ra, &gregs[23]);
        err |= __put_user(sw->fp, &gregs[24]);
        err |= __put_user(sw->gp, &gregs[25]);
        err |= __put_user(regs->ea, &gregs[27]);
        err |= __put_user(regs->sp, &gregs[28]);
        return err;
}

static inline void __user *get_sigframe(struct ksignal *ksig,
                                        struct pt_regs *regs,
                                        size_t frame_size)
{
        unsigned long usp;

        /* Default to using normal stack.  */
        usp = regs->sp;

        /* This is the X/Open sanctioned signal stack switching.  */
        usp = sigsp(usp, ksig);

        /* Verify, is it 32 or 64 bit aligned */
        return (void __user *)((usp - frame_size) & -8UL);
}

static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
                          struct pt_regs *regs)
{
        struct rt_sigframe __user *frame;
        int err = 0;

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

        if (ksig->ka.sa.sa_flags & SA_SIGINFO)
                err |= copy_siginfo_to_user(&frame->info, &ksig->info);

        /* Create the ucontext.  */
        err |= __put_user(0, &frame->uc.uc_flags);
        err |= __put_user(0, &frame->uc.uc_link);
        err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
        err |= rt_setup_ucontext(&frame->uc, regs);
        err |= copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));

        if (err)
                goto give_sigsegv;

        /* Set up to return from userspace; jump to fixed address sigreturn
           trampoline on kuser page.  */
        regs->ra = (unsigned long) (0x1044);

        /* Set up registers for signal handler */
        regs->sp = (unsigned long) frame;
        regs->r4 = (unsigned long) ksig->sig;
        regs->r5 = (unsigned long) &frame->info;
        regs->r6 = (unsigned long) &frame->uc;
        regs->ea = (unsigned long) ksig->ka.sa.sa_handler;
        return 0;

give_sigsegv:
        force_sigsegv(ksig->sig);
        return -EFAULT;
}

/*
 * OK, we're invoking a handler
 */
static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
{
        int ret;
        sigset_t *oldset = sigmask_to_save();

        /* set up the stack frame */
        ret = setup_rt_frame(ksig, oldset, regs);

        signal_setup_done(ret, ksig, 0);
}

static int do_signal(struct pt_regs *regs)
{
        unsigned int retval = 0, continue_addr = 0, restart_addr = 0;
        int restart = 0;
        struct ksignal ksig;

        current->thread.kregs = regs;

        /*
         * If we were from a system call, check for system call restarting...
         */
        if (regs->orig_r2 >= 0 && regs->r1) {
                continue_addr = regs->ea;
                restart_addr = continue_addr - 4;
                retval = regs->r2;

                /*
                 * Prepare for system call restart. We do this here so that a
                 * debugger will see the already changed PC.
                 */
                switch (retval) {
                case ERESTART_RESTARTBLOCK:
                        restart = -2;
                        fallthrough;
                case ERESTARTNOHAND:
                case ERESTARTSYS:
                case ERESTARTNOINTR:
                        restart++;
                        regs->r2 = regs->orig_r2;
                        regs->r7 = regs->orig_r7;
                        regs->ea = restart_addr;
                        break;
                }
                regs->orig_r2 = -1;
        }

        if (get_signal(&ksig)) {
                /* handler */
                if (unlikely(restart && regs->ea == restart_addr)) {
                        if (retval == ERESTARTNOHAND ||
                            retval == ERESTART_RESTARTBLOCK ||
                             (retval == ERESTARTSYS
                                && !(ksig.ka.sa.sa_flags & SA_RESTART))) {
                                regs->r2 = EINTR;
                                regs->r7 = 1;
                                regs->ea = continue_addr;
                        }
                }
                handle_signal(&ksig, regs);
                return 0;
        }

        /*
         * No handler present
         */
        if (unlikely(restart) && regs->ea == restart_addr) {
                regs->ea = continue_addr;
                regs->r2 = __NR_restart_syscall;
        }

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

        return restart;
}

asmlinkage int do_notify_resume(struct pt_regs *regs)
{
        /*
         * 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 0;

        if (test_thread_flag(TIF_SIGPENDING) ||
            test_thread_flag(TIF_NOTIFY_SIGNAL)) {
                int restart = do_signal(regs);

                if (unlikely(restart)) {
                        /*
                         * Restart without handlers.
                         * Deal with it without leaving
                         * the kernel space.
                         */
                        return restart;
                }
        } else if (test_thread_flag(TIF_NOTIFY_RESUME))
                resume_user_mode_work(regs);

        return 0;
}