/*
 * 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.
 *
 * Copyright (C) 1991, 1992  Linus Torvalds
 * Copyright (C) 1994 - 2000  Ralf Baechle
 * Copyright (C) 1999, 2000 Silicon Graphics, Inc.
 * Copyright (C) 2014, Imagination Technologies Ltd.
 */
#include <linux/cache.h>
#include <linux/context_tracking.h>
#include <linux/irqflags.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/personality.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/uprobes.h>
#include <linux/compiler.h>
#include <linux/syscalls.h>
#include <linux/uaccess.h>
#include <linux/tracehook.h>

#include <asm/abi.h>
#include <asm/asm.h>
#include <linux/bitops.h>
#include <asm/cacheflush.h>
#include <asm/fpu.h>
#include <asm/sim.h>
#include <asm/ucontext.h>
#include <asm/cpu-features.h>
#include <asm/war.h>
#include <asm/dsp.h>
#include <asm/inst.h>
#include <asm/msa.h>

#include "signal-common.h"

static int (*save_fp_context)(void __user *sc);
static int (*restore_fp_context)(void __user *sc);

struct sigframe {
        u32 sf_ass[4];          /* argument save space for o32 */
        u32 sf_pad[2];          /* Was: signal trampoline */

        /* Matches struct ucontext from its uc_mcontext field onwards */
        struct sigcontext sf_sc;
        sigset_t sf_mask;
        unsigned long long sf_extcontext[0];
};

struct rt_sigframe {
        u32 rs_ass[4];          /* argument save space for o32 */
        u32 rs_pad[2];          /* Was: signal trampoline */
        struct siginfo rs_info;
        struct ucontext rs_uc;
};

#ifdef CONFIG_MIPS_FP_SUPPORT

/*
 * Thread saved context copy to/from a signal context presumed to be on the
 * user stack, and therefore accessed with appropriate macros from uaccess.h.
 */
static int copy_fp_to_sigcontext(void __user *sc)
{
        struct mips_abi *abi = current->thread.abi;
        uint64_t __user *fpregs = sc + abi->off_sc_fpregs;
        uint32_t __user *csr = sc + abi->off_sc_fpc_csr;
        int i;
        int err = 0;
        int inc = test_thread_flag(TIF_32BIT_FPREGS) ? 2 : 1;

        for (i = 0; i < NUM_FPU_REGS; i += inc) {
                err |=
                    __put_user(get_fpr64(&current->thread.fpu.fpr[i], 0),
                               &fpregs[i]);
        }
        err |= __put_user(current->thread.fpu.fcr31, csr);

        return err;
}

static int copy_fp_from_sigcontext(void __user *sc)
{
        struct mips_abi *abi = current->thread.abi;
        uint64_t __user *fpregs = sc + abi->off_sc_fpregs;
        uint32_t __user *csr = sc + abi->off_sc_fpc_csr;
        int i;
        int err = 0;
        int inc = test_thread_flag(TIF_32BIT_FPREGS) ? 2 : 1;
        u64 fpr_val;

        for (i = 0; i < NUM_FPU_REGS; i += inc) {
                err |= __get_user(fpr_val, &fpregs[i]);
                set_fpr64(&current->thread.fpu.fpr[i], 0, fpr_val);
        }
        err |= __get_user(current->thread.fpu.fcr31, csr);

        return err;
}

#else /* !CONFIG_MIPS_FP_SUPPORT */

static int copy_fp_to_sigcontext(void __user *sc)
{
        return 0;
}

static int copy_fp_from_sigcontext(void __user *sc)
{
        return 0;
}

#endif /* !CONFIG_MIPS_FP_SUPPORT */

/*
 * Wrappers for the assembly _{save,restore}_fp_context functions.
 */
static int save_hw_fp_context(void __user *sc)
{
        struct mips_abi *abi = current->thread.abi;
        uint64_t __user *fpregs = sc + abi->off_sc_fpregs;
        uint32_t __user *csr = sc + abi->off_sc_fpc_csr;

        return _save_fp_context(fpregs, csr);
}

static int restore_hw_fp_context(void __user *sc)
{
        struct mips_abi *abi = current->thread.abi;
        uint64_t __user *fpregs = sc + abi->off_sc_fpregs;
        uint32_t __user *csr = sc + abi->off_sc_fpc_csr;

        return _restore_fp_context(fpregs, csr);
}

/*
 * Extended context handling.
 */

static inline void __user *sc_to_extcontext(void __user *sc)
{
        struct ucontext __user *uc;

        /*
         * We can just pretend the sigcontext is always embedded in a struct
         * ucontext here, because the offset from sigcontext to extended
         * context is the same in the struct sigframe case.
         */
        uc = container_of(sc, struct ucontext, uc_mcontext);
        return &uc->uc_extcontext;
}

#ifdef CONFIG_CPU_HAS_MSA

static int save_msa_extcontext(void __user *buf)
{
        struct msa_extcontext __user *msa = buf;
        uint64_t val;
        int i, err;

        if (!thread_msa_context_live())
                return 0;

        /*
         * Ensure that we can't lose the live MSA context between checking
         * for it & writing it to memory.
         */
        preempt_disable();

        if (is_msa_enabled()) {
                /*
                 * There are no EVA versions of the vector register load/store
                 * instructions, so MSA context has to be saved to kernel memory
                 * and then copied to user memory. The save to kernel memory
                 * should already have been done when handling scalar FP
                 * context.
                 */
                BUG_ON(IS_ENABLED(CONFIG_EVA));

                err = __put_user(read_msa_csr(), &msa->csr);
                err |= _save_msa_all_upper(&msa->wr);

                preempt_enable();
        } else {
                preempt_enable();

                err = __put_user(current->thread.fpu.msacsr, &msa->csr);

                for (i = 0; i < NUM_FPU_REGS; i++) {
                        val = get_fpr64(&current->thread.fpu.fpr[i], 1);
                        err |= __put_user(val, &msa->wr[i]);
                }
        }

        err |= __put_user(MSA_EXTCONTEXT_MAGIC, &msa->ext.magic);
        err |= __put_user(sizeof(*msa), &msa->ext.size);

        return err ? -EFAULT : sizeof(*msa);
}

static int restore_msa_extcontext(void __user *buf, unsigned int size)
{
        struct msa_extcontext __user *msa = buf;
        unsigned long long val;
        unsigned int csr;
        int i, err;

        if (size != sizeof(*msa))
                return -EINVAL;

        err = get_user(csr, &msa->csr);
        if (err)
                return err;

        preempt_disable();

        if (is_msa_enabled()) {
                /*
                 * There are no EVA versions of the vector register load/store
                 * instructions, so MSA context has to be copied to kernel
                 * memory and later loaded to registers. The same is true of
                 * scalar FP context, so FPU & MSA should have already been
                 * disabled whilst handling scalar FP context.
                 */
                BUG_ON(IS_ENABLED(CONFIG_EVA));

                write_msa_csr(csr);
                err |= _restore_msa_all_upper(&msa->wr);
                preempt_enable();
        } else {
                preempt_enable();

                current->thread.fpu.msacsr = csr;

                for (i = 0; i < NUM_FPU_REGS; i++) {
                        err |= __get_user(val, &msa->wr[i]);
                        set_fpr64(&current->thread.fpu.fpr[i], 1, val);
                }
        }

        return err;
}

#else /* !CONFIG_CPU_HAS_MSA */

static int save_msa_extcontext(void __user *buf)
{
        return 0;
}

static int restore_msa_extcontext(void __user *buf, unsigned int size)
{
        return SIGSYS;
}

#endif /* !CONFIG_CPU_HAS_MSA */

static int save_extcontext(void __user *buf)
{
        int sz;

        sz = save_msa_extcontext(buf);
        if (sz < 0)
                return sz;
        buf += sz;

        /* If no context was saved then trivially return */
        if (!sz)
                return 0;

        /* Write the end marker */
        if (__put_user(END_EXTCONTEXT_MAGIC, (u32 *)buf))
                return -EFAULT;

        sz += sizeof(((struct extcontext *)NULL)->magic);
        return sz;
}

static int restore_extcontext(void __user *buf)
{
        struct extcontext ext;
        int err;

        while (1) {
                err = __get_user(ext.magic, (unsigned int *)buf);
                if (err)
                        return err;

                if (ext.magic == END_EXTCONTEXT_MAGIC)
                        return 0;

                err = __get_user(ext.size, (unsigned int *)(buf
                        + offsetof(struct extcontext, size)));
                if (err)
                        return err;

                switch (ext.magic) {
                case MSA_EXTCONTEXT_MAGIC:
                        err = restore_msa_extcontext(buf, ext.size);
                        break;

                default:
                        err = -EINVAL;
                        break;
                }

                if (err)
                        return err;

                buf += ext.size;
        }
}

/*
 * Helper routines
 */
int protected_save_fp_context(void __user *sc)
{
        struct mips_abi *abi = current->thread.abi;
        uint64_t __user *fpregs = sc + abi->off_sc_fpregs;
        uint32_t __user *csr = sc + abi->off_sc_fpc_csr;
        uint32_t __user *used_math = sc + abi->off_sc_used_math;
        unsigned int used, ext_sz;
        int err;

        used = used_math() ? USED_FP : 0;
        if (!used)
                goto fp_done;

        if (!test_thread_flag(TIF_32BIT_FPREGS))
                used |= USED_FR1;
        if (test_thread_flag(TIF_HYBRID_FPREGS))
                used |= USED_HYBRID_FPRS;

        /*
         * EVA does not have userland equivalents of ldc1 or sdc1, so
         * save to the kernel FP context & copy that to userland below.
         */
        if (IS_ENABLED(CONFIG_EVA))
                lose_fpu(1);

        while (1) {
                lock_fpu_owner();
                if (is_fpu_owner()) {
                        err = save_fp_context(sc);
                        unlock_fpu_owner();
                } else {
                        unlock_fpu_owner();
                        err = copy_fp_to_sigcontext(sc);
                }
                if (likely(!err))
                        break;
                /* touch the sigcontext and try again */
                err = __put_user(0, &fpregs[0]) |
                        __put_user(0, &fpregs[31]) |
                        __put_user(0, csr);
                if (err)
                        return err;     /* really bad sigcontext */
        }

fp_done:
        ext_sz = err = save_extcontext(sc_to_extcontext(sc));
        if (err < 0)
                return err;
        used |= ext_sz ? USED_EXTCONTEXT : 0;

        return __put_user(used, used_math);
}

int protected_restore_fp_context(void __user *sc)
{
        struct mips_abi *abi = current->thread.abi;
        uint64_t __user *fpregs = sc + abi->off_sc_fpregs;
        uint32_t __user *csr = sc + abi->off_sc_fpc_csr;
        uint32_t __user *used_math = sc + abi->off_sc_used_math;
        unsigned int used;
        int err, sig = 0, tmp __maybe_unused;

        err = __get_user(used, used_math);
        conditional_used_math(used & USED_FP);

        /*
         * The signal handler may have used FPU; give it up if the program
         * doesn't want it following sigreturn.
         */
        if (err || !(used & USED_FP))
                lose_fpu(0);
        if (err)
                return err;
        if (!(used & USED_FP))
                goto fp_done;

        err = sig = fpcsr_pending(csr);
        if (err < 0)
                return err;

        /*
         * EVA does not have userland equivalents of ldc1 or sdc1, so we
         * disable the FPU here such that the code below simply copies to
         * the kernel FP context.
         */
        if (IS_ENABLED(CONFIG_EVA))
                lose_fpu(0);

        while (1) {
                lock_fpu_owner();
                if (is_fpu_owner()) {
                        err = restore_fp_context(sc);
                        unlock_fpu_owner();
                } else {
                        unlock_fpu_owner();
                        err = copy_fp_from_sigcontext(sc);
                }
                if (likely(!err))
                        break;
                /* touch the sigcontext and try again */
                err = __get_user(tmp, &fpregs[0]) |
                        __get_user(tmp, &fpregs[31]) |
                        __get_user(tmp, csr);
                if (err)
                        break;  /* really bad sigcontext */
        }

fp_done:
        if (!err && (used & USED_EXTCONTEXT))
                err = restore_extcontext(sc_to_extcontext(sc));

        return err ?: sig;
}

int setup_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
{
        int err = 0;
        int i;

        err |= __put_user(regs->cp0_epc, &sc->sc_pc);

        err |= __put_user(0, &sc->sc_regs[0]);
        for (i = 1; i < 32; i++)
                err |= __put_user(regs->regs[i], &sc->sc_regs[i]);

#ifdef CONFIG_CPU_HAS_SMARTMIPS
        err |= __put_user(regs->acx, &sc->sc_acx);
#endif
        err |= __put_user(regs->hi, &sc->sc_mdhi);
        err |= __put_user(regs->lo, &sc->sc_mdlo);
        if (cpu_has_dsp) {
                err |= __put_user(mfhi1(), &sc->sc_hi1);
                err |= __put_user(mflo1(), &sc->sc_lo1);
                err |= __put_user(mfhi2(), &sc->sc_hi2);
                err |= __put_user(mflo2(), &sc->sc_lo2);
                err |= __put_user(mfhi3(), &sc->sc_hi3);
                err |= __put_user(mflo3(), &sc->sc_lo3);
                err |= __put_user(rddsp(DSP_MASK), &sc->sc_dsp);
        }


        /*
         * Save FPU state to signal context. Signal handler
         * will "inherit" current FPU state.
         */
        err |= protected_save_fp_context(sc);

        return err;
}

static size_t extcontext_max_size(void)
{
        size_t sz = 0;

        /*
         * The assumption here is that between this point & the point at which
         * the extended context is saved the size of the context should only
         * ever be able to shrink (if the task is preempted), but never grow.
         * That is, what this function returns is an upper bound on the size of
         * the extended context for the current task at the current time.
         */

        if (thread_msa_context_live())
                sz += sizeof(struct msa_extcontext);

        /* If any context is saved then we'll append the end marker */
        if (sz)
                sz += sizeof(((struct extcontext *)NULL)->magic);

        return sz;
}

int fpcsr_pending(unsigned int __user *fpcsr)
{
        int err, sig = 0;
        unsigned int csr, enabled;

        err = __get_user(csr, fpcsr);
        enabled = FPU_CSR_UNI_X | ((csr & FPU_CSR_ALL_E) << 5);
        /*
         * If the signal handler set some FPU exceptions, clear it and
         * send SIGFPE.
         */
        if (csr & enabled) {
                csr &= ~enabled;
                err |= __put_user(csr, fpcsr);
                sig = SIGFPE;
        }
        return err ?: sig;
}

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

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

        err |= __get_user(regs->cp0_epc, &sc->sc_pc);

#ifdef CONFIG_CPU_HAS_SMARTMIPS
        err |= __get_user(regs->acx, &sc->sc_acx);
#endif
        err |= __get_user(regs->hi, &sc->sc_mdhi);
        err |= __get_user(regs->lo, &sc->sc_mdlo);
        if (cpu_has_dsp) {
                err |= __get_user(treg, &sc->sc_hi1); mthi1(treg);
                err |= __get_user(treg, &sc->sc_lo1); mtlo1(treg);
                err |= __get_user(treg, &sc->sc_hi2); mthi2(treg);
                err |= __get_user(treg, &sc->sc_lo2); mtlo2(treg);
                err |= __get_user(treg, &sc->sc_hi3); mthi3(treg);
                err |= __get_user(treg, &sc->sc_lo3); mtlo3(treg);
                err |= __get_user(treg, &sc->sc_dsp); wrdsp(treg, DSP_MASK);
        }

        for (i = 1; i < 32; i++)
                err |= __get_user(regs->regs[i], &sc->sc_regs[i]);

        return err ?: protected_restore_fp_context(sc);
}

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

        /* Leave space for potential extended context */
        frame_size += extcontext_max_size();

        /* Default to using normal stack */
        sp = regs->regs[29];

        /*
         * FPU emulator may have it's own trampoline active just
         * above the user stack, 16-bytes before the next lowest
         * 16 byte boundary.  Try to avoid trashing it.
         */
        sp -= 32;

        sp = sigsp(sp, ksig);

        return (void __user *)((sp - frame_size) & (ICACHE_REFILLS_WORKAROUND_WAR ? ~(cpu_icache_line_size()-1) : ALMASK));
}

/*
 * Atomically swap in the new signal mask, and wait for a signal.
 */

#ifdef CONFIG_TRAD_SIGNALS
SYSCALL_DEFINE1(sigsuspend, sigset_t __user *, uset)
{
        return sys_rt_sigsuspend(uset, sizeof(sigset_t));
}
#endif

#ifdef CONFIG_TRAD_SIGNALS
SYSCALL_DEFINE3(sigaction, int, sig, const struct sigaction __user *, act,
        struct sigaction __user *, oact)
{
        struct k_sigaction new_ka, old_ka;
        int ret;
        int err = 0;

        if (act) {
                old_sigset_t mask;

                if (!access_ok(act, sizeof(*act)))
                        return -EFAULT;
                err |= __get_user(new_ka.sa.sa_handler, &act->sa_handler);
                err |= __get_user(new_ka.sa.sa_flags, &act->sa_flags);
                err |= __get_user(mask, &act->sa_mask.sig[0]);
                if (err)
                        return -EFAULT;

                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(oact, sizeof(*oact)))
                        return -EFAULT;
                err |= __put_user(old_ka.sa.sa_flags, &oact->sa_flags);
                err |= __put_user(old_ka.sa.sa_handler, &oact->sa_handler);
                err |= __put_user(old_ka.sa.sa_mask.sig[0], oact->sa_mask.sig);
                err |= __put_user(0, &oact->sa_mask.sig[1]);
                err |= __put_user(0, &oact->sa_mask.sig[2]);
                err |= __put_user(0, &oact->sa_mask.sig[3]);
                if (err)
                        return -EFAULT;
        }

        return ret;
}
#endif

#ifdef CONFIG_TRAD_SIGNALS
asmlinkage void sys_sigreturn(void)
{
        struct sigframe __user *frame;
        struct pt_regs *regs;
        sigset_t blocked;
        int sig;

        regs = current_pt_regs();
        frame = (struct sigframe __user *)regs->regs[29];
        if (!access_ok(frame, sizeof(*frame)))
                goto badframe;
        if (__copy_from_user(&blocked, &frame->sf_mask, sizeof(blocked)))
                goto badframe;

        set_current_blocked(&blocked);

        sig = restore_sigcontext(regs, &frame->sf_sc);
        if (sig < 0)
                goto badframe;
        else if (sig)
                force_sig(sig);

        /*
         * Don't let your children do this ...
         */
        __asm__ __volatile__(
                "move\t$29, %0\n\t"
                "j\tsyscall_exit"
                : /* no outputs */
                : "r" (regs));
        /* Unreached */

badframe:
        force_sig(SIGSEGV);
}
#endif /* CONFIG_TRAD_SIGNALS */

asmlinkage void sys_rt_sigreturn(void)
{
        struct rt_sigframe __user *frame;
        struct pt_regs *regs;
        sigset_t set;
        int sig;

        regs = current_pt_regs();
        frame = (struct rt_sigframe __user *)regs->regs[29];
        if (!access_ok(frame, sizeof(*frame)))
                goto badframe;
        if (__copy_from_user(&set, &frame->rs_uc.uc_sigmask, sizeof(set)))
                goto badframe;

        set_current_blocked(&set);

        sig = restore_sigcontext(regs, &frame->rs_uc.uc_mcontext);
        if (sig < 0)
                goto badframe;
        else if (sig)
                force_sig(sig);

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

        /*
         * Don't let your children do this ...
         */
        __asm__ __volatile__(
                "move\t$29, %0\n\t"
                "j\tsyscall_exit"
                : /* no outputs */
                : "r" (regs));
        /* Unreached */

badframe:
        force_sig(SIGSEGV);
}

#ifdef CONFIG_TRAD_SIGNALS
static int setup_frame(void *sig_return, struct ksignal *ksig,
                       struct pt_regs *regs, sigset_t *set)
{
        struct sigframe __user *frame;
        int err = 0;

        frame = get_sigframe(ksig, regs, sizeof(*frame));
        if (!access_ok(frame, sizeof (*frame)))
                return -EFAULT;

        err |= setup_sigcontext(regs, &frame->sf_sc);
        err |= __copy_to_user(&frame->sf_mask, set, sizeof(*set));
        if (err)
                return -EFAULT;

        /*
         * Arguments to signal handler:
         *
         *   a0 = signal number
         *   a1 = 0 (should be cause)
         *   a2 = pointer to struct sigcontext
         *
         * $25 and c0_epc point to the signal handler, $29 points to the
         * struct sigframe.
         */
        regs->regs[ 4] = ksig->sig;
        regs->regs[ 5] = 0;
        regs->regs[ 6] = (unsigned long) &frame->sf_sc;
        regs->regs[29] = (unsigned long) frame;
        regs->regs[31] = (unsigned long) sig_return;
        regs->cp0_epc = regs->regs[25] = (unsigned long) ksig->ka.sa.sa_handler;

        DEBUGP("SIG deliver (%s:%d): sp=0x%p pc=0x%lx ra=0x%lx\n",
               current->comm, current->pid,
               frame, regs->cp0_epc, regs->regs[31]);
        return 0;
}
#endif

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

        frame = get_sigframe(ksig, regs, sizeof(*frame));
        if (!access_ok(frame, sizeof (*frame)))
                return -EFAULT;

        /* Create siginfo.  */
        err |= copy_siginfo_to_user(&frame->rs_info, &ksig->info);

        /* Create the ucontext.  */
        err |= __put_user(0, &frame->rs_uc.uc_flags);
        err |= __put_user(NULL, &frame->rs_uc.uc_link);
        err |= __save_altstack(&frame->rs_uc.uc_stack, regs->regs[29]);
        err |= setup_sigcontext(regs, &frame->rs_uc.uc_mcontext);
        err |= __copy_to_user(&frame->rs_uc.uc_sigmask, set, sizeof(*set));

        if (err)
                return -EFAULT;

        /*
         * Arguments to signal handler:
         *
         *   a0 = signal number
         *   a1 = 0 (should be cause)
         *   a2 = pointer to ucontext
         *
         * $25 and c0_epc point to the signal handler, $29 points to
         * the struct rt_sigframe.
         */
        regs->regs[ 4] = ksig->sig;
        regs->regs[ 5] = (unsigned long) &frame->rs_info;
        regs->regs[ 6] = (unsigned long) &frame->rs_uc;
        regs->regs[29] = (unsigned long) frame;
        regs->regs[31] = (unsigned long) sig_return;
        regs->cp0_epc = regs->regs[25] = (unsigned long) ksig->ka.sa.sa_handler;

        DEBUGP("SIG deliver (%s:%d): sp=0x%p pc=0x%lx ra=0x%lx\n",
               current->comm, current->pid,
               frame, regs->cp0_epc, regs->regs[31]);

        return 0;
}

struct mips_abi mips_abi = {
#ifdef CONFIG_TRAD_SIGNALS
        .setup_frame    = setup_frame,
#endif
        .setup_rt_frame = setup_rt_frame,
        .restart        = __NR_restart_syscall,

        .off_sc_fpregs = offsetof(struct sigcontext, sc_fpregs),
        .off_sc_fpc_csr = offsetof(struct sigcontext, sc_fpc_csr),
        .off_sc_used_math = offsetof(struct sigcontext, sc_used_math),

        .vdso           = &vdso_image,
};

static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
{
        sigset_t *oldset = sigmask_to_save();
        int ret;
        struct mips_abi *abi = current->thread.abi;
        void *vdso = current->mm->context.vdso;

        /*
         * If we were emulating a delay slot instruction, exit that frame such
         * that addresses in the sigframe are as expected for userland and we
         * don't have a problem if we reuse the thread's frame for an
         * instruction within the signal handler.
         */
        dsemul_thread_rollback(regs);

        if (regs->regs[0]) {
                switch(regs->regs[2]) {
                case ERESTART_RESTARTBLOCK:
                case ERESTARTNOHAND:
                        regs->regs[2] = EINTR;
                        break;
                case ERESTARTSYS:
                        if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
                                regs->regs[2] = EINTR;
                                break;
                        }
                /* fallthrough */
                case ERESTARTNOINTR:
                        regs->regs[7] = regs->regs[26];
                        regs->regs[2] = regs->regs[0];
                        regs->cp0_epc -= 4;
                }

                regs->regs[0] = 0;              /* Don't deal with this again.  */
        }

        rseq_signal_deliver(ksig, regs);

        if (sig_uses_siginfo(&ksig->ka, abi))
                ret = abi->setup_rt_frame(vdso + abi->vdso->off_rt_sigreturn,
                                          ksig, regs, oldset);
        else
                ret = abi->setup_frame(vdso + abi->vdso->off_sigreturn,
                                       ksig, regs, oldset);

        signal_setup_done(ret, ksig, 0);
}

static void do_signal(struct pt_regs *regs)
{
        struct ksignal ksig;

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

        if (regs->regs[0]) {
                switch (regs->regs[2]) {
                case ERESTARTNOHAND:
                case ERESTARTSYS:
                case ERESTARTNOINTR:
                        regs->regs[2] = regs->regs[0];
                        regs->regs[7] = regs->regs[26];
                        regs->cp0_epc -= 4;
                        break;

                case ERESTART_RESTARTBLOCK:
                        regs->regs[2] = current->thread.abi->restart;
                        regs->regs[7] = regs->regs[26];
                        regs->cp0_epc -= 4;
                        break;
                }
                regs->regs[0] = 0;      /* Don't deal with this again.  */
        }

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

/*
 * notification of userspace execution resumption
 * - triggered by the TIF_WORK_MASK flags
 */
asmlinkage void do_notify_resume(struct pt_regs *regs, void *unused,
        __u32 thread_info_flags)
{
        local_irq_enable();

        user_exit();

        if (thread_info_flags & _TIF_UPROBE)
                uprobe_notify_resume(regs);

        /* deal with pending signal delivery */
        if (thread_info_flags & _TIF_SIGPENDING)
                do_signal(regs);

        if (thread_info_flags & _TIF_NOTIFY_RESUME) {
                clear_thread_flag(TIF_NOTIFY_RESUME);
                tracehook_notify_resume(regs);
                rseq_handle_notify_resume(NULL, regs);
        }

        user_enter();
}

#if defined(CONFIG_SMP) && defined(CONFIG_MIPS_FP_SUPPORT)
static int smp_save_fp_context(void __user *sc)
{
        return raw_cpu_has_fpu
               ? save_hw_fp_context(sc)
               : copy_fp_to_sigcontext(sc);
}

static int smp_restore_fp_context(void __user *sc)
{
        return raw_cpu_has_fpu
               ? restore_hw_fp_context(sc)
               : copy_fp_from_sigcontext(sc);
}
#endif

static int signal_setup(void)
{
        /*
         * The offset from sigcontext to extended context should be the same
         * regardless of the type of signal, such that userland can always know
         * where to look if it wishes to find the extended context structures.
         */
        BUILD_BUG_ON((offsetof(struct sigframe, sf_extcontext) -
                      offsetof(struct sigframe, sf_sc)) !=
                     (offsetof(struct rt_sigframe, rs_uc.uc_extcontext) -
                      offsetof(struct rt_sigframe, rs_uc.uc_mcontext)));

#if defined(CONFIG_SMP) && defined(CONFIG_MIPS_FP_SUPPORT)
        /* For now just do the cpu_has_fpu check when the functions are invoked */
        save_fp_context = smp_save_fp_context;
        restore_fp_context = smp_restore_fp_context;
#else
        if (cpu_has_fpu) {
                save_fp_context = save_hw_fp_context;
                restore_fp_context = restore_hw_fp_context;
        } else {
                save_fp_context = copy_fp_to_sigcontext;
                restore_fp_context = copy_fp_from_sigcontext;
        }
#endif /* CONFIG_SMP */

        return 0;
}

arch_initcall(signal_setup);