// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (C) 2009 Sunplus Core Technology Co., Ltd.
 *  Chen Liqin <liqin.chen@sunplusct.com>
 *  Lennox Wu <lennox.wu@sunplusct.com>
 * Copyright (C) 2012 Regents of the University of California
 */

#include <linux/signal.h>
#include <linux/uaccess.h>
#include <linux/syscalls.h>
#include <linux/tracehook.h>
#include <linux/linkage.h>

#include <asm/ucontext.h>
#include <asm/vdso.h>
#include <asm/switch_to.h>
#include <asm/csr.h>

extern u32 __user_rt_sigreturn[2];

#define DEBUG_SIG 0

struct rt_sigframe {
        struct siginfo info;
        struct ucontext uc;
#ifndef CONFIG_MMU
        u32 sigreturn_code[2];
#endif
};

#ifdef CONFIG_FPU
static long restore_fp_state(struct pt_regs *regs,
                             union __riscv_fp_state __user *sc_fpregs)
{
        long err;
        struct __riscv_d_ext_state __user *state = &sc_fpregs->d;
        size_t i;

        err = __copy_from_user(&current->thread.fstate, state, sizeof(*state));
        if (unlikely(err))
                return err;

        fstate_restore(current, regs);

        /* We support no other extension state at this time. */
        for (i = 0; i < ARRAY_SIZE(sc_fpregs->q.reserved); i++) {
                u32 value;

                err = __get_user(value, &sc_fpregs->q.reserved[i]);
                if (unlikely(err))
                        break;
                if (value != 0)
                        return -EINVAL;
        }

        return err;
}

static long save_fp_state(struct pt_regs *regs,
                          union __riscv_fp_state __user *sc_fpregs)
{
        long err;
        struct __riscv_d_ext_state __user *state = &sc_fpregs->d;
        size_t i;

        fstate_save(current, regs);
        err = __copy_to_user(state, &current->thread.fstate, sizeof(*state));
        if (unlikely(err))
                return err;

        /* We support no other extension state at this time. */
        for (i = 0; i < ARRAY_SIZE(sc_fpregs->q.reserved); i++) {
                err = __put_user(0, &sc_fpregs->q.reserved[i]);
                if (unlikely(err))
                        break;
        }

        return err;
}
#else
#define save_fp_state(task, regs) (0)
#define restore_fp_state(task, regs) (0)
#endif

static long restore_sigcontext(struct pt_regs *regs,
        struct sigcontext __user *sc)
{
        long err;
        /* sc_regs is structured the same as the start of pt_regs */
        err = __copy_from_user(regs, &sc->sc_regs, sizeof(sc->sc_regs));
        /* Restore the floating-point state. */
        if (has_fpu())
                err |= restore_fp_state(regs, &sc->sc_fpregs);
        return err;
}

SYSCALL_DEFINE0(rt_sigreturn)
{
        struct pt_regs *regs = current_pt_regs();
        struct rt_sigframe __user *frame;
        struct task_struct *task;
        sigset_t set;

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

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

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

        return regs->a0;

badframe:
        task = current;
        if (show_unhandled_signals) {
                pr_info_ratelimited(
                        "%s[%d]: bad frame in %s: frame=%p pc=%p sp=%p\n",
                        task->comm, task_pid_nr(task), __func__,
                        frame, (void *)regs->epc, (void *)regs->sp);
        }
        force_sig(SIGSEGV);
        return 0;
}

static long setup_sigcontext(struct rt_sigframe __user *frame,
        struct pt_regs *regs)
{
        struct sigcontext __user *sc = &frame->uc.uc_mcontext;
        long err;
        /* sc_regs is structured the same as the start of pt_regs */
        err = __copy_to_user(&sc->sc_regs, regs, sizeof(sc->sc_regs));
        /* Save the floating-point state. */
        if (has_fpu())
                err |= save_fp_state(regs, &sc->sc_fpregs);
        return err;
}

static inline void __user *get_sigframe(struct ksignal *ksig,
        struct pt_regs *regs, size_t framesize)
{
        unsigned long sp;
        /* Default to using normal stack */
        sp = regs->sp;

        /*
         * 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 (on_sig_stack(sp) && !likely(on_sig_stack(sp - framesize)))
                return (void __user __force *)(-1UL);

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

        /* Align the stack frame. */
        sp &= ~0xfUL;

        return (void __user *)sp;
}

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

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

        err |= copy_siginfo_to_user(&frame->info, &ksig->info);

        /* Create the ucontext. */
        err |= __put_user(0, &frame->uc.uc_flags);
        err |= __put_user(NULL, &frame->uc.uc_link);
        err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
        err |= setup_sigcontext(frame, regs);
        err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
        if (err)
                return -EFAULT;

        /* Set up to return from userspace. */
#ifdef CONFIG_MMU
        regs->ra = (unsigned long)VDSO_SYMBOL(
                current->mm->context.vdso, rt_sigreturn);
#else
        /*
         * For the nommu case we don't have a VDSO.  Instead we push two
         * instructions to call the rt_sigreturn syscall onto the user stack.
         */
        if (copy_to_user(&frame->sigreturn_code, __user_rt_sigreturn,
                         sizeof(frame->sigreturn_code)))
                return -EFAULT;
        regs->ra = (unsigned long)&frame->sigreturn_code;
#endif /* CONFIG_MMU */

        /*
         * Set up registers for signal handler.
         * Registers that we don't modify keep the value they had from
         * user-space at the time we took the signal.
         * We always pass siginfo and mcontext, regardless of SA_SIGINFO,
         * since some things rely on this (e.g. glibc's debug/segfault.c).
         */
        regs->epc = (unsigned long)ksig->ka.sa.sa_handler;
        regs->sp = (unsigned long)frame;
        regs->a0 = ksig->sig;                     /* a0: signal number */
        regs->a1 = (unsigned long)(&frame->info); /* a1: siginfo pointer */
        regs->a2 = (unsigned long)(&frame->uc);   /* a2: ucontext pointer */

#if DEBUG_SIG
        pr_info("SIG deliver (%s:%d): sig=%d pc=%p ra=%p sp=%p\n",
                current->comm, task_pid_nr(current), ksig->sig,
                (void *)regs->epc, (void *)regs->ra, frame);
#endif

        return 0;
}

static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
{
        sigset_t *oldset = sigmask_to_save();
        int ret;

        /* Are we from a system call? */
        if (regs->cause == EXC_SYSCALL) {
                /* Avoid additional syscall restarting via ret_from_exception */
                regs->cause = -1UL;
                /* If so, check system call restarting.. */
                switch (regs->a0) {
                case -ERESTART_RESTARTBLOCK:
                case -ERESTARTNOHAND:
                        regs->a0 = -EINTR;
                        break;

                case -ERESTARTSYS:
                        if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
                                regs->a0 = -EINTR;
                                break;
                        }
                        fallthrough;
                case -ERESTARTNOINTR:
                        regs->a0 = regs->orig_a0;
                        regs->epc -= 0x4;
                        break;
                }
        }

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

        signal_setup_done(ret, ksig, 0);
}

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

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

        /* Did we come from a system call? */
        if (regs->cause == EXC_SYSCALL) {
                /* Avoid additional syscall restarting via ret_from_exception */
                regs->cause = -1UL;

                /* Restart the system call - no handlers present */
                switch (regs->a0) {
                case -ERESTARTNOHAND:
                case -ERESTARTSYS:
                case -ERESTARTNOINTR:
                        regs->a0 = regs->orig_a0;
                        regs->epc -= 0x4;
                        break;
                case -ERESTART_RESTARTBLOCK:
                        regs->a0 = regs->orig_a0;
                        regs->a7 = __NR_restart_syscall;
                        regs->epc -= 0x4;
                        break;
                }
        }

        /*
         * If there is 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 __visible void do_notify_resume(struct pt_regs *regs,
                                           unsigned long thread_info_flags)
{
        if (thread_info_flags & _TIF_UPROBE)
                uprobe_notify_resume(regs);

        /* Handle pending signal delivery */
        if (thread_info_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
                do_signal(regs);

        if (thread_info_flags & _TIF_NOTIFY_RESUME)
                tracehook_notify_resume(regs);
}