// SPDX-License-Identifier: GPL-2.0

#include <linux/signal.h>
#include <linux/uaccess.h>
#include <linux/syscalls.h>
#include <linux/resume_user_mode.h>

#include <asm/traps.h>
#include <asm/ucontext.h>
#include <asm/vdso.h>

#include <abi/regdef.h>

#ifdef CONFIG_CPU_HAS_FPU
#include <abi/fpu.h>
static int restore_fpu_state(struct sigcontext __user *sc)
{
        int err = 0;
        struct user_fp user_fp;

        err = __copy_from_user(&user_fp, &sc->sc_user_fp, sizeof(user_fp));

        restore_from_user_fp(&user_fp);

        return err;
}

static int save_fpu_state(struct sigcontext __user *sc)
{
        struct user_fp user_fp;

        save_to_user_fp(&user_fp);

        return __copy_to_user(&sc->sc_user_fp, &user_fp, sizeof(user_fp));
}
#else
#define restore_fpu_state(sigcontext)   (0)
#define save_fpu_state(sigcontext)      (0)
#endif

struct rt_sigframe {
        /*
         * pad[3] is compatible with the same struct defined in
         * gcc/libgcc/config/csky/linux-unwind.h
         */
        int pad[3];
        struct siginfo info;
        struct ucontext uc;
};

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

        /* sc_pt_regs is structured the same as the start of pt_regs */
        err |= __copy_from_user(regs, &sc->sc_pt_regs, sizeof(struct pt_regs));

        /* BIT(0) of regs->sr is Condition Code/Carry bit */
        regs->sr = (sr & ~1) | (regs->sr & 1);

        /* Restore the floating-point state. */
        err |= restore_fpu_state(sc);

        return err;
}

SYSCALL_DEFINE0(rt_sigreturn)
{
        struct pt_regs *regs = current_pt_regs();
        struct rt_sigframe __user *frame;
        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->usp;

        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:
        force_sig(SIGSEGV);
        return 0;
}

static int setup_sigcontext(struct rt_sigframe __user *frame,
        struct pt_regs *regs)
{
        struct sigcontext __user *sc = &frame->uc.uc_mcontext;
        int err = 0;

        err |= __copy_to_user(&sc->sc_pt_regs, regs, sizeof(struct pt_regs));
        err |= save_fpu_state(sc);

        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->usp;

        /*
         * 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 &= -8UL;

        return (void __user *)sp;
}

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 (!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->usp);
        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. */
        regs->lr = (unsigned long)VDSO_SYMBOL(
                current->mm->context.vdso, rt_sigreturn);

        /*
         * 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->pc  = (unsigned long)ksig->ka.sa.sa_handler;
        regs->usp = (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 */

        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 (in_syscall(regs)) {
                /* Avoid additional syscall restarting via ret_from_exception */
                forget_syscall(regs);

                /* 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->pc -= TRAP0_SIZE;
                        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 (in_syscall(regs)) {
                /* Avoid additional syscall restarting via ret_from_exception */
                forget_syscall(regs);

                /* Restart the system call - no handlers present */
                switch (regs->a0) {
                case -ERESTARTNOHAND:
                case -ERESTARTSYS:
                case -ERESTARTNOINTR:
                        regs->a0 = regs->orig_a0;
                        regs->pc -= TRAP0_SIZE;
                        break;
                case -ERESTART_RESTARTBLOCK:
                        regs->a0 = regs->orig_a0;
                        regs_syscallid(regs) = __NR_restart_syscall;
                        regs->pc -= TRAP0_SIZE;
                        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 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)
                resume_user_mode_work(regs);
}