// SPDX-License-Identifier: GPL-2.0-or-later

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

#include <asm/csr.h>
#include <asm/signal32.h>
#include <asm/switch_to.h>
#include <asm/ucontext.h>
#include <asm/vdso.h>

#define COMPAT_DEBUG_SIG 0

struct compat_sigcontext {
        struct compat_user_regs_struct sc_regs;
        union __riscv_fp_state sc_fpregs;
};

struct compat_ucontext {
        compat_ulong_t          uc_flags;
        struct compat_ucontext  *uc_link;
        compat_stack_t          uc_stack;
        sigset_t                uc_sigmask;
        /* There's some padding here to allow sigset_t to be expanded in the
         * future.  Though this is unlikely, other architectures put uc_sigmask
         * at the end of this structure and explicitly state it can be
         * expanded, so we didn't want to box ourselves in here. */
        __u8              __unused[1024 / 8 - sizeof(sigset_t)];
        /* We can't put uc_sigmask at the end of this structure because we need
         * to be able to expand sigcontext in the future.  For example, the
         * vector ISA extension will almost certainly add ISA state.  We want
         * to ensure all user-visible ISA state can be saved and restored via a
         * ucontext, so we're putting this at the end in order to allow for
         * infinite extensibility.  Since we know this will be extended and we
         * assume sigset_t won't be extended an extreme amount, we're
         * prioritizing this. */
        struct compat_sigcontext uc_mcontext;
};

struct compat_rt_sigframe {
        struct compat_siginfo info;
        struct compat_ucontext uc;
};

#ifdef CONFIG_FPU
static long compat_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 compat_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 compat_save_fp_state(task, regs) (0)
#define compat_restore_fp_state(task, regs) (0)
#endif

static long compat_restore_sigcontext(struct pt_regs *regs,
        struct compat_sigcontext __user *sc)
{
        long err;
        struct compat_user_regs_struct cregs;

        /* sc_regs is structured the same as the start of pt_regs */
        err = __copy_from_user(&cregs, &sc->sc_regs, sizeof(sc->sc_regs));

        cregs_to_regs(&cregs, regs);

        /* Restore the floating-point state. */
        if (has_fpu())
                err |= compat_restore_fp_state(regs, &sc->sc_fpregs);
        return err;
}

COMPAT_SYSCALL_DEFINE0(rt_sigreturn)
{
        struct pt_regs *regs = current_pt_regs();
        struct compat_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 compat_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 (compat_restore_sigcontext(regs, &frame->uc.uc_mcontext))
                goto badframe;

        if (compat_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 compat_setup_sigcontext(struct compat_rt_sigframe __user *frame,
        struct pt_regs *regs)
{
        struct compat_sigcontext __user *sc = &frame->uc.uc_mcontext;
        struct compat_user_regs_struct cregs;
        long err;

        regs_to_cregs(&cregs, regs);

        /* sc_regs is structured the same as the start of pt_regs */
        err = __copy_to_user(&sc->sc_regs, &cregs, sizeof(sc->sc_regs));
        /* Save the floating-point state. */
        if (has_fpu())
                err |= compat_save_fp_state(regs, &sc->sc_fpregs);
        return err;
}

static inline void __user *compat_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;
}

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

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

        err |= copy_siginfo_to_user32(&frame->info, &ksig->info);

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

        regs->ra = (unsigned long)COMPAT_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->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 COMPAT_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;
}