// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
 */
#include <linux/bitfield.h>
#include <linux/extable.h>
#include <linux/uaccess.h>
#include <asm/asm-extable.h>
#include <asm/branch.h>

static inline unsigned long
get_ex_fixup(const struct exception_table_entry *ex)
{
        return ((unsigned long)&ex->fixup + ex->fixup);
}

static inline void regs_set_gpr(struct pt_regs *regs,
                                unsigned int offset, unsigned long val)
{
        if (offset && offset <= MAX_REG_OFFSET)
                *(unsigned long *)((unsigned long)regs + offset) = val;
}

static bool ex_handler_fixup(const struct exception_table_entry *ex,
                             struct pt_regs *regs)
{
        regs->csr_era = get_ex_fixup(ex);

        return true;
}

static bool ex_handler_uaccess_err_zero(const struct exception_table_entry *ex,
                                        struct pt_regs *regs)
{
        int reg_err = FIELD_GET(EX_DATA_REG_ERR, ex->data);
        int reg_zero = FIELD_GET(EX_DATA_REG_ZERO, ex->data);

        regs_set_gpr(regs, reg_err * sizeof(unsigned long), -EFAULT);
        regs_set_gpr(regs, reg_zero * sizeof(unsigned long), 0);
        regs->csr_era = get_ex_fixup(ex);

        return true;
}

bool fixup_exception(struct pt_regs *regs)
{
        const struct exception_table_entry *ex;

        ex = search_exception_tables(exception_era(regs));
        if (!ex)
                return false;

        switch (ex->type) {
        case EX_TYPE_FIXUP:
                return ex_handler_fixup(ex, regs);
        case EX_TYPE_UACCESS_ERR_ZERO:
                return ex_handler_uaccess_err_zero(ex, regs);
        case EX_TYPE_BPF:
                return ex_handler_bpf(ex, regs);
        }

        BUG();
}