arch/riscv/mm/extable.c

root/arch/riscv/mm/extable.c
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (C) 2009 Sunplus Core Technology Co., Ltd.
 *  Lennox Wu <lennox.wu@sunplusct.com>
 *  Chen Liqin <liqin.chen@sunplusct.com>
 * Copyright (C) 2013 Regents of the University of California
 */


#include <linux/bitfield.h>
#include <linux/extable.h>
#include <linux/module.h>
#include <linux/uaccess.h>
#include <asm/asm-extable.h>
#include <asm/ptrace.h>

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

static bool ex_handler_fixup(const struct exception_table_entry *ex,
                             struct pt_regs *regs)
{
        regs->epc = get_ex_fixup(ex);
        return true;
}

static inline unsigned long regs_get_gpr(struct pt_regs *regs, unsigned int offset)
{
        if (unlikely(!offset || offset > MAX_REG_OFFSET))
                return 0;

        return *(unsigned long *)((unsigned long)regs + offset);
}

static inline void regs_set_gpr(struct pt_regs *regs, unsigned int offset,
                                unsigned long val)
{
        if (unlikely(offset > MAX_REG_OFFSET))
                return;

        if (offset)
                *(unsigned long *)((unsigned long)regs + offset) = val;
}

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->epc = get_ex_fixup(ex);
        return true;
}

static bool
ex_handler_load_unaligned_zeropad(const struct exception_table_entry *ex,
                                  struct pt_regs *regs)
{
        int reg_data = FIELD_GET(EX_DATA_REG_DATA, ex->data);
        int reg_addr = FIELD_GET(EX_DATA_REG_ADDR, ex->data);
        unsigned long data, addr, offset;

        addr = regs_get_gpr(regs, reg_addr * sizeof(unsigned long));

        offset = addr & 0x7UL;
        addr &= ~0x7UL;

        data = *(unsigned long *)addr >> (offset * 8);

        regs_set_gpr(regs, reg_data * sizeof(unsigned long), data);

        regs->epc = get_ex_fixup(ex);
        return true;
}

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

        ex = search_exception_tables(regs->epc);
        if (!ex)
                return false;

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

        BUG();
}
Linux
