extable.c

// 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();
}