1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
4 */
5#include <linux/bitfield.h>
6#include <linux/extable.h>
7#include <linux/uaccess.h>
8#include <asm/asm-extable.h>
9#include <asm/branch.h>
10
11static inline unsigned long
12get_ex_fixup(const struct exception_table_entry *ex)
13{
14	return ((unsigned long)&ex->fixup + ex->fixup);
15}
16
17static inline void regs_set_gpr(struct pt_regs *regs,
18				unsigned int offset, unsigned long val)
19{
20	if (offset && offset <= MAX_REG_OFFSET)
21		*(unsigned long *)((unsigned long)regs + offset) = val;
22}
23
24static bool ex_handler_fixup(const struct exception_table_entry *ex,
25			     struct pt_regs *regs)
26{
27	regs->csr_era = get_ex_fixup(ex);
28
29	return true;
30}
31
32static bool ex_handler_uaccess_err_zero(const struct exception_table_entry *ex,
33					struct pt_regs *regs)
34{
35	int reg_err = FIELD_GET(EX_DATA_REG_ERR, ex->data);
36	int reg_zero = FIELD_GET(EX_DATA_REG_ZERO, ex->data);
37
38	regs_set_gpr(regs, reg_err * sizeof(unsigned long), -EFAULT);
39	regs_set_gpr(regs, reg_zero * sizeof(unsigned long), 0);
40	regs->csr_era = get_ex_fixup(ex);
41
42	return true;
43}
44
45bool fixup_exception(struct pt_regs *regs)
46{
47	const struct exception_table_entry *ex;
48
49	ex = search_exception_tables(exception_era(regs));
50	if (!ex)
51		return false;
52
53	switch (ex->type) {
54	case EX_TYPE_FIXUP:
55		return ex_handler_fixup(ex, regs);
56	case EX_TYPE_UACCESS_ERR_ZERO:
57		return ex_handler_uaccess_err_zero(ex, regs);
58	case EX_TYPE_BPF:
59		return ex_handler_bpf(ex, regs);
60	}
61
62	BUG();
63}
64