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
11 static inline unsigned long
12 get_ex_fixup(const struct exception_table_entry *ex)
13 {
14 return ((unsigned long)&ex->fixup + ex->fixup);
15 }
16
17 static 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
24 static 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
32 static 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
45 bool 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
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