1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Based on arch/arm/mm/extable.c
4 */
5
6#include <linux/bitfield.h>
7#include <linux/extable.h>
8#include <linux/uaccess.h>
9
10#include <asm/asm-extable.h>
11#include <asm/ptrace.h>
12
13static inline unsigned long
14get_ex_fixup(const struct exception_table_entry *ex)
15{
16	return ((unsigned long)&ex->fixup + ex->fixup);
17}
18
19static bool ex_handler_uaccess_err_zero(const struct exception_table_entry *ex,
20					struct pt_regs *regs)
21{
22	int reg_err = FIELD_GET(EX_DATA_REG_ERR, ex->data);
23	int reg_zero = FIELD_GET(EX_DATA_REG_ZERO, ex->data);
24
25	pt_regs_write_reg(regs, reg_err, -EFAULT);
26	pt_regs_write_reg(regs, reg_zero, 0);
27
28	regs->pc = get_ex_fixup(ex);
29	return true;
30}
31
32static bool
33ex_handler_load_unaligned_zeropad(const struct exception_table_entry *ex,
34				  struct pt_regs *regs)
35{
36	int reg_data = FIELD_GET(EX_DATA_REG_DATA, ex->data);
37	int reg_addr = FIELD_GET(EX_DATA_REG_ADDR, ex->data);
38	unsigned long data, addr, offset;
39
40	addr = pt_regs_read_reg(regs, reg_addr);
41
42	offset = addr & 0x7UL;
43	addr &= ~0x7UL;
44
45	data = *(unsigned long*)addr;
46
47#ifndef __AARCH64EB__
48	data >>= 8 * offset;
49#else
50	data <<= 8 * offset;
51#endif
52
53	pt_regs_write_reg(regs, reg_data, data);
54
55	regs->pc = get_ex_fixup(ex);
56	return true;
57}
58
59bool fixup_exception(struct pt_regs *regs)
60{
61	const struct exception_table_entry *ex;
62
63	ex = search_exception_tables(instruction_pointer(regs));
64	if (!ex)
65		return false;
66
67	switch (ex->type) {
68	case EX_TYPE_BPF:
69		return ex_handler_bpf(ex, regs);
70	case EX_TYPE_UACCESS_ERR_ZERO:
71	case EX_TYPE_KACCESS_ERR_ZERO:
72		return ex_handler_uaccess_err_zero(ex, regs);
73	case EX_TYPE_LOAD_UNALIGNED_ZEROPAD:
74		return ex_handler_load_unaligned_zeropad(ex, regs);
75	}
76
77	BUG();
78}
79