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
13 typedef bool (*ex_handler_t)(const struct exception_table_entry *,
14 struct pt_regs *);
15
16 static inline unsigned long
get_ex_fixup(const struct exception_table_entry * ex)17 get_ex_fixup(const struct exception_table_entry *ex)
18 {
19 return ((unsigned long)&ex->fixup + ex->fixup);
20 }
21
ex_handler_fixup(const struct exception_table_entry * ex,struct pt_regs * regs)22 static bool ex_handler_fixup(const struct exception_table_entry *ex,
23 struct pt_regs *regs)
24 {
25 regs->pc = get_ex_fixup(ex);
26 return true;
27 }
28
ex_handler_uaccess_err_zero(const struct exception_table_entry * ex,struct pt_regs * regs)29 static bool ex_handler_uaccess_err_zero(const struct exception_table_entry *ex,
30 struct pt_regs *regs)
31 {
32 int reg_err = FIELD_GET(EX_DATA_REG_ERR, ex->data);
33 int reg_zero = FIELD_GET(EX_DATA_REG_ZERO, ex->data);
34
35 pt_regs_write_reg(regs, reg_err, -EFAULT);
36 pt_regs_write_reg(regs, reg_zero, 0);
37
38 regs->pc = get_ex_fixup(ex);
39 return true;
40 }
41
42 static bool
ex_handler_load_unaligned_zeropad(const struct exception_table_entry * ex,struct pt_regs * regs)43 ex_handler_load_unaligned_zeropad(const struct exception_table_entry *ex,
44 struct pt_regs *regs)
45 {
46 int reg_data = FIELD_GET(EX_DATA_REG_DATA, ex->type);
47 int reg_addr = FIELD_GET(EX_DATA_REG_ADDR, ex->type);
48 unsigned long data, addr, offset;
49
50 addr = pt_regs_read_reg(regs, reg_addr);
51
52 offset = addr & 0x7UL;
53 addr &= ~0x7UL;
54
55 data = *(unsigned long*)addr;
56
57 #ifndef __AARCH64EB__
58 data >>= 8 * offset;
59 #else
60 data <<= 8 * offset;
61 #endif
62
63 pt_regs_write_reg(regs, reg_data, data);
64
65 regs->pc = get_ex_fixup(ex);
66 return true;
67 }
68
fixup_exception(struct pt_regs * regs)69 bool fixup_exception(struct pt_regs *regs)
70 {
71 const struct exception_table_entry *ex;
72
73 ex = search_exception_tables(instruction_pointer(regs));
74 if (!ex)
75 return false;
76
77 switch (ex->type) {
78 case EX_TYPE_FIXUP:
79 return ex_handler_fixup(ex, regs);
80 case EX_TYPE_BPF:
81 return ex_handler_bpf(ex, regs);
82 case EX_TYPE_UACCESS_ERR_ZERO:
83 return ex_handler_uaccess_err_zero(ex, regs);
84 case EX_TYPE_LOAD_UNALIGNED_ZEROPAD:
85 return ex_handler_load_unaligned_zeropad(ex, regs);
86 }
87
88 BUG();
89 }
90