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 static inline unsigned long
14 get_ex_fixup(const struct exception_table_entry *ex)
15 {
16 return ((unsigned long)&ex->fixup + ex->fixup);
17 }
18
19 static 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
32 static bool
33 ex_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
59 bool 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
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