1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3 * Copyright (C) 1999 Magnus Damm <kieraypc01.p.y.kie.era.ericsson.se>
4 *
5 * (C) Copyright 2000
6 * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
7 */
8 #include <common.h>
9 #include <log.h>
10
11 /*
12 * The exception table consists of pairs of addresses: the first is the
13 * address of an instruction that is allowed to fault, and the second is
14 * the address at which the program should continue. No registers are
15 * modified, so it is entirely up to the continuation code to figure out
16 * what to do.
17 *
18 * All the routines below use bits of fixup code that are out of line
19 * with the main instruction path. This means when everything is well,
20 * we don't even have to jump over them. Further, they do not intrude
21 * on our cache or tlb entries.
22 */
23
24 struct exception_table_entry
25 {
26 unsigned long insn, fixup;
27 };
28
29 extern const struct exception_table_entry __start___ex_table[];
30 extern const struct exception_table_entry __stop___ex_table[];
31
32 static inline unsigned long
search_one_table(const struct exception_table_entry * first,const struct exception_table_entry * last,unsigned long value)33 search_one_table(const struct exception_table_entry *first,
34 const struct exception_table_entry *last,
35 unsigned long value)
36 {
37 long diff;
38 while (first <= last) {
39 diff = first->insn - value;
40 if (diff == 0)
41 return first->fixup;
42 first++;
43 }
44
45 return 0;
46 }
47
48 unsigned long
search_exception_table(unsigned long addr)49 search_exception_table(unsigned long addr)
50 {
51 unsigned long ret;
52
53 /* There is only the kernel to search. */
54 ret = search_one_table(__start___ex_table, __stop___ex_table-1, addr);
55 /* if the serial port does not hang in exception, printf can be used */
56 #if !defined(CONFIG_SYS_SERIAL_HANG_IN_EXCEPTION)
57 debug("Bus Fault @ 0x%08lx, fixup 0x%08lx\n", addr, ret);
58 #endif
59 if (ret) return ret;
60
61 return 0;
62 }
63