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