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1 /*
2  * linux/arch/alpha/mm/extable.c
3  */
4 
5 #include <linux/module.h>
6 #include <linux/sort.h>
7 #include <asm/uaccess.h>
8 
ex_to_addr(const struct exception_table_entry * x)9 static inline unsigned long ex_to_addr(const struct exception_table_entry *x)
10 {
11 	return (unsigned long)&x->insn + x->insn;
12 }
13 
swap_ex(void * a,void * b,int size)14 static void swap_ex(void *a, void *b, int size)
15 {
16 	struct exception_table_entry *ex_a = a, *ex_b = b;
17 	unsigned long addr_a = ex_to_addr(ex_a), addr_b = ex_to_addr(ex_b);
18 	unsigned int t = ex_a->fixup.unit;
19 
20 	ex_a->fixup.unit = ex_b->fixup.unit;
21 	ex_b->fixup.unit = t;
22 	ex_a->insn = (int)(addr_b - (unsigned long)&ex_a->insn);
23 	ex_b->insn = (int)(addr_a - (unsigned long)&ex_b->insn);
24 }
25 
26 /*
27  * The exception table needs to be sorted so that the binary
28  * search that we use to find entries in it works properly.
29  * This is used both for the kernel exception table and for
30  * the exception tables of modules that get loaded.
31  */
cmp_ex(const void * a,const void * b)32 static int cmp_ex(const void *a, const void *b)
33 {
34 	const struct exception_table_entry *x = a, *y = b;
35 
36 	/* avoid overflow */
37 	if (ex_to_addr(x) > ex_to_addr(y))
38 		return 1;
39 	if (ex_to_addr(x) < ex_to_addr(y))
40 		return -1;
41 	return 0;
42 }
43 
sort_extable(struct exception_table_entry * start,struct exception_table_entry * finish)44 void sort_extable(struct exception_table_entry *start,
45 		  struct exception_table_entry *finish)
46 {
47 	sort(start, finish - start, sizeof(struct exception_table_entry),
48 	     cmp_ex, swap_ex);
49 }
50 
51 #ifdef CONFIG_MODULES
52 /*
53  * Any entry referring to the module init will be at the beginning or
54  * the end.
55  */
trim_init_extable(struct module * m)56 void trim_init_extable(struct module *m)
57 {
58 	/*trim the beginning*/
59 	while (m->num_exentries &&
60 	       within_module_init(ex_to_addr(&m->extable[0]), m)) {
61 		m->extable++;
62 		m->num_exentries--;
63 	}
64 	/*trim the end*/
65 	while (m->num_exentries &&
66 	       within_module_init(ex_to_addr(&m->extable[m->num_exentries-1]),
67 				  m))
68 		m->num_exentries--;
69 }
70 #endif /* CONFIG_MODULES */
71 
72 const struct exception_table_entry *
search_extable(const struct exception_table_entry * first,const struct exception_table_entry * last,unsigned long value)73 search_extable(const struct exception_table_entry *first,
74 	       const struct exception_table_entry *last,
75 	       unsigned long value)
76 {
77         while (first <= last) {
78 		const struct exception_table_entry *mid;
79 		unsigned long mid_value;
80 
81 		mid = (last - first) / 2 + first;
82 		mid_value = ex_to_addr(mid);
83                 if (mid_value == value)
84                         return mid;
85                 else if (mid_value < value)
86                         first = mid+1;
87                 else
88                         last = mid-1;
89         }
90 
91         return NULL;
92 }
93