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Linux/lib/extable.c

  1 /*
  2  * Derived from arch/ppc/mm/extable.c and arch/i386/mm/extable.c.
  3  *
  4  * Copyright (C) 2004 Paul Mackerras, IBM Corp.
  5  *
  6  * This program is free software; you can redistribute it and/or
  7  * modify it under the terms of the GNU General Public License
  8  * as published by the Free Software Foundation; either version
  9  * 2 of the License, or (at your option) any later version.
 10  */
 11 
 12 #include <linux/module.h>
 13 #include <linux/init.h>
 14 #include <linux/sort.h>
 15 #include <linux/uaccess.h>
 16 
 17 #ifndef ARCH_HAS_RELATIVE_EXTABLE
 18 #define ex_to_insn(x)   ((x)->insn)
 19 #else
 20 static inline unsigned long ex_to_insn(const struct exception_table_entry *x)
 21 {
 22         return (unsigned long)&x->insn + x->insn;
 23 }
 24 #endif
 25 
 26 #ifndef ARCH_HAS_SORT_EXTABLE
 27 #ifndef ARCH_HAS_RELATIVE_EXTABLE
 28 #define swap_ex         NULL
 29 #else
 30 static void swap_ex(void *a, void *b, int size)
 31 {
 32         struct exception_table_entry *x = a, *y = b, tmp;
 33         int delta = b - a;
 34 
 35         tmp = *x;
 36         x->insn = y->insn + delta;
 37         y->insn = tmp.insn - delta;
 38 
 39 #ifdef swap_ex_entry_fixup
 40         swap_ex_entry_fixup(x, y, tmp, delta);
 41 #else
 42         x->fixup = y->fixup + delta;
 43         y->fixup = tmp.fixup - delta;
 44 #endif
 45 }
 46 #endif /* ARCH_HAS_RELATIVE_EXTABLE */
 47 
 48 /*
 49  * The exception table needs to be sorted so that the binary
 50  * search that we use to find entries in it works properly.
 51  * This is used both for the kernel exception table and for
 52  * the exception tables of modules that get loaded.
 53  */
 54 static int cmp_ex(const void *a, const void *b)
 55 {
 56         const struct exception_table_entry *x = a, *y = b;
 57 
 58         /* avoid overflow */
 59         if (ex_to_insn(x) > ex_to_insn(y))
 60                 return 1;
 61         if (ex_to_insn(x) < ex_to_insn(y))
 62                 return -1;
 63         return 0;
 64 }
 65 
 66 void sort_extable(struct exception_table_entry *start,
 67                   struct exception_table_entry *finish)
 68 {
 69         sort(start, finish - start, sizeof(struct exception_table_entry),
 70              cmp_ex, swap_ex);
 71 }
 72 
 73 #ifdef CONFIG_MODULES
 74 /*
 75  * If the exception table is sorted, any referring to the module init
 76  * will be at the beginning or the end.
 77  */
 78 void trim_init_extable(struct module *m)
 79 {
 80         /*trim the beginning*/
 81         while (m->num_exentries &&
 82                within_module_init(ex_to_insn(&m->extable[0]), m)) {
 83                 m->extable++;
 84                 m->num_exentries--;
 85         }
 86         /*trim the end*/
 87         while (m->num_exentries &&
 88                within_module_init(ex_to_insn(&m->extable[m->num_exentries - 1]),
 89                                   m))
 90                 m->num_exentries--;
 91 }
 92 #endif /* CONFIG_MODULES */
 93 #endif /* !ARCH_HAS_SORT_EXTABLE */
 94 
 95 #ifndef ARCH_HAS_SEARCH_EXTABLE
 96 /*
 97  * Search one exception table for an entry corresponding to the
 98  * given instruction address, and return the address of the entry,
 99  * or NULL if none is found.
100  * We use a binary search, and thus we assume that the table is
101  * already sorted.
102  */
103 const struct exception_table_entry *
104 search_extable(const struct exception_table_entry *first,
105                const struct exception_table_entry *last,
106                unsigned long value)
107 {
108         while (first <= last) {
109                 const struct exception_table_entry *mid;
110 
111                 mid = ((last - first) >> 1) + first;
112                 /*
113                  * careful, the distance between value and insn
114                  * can be larger than MAX_LONG:
115                  */
116                 if (ex_to_insn(mid) < value)
117                         first = mid + 1;
118                 else if (ex_to_insn(mid) > value)
119                         last = mid - 1;
120                 else
121                         return mid;
122         }
123         return NULL;
124 }
125 #endif
126 

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