extable.c

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    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 <asm/uaccess.h>
   16 
   17 #ifndef ARCH_HAS_SORT_EXTABLE
   18 /*
   19  * The exception table needs to be sorted so that the binary
   20  * search that we use to find entries in it works properly.
   21  * This is used both for the kernel exception table and for
   22  * the exception tables of modules that get loaded.
   23  */
   24 static int cmp_ex(const void *a, const void *b)
   25 {
   26         const struct exception_table_entry *x = a, *y = b;
   27 
   28         /* avoid overflow */
   29         if (x->insn > y->insn)
   30                 return 1;
   31         if (x->insn < y->insn)
   32                 return -1;
   33         return 0;
   34 }
   35 
   36 void sort_extable(struct exception_table_entry *start,
   37                   struct exception_table_entry *finish)
   38 {
   39         sort(start, finish - start, sizeof(struct exception_table_entry),
   40              cmp_ex, NULL);
   41 }
   42 
   43 #ifdef CONFIG_MODULES
   44 /*
   45  * If the exception table is sorted, any referring to the module init
   46  * will be at the beginning or the end.
   47  */
   48 void trim_init_extable(struct module *m)
   49 {
   50         /*trim the beginning*/
   51         while (m->num_exentries && within_module_init(m->extable[0].insn, m)) {
   52                 m->extable++;
   53                 m->num_exentries--;
   54         }
   55         /*trim the end*/
   56         while (m->num_exentries &&
   57                 within_module_init(m->extable[m->num_exentries-1].insn, m))
   58                 m->num_exentries--;
   59 }
   60 #endif /* CONFIG_MODULES */
   61 #endif /* !ARCH_HAS_SORT_EXTABLE */
   62 
   63 #ifndef ARCH_HAS_SEARCH_EXTABLE
   64 /*
   65  * Search one exception table for an entry corresponding to the
   66  * given instruction address, and return the address of the entry,
   67  * or NULL if none is found.
   68  * We use a binary search, and thus we assume that the table is
   69  * already sorted.
   70  */
   71 const struct exception_table_entry *
   72 search_extable(const struct exception_table_entry *first,
   73                const struct exception_table_entry *last,
   74                unsigned long value)
   75 {
   76         while (first <= last) {
   77                 const struct exception_table_entry *mid;
   78 
   79                 mid = ((last - first) >> 1) + first;
   80                 /*
   81                  * careful, the distance between value and insn
   82                  * can be larger than MAX_LONG:
   83                  */
   84                 if (mid->insn < value)
   85                         first = mid + 1;
   86                 else if (mid->insn > value)
   87                         last = mid - 1;
   88                 else
   89                         return mid;
   90         }
   91         return NULL;
   92 }
   93 #endif

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FreeBSD/Linux Kernel Cross Reference sys/lib/extable.c

FreeBSD/Linux Kernel Cross Reference
sys/lib/extable.c