arch/s390/mm/extable.c

   1 #include <linux/module.h>
   2 #include <linux/sort.h>
   3 #include <asm/uaccess.h>
   4
   5 /*
   6  * Search one exception table for an entry corresponding to the
   7  * given instruction address, and return the address of the entry,
   8  * or NULL if none is found.
   9  * We use a binary search, and thus we assume that the table is
  10  * already sorted.
  11  */
  12 const struct exception_table_entry *
  13 search_extable(const struct exception_table_entry *first,
  14                const struct exception_table_entry *last,
  15                unsigned long value)
  16 {
  17         const struct exception_table_entry *mid;
  18         unsigned long addr;
  19
  20         while (first <= last) {
  21                 mid = ((last - first) >> 1) + first;
  22                 addr = extable_insn(mid);
  23                 if (addr < value)
  24                         first = mid + 1;
  25                 else if (addr > value)
  26                         last = mid - 1;
  27                 else
  28                         return mid;
  29         }
  30         return NULL;
  31 }
  32
  33 /*
  34  * The exception table needs to be sorted so that the binary
  35  * search that we use to find entries in it works properly.
  36  * This is used both for the kernel exception table and for
  37  * the exception tables of modules that get loaded.
  38  *
  39  */
  40 static int cmp_ex(const void *a, const void *b)
  41 {
  42         const struct exception_table_entry *x = a, *y = b;
  43
  44         /* This compare is only valid after normalization. */
  45         return x->insn - y->insn;
  46 }
  47
  48 void sort_extable(struct exception_table_entry *start,
  49                   struct exception_table_entry *finish)
  50 {
  51         struct exception_table_entry *p;
  52         int i;
  53
  54         /* Normalize entries to being relative to the start of the section */
  55         for (p = start, i = 0; p < finish; p++, i += 8) {
  56                 p->insn += i;
  57                 p->fixup += i + 4;
  58         }
  59         sort(start, finish - start, sizeof(*start), cmp_ex, NULL);
  60         /* Denormalize all entries */
  61         for (p = start, i = 0; p < finish; p++, i += 8) {
  62                 p->insn -= i;
  63                 p->fixup -= i + 4;
  64         }
  65 }
  66
  67 #ifdef CONFIG_MODULES
  68 /*
  69  * If the exception table is sorted, any referring to the module init
  70  * will be at the beginning or the end.
  71  */
  72 void trim_init_extable(struct module *m)
  73 {
  74         /* Trim the beginning */
  75         while (m->num_exentries &&
  76                within_module_init(extable_insn(&m->extable[0]), m)) {
  77                 m->extable++;
  78                 m->num_exentries--;
  79         }
  80         /* Trim the end */
  81         while (m->num_exentries &&
  82                within_module_init(extable_insn(&m->extable[m->num_exentries-1]), m))
  83                 m->num_exentries--;
  84 }
  85 #endif /* CONFIG_MODULES */