lib/extable.c: use bsearch() library function in search_extable()

Am 04.06.2017 um 00:38 schrieb Thomas Meyer <[email protected]>:

Signed-off-by Thomas Meyer <[email protected]>

---
 include/linux/extable.h |  3 ++-
 kernel/extable.c        |  2 +-
 kernel/module.c         |  2 +-
 lib/extable.c           | 38 +++++++++++++++++++-------------------
 4 files changed, 23 insertions(+), 22 deletions(-)

include/linux/extable.h +2 -1

index 7effea4..b575bb9 100644
@@ -2,13 +2,14 @@
 #define _LINUX_EXTABLE_H
 
 #include <linux/stddef.h>    /* for NULL */
+#include <linux/types.h>
 
 struct module;
 struct exception_table_entry;
 
 const struct exception_table_entry *
 search_extable(const struct exception_table_entry *first,
-           const struct exception_table_entry *last,
+           const size_t num,
            unsigned long value);
 void sort_extable(struct exception_table_entry *start,
           struct exception_table_entry *finish);

kernel/extable.c +1 -1

index 2676d7f..0c25b75 100644
@@ -55,7 +55,7 @@ const struct exception_table_entry *search_exception_tables(unsigned long addr)
 {
     const struct exception_table_entry *e;
 
-    e = search_extable(__start___ex_table, __stop___ex_table-1, addr);
+    e = search_extable(__start___ex_table, __stop___ex_table - __start___ex_table, addr);
     if (!e)
         e = search_module_extables(addr);
     return e;

kernel/module.c +1 -1

index 4a3665f..22faf11 100644
@@ -4201,7 +4201,7 @@ const struct exception_table_entry *search_module_extables(unsigned long addr)
         goto out;
 
     e = search_extable(mod->extable,
-               mod->extable + mod->num_exentries - 1,
+               mod->num_exentries,
                addr);
 out:
     preempt_enable();

lib/extable.c +19 -19

index 62968da..d4d3929 100644
@@ -9,6 +9,7 @@
  * 2 of the License, or (at your option) any later version.
  */
 
+#include <linux/bsearch.h>
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/sort.h>

@@ -51,7 +52,7 @@ static void swap_ex(void *a, void *b, int size)
  * This is used both for the kernel exception table and for
  * the exception tables of modules that get loaded.
  */
-static int cmp_ex(const void *a, const void *b)
+static int cmp_ex_sort(const void *a, const void *b)
 {
     const struct exception_table_entry *x = a, *y = b;
 

@@ -67,7 +68,7 @@ void sort_extable(struct exception_table_entry *start,
           struct exception_table_entry *finish)
 {
     sort(start, finish - start, sizeof(struct exception_table_entry),
-         cmp_ex, swap_ex);
+         cmp_ex_sort, swap_ex);
 }
 
 #ifdef CONFIG_MODULES

@@ -93,6 +94,20 @@ void trim_init_extable(struct module *m)
 #endif /* !ARCH_HAS_SORT_EXTABLE */
 
 #ifndef ARCH_HAS_SEARCH_EXTABLE
+
+static int cmp_ex_search(const void *key, const void *elt)
+{
+    const struct exception_table_entry * _elt = elt;
+    unsigned long k = *(unsigned long*) key;
+
+    /* avoid overflow */
+    if (k > ex_to_insn(_elt))
+        return 1;
+    if (k < ex_to_insn(_elt))
+        return -1;
+    return 0;
+}
+
 /*
  * Search one exception table for an entry corresponding to the
  * given instruction address, and return the address of the entry,

@@ -102,24 +117,9 @@ void trim_init_extable(struct module *m)
  */
 const struct exception_table_entry *
 search_extable(const struct exception_table_entry *first,
-           const struct exception_table_entry *last,
+           const size_t num, 
            unsigned long value)
 {
-    while (first <= last) {
-        const struct exception_table_entry *mid;
-
-        mid = ((last - first) >> 1) + first;
-        /*
-         * careful, the distance between value and insn
-         * can be larger than MAX_LONG:
-         */
-        if (ex_to_insn(mid) < value)
-            first = mid + 1;
-        else if (ex_to_insn(mid) > value)
-            last = mid - 1;
-        else
-            return mid;
-    }
-    return NULL;
+    return bsearch(&value, first, num, sizeof(struct exception_table_entry), cmp_ex_search);
 }
 #endif