UPSTREAM: extable: add support for relative extables to search and sort routines

This adds support to the generic search_extable() and sort_extable()
implementations for dealing with exception table entries whose fields
contain relative offsets rather than absolute addresses.

Acked-by: Helge Deller <deller@gmx.de>
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Acked-by: H. Peter Anvin <hpa@linux.intel.com>
Acked-by: Tony Luck <tony.luck@intel.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Bug: 30369029
Patchset: kaslr-arm64-4.4

(cherry picked from commit a272858a3c1ecd4a935ba23c66668f81214bd110)
Signed-off-by: Jeff Vander Stoep <jeffv@google.com>
Change-Id: I9d144d351d547c49bf3203a69dfff3cb71a51177

diff --git a/lib/extable.c b/lib/extable.c
index 4cac81ec225e09af4cfd69c36d63a574a8418110..0be02ad561e9e346c01a65434873f9960472047a 100644 (file)
--- a/lib/extable.c
+++ b/lib/extable.c
@@ -14,7 +14,37 @@
 #include <linux/sort.h>
 #include <asm/uaccess.h>
 
+#ifndef ARCH_HAS_RELATIVE_EXTABLE
+#define ex_to_insn(x)  ((x)->insn)
+#else
+static inline unsigned long ex_to_insn(const struct exception_table_entry *x)
+{
+       return (unsigned long)&x->insn + x->insn;
+}
+#endif
+
 #ifndef ARCH_HAS_SORT_EXTABLE
+#ifndef ARCH_HAS_RELATIVE_EXTABLE
+#define swap_ex                NULL
+#else
+static void swap_ex(void *a, void *b, int size)
+{
+       struct exception_table_entry *x = a, *y = b, tmp;
+       int delta = b - a;
+
+       tmp = *x;
+       x->insn = y->insn + delta;
+       y->insn = tmp.insn - delta;
+
+#ifdef swap_ex_entry_fixup
+       swap_ex_entry_fixup(x, y, tmp, delta);
+#else
+       x->fixup = y->fixup + delta;
+       y->fixup = tmp.fixup - delta;
+#endif
+}
+#endif /* ARCH_HAS_RELATIVE_EXTABLE */
+
 /*
  * The exception table needs to be sorted so that the binary
  * search that we use to find entries in it works properly.
@@ -26,9 +56,9 @@ static int cmp_ex(const void *a, const void *b)
        const struct exception_table_entry *x = a, *y = b;
 
        /* avoid overflow */
-       if (x->insn > y->insn)
+       if (ex_to_insn(x) > ex_to_insn(y))
                return 1;
-       if (x->insn < y->insn)
+       if (ex_to_insn(x) < ex_to_insn(y))
                return -1;
        return 0;
 }
@@ -37,7 +67,7 @@ void sort_extable(struct exception_table_entry *start,
                  struct exception_table_entry *finish)
 {
        sort(start, finish - start, sizeof(struct exception_table_entry),
-            cmp_ex, NULL);
+            cmp_ex, swap_ex);
 }
 
 #ifdef CONFIG_MODULES
@@ -48,13 +78,15 @@ void sort_extable(struct exception_table_entry *start,
 void trim_init_extable(struct module *m)
 {
        /*trim the beginning*/
-       while (m->num_exentries && within_module_init(m->extable[0].insn, m)) {
+       while (m->num_exentries &&
+              within_module_init(ex_to_insn(&m->extable[0]), m)) {
                m->extable++;
                m->num_exentries--;
        }
        /*trim the end*/
        while (m->num_exentries &&
-               within_module_init(m->extable[m->num_exentries-1].insn, m))
+              within_module_init(ex_to_insn(&m->extable[m->num_exentries - 1]),
+                                 m))
                m->num_exentries--;
 }
 #endif /* CONFIG_MODULES */
@@ -81,13 +113,13 @@ search_extable(const struct exception_table_entry *first,
                 * careful, the distance between value and insn
                 * can be larger than MAX_LONG:
                 */
-               if (mid->insn < value)
+               if (ex_to_insn(mid) < value)
                        first = mid + 1;
-               else if (mid->insn > value)
+               else if (ex_to_insn(mid) > value)
                        last = mid - 1;
                else
                        return mid;
-        }
-        return NULL;
+       }
+       return NULL;
 }
 #endif