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authorRusty Russell <rusty@rustcorp.com.au>2009-06-12 21:47:03 -0600
committerRusty Russell <rusty@rustcorp.com.au>2009-06-12 21:47:04 +0930
commitad6561dffa17f17bb68d7207d422c26c381c4313 (patch)
tree04cf6480ccd6732ab0ffe3d552bd32599390ff65 /arch/sparc/mm/extable.c
parentc398df30d5caad626ac72bfab0361a7b0f67a661 (diff)
module: trim exception table on init free.
It's theoretically possible that there are exception table entries which point into the (freed) init text of modules. These could cause future problems if other modules get loaded into that memory and cause an exception as we'd see the wrong fixup. The only case I know of is kvm-intel.ko (when CONFIG_CC_OPTIMIZE_FOR_SIZE=n). Amerigo fixed this long-standing FIXME in the x86 version, but this patch is more general. This implements trim_init_extable(); most archs are simple since they use the standard lib/extable.c sort code. Alpha and IA64 use relative addresses in their fixups, so thier trimming is a slight variation. Sparc32 is unique; it doesn't seem to define ARCH_HAS_SORT_EXTABLE, yet it defines its own sort_extable() which overrides the one in lib. It doesn't sort, so we have to mark deleted entries instead of actually trimming them. Inspired-by: Amerigo Wang <amwang@redhat.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Cc: linux-alpha@vger.kernel.org Cc: sparclinux@vger.kernel.org Cc: linux-ia64@vger.kernel.org
Diffstat (limited to 'arch/sparc/mm/extable.c')
-rw-r--r--arch/sparc/mm/extable.c29
1 files changed, 29 insertions, 0 deletions
diff --git a/arch/sparc/mm/extable.c b/arch/sparc/mm/extable.c
index 16cc28935e3..a61c349448e 100644
--- a/arch/sparc/mm/extable.c
+++ b/arch/sparc/mm/extable.c
@@ -28,6 +28,10 @@ search_extable(const struct exception_table_entry *start,
* word 3: last insn address + 4 bytes
* word 4: fixup code address
*
+ * Deleted entries are encoded as:
+ * word 1: unused
+ * word 2: -1
+ *
* See asm/uaccess.h for more details.
*/
@@ -39,6 +43,10 @@ search_extable(const struct exception_table_entry *start,
continue;
}
+ /* A deleted entry; see trim_init_extable */
+ if (walk->fixup == -1)
+ continue;
+
if (walk->insn == value)
return walk;
}
@@ -57,6 +65,27 @@ search_extable(const struct exception_table_entry *start,
return NULL;
}
+#ifdef CONFIG_MODULES
+/* We could memmove them around; easier to mark the trimmed ones. */
+void trim_init_extable(struct module *m)
+{
+ unsigned int i;
+ bool range;
+
+ for (i = 0; i < m->num_exentries; i += range ? 2 : 1) {
+ range = m->extable[i].fixup == 0;
+
+ if (within_module_init(m->extable[i].insn, m)) {
+ m->extable[i].fixup = -1;
+ if (range)
+ m->extable[i+1].fixup = -1;
+ }
+ if (range)
+ i++;
+ }
+}
+#endif /* CONFIG_MODULES */
+
/* Special extable search, which handles ranges. Returns fixup */
unsigned long search_extables_range(unsigned long addr, unsigned long *g2)
{