jump label: Add jump_label_text_reserved() to reserve jump points
Jason Baron [Fri, 17 Sep 2010 15:09:08 +0000 (11:09 -0400)]
Add a jump_label_text_reserved(void *start, void *end), so that other
pieces of code that want to modify kernel text, can first verify that
jump label has not reserved the instruction.

Acked-by: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Jason Baron <jbaron@redhat.com>
LKML-Reference: <06236663a3a7b1c1f13576bb9eccb6d9c17b7bfe.1284733808.git.jbaron@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

arch/x86/kernel/kprobes.c
include/linux/jump_label.h
kernel/jump_label.c
kernel/kprobes.c

index e05952a..1cbd54c 100644 (file)
@@ -1218,7 +1218,8 @@ static int __kprobes copy_optimized_instructions(u8 *dest, u8 *src)
        }
        /* Check whether the address range is reserved */
        if (ftrace_text_reserved(src, src + len - 1) ||
-           alternatives_text_reserved(src, src + len - 1))
+           alternatives_text_reserved(src, src + len - 1) ||
+           jump_label_text_reserved(src, src + len - 1))
                return -EBUSY;
 
        return len;
index de58656..b72cd9f 100644 (file)
@@ -20,9 +20,10 @@ extern struct jump_entry __stop___jump_table[];
 
 extern void arch_jump_label_transform(struct jump_entry *entry,
                                 enum jump_label_type type);
+extern void arch_jump_label_text_poke_early(jump_label_t addr);
 extern void jump_label_update(unsigned long key, enum jump_label_type type);
 extern void jump_label_apply_nops(struct module *mod);
-extern void arch_jump_label_text_poke_early(jump_label_t addr);
+extern int jump_label_text_reserved(void *start, void *end);
 
 #define enable_jump_label(key) \
        jump_label_update((unsigned long)key, JUMP_LABEL_ENABLE);
@@ -53,6 +54,11 @@ static inline int jump_label_apply_nops(struct module *mod)
        return 0;
 }
 
+static inline int jump_label_text_reserved(void *start, void *end)
+{
+       return 0;
+}
+
 #endif
 
 #endif
index 460fd40..7be868b 100644 (file)
@@ -177,6 +177,89 @@ void jump_label_update(unsigned long key, enum jump_label_type type)
        mutex_unlock(&jump_label_mutex);
 }
 
+static int addr_conflict(struct jump_entry *entry, void *start, void *end)
+{
+       if (entry->code <= (unsigned long)end &&
+               entry->code + JUMP_LABEL_NOP_SIZE > (unsigned long)start)
+               return 1;
+
+       return 0;
+}
+
+#ifdef CONFIG_MODULES
+
+static int module_conflict(void *start, void *end)
+{
+       struct hlist_head *head;
+       struct hlist_node *node, *node_next, *module_node, *module_node_next;
+       struct jump_label_entry *e;
+       struct jump_label_module_entry *e_module;
+       struct jump_entry *iter;
+       int i, count;
+       int conflict = 0;
+
+       for (i = 0; i < JUMP_LABEL_TABLE_SIZE; i++) {
+               head = &jump_label_table[i];
+               hlist_for_each_entry_safe(e, node, node_next, head, hlist) {
+                       hlist_for_each_entry_safe(e_module, module_node,
+                                                       module_node_next,
+                                                       &(e->modules), hlist) {
+                               count = e_module->nr_entries;
+                               iter = e_module->table;
+                               while (count--) {
+                                       if (addr_conflict(iter, start, end)) {
+                                               conflict = 1;
+                                               goto out;
+                                       }
+                                       iter++;
+                               }
+                       }
+               }
+       }
+out:
+       return conflict;
+}
+
+#endif
+
+/***
+ * jump_label_text_reserved - check if addr range is reserved
+ * @start: start text addr
+ * @end: end text addr
+ *
+ * checks if the text addr located between @start and @end
+ * overlaps with any of the jump label patch addresses. Code
+ * that wants to modify kernel text should first verify that
+ * it does not overlap with any of the jump label addresses.
+ *
+ * returns 1 if there is an overlap, 0 otherwise
+ */
+int jump_label_text_reserved(void *start, void *end)
+{
+       struct jump_entry *iter;
+       struct jump_entry *iter_start = __start___jump_table;
+       struct jump_entry *iter_stop = __start___jump_table;
+       int conflict = 0;
+
+       mutex_lock(&jump_label_mutex);
+       iter = iter_start;
+       while (iter < iter_stop) {
+               if (addr_conflict(iter, start, end)) {
+                       conflict = 1;
+                       goto out;
+               }
+               iter++;
+       }
+
+       /* now check modules */
+#ifdef CONFIG_MODULES
+       conflict = module_conflict(start, end);
+#endif
+out:
+       mutex_unlock(&jump_label_mutex);
+       return conflict;
+}
+
 static __init int init_jump_label(void)
 {
        int ret;
index 18904e4..ec4210c 100644 (file)
@@ -1147,7 +1147,8 @@ int __kprobes register_kprobe(struct kprobe *p)
        preempt_disable();
        if (!kernel_text_address((unsigned long) p->addr) ||
            in_kprobes_functions((unsigned long) p->addr) ||
-           ftrace_text_reserved(p->addr, p->addr)) {
+           ftrace_text_reserved(p->addr, p->addr) ||
+           jump_label_text_reserved(p->addr, p->addr)) {
                preempt_enable();
                return -EINVAL;
        }