ftrace, kprobes: Support IPMODIFY flag to find IP modify conflict
Introduce FTRACE_OPS_FL_IPMODIFY to avoid conflict among
ftrace users who may modify regs->ip to change the execution
path. If two or more users modify the regs->ip on the same
function entry, one of them will be broken. So they must add
IPMODIFY flag and make sure that ftrace_set_filter_ip() succeeds.
Note that ftrace doesn't allow ftrace_ops which has IPMODIFY
flag to have notrace hash, and the ftrace_ops must have a
filter hash (so that the ftrace_ops can hook only specific
entries), because it strongly depends on the address and
must be allowed for only few selected functions.
Link: http://lkml.kernel.org/r/20141121102516.11844.27829.stgit@localhost.localdomain
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Petr Mladek <pmladek@suse.cz>
Cc: Vojtech Pavlik <vojtech@suse.cz>
Cc: Miroslav Benes <mbenes@suse.cz>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
[ fixed up some of the comments ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 588af40..929a733d 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1358,6 +1358,9 @@
static void
ftrace_hash_rec_enable_modify(struct ftrace_ops *ops, int filter_hash);
+static int ftrace_hash_ipmodify_update(struct ftrace_ops *ops,
+ struct ftrace_hash *new_hash);
+
static int
ftrace_hash_move(struct ftrace_ops *ops, int enable,
struct ftrace_hash **dst, struct ftrace_hash *src)
@@ -1368,8 +1371,13 @@
struct ftrace_hash *new_hash;
int size = src->count;
int bits = 0;
+ int ret;
int i;
+ /* Reject setting notrace hash on IPMODIFY ftrace_ops */
+ if (ops->flags & FTRACE_OPS_FL_IPMODIFY && !enable)
+ return -EINVAL;
+
/*
* If the new source is empty, just free dst and assign it
* the empty_hash.
@@ -1403,6 +1411,16 @@
}
update:
+ /* Make sure this can be applied if it is IPMODIFY ftrace_ops */
+ if (enable) {
+ /* IPMODIFY should be updated only when filter_hash updating */
+ ret = ftrace_hash_ipmodify_update(ops, new_hash);
+ if (ret < 0) {
+ free_ftrace_hash(new_hash);
+ return ret;
+ }
+ }
+
/*
* Remove the current set, update the hash and add
* them back.
@@ -1767,6 +1785,114 @@
ftrace_hash_rec_update_modify(ops, filter_hash, 1);
}
+/*
+ * Try to update IPMODIFY flag on each ftrace_rec. Return 0 if it is OK
+ * or no-needed to update, -EBUSY if it detects a conflict of the flag
+ * on a ftrace_rec, and -EINVAL if the new_hash tries to trace all recs.
+ * Note that old_hash and new_hash has below meanings
+ * - If the hash is NULL, it hits all recs (if IPMODIFY is set, this is rejected)
+ * - If the hash is EMPTY_HASH, it hits nothing
+ * - Anything else hits the recs which match the hash entries.
+ */
+static int __ftrace_hash_update_ipmodify(struct ftrace_ops *ops,
+ struct ftrace_hash *old_hash,
+ struct ftrace_hash *new_hash)
+{
+ struct ftrace_page *pg;
+ struct dyn_ftrace *rec, *end = NULL;
+ int in_old, in_new;
+
+ /* Only update if the ops has been registered */
+ if (!(ops->flags & FTRACE_OPS_FL_ENABLED))
+ return 0;
+
+ if (!(ops->flags & FTRACE_OPS_FL_IPMODIFY))
+ return 0;
+
+ /*
+ * Since the IPMODIFY is a very address sensitive action, we do not
+ * allow ftrace_ops to set all functions to new hash.
+ */
+ if (!new_hash || !old_hash)
+ return -EINVAL;
+
+ /* Update rec->flags */
+ do_for_each_ftrace_rec(pg, rec) {
+ /* We need to update only differences of filter_hash */
+ in_old = !!ftrace_lookup_ip(old_hash, rec->ip);
+ in_new = !!ftrace_lookup_ip(new_hash, rec->ip);
+ if (in_old == in_new)
+ continue;
+
+ if (in_new) {
+ /* New entries must ensure no others are using it */
+ if (rec->flags & FTRACE_FL_IPMODIFY)
+ goto rollback;
+ rec->flags |= FTRACE_FL_IPMODIFY;
+ } else /* Removed entry */
+ rec->flags &= ~FTRACE_FL_IPMODIFY;
+ } while_for_each_ftrace_rec();
+
+ return 0;
+
+rollback:
+ end = rec;
+
+ /* Roll back what we did above */
+ do_for_each_ftrace_rec(pg, rec) {
+ if (rec == end)
+ goto err_out;
+
+ in_old = !!ftrace_lookup_ip(old_hash, rec->ip);
+ in_new = !!ftrace_lookup_ip(new_hash, rec->ip);
+ if (in_old == in_new)
+ continue;
+
+ if (in_new)
+ rec->flags &= ~FTRACE_FL_IPMODIFY;
+ else
+ rec->flags |= FTRACE_FL_IPMODIFY;
+ } while_for_each_ftrace_rec();
+
+err_out:
+ return -EBUSY;
+}
+
+static int ftrace_hash_ipmodify_enable(struct ftrace_ops *ops)
+{
+ struct ftrace_hash *hash = ops->func_hash->filter_hash;
+
+ if (ftrace_hash_empty(hash))
+ hash = NULL;
+
+ return __ftrace_hash_update_ipmodify(ops, EMPTY_HASH, hash);
+}
+
+/* Disabling always succeeds */
+static void ftrace_hash_ipmodify_disable(struct ftrace_ops *ops)
+{
+ struct ftrace_hash *hash = ops->func_hash->filter_hash;
+
+ if (ftrace_hash_empty(hash))
+ hash = NULL;
+
+ __ftrace_hash_update_ipmodify(ops, hash, EMPTY_HASH);
+}
+
+static int ftrace_hash_ipmodify_update(struct ftrace_ops *ops,
+ struct ftrace_hash *new_hash)
+{
+ struct ftrace_hash *old_hash = ops->func_hash->filter_hash;
+
+ if (ftrace_hash_empty(old_hash))
+ old_hash = NULL;
+
+ if (ftrace_hash_empty(new_hash))
+ new_hash = NULL;
+
+ return __ftrace_hash_update_ipmodify(ops, old_hash, new_hash);
+}
+
static void print_ip_ins(const char *fmt, unsigned char *p)
{
int i;
@@ -2436,6 +2562,15 @@
*/
ops->flags |= FTRACE_OPS_FL_ENABLED | FTRACE_OPS_FL_ADDING;
+ ret = ftrace_hash_ipmodify_enable(ops);
+ if (ret < 0) {
+ /* Rollback registration process */
+ __unregister_ftrace_function(ops);
+ ftrace_start_up--;
+ ops->flags &= ~FTRACE_OPS_FL_ENABLED;
+ return ret;
+ }
+
ftrace_hash_rec_enable(ops, 1);
ftrace_startup_enable(command);
@@ -2464,6 +2599,8 @@
*/
WARN_ON_ONCE(ftrace_start_up < 0);
+ /* Disabling ipmodify never fails */
+ ftrace_hash_ipmodify_disable(ops);
ftrace_hash_rec_disable(ops, 1);
ops->flags &= ~FTRACE_OPS_FL_ENABLED;
@@ -3058,9 +3195,10 @@
if (iter->flags & FTRACE_ITER_ENABLED) {
struct ftrace_ops *ops = NULL;
- seq_printf(m, " (%ld)%s",
+ seq_printf(m, " (%ld)%s%s",
ftrace_rec_count(rec),
- rec->flags & FTRACE_FL_REGS ? " R" : " ");
+ rec->flags & FTRACE_FL_REGS ? " R" : " ",
+ rec->flags & FTRACE_FL_IPMODIFY ? " I" : " ");
if (rec->flags & FTRACE_FL_TRAMP_EN) {
ops = ftrace_find_tramp_ops_any(rec);
if (ops)