Commit 36dadef23fcc ("kprobes: Init kprobes in early_initcall")
moved the kprobe setup in early_initcall(), which includes kprobe
jump optimization.
The kprobes jump optimizer involves synchronize_rcu_tasks() which
depends on the ksoftirqd and rcu_spawn_tasks_*(). However, since
those are setup in core_initcall(), kprobes jump optimizer can not
run at the early_initcall().
To avoid this issue, make the kprobe optimization disabled in the
early_initcall() and enables it in subsys_initcall().
Note that non-optimized kprobes is still available after
early_initcall(). Only jump optimization is delayed.
Fixes: 36dadef23fcc ("kprobes: Init kprobes in early_initcall")
Reported-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
kernel/kprobes.c | 31 +++++++++++++++++++++----------
1 file changed, 21 insertions(+), 10 deletions(-)
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index d5a3eb74a657..779d8322e307 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -861,7 +861,6 @@ static void try_to_optimize_kprobe(struct kprobe *p)
cpus_read_unlock();
}
-#ifdef CONFIG_SYSCTL
static void optimize_all_kprobes(void)
{
struct hlist_head *head;
@@ -887,6 +886,7 @@ static void optimize_all_kprobes(void)
mutex_unlock(&kprobe_mutex);
}
+#ifdef CONFIG_SYSCTL
static void unoptimize_all_kprobes(void)
{
struct hlist_head *head;
@@ -2497,18 +2497,14 @@ static int __init init_kprobes(void)
}
}
-#if defined(CONFIG_OPTPROBES)
-#if defined(__ARCH_WANT_KPROBES_INSN_SLOT)
- /* Init kprobe_optinsn_slots */
- kprobe_optinsn_slots.insn_size = MAX_OPTINSN_SIZE;
-#endif
- /* By default, kprobes can be optimized */
- kprobes_allow_optimization = true;
-#endif
-
/* By default, kprobes are armed */
kprobes_all_disarmed = false;
+#if defined(CONFIG_OPTPROBES) && defined(__ARCH_WANT_KPROBES_INSN_SLOT)
+ /* Init kprobe_optinsn_slots for allocation */
+ kprobe_optinsn_slots.insn_size = MAX_OPTINSN_SIZE;
+#endif
+
err = arch_init_kprobes();
if (!err)
err = register_die_notifier(&kprobe_exceptions_nb);
@@ -2523,6 +2519,21 @@ static int __init init_kprobes(void)
}
early_initcall(init_kprobes);
+#if defined(CONFIG_OPTPROBES)
+static int __init init_optprobes(void)
+{
+ /*
+ * Enable kprobe optimization - this kicks the optimizer which
+ * depends on synchronize_rcu_tasks() and ksoftirqd, that is
+ * not spawned in early initcall. So delay the optimization.
+ */
+ optimize_all_kprobes();
+
+ return 0;
+}
+subsys_initcall(init_optprobes);
+#endif
+
#ifdef CONFIG_DEBUG_FS
static void report_probe(struct seq_file *pi, struct kprobe *p,
const char *sym, int offset, char *modname, struct kprobe *pp)
