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Subject[PATCH -tip v2 7/9] kprobes: Move locks into appropriate functions
Date
Break a big critical region into fine-grained pieces at
registering kprobe path. This helps us to solve circular
locking dependency when introducing ftrace-based kprobes.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
---
kernel/kprobes.c | 63 ++++++++++++++++++++++++++++++++++++------------------
1 files changed, 42 insertions(+), 21 deletions(-)
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 6137fe3..9e47f44 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -759,20 +759,28 @@ static __kprobes void try_to_optimize_kprobe(struct kprobe *p)
struct kprobe *ap;
struct optimized_kprobe *op;

+ /* For preparing optimization, jump_label_text_reserved() is called */
+ jump_label_lock();
+ mutex_lock(&text_mutex);
+
ap = alloc_aggr_kprobe(p);
if (!ap)
- return;
+ goto out;

op = container_of(ap, struct optimized_kprobe, kp);
if (!arch_prepared_optinsn(&op->optinsn)) {
/* If failed to setup optimizing, fallback to kprobe */
arch_remove_optimized_kprobe(op);
kfree(op);
- return;
+ goto out;
}

init_aggr_kprobe(ap, p);
- optimize_kprobe(ap);
+ optimize_kprobe(ap); /* This just kicks optimizer thread */
+
+out:
+ mutex_unlock(&text_mutex);
+ jump_label_unlock();
}

#ifdef CONFIG_SYSCTL
@@ -1144,12 +1152,6 @@ static int __kprobes add_new_kprobe(struct kprobe *ap, struct kprobe *p)
if (p->post_handler && !ap->post_handler)
ap->post_handler = aggr_post_handler;

- if (kprobe_disabled(ap) && !kprobe_disabled(p)) {
- ap->flags &= ~KPROBE_FLAG_DISABLED;
- if (!kprobes_all_disarmed)
- /* Arm the breakpoint again. */
- __arm_kprobe(ap);
- }
return 0;
}

@@ -1189,11 +1191,22 @@ static int __kprobes register_aggr_kprobe(struct kprobe *orig_p,
int ret = 0;
struct kprobe *ap = orig_p;

+ /* For preparing optimization, jump_label_text_reserved() is called */
+ jump_label_lock();
+ /*
+ * Get online CPUs to avoid text_mutex deadlock.with stop machine,
+ * which is invoked by unoptimize_kprobe() in add_new_kprobe()
+ */
+ get_online_cpus();
+ mutex_lock(&text_mutex);
+
if (!kprobe_aggrprobe(orig_p)) {
/* If orig_p is not an aggr_kprobe, create new aggr_kprobe. */
ap = alloc_aggr_kprobe(orig_p);
- if (!ap)
- return -ENOMEM;
+ if (!ap) {
+ ret = -ENOMEM;
+ goto out;
+ }
init_aggr_kprobe(ap, orig_p);
} else if (kprobe_unused(ap))
/* This probe is going to die. Rescue it */
@@ -1213,7 +1226,7 @@ static int __kprobes register_aggr_kprobe(struct kprobe *orig_p,
* free aggr_probe. It will be used next time, or
* freed by unregister_kprobe.
*/
- return ret;
+ goto out;

/* Prepare optimized instructions if possible. */
prepare_optimized_kprobe(ap);
@@ -1228,7 +1241,20 @@ static int __kprobes register_aggr_kprobe(struct kprobe *orig_p,

/* Copy ap's insn slot to p */
copy_kprobe(ap, p);
- return add_new_kprobe(ap, p);
+ ret = add_new_kprobe(ap, p);
+
+out:
+ mutex_unlock(&text_mutex);
+ put_online_cpus();
+ jump_label_unlock();
+
+ if (ret == 0 && kprobe_disabled(ap) && !kprobe_disabled(p)) {
+ ap->flags &= ~KPROBE_FLAG_DISABLED;
+ if (!kprobes_all_disarmed)
+ /* Arm the breakpoint again. */
+ arm_kprobe(ap);
+ }
+ return ret;
}

static int __kprobes in_kprobes_functions(unsigned long addr)
@@ -1387,10 +1413,6 @@ int __kprobes register_kprobe(struct kprobe *p)
return ret;

mutex_lock(&kprobe_mutex);
- jump_label_lock(); /* needed to call jump_label_text_reserved() */
-
- get_online_cpus(); /* For avoiding text_mutex deadlock. */
- mutex_lock(&text_mutex);

old_p = get_kprobe(p->addr);
if (old_p) {
@@ -1399,7 +1421,9 @@ int __kprobes register_kprobe(struct kprobe *p)
goto out;
}

+ mutex_lock(&text_mutex); /* Avoiding text modification */
ret = arch_prepare_kprobe(p);
+ mutex_unlock(&text_mutex);
if (ret)
goto out;

@@ -1408,15 +1432,12 @@ int __kprobes register_kprobe(struct kprobe *p)
&kprobe_table[hash_ptr(p->addr, KPROBE_HASH_BITS)]);

if (!kprobes_all_disarmed && !kprobe_disabled(p))
- __arm_kprobe(p);
+ arm_kprobe(p);

/* Try to optimize kprobe */
try_to_optimize_kprobe(p);

out:
- mutex_unlock(&text_mutex);
- put_online_cpus();
- jump_label_unlock();
mutex_unlock(&kprobe_mutex);

if (probed_mod)


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