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From: Masami Hiramatsu <mhiramat@kernel.org>
To: Ingo Molnar <mingo@redhat.com>
Cc: "Naveen N . Rao" <naveen.n.rao@linux.vnet.ibm.com>,
	Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>,
	"David S . Miller" <davem@davemloft.net>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	linux-kernel@vger.kernel.org
Subject: [PATCH -tip v2 4/5] kprobes: Return error if fail to reuse kprobe instead of BUG_ON
Date: Tue, 11 Sep 2018 19:20:40 +0900
Message-ID: <153666124040.21306.14150398706331307654.stgit@devbox> (raw)
In-Reply-To: <153666112297.21306.4621579144717171778.stgit@devbox>

Make reuse_unused_kprobe() to return error code if
it fails to reuse unused kprobe for optprobe instead
of calling BUG_ON().

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 kernel/kprobes.c |   27 ++++++++++++++++++++-------
 1 file changed, 20 insertions(+), 7 deletions(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 277a6cbe83db..63c342e5e6c3 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -700,9 +700,10 @@ static void unoptimize_kprobe(struct kprobe *p, bool force)
 }
 
 /* Cancel unoptimizing for reusing */
-static void reuse_unused_kprobe(struct kprobe *ap)
+static int reuse_unused_kprobe(struct kprobe *ap)
 {
 	struct optimized_kprobe *op;
+	int ret;
 
 	/*
 	 * Unused kprobe MUST be on the way of delayed unoptimizing (means
@@ -713,8 +714,12 @@ static void reuse_unused_kprobe(struct kprobe *ap)
 	/* Enable the probe again */
 	ap->flags &= ~KPROBE_FLAG_DISABLED;
 	/* Optimize it again (remove from op->list) */
-	BUG_ON(!kprobe_optready(ap));
+	ret = kprobe_optready(ap);
+	if (ret)
+		return ret;
+
 	optimize_kprobe(ap);
+	return 0;
 }
 
 /* Remove optimized instructions */
@@ -939,11 +944,16 @@ static void __disarm_kprobe(struct kprobe *p, bool reopt)
 #define kprobe_disarmed(p)			kprobe_disabled(p)
 #define wait_for_kprobe_optimizer()		do {} while (0)
 
-/* There should be no unused kprobes can be reused without optimization */
-static void reuse_unused_kprobe(struct kprobe *ap)
+static int reuse_unused_kprobe(struct kprobe *ap)
 {
+	/*
+	 * If the optimized kprobe is NOT supported, the aggr kprobe is
+	 * released at the same time that the last aggregated kprobe is
+	 * unregistered.
+	 * Thus there should be no chance to reuse unused kprobe.
+	 */
 	printk(KERN_ERR "Error: There should be no unused kprobe here.\n");
-	BUG_ON(kprobe_unused(ap));
+	return -EINVAL;
 }
 
 static void free_aggr_kprobe(struct kprobe *p)
@@ -1315,9 +1325,12 @@ static int register_aggr_kprobe(struct kprobe *orig_p, struct kprobe *p)
 			goto out;
 		}
 		init_aggr_kprobe(ap, orig_p);
-	} else if (kprobe_unused(ap))
+	} else if (kprobe_unused(ap)) {
 		/* This probe is going to die. Rescue it */
-		reuse_unused_kprobe(ap);
+		ret = reuse_unused_kprobe(ap);
+		if (ret)
+			goto out;
+	}
 
 	if (kprobe_gone(ap)) {
 		/*


  parent reply index

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-11 10:18 [PATCH -tip v2 0/5] kprobes: Remove BUG_ON from kprobes Masami Hiramatsu
2018-09-11 10:19 ` [PATCH -tip v2 1/5] kprobes: Remove meaningless BUG_ON from disarming process Masami Hiramatsu
2018-09-12  6:51   ` [tip:perf/core] kprobes: Remove pointless BUG_ON() " tip-bot for Masami Hiramatsu
2018-09-11 10:19 ` [PATCH -tip v2 2/5] kprobes: Remove meaningless BUG_ON from add_new_kprobe Masami Hiramatsu
2018-09-12  6:52   ` [tip:perf/core] kprobes: Remove pointless BUG_ON() from add_new_kprobe() tip-bot for Masami Hiramatsu
2018-09-11 10:20 ` [PATCH -tip v2 3/5] kprobes: Remove meaningless BUG_ON from reuse_unused_kprobe Masami Hiramatsu
2018-09-12  6:52   ` [tip:perf/core] kprobes: Remove pointless BUG_ON() from reuse_unused_kprobe() tip-bot for Masami Hiramatsu
2018-09-11 10:20 ` Masami Hiramatsu [this message]
2018-09-12  6:53   ` [tip:perf/core] kprobes: Return error if we fail to reuse kprobe instead of BUG_ON() tip-bot for Masami Hiramatsu
2018-09-11 10:21 ` [PATCH -tip v2 5/5] kprobes: Don't call BUG_ON if there is a kprobe in use on free list Masami Hiramatsu
2018-09-12  6:54   ` [tip:perf/core] kprobes: Don't call BUG_ON() " tip-bot for Masami Hiramatsu

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