linux-kernel - [PATCH 7/7] kprobes: Support probing module _

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Message-ID: <4919F1C6.4030106@redhat.com>
Date:	Tue, 11 Nov 2008 15:57:42 -0500
From:	Masami Hiramatsu <mhiramat@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Jim Keniston <jkenisto@...ibm.com>,
	David Miller <davem@...emloft.net>,
	LKML <linux-kernel@...r.kernel.org>,
	systemtap-ml <systemtap@...rces.redhat.com>,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: [PATCH 7/7] kprobes: Support probing module __init function

Allow kprobes to probe module __init routines.
When __init functions are freed, kprobes which probe those functions
are set to "Gone" flag. These "Gone" probes are disarmed from the code
and never be enabled.

Signed-off-by: Masami Hiramatsu <mhiramat@...hat.com>
---
 kernel/kprobes.c |   23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

Index: 2.6.28-rc4/kernel/kprobes.c
===================================================================
--- 2.6.28-rc4.orig/kernel/kprobes.c
+++ 2.6.28-rc4/kernel/kprobes.c
@@ -676,6 +676,16 @@ int __kprobes register_kprobe(struct kpr
 			preempt_enable();
 			return -EINVAL;
 		}
+		/*
+		 * If the module freed .init.text, we couldn't insert
+		 * kprobes in there.
+		 */
+		if (within_module_init((unsigned long)p->addr, probed_mod) &&
+		    probed_mod->state != MODULE_STATE_COMING) {
+			module_put(probed_mod);
+			preempt_enable();
+			return -EINVAL;
+		}
 	}
 	preempt_enable();

@@ -1072,19 +1082,24 @@ static int __kprobes kprobes_module_call
 	struct hlist_node *node;
 	struct kprobe *p;
 	unsigned int i;
+	int checkcore = (val == MODULE_STATE_GOING);

-	if (val != MODULE_STATE_GOING)
+	if (val != MODULE_STATE_GOING && val != MODULE_STATE_LIVE)
 		return NOTIFY_DONE;

 	/*
-	 * module .text section will be freed. We need to
-	 * disable kprobes which have been inserted in the section.
+	 * When MODULE_STATE_GOING was notified, both of module .text and
+	 * .init.text sections would be freed. When MODULE_STATE_LIVE was
+	 * notified, only .init.text section would be freed. We need to
+	 * disable kprobes which have been inserted in the sections.
 	 */
 	mutex_lock(&kprobe_mutex);
 	for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
 		head = &kprobe_table[i];
 		hlist_for_each_entry_rcu(p, node, head, hlist)
-			if (within_module_core((unsigned long)p->addr, mod)) {
+			if (within_module_init((unsigned long)p->addr, mod) ||
+			    (checkcore &&
+			     within_module_core((unsigned long)p->addr, mod))) {
 				/*
 				 * The vaddr this probe is installed will soon
 				 * be vfreed buy not synced to disk. Hence,

-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division

e-mail: mhiramat@...hat.com

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