[PATCH] kprobes: Allow multiple kprobes at the same address

Allow registration of multiple kprobes at an address in an architecture agnostic way. Corresponding handlers will be invoked in a sequence. But, a kprobe and a jprobe can't (yet) co-exist at the same address. Signed-off-by: Ananth N Mavinakayanahalli <amavin@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] kprobes: Allow multiple kprobes at the same address
Allow registration of multiple kprobes at an address in an architecture agnostic way. Corresponding handlers will be invoked in a sequence. But, a kprobe and a jprobe can't (yet) co-exist at the same address. Signed-off-by: Ananth N Mavinakayanahalli <amavin@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Ananth N Mavinakayanahalli · Linus Torvalds
1 parent 04dea5f932
Showing 2 changed files with 134 additions and 13 deletions Side-by-side Diff
include/linux/kprobes.h
kernel/kprobes.c
@@ -43,6 +43,9 @@
 struct kprobe {
 	struct hlist_node hlist;
  
+	/* list of kprobes for multi-handler support */
+	struct list_head list;
+
 	/* location of the probe point */
 	kprobe_opcode_t *addr;
  
@@ -44,6 +44,7 @@
  
 unsigned int kprobe_cpu = NR_CPUS;
 static DEFINE_SPINLOCK(kprobe_lock);
+static struct kprobe *curr_kprobe;
  
 /* Locks kprobe: irqs must be disabled */
 void lock_kprobes(void)
  
  
  
  
@@ -73,22 +74,139 @@
 	return NULL;
 }
  
+/*
+ * Aggregate handlers for multiple kprobes support - these handlers
+ * take care of invoking the individual kprobe handlers on p->list
+ */
+int aggr_pre_handler(struct kprobe *p, struct pt_regs *regs)
+{
+	struct kprobe *kp;
+
+	list_for_each_entry(kp, &p->list, list) {
+		if (kp->pre_handler) {
+			curr_kprobe = kp;
+			kp->pre_handler(kp, regs);
+			curr_kprobe = NULL;
+		}
+	}
+	return 0;
+}
+
+void aggr_post_handler(struct kprobe *p, struct pt_regs *regs,
+		unsigned long flags)
+{
+	struct kprobe *kp;
+
+	list_for_each_entry(kp, &p->list, list) {
+		if (kp->post_handler) {
+			curr_kprobe = kp;
+			kp->post_handler(kp, regs, flags);
+			curr_kprobe = NULL;
+		}
+	}
+	return;
+}
+
+int aggr_fault_handler(struct kprobe *p, struct pt_regs *regs, int trapnr)
+{
+	/*
+	 * if we faulted "during" the execution of a user specified
+	 * probe handler, invoke just that probe's fault handler
+	 */
+	if (curr_kprobe && curr_kprobe->fault_handler) {
+		if (curr_kprobe->fault_handler(curr_kprobe, regs, trapnr))
+			return 1;
+	}
+	return 0;
+}
+
+/*
+ * Fill in the required fields of the "manager kprobe". Replace the
+ * earlier kprobe in the hlist with the manager kprobe
+ */
+static inline void add_aggr_kprobe(struct kprobe *ap, struct kprobe *p)
+{
+	ap->addr = p->addr;
+	ap->opcode = p->opcode;
+	memcpy(&ap->ainsn, &p->ainsn, sizeof(struct arch_specific_insn));
+
+	ap->pre_handler = aggr_pre_handler;
+	ap->post_handler = aggr_post_handler;
+	ap->fault_handler = aggr_fault_handler;
+
+	INIT_LIST_HEAD(&ap->list);
+	list_add(&p->list, &ap->list);
+
+	INIT_HLIST_NODE(&ap->hlist);
+	hlist_del(&p->hlist);
+	hlist_add_head(&ap->hlist,
+		&kprobe_table[hash_ptr(ap->addr, KPROBE_HASH_BITS)]);
+}
+
+/*
+ * This is the second or subsequent kprobe at the address - handle
+ * the intricacies
+ * TODO: Move kcalloc outside the spinlock
+ */
+static int register_aggr_kprobe(struct kprobe *old_p, struct kprobe *p)
+{
+	int ret = 0;
+	struct kprobe *ap;
+
+	if (old_p->break_handler || p->break_handler) {
+		ret = -EEXIST;	/* kprobe and jprobe can't (yet) coexist */
+	} else if (old_p->pre_handler == aggr_pre_handler) {
+		list_add(&p->list, &old_p->list);
+	} else {
+		ap = kcalloc(1, sizeof(struct kprobe), GFP_ATOMIC);
+		if (!ap)
+			return -ENOMEM;
+		add_aggr_kprobe(ap, old_p);
+		list_add(&p->list, &ap->list);
+	}
+	return ret;
+}
+
+/* kprobe removal house-keeping routines */
+static inline void cleanup_kprobe(struct kprobe *p, unsigned long flags)
+{
+	*p->addr = p->opcode;
+	hlist_del(&p->hlist);
+	flush_icache_range((unsigned long) p->addr,
+		   (unsigned long) p->addr + sizeof(kprobe_opcode_t));
+	spin_unlock_irqrestore(&kprobe_lock, flags);
+	arch_remove_kprobe(p);
+}
+
+static inline void cleanup_aggr_kprobe(struct kprobe *old_p,
+		struct kprobe *p, unsigned long flags)
+{
+	list_del(&p->list);
+	if (list_empty(&old_p->list)) {
+		cleanup_kprobe(old_p, flags);
+		kfree(old_p);
+	} else
+		spin_unlock_irqrestore(&kprobe_lock, flags);
+}
+
 int register_kprobe(struct kprobe *p)
 {
 	int ret = 0;
 	unsigned long flags = 0;
+	struct kprobe *old_p;
  
 	if ((ret = arch_prepare_kprobe(p)) != 0) {
 		goto rm_kprobe;
 	}
 	spin_lock_irqsave(&kprobe_lock, flags);
-	INIT_HLIST_NODE(&p->hlist);
-	if (get_kprobe(p->addr)) {
-		ret = -EEXIST;
+	old_p = get_kprobe(p->addr);
+	if (old_p) {
+		ret = register_aggr_kprobe(old_p, p);
 		goto out;
 	}
-	arch_copy_kprobe(p);
  
+	arch_copy_kprobe(p);
+	INIT_HLIST_NODE(&p->hlist);
 	hlist_add_head(&p->hlist,
 		       &kprobe_table[hash_ptr(p->addr, KPROBE_HASH_BITS)]);
  
  
  
@@ -107,17 +225,17 @@
 void unregister_kprobe(struct kprobe *p)
 {
 	unsigned long flags;
+	struct kprobe *old_p;
+
 	spin_lock_irqsave(&kprobe_lock, flags);
-	if (!get_kprobe(p->addr)) {
+	old_p = get_kprobe(p->addr);
+	if (old_p) {
+		if (old_p->pre_handler == aggr_pre_handler)
+			cleanup_aggr_kprobe(old_p, p, flags);
+		else
+			cleanup_kprobe(p, flags);
+	} else
 		spin_unlock_irqrestore(&kprobe_lock, flags);
-		return;
-	}
-	*p->addr = p->opcode;
-	hlist_del(&p->hlist);
-	flush_icache_range((unsigned long) p->addr,
-			   (unsigned long) p->addr + sizeof(kprobe_opcode_t));
-	spin_unlock_irqrestore(&kprobe_lock, flags);
-	arch_remove_kprobe(p);
 }
  
 static struct notifier_block kprobe_exceptions_nb = {
...	...	@@ -43,6 +43,9 @@
43	43	struct kprobe {
44	44	struct hlist_node hlist;
45	45
	46	+ /* list of kprobes for multi-handler support */
	47	+ struct list_head list;
	48	+
46	49	/* location of the probe point */
47	50	kprobe_opcode_t *addr;
48	51
...	...	@@ -44,6 +44,7 @@
44	44
45	45	unsigned int kprobe_cpu = NR_CPUS;
46	46	static DEFINE_SPINLOCK(kprobe_lock);
	47	+static struct kprobe *curr_kprobe;
47	48
48	49	/* Locks kprobe: irqs must be disabled */
49	50	void lock_kprobes(void)
50	51
51	52
52	53
53	54
...	...	@@ -73,22 +74,139 @@
73	74	return NULL;
74	75	}
75	76
	77	+/*
	78	+ * Aggregate handlers for multiple kprobes support - these handlers
	79	+ * take care of invoking the individual kprobe handlers on p->list
	80	+ */
	81	+int aggr_pre_handler(struct kprobe p, struct pt_regs regs)
	82	+{
	83	+ struct kprobe *kp;
	84	+
	85	+ list_for_each_entry(kp, &p->list, list) {
	86	+ if (kp->pre_handler) {
	87	+ curr_kprobe = kp;
	88	+ kp->pre_handler(kp, regs);
	89	+ curr_kprobe = NULL;
	90	+ }
	91	+ }
	92	+ return 0;
	93	+}
	94	+
	95	+void aggr_post_handler(struct kprobe p, struct pt_regs regs,
	96	+ unsigned long flags)
	97	+{
	98	+ struct kprobe *kp;
	99	+
	100	+ list_for_each_entry(kp, &p->list, list) {
	101	+ if (kp->post_handler) {
	102	+ curr_kprobe = kp;
	103	+ kp->post_handler(kp, regs, flags);
	104	+ curr_kprobe = NULL;
	105	+ }
	106	+ }
	107	+ return;
	108	+}
	109	+
	110	+int aggr_fault_handler(struct kprobe p, struct pt_regs regs, int trapnr)
	111	+{
	112	+ /*
	113	+ * if we faulted "during" the execution of a user specified
	114	+ * probe handler, invoke just that probe's fault handler
	115	+ */
	116	+ if (curr_kprobe && curr_kprobe->fault_handler) {
	117	+ if (curr_kprobe->fault_handler(curr_kprobe, regs, trapnr))
	118	+ return 1;
	119	+ }
	120	+ return 0;
	121	+}
	122	+
	123	+/*
	124	+ * Fill in the required fields of the "manager kprobe". Replace the
	125	+ * earlier kprobe in the hlist with the manager kprobe
	126	+ */
	127	+static inline void add_aggr_kprobe(struct kprobe ap, struct kprobe p)
	128	+{
	129	+ ap->addr = p->addr;
	130	+ ap->opcode = p->opcode;
	131	+ memcpy(&ap->ainsn, &p->ainsn, sizeof(struct arch_specific_insn));
	132	+
	133	+ ap->pre_handler = aggr_pre_handler;
	134	+ ap->post_handler = aggr_post_handler;
	135	+ ap->fault_handler = aggr_fault_handler;
	136	+
	137	+ INIT_LIST_HEAD(&ap->list);
	138	+ list_add(&p->list, &ap->list);
	139	+
	140	+ INIT_HLIST_NODE(&ap->hlist);
	141	+ hlist_del(&p->hlist);
	142	+ hlist_add_head(&ap->hlist,
	143	+ &kprobe_table[hash_ptr(ap->addr, KPROBE_HASH_BITS)]);
	144	+}
	145	+
	146	+/*
	147	+ * This is the second or subsequent kprobe at the address - handle
	148	+ * the intricacies
	149	+ * TODO: Move kcalloc outside the spinlock
	150	+ */
	151	+static int register_aggr_kprobe(struct kprobe old_p, struct kprobe p)
	152	+{
	153	+ int ret = 0;
	154	+ struct kprobe *ap;
	155	+
	156	+ if (old_p->break_handler \|\| p->break_handler) {
	157	+ ret = -EEXIST; /* kprobe and jprobe can't (yet) coexist */
	158	+ } else if (old_p->pre_handler == aggr_pre_handler) {
	159	+ list_add(&p->list, &old_p->list);
	160	+ } else {
	161	+ ap = kcalloc(1, sizeof(struct kprobe), GFP_ATOMIC);
	162	+ if (!ap)
	163	+ return -ENOMEM;
	164	+ add_aggr_kprobe(ap, old_p);
	165	+ list_add(&p->list, &ap->list);
	166	+ }
	167	+ return ret;
	168	+}
	169	+
	170	+/* kprobe removal house-keeping routines */
	171	+static inline void cleanup_kprobe(struct kprobe *p, unsigned long flags)
	172	+{
	173	+ *p->addr = p->opcode;
	174	+ hlist_del(&p->hlist);
	175	+ flush_icache_range((unsigned long) p->addr,
	176	+ (unsigned long) p->addr + sizeof(kprobe_opcode_t));
	177	+ spin_unlock_irqrestore(&kprobe_lock, flags);
	178	+ arch_remove_kprobe(p);
	179	+}
	180	+
	181	+static inline void cleanup_aggr_kprobe(struct kprobe *old_p,
	182	+ struct kprobe *p, unsigned long flags)
	183	+{
	184	+ list_del(&p->list);
	185	+ if (list_empty(&old_p->list)) {
	186	+ cleanup_kprobe(old_p, flags);
	187	+ kfree(old_p);
	188	+ } else
	189	+ spin_unlock_irqrestore(&kprobe_lock, flags);
	190	+}
	191	+
76	192	int register_kprobe(struct kprobe *p)
77	193	{
78	194	int ret = 0;
79	195	unsigned long flags = 0;
	196	+ struct kprobe *old_p;
80	197
81	198	if ((ret = arch_prepare_kprobe(p)) != 0) {
82	199	goto rm_kprobe;
83	200	}
84	201	spin_lock_irqsave(&kprobe_lock, flags);
85		- INIT_HLIST_NODE(&p->hlist);
86		- if (get_kprobe(p->addr)) {
87		- ret = -EEXIST;
	202	+ old_p = get_kprobe(p->addr);
	203	+ if (old_p) {
	204	+ ret = register_aggr_kprobe(old_p, p);
88	205	goto out;
89	206	}
90		- arch_copy_kprobe(p);
91	207
	208	+ arch_copy_kprobe(p);
	209	+ INIT_HLIST_NODE(&p->hlist);
92	210	hlist_add_head(&p->hlist,
93	211	&kprobe_table[hash_ptr(p->addr, KPROBE_HASH_BITS)]);
94	212
95	213
96	214
...	...	@@ -107,17 +225,17 @@
107	225	void unregister_kprobe(struct kprobe *p)
108	226	{
109	227	unsigned long flags;
	228	+ struct kprobe *old_p;
	229	+
110	230	spin_lock_irqsave(&kprobe_lock, flags);
111		- if (!get_kprobe(p->addr)) {
	231	+ old_p = get_kprobe(p->addr);
	232	+ if (old_p) {
	233	+ if (old_p->pre_handler == aggr_pre_handler)
	234	+ cleanup_aggr_kprobe(old_p, p, flags);
	235	+ else
	236	+ cleanup_kprobe(p, flags);
	237	+ } else
112	238	spin_unlock_irqrestore(&kprobe_lock, flags);
113		- return;
114		- }
115		- *p->addr = p->opcode;
116		- hlist_del(&p->hlist);
117		- flush_icache_range((unsigned long) p->addr,
118		- (unsigned long) p->addr + sizeof(kprobe_opcode_t));
119		- spin_unlock_irqrestore(&kprobe_lock, flags);
120		- arch_remove_kprobe(p);
121	239	}
122	240
123	241	static struct notifier_block kprobe_exceptions_nb = {