[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>
diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index f20c163..99ddba5 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -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;
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index d8903e6..037142b7 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -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 = {