1 files changed, 191 insertions, 0 deletions
diff --git a/runtime/task_finder_map.c b/runtime/task_finder_map.c
new file mode 100644
index 00000000..b770dd0e
--- /dev/null
+++ b/runtime/task_finder_map.c
@@ -0,0 +1,191 @@
+#include <linux/list.h>
+#include <linux/jhash.h>
+#include <linux/spinlock.h>
+
+// When handling mmap()/munmap()/mprotect() syscall tracing to notice
+// memory map changes, we need to cache syscall entry parameter values
+// for processing at syscall exit.
+
+// __stp_tf_map_lock protects the hash table.
+// Documentation/spinlocks.txt suggest we can be a bit more clever
+// if we guarantee that in interrupt context we only read, not write
+// the datastructures. We should never change the hash table or the
+// contents in interrupt context (which should only ever call 
+// stap_find_map_map_info for getting stored info). So we might
+// want to look into that if this seems a bottleneck.
+static DEFINE_RWLOCK(__stp_tf_map_lock);
+
+#define __STP_TF_HASH_BITS 4
+#define __STP_TF_TABLE_SIZE (1 << __STP_TF_HASH_BITS)
+
+#ifndef TASK_FINDER_MAP_ENTRY_ITEMS
+#define TASK_FINDER_MAP_ENTRY_ITEMS 100
+#endif
+
+struct __stp_tf_map_entry {
+/* private: */
+	struct hlist_node hlist;
+	int usage;
+
+/* public: */
+	pid_t pid;
+	long syscall_no;
+	unsigned long arg0;
+	unsigned long arg1;
+	unsigned long arg2;
+};
+
+static struct __stp_tf_map_entry
+__stp_tf_map_free_list_items[TASK_FINDER_MAP_ENTRY_ITEMS];
+
+static struct hlist_head __stp_tf_map_free_list[1];
+
+static struct hlist_head __stp_tf_map_table[__STP_TF_TABLE_SIZE];
+
+// __stp_tf_map_initialize():  Initialize the free list.  Grabs the
+// lock.
+static void
+__stp_tf_map_initialize(void)
+{
+	int i;
+	struct hlist_head *head = &__stp_tf_map_free_list[0];
+
+	unsigned long flags;
+	write_lock_irqsave(&__stp_tf_map_lock, flags);
+	for (i = 0; i < TASK_FINDER_MAP_ENTRY_ITEMS; i++) {
+		hlist_add_head(&__stp_tf_map_free_list_items[i].hlist, head);
+	}
+	write_unlock_irqrestore(&__stp_tf_map_lock, flags);
+}
+
+
+// __stp_tf_map_get_free_entry(): Returns an entry from the free list
+// or NULL.  The __stp_tf_map_lock must be write locked before calling this
+// function.
+static struct __stp_tf_map_entry *
+__stp_tf_map_get_free_entry(void)
+{
+	struct hlist_head *head = &__stp_tf_map_free_list[0];
+	struct hlist_node *node;
+	struct __stp_tf_map_entry *entry = NULL;
+
+	if (hlist_empty(head))
+		return NULL;
+	hlist_for_each_entry(entry, node, head, hlist) {
+		break;
+	}
+	if (entry != NULL)
+		hlist_del(&entry->hlist);
+	return entry;
+}
+
+
+// __stp_tf_map_put_free_entry(): Puts an entry back on the free
+// list.  The __stp_tf_map_lock must be write locked before calling this
+// function.
+static void
+__stp_tf_map_put_free_entry(struct __stp_tf_map_entry *entry)
+{
+	struct hlist_head *head = &__stp_tf_map_free_list[0];
+	hlist_add_head(&entry->hlist, head);
+}
+
+
+// __stp_tf_map_hash(): Compute the map hash.
+static inline u32
+__stp_tf_map_hash(struct task_struct *tsk)
+{
+    return (jhash_1word(tsk->pid, 0) & (__STP_TF_TABLE_SIZE - 1));
+}
+
+
+// Get map_entry if the map is present in the map hash table.
+// Returns NULL if not present. Takes a read lock on __stp_tf_map_lock.
+static struct __stp_tf_map_entry *
+__stp_tf_get_map_entry(struct task_struct *tsk)
+{
+	struct hlist_head *head;
+	struct hlist_node *node;
+	struct __stp_tf_map_entry *entry;
+
+	unsigned long flags;
+	read_lock_irqsave(&__stp_tf_map_lock, flags);
+	head = &__stp_tf_map_table[__stp_tf_map_hash(tsk)];
+	hlist_for_each_entry(entry, node, head, hlist) {
+		if (tsk->pid == entry->pid) {
+			read_unlock_irqrestore(&__stp_tf_map_lock, flags);
+			return entry;
+		}
+	}
+	read_unlock_irqrestore(&__stp_tf_map_lock, flags);
+	return NULL;
+}
+
+
+// Add the map info to the map hash table. Takes a write lock on
+// __stp_tf_map_lock.
+static int
+__stp_tf_add_map(struct task_struct *tsk, long syscall_no, unsigned long arg0,
+		 unsigned long arg1, unsigned long arg2)
+{
+	struct hlist_head *head;
+	struct hlist_node *node;
+	struct __stp_tf_map_entry *entry;
+	unsigned long flags;
+
+	write_lock_irqsave(&__stp_tf_map_lock, flags);
+	head = &__stp_tf_map_table[__stp_tf_map_hash(tsk)];
+	hlist_for_each_entry(entry, node, head, hlist) {
+		// If we find an existing entry, just increment the
+		// usage count.
+		if (tsk->pid == entry->pid) {
+			entry->usage++;
+			write_unlock_irqrestore(&__stp_tf_map_lock, flags);
+			return 0;
+		}
+	}
+
+	// Get an element from the free list.
+	entry = __stp_tf_map_get_free_entry();
+	if (!entry) {
+		write_unlock_irqrestore(&__stp_tf_map_lock, flags);
+		return -ENOMEM;
+	}
+	entry->usage = 1;
+	entry->pid = tsk->pid;
+	entry->syscall_no = syscall_no;
+	entry->arg0 = arg0;
+	entry->arg1 = arg1;
+	entry->arg2 = arg2;
+	hlist_add_head(&entry->hlist, head);
+	write_unlock_irqrestore(&__stp_tf_map_lock, flags);
+	return 0;
+}
+
+
+// Remove the map entry from the map hash table. Takes a write lock on
+// __stp_tf_map_lock.
+static int
+__stp_tf_remove_map_entry(struct __stp_tf_map_entry *entry)
+{
+	struct hlist_head *head;
+	struct hlist_node *node;
+	int found = 0;
+
+	if (entry != NULL) {
+		unsigned long flags;
+		write_lock_irqsave(&__stp_tf_map_lock, flags);
+
+		// Decrement the usage count.
+		entry->usage--;
+
+		// If the entry is unused, put it back on the free
+		// list.
+		if (entry->usage == 0) {
+			hlist_del(&entry->hlist);
+			__stp_tf_map_put_free_entry(entry);
+		}
+		write_unlock_irqrestore(&__stp_tf_map_lock, flags);
+	}
+	return 0;
+}