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@@ -0,0 +1,476 @@
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+/*
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+ * Copyright (C) 2008 Mathieu Desnoyers
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+ *
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+ * This program is free software; you can redistribute it and/or modify
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+ * it under the terms of the GNU General Public License as published by
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+ * the Free Software Foundation; either version 2 of the License, or
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+ * (at your option) any later version.
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+ *
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+ * This program is distributed in the hope that it will be useful,
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+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
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+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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+ * GNU General Public License for more details.
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+ *
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+ * You should have received a copy of the GNU General Public License
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+ * along with this program; if not, write to the Free Software
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+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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+ */
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+#include <linux/module.h>
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+#include <linux/mutex.h>
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+#include <linux/types.h>
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+#include <linux/jhash.h>
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+#include <linux/list.h>
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+#include <linux/rcupdate.h>
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+#include <linux/tracepoint.h>
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+#include <linux/err.h>
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+#include <linux/slab.h>
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+
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+extern struct tracepoint __start___tracepoints[];
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+extern struct tracepoint __stop___tracepoints[];
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+
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+/* Set to 1 to enable tracepoint debug output */
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+static const int tracepoint_debug;
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+
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+/*
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+ * tracepoints_mutex nests inside module_mutex. Tracepoints mutex protects the
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+ * builtin and module tracepoints and the hash table.
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+ */
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+static DEFINE_MUTEX(tracepoints_mutex);
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+
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+/*
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+ * Tracepoint hash table, containing the active tracepoints.
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+ * Protected by tracepoints_mutex.
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+ */
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+#define TRACEPOINT_HASH_BITS 6
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+#define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS)
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+
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+/*
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+ * Note about RCU :
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+ * It is used to to delay the free of multiple probes array until a quiescent
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+ * state is reached.
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+ * Tracepoint entries modifications are protected by the tracepoints_mutex.
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+ */
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+struct tracepoint_entry {
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+ struct hlist_node hlist;
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+ void **funcs;
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+ int refcount; /* Number of times armed. 0 if disarmed. */
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+ struct rcu_head rcu;
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+ void *oldptr;
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+ unsigned char rcu_pending:1;
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+ char name[0];
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+};
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+
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+static struct hlist_head tracepoint_table[TRACEPOINT_TABLE_SIZE];
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+
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+static void free_old_closure(struct rcu_head *head)
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+{
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+ struct tracepoint_entry *entry = container_of(head,
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+ struct tracepoint_entry, rcu);
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+ kfree(entry->oldptr);
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+ /* Make sure we free the data before setting the pending flag to 0 */
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+ smp_wmb();
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+ entry->rcu_pending = 0;
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+}
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+
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+static void tracepoint_entry_free_old(struct tracepoint_entry *entry, void *old)
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+{
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+ if (!old)
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+ return;
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+ entry->oldptr = old;
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+ entry->rcu_pending = 1;
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+ /* write rcu_pending before calling the RCU callback */
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+ smp_wmb();
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+#ifdef CONFIG_PREEMPT_RCU
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+ synchronize_sched(); /* Until we have the call_rcu_sched() */
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+#endif
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+ call_rcu(&entry->rcu, free_old_closure);
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+}
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+
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+static void debug_print_probes(struct tracepoint_entry *entry)
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+{
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+ int i;
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+
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+ if (!tracepoint_debug)
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+ return;
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+
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+ for (i = 0; entry->funcs[i]; i++)
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+ printk(KERN_DEBUG "Probe %d : %p\n", i, entry->funcs[i]);
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+}
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+
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+static void *
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+tracepoint_entry_add_probe(struct tracepoint_entry *entry, void *probe)
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+{
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+ int nr_probes = 0;
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+ void **old, **new;
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+
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+ WARN_ON(!probe);
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+
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+ debug_print_probes(entry);
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+ old = entry->funcs;
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+ if (old) {
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+ /* (N -> N+1), (N != 0, 1) probes */
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+ for (nr_probes = 0; old[nr_probes]; nr_probes++)
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+ if (old[nr_probes] == probe)
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+ return ERR_PTR(-EEXIST);
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+ }
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+ /* + 2 : one for new probe, one for NULL func */
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+ new = kzalloc((nr_probes + 2) * sizeof(void *), GFP_KERNEL);
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+ if (new == NULL)
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+ return ERR_PTR(-ENOMEM);
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+ if (old)
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+ memcpy(new, old, nr_probes * sizeof(void *));
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+ new[nr_probes] = probe;
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+ entry->refcount = nr_probes + 1;
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+ entry->funcs = new;
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+ debug_print_probes(entry);
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+ return old;
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+}
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+
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+static void *
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+tracepoint_entry_remove_probe(struct tracepoint_entry *entry, void *probe)
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+{
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+ int nr_probes = 0, nr_del = 0, i;
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+ void **old, **new;
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+
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+ old = entry->funcs;
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+
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+ debug_print_probes(entry);
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+ /* (N -> M), (N > 1, M >= 0) probes */
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+ for (nr_probes = 0; old[nr_probes]; nr_probes++) {
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+ if ((!probe || old[nr_probes] == probe))
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+ nr_del++;
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+ }
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+
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+ if (nr_probes - nr_del == 0) {
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+ /* N -> 0, (N > 1) */
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+ entry->funcs = NULL;
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+ entry->refcount = 0;
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+ debug_print_probes(entry);
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+ return old;
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+ } else {
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+ int j = 0;
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+ /* N -> M, (N > 1, M > 0) */
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+ /* + 1 for NULL */
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+ new = kzalloc((nr_probes - nr_del + 1)
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+ * sizeof(void *), GFP_KERNEL);
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+ if (new == NULL)
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+ return ERR_PTR(-ENOMEM);
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+ for (i = 0; old[i]; i++)
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+ if ((probe && old[i] != probe))
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+ new[j++] = old[i];
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+ entry->refcount = nr_probes - nr_del;
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+ entry->funcs = new;
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+ }
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+ debug_print_probes(entry);
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+ return old;
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+}
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+
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+/*
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+ * Get tracepoint if the tracepoint is present in the tracepoint hash table.
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+ * Must be called with tracepoints_mutex held.
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+ * Returns NULL if not present.
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+ */
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+static struct tracepoint_entry *get_tracepoint(const char *name)
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+{
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+ struct hlist_head *head;
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+ struct hlist_node *node;
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+ struct tracepoint_entry *e;
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+ u32 hash = jhash(name, strlen(name), 0);
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+
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+ head = &tracepoint_table[hash & ((1 << TRACEPOINT_HASH_BITS)-1)];
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+ hlist_for_each_entry(e, node, head, hlist) {
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+ if (!strcmp(name, e->name))
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+ return e;
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+ }
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+ return NULL;
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+}
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+
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+/*
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+ * Add the tracepoint to the tracepoint hash table. Must be called with
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+ * tracepoints_mutex held.
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+ */
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+static struct tracepoint_entry *add_tracepoint(const char *name)
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+{
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+ struct hlist_head *head;
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+ struct hlist_node *node;
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+ struct tracepoint_entry *e;
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+ size_t name_len = strlen(name) + 1;
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+ u32 hash = jhash(name, name_len-1, 0);
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+
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+ head = &tracepoint_table[hash & ((1 << TRACEPOINT_HASH_BITS)-1)];
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+ hlist_for_each_entry(e, node, head, hlist) {
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+ if (!strcmp(name, e->name)) {
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+ printk(KERN_NOTICE
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+ "tracepoint %s busy\n", name);
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+ return ERR_PTR(-EEXIST); /* Already there */
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+ }
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+ }
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+ /*
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+ * Using kmalloc here to allocate a variable length element. Could
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+ * cause some memory fragmentation if overused.
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+ */
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+ e = kmalloc(sizeof(struct tracepoint_entry) + name_len, GFP_KERNEL);
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+ if (!e)
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+ return ERR_PTR(-ENOMEM);
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+ memcpy(&e->name[0], name, name_len);
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+ e->funcs = NULL;
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+ e->refcount = 0;
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+ e->rcu_pending = 0;
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+ hlist_add_head(&e->hlist, head);
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+ return e;
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+}
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+
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+/*
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+ * Remove the tracepoint from the tracepoint hash table. Must be called with
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+ * mutex_lock held.
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+ */
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+static int remove_tracepoint(const char *name)
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+{
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+ struct hlist_head *head;
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+ struct hlist_node *node;
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+ struct tracepoint_entry *e;
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+ int found = 0;
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+ size_t len = strlen(name) + 1;
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+ u32 hash = jhash(name, len-1, 0);
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+
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+ head = &tracepoint_table[hash & ((1 << TRACEPOINT_HASH_BITS)-1)];
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+ hlist_for_each_entry(e, node, head, hlist) {
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+ if (!strcmp(name, e->name)) {
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+ found = 1;
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+ break;
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+ }
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+ }
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+ if (!found)
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+ return -ENOENT;
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+ if (e->refcount)
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+ return -EBUSY;
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+ hlist_del(&e->hlist);
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+ /* Make sure the call_rcu has been executed */
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+ if (e->rcu_pending)
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+ rcu_barrier();
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+ kfree(e);
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+ return 0;
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+}
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+
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+/*
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+ * Sets the probe callback corresponding to one tracepoint.
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+ */
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+static void set_tracepoint(struct tracepoint_entry **entry,
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+ struct tracepoint *elem, int active)
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+{
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+ WARN_ON(strcmp((*entry)->name, elem->name) != 0);
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+
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+ /*
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+ * rcu_assign_pointer has a smp_wmb() which makes sure that the new
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+ * probe callbacks array is consistent before setting a pointer to it.
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+ * This array is referenced by __DO_TRACE from
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+ * include/linux/tracepoints.h. A matching smp_read_barrier_depends()
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+ * is used.
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+ */
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+ rcu_assign_pointer(elem->funcs, (*entry)->funcs);
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+ elem->state = active;
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+}
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+
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+/*
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+ * Disable a tracepoint and its probe callback.
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+ * Note: only waiting an RCU period after setting elem->call to the empty
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+ * function insures that the original callback is not used anymore. This insured
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+ * by preempt_disable around the call site.
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+ */
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+static void disable_tracepoint(struct tracepoint *elem)
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+{
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+ elem->state = 0;
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+}
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+
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+/**
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+ * tracepoint_update_probe_range - Update a probe range
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+ * @begin: beginning of the range
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+ * @end: end of the range
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+ *
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+ * Updates the probe callback corresponding to a range of tracepoints.
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+ */
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+void tracepoint_update_probe_range(struct tracepoint *begin,
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+ struct tracepoint *end)
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+{
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+ struct tracepoint *iter;
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+ struct tracepoint_entry *mark_entry;
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+
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+ mutex_lock(&tracepoints_mutex);
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+ for (iter = begin; iter < end; iter++) {
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+ mark_entry = get_tracepoint(iter->name);
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+ if (mark_entry) {
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+ set_tracepoint(&mark_entry, iter,
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+ !!mark_entry->refcount);
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+ } else {
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+ disable_tracepoint(iter);
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+ }
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+ }
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+ mutex_unlock(&tracepoints_mutex);
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+}
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+
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+/*
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+ * Update probes, removing the faulty probes.
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+ */
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+static void tracepoint_update_probes(void)
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+{
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+ /* Core kernel tracepoints */
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+ tracepoint_update_probe_range(__start___tracepoints,
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+ __stop___tracepoints);
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+ /* tracepoints in modules. */
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+ module_update_tracepoints();
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+}
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+
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+/**
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+ * tracepoint_probe_register - Connect a probe to a tracepoint
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+ * @name: tracepoint name
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+ * @probe: probe handler
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+ *
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+ * Returns 0 if ok, error value on error.
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+ * The probe address must at least be aligned on the architecture pointer size.
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+ */
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+int tracepoint_probe_register(const char *name, void *probe)
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+{
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+ struct tracepoint_entry *entry;
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+ int ret = 0;
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+ void *old;
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+
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+ mutex_lock(&tracepoints_mutex);
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+ entry = get_tracepoint(name);
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+ if (!entry) {
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+ entry = add_tracepoint(name);
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+ if (IS_ERR(entry)) {
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+ ret = PTR_ERR(entry);
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+ goto end;
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+ }
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+ }
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+ /*
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+ * If we detect that a call_rcu is pending for this tracepoint,
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+ * make sure it's executed now.
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+ */
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+ if (entry->rcu_pending)
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+ rcu_barrier();
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+ old = tracepoint_entry_add_probe(entry, probe);
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+ if (IS_ERR(old)) {
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+ ret = PTR_ERR(old);
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+ goto end;
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+ }
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+ mutex_unlock(&tracepoints_mutex);
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+ tracepoint_update_probes(); /* may update entry */
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+ mutex_lock(&tracepoints_mutex);
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+ entry = get_tracepoint(name);
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+ WARN_ON(!entry);
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+ tracepoint_entry_free_old(entry, old);
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+end:
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+ mutex_unlock(&tracepoints_mutex);
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+ return ret;
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+}
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+EXPORT_SYMBOL_GPL(tracepoint_probe_register);
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+
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+/**
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+ * tracepoint_probe_unregister - Disconnect a probe from a tracepoint
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+ * @name: tracepoint name
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+ * @probe: probe function pointer
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+ *
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+ * We do not need to call a synchronize_sched to make sure the probes have
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+ * finished running before doing a module unload, because the module unload
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+ * itself uses stop_machine(), which insures that every preempt disabled section
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+ * have finished.
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+ */
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+int tracepoint_probe_unregister(const char *name, void *probe)
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+{
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+ struct tracepoint_entry *entry;
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+ void *old;
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+ int ret = -ENOENT;
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+
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+ mutex_lock(&tracepoints_mutex);
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+ entry = get_tracepoint(name);
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+ if (!entry)
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+ goto end;
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+ if (entry->rcu_pending)
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+ rcu_barrier();
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+ old = tracepoint_entry_remove_probe(entry, probe);
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+ mutex_unlock(&tracepoints_mutex);
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+ tracepoint_update_probes(); /* may update entry */
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+ mutex_lock(&tracepoints_mutex);
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+ entry = get_tracepoint(name);
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+ if (!entry)
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+ goto end;
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+ tracepoint_entry_free_old(entry, old);
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+ remove_tracepoint(name); /* Ignore busy error message */
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+ ret = 0;
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+end:
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+ mutex_unlock(&tracepoints_mutex);
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+ return ret;
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+}
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+EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);
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+
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+/**
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+ * tracepoint_get_iter_range - Get a next tracepoint iterator given a range.
|
|
|
+ * @tracepoint: current tracepoints (in), next tracepoint (out)
|
|
|
+ * @begin: beginning of the range
|
|
|
+ * @end: end of the range
|
|
|
+ *
|
|
|
+ * Returns whether a next tracepoint has been found (1) or not (0).
|
|
|
+ * Will return the first tracepoint in the range if the input tracepoint is
|
|
|
+ * NULL.
|
|
|
+ */
|
|
|
+int tracepoint_get_iter_range(struct tracepoint **tracepoint,
|
|
|
+ struct tracepoint *begin, struct tracepoint *end)
|
|
|
+{
|
|
|
+ if (!*tracepoint && begin != end) {
|
|
|
+ *tracepoint = begin;
|
|
|
+ return 1;
|
|
|
+ }
|
|
|
+ if (*tracepoint >= begin && *tracepoint < end)
|
|
|
+ return 1;
|
|
|
+ return 0;
|
|
|
+}
|
|
|
+EXPORT_SYMBOL_GPL(tracepoint_get_iter_range);
|
|
|
+
|
|
|
+static void tracepoint_get_iter(struct tracepoint_iter *iter)
|
|
|
+{
|
|
|
+ int found = 0;
|
|
|
+
|
|
|
+ /* Core kernel tracepoints */
|
|
|
+ if (!iter->module) {
|
|
|
+ found = tracepoint_get_iter_range(&iter->tracepoint,
|
|
|
+ __start___tracepoints, __stop___tracepoints);
|
|
|
+ if (found)
|
|
|
+ goto end;
|
|
|
+ }
|
|
|
+ /* tracepoints in modules. */
|
|
|
+ found = module_get_iter_tracepoints(iter);
|
|
|
+end:
|
|
|
+ if (!found)
|
|
|
+ tracepoint_iter_reset(iter);
|
|
|
+}
|
|
|
+
|
|
|
+void tracepoint_iter_start(struct tracepoint_iter *iter)
|
|
|
+{
|
|
|
+ tracepoint_get_iter(iter);
|
|
|
+}
|
|
|
+EXPORT_SYMBOL_GPL(tracepoint_iter_start);
|
|
|
+
|
|
|
+void tracepoint_iter_next(struct tracepoint_iter *iter)
|
|
|
+{
|
|
|
+ iter->tracepoint++;
|
|
|
+ /*
|
|
|
+ * iter->tracepoint may be invalid because we blindly incremented it.
|
|
|
+ * Make sure it is valid by marshalling on the tracepoints, getting the
|
|
|
+ * tracepoints from following modules if necessary.
|
|
|
+ */
|
|
|
+ tracepoint_get_iter(iter);
|
|
|
+}
|
|
|
+EXPORT_SYMBOL_GPL(tracepoint_iter_next);
|
|
|
+
|
|
|
+void tracepoint_iter_stop(struct tracepoint_iter *iter)
|
|
|
+{
|
|
|
+}
|
|
|
+EXPORT_SYMBOL_GPL(tracepoint_iter_stop);
|
|
|
+
|
|
|
+void tracepoint_iter_reset(struct tracepoint_iter *iter)
|
|
|
+{
|
|
|
+ iter->module = NULL;
|
|
|
+ iter->tracepoint = NULL;
|
|
|
+}
|
|
|
+EXPORT_SYMBOL_GPL(tracepoint_iter_reset);
|
Mathieu Desnoyers