--- /dev/null
+/*
+ * Copyright (C) 2008-2011 Mathieu Desnoyers
+ * Copyright (C) 2009 Pierre-Marc Fournier
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation;
+ * version 2.1 of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ *
+ * Ported to userspace by Pierre-Marc Fournier.
+ */
+
+#define _LGPL_SOURCE
+#include <errno.h>
+#include <lttng/tracepoint.h>
+#include <lttng/tracepoint-internal.h>
+#include <lttng/core.h>
+#include <lttng/kcompat/kcompat.h>
+#include <urcu-bp.h>
+#include <urcu/hlist.h>
+#include <urcu/uatomic.h>
+
+#include <lttng/usterr-signal-safe.h>
+#include "ltt-tracer-core.h"
+
+/* Set to 1 to enable tracepoint debug output */
+static const int tracepoint_debug;
+static int initialized;
+static void (*new_tracepoint_cb)(struct tracepoint *);
+
+/* libraries that contain tracepoints (struct tracepoint_lib) */
+static CDS_LIST_HEAD(libs);
+
+/*
+ * The UST lock protects the library tracepoints, the hash table, and
+ * the library list.
+ * All calls to the tracepoint API must be protected by the UST lock,
+ * excepts calls to tracepoint_register_lib and
+ * tracepoint_unregister_lib, which take the UST lock themselves.
+ */
+
+/*
+ * Tracepoint hash table, containing the active tracepoints.
+ * Protected by tracepoints_mutex.
+ */
+#define TRACEPOINT_HASH_BITS 6
+#define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS)
+static struct cds_hlist_head tracepoint_table[TRACEPOINT_TABLE_SIZE];
+
+static CDS_LIST_HEAD(old_probes);
+static int need_update;
+
+/*
+ * Note about RCU :
+ * It is used to to delay the free of multiple probes array until a quiescent
+ * state is reached.
+ * Tracepoint entries modifications are protected by the tracepoints_mutex.
+ */
+struct tracepoint_entry {
+ struct cds_hlist_node hlist;
+ struct tracepoint_probe *probes;
+ int refcount; /* Number of times armed. 0 if disarmed. */
+ char name[0];
+};
+
+struct tp_probes {
+ union {
+ struct cds_list_head list;
+ } u;
+ struct tracepoint_probe probes[0];
+};
+
+static inline void *allocate_probes(int count)
+{
+ struct tp_probes *p = zmalloc(count * sizeof(struct tracepoint_probe)
+ + sizeof(struct tp_probes));
+ return p == NULL ? NULL : p->probes;
+}
+
+static inline void release_probes(void *old)
+{
+ if (old) {
+ struct tp_probes *tp_probes = _ust_container_of(old,
+ struct tp_probes, probes[0]);
+ synchronize_rcu();
+ free(tp_probes);
+ }
+}
+
+static void debug_print_probes(struct tracepoint_entry *entry)
+{
+ int i;
+
+ if (!tracepoint_debug || !entry->probes)
+ return;
+
+ for (i = 0; entry->probes[i].func; i++)
+ DBG("Probe %d : %p", i, entry->probes[i].func);
+}
+
+static void *
+tracepoint_entry_add_probe(struct tracepoint_entry *entry,
+ void *probe, void *data)
+{
+ int nr_probes = 0;
+ struct tracepoint_probe *old, *new;
+
+ WARN_ON(!probe);
+
+ debug_print_probes(entry);
+ old = entry->probes;
+ if (old) {
+ /* (N -> N+1), (N != 0, 1) probes */
+ for (nr_probes = 0; old[nr_probes].func; nr_probes++)
+ if (old[nr_probes].func == probe &&
+ old[nr_probes].data == data)
+ return ERR_PTR(-EEXIST);
+ }
+ /* + 2 : one for new probe, one for NULL func */
+ new = allocate_probes(nr_probes + 2);
+ if (new == NULL)
+ return ERR_PTR(-ENOMEM);
+ if (old)
+ memcpy(new, old, nr_probes * sizeof(struct tracepoint_probe));
+ new[nr_probes].func = probe;
+ new[nr_probes].data = data;
+ new[nr_probes + 1].func = NULL;
+ entry->refcount = nr_probes + 1;
+ entry->probes = new;
+ debug_print_probes(entry);
+ return old;
+}
+
+static void *
+tracepoint_entry_remove_probe(struct tracepoint_entry *entry, void *probe,
+ void *data)
+{
+ int nr_probes = 0, nr_del = 0, i;
+ struct tracepoint_probe *old, *new;
+
+ old = entry->probes;
+
+ if (!old)
+ return ERR_PTR(-ENOENT);
+
+ debug_print_probes(entry);
+ /* (N -> M), (N > 1, M >= 0) probes */
+ for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
+ if (!probe ||
+ (old[nr_probes].func == probe &&
+ old[nr_probes].data == data))
+ nr_del++;
+ }
+
+ if (nr_probes - nr_del == 0) {
+ /* N -> 0, (N > 1) */
+ entry->probes = NULL;
+ entry->refcount = 0;
+ debug_print_probes(entry);
+ return old;
+ } else {
+ int j = 0;
+ /* N -> M, (N > 1, M > 0) */
+ /* + 1 for NULL */
+ new = allocate_probes(nr_probes - nr_del + 1);
+ if (new == NULL)
+ return ERR_PTR(-ENOMEM);
+ for (i = 0; old[i].func; i++)
+ if (probe &&
+ (old[i].func != probe || old[i].data != data))
+ new[j++] = old[i];
+ new[nr_probes - nr_del].func = NULL;
+ entry->refcount = nr_probes - nr_del;
+ entry->probes = new;
+ }
+ debug_print_probes(entry);
+ return old;
+}
+
+/*
+ * Get tracepoint if the tracepoint is present in the tracepoint hash table.
+ * Must be called with tracepoints_mutex held.
+ * Returns NULL if not present.
+ */
+static struct tracepoint_entry *get_tracepoint(const char *name)
+{
+ struct cds_hlist_head *head;
+ struct cds_hlist_node *node;
+ struct tracepoint_entry *e;
+ u32 hash = jhash(name, strlen(name), 0);
+
+ head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
+ cds_hlist_for_each_entry(e, node, head, hlist) {
+ if (!strcmp(name, e->name))
+ return e;
+ }
+ return NULL;
+}
+
+/*
+ * Add the tracepoint to the tracepoint hash table. Must be called with
+ * tracepoints_mutex held.
+ */
+static struct tracepoint_entry *add_tracepoint(const char *name)
+{
+ struct cds_hlist_head *head;
+ struct cds_hlist_node *node;
+ struct tracepoint_entry *e;
+ size_t name_len = strlen(name) + 1;
+ u32 hash = jhash(name, name_len-1, 0);
+
+ head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
+ cds_hlist_for_each_entry(e, node, head, hlist) {
+ if (!strcmp(name, e->name)) {
+ DBG("tracepoint %s busy", name);
+ return ERR_PTR(-EEXIST); /* Already there */
+ }
+ }
+ /*
+ * Using zmalloc here to allocate a variable length element. Could
+ * cause some memory fragmentation if overused.
+ */
+ e = zmalloc(sizeof(struct tracepoint_entry) + name_len);
+ if (!e)
+ return ERR_PTR(-ENOMEM);
+ memcpy(&e->name[0], name, name_len);
+ e->probes = NULL;
+ e->refcount = 0;
+ cds_hlist_add_head(&e->hlist, head);
+ return e;
+}
+
+/*
+ * Remove the tracepoint from the tracepoint hash table. Must be called with
+ * ust_lock held.
+ */
+static inline void remove_tracepoint(struct tracepoint_entry *e)
+{
+ cds_hlist_del(&e->hlist);
+ free(e);
+}
+
+/*
+ * Sets the probe callback corresponding to one tracepoint.
+ */
+static void set_tracepoint(struct tracepoint_entry **entry,
+ struct tracepoint *elem, int active)
+{
+ WARN_ON(strcmp((*entry)->name, elem->name) != 0);
+
+ /*
+ * rcu_assign_pointer has a cmm_smp_wmb() which makes sure that the new
+ * probe callbacks array is consistent before setting a pointer to it.
+ * This array is referenced by __DO_TRACE from
+ * include/linux/tracepoints.h. A matching cmm_smp_read_barrier_depends()
+ * is used.
+ */
+ rcu_assign_pointer(elem->probes, (*entry)->probes);
+ elem->state = active;
+}
+
+/*
+ * Disable a tracepoint and its probe callback.
+ * Note: only waiting an RCU period after setting elem->call to the empty
+ * function insures that the original callback is not used anymore. This insured
+ * by preempt_disable around the call site.
+ */
+static void disable_tracepoint(struct tracepoint *elem)
+{
+ elem->state = 0;
+ rcu_assign_pointer(elem->probes, NULL);
+}
+
+/**
+ * tracepoint_update_probe_range - Update a probe range
+ * @begin: beginning of the range
+ * @end: end of the range
+ *
+ * Updates the probe callback corresponding to a range of tracepoints.
+ */
+static
+void tracepoint_update_probe_range(struct tracepoint * const *begin,
+ struct tracepoint * const *end)
+{
+ struct tracepoint * const *iter;
+ struct tracepoint_entry *mark_entry;
+
+ for (iter = begin; iter < end; iter++) {
+ if (!*iter)
+ continue; /* skip dummy */
+ if (!(*iter)->name) {
+ disable_tracepoint(*iter);
+ continue;
+ }
+ mark_entry = get_tracepoint((*iter)->name);
+ if (mark_entry) {
+ set_tracepoint(&mark_entry, *iter,
+ !!mark_entry->refcount);
+ } else {
+ disable_tracepoint(*iter);
+ }
+ }
+}
+
+static void lib_update_tracepoints(void)
+{
+ struct tracepoint_lib *lib;
+
+ cds_list_for_each_entry(lib, &libs, list) {
+ tracepoint_update_probe_range(lib->tracepoints_start,
+ lib->tracepoints_start + lib->tracepoints_count);
+ }
+}
+
+/*
+ * Update probes, removing the faulty probes.
+ */
+static void tracepoint_update_probes(void)
+{
+ /* tracepoints registered from libraries and executable. */
+ lib_update_tracepoints();
+}
+
+static struct tracepoint_probe *
+tracepoint_add_probe(const char *name, void *probe, void *data)
+{
+ struct tracepoint_entry *entry;
+ struct tracepoint_probe *old;
+
+ entry = get_tracepoint(name);
+ if (!entry) {
+ entry = add_tracepoint(name);
+ if (IS_ERR(entry))
+ return (struct tracepoint_probe *)entry;
+ }
+ old = tracepoint_entry_add_probe(entry, probe, data);
+ if (IS_ERR(old) && !entry->refcount)
+ remove_tracepoint(entry);
+ return old;
+}
+
+/**
+ * __tracepoint_probe_register - Connect a probe to a tracepoint
+ * @name: tracepoint name
+ * @probe: probe handler
+ *
+ * Returns 0 if ok, error value on error.
+ * The probe address must at least be aligned on the architecture pointer size.
+ * Called with the UST lock held.
+ */
+int __tracepoint_probe_register(const char *name, void *probe, void *data)
+{
+ void *old;
+
+ old = tracepoint_add_probe(name, probe, data);
+ if (IS_ERR(old))
+ return PTR_ERR(old);
+
+ tracepoint_update_probes(); /* may update entry */
+ release_probes(old);
+ return 0;
+}
+
+static void *tracepoint_remove_probe(const char *name, void *probe, void *data)
+{
+ struct tracepoint_entry *entry;
+ void *old;
+
+ entry = get_tracepoint(name);
+ if (!entry)
+ return ERR_PTR(-ENOENT);
+ old = tracepoint_entry_remove_probe(entry, probe, data);
+ if (IS_ERR(old))
+ return old;
+ if (!entry->refcount)
+ remove_tracepoint(entry);
+ return old;
+}
+
+/**
+ * tracepoint_probe_unregister - Disconnect a probe from a tracepoint
+ * @name: tracepoint name
+ * @probe: probe function pointer
+ * @probe: probe data pointer
+ *
+ * Called with the UST lock held.
+ */
+int __tracepoint_probe_unregister(const char *name, void *probe, void *data)
+{
+ void *old;
+
+ old = tracepoint_remove_probe(name, probe, data);
+ if (IS_ERR(old))
+ return PTR_ERR(old);
+
+ tracepoint_update_probes(); /* may update entry */
+ release_probes(old);
+ return 0;
+}
+
+static void tracepoint_add_old_probes(void *old)
+{
+ need_update = 1;
+ if (old) {
+ struct tp_probes *tp_probes = _ust_container_of(old,
+ struct tp_probes, probes[0]);
+ cds_list_add(&tp_probes->u.list, &old_probes);
+ }
+}
+
+/**
+ * tracepoint_probe_register_noupdate - register a probe but not connect
+ * @name: tracepoint name
+ * @probe: probe handler
+ *
+ * caller must call tracepoint_probe_update_all()
+ * Called with the UST lock held.
+ */
+int tracepoint_probe_register_noupdate(const char *name, void *probe,
+ void *data)
+{
+ void *old;
+
+ old = tracepoint_add_probe(name, probe, data);
+ if (IS_ERR(old)) {
+ return PTR_ERR(old);
+ }
+ tracepoint_add_old_probes(old);
+ return 0;
+}
+
+/**
+ * tracepoint_probe_unregister_noupdate - remove a probe but not disconnect
+ * @name: tracepoint name
+ * @probe: probe function pointer
+ *
+ * caller must call tracepoint_probe_update_all()
+ * Called with the UST lock held.
+ */
+int tracepoint_probe_unregister_noupdate(const char *name, void *probe,
+ void *data)
+{
+ void *old;
+
+ old = tracepoint_remove_probe(name, probe, data);
+ if (IS_ERR(old)) {
+ return PTR_ERR(old);
+ }
+ tracepoint_add_old_probes(old);
+ return 0;
+}
+
+/**
+ * tracepoint_probe_update_all - update tracepoints
+ * Called with the UST lock held.
+ */
+void tracepoint_probe_update_all(void)
+{
+ CDS_LIST_HEAD(release_probes);
+ struct tp_probes *pos, *next;
+
+ if (!need_update) {
+ return;
+ }
+ if (!cds_list_empty(&old_probes))
+ cds_list_replace_init(&old_probes, &release_probes);
+ need_update = 0;
+
+ tracepoint_update_probes();
+ cds_list_for_each_entry_safe(pos, next, &release_probes, u.list) {
+ cds_list_del(&pos->u.list);
+ synchronize_rcu();
+ free(pos);
+ }
+}
+
+/*
+ * Returns 0 if current not found.
+ * Returns 1 if current found.
+ *
+ * Called with tracepoint mutex held
+ */
+int lib_get_iter_tracepoints(struct tracepoint_iter *iter)
+{
+ struct tracepoint_lib *iter_lib;
+ int found = 0;
+
+ cds_list_for_each_entry(iter_lib, &libs, list) {
+ if (iter_lib < iter->lib)
+ continue;
+ else if (iter_lib > iter->lib)
+ iter->tracepoint = NULL;
+ found = tracepoint_get_iter_range(&iter->tracepoint,
+ iter_lib->tracepoints_start,
+ iter_lib->tracepoints_start + iter_lib->tracepoints_count);
+ if (found) {
+ iter->lib = iter_lib;
+ break;
+ }
+ }
+ return found;
+}
+
+/**
+ * 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.
+ * Called with tracepoint mutex held.
+ */
+int tracepoint_get_iter_range(struct tracepoint * const **tracepoint,
+ struct tracepoint * const *begin, struct tracepoint * const *end)
+{
+ if (!*tracepoint && begin != end)
+ *tracepoint = begin;
+ while (*tracepoint >= begin && *tracepoint < end) {
+ if (!**tracepoint)
+ (*tracepoint)++; /* skip dummy */
+ else
+ return 1;
+ }
+ return 0;
+}
+
+/*
+ * Called with tracepoint mutex held.
+ */
+static void tracepoint_get_iter(struct tracepoint_iter *iter)
+{
+ int found = 0;
+
+ /* tracepoints in libs. */
+ found = lib_get_iter_tracepoints(iter);
+ if (!found)
+ tracepoint_iter_reset(iter);
+}
+
+/*
+ * Called with UST lock held.
+ */
+void tracepoint_iter_start(struct tracepoint_iter *iter)
+{
+ tracepoint_get_iter(iter);
+}
+
+/*
+ * Called with UST lock held.
+ */
+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);
+}
+
+/*
+ * Called with UST lock held.
+ */
+void tracepoint_iter_stop(struct tracepoint_iter *iter)
+{
+}
+
+void tracepoint_iter_reset(struct tracepoint_iter *iter)
+{
+ iter->tracepoint = NULL;
+}
+
+void tracepoint_set_new_tracepoint_cb(void (*cb)(struct tracepoint *))
+{
+ new_tracepoint_cb = cb;
+}
+
+static void new_tracepoints(struct tracepoint * const *start, struct tracepoint * const *end)
+{
+ if (new_tracepoint_cb) {
+ struct tracepoint * const *t;
+
+ for (t = start; t < end; t++) {
+ if (*t)
+ new_tracepoint_cb(*t);
+ }
+ }
+}
+
+int tracepoint_register_lib(struct tracepoint * const *tracepoints_start,
+ int tracepoints_count)
+{
+ struct tracepoint_lib *pl, *iter;
+
+ init_tracepoint();
+
+ pl = (struct tracepoint_lib *) zmalloc(sizeof(struct tracepoint_lib));
+
+ pl->tracepoints_start = tracepoints_start;
+ pl->tracepoints_count = tracepoints_count;
+
+ ust_lock();
+ /*
+ * We sort the libs by struct lib pointer address.
+ */
+ cds_list_for_each_entry_reverse(iter, &libs, list) {
+ BUG_ON(iter == pl); /* Should never be in the list twice */
+ if (iter < pl) {
+ /* We belong to the location right after iter. */
+ cds_list_add(&pl->list, &iter->list);
+ goto lib_added;
+ }
+ }
+ /* We should be added at the head of the list */
+ cds_list_add(&pl->list, &libs);
+lib_added:
+ new_tracepoints(tracepoints_start, tracepoints_start + tracepoints_count);
+
+ /* TODO: update just the loaded lib */
+ lib_update_tracepoints();
+ ust_unlock();
+
+ DBG("just registered a tracepoints section from %p and having %d tracepoints",
+ tracepoints_start, tracepoints_count);
+
+ return 0;
+}
+
+int tracepoint_unregister_lib(struct tracepoint * const *tracepoints_start)
+{
+ struct tracepoint_lib *lib;
+
+ ust_lock();
+ cds_list_for_each_entry(lib, &libs, list) {
+ if (lib->tracepoints_start == tracepoints_start) {
+ struct tracepoint_lib *lib2free = lib;
+ cds_list_del(&lib->list);
+ free(lib2free);
+ break;
+ }
+ }
+ ust_unlock();
+
+ return 0;
+}
+
+void init_tracepoint(void)
+{
+ if (uatomic_xchg(&initialized, 1) == 1)
+ return;
+ init_usterr();
+}
+
+void exit_tracepoint(void)
+{
+ initialized = 0;
+}
projects / ust.git / blobdiff