--- /dev/null
+/*
+ * SPDX-License-Identifier: LGPL-2.1-only
+ *
+ * Copyright (C) 2008-2011 Mathieu Desnoyers
+ * Copyright (C) 2009 Pierre-Marc Fournier
+ *
+ * Ported to userspace by Pierre-Marc Fournier.
+ */
+
+#define _LGPL_SOURCE
+#include <errno.h>
+#include <stdint.h>
+#include <stddef.h>
+#include <stdio.h>
+
+#include <urcu/arch.h>
+#include <lttng/urcu/urcu-ust.h>
+#include <urcu/hlist.h>
+#include <urcu/uatomic.h>
+#include <urcu/compiler.h>
+#include <urcu/system.h>
+
+#include <lttng/tracepoint.h>
+#include <lttng/ust-abi.h> /* for LTTNG_UST_ABI_SYM_NAME_LEN */
+
+#include "common/logging.h"
+#include "common/macros.h"
+
+#include "lib/lttng-ust-tracepoint/tracepoint.h"
+#include "common/tracepoint.h"
+#include "common/jhash.h"
+#include "common/err-ptr.h"
+
+/* Test compiler support for weak symbols with hidden visibility. */
+int __tracepoint_test_symbol1 __attribute__((weak, visibility("hidden")));
+void *__tracepoint_test_symbol2 __attribute__((weak, visibility("hidden")));
+struct {
+ char a[24];
+} __tracepoint_test_symbol3 __attribute__((weak, visibility("hidden")));
+
+/* Set to 1 to enable tracepoint debug output */
+static const int tracepoint_debug;
+static int initialized;
+
+/*
+ * If tracepoint_destructors_state = 1, tracepoint destructors are
+ * enabled. They are disabled otherwise.
+ */
+static int tracepoint_destructors_state = 1;
+
+static void (*new_tracepoint_cb)(struct lttng_ust_tracepoint *);
+
+/*
+ * tracepoint_mutex nests inside UST mutex.
+ *
+ * Note about interaction with fork/clone: UST does not hold the
+ * tracepoint mutex across fork/clone because it is either:
+ * - nested within UST mutex, in which case holding the UST mutex across
+ * fork/clone suffice,
+ * - taken by a library constructor, which should never race with a
+ * fork/clone if the application is expected to continue running with
+ * the same memory layout (no following exec()).
+ */
+static pthread_mutex_t tracepoint_mutex = PTHREAD_MUTEX_INITIALIZER;
+
+/*
+ * libraries that contain tracepoints (struct tracepoint_lib).
+ * Protected by tracepoint mutex.
+ */
+static CDS_LIST_HEAD(libs);
+
+/*
+ * The tracepoint mutex protects the library tracepoints, the hash table, and
+ * the library list.
+ * All calls to the tracepoint API must be protected by the tracepoint mutex,
+ * excepts calls to tracepoint_register_lib and
+ * tracepoint_unregister_lib, which take the tracepoint mutex themselves.
+ */
+
+/*
+ * Tracepoint hash table, containing the active tracepoints.
+ * Protected by tracepoint mutex.
+ */
+#define TRACEPOINT_HASH_BITS 12
+#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;
+
+static CDS_LIST_HEAD(release_queue);
+static int release_queue_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 tracepoint mutex.
+ */
+struct tracepoint_entry {
+ struct cds_hlist_node hlist;
+ struct lttng_ust_tracepoint_probe *probes;
+ int refcount; /* Number of times armed. 0 if disarmed. */
+ int callsite_refcount; /* how many libs use this tracepoint */
+ char *signature;
+ char *name;
+};
+
+struct tp_probes {
+ union {
+ struct cds_list_head list;
+ /* Field below only used for call_rcu scheme */
+ /* struct rcu_head head; */
+ } u;
+ struct lttng_ust_tracepoint_probe probes[0];
+};
+
+/*
+ * Callsite hash table, containing the tracepoint call sites.
+ * Protected by tracepoint mutex.
+ */
+#define CALLSITE_HASH_BITS 12
+#define CALLSITE_TABLE_SIZE (1 << CALLSITE_HASH_BITS)
+static struct cds_hlist_head callsite_table[CALLSITE_TABLE_SIZE];
+
+struct callsite_entry {
+ struct cds_hlist_node hlist; /* hash table node */
+ struct cds_list_head node; /* lib list of callsites node */
+ struct lttng_ust_tracepoint *tp;
+ bool tp_entry_callsite_ref; /* Has a tp_entry took a ref on this callsite */
+};
+
+/* coverity[+alloc] */
+static void *allocate_probes(int count)
+{
+ struct tp_probes *p =
+ zmalloc(count * sizeof(struct lttng_ust_tracepoint_probe)
+ + sizeof(struct tp_probes));
+ return p == NULL ? NULL : p->probes;
+}
+
+/* coverity[+free : arg-0] */
+static void release_probes(void *old)
+{
+ if (old) {
+ struct tp_probes *tp_probes = caa_container_of(old,
+ struct tp_probes, probes[0]);
+ lttng_ust_urcu_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), void *data)
+{
+ int nr_probes = 0;
+ struct lttng_ust_tracepoint_probe *old, *new;
+
+ if (!probe) {
+ WARN_ON(1);
+ return ERR_PTR(-EINVAL);
+ }
+ 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 lttng_ust_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), void *data)
+{
+ int nr_probes = 0, nr_del = 0, i;
+ struct lttng_ust_tracepoint_probe *old, *new;
+
+ old = entry->probes;
+
+ if (!old)
+ return ERR_PTR(-ENOENT);
+
+ debug_print_probes(entry);
+ /* (N -> M), (N > 1, M >= 0) probes */
+ if (probe) {
+ for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
+ if (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 (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 tracepoint 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;
+ size_t name_len = strlen(name);
+ uint32_t hash;
+
+ if (name_len > LTTNG_UST_ABI_SYM_NAME_LEN - 1) {
+ WARN("Truncating tracepoint name %s which exceeds size limits of %u chars", name, LTTNG_UST_ABI_SYM_NAME_LEN - 1);
+ name_len = LTTNG_UST_ABI_SYM_NAME_LEN - 1;
+ }
+ hash = jhash(name, name_len, 0);
+ head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
+ cds_hlist_for_each_entry(e, node, head, hlist) {
+ if (!strncmp(name, e->name, LTTNG_UST_ABI_SYM_NAME_LEN - 1))
+ return e;
+ }
+ return NULL;
+}
+
+/*
+ * Add the tracepoint to the tracepoint hash table. Must be called with
+ * tracepoint mutex held.
+ */
+static struct tracepoint_entry *add_tracepoint(const char *name,
+ const char *signature)
+{
+ struct cds_hlist_head *head;
+ struct cds_hlist_node *node;
+ struct tracepoint_entry *e;
+ size_t name_len = strlen(name);
+ size_t sig_len = strlen(signature);
+ size_t sig_off, name_off;
+ uint32_t hash;
+
+ if (name_len > LTTNG_UST_ABI_SYM_NAME_LEN - 1) {
+ WARN("Truncating tracepoint name %s which exceeds size limits of %u chars", name, LTTNG_UST_ABI_SYM_NAME_LEN - 1);
+ name_len = LTTNG_UST_ABI_SYM_NAME_LEN - 1;
+ }
+ hash = jhash(name, name_len, 0);
+ head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
+ cds_hlist_for_each_entry(e, node, head, hlist) {
+ if (!strncmp(name, e->name, LTTNG_UST_ABI_SYM_NAME_LEN - 1)) {
+ DBG("tracepoint %s busy", name);
+ return ERR_PTR(-EEXIST); /* Already there */
+ }
+ }
+
+ /*
+ * Using zmalloc here to allocate a variable length elements: name and
+ * signature. Could cause some memory fragmentation if overused.
+ */
+ name_off = sizeof(struct tracepoint_entry);
+ sig_off = name_off + name_len + 1;
+
+ e = zmalloc(sizeof(struct tracepoint_entry) + name_len + 1 + sig_len + 1);
+ if (!e)
+ return ERR_PTR(-ENOMEM);
+ e->name = (char *) e + name_off;
+ memcpy(e->name, name, name_len + 1);
+ e->name[name_len] = '\0';
+
+ e->signature = (char *) e + sig_off;
+ memcpy(e->signature, signature, sig_len + 1);
+ e->signature[sig_len] = '\0';
+
+ e->probes = NULL;
+ e->refcount = 0;
+ e->callsite_refcount = 0;
+
+ cds_hlist_add_head(&e->hlist, head);
+ return e;
+}
+
+/*
+ * Remove the tracepoint from the tracepoint hash table. Must be called with
+ * tracepoint mutex held.
+ */
+static 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 lttng_ust_tracepoint *elem, int active)
+{
+ WARN_ON(strncmp((*entry)->name, elem->name, LTTNG_UST_ABI_SYM_NAME_LEN - 1) != 0);
+ /*
+ * Check that signatures match before connecting a probe to a
+ * tracepoint. Warn the user if they don't.
+ */
+ if (strcmp(elem->signature, (*entry)->signature) != 0) {
+ static int warned = 0;
+
+ /* Only print once, don't flood console. */
+ if (!warned) {
+ WARN("Tracepoint signature mismatch, not enabling one or more tracepoints. Ensure that the tracepoint probes prototypes match the application.");
+ WARN("Tracepoint \"%s\" signatures: call: \"%s\" vs probe: \"%s\".",
+ elem->name, elem->signature, (*entry)->signature);
+ warned = 1;
+ }
+ /* Don't accept connecting non-matching signatures. */
+ return;
+ }
+
+ /*
+ * 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.
+ */
+ lttng_ust_rcu_assign_pointer(elem->probes, (*entry)->probes);
+ CMM_STORE_SHARED(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 lttng_ust_tracepoint *elem)
+{
+ CMM_STORE_SHARED(elem->state, 0);
+ lttng_ust_rcu_assign_pointer(elem->probes, NULL);
+}
+
+/*
+ * Add the callsite to the callsite hash table. Must be called with
+ * tracepoint mutex held.
+ */
+static void add_callsite(struct tracepoint_lib * lib, struct lttng_ust_tracepoint *tp)
+{
+ struct cds_hlist_head *head;
+ struct callsite_entry *e;
+ const char *name = tp->name;
+ size_t name_len = strlen(name);
+ uint32_t hash;
+ struct tracepoint_entry *tp_entry;
+
+ if (name_len > LTTNG_UST_ABI_SYM_NAME_LEN - 1) {
+ WARN("Truncating tracepoint name %s which exceeds size limits of %u chars", name, LTTNG_UST_ABI_SYM_NAME_LEN - 1);
+ name_len = LTTNG_UST_ABI_SYM_NAME_LEN - 1;
+ }
+ hash = jhash(name, name_len, 0);
+ head = &callsite_table[hash & (CALLSITE_TABLE_SIZE - 1)];
+ e = zmalloc(sizeof(struct callsite_entry));
+ if (!e) {
+ PERROR("Unable to add callsite for tracepoint \"%s\"", name);
+ return;
+ }
+ cds_hlist_add_head(&e->hlist, head);
+ e->tp = tp;
+ cds_list_add(&e->node, &lib->callsites);
+
+ tp_entry = get_tracepoint(name);
+ if (!tp_entry)
+ return;
+ tp_entry->callsite_refcount++;
+ e->tp_entry_callsite_ref = true;
+}
+
+/*
+ * Remove the callsite from the callsite hash table and from lib
+ * callsite list. Must be called with tracepoint mutex held.
+ */
+static void remove_callsite(struct callsite_entry *e)
+{
+ struct tracepoint_entry *tp_entry;
+
+ tp_entry = get_tracepoint(e->tp->name);
+ if (tp_entry) {
+ if (e->tp_entry_callsite_ref)
+ tp_entry->callsite_refcount--;
+ if (tp_entry->callsite_refcount == 0)
+ disable_tracepoint(e->tp);
+ }
+ cds_hlist_del(&e->hlist);
+ cds_list_del(&e->node);
+ free(e);
+}
+
+/*
+ * Enable/disable all callsites based on the state of a specific
+ * tracepoint entry.
+ * Must be called with tracepoint mutex held.
+ */
+static void tracepoint_sync_callsites(const char *name)
+{
+ struct cds_hlist_head *head;
+ struct cds_hlist_node *node;
+ struct callsite_entry *e;
+ size_t name_len = strlen(name);
+ uint32_t hash;
+ struct tracepoint_entry *tp_entry;
+
+ tp_entry = get_tracepoint(name);
+ if (name_len > LTTNG_UST_ABI_SYM_NAME_LEN - 1) {
+ WARN("Truncating tracepoint name %s which exceeds size limits of %u chars", name, LTTNG_UST_ABI_SYM_NAME_LEN - 1);
+ name_len = LTTNG_UST_ABI_SYM_NAME_LEN - 1;
+ }
+ hash = jhash(name, name_len, 0);
+ head = &callsite_table[hash & (CALLSITE_TABLE_SIZE - 1)];
+ cds_hlist_for_each_entry(e, node, head, hlist) {
+ struct lttng_ust_tracepoint *tp = e->tp;
+
+ if (strncmp(name, tp->name, LTTNG_UST_ABI_SYM_NAME_LEN - 1))
+ continue;
+ if (tp_entry) {
+ if (!e->tp_entry_callsite_ref) {
+ tp_entry->callsite_refcount++;
+ e->tp_entry_callsite_ref = true;
+ }
+ set_tracepoint(&tp_entry, tp,
+ !!tp_entry->refcount);
+ } else {
+ disable_tracepoint(tp);
+ e->tp_entry_callsite_ref = false;
+ }
+ }
+}
+
+/**
+ * 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 lttng_ust_tracepoint * const *begin,
+ struct lttng_ust_tracepoint * const *end)
+{
+ struct lttng_ust_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(struct tracepoint_lib *lib)
+{
+ tracepoint_update_probe_range(lib->tracepoints_start,
+ lib->tracepoints_start + lib->tracepoints_count);
+}
+
+static void lib_register_callsites(struct tracepoint_lib *lib)
+{
+ struct lttng_ust_tracepoint * const *begin;
+ struct lttng_ust_tracepoint * const *end;
+ struct lttng_ust_tracepoint * const *iter;
+
+ begin = lib->tracepoints_start;
+ end = lib->tracepoints_start + lib->tracepoints_count;
+
+ for (iter = begin; iter < end; iter++) {
+ if (!*iter)
+ continue; /* skip dummy */
+ if (!(*iter)->name) {
+ continue;
+ }
+ add_callsite(lib, *iter);
+ }
+}
+
+static void lib_unregister_callsites(struct tracepoint_lib *lib)
+{
+ struct callsite_entry *callsite, *tmp;
+
+ cds_list_for_each_entry_safe(callsite, tmp, &lib->callsites, node)
+ remove_callsite(callsite);
+}
+
+/*
+ * Update probes, removing the faulty probes.
+ */
+static void tracepoint_update_probes(void)
+{
+ struct tracepoint_lib *lib;
+
+ /* tracepoints registered from libraries and executable. */
+ cds_list_for_each_entry(lib, &libs, list)
+ lib_update_tracepoints(lib);
+}
+
+static struct lttng_ust_tracepoint_probe *
+tracepoint_add_probe(const char *name, void (*probe)(void), void *data,
+ const char *signature)
+{
+ struct tracepoint_entry *entry;
+ struct lttng_ust_tracepoint_probe *old;
+
+ entry = get_tracepoint(name);
+ if (entry) {
+ if (strcmp(entry->signature, signature) != 0) {
+ ERR("Tracepoint and probe signature do not match.");
+ return ERR_PTR(-EINVAL);
+ }
+ } else {
+ entry = add_tracepoint(name, signature);
+ if (IS_ERR(entry))
+ return (struct lttng_ust_tracepoint_probe *)entry;
+ }
+ old = tracepoint_entry_add_probe(entry, probe, data);
+ if (IS_ERR(old) && !entry->refcount)
+ remove_tracepoint(entry);
+ return old;
+}
+
+static void tracepoint_release_queue_add_old_probes(void *old)
+{
+ release_queue_need_update = 1;
+ if (old) {
+ struct tp_probes *tp_probes = caa_container_of(old,
+ struct tp_probes, probes[0]);
+ cds_list_add(&tp_probes->u.list, &release_queue);
+ }
+}
+
+/**
+ * __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 tracepoint mutex held.
+ */
+int __tracepoint_probe_register(const char *name, void (*probe)(void),
+ void *data, const char *signature)
+{
+ void *old;
+ int ret = 0;
+
+ DBG("Registering probe to tracepoint %s", name);
+
+ pthread_mutex_lock(&tracepoint_mutex);
+ old = tracepoint_add_probe(name, probe, data, signature);
+ if (IS_ERR(old)) {
+ ret = PTR_ERR(old);
+ goto end;
+ }
+
+ tracepoint_sync_callsites(name);
+ release_probes(old);
+end:
+ pthread_mutex_unlock(&tracepoint_mutex);
+ return ret;
+}
+
+/*
+ * Caller needs to invoke __tracepoint_probe_release_queue() after
+ * calling lttng_ust_tp_probe_register_queue_release() one or multiple
+ * times to ensure it does not leak memory.
+ */
+int lttng_ust_tp_probe_register_queue_release(const char *name,
+ void (*probe)(void), void *data, const char *signature)
+{
+ void *old;
+ int ret = 0;
+
+ DBG("Registering probe to tracepoint %s. Queuing release.", name);
+
+ pthread_mutex_lock(&tracepoint_mutex);
+ old = tracepoint_add_probe(name, probe, data, signature);
+ if (IS_ERR(old)) {
+ ret = PTR_ERR(old);
+ goto end;
+ }
+
+ tracepoint_sync_callsites(name);
+ tracepoint_release_queue_add_old_probes(old);
+end:
+ pthread_mutex_unlock(&tracepoint_mutex);
+ return ret;
+}
+
+static void *tracepoint_remove_probe(const char *name, void (*probe)(void),
+ 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
+ */
+int __tracepoint_probe_unregister(const char *name, void (*probe)(void),
+ void *data)
+{
+ void *old;
+ int ret = 0;
+
+ DBG("Un-registering probe from tracepoint %s", name);
+
+ pthread_mutex_lock(&tracepoint_mutex);
+ old = tracepoint_remove_probe(name, probe, data);
+ if (IS_ERR(old)) {
+ ret = PTR_ERR(old);
+ goto end;
+ }
+ tracepoint_sync_callsites(name);
+ release_probes(old);
+end:
+ pthread_mutex_unlock(&tracepoint_mutex);
+ return ret;
+}
+
+/*
+ * Caller needs to invoke __tracepoint_probe_release_queue() after
+ * calling lttng_ust_tp_probe_unregister_queue_release() one or multiple
+ * times to ensure it does not leak memory.
+ */
+int lttng_ust_tp_probe_unregister_queue_release(const char *name,
+ void (*probe)(void), void *data)
+{
+ void *old;
+ int ret = 0;
+
+ DBG("Un-registering probe from tracepoint %s. Queuing release.", name);
+
+ pthread_mutex_lock(&tracepoint_mutex);
+ old = tracepoint_remove_probe(name, probe, data);
+ if (IS_ERR(old)) {
+ ret = PTR_ERR(old);
+ goto end;
+ }
+ tracepoint_sync_callsites(name);
+ tracepoint_release_queue_add_old_probes(old);
+end:
+ pthread_mutex_unlock(&tracepoint_mutex);
+ return ret;
+}
+
+void lttng_ust_tp_probe_prune_release_queue(void)
+{
+ CDS_LIST_HEAD(release_probes);
+ struct tp_probes *pos, *next;
+
+ DBG("Release queue of unregistered tracepoint probes.");
+
+ pthread_mutex_lock(&tracepoint_mutex);
+ if (!release_queue_need_update)
+ goto end;
+ if (!cds_list_empty(&release_queue))
+ cds_list_replace_init(&release_queue, &release_probes);
+ release_queue_need_update = 0;
+
+ /* Wait for grace period between all sync_callsites and free. */
+ lttng_ust_urcu_synchronize_rcu();
+
+ cds_list_for_each_entry_safe(pos, next, &release_probes, u.list) {
+ cds_list_del(&pos->u.list);
+ free(pos);
+ }
+end:
+ pthread_mutex_unlock(&tracepoint_mutex);
+}
+
+static void tracepoint_add_old_probes(void *old)
+{
+ need_update = 1;
+ if (old) {
+ struct tp_probes *tp_probes = caa_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()
+ */
+int tracepoint_probe_register_noupdate(const char *name, void (*probe)(void),
+ void *data, const char *signature)
+{
+ void *old;
+ int ret = 0;
+
+ pthread_mutex_lock(&tracepoint_mutex);
+ old = tracepoint_add_probe(name, probe, data, signature);
+ if (IS_ERR(old)) {
+ ret = PTR_ERR(old);
+ goto end;
+ }
+ tracepoint_add_old_probes(old);
+end:
+ pthread_mutex_unlock(&tracepoint_mutex);
+ return ret;
+}
+
+/**
+ * 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 tracepoint mutex held.
+ */
+int tracepoint_probe_unregister_noupdate(const char *name, void (*probe)(void),
+ void *data)
+{
+ void *old;
+ int ret = 0;
+
+ DBG("Un-registering probe from tracepoint %s", name);
+
+ pthread_mutex_lock(&tracepoint_mutex);
+ old = tracepoint_remove_probe(name, probe, data);
+ if (IS_ERR(old)) {
+ ret = PTR_ERR(old);
+ goto end;
+ }
+ tracepoint_add_old_probes(old);
+end:
+ pthread_mutex_unlock(&tracepoint_mutex);
+ return ret;
+}
+
+/**
+ * tracepoint_probe_update_all - update tracepoints
+ */
+void tracepoint_probe_update_all(void)
+{
+ CDS_LIST_HEAD(release_probes);
+ struct tp_probes *pos, *next;
+
+ pthread_mutex_lock(&tracepoint_mutex);
+ if (!need_update) {
+ goto end;
+ }
+ if (!cds_list_empty(&old_probes))
+ cds_list_replace_init(&old_probes, &release_probes);
+ need_update = 0;
+
+ tracepoint_update_probes();
+ /* Wait for grace period between update_probes and free. */
+ lttng_ust_urcu_synchronize_rcu();
+ cds_list_for_each_entry_safe(pos, next, &release_probes, u.list) {
+ cds_list_del(&pos->u.list);
+ free(pos);
+ }
+end:
+ pthread_mutex_unlock(&tracepoint_mutex);
+}
+
+static void new_tracepoints(struct lttng_ust_tracepoint * const *start,
+ struct lttng_ust_tracepoint * const *end)
+{
+ if (new_tracepoint_cb) {
+ struct lttng_ust_tracepoint * const *t;
+
+ for (t = start; t < end; t++) {
+ if (*t)
+ new_tracepoint_cb(*t);
+ }
+ }
+}
+
+/*
+ * tracepoint_{un,}register_lib is meant to be looked up by instrumented
+ * applications through dlsym(). If found, those can register their
+ * tracepoints, else those tracepoints will not be available for
+ * tracing. The number at the end of those symbols acts as a major
+ * version for tracepoints.
+ *
+ * Older instrumented applications should still work with newer
+ * liblttng-ust, but it is fine that instrumented applications compiled
+ * against recent liblttng-ust headers require a recent liblttng-ust
+ * runtime for those tracepoints to be taken into account.
+ */
+int tracepoint_register_lib(struct lttng_ust_tracepoint * const *tracepoints_start,
+ int tracepoints_count);
+int tracepoint_register_lib(struct lttng_ust_tracepoint * const *tracepoints_start,
+ int tracepoints_count)
+{
+ struct tracepoint_lib *pl, *iter;
+
+ lttng_ust_tp_init();
+
+ pl = (struct tracepoint_lib *) zmalloc(sizeof(struct tracepoint_lib));
+ if (!pl) {
+ PERROR("Unable to register tracepoint lib");
+ return -1;
+ }
+ pl->tracepoints_start = tracepoints_start;
+ pl->tracepoints_count = tracepoints_count;
+ CDS_INIT_LIST_HEAD(&pl->callsites);
+
+ pthread_mutex_lock(&tracepoint_mutex);
+ /*
+ * 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);
+ lib_register_callsites(pl);
+ lib_update_tracepoints(pl);
+ pthread_mutex_unlock(&tracepoint_mutex);
+
+ DBG("just registered a tracepoints section from %p and having %d tracepoints",
+ tracepoints_start, tracepoints_count);
+ if (lttng_ust_logging_debug_enabled()) {
+ int i;
+
+ for (i = 0; i < tracepoints_count; i++) {
+ DBG("registered tracepoint: %s", tracepoints_start[i]->name);
+ }
+ }
+
+ return 0;
+}
+
+int tracepoint_unregister_lib(struct lttng_ust_tracepoint * const *tracepoints_start);
+int tracepoint_unregister_lib(struct lttng_ust_tracepoint * const *tracepoints_start)
+{
+ struct tracepoint_lib *lib;
+
+ pthread_mutex_lock(&tracepoint_mutex);
+ cds_list_for_each_entry(lib, &libs, list) {
+ if (lib->tracepoints_start != tracepoints_start)
+ continue;
+
+ cds_list_del(&lib->list);
+ /*
+ * Unregistering a callsite also decreases the
+ * callsite reference count of the corresponding
+ * tracepoint, and disables the tracepoint if
+ * the reference count drops to zero.
+ */
+ lib_unregister_callsites(lib);
+ DBG("just unregistered a tracepoints section from %p",
+ lib->tracepoints_start);
+ free(lib);
+ break;
+ }
+ pthread_mutex_unlock(&tracepoint_mutex);
+ return 0;
+}
+
+/*
+ * Report in debug message whether the compiler correctly supports weak
+ * hidden symbols. This test checks that the address associated with two
+ * weak symbols with hidden visibility is the same when declared within
+ * two compile units part of the same module.
+ */
+static void check_weak_hidden(void)
+{
+ DBG("Your compiler treats weak symbols with hidden visibility for integer objects as %s between compile units part of the same module.",
+ &__tracepoint_test_symbol1 == lttng_ust_tp_check_weak_hidden1() ?
+ "SAME address" :
+ "DIFFERENT addresses");
+ DBG("Your compiler treats weak symbols with hidden visibility for pointer objects as %s between compile units part of the same module.",
+ &__tracepoint_test_symbol2 == lttng_ust_tp_check_weak_hidden2() ?
+ "SAME address" :
+ "DIFFERENT addresses");
+ DBG("Your compiler treats weak symbols with hidden visibility for 24-byte structure objects as %s between compile units part of the same module.",
+ &__tracepoint_test_symbol3 == lttng_ust_tp_check_weak_hidden3() ?
+ "SAME address" :
+ "DIFFERENT addresses");
+}
+
+void lttng_ust_tp_init(void)
+{
+ if (uatomic_xchg(&initialized, 1) == 1)
+ return;
+ lttng_ust_logging_init();
+ check_weak_hidden();
+}
+
+void lttng_ust_tp_exit(void)
+{
+ initialized = 0;
+}
+
+/*
+ * Create the wrapper symbols.
+ */
+#undef tp_rcu_read_lock
+#undef tp_rcu_read_unlock
+#undef tp_rcu_dereference
+
+void tp_rcu_read_lock(void);
+void tp_rcu_read_lock(void)
+{
+ lttng_ust_urcu_read_lock();
+}
+
+void tp_rcu_read_unlock(void);
+void tp_rcu_read_unlock(void)
+{
+ lttng_ust_urcu_read_unlock();
+}
+
+void *tp_rcu_dereference_sym(void *p);
+void *tp_rcu_dereference_sym(void *p)
+{
+ return lttng_ust_rcu_dereference(p);
+}
+
+/*
+ * Programs that have threads that survive after they exit, and therefore call
+ * library destructors, should disable the tracepoint destructors by calling
+ * tp_disable_destructors(). This will leak the tracepoint
+ * instrumentation library shared object, leaving its teardown to the operating
+ * system process teardown.
+ *
+ * To access and/or modify this value, users need to use a combination of
+ * dlopen(3) and dlsym(3) to get an handle on the
+ * tp_disable_destructors and tp_get_destructors_state symbols below.
+ */
+void tp_disable_destructors(void);
+void tp_disable_destructors(void)
+{
+ uatomic_set(&tracepoint_destructors_state, 0);
+}
+
+/*
+ * Returns 1 if the destructors are enabled and should be executed.
+ * Returns 0 if the destructors are disabled.
+ */
+int tp_get_destructors_state(void);
+int tp_get_destructors_state(void)
+{
+ return uatomic_read(&tracepoint_destructors_state);
+}
projects / lttng-ust.git / blobdiff