X-Git-Url: http://git.lttng.org/?a=blobdiff_plain;f=liblttng-ust%2Ftracepoint.c;h=f65097f6aaa92cc640eab93751847d32abf9556d;hb=c0c0989ab70574e09b2f7e8b48c2da6af664a849;hp=526ee00e58d130cd2093ab59e31078b7cdbf52b4;hpb=596c4223bf063ebc06262c08896c596326d036e6;p=lttng-ust.git diff --git a/liblttng-ust/tracepoint.c b/liblttng-ust/tracepoint.c index 526ee00e..f65097f6 100644 --- a/liblttng-ust/tracepoint.c +++ b/liblttng-ust/tracepoint.c @@ -1,101 +1,151 @@ /* + * SPDX-License-Identifier: LGPL-2.1-only + * * 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 -#include -#include #include #include +#include + #include -#include +#include #include #include #include +#include + +#include +#include /* for LTTNG_UST_SYM_NAME_LEN */ + +#include +#include -#include #include "tracepoint-internal.h" -#include "ltt-tracer-core.h" +#include "lttng-tracer-core.h" #include "jhash.h" +#include "error.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; -static void (*new_tracepoint_cb)(struct tracepoint *); -/* libraries that contain tracepoints (struct tracepoint_lib) */ +/* + * 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 UST lock protects the library tracepoints, the hash table, and + * 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 UST lock, + * 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 UST lock themselves. + * tracepoint_unregister_lib, which take the tracepoint mutex themselves. */ /* * Tracepoint hash table, containing the active tracepoints. - * Protected by tracepoints_mutex. + * Protected by tracepoint mutex. */ -#define TRACEPOINT_HASH_BITS 6 +#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 tracepoints_mutex. + * Tracepoint entries modifications are protected by the tracepoint mutex. */ struct tracepoint_entry { struct cds_hlist_node hlist; - struct tracepoint_probe *probes; + struct lttng_ust_tracepoint_probe *probes; int refcount; /* Number of times armed. 0 if disarmed. */ - char name[0]; + 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 tracepoint_probe probes[0]; + struct lttng_ust_tracepoint_probe probes[0]; }; -static inline void *allocate_probes(int count) +/* + * 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 tracepoint_probe) - + sizeof(struct tp_probes)); + struct tp_probes *p = + zmalloc(count * sizeof(struct lttng_ust_tracepoint_probe) + + sizeof(struct tp_probes)); return p == NULL ? NULL : p->probes; } -static inline void release_probes(void *old) +/* 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]); - synchronize_rcu(); + lttng_ust_synchronize_trace(); free(tp_probes); } } @@ -113,13 +163,15 @@ static void debug_print_probes(struct tracepoint_entry *entry) static void * tracepoint_entry_add_probe(struct tracepoint_entry *entry, - void *probe, void *data) + void (*probe)(void), void *data) { int nr_probes = 0; - struct tracepoint_probe *old, *new; - - WARN_ON(!probe); + 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) { @@ -134,7 +186,8 @@ tracepoint_entry_add_probe(struct tracepoint_entry *entry, if (new == NULL) return ERR_PTR(-ENOMEM); if (old) - memcpy(new, old, nr_probes * sizeof(struct tracepoint_probe)); + 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; @@ -145,11 +198,11 @@ tracepoint_entry_add_probe(struct tracepoint_entry *entry, } static void * -tracepoint_entry_remove_probe(struct tracepoint_entry *entry, void *probe, - void *data) +tracepoint_entry_remove_probe(struct tracepoint_entry *entry, + void (*probe)(void), void *data) { int nr_probes = 0, nr_del = 0, i; - struct tracepoint_probe *old, *new; + struct lttng_ust_tracepoint_probe *old, *new; old = entry->probes; @@ -158,11 +211,12 @@ tracepoint_entry_remove_probe(struct tracepoint_entry *entry, void *probe, 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 (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) { @@ -179,8 +233,7 @@ tracepoint_entry_remove_probe(struct tracepoint_entry *entry, void *probe, if (new == NULL) return ERR_PTR(-ENOMEM); for (i = 0; old[i].func; i++) - if (probe && - (old[i].func != probe || old[i].data != data)) + 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; @@ -192,7 +245,7 @@ tracepoint_entry_remove_probe(struct tracepoint_entry *entry, void *probe, /* * Get tracepoint if the tracepoint is present in the tracepoint hash table. - * Must be called with tracepoints_mutex held. + * Must be called with tracepoint mutex held. * Returns NULL if not present. */ static struct tracepoint_entry *get_tracepoint(const char *name) @@ -200,11 +253,17 @@ static struct tracepoint_entry *get_tracepoint(const char *name) struct cds_hlist_head *head; struct cds_hlist_node *node; struct tracepoint_entry *e; - uint32_t hash = jhash(name, strlen(name), 0); + size_t name_len = strlen(name); + uint32_t hash; + if (name_len > LTTNG_UST_SYM_NAME_LEN - 1) { + WARN("Truncating tracepoint name %s which exceeds size limits of %u chars", name, LTTNG_UST_SYM_NAME_LEN - 1); + name_len = LTTNG_UST_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 (!strcmp(name, e->name)) + if (!strncmp(name, e->name, LTTNG_UST_SYM_NAME_LEN - 1)) return e; } return NULL; @@ -212,42 +271,63 @@ static struct tracepoint_entry *get_tracepoint(const char *name) /* * Add the tracepoint to the tracepoint hash table. Must be called with - * tracepoints_mutex held. + * tracepoint mutex held. */ -static struct tracepoint_entry *add_tracepoint(const char *name) +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) + 1; - uint32_t hash = jhash(name, name_len-1, 0); - + 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_SYM_NAME_LEN - 1) { + WARN("Truncating tracepoint name %s which exceeds size limits of %u chars", name, LTTNG_UST_SYM_NAME_LEN - 1); + name_len = LTTNG_UST_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 (!strcmp(name, e->name)) { + if (!strncmp(name, e->name, LTTNG_UST_SYM_NAME_LEN - 1)) { 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. + * Using zmalloc here to allocate a variable length elements: name and + * signature. Could cause some memory fragmentation if overused. */ - e = zmalloc(sizeof(struct tracepoint_entry) + name_len); + 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); - memcpy(&e->name[0], name, name_len); + 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 - * ust_lock held. + * tracepoint mutex held. */ -static inline void remove_tracepoint(struct tracepoint_entry *e) +static void remove_tracepoint(struct tracepoint_entry *e) { cds_hlist_del(&e->hlist); free(e); @@ -257,9 +337,26 @@ static inline void remove_tracepoint(struct tracepoint_entry *e) * Sets the probe callback corresponding to one tracepoint. */ static void set_tracepoint(struct tracepoint_entry **entry, - struct tracepoint *elem, int active) + struct lttng_ust_tracepoint *elem, int active) { - WARN_ON(strcmp((*entry)->name, elem->name) != 0); + WARN_ON(strncmp((*entry)->name, elem->name, LTTNG_UST_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 @@ -268,8 +365,8 @@ static void set_tracepoint(struct tracepoint_entry **entry, * include/linux/tracepoints.h. A matching cmm_smp_read_barrier_depends() * is used. */ - rcu_assign_pointer(elem->probes, (*entry)->probes); - elem->state = active; + lttng_ust_rcu_assign_pointer(elem->probes, (*entry)->probes); + CMM_STORE_SHARED(elem->state, active); } /* @@ -278,10 +375,105 @@ static void set_tracepoint(struct tracepoint_entry **entry, * 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) +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_SYM_NAME_LEN - 1) { + WARN("Truncating tracepoint name %s which exceeds size limits of %u chars", name, LTTNG_UST_SYM_NAME_LEN - 1); + name_len = LTTNG_UST_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) { - elem->state = 0; - rcu_assign_pointer(elem->probes, NULL); + 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_SYM_NAME_LEN - 1) { + WARN("Truncating tracepoint name %s which exceeds size limits of %u chars", name, LTTNG_UST_SYM_NAME_LEN - 1); + name_len = LTTNG_UST_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_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; + } + } } /** @@ -292,10 +484,10 @@ static void disable_tracepoint(struct tracepoint *elem) * Updates the probe callback corresponding to a range of tracepoints. */ static -void tracepoint_update_probe_range(struct tracepoint * const *begin, - struct tracepoint * const *end) +void tracepoint_update_probe_range(struct lttng_ust_tracepoint * const *begin, + struct lttng_ust_tracepoint * const *end) { - struct tracepoint * const *iter; + struct lttng_ust_tracepoint * const *iter; struct tracepoint_entry *mark_entry; for (iter = begin; iter < end; iter++) { @@ -315,36 +507,68 @@ void tracepoint_update_probe_range(struct tracepoint * const *begin, } } -static void lib_update_tracepoints(void) +static void lib_update_tracepoints(struct tracepoint_lib *lib) { - struct tracepoint_lib *lib; + tracepoint_update_probe_range(lib->tracepoints_start, + lib->tracepoints_start + lib->tracepoints_count); +} - cds_list_for_each_entry(lib, &libs, list) { - 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. */ - lib_update_tracepoints(); + cds_list_for_each_entry(lib, &libs, list) + lib_update_tracepoints(lib); } -static struct tracepoint_probe * -tracepoint_add_probe(const char *name, void *probe, void *data) +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 tracepoint_probe *old; + struct lttng_ust_tracepoint_probe *old; entry = get_tracepoint(name); - if (!entry) { - entry = add_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 tracepoint_probe *)entry; + return (struct lttng_ust_tracepoint_probe *)entry; } old = tracepoint_entry_add_probe(entry, probe, data); if (IS_ERR(old) && !entry->refcount) @@ -352,6 +576,16 @@ tracepoint_add_probe(const char *name, void *probe, void *data) 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 @@ -359,22 +593,59 @@ tracepoint_add_probe(const char *name, void *probe, void *data) * * 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. + * Called with the tracepoint mutex held. */ -int __tracepoint_probe_register(const char *name, void *probe, void *data) +int __tracepoint_probe_register(const char *name, void (*probe)(void), + void *data, const char *signature) { void *old; + int ret = 0; - old = tracepoint_add_probe(name, probe, data); - if (IS_ERR(old)) - return PTR_ERR(old); + 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_update_probes(); /* may update entry */ + tracepoint_sync_callsites(name); release_probes(old); - return 0; +end: + pthread_mutex_unlock(&tracepoint_mutex); + return ret; } -static void *tracepoint_remove_probe(const char *name, void *probe, void *data) +/* + * Caller needs to invoke __tracepoint_probe_release_queue() after + * calling __tracepoint_probe_register_queue_release() one or multiple + * times to ensure it does not leak memory. + */ +int __tracepoint_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; @@ -395,20 +666,77 @@ static void *tracepoint_remove_probe(const char *name, void *probe, void *data) * @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) +int __tracepoint_probe_unregister(const char *name, void (*probe)(void), + void *data) { void *old; + int ret = 0; - old = tracepoint_remove_probe(name, probe, data); - if (IS_ERR(old)) - return PTR_ERR(old); + DBG("Un-registering probe from tracepoint %s", name); - tracepoint_update_probes(); /* may update entry */ + 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); - return 0; +end: + pthread_mutex_unlock(&tracepoint_mutex); + return ret; +} + +/* + * Caller needs to invoke __tracepoint_probe_release_queue() after + * calling __tracepoint_probe_unregister_queue_release() one or multiple + * times to ensure it does not leak memory. + */ +int __tracepoint_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 __tracepoint_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_synchronize_trace(); + + 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) @@ -427,19 +755,23 @@ static void tracepoint_add_old_probes(void *old) * @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) +int tracepoint_probe_register_noupdate(const char *name, void (*probe)(void), + void *data, const char *signature) { void *old; + int ret = 0; - old = tracepoint_add_probe(name, probe, data); + pthread_mutex_lock(&tracepoint_mutex); + old = tracepoint_add_probe(name, probe, data, signature); if (IS_ERR(old)) { - return PTR_ERR(old); + ret = PTR_ERR(old); + goto end; } tracepoint_add_old_probes(old); - return 0; +end: + pthread_mutex_unlock(&tracepoint_mutex); + return ret; } /** @@ -448,153 +780,65 @@ int tracepoint_probe_register_noupdate(const char *name, void *probe, * @probe: probe function pointer * * caller must call tracepoint_probe_update_all() - * Called with the UST lock held. + * Called with the tracepoint mutex held. */ -int tracepoint_probe_unregister_noupdate(const char *name, void *probe, +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)) { - return PTR_ERR(old); + ret = PTR_ERR(old); + goto end; } tracepoint_add_old_probes(old); - return 0; +end: + pthread_mutex_unlock(&tracepoint_mutex); + return ret; } /** * 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; + pthread_mutex_lock(&tracepoint_mutex); if (!need_update) { - return; + 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_synchronize_trace(); cds_list_for_each_entry_safe(pos, next, &release_probes, u.list) { cds_list_del(&pos->u.list); - synchronize_rcu(); free(pos); } +end: + pthread_mutex_unlock(&tracepoint_mutex); } -/* - * 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 *)) +void tracepoint_set_new_tracepoint_cb(void (*cb)(struct lttng_ust_tracepoint *)) { new_tracepoint_cb = cb; } -static void new_tracepoints(struct tracepoint * const *start, struct tracepoint * const *end) +static void new_tracepoints(struct lttng_ust_tracepoint * const *start, + struct lttng_ust_tracepoint * const *end) { if (new_tracepoint_cb) { - struct tracepoint * const *t; + struct lttng_ust_tracepoint * const *t; for (t = start; t < end; t++) { if (*t) @@ -603,19 +847,35 @@ static void new_tracepoints(struct tracepoint * const *start, struct tracepoint } } -int tracepoint_register_lib(struct tracepoint * const *tracepoints_start, - int tracepoints_count) +/* + * 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) { struct tracepoint_lib *pl, *iter; init_tracepoint(); 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); - ust_lock(); + pthread_mutex_lock(&tracepoint_mutex); /* * We sort the libs by struct lib pointer address. */ @@ -631,43 +891,132 @@ int tracepoint_register_lib(struct tracepoint * const *tracepoints_start, 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(); + 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 (ust_debug()) { + int i; + + for (i = 0; i < tracepoints_count; i++) { + DBG("registered tracepoint: %s", tracepoints_start[i]->name); + } + } return 0; } -int tracepoint_unregister_lib(struct tracepoint * const *tracepoints_start) +int tracepoint_unregister_lib(struct lttng_ust_tracepoint * const *tracepoints_start) { struct tracepoint_lib *lib; - ust_lock(); + pthread_mutex_lock(&tracepoint_mutex); 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(); + 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 init_tracepoint(void) { if (uatomic_xchg(&initialized, 1) == 1) return; init_usterr(); + check_weak_hidden(); } void exit_tracepoint(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) +{ + lttng_ust_urcu_read_lock(); +} + +void tp_rcu_read_unlock(void) +{ + lttng_ust_urcu_read_unlock(); +} + +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) +{ + 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) +{ + return uatomic_read(&tracepoint_destructors_state); +} + +void lttng_ust_synchronize_trace(void) +{ + lttng_ust_urcu_synchronize_rcu(); +}