+++ /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 <stdint.h>
-#include <stddef.h>
-
-#include <urcu/arch.h>
-#include <urcu-bp.h>
-#include <urcu/hlist.h>
-#include <urcu/uatomic.h>
-#include <urcu/compiler.h>
-
-#include <lttng/tracepoint.h>
-#include <lttng/ust-abi.h> /* for LTTNG_UST_SYM_NAME_LEN */
-
-#include <usterr-signal-safe.h>
-#include <helper.h>
-
-#include "tracepoint-internal.h"
-#include "ltt-tracer-core.h"
-#include "jhash.h"
-#include "error.h"
-
-/* Set to 1 to enable tracepoint debug output */
-static const int tracepoint_debug;
-static int initialized;
-static void (*new_tracepoint_cb)(struct 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 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 tracepoint mutex.
- */
-struct tracepoint_entry {
- struct cds_hlist_node hlist;
- struct tracepoint_probe *probes;
- int refcount; /* Number of times armed. 0 if disarmed. */
- const char *signature;
- char name[0];
-};
-
-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];
-};
-
-static 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 void release_probes(void *old)
-{
- if (old) {
- struct tp_probes *tp_probes = caa_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 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_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 (!strncmp(name, e->name, LTTNG_UST_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);
- 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 (!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.
- */
- e = zmalloc(sizeof(struct tracepoint_entry) + name_len + 1);
- if (!e)
- return ERR_PTR(-ENOMEM);
- memcpy(&e->name[0], name, name_len + 1);
- e->name[name_len] = '\0';
- e->probes = NULL;
- e->refcount = 0;
- e->signature = signature;
- 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 tracepoint *elem, int active)
-{
- 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
- * 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,
- const char *signature)
-{
- struct tracepoint_entry *entry;
- struct tracepoint_probe *old;
-
- entry = get_tracepoint(name);
- if (!entry) {
- entry = add_tracepoint(name, signature);
- 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 tracepoint mutex held.
- */
-int __tracepoint_probe_register(const char *name, void *probe, 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_update_probes(); /* may update entry */
- release_probes(old);
-end:
- pthread_mutex_unlock(&tracepoint_mutex);
- return ret;
-}
-
-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
- */
-int __tracepoint_probe_unregister(const char *name, void *probe, 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_update_probes(); /* may update entry */
- release_probes(old);
-end:
- pthread_mutex_unlock(&tracepoint_mutex);
- return ret;
-}
-
-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 *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 *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();
- 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);
-}
-
-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);
- }
- }
-}
-
-static
-void lib_disable_tracepoints(struct tracepoint * const *begin,
- struct tracepoint * const *end)
-{
- struct tracepoint * const *iter;
-
- for (iter = begin; iter < end; iter++) {
- if (!*iter)
- continue; /* skip dummy */
- disable_tracepoint(*iter);
- }
-
-}
-
-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;
-
- 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);
-
- /* TODO: update just the loaded lib */
- lib_update_tracepoints();
- 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)
-{
- struct tracepoint_lib *lib;
- int tracepoints_count;
-
- 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);
- tracepoints_count = lib->tracepoints_count;
- free(lib2free);
- goto found;
- }
- }
- goto end;
-found:
- /*
- * Force tracepoint disarm for all tracepoints of this lib.
- * This takes care of destructor of library that would leave a
- * LD_PRELOAD wrapper override function enabled for tracing, but
- * the session teardown would not be able to reach the
- * tracepoint anymore to disable it.
- */
- lib_disable_tracepoints(tracepoints_start,
- tracepoints_start + tracepoints_count);
- DBG("just unregistered a tracepoints section from %p",
- tracepoints_start);
-end:
- pthread_mutex_unlock(&tracepoint_mutex);
- return 0;
-}
-
-void init_tracepoint(void)
-{
- if (uatomic_xchg(&initialized, 1) == 1)
- return;
- init_usterr();
-}
-
-void exit_tracepoint(void)
-{
- initialized = 0;
-}
-
-/*
- * Create the wrapper symbols.
- */
-#undef tp_rcu_read_lock_bp
-#undef tp_rcu_read_unlock_bp
-#undef tp_rcu_dereference_bp
-
-void tp_rcu_read_lock_bp(void)
-{
- rcu_read_lock_bp();
-}
-
-void tp_rcu_read_unlock_bp(void)
-{
- rcu_read_unlock_bp();
-}
-
-void *tp_rcu_dereference_sym_bp(void *p)
-{
- return rcu_dereference_bp(p);
-}
projects / lttng-ust.git / blobdiff