X-Git-Url: https://git.lttng.org/?a=blobdiff_plain;f=liblttng-ust%2Ftracepoint.c;h=f74a43b0ea67076a71c1f03b7b11976a4e3c5849;hb=ade7037b9b18fc90eb1ab919286aaf6ea3dc96a7;hp=0393aa467a282b17139a05ae17fd8336e7271fb9;hpb=40b2b5a43e4c2067849770b3379ca5360facacd5;p=lttng-ust.git

diff --git a/liblttng-ust/tracepoint.c b/liblttng-ust/tracepoint.c
index 0393aa46..f74a43b0 100644
--- a/liblttng-ust/tracepoint.c
+++ b/liblttng-ust/tracepoint.c
@@ -31,6 +31,7 @@
 #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>
@@ -86,6 +87,8 @@ struct tracepoint_entry {
 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];
 };
@@ -207,11 +210,17 @@ 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;
@@ -226,12 +235,17 @@ 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;
-	uint32_t hash = jhash(name, name_len-1, 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)) {
 			DBG("tracepoint %s busy", name);
 			return ERR_PTR(-EEXIST);	/* Already there */
 		}
@@ -240,10 +254,11 @@ static struct tracepoint_entry *add_tracepoint(const char *name)
 	 * Using zmalloc here to allocate a variable length element. Could
 	 * cause some memory fragmentation if overused.
 	 */
-	e = zmalloc(sizeof(struct tracepoint_entry) + name_len);
+	e = zmalloc(sizeof(struct tracepoint_entry) + name_len + 1);
 	if (!e)
 		return ERR_PTR(-ENOMEM);
-	memcpy(&e->name[0], name, name_len);
+	memcpy(&e->name[0], name, name_len + 1);
+	e->name[name_len] = '\0';
 	e->probes = NULL;
 	e->refcount = 0;
 	cds_hlist_add_head(&e->hlist, head);
@@ -266,7 +281,7 @@ static void remove_tracepoint(struct tracepoint_entry *e)
 static void set_tracepoint(struct tracepoint_entry **entry,
 	struct 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);
 
 	/*
 	 * rcu_assign_pointer has a cmm_smp_wmb() which makes sure that the new
@@ -511,6 +526,20 @@ static void new_tracepoints(struct tracepoint * const *start, struct tracepoint
 	}
 }
 
+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)
 {
@@ -553,18 +582,34 @@ lib_added:
 int tracepoint_unregister_lib(struct tracepoint * const *tracepoints_start)
 {
 	struct tracepoint_lib *lib;
+	int tracepoints_count;
 
 	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);
+			tracepoints_count = lib->tracepoints_count;
 			free(lib2free);
-			break;
+			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:
 	ust_unlock();
-
 	return 0;
 }