Add callsite support

[lttng-ust.git] / include / lttng / tracepoint.h

diff --git a/include/lttng/tracepoint.h b/include/lttng/tracepoint.h
index 8b08914418f0c98b047c46d53ed77637fb838073..8086b648a2a4be8d9b7ed04cbe21977a3f039929 100644 (file)
--- a/include/lttng/tracepoint.h
+++ b/include/lttng/tracepoint.h
@@ -37,6 +37,7 @@ extern "C" {
 
 #define tracepoint(provider, name, ...)                                            \
        do {                                                                \
+               TRACEPOINT_CALLSITE(provider, name);                        \
                STAP_PROBEV(provider, name, ## __VA_ARGS__);                \
                if (caa_unlikely(__tracepoint_##provider##___##name.state)) \
                        __tracepoint_cb_##provider##___##name(__VA_ARGS__); \
@@ -205,6 +206,103 @@ struct tracepoint_dlopen {
 
 extern struct tracepoint_dlopen tracepoint_dlopen;
 
+struct tracepoint_callsite_dlopen {
+       void *liblttngust_handle;
+
+       int (*tracepoint_register_lib_callsite)(struct tracepoint_callsite * const *tp_start,
+               int tp_count);
+       int (*tracepoint_unregister_lib_callsite)(struct tracepoint_callsite * const *tp_start,
+               int tp_count);
+};
+
+struct tracepoint_callsite_dlopen tracepoint_callsite_dlopen
+       __attribute__((weak, visibility("hidden")));
+int __tracepoint_callsite_registered
+       __attribute__((weak, visibility("hidden")));
+
+/*
+ * Note: to allow PIC code, we need to allow the linker to update the pointers
+ * in the __tracepoints_callsite_ptrs section.
+ * Therefore, this section is _not_ const (read-only).
+ */
+#define TRACEPOINT_CALLSITE(_provider, _name)                                  \
+       static struct tracepoint_callsite                                       \
+               __tracepoint_callsite_##_provider##___##_name                   \
+               __attribute__((section("__tracepoint_callsite"))) =             \
+               {                                                               \
+                       .tp = &__tracepoint_##_provider##___##_name,            \
+                       .func = __func__,                                       \
+                       .file = __FILE__,                                       \
+                       .lineno = __LINE__,                                     \
+               };                                                              \
+       static struct tracepoint_callsite *                                     \
+               __tracepoint_callsite_ptr_##_provider##___##_name               \
+               __attribute__((used, section("__tracepoint_callsite_ptrs"))) =  \
+                       &__tracepoint_callsite_##_provider##___##_name
+
+/*
+ * These weak symbols, the constructor, and destructor take care of
+ * registering only _one_ instance of the tracepoint callsite per
+ * shared-ojbect (or for the whole main program).
+ */
+extern struct tracepoint_callsite * const __start___tracepoint_callsite_ptrs[]
+       __attribute__((weak, visibility("hidden")));
+extern struct tracepoint_callsite * const __stop___tracepoint_callsite_ptrs[]
+       __attribute__((weak, visibility("hidden")));
+
+/*
+ * We need at least one pointer in the section.
+ */
+static struct tracepoint_callsite *
+       __tracepoint_callsite_ptr_dummy
+       __attribute__((used, section("__tracepoint_callsite_ptrs"))) =
+               NULL;
+
+static void lttng_ust_notrace __attribute__((constructor))
+__tracepoint_callsite__init(void);
+static void
+__tracepoint_callsite__init(void)
+{
+       if (__tracepoint_callsite_registered++)
+               return;
+
+       tracepoint_callsite_dlopen.liblttngust_handle =
+               dlopen("liblttng-ust-tracepoint.so.0", RTLD_NOW | RTLD_GLOBAL);
+       if (!tracepoint_callsite_dlopen.liblttngust_handle)
+               return;
+       tracepoint_callsite_dlopen.tracepoint_register_lib_callsite =
+               URCU_FORCE_CAST(int (*)(struct tracepoint_callsite * const *, int),
+                               dlsym(tracepoint_callsite_dlopen.liblttngust_handle,
+                                       "tracepoint_register_lib_callsite"));
+       tracepoint_callsite_dlopen.tracepoint_unregister_lib_callsite =
+               URCU_FORCE_CAST(int (*)(struct tracepoint_callsite * const *, int),
+                               dlsym(tracepoint_callsite_dlopen.liblttngust_handle,
+                                       "tracepoint_unregister_lib_callsite"));
+       tracepoint_callsite_dlopen.tracepoint_register_lib_callsite(__start___tracepoint_callsite_ptrs,
+                               __stop___tracepoint_callsite_ptrs -
+                               __start___tracepoint_callsite_ptrs);
+}
+
+static void lttng_ust_notrace __attribute__((destructor))
+__tracepoint_callsite__destroy(void);
+static void
+__tracepoint_callsite__destroy(void)
+{
+       int ret;
+
+       if (--__tracepoint_callsite_registered)
+               return;
+       if (tracepoint_callsite_dlopen.tracepoint_unregister_lib_callsite)
+               tracepoint_callsite_dlopen.tracepoint_unregister_lib_callsite(__start___tracepoint_callsite_ptrs,
+                               __stop___tracepoint_callsite_ptrs -
+                               __start___tracepoint_callsite_ptrs);
+       if (tracepoint_callsite_dlopen.liblttngust_handle) {
+               ret = dlclose(tracepoint_callsite_dlopen.liblttngust_handle);
+               assert(!ret);
+               memset(&tracepoint_callsite_dlopen, 0, sizeof(tracepoint_callsite_dlopen));
+       }
+}
+
 #ifdef TRACEPOINT_DEFINE
 
 /*