callsite: move after the call

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

diff --git a/include/lttng/tracepoint.h b/include/lttng/tracepoint.h
index 8b08914418f0c98b047c46d53ed77637fb838073..8e4704c47f3e264e653b1539f45e30234f4080cf 100644 (file)
--- a/include/lttng/tracepoint.h
+++ b/include/lttng/tracepoint.h
@@ -35,11 +35,13 @@
 extern "C" {
 #endif
 
-#define tracepoint(provider, name, ...)                                            \
-       do {                                                                \
-               STAP_PROBEV(provider, name, ## __VA_ARGS__);                \
-               if (caa_unlikely(__tracepoint_##provider##___##name.state)) \
-                       __tracepoint_cb_##provider##___##name(__VA_ARGS__); \
+#define tracepoint(provider, name, ...)                                              \
+       do {                                                                  \
+               STAP_PROBEV(provider, name, ## __VA_ARGS__);                  \
+               if (caa_unlikely(__tracepoint_##provider##___##name.state)) { \
+                       __tracepoint_cb_##provider##___##name(__VA_ARGS__);   \
+                       TRACEPOINT_CALLSITE(provider, name);                  \
+               }                                                             \
        } while (0)
 
 #define TP_ARGS(...)       __VA_ARGS__
@@ -205,6 +207,112 @@ 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")));
+
+#if (CAA_BITS_PER_LONG == 64)
+#define __TP_ASM_PTR   ".quad "
+#else
+#define __TP_ASM_PTR   ".long "
+#endif
+
+/*
+ * 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)                                  \
+do {                                                                           \
+       asm volatile (  ".pushsection __tracepoint_callsite, \"aw\"\n\t"        \
+                       "1:\n\t"                                                \
+                       __TP_ASM_PTR "%c0, %c1, %c2, 2f\n\t"                    \
+                       ".int %c3\n\t"                                          \
+                       ".space 16\n\t" /* padding */                           \
+                       ".popsection\n\t"                                       \
+                       ".pushsection __tracepoint_callsite_ptrs, \"aw\"\n\t"   \
+                       __TP_ASM_PTR "1b\n\t"                                   \
+                       ".popsection\n\t"                                       \
+                       "2:\n\t"                                                \
+               : : "i" (#_provider ":" #_name),                                \
+                       "i" (__func__),                                         \
+                       "i" (__FILE__),                                         \
+                       "i" (__LINE__));                                        \
+} while (0)
+
+/*
+ * 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
 
 /*