From de774d109ecb14831270cd3f514ed68bb6ea4e69 Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Thu, 28 Mar 2013 14:39:24 -0400 Subject: [PATCH] Fix: tracepoint instrumentation constructor order issue If the linker decides to run a constructor from a tracepoint probe before the constructor from the application, a recent modification (commit 558b9d86247004f8e9bbaf8c982f3b2b182093d1) allowed that the wrong constructor execution order could prohibit the program's tracepoints from being registered. Fix this by making two separate constructors. Fixes #487 Signed-off-by: Mathieu Desnoyers --- include/lttng/tracepoint.h | 164 ++++++++++++++++++++----------------- 1 file changed, 89 insertions(+), 75 deletions(-) diff --git a/include/lttng/tracepoint.h b/include/lttng/tracepoint.h index 785c87e5..fb635c11 100644 --- a/include/lttng/tracepoint.h +++ b/include/lttng/tracepoint.h @@ -213,6 +213,75 @@ struct tracepoint_dlopen { extern struct tracepoint_dlopen tracepoint_dlopen; +#if defined(TRACEPOINT_DEFINE) || defined(TRACEPOINT_CREATE_PROBES) + +/* + * These weak symbols, the constructor, and destructor take care of + * registering only _one_ instance of the tracepoints per shared-ojbect + * (or for the whole main program). + */ +int __tracepoint_registered + __attribute__((weak, visibility("hidden"))); +int __tracepoint_ptrs_registered + __attribute__((weak, visibility("hidden"))); +struct tracepoint_dlopen tracepoint_dlopen + __attribute__((weak, visibility("hidden"))); + +static void lttng_ust_notrace __attribute__((constructor)) +__tracepoints__init(void); +static void +__tracepoints__init(void) +{ + if (__tracepoint_registered++) + return; + + if (!tracepoint_dlopen.liblttngust_handle) + tracepoint_dlopen.liblttngust_handle = + dlopen("liblttng-ust-tracepoint.so.0", RTLD_NOW | RTLD_GLOBAL); + if (!tracepoint_dlopen.liblttngust_handle) + return; + tracepoint_dlopen.tracepoint_register_lib = + URCU_FORCE_CAST(int (*)(struct tracepoint * const *, int), + dlsym(tracepoint_dlopen.liblttngust_handle, + "tracepoint_register_lib")); + tracepoint_dlopen.tracepoint_unregister_lib = + URCU_FORCE_CAST(int (*)(struct tracepoint * const *), + dlsym(tracepoint_dlopen.liblttngust_handle, + "tracepoint_unregister_lib")); +#ifndef _LGPL_SOURCE + tracepoint_dlopen.rcu_read_lock_sym_bp = + URCU_FORCE_CAST(void (*)(void), + dlsym(tracepoint_dlopen.liblttngust_handle, + "tp_rcu_read_lock_bp")); + tracepoint_dlopen.rcu_read_unlock_sym_bp = + URCU_FORCE_CAST(void (*)(void), + dlsym(tracepoint_dlopen.liblttngust_handle, + "tp_rcu_read_unlock_bp")); + tracepoint_dlopen.rcu_dereference_sym_bp = + URCU_FORCE_CAST(void *(*)(void *p), + dlsym(tracepoint_dlopen.liblttngust_handle, + "tp_rcu_dereference_sym_bp")); +#endif +} + +static void lttng_ust_notrace __attribute__((destructor)) +__tracepoints__destroy(void); +static void +__tracepoints__destroy(void) +{ + int ret; + + if (--__tracepoint_registered) + return; + if (tracepoint_dlopen.liblttngust_handle && !__tracepoint_ptrs_registered) { + ret = dlclose(tracepoint_dlopen.liblttngust_handle); + assert(!ret); + memset(&tracepoint_dlopen, 0, sizeof(tracepoint_dlopen)); + } +} + +#endif + #ifdef TRACEPOINT_DEFINE /* @@ -265,101 +334,46 @@ extern struct tracepoint * const __stop___tracepoints_ptrs[] __attribute__((used, section("__tracepoints_ptrs"))) = \ &__tracepoint_##_provider##___##_name; -static inline void __tracepoints__init_define(void) -{ - tracepoint_dlopen.tracepoint_register_lib(__start___tracepoints_ptrs, - __stop___tracepoints_ptrs - - __start___tracepoints_ptrs); -} - -static inline void __tracepoints__destroy_define(void) -{ - if (tracepoint_dlopen.tracepoint_unregister_lib) - tracepoint_dlopen.tracepoint_unregister_lib(__start___tracepoints_ptrs); -} - - -#else /* TRACEPOINT_DEFINE */ - -#define _DEFINE_TRACEPOINT(_provider, _name, _args) - -static inline void __tracepoints__init_define(void) -{ -} - -static inline void __tracepoints__destroy_define(void) -{ -} - -#endif /* #else TRACEPOINT_DEFINE */ - -#if defined(TRACEPOINT_DEFINE) || defined(TRACEPOINT_CREATE_PROBES) - -/* - * These weak symbols, the constructor, and destructor take care of - * registering only _one_ instance of the tracepoints per shared-ojbect - * (or for the whole main program). - */ -int __tracepoint_registered - __attribute__((weak, visibility("hidden"))); -struct tracepoint_dlopen tracepoint_dlopen - __attribute__((weak, visibility("hidden"))); - static void lttng_ust_notrace __attribute__((constructor)) -__tracepoints__init(void); +__tracepoints__ptrs_init(void); static void -__tracepoints__init(void) +__tracepoints__ptrs_init(void) { - if (__tracepoint_registered++) + if (__tracepoint_ptrs_registered++) return; - - tracepoint_dlopen.liblttngust_handle = - dlopen("liblttng-ust-tracepoint.so.0", RTLD_NOW | RTLD_GLOBAL); + if (!tracepoint_dlopen.liblttngust_handle) + tracepoint_dlopen.liblttngust_handle = + dlopen("liblttng-ust-tracepoint.so.0", RTLD_NOW | RTLD_GLOBAL); if (!tracepoint_dlopen.liblttngust_handle) return; - tracepoint_dlopen.tracepoint_register_lib = - URCU_FORCE_CAST(int (*)(struct tracepoint * const *, int), - dlsym(tracepoint_dlopen.liblttngust_handle, - "tracepoint_register_lib")); - tracepoint_dlopen.tracepoint_unregister_lib = - URCU_FORCE_CAST(int (*)(struct tracepoint * const *), - dlsym(tracepoint_dlopen.liblttngust_handle, - "tracepoint_unregister_lib")); -#ifndef _LGPL_SOURCE - tracepoint_dlopen.rcu_read_lock_sym_bp = - URCU_FORCE_CAST(void (*)(void), - dlsym(tracepoint_dlopen.liblttngust_handle, - "tp_rcu_read_lock_bp")); - tracepoint_dlopen.rcu_read_unlock_sym_bp = - URCU_FORCE_CAST(void (*)(void), - dlsym(tracepoint_dlopen.liblttngust_handle, - "tp_rcu_read_unlock_bp")); - tracepoint_dlopen.rcu_dereference_sym_bp = - URCU_FORCE_CAST(void *(*)(void *p), - dlsym(tracepoint_dlopen.liblttngust_handle, - "tp_rcu_dereference_sym_bp")); -#endif - __tracepoints__init_define(); + tracepoint_dlopen.tracepoint_register_lib(__start___tracepoints_ptrs, + __stop___tracepoints_ptrs - + __start___tracepoints_ptrs); } static void lttng_ust_notrace __attribute__((destructor)) -__tracepoints__destroy(void); +__tracepoints__ptrs_destroy(void); static void -__tracepoints__destroy(void) +__tracepoints__ptrs_destroy(void) { int ret; - if (--__tracepoint_registered) + if (--__tracepoint_ptrs_registered) return; - __tracepoints__destroy_define(); - if (tracepoint_dlopen.liblttngust_handle) { + if (tracepoint_dlopen.tracepoint_unregister_lib) + tracepoint_dlopen.tracepoint_unregister_lib(__start___tracepoints_ptrs); + if (tracepoint_dlopen.liblttngust_handle && !__tracepoint_registered) { ret = dlclose(tracepoint_dlopen.liblttngust_handle); assert(!ret); memset(&tracepoint_dlopen, 0, sizeof(tracepoint_dlopen)); } } -#endif +#else /* TRACEPOINT_DEFINE */ + +#define _DEFINE_TRACEPOINT(_provider, _name, _args) + +#endif /* #else TRACEPOINT_DEFINE */ #ifdef __cplusplus } -- 2.34.1