tracepoints: export pointer array

Fixes odd alignment issues between linker and compiler, caused by compiler
using larger alignment values than expected for structures -- and the linker
adding unexpected padding within the sections. Use the same technique recently
introduced for Linux kernel tracepoints.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/include/ust/tracepoint.h b/include/ust/tracepoint.h
index 1d286a0ff995432bb16e047fb78fc09d6ab5a05b..05e5c11dd902c0c01ae2713b3d1d44952fd9dcc5 100644 (file)
--- a/include/ust/tracepoint.h
+++ b/include/ust/tracepoint.h
@@ -42,12 +42,7 @@ struct tracepoint {
        const char *name;               /* Tracepoint name */
        DEFINE_IMV(char, state);        /* State. */
        struct probe *probes;
-} __attribute__((aligned(32)));                /*
-                                        * Aligned on 32 bytes because it is
-                                        * globally visible and gcc happily
-                                        * align these on the structure size.
-                                        * Keep in sync with vmlinux.lds.h.
-                                        */
+};
 
 #define PARAMS(args...) args
 
@@ -128,18 +123,21 @@ struct tracepoint {
                                                   data);               \
        }
 
-#define DEFINE_TRACE_FN(name, reg, unreg)                                      \
+#define DEFINE_TRACE_FN(name, reg, unreg)                              \
        static const char __tpstrtab_##name[]                           \
        __attribute__((section("__tracepoints_strings"))) = #name;      \
        struct tracepoint __tracepoint_##name                           \
-       __attribute__((section("__tracepoints"), aligned(32))) =        \
-               { __tpstrtab_##name, 0, NULL }
+       __attribute__((section("__tracepoints"))) =                     \
+               { __tpstrtab_##name, 0, NULL };                         \
+       static struct tracepoint * const __tracepoint_ptr_##name        \
+       __attribute__((used, section("__tracepoints_ptrs"))) =          \
+               &__tracepoint_##name;
 
 #define DEFINE_TRACE(name)                                             \
-       DEFINE_TRACE_FN(name, NULL, NULL);
+       DEFINE_TRACE_FN(name, NULL, NULL)
 
-extern void tracepoint_update_probe_range(struct tracepoint *begin,
-       struct tracepoint *end);
+extern void tracepoint_update_probe_range(struct tracepoint * const *begin,
+       struct tracepoint * const *end);
 
 #else /* !CONFIG_TRACEPOINTS */
 #define __DECLARE_TRACE(name, proto, args)                             \
@@ -147,11 +145,11 @@ extern void tracepoint_update_probe_range(struct tracepoint *begin,
        { }                                                             \
        static inline void _trace_##name(proto)                         \
        { }                                                             \
-       static inline int register_trace_##name(void (*probe)(proto))   \
+       static inline int register_trace_##name(void (*probe)(proto), void *data)       \
        {                                                               \
                return -ENOSYS;                                         \
        }                                                               \
-       static inline int unregister_trace_##name(void (*probe)(proto)) \
+       static inline int unregister_trace_##name(void (*probe)(proto), void *data)     \
        {                                                               \
                return -ENOSYS;                                         \
        }
@@ -191,15 +189,15 @@ extern void tracepoint_probe_update_all(void);
 struct tracepoint_iter {
 //ust//        struct module *module;
        struct tracepoint_lib *lib;
-       struct tracepoint *tracepoint;
+       struct tracepoint * const *tracepoint;
 };
 
 extern void tracepoint_iter_start(struct tracepoint_iter *iter);
 extern void tracepoint_iter_next(struct tracepoint_iter *iter);
 extern void tracepoint_iter_stop(struct tracepoint_iter *iter);
 extern void tracepoint_iter_reset(struct tracepoint_iter *iter);
-extern int tracepoint_get_iter_range(struct tracepoint **tracepoint,
-       struct tracepoint *begin, struct tracepoint *end);
+extern int tracepoint_get_iter_range(struct tracepoint * const **tracepoint,
+       struct tracepoint * const *begin, struct tracepoint * const *end);
 
 /*
  * tracepoint_synchronize_unregister must be called between the last tracepoint
@@ -212,22 +210,22 @@ static inline void tracepoint_synchronize_unregister(void)
 }
 
 struct tracepoint_lib {
-       struct tracepoint *tracepoints_start;
+       struct tracepoint * const *tracepoints_start;
        int tracepoints_count;
        struct cds_list_head list;
 };
 
-extern int tracepoint_register_lib(struct tracepoint *tracepoints_start,
+extern int tracepoint_register_lib(struct tracepoint * const *tracepoints_start,
                                   int tracepoints_count);
-extern int tracepoint_unregister_lib(struct tracepoint *tracepoints_start);
+extern int tracepoint_unregister_lib(struct tracepoint * const *tracepoints_start);
 
 #define TRACEPOINT_LIB                                                 \
-       extern struct tracepoint __start___tracepoints[] __attribute__((weak, visibility("hidden"))); \
-       extern struct tracepoint __stop___tracepoints[] __attribute__((weak, visibility("hidden"))); \
+       extern struct tracepoint * const __start___tracepoints[] __attribute__((weak, visibility("hidden"))); \
+       extern struct tracepoint * const __stop___tracepoints[] __attribute__((weak, visibility("hidden"))); \
        static void __attribute__((constructor)) __tracepoints__init(void) \
        {                                                               \
                tracepoint_register_lib(__start___tracepoints,          \
-                                       (((long)__stop___tracepoints)-((long)__start___tracepoints))/sizeof(struct tracepoint)); \
+                                       (((long)__stop___tracepoints)-((long)__start___tracepoints)) / sizeof(*__start___tracepoints)); \
        } \
        \
        static void __attribute__((destructor)) __tracepoints__destroy(void) \

diff --git a/libust/tracepoint.c b/libust/tracepoint.c
index 47d3785a1a1bede84f356cefdf45736a7d037601..ca40902494f61b9785a1e0b863852dca4694aff3 100644 (file)
--- a/libust/tracepoint.c
+++ b/libust/tracepoint.c
@@ -287,24 +287,24 @@ static void disable_tracepoint(struct tracepoint *elem)
  *
  * Updates the probe callback corresponding to a range of tracepoints.
  */
-void tracepoint_update_probe_range(struct tracepoint *begin,
-                                  struct tracepoint *end)
+void tracepoint_update_probe_range(struct tracepoint * const *begin,
+                                  struct tracepoint * const *end)
 {
-       struct tracepoint *iter;
+       struct tracepoint * const *iter;
        struct tracepoint_entry *mark_entry;
 
        pthread_mutex_lock(&tracepoints_mutex);
        for (iter = begin; iter < end; iter++) {
-               if (!iter->name) {
-                       disable_tracepoint(iter);
+               if (!(*iter)->name) {
+                       disable_tracepoint(*iter);
                        continue;
                }
-               mark_entry = get_tracepoint(iter->name);
+               mark_entry = get_tracepoint((*iter)->name);
                if (mark_entry) {
-                       set_tracepoint(&mark_entry, iter,
+                       set_tracepoint(&mark_entry, *iter,
                                        !!mark_entry->refcount);
                } else {
-                       disable_tracepoint(iter);
+                       disable_tracepoint(*iter);
                }
        }
        pthread_mutex_unlock(&tracepoints_mutex);
@@ -547,8 +547,8 @@ int lib_get_iter_tracepoints(struct tracepoint_iter *iter)
  * Will return the first tracepoint in the range if the input tracepoint is
  * NULL.
  */
-int tracepoint_get_iter_range(struct tracepoint **tracepoint,
-       struct tracepoint *begin, struct tracepoint *end)
+int tracepoint_get_iter_range(struct tracepoint * const **tracepoint,
+       struct tracepoint * const *begin, struct tracepoint * const *end)
 {
        if (!*tracepoint && begin != end) {
                *tracepoint = begin;
@@ -648,17 +648,17 @@ void tracepoint_set_new_tracepoint_cb(void (*cb)(struct tracepoint *))
        new_tracepoint_cb = cb;
 }
 
-static void new_tracepoints(struct tracepoint *start, struct tracepoint *end)
+static void new_tracepoints(struct tracepoint * const *start, struct tracepoint * const *end)
 {
-       if(new_tracepoint_cb) {
-               struct tracepoint *t;
+       if (new_tracepoint_cb) {
+               struct tracepoint * const *t;
                for(t=start; t < end; t++) {
-                       new_tracepoint_cb(t);
+                       new_tracepoint_cb(*t);
                }
        }
 }
 
-int tracepoint_register_lib(struct tracepoint *tracepoints_start, int tracepoints_count)
+int tracepoint_register_lib(struct tracepoint * const *tracepoints_start, int tracepoints_count)
 {
        struct tracepoint_lib *pl;
 
@@ -682,14 +682,14 @@ int tracepoint_register_lib(struct tracepoint *tracepoints_start, int tracepoint
        return 0;
 }
 
-int tracepoint_unregister_lib(struct tracepoint *tracepoints_start)
+int tracepoint_unregister_lib(struct tracepoint * const *tracepoints_start)
 {
        struct tracepoint_lib *lib;
 
        pthread_mutex_lock(&tracepoints_mutex);
 
        cds_list_for_each_entry(lib, &libs, list) {
-               if(lib->tracepoints_start == tracepoints_start) {
+               if (lib->tracepoints_start == tracepoints_start) {
                        struct tracepoint_lib *lib2free = lib;
                        cds_list_del(&lib->list);
                        free(lib2free);