tracing: add run-time field descriptions for event filtering

This patch makes the field descriptions defined for event tracing
available at run-time, for the event-filtering mechanism introduced
in a subsequent patch.

The common event fields are prepended with 'common_' in the format
display, allowing them to be distinguished from the other fields
that might internally have same name and can therefore be
unambiguously used in filters.

Signed-off-by: Tom Zanussi <tzanussi@gmail.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1237710639.7703.46.camel@charm-linux>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

4 files changed, 107 insertions, 10 deletions

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 7cfb741be200..9288dc7ad14f 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -775,16 +775,26 @@ enum {
         TRACE_EVENT_TYPE_RAW            = 2,
 };
 
+struct ftrace_event_field {
+        struct list_head        link;
+        char                    *name;
+        char                    *type;
+        int                     offset;
+        int                     size;
+};
+
 struct ftrace_event_call {
-        char            *name;
-        char            *system;
-        struct dentry   *dir;
-        int             enabled;
-        int             (*regfunc)(void);
-        void            (*unregfunc)(void);
-        int             id;
-        int             (*raw_init)(void);
-        int             (*show_format)(struct trace_seq *s);
+        char                    *name;
+        char                    *system;
+        struct dentry           *dir;
+        int                     enabled;
+        int                     (*regfunc)(void);
+        void                    (*unregfunc)(void);
+        int                     id;
+        int                     (*raw_init)(void);
+        int                     (*show_format)(struct trace_seq *s);
+        int                     (*define_fields)(void);
+        struct list_head        fields;
 
 #ifdef CONFIG_EVENT_PROFILE
         atomic_t        profile_count;
@@ -793,6 +803,8 @@ struct ftrace_event_call {
 #endif
 };
 
+int trace_define_field(struct ftrace_event_call *call, char *type,
+                       char *name, int offset, int size);
 void event_trace_printk(unsigned long ip, const char *fmt, ...);
 extern struct ftrace_event_call __start_ftrace_events[];
 extern struct ftrace_event_call __stop_ftrace_events[];
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 3047b56f6637..961b057da28b 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -19,6 +19,34 @@
 
 static DEFINE_MUTEX(event_mutex);
 
+int trace_define_field(struct ftrace_event_call *call, char *type,
+                       char *name, int offset, int size)
+{
+        struct ftrace_event_field *field;
+
+        field = kmalloc(sizeof(*field), GFP_KERNEL);
+        if (!field)
+                goto err;
+        field->name = kstrdup(name, GFP_KERNEL);
+        if (!field->name)
+                goto err;
+        field->type = kstrdup(type, GFP_KERNEL);
+        if (!field->type)
+                goto err;
+        field->offset = offset;
+        field->size = size;
+        list_add(&field->link, &call->fields);
+
+        return 0;
+err:
+        if (field) {
+                kfree(field->name);
+                kfree(field->type);
+        }
+        kfree(field);
+        return -ENOMEM;
+}
+
 static void ftrace_clear_events(void)
 {
         struct ftrace_event_call *call = (void *)__start_ftrace_events;
@@ -343,7 +371,8 @@ event_enable_write(struct file *filp, const char __user *ubuf, size_t cnt,
 
 #undef FIELD
 #define FIELD(type, name)                                               \
-        #type, #name, offsetof(typeof(field), name), sizeof(field.name)
+        #type, "common_" #name, offsetof(typeof(field), name),          \
+                sizeof(field.name)
 
 static int trace_write_header(struct trace_seq *s)
 {
@@ -581,6 +610,15 @@ event_create_dir(struct ftrace_event_call *call, struct dentry *d_events)
                                         call->name);
         }
 
+        if (call->define_fields) {
+                ret = call->define_fields();
+                if (ret < 0) {
+                        pr_warning("Could not initialize trace point"
+                                   " events/%s\n", call->name);
+                        return ret;
+                }
+        }
+
         /* A trace may not want to export its format */
         if (!call->show_format)
                 return 0;
diff --git a/kernel/trace/trace_events_stage_2.h b/kernel/trace/trace_events_stage_2.h
index 5117c43f5c67..30743f7d4110 100644
--- a/kernel/trace/trace_events_stage_2.h
+++ b/kernel/trace/trace_events_stage_2.h
@@ -129,3 +129,48 @@ ftrace_format_##call(struct trace_seq *s)				\
 }
 
 #include <trace/trace_event_types.h>
+
+#undef __field
+#define __field(type, item)                                             \
+        ret = trace_define_field(event_call, #type, #item,              \
+                                 offsetof(typeof(field), item),         \
+                                 sizeof(field.item));                   \
+        if (ret)                                                        \
+                return ret;
+
+#undef __array
+#define __array(type, item, len)                                        \
+        ret = trace_define_field(event_call, #type "[" #len "]", #item, \
+                                 offsetof(typeof(field), item),         \
+                                 sizeof(field.item));                   \
+        if (ret)                                                        \
+                return ret;
+
+#define __common_field(type, item)                                      \
+        ret = trace_define_field(event_call, #type, "common_" #item,    \
+                                 offsetof(typeof(field.ent), item),     \
+                                 sizeof(field.ent.item));               \
+        if (ret)                                                        \
+                return ret;
+
+#undef TRACE_EVENT
+#define TRACE_EVENT(call, proto, args, tstruct, func, print)            \
+int                                                                     \
+ftrace_define_fields_##call(void)                                       \
+{                                                                       \
+        struct ftrace_raw_##call field;                                 \
+        struct ftrace_event_call *event_call = &event_##call;           \
+        int ret;                                                        \
+                                                                        \
+        __common_field(unsigned char, type);                            \
+        __common_field(unsigned char, flags);                           \
+        __common_field(unsigned char, preempt_count);                   \
+        __common_field(int, pid);                                       \
+        __common_field(int, tgid);                                      \
+                                                                        \
+        tstruct;                                                        \
+                                                                        \
+        return ret;                                                     \
+}
+
+#include <trace/trace_event_types.h>
diff --git a/kernel/trace/trace_events_stage_3.h b/kernel/trace/trace_events_stage_3.h
index 6b3261ca988c..468938f70141 100644
--- a/kernel/trace/trace_events_stage_3.h
+++ b/kernel/trace/trace_events_stage_3.h
@@ -252,6 +252,7 @@ static int ftrace_raw_init_event_##call(void)				\
         if (!id)                                                        \
                 return -ENODEV;                                         \
         event_##call.id = id;                                           \
+        INIT_LIST_HEAD(&event_##call.fields);                           \
         return 0;                                                       \
 }                                                                       \
                                                                         \
@@ -264,6 +265,7 @@ __attribute__((section("_ftrace_events"))) event_##call = {		\
         .regfunc                = ftrace_raw_reg_event_##call,          \
         .unregfunc              = ftrace_raw_unreg_event_##call,        \
         .show_format            = ftrace_format_##call,                 \
+        .define_fields          = ftrace_define_fields_##call,          \
         _TRACE_PROFILE_INIT(call)                                       \
 }