Allow for reading of the format fields of an event by a plugin

Plugins need to find information about the format fields like the
offset and size of the field.

  Added: pevent_find_field(event, name)

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

3 files changed, 71 insertions, 26 deletions

diff --git a/parse-events.c b/parse-events.c
index 1527c2b..f7b8bce 100644
--- a/parse-events.c
+++ b/parse-events.c
@@ -48,8 +48,6 @@ static unsigned long long input_buf_siz;
 static int cpus;
 static int long_size;
 
-static struct format_field *find_field(struct event *event, const char *name);
-
 static void init_input_buf(char *buf, unsigned long long size)
 {
         input_buf = buf;
@@ -1728,7 +1726,7 @@ process_dynamic_array(struct event *event, struct print_arg *arg, char **tok)
 
         /* Find the field */
 
-        field = find_field(event, token);
+        field = pevent_find_field(event, token);
         if (!field)
                 return EVENT_ERROR;
 
@@ -2041,8 +2039,8 @@ find_common_field(struct event *event, const char *name)
         return format;
 }
 
-static struct format_field *
-find_field(struct event *event, const char *name)
+struct format_field *
+pevent_find_field(struct event *event, const char *name)
 {
         struct format_field *format;
 
@@ -2063,7 +2061,7 @@ find_any_field(struct event *event, const char *name)
         format = find_common_field(event, name);
         if (format)
                 return format;
-        return find_field(event, name);
+        return pevent_find_field(event, name);
 }
 
 static unsigned long long read_size(void *ptr, int size)
@@ -2498,10 +2496,10 @@ static struct print_arg *make_bprint_args(char *fmt, void *data, int size, struc
         void *bptr;
 
         if (!field) {
-                field = find_field(event, "buf");
+                field = pevent_find_field(event, "buf");
                 if (!field)
                         die("can't find buffer field for binary printk");
-                ip_field = find_field(event, "ip");
+                ip_field = pevent_find_field(event, "ip");
                 if (!ip_field)
                         die("can't find ip field for binary printk");
         }
@@ -2612,7 +2610,7 @@ get_bprint_format(void *data, int size __unused, struct event *event)
         char *p;
 
         if (!field) {
-                field = find_field(event, "fmt");
+                field = pevent_find_field(event, "fmt");
                 if (!field)
                         die("can't find format field for binary printk");
                 printf("field->offset = %d size=%d\n", field->offset, field->size);
@@ -2941,7 +2939,7 @@ get_return_for_leaf(int cpu, int cur_pid, unsigned long long cur_func,
                 return NULL;
 
         pid = parse_common_pid(next->data);
-        field = find_field(event, "func");
+        field = pevent_find_field(event, "func");
         if (!field)
                 die("function return does not have field func");
 
@@ -3022,12 +3020,12 @@ print_graph_entry_leaf(struct trace_seq *s,
         type = trace_parse_common_type(ret_rec->data);
         ret_event = trace_find_event(type);
 
-        field = find_field(ret_event, "rettime");
+        field = pevent_find_field(ret_event, "rettime");
         if (!field)
                 die("can't find rettime in return graph");
         rettime = read_size(ret_rec->data + field->offset, field->size);
 
-        field = find_field(ret_event, "calltime");
+        field = pevent_find_field(ret_event, "calltime");
         if (!field)
                 die("can't find rettime in return graph");
         calltime = read_size(ret_rec->data + field->offset, field->size);
@@ -3040,7 +3038,7 @@ print_graph_entry_leaf(struct trace_seq *s,
         /* Duration */
         print_graph_duration(s, duration);
 
-        field = find_field(event, "depth");
+        field = pevent_find_field(event, "depth");
         if (!field)
                 die("can't find depth in entry graph");
         depth = read_size(data + field->offset, field->size);
@@ -3049,7 +3047,7 @@ print_graph_entry_leaf(struct trace_seq *s,
         for (i = 0; i < (int)(depth * TRACE_GRAPH_INDENT); i++)
                 trace_seq_putc(s, ' ');
 
-        field = find_field(event, "func");
+        field = pevent_find_field(event, "func");
         if (!field)
                 die("can't find func in entry graph");
         val = read_size(data + field->offset, field->size);
@@ -3076,7 +3074,7 @@ static void print_graph_nested(struct trace_seq *s,
         /* No time */
         trace_seq_puts(s, "           |  ");
 
-        field = find_field(event, "depth");
+        field = pevent_find_field(event, "depth");
         if (!field)
                 die("can't find depth in entry graph");
         depth = read_size(data + field->offset, field->size);
@@ -3085,7 +3083,7 @@ static void print_graph_nested(struct trace_seq *s,
         for (i = 0; i < (int)(depth * TRACE_GRAPH_INDENT); i++)
                 trace_seq_putc(s, ' ');
 
-        field = find_field(event, "func");
+        field = pevent_find_field(event, "func");
         if (!field)
                 die("can't find func in entry graph");
         val = read_size(data + field->offset, field->size);
@@ -3120,7 +3118,7 @@ pretty_print_func_ent(struct trace_seq *s,
                 trace_seq_puts(s, " | ");
         }
 
-        field = find_field(event, "func");
+        field = pevent_find_field(event, "func");
         if (!field)
                 die("function entry does not have func field");
 
@@ -3169,12 +3167,12 @@ pretty_print_func_ret(struct trace_seq *s,
                 trace_seq_puts(s, " | ");
         }
 
-        field = find_field(event, "rettime");
+        field = pevent_find_field(event, "rettime");
         if (!field)
                 die("can't find rettime in return graph");
         rettime = read_size(data + field->offset, field->size);
 
-        field = find_field(event, "calltime");
+        field = pevent_find_field(event, "calltime");
         if (!field)
                 die("can't find calltime in return graph");
         calltime = read_size(data + field->offset, field->size);
@@ -3187,7 +3185,7 @@ pretty_print_func_ret(struct trace_seq *s,
         /* Duration */
         print_graph_duration(s, duration);
 
-        field = find_field(event, "depth");
+        field = pevent_find_field(event, "depth");
         if (!field)
                 die("can't find depth in entry graph");
         depth = read_size(data + field->offset, field->size);
diff --git a/parse-events.h b/parse-events.h
index a29c295..ff597ef 100644
--- a/parse-events.h
+++ b/parse-events.h
@@ -299,6 +299,9 @@ int pevent_parse_event(char *buf, unsigned long size, char *sys);
 int pevent_register_event_handler(int id, char *sys_name, char *event_name,
                                   pevent_event_handler_func func);
 
+struct format_field *pevent_find_field(struct event *event, const char *name);
+
+
 /* for debugging */
 void pevent_print_funcs(void);
 void pevent_print_printk(void);
diff --git a/test_plugin.c b/test_plugin.c
index 3a23556..802c7e0 100644
--- a/test_plugin.c
+++ b/test_plugin.c
@@ -4,13 +4,36 @@
 
 #include "parse-events.h"
 
+static int get_offset(struct trace_seq *s, struct event *event, char *name)
+{
+        struct format_field *field;
+
+        field = pevent_find_field(event, name);
+        if (field)
+                return field->offset;
+
+        trace_seq_printf(s, "CAN'T FIND FIELD \"%s\"", name);
+        return -1;
+}
+
 static int timer_expire_handler(struct trace_seq *s, void *data, int size,
                                 struct event *event)
 {
-        void *hrtimer = data + 16;
-        long long now = *(long long *)(data + 24);
+        void *hrtimer;
+        long long now;
+        int offset;
         int ret;
 
+        offset = get_offset(s, event, "hrtimer");
+        if (offset < 0)
+                return 0;
+        hrtimer = *(void **)(data + offset);
+
+        offset = get_offset(s, event, "now");
+        if (offset < 0)
+                return 0;
+        now = *(long long *)(data + offset);
+
         ret = trace_seq_printf(s, "hrtimer=%p now=%llu",
                                hrtimer, now);
         return ret;
@@ -19,12 +42,33 @@ static int timer_expire_handler(struct trace_seq *s, void *data, int size,
 static int timer_start_handler(struct trace_seq *s, void *data, int size,
                                struct event *event)
 {
-        void *hrtimer = data + 16;
-        void *function = data + 24;
-        long long expires = *(long long *)(data + 32);
-        long long soft = *(long long *)(data + 40);
+        void *hrtimer;
+        void *function;
+        long long expires;
+        long long soft;
+        int offset;
         int ret;
 
+        offset = get_offset(s, event, "hrtimer");
+        if (offset < 0)
+                return 0;
+        hrtimer = *(void **)(data + offset);
+
+        offset = get_offset(s, event, "function");
+        if (offset < 0)
+                return 0;
+        function = *(void **)(data + offset);
+
+        offset = get_offset(s, event, "expires");
+        if (offset < 0)
+                return 0;
+        expires = *(long long *)(data + offset);
+
+        offset = get_offset(s, event, "softexpires");
+        if (offset < 0)
+                return 0;
+        soft = *(long long *)(data + offset);
+
         ret = trace_seq_printf(s, "hrtimer=%p function=%pf expires=%llu softexpires=%llu",
                                hrtimer, function,
                                expires, soft);