From: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
In order to move pointer checks like IS_ERR_VALUE() out of the hotpath
and into the reader path of a trace event, user space tools need to be
able to parse that. IS_ERR_VALUE() is defined as:
#define IS_ERR_VALUE() unlikely((unsigned long)(void *)(x) >= (unsigned long)-MAX_ERRNO)
Which eventually turns into:
__builtin_expect(!!((unsigned long)(void *)(x) >= (unsigned long)-4095), 0)
Now the traceevent parser can handle most of that except for the
__builtin_expect(), which needs to be added.
Link: https://lore.kernel.org/linux-mm/20200320055823.27089-3-jaewon31.kim@xxxxxxxxxxx/
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Jaewon Kim <jaewon31.kim@xxxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Kees Kook <keescook@xxxxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: linux-mm@xxxxxxxxx
Cc: linux-trace-devel@xxxxxxxxxxxxxxx
Link: http://lore.kernel.org/lkml/20200324200956.821799393@xxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@xxxxxxxxx>
---
lib/traceevent/event-parse.c | 35 +++++++++++++++++++++++++++++++++++
1 file changed, 35 insertions(+)
diff --git a/lib/traceevent/event-parse.c b/lib/traceevent/event-parse.c
index 7e9cd9bb..ee16be96 100644
--- a/lib/traceevent/event-parse.c
+++ b/lib/traceevent/event-parse.c
@@ -3084,6 +3084,37 @@ err:
return TEP_EVENT_ERROR;
}
+static enum tep_event_type
+process_builtin_expect(struct tep_event *event, struct tep_print_arg *arg, char **tok)
+{
+ enum tep_event_type type;
+ char *token = NULL;
+
+ /* Handle __builtin_expect( cond, #) */
+ type = process_arg(event, arg, &token);
+
+ if (type != TEP_EVENT_DELIM || token[0] != ',')
+ goto out_free;
+
+ free_token(token);
+
+ /* We don't care what the second parameter is of the __builtin_expect() */
+ if (read_expect_type(TEP_EVENT_ITEM, &token) < 0)
+ goto out_free;
+
+ if (read_expected(TEP_EVENT_DELIM, ")") < 0)
+ goto out_free;
+
+ free_token(token);
+ type = read_token_item(tok);
+ return type;
+
+out_free:
+ free_token(token);
+ *tok = NULL;
+ return TEP_EVENT_ERROR;
+}
+
static enum tep_event_type
process_function(struct tep_event *event, struct tep_print_arg *arg,
char *token, char **tok)
@@ -3128,6 +3159,10 @@ process_function(struct tep_event *event, struct tep_print_arg *arg,
free_token(token);
return process_dynamic_array_len(event, arg, tok);
}
+ if (strcmp(token, "__builtin_expect") == 0) {
+ free_token(token);
+ return process_builtin_expect(event, arg, tok);
+ }
func = find_func_handler(event->tep, token);
if (func) {
--
2.26.2
|