tools lib traceevent: Add handler for __builtin_expect()

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@samsung.com/
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jaewon Kim <jaewon31.kim@samsung.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kees Kook <keescook@chromium.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: linux-mm@kvack.org
Cc: linux-trace-devel@vger.kernel.org
Link: http://lore.kernel.org/lkml/20200324200956.821799393@goodmis.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/lib/traceevent/event-parse.c b/tools/lib/traceevent/event-parse.c
index 010e60d..5b36c58 100644 (file)
--- a/tools/lib/traceevent/event-parse.c
+++ b/tools/lib/traceevent/event-parse.c
@@ -3085,6 +3085,37 @@ err:
 }
 
 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) {