Commit 1b20d949 authored Mar 24, 2020 by Steven Rostedt (VMware) Committed by Arnaldo Carvalho de Melo Jun 18, 2020

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>

parent 74621d92

tools/lib/traceevent/event-parse.c

+35 −0

Original line number	Diff line number	Diff line
		@@ -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) {

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