[tip:perf/urgent] tools lib traceevent: Fix missing equality check for strcmp

[tip-bot for Rikard Falkeborn]

Commit-ID:  ff4f5471801f879aea8f9e3ace2b9af31efc9178
Gitweb:     https://git.kernel.org/tip/ff4f5471801f879aea8f9e3ace2b9af31efc9178
Author:     Rikard Falkeborn <rikard.falkeborn@xxxxxxxxx>
AuthorDate: Tue, 9 Apr 2019 11:15:29 +0200
Committer:  Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Tue, 9 Apr 2019 11:55:30 -0300

tools lib traceevent: Fix missing equality check for strcmp

There was a missing comparison with 0 when checking if type is "s64" or
"u64". Therefore, the body of the if-statement was entered if "type" was
"u64" or not "s64", which made the first strcmp() redundant since if
type is "u64", it's not "s64".

If type is "s64", the body of the if-statement is not entered but since
the remainder of the function consists of if-statements which will not
be entered if type is "s64", we will just return "val", which is
correct, albeit at the cost of a few more calls to strcmp(), i.e., it
will behave just as if the if-statement was entered.

If type is neither "s64" or "u64", the body of the if-statement will be
entered incorrectly and "val" returned. This means that any type that is
checked after "s64" and "u64" is handled the same way as "s64" and
"u64", i.e., the limiting of "val" to fit in for example "s8" is never
reached.

This was introduced in the kernel tree when the sources were copied from
trace-cmd in commit f7d82350e597 ("tools/events: Add files to create
libtraceevent.a"), and in the trace-cmd repo in 1cdbae6035cei
("Implement typecasting in parser") when the function was introduced,
i.e., it has always behaved the wrong way.

Detected by cppcheck.

Signed-off-by: Rikard Falkeborn <rikard.falkeborn@xxxxxxxxx>
Reviewed-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Cc: Tzvetomir Stoyanov <tstoyanov@xxxxxxxxxx>
Fixes: f7d82350e597 ("tools/events: Add files to create libtraceevent.a")
Link: http://lkml.kernel.org/r/20190409091529.2686-1-rikard.falkeborn@xxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/lib/traceevent/event-parse.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/lib/traceevent/event-parse.c b/tools/lib/traceevent/event-parse.c
index 87494c7c619d..981c6ce2da2c 100644
--- a/tools/lib/traceevent/event-parse.c
+++ b/tools/lib/traceevent/event-parse.c
@@ -2233,7 +2233,7 @@ eval_type_str(unsigned long long val, const char *type, int pointer)
 		return val & 0xffffffff;
 
 	if (strcmp(type, "u64") == 0 ||
-	    strcmp(type, "s64"))
+	    strcmp(type, "s64") == 0)
 		return val;
 
 	if (strcmp(type, "s8") == 0)