perf tools: Ensure comm string is properly terminated

If threads in a multi-threaded process have names shorter than the main
thread the comm for the named threads is not properly terminated.

E.g., for the process 'namedthreads' where each thread is named noploop%d
where %d is the thread number:

Before:
    perf script -f comm,tid,ip,sym,dso
    noploop:4ads 21616  400a49 noploop (/tmp/namedthreads)
The 'ads' in the thread comm bleeds over from the process name.

After:
    perf script -f comm,tid,ip,sym,dso
       noploop:4 21616  400a49 noploop (/tmp/namedthreads)

Cc: Frederic Weisbecker <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: David Ahern <[email protected]>
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
index 2044324b755a51bc9b41536957dce8b35a11a6fd..2a6f33cd888ca7d7e9dbe7d27f6999a552dec7f1 100644 (file)
--- a/tools/perf/util/event.c
+++ b/tools/perf/util/event.c
@@ -74,6 +74,7 @@ static pid_t perf_event__get_comm_tgid(pid_t pid, char *comm, size_t len)
                        if (size >= len)
                                size = len - 1;
                        memcpy(comm, name, size);
+                       comm[size] = '\0';
 
                } else if (memcmp(bf, "Tgid:", 5) == 0) {
                        char *tgids = bf + 5;