From 8579aca3f9a8f890d6d94ccaed7cf5fd54a0c3bd Mon Sep 17 00:00:00 2001 From: Taeung Song Date: Fri, 26 Feb 2016 00:12:59 +0900 Subject: [PATCH] perf script: Exception handling when the print fmt is empty After collecting samples for events 'syscalls:', perf-script with python script doesn't occasionally work generating a segmentation fault. The reason is that the print fmt is empty and a value of event->print_fmt.args is NULL, so dereferencing the null pointer results in a segmentation fault i.e.: # perf record -e syscalls:* # perf script -g python # perf script -s perf-script.py in trace_begin syscalls__sys_enter_brk 3 79841.832099154 3777 test.sh syscall_nr=12, brk=0 ... (omitted) ... Segmentation fault (core dumped) For example, a format of sys_enter_getuid() hasn't print fmt as below. # cat /sys/kernel/debug/tracing/events/syscalls/sys_enter_getuid/format name: sys_enter_getuid ID: 188 format: field:unsigned short common_type; offset:0; size:2; signed:0; field:unsigned char common_flags; offset:2; size:1; signed:0; field:unsigned char common_preempt_count; offset:3; size:1; signed:0; field:int common_pid; offset:4; size:4; signed:1; field:int syscall_nr; offset:8; size:4; signed:1; print fmt: "" So add exception handling to avoid this problem. Signed-off-by: Taeung Song Tested-by: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Namhyung Kim Cc: Wang Nan Link: http://lkml.kernel.org/r/1456413179-12331-1-git-send-email-treeze.taeung@gmail.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/scripting-engines/trace-event-perl.c | 3 +++ tools/perf/util/scripting-engines/trace-event-python.c | 3 +++ 2 files changed, 6 insertions(+) diff --git a/tools/perf/util/scripting-engines/trace-event-perl.c b/tools/perf/util/scripting-engines/trace-event-perl.c index 544509c159ce..b3aabc0d4eb0 100644 --- a/tools/perf/util/scripting-engines/trace-event-perl.c +++ b/tools/perf/util/scripting-engines/trace-event-perl.c @@ -187,6 +187,9 @@ static void define_event_symbols(struct event_format *event, const char *ev_name, struct print_arg *args) { + if (args == NULL) + return; + switch (args->type) { case PRINT_NULL: break; diff --git a/tools/perf/util/scripting-engines/trace-event-python.c b/tools/perf/util/scripting-engines/trace-event-python.c index d72fafc1c800..309d90fa7698 100644 --- a/tools/perf/util/scripting-engines/trace-event-python.c +++ b/tools/perf/util/scripting-engines/trace-event-python.c @@ -205,6 +205,9 @@ static void define_event_symbols(struct event_format *event, const char *ev_name, struct print_arg *args) { + if (args == NULL) + return; + switch (args->type) { case PRINT_NULL: break; -- 2.20.1