[PATCH 2/3] perf script: Exception handling when the print fmt is empty

[PATCH 2/3] perf script: Exception handling when the print fmt is empty

[Taeung Song]

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.

Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Signed-off-by: Taeung Song <treeze.taeung@gmail.com>
---
 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 544509c..b3aabc0 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 d72fafc..309d90f 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;
-- 
2.5.0

Re: [PATCH 2/3] perf script: Exception handling when the print fmt is empty

[Arnaldo Carvalho de Melo]

Em Fri, Feb 26, 2016 at 12:12:59AM +0900, Taeung Song escreveu:
> After collecting samples for events 'syscalls:',
> perf-script with python script doesn't occasionally
> work generating a segmentation fault.

Thanks, applied.

- Arnaldo
 
> 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.
> 
> Cc: Jiri Olsa <jolsa@kernel.org>
> Cc: Wang Nan <wangnan0@huawei.com>
> Signed-off-by: Taeung Song <treeze.taeung@gmail.com>
> ---
>  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 544509c..b3aabc0 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 d72fafc..309d90f 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;
> -- 
> 2.5.0

Re: [PATCH 2/3] perf script: Exception handling when the print fmt is empty

[Taeung Song]

Hi, Arnaldo

On 02/26/2016 12:59 AM, Arnaldo Carvalho de Melo wrote:
> Em Fri, Feb 26, 2016 at 12:12:59AM +0900, Taeung Song escreveu:
>> After collecting samples for events 'syscalls:',
>> perf-script with python script doesn't occasionally
>> work generating a segmentation fault.
>
> Thanks, applied.
>
> - Arnaldo

Thank you!!
Taeung

[tip:perf/core] perf script: Exception handling when the print fmt is empty

[tip-bot for Taeung Song]

Commit-ID:  8579aca3f9a8f890d6d94ccaed7cf5fd54a0c3bd
Gitweb:     http://git.kernel.org/tip/8579aca3f9a8f890d6d94ccaed7cf5fd54a0c3bd
Author:     Taeung Song <treeze.taeung@gmail.com>
AuthorDate: Fri, 26 Feb 2016 00:12:59 +0900
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Thu, 25 Feb 2016 12:54:20 -0300

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 <treeze.taeung@gmail.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1456413179-12331-1-git-send-email-treeze.taeung@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 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 544509c..b3aabc0 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 d72fafc..309d90f 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;