2021-04-21 14:05:38

by Thomas Richter

Subject: [PATCH] [PING] perf ftrace: Command fails on s390

Command 'perf ftrace -v -- ls' fails in s390 (at least 5.12.0rc6).

The root cause is a missing pointer dereference which causes an
array element address to be used as PID.

Fix this by extracting the PID.

Output before:
# ./perf ftrace -v -- ls
function_graph tracer is used
write '-263732416' to tracing/set_ftrace_pid failed: Invalid argument
failed to set ftrace pid
#

Output after:
./perf ftrace -v -- ls
function_graph tracer is used
# tracer: function_graph
#
# CPU DURATION FUNCTION CALLS
# | | | | | | |
4) | rcu_read_lock_sched_held() {
4) 0.552 us | rcu_lockdep_current_cpu_online();
4) 6.124 us | }

Signed-off-by: Thomas Richter <[email protected]>
Reported-by: Alexander Schmidt <[email protected]>
---
tools/perf/builtin-ftrace.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
index d49448a1060c..87cb11a7a3ee 100644
--- a/tools/perf/builtin-ftrace.c
+++ b/tools/perf/builtin-ftrace.c
@@ -289,7 +289,7 @@ static int set_tracing_pid(struct perf_ftrace *ftrace)

for (i = 0; i < perf_thread_map__nr(ftrace->evlist->core.threads); i++) {
scnprintf(buf, sizeof(buf), "%d",
- ftrace->evlist->core.threads->map[i]);
+ perf_thread_map__pid(ftrace->evlist->core.threads, i));
if (append_tracing_file("set_ftrace_pid", buf) < 0)
return -1;
}
--
2.30.2

2021-04-22 01:22:38

by Namhyung Kim

Subject: Re: [PATCH] [PING] perf ftrace: Command fails on s390

Hello,

On Wed, Apr 21, 2021 at 10:03 PM Thomas Richter <[email protected]> wrote:
>
> Command 'perf ftrace -v -- ls' fails in s390 (at least 5.12.0rc6).
>
> The root cause is a missing pointer dereference which causes an
> array element address to be used as PID.
>
> Fix this by extracting the PID.
>
> Output before:
> # ./perf ftrace -v -- ls
> function_graph tracer is used
> write '-263732416' to tracing/set_ftrace_pid failed: Invalid argument
> failed to set ftrace pid
> #
>
> Output after:
> ./perf ftrace -v -- ls
> function_graph tracer is used
> # tracer: function_graph
> #
> # CPU DURATION FUNCTION CALLS
> # | | | | | | |
> 4) | rcu_read_lock_sched_held() {
> 4) 0.552 us | rcu_lockdep_current_cpu_online();
> 4) 6.124 us | }
>
> Signed-off-by: Thomas Richter <[email protected]>
> Reported-by: Alexander Schmidt <[email protected]>

Acked-by: Namhyung Kim <[email protected]>

Thanks,
Namhyung

> ---
> tools/perf/builtin-ftrace.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
> index d49448a1060c..87cb11a7a3ee 100644
> --- a/tools/perf/builtin-ftrace.c
> +++ b/tools/perf/builtin-ftrace.c
> @@ -289,7 +289,7 @@ static int set_tracing_pid(struct perf_ftrace *ftrace)
>
> for (i = 0; i < perf_thread_map__nr(ftrace->evlist->core.threads); i++) {
> scnprintf(buf, sizeof(buf), "%d",
> - ftrace->evlist->core.threads->map[i]);
> + perf_thread_map__pid(ftrace->evlist->core.threads, i));
> if (append_tracing_file("set_ftrace_pid", buf) < 0)
> return -1;
> }
> --
> 2.30.2
>

2021-04-23 13:42:08

by Arnaldo Carvalho de Melo

Subject: Re: [PATCH] [PING] perf ftrace: Command fails on s390

Em Wed, Apr 21, 2021 at 02:04:00PM +0200, Thomas Richter escreveu:
> Command 'perf ftrace -v -- ls' fails in s390 (at least 5.12.0rc6).
>
> The root cause is a missing pointer dereference which causes an
> array element address to be used as PID.
>
> Fix this by extracting the PID.

Thanks, applied.

- Arnaldo


> Output before:
> # ./perf ftrace -v -- ls
> function_graph tracer is used
> write '-263732416' to tracing/set_ftrace_pid failed: Invalid argument
> failed to set ftrace pid
> #
>
> Output after:
> ./perf ftrace -v -- ls
> function_graph tracer is used
> # tracer: function_graph
> #
> # CPU DURATION FUNCTION CALLS
> # | | | | | | |
> 4) | rcu_read_lock_sched_held() {
> 4) 0.552 us | rcu_lockdep_current_cpu_online();
> 4) 6.124 us | }
>
> Signed-off-by: Thomas Richter <[email protected]>
> Reported-by: Alexander Schmidt <[email protected]>
> ---
> tools/perf/builtin-ftrace.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
> index d49448a1060c..87cb11a7a3ee 100644
> --- a/tools/perf/builtin-ftrace.c
> +++ b/tools/perf/builtin-ftrace.c
> @@ -289,7 +289,7 @@ static int set_tracing_pid(struct perf_ftrace *ftrace)
>
> for (i = 0; i < perf_thread_map__nr(ftrace->evlist->core.threads); i++) {
> scnprintf(buf, sizeof(buf), "%d",
> - ftrace->evlist->core.threads->map[i]);
> + perf_thread_map__pid(ftrace->evlist->core.threads, i));
> if (append_tracing_file("set_ftrace_pid", buf) < 0)
> return -1;
> }
> --
> 2.30.2
>

--

- Arnaldo

2021-04-23 19:03:38

by Arnaldo Carvalho de Melo

Subject: Re: [PATCH] [PING] perf ftrace: Command fails on s390

Em Wed, Apr 21, 2021 at 02:04:00PM +0200, Thomas Richter escreveu:
> Command 'perf ftrace -v -- ls' fails in s390 (at least 5.12.0rc6).
>
> The root cause is a missing pointer dereference which causes an
> array element address to be used as PID.

Since you pinged on this one, and rightly so, please CC:

From the MAINTAINERS file:

PERFORMANCE EVENTS SUBSYSTEM
R: Jiri Olsa <[email protected]>
R: Namhyung Kim <[email protected]>

These reviewers that help me into getting patches processed.

Patch is processed now, good catch, I collected Namhyung's Acked-by.

Thanks,

- Arnaldo


> Fix this by extracting the PID.
>
> Output before:
> # ./perf ftrace -v -- ls
> function_graph tracer is used
> write '-263732416' to tracing/set_ftrace_pid failed: Invalid argument
> failed to set ftrace pid
> #
>
> Output after:
> ./perf ftrace -v -- ls
> function_graph tracer is used
> # tracer: function_graph
> #
> # CPU DURATION FUNCTION CALLS
> # | | | | | | |
> 4) | rcu_read_lock_sched_held() {
> 4) 0.552 us | rcu_lockdep_current_cpu_online();
> 4) 6.124 us | }
>
> Signed-off-by: Thomas Richter <[email protected]>
> Reported-by: Alexander Schmidt <[email protected]>
> ---
> tools/perf/builtin-ftrace.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
> index d49448a1060c..87cb11a7a3ee 100644
> --- a/tools/perf/builtin-ftrace.c
> +++ b/tools/perf/builtin-ftrace.c
> @@ -289,7 +289,7 @@ static int set_tracing_pid(struct perf_ftrace *ftrace)
>
> for (i = 0; i < perf_thread_map__nr(ftrace->evlist->core.threads); i++) {
> scnprintf(buf, sizeof(buf), "%d",
> - ftrace->evlist->core.threads->map[i]);
> + perf_thread_map__pid(ftrace->evlist->core.threads, i));
> if (append_tracing_file("set_ftrace_pid", buf) < 0)
> return -1;
> }
> --
> 2.30.2
>

--

- Arnaldo