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[PATCH v2] perf ftrace: Detect whether ftrace is enabled on system

Changbin Du posted 1 patch 2 months, 2 weeks ago 
tools/perf/builtin-ftrace.c | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
[PATCH v2] perf ftrace: Detect whether ftrace is enabled on system
Posted by Changbin Du 2 months, 2 weeks ago 
To make error messages more accurate, this change detects whether ftrace is
enabled on system by checking trace file "set_ftrace_pid".

Before:
~ # perf ftrace
failed to reset ftrace

After:
~ # perf ftrace
ftrace is not supported on this system

Signed-off-by: Changbin Du <changbin.du@huawei.com>

v2: rebase on perf-tools-next.
---
 tools/perf/builtin-ftrace.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
index 88a87bf387d2..abcdc49b7a98 100644
--- a/tools/perf/builtin-ftrace.c
+++ b/tools/perf/builtin-ftrace.c
@@ -80,6 +80,24 @@ static bool check_ftrace_capable(void)
 	return false;
 }
 
+static bool is_ftrace_supported(void)
+{
+	char *file;
+	bool supported = false;
+
+	file = get_tracing_file("set_ftrace_pid");
+	if (!file) {
+		pr_debug("cannot get tracing file set_ftrace_pid\n");
+		return false;
+	}
+
+	if (!access(file, F_OK))
+		supported = true;
+
+	put_tracing_file(file);
+	return supported;
+}
+
 static int __write_tracing_file(const char *name, const char *val, bool append)
 {
 	char *file;
@@ -1583,6 +1601,11 @@ int cmd_ftrace(int argc, const char **argv)
 	if (!check_ftrace_capable())
 		return -1;
 
+	if (!is_ftrace_supported()) {
+		pr_err("ftrace is not supported on this system\n");
+		return -ENOTSUP;
+	}
+
 	ret = perf_config(perf_ftrace_config, &ftrace);
 	if (ret < 0)
 		return -1;
-- 
2.34.1
Re: [PATCH v2] perf ftrace: Detect whether ftrace is enabled on system
Posted by James Clark 2 months, 2 weeks ago 

On 11/09/2024 11:01, Changbin Du wrote:
> To make error messages more accurate, this change detects whether ftrace is
> enabled on system by checking trace file "set_ftrace_pid".
> 
> Before:
> ~ # perf ftrace
> failed to reset ftrace
> 
> After:
> ~ # perf ftrace
> ftrace is not supported on this system
> 
> Signed-off-by: Changbin Du <changbin.du@huawei.com>
> 
> v2: rebase on perf-tools-next.
> ---
>   tools/perf/builtin-ftrace.c | 23 +++++++++++++++++++++++
>   1 file changed, 23 insertions(+)
> 
> diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
> index 88a87bf387d2..abcdc49b7a98 100644
> --- a/tools/perf/builtin-ftrace.c
> +++ b/tools/perf/builtin-ftrace.c
> @@ -80,6 +80,24 @@ static bool check_ftrace_capable(void)
>   	return false;
>   }
>   
> +static bool is_ftrace_supported(void)
> +{
> +	char *file;
> +	bool supported = false;
> +
> +	file = get_tracing_file("set_ftrace_pid");
> +	if (!file) {
> +		pr_debug("cannot get tracing file set_ftrace_pid\n");
> +		return false;
> +	}
> +
> +	if (!access(file, F_OK))
> +		supported = true;
> +
> +	put_tracing_file(file);
> +	return supported;
> +}
> +
>   static int __write_tracing_file(const char *name, const char *val, bool append)
>   {
>   	char *file;
> @@ -1583,6 +1601,11 @@ int cmd_ftrace(int argc, const char **argv)
>   	if (!check_ftrace_capable())
>   		return -1;
>   
> +	if (!is_ftrace_supported()) {
> +		pr_err("ftrace is not supported on this system\n");
> +		return -ENOTSUP;
> +	}
> +
>   	ret = perf_config(perf_ftrace_config, &ftrace);
>   	if (ret < 0)
>   		return -1;

Reviewed-by: James Clark <james.clark@linaro.org>
Re: [PATCH v2] perf ftrace: Detect whether ftrace is enabled on system
Posted by Arnaldo Carvalho de Melo 2 months, 2 weeks ago 
On Wed, Sep 11, 2024 at 11:15:19AM +0100, James Clark wrote:
> On 11/09/2024 11:01, Changbin Du wrote:
> > To make error messages more accurate, this change detects whether ftrace is
> > enabled on system by checking trace file "set_ftrace_pid".

<SNIP>

> > @@ -1583,6 +1601,11 @@ int cmd_ftrace(int argc, const char **argv)
> >   	if (!check_ftrace_capable())
> >   		return -1;
> > +	if (!is_ftrace_supported()) {
> > +		pr_err("ftrace is not supported on this system\n");
> > +		return -ENOTSUP;
> > +	}
> > +
> >   	ret = perf_config(perf_ftrace_config, &ftrace);
> >   	if (ret < 0)
> >   		return -1;
> 
> Reviewed-by: James Clark <james.clark@linaro.org>

Applied and added these comments:

Committer testing:

Doing it in an unprivileged toolbox container on Fedora 40:

Before:

  acme@number:~/git/perf-tools-next$ toolbox enter perf
  ⬢[acme@toolbox perf-tools-next]$ sudo su -
  ⬢[root@toolbox ~]# ~acme/bin/perf ftrace
  failed to reset ftrace
  ⬢[root@toolbox ~]#

After this patch:

  ⬢[root@toolbox ~]# ~acme/bin/perf ftrace
  ftrace is not supported on this system
  ⬢[root@toolbox ~]#

Maybe we could check if we are in such as situation, inside an
unprivileged container, and provide a HINT line?

Reviewed-by: James Clark <james.clark@linaro.org>
Signed-off-by: Changbin Du <changbin.du@huawei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Re: [PATCH v2] perf ftrace: Detect whether ftrace is enabled on system
Posted by duchangbin 2 months, 2 weeks ago 
On Wed, Sep 11, 2024 at 09:31:02AM -0300, Arnaldo Carvalho de Melo wrote:
> On Wed, Sep 11, 2024 at 11:15:19AM +0100, James Clark wrote:
> > On 11/09/2024 11:01, Changbin Du wrote:
> > > To make error messages more accurate, this change detects whether ftrace is
> > > enabled on system by checking trace file "set_ftrace_pid".
> 
> <SNIP>
> 
> > > @@ -1583,6 +1601,11 @@ int cmd_ftrace(int argc, const char **argv)
> > >   	if (!check_ftrace_capable())
> > >   		return -1;
> > > +	if (!is_ftrace_supported()) {
> > > +		pr_err("ftrace is not supported on this system\n");
> > > +		return -ENOTSUP;
> > > +	}
> > > +
> > >   	ret = perf_config(perf_ftrace_config, &ftrace);
> > >   	if (ret < 0)
> > >   		return -1;
> > 
> > Reviewed-by: James Clark <james.clark@linaro.org>
> 
> Applied and added these comments:
> 
> Committer testing:
> 
> Doing it in an unprivileged toolbox container on Fedora 40:
> 
> Before:
> 
>   acme@number:~/git/perf-tools-next$ toolbox enter perf
>   ⬢[acme@toolbox perf-tools-next]$ sudo su -
>   ⬢[root@toolbox ~]# ~acme/bin/perf ftrace
>   failed to reset ftrace
>   ⬢[root@toolbox ~]#
> 
> After this patch:
> 
>   ⬢[root@toolbox ~]# ~acme/bin/perf ftrace
>   ftrace is not supported on this system
>   ⬢[root@toolbox ~]#
> 
> Maybe we could check if we are in such as situation, inside an
> unprivileged container, and provide a HINT line?
> 
I think we could check the mount status of tracefs first, and then check whether
the ftrace node exists. If there's a permission issue in container, maybe we
should also check the errno of access().

> Reviewed-by: James Clark <james.clark@linaro.org>
> Signed-off-by: Changbin Du <changbin.du@huawei.com>
> Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>

-- 
Cheers,
Changbin Du

Patchew 2.1-devel-b67e4c2

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