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[PATCH 2/2] perf probe: Fix offline module name missmatch issue

Started byRavi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
First post2016-04-26 16:30 +0200
Last post2016-04-27 17:40 +0200
Articles 3 — 3 participants

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  [PATCH 2/2] perf probe: Fix offline module name missmatch issue Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com> - 2016-04-26 16:30 +0200
    Re: [PATCH 2/2] perf probe: Fix offline module name missmatch issue Masami Hiramatsu <mhiramat@kernel.org> - 2016-04-26 16:50 +0200
    [tip:perf/core] perf probe: Fix offline module name missmatch issue tip-bot for Ravi Bangoria <tipbot@zytor.com> - 2016-04-27 17:40 +0200

#1387529 — [PATCH 2/2] perf probe: Fix offline module name missmatch issue

FromRavi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Date2016-04-26 16:30 +0200
Subject[PATCH 2/2] perf probe: Fix offline module name missmatch issue
Message-ID<rsc9X-OI-7@gated-at.bofh.it>
Perf can add a probe on kernel module which has not been loaded yet.
Current implementation finds module name from path. But if filename
is different from actual module name then perf fails to register
probe while loading module because of mismatch in names. For example,
samples/kobject/kobject-example.ko is loaded as kobject_example.

Before applying patch:

  $ sudo ./perf probe -m /linux/samples/kobject/kobject-example.ko foo_show
    Added new event:
      probe:foo_show       (on foo_show in kobject-example)

    You can now use it in all perf tools, such as:

    perf record -e probe:foo_show -aR sleep 1

  $ cat /sys/kernel/debug/tracing/kprobe_events
    p:probe/foo_show kobject-example:foo_show

  $ insmod kobject-example.ko

  $ lsmod
    Module                  Size  Used by
    kobject_example        16384  0

  Generate read to /sys/kernel/kobject_example/foo while recording data
  with below command
  $ sudo ./perf record -e probe:foo_show -a
    [ perf record: Woken up 1 times to write data ]
    [ perf record: Captured and wrote 0.093 MB perf.data ]

  $./perf report --stdio -F overhead,comm,dso,sym
    Error:
    The perf.data.old file has no samples!

After applying patch:

  $ sudo ./perf probe -m /linux/samples/kobject/kobject-example.ko foo_show
    Added new event:
      probe:foo_show       (on foo_show in kobject_example)

    You can now use it in all perf tools, such as:

    perf record -e probe:foo_show -aR sleep 1

  $ sudo cat /sys/kernel/debug/tracing/kprobe_events
    p:probe/foo_show kobject_example:foo_show

  $ insmod kobject-example.ko

  $ lsmod
    Module                  Size  Used by
    kobject_example        16384  0

  Generate read to /sys/kernel/kobject_example/foo while recording data
  with below command
  $ sudo ./perf record -e probe:foo_show -a
    [ perf record: Woken up 1 times to write data ]
    [ perf record: Captured and wrote 0.097 MB perf.data (8 samples) ]

  $ sudo ./perf report  --stdio -F overhead,comm,dso,sym
    ...
    # Samples: 8  of event 'probe:foo_show'
    # Event count (approx.): 8
    #
    # Overhead  Command  Shared Object      Symbol
    # ........  .......  .................  ............
    #
       100.00%  cat      [kobject_example]  [k] foo_show

Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
---
 tools/perf/util/probe-event.c | 19 +++++--------------
 1 file changed, 5 insertions(+), 14 deletions(-)

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index d58de20..26803e1 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -642,32 +642,23 @@ static int add_module_to_probe_trace_events(struct probe_trace_event *tevs,
 					    int ntevs, const char *module)
 {
 	int i, ret = 0;
-	char *tmp;
+	char *mod_name = NULL;
 
 	if (!module)
 		return 0;
 
-	tmp = strrchr(module, '/');
-	if (tmp) {
-		/* This is a module path -- get the module name */
-		module = strdup(tmp + 1);
-		if (!module)
-			return -ENOMEM;
-		tmp = strchr(module, '.');
-		if (tmp)
-			*tmp = '\0';
-		tmp = (char *)module;	/* For free() */
-	}
+	mod_name = find_module_name(module);
 
 	for (i = 0; i < ntevs; i++) {
-		tevs[i].point.module = strdup(module);
+		tevs[i].point.module =
+			strdup(mod_name ? mod_name : module);
 		if (!tevs[i].point.module) {
 			ret = -ENOMEM;
 			break;
 		}
 	}
 
-	free(tmp);
+	free(mod_name);
 	return ret;
 }
 
-- 
1.9.1

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#1387560

FromMasami Hiramatsu <mhiramat@kernel.org>
Date2016-04-26 16:50 +0200
Message-ID<rsctk-Xx-29@gated-at.bofh.it>
In reply to#1387529
On Tue, 26 Apr 2016 19:55:41 +0530
Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com> wrote:

> Perf can add a probe on kernel module which has not been loaded yet.
> Current implementation finds module name from path. But if filename
> is different from actual module name then perf fails to register
> probe while loading module because of mismatch in names. For example,
> samples/kobject/kobject-example.ko is loaded as kobject_example.
> 
> Before applying patch:
> 
>   $ sudo ./perf probe -m /linux/samples/kobject/kobject-example.ko foo_show
>     Added new event:
>       probe:foo_show       (on foo_show in kobject-example)
> 
>     You can now use it in all perf tools, such as:
> 
>     perf record -e probe:foo_show -aR sleep 1
> 
>   $ cat /sys/kernel/debug/tracing/kprobe_events
>     p:probe/foo_show kobject-example:foo_show
> 
>   $ insmod kobject-example.ko
> 
>   $ lsmod
>     Module                  Size  Used by
>     kobject_example        16384  0
> 
>   Generate read to /sys/kernel/kobject_example/foo while recording data
>   with below command
>   $ sudo ./perf record -e probe:foo_show -a
>     [ perf record: Woken up 1 times to write data ]
>     [ perf record: Captured and wrote 0.093 MB perf.data ]
> 
>   $./perf report --stdio -F overhead,comm,dso,sym
>     Error:
>     The perf.data.old file has no samples!
> 
> After applying patch:
> 
>   $ sudo ./perf probe -m /linux/samples/kobject/kobject-example.ko foo_show
>     Added new event:
>       probe:foo_show       (on foo_show in kobject_example)
> 
>     You can now use it in all perf tools, such as:
> 
>     perf record -e probe:foo_show -aR sleep 1
> 
>   $ sudo cat /sys/kernel/debug/tracing/kprobe_events
>     p:probe/foo_show kobject_example:foo_show
> 
>   $ insmod kobject-example.ko
> 
>   $ lsmod
>     Module                  Size  Used by
>     kobject_example        16384  0
> 
>   Generate read to /sys/kernel/kobject_example/foo while recording data
>   with below command
>   $ sudo ./perf record -e probe:foo_show -a
>     [ perf record: Woken up 1 times to write data ]
>     [ perf record: Captured and wrote 0.097 MB perf.data (8 samples) ]
> 
>   $ sudo ./perf report  --stdio -F overhead,comm,dso,sym
>     ...
>     # Samples: 8  of event 'probe:foo_show'
>     # Event count (approx.): 8
>     #
>     # Overhead  Command  Shared Object      Symbol
>     # ........  .......  .................  ............
>     #
>        100.00%  cat      [kobject_example]  [k] foo_show
> 

Looks good to me :)

Acked-by: Masami Hiramatsu <mhiramat@kernel.org>

Thank you!

> Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
> ---
>  tools/perf/util/probe-event.c | 19 +++++--------------
>  1 file changed, 5 insertions(+), 14 deletions(-)
> 
> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> index d58de20..26803e1 100644
> --- a/tools/perf/util/probe-event.c
> +++ b/tools/perf/util/probe-event.c
> @@ -642,32 +642,23 @@ static int add_module_to_probe_trace_events(struct probe_trace_event *tevs,
>  					    int ntevs, const char *module)
>  {
>  	int i, ret = 0;
> -	char *tmp;
> +	char *mod_name = NULL;
>  
>  	if (!module)
>  		return 0;
>  
> -	tmp = strrchr(module, '/');
> -	if (tmp) {
> -		/* This is a module path -- get the module name */
> -		module = strdup(tmp + 1);
> -		if (!module)
> -			return -ENOMEM;
> -		tmp = strchr(module, '.');
> -		if (tmp)
> -			*tmp = '\0';
> -		tmp = (char *)module;	/* For free() */
> -	}
> +	mod_name = find_module_name(module);
>  
>  	for (i = 0; i < ntevs; i++) {
> -		tevs[i].point.module = strdup(module);
> +		tevs[i].point.module =
> +			strdup(mod_name ? mod_name : module);
>  		if (!tevs[i].point.module) {
>  			ret = -ENOMEM;
>  			break;
>  		}
>  	}
>  
> -	free(tmp);
> +	free(mod_name);
>  	return ret;
>  }
>  
> -- 
> 1.9.1
> 


-- 
Masami Hiramatsu <mhiramat@kernel.org>

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#1389239 — [tip:perf/core] perf probe: Fix offline module name missmatch issue

Fromtip-bot for Ravi Bangoria <tipbot@zytor.com>
Date2016-04-27 17:40 +0200
Subject[tip:perf/core] perf probe: Fix offline module name missmatch issue
Message-ID<rszJg-3tA-21@gated-at.bofh.it>
In reply to#1387529
Commit-ID:  63a29613d7c69f17b6a3266bfc338986698b2546
Gitweb:     http://git.kernel.org/tip/63a29613d7c69f17b6a3266bfc338986698b2546
Author:     Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
AuthorDate: Tue, 26 Apr 2016 19:55:41 +0530
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Tue, 26 Apr 2016 13:15:01 -0300

perf probe: Fix offline module name missmatch issue

Perf can add a probe on kernel module which has not been loaded yet.

The current implementation finds the module name from path. But if the
filename is different from the actual module name then perf fails to
register a probe while loading module because of mismatch in the names.

For example, samples/kobject/kobject-example.ko is loaded as
kobject_example.

Before applying patch:

  $ sudo ./perf probe -m /linux/samples/kobject/kobject-example.ko foo_show
    Added new event:
      probe:foo_show       (on foo_show in kobject-example)

    You can now use it in all perf tools, such as:

    perf record -e probe:foo_show -aR sleep 1

  $ cat /sys/kernel/debug/tracing/kprobe_events
    p:probe/foo_show kobject-example:foo_show

  $ insmod kobject-example.ko

  $ lsmod
    Module                  Size  Used by
    kobject_example        16384  0

  Generate read to /sys/kernel/kobject_example/foo while recording data
  with below command
  $ sudo ./perf record -e probe:foo_show -a
    [ perf record: Woken up 1 times to write data ]
    [ perf record: Captured and wrote 0.093 MB perf.data ]

  $./perf report --stdio -F overhead,comm,dso,sym
    Error:
    The perf.data.old file has no samples!

After applying patch:

  $ sudo ./perf probe -m /linux/samples/kobject/kobject-example.ko foo_show
    Added new event:
      probe:foo_show       (on foo_show in kobject_example)

    You can now use it in all perf tools, such as:

    perf record -e probe:foo_show -aR sleep 1

  $ sudo cat /sys/kernel/debug/tracing/kprobe_events
    p:probe/foo_show kobject_example:foo_show

  $ insmod kobject-example.ko

  $ lsmod
    Module                  Size  Used by
    kobject_example        16384  0

  Generate read to /sys/kernel/kobject_example/foo while recording data
  with below command
  $ sudo ./perf record -e probe:foo_show -a
    [ perf record: Woken up 1 times to write data ]
    [ perf record: Captured and wrote 0.097 MB perf.data (8 samples) ]

  $ sudo ./perf report  --stdio -F overhead,comm,dso,sym
    ...
    # Samples: 8  of event 'probe:foo_show'
    # Event count (approx.): 8
    #
    # Overhead  Command  Shared Object      Symbol
    # ........  .......  .................  ............
    #
       100.00%  cat      [kobject_example]  [k] foo_show

Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1461680741-12517-2-git-send-email-ravi.bangoria@linux.vnet.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/probe-event.c | 19 +++++--------------
 1 file changed, 5 insertions(+), 14 deletions(-)

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 0de5d10..bc2eb7c 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -588,32 +588,23 @@ static int add_module_to_probe_trace_events(struct probe_trace_event *tevs,
 					    int ntevs, const char *module)
 {
 	int i, ret = 0;
-	char *tmp;
+	char *mod_name = NULL;
 
 	if (!module)
 		return 0;
 
-	tmp = strrchr(module, '/');
-	if (tmp) {
-		/* This is a module path -- get the module name */
-		module = strdup(tmp + 1);
-		if (!module)
-			return -ENOMEM;
-		tmp = strchr(module, '.');
-		if (tmp)
-			*tmp = '\0';
-		tmp = (char *)module;	/* For free() */
-	}
+	mod_name = find_module_name(module);
 
 	for (i = 0; i < ntevs; i++) {
-		tevs[i].point.module = strdup(module);
+		tevs[i].point.module =
+			strdup(mod_name ? mod_name : module);
 		if (!tevs[i].point.module) {
 			ret = -ENOMEM;
 			break;
 		}
 	}
 
-	free(tmp);
+	free(mod_name);
 	return ret;
 }

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