[PATCH] perf probe: Fix bug in perf probe with global variables

[PATCH] perf probe: Fix bug in perf probe with global variables

[He Kuang]

There are missing curly braces which causes find_variable() return wrong
value when probing with global variables.

This problem can be reproduced as following:

  $ perf probe -v --add='generic_perform_write global_variable_for_test'
  ...
  Try to find probe point from debuginfo.
  Probe point found: generic_perform_write+0
  Searching 'global_variable_for_test' variable in context.
  An error occurred in debuginfo analysis (-2).
    Error: Failed to add events. Reason: No such file or directory (Code: -2)

After this patch:

  $ perf probe -v --add='generic_perform_write global_variable_for_test'
  ...
  Converting variable global_variable_for_test into trace event.
  global_variable_for_test type is int.
  Found 1 probe_trace_events.
  Opening /sys/kernel/debug/tracing/kprobe_events write=1
  Added new event:
  Writing event: p:probe/generic_perform_write _stext+1237464
  global_variable_for_test=@global_variable_for_test+0:s32
    probe:generic_perform_write (on generic_perform_write with
    global_variable_for_test)

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

      perf record -e probe:generic_perform_write -aR sleep 1

Signed-off-by: He Kuang <hekuang@huawei.com>
---
 tools/perf/util/probe-finder.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 44554c3..1c3cc07 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -578,10 +578,12 @@ static int find_variable(Dwarf_Die *sc_die, struct probe_finder *pf)
 	/* Search child die for local variables and parameters. */
 	if (!die_find_variable_at(sc_die, pf->pvar->var, pf->addr, &vr_die)) {
 		/* Search again in global variables */
-		if (!die_find_variable_at(&pf->cu_die, pf->pvar->var, 0, &vr_die))
+		if (!die_find_variable_at(&pf->cu_die, pf->pvar->var,
+						0, &vr_die)) {
 			pr_warning("Failed to find '%s' in this function.\n",
 				   pf->pvar->var);
 			ret = -ENOENT;
+		}
 	}
 	if (ret >= 0)
 		ret = convert_variable(&vr_die, pf);
-- 
1.8.5.2

Re: [PATCH] perf probe: Fix bug in perf probe with global variables

[Masami Hiramatsu]

(2015/04/25 17:08), He Kuang wrote:
> There are missing curly braces which causes find_variable() return wrong
> value when probing with global variables.
> 
> This problem can be reproduced as following:
> 
>   $ perf probe -v --add='generic_perform_write global_variable_for_test'
>   ...
>   Try to find probe point from debuginfo.
>   Probe point found: generic_perform_write+0
>   Searching 'global_variable_for_test' variable in context.
>   An error occurred in debuginfo analysis (-2).
>     Error: Failed to add events. Reason: No such file or directory (Code: -2)
> 
> After this patch:
> 
>   $ perf probe -v --add='generic_perform_write global_variable_for_test'
>   ...
>   Converting variable global_variable_for_test into trace event.
>   global_variable_for_test type is int.
>   Found 1 probe_trace_events.
>   Opening /sys/kernel/debug/tracing/kprobe_events write=1
>   Added new event:
>   Writing event: p:probe/generic_perform_write _stext+1237464
>   global_variable_for_test=@global_variable_for_test+0:s32
>     probe:generic_perform_write (on generic_perform_write with
>     global_variable_for_test)
> 
>   You can now use it in all perf tools, such as:
> 
>       perf record -e probe:generic_perform_write -aR sleep 1

Oops, that's my fault! :(

Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>

Thank you!!

> 
> Signed-off-by: He Kuang <hekuang@huawei.com>
> ---
>  tools/perf/util/probe-finder.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
> index 44554c3..1c3cc07 100644
> --- a/tools/perf/util/probe-finder.c
> +++ b/tools/perf/util/probe-finder.c
> @@ -578,10 +578,12 @@ static int find_variable(Dwarf_Die *sc_die, struct probe_finder *pf)
>  	/* Search child die for local variables and parameters. */
>  	if (!die_find_variable_at(sc_die, pf->pvar->var, pf->addr, &vr_die)) {
>  		/* Search again in global variables */
> -		if (!die_find_variable_at(&pf->cu_die, pf->pvar->var, 0, &vr_die))
> +		if (!die_find_variable_at(&pf->cu_die, pf->pvar->var,
> +						0, &vr_die)) {
>  			pr_warning("Failed to find '%s' in this function.\n",
>  				   pf->pvar->var);
>  			ret = -ENOENT;
> +		}
>  	}
>  	if (ret >= 0)
>  		ret = convert_variable(&vr_die, pf);
> 


-- 
Masami HIRAMATSU
Linux Technology Research Center, System Productivity Research Dept.
Center for Technology Innovation - Systems Engineering
Hitachi, Ltd., Research & Development Group
E-mail: masami.hiramatsu.pt@hitachi.com

Re: [PATCH] perf probe: Fix bug in perf probe with global variables

[Arnaldo Carvalho de Melo]

Em Sun, Apr 26, 2015 at 09:56:06AM +0900, Masami Hiramatsu escreveu:
> (2015/04/25 17:08), He Kuang wrote:
> > There are missing curly braces which causes find_variable() return wrong
> > value when probing with global variables.
> > 
> > This problem can be reproduced as following:
> > 
> >   $ perf probe -v --add='generic_perform_write global_variable_for_test'
> >   ...
> >   Try to find probe point from debuginfo.
> >   Probe point found: generic_perform_write+0
> >   Searching 'global_variable_for_test' variable in context.
> >   An error occurred in debuginfo analysis (-2).
> >     Error: Failed to add events. Reason: No such file or directory (Code: -2)
> > 
> > After this patch:
> > 
> >   $ perf probe -v --add='generic_perform_write global_variable_for_test'
> >   ...
> >   Converting variable global_variable_for_test into trace event.
> >   global_variable_for_test type is int.
> >   Found 1 probe_trace_events.
> >   Opening /sys/kernel/debug/tracing/kprobe_events write=1
> >   Added new event:
> >   Writing event: p:probe/generic_perform_write _stext+1237464
> >   global_variable_for_test=@global_variable_for_test+0:s32
> >     probe:generic_perform_write (on generic_perform_write with
> >     global_variable_for_test)
> > 
> >   You can now use it in all perf tools, such as:
> > 
> >       perf record -e probe:generic_perform_write -aR sleep 1
> 
> Oops, that's my fault! :(
> 
> Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
> 
> Thank you!!

Thanks, applied to perf/urgent.

- Arnaldo

[tip:perf/urgent] perf probe: Fix bug with global variables handling

[tip-bot for He Kuang]

Commit-ID:  d13855ef18e1852b2c4dc86ddf5759c5b34628cb
Gitweb:     http://git.kernel.org/tip/d13855ef18e1852b2c4dc86ddf5759c5b34628cb
Author:     He Kuang <hekuang@huawei.com>
AuthorDate: Sat, 25 Apr 2015 16:08:58 +0800
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Mon, 27 Apr 2015 13:57:29 -0300

perf probe: Fix bug with global variables handling

There are missing curly braces which causes find_variable() return wrong
value when probing with global variables.

This problem can be reproduced as following:

  $ perf probe -v --add='generic_perform_write global_variable_for_test'
  ...
  Try to find probe point from debuginfo.
  Probe point found: generic_perform_write+0
  Searching 'global_variable_for_test' variable in context.
  An error occurred in debuginfo analysis (-2).
    Error: Failed to add events. Reason: No such file or directory (Code: -2)

After this patch:

  $ perf probe -v --add='generic_perform_write global_variable_for_test'
  ...
  Converting variable global_variable_for_test into trace event.
  global_variable_for_test type is int.
  Found 1 probe_trace_events.
  Opening /sys/kernel/debug/tracing/kprobe_events write=1
  Added new event:
  Writing event: p:probe/generic_perform_write _stext+1237464
  global_variable_for_test=@global_variable_for_test+0:s32
    probe:generic_perform_write (on generic_perform_write with
    global_variable_for_test)

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

      perf record -e probe:generic_perform_write -aR sleep 1

Signed-off-by: He Kuang <hekuang@huawei.com>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1429949338-18678-1-git-send-email-hekuang@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/probe-finder.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 44554c3..1c3cc07 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -578,10 +578,12 @@ static int find_variable(Dwarf_Die *sc_die, struct probe_finder *pf)
 	/* Search child die for local variables and parameters. */
 	if (!die_find_variable_at(sc_die, pf->pvar->var, pf->addr, &vr_die)) {
 		/* Search again in global variables */
-		if (!die_find_variable_at(&pf->cu_die, pf->pvar->var, 0, &vr_die))
+		if (!die_find_variable_at(&pf->cu_die, pf->pvar->var,
+						0, &vr_die)) {
 			pr_warning("Failed to find '%s' in this function.\n",
 				   pf->pvar->var);
 			ret = -ENOENT;
+		}
 	}
 	if (ret >= 0)
 		ret = convert_variable(&vr_die, pf);