Trying to use 'perf probe' to debug perf itself

PATCH In review Arnaldo Carvalho de Melo 3 participants 9 messages Feb 24, 2015 – Mar 3, 2015 perf events

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Arnaldo Carvalho de Melo

author maintainer

2015-02-24 18:49 UTC #0 lore raw

Hi Masami,

I'm adding thread refcounting in perf, and in this process I am
investigating a problem, so thought about using perf itself to match thread__get with thread__put:

[root@ssdandy ~]# perf probe -x ~/bin/perf -V thread__put Available variables at thread__put
@<thread__put+0>
struct thread* thread
[root@ssdandy ~]# perf probe -x ~/bin/perf -V thread__get Available variables at thread__get
@<thread__get+0>
struct thread* thread
[root@ssdandy ~]#

cool, so I thought it would be just a matter of asking to put the probes and get the value of 'thread', then match things, but:

[root@ssdandy ~]# perf probe -v ~/bin/perf thread__put thread probe-definition(0): thread__put thread
symbol:thread__put file:(null) line:0 offset:0 return:0 lazy:(null) parsing arg: thread into thread
1 arguments
Open Debuginfo file: /root/bin/perf
Try to find probe point from debuginfo.
Probe point found: thread__put+0
Searching 'thread' variable in context.
Converting variable thread into trace event.
thread type is (null).
Found 1 probe_trace_events.
Opening /sys/kernel/debug/tracing/uprobe_events write=1
Added new event:
Writing event: p:probe_perf/thread__put /root/bin/perf:0xd03d2 thread=-32(%sp):u64 Failed to write event: Invalid argument
Error: Failed to add events. Reason: Invalid argument (Code: -22)
[root@ssdandy ~]#

Not possible :-\

please let me know if you need some file, here is the readelf -wi for those two routines:

# readelf -wi ~/bin/perf
<SNIP>
 <1><e25f1>: Abbrev Number: 35 (DW_TAG_subprogram)
    <e25f2>   DW_AT_external    : 1     
    <e25f2>   DW_AT_name        : (indirect string, offset: 0x4c5c3): thread__get       
    <e25f6>   DW_AT_decl_file   : 6     
    <e25f7>   DW_AT_decl_line   : 84    
    <e25f8>   DW_AT_prototyped  : 1     
    <e25f8>   DW_AT_type        : <0xe15cc>     
    <e25fc>   DW_AT_low_pc      : 0x4d038c      
    <e2604>   DW_AT_high_pc     : 0x46  
    <e260c>   DW_AT_frame_base  : 1 byte block: 9c      (DW_OP_call_frame_cfa)
    <e260e>   DW_AT_GNU_all_tail_call_sites: 1  
    <e260e>   DW_AT_sibling     : <0xe2621>     
 <2><e2612>: Abbrev Number: 32 (DW_TAG_formal_parameter)
    <e2613>   DW_AT_name        : (indirect string, offset: 0x43dc7): thread    
    <e2617>   DW_AT_decl_file   : 6     
    <e2618>   DW_AT_decl_line   : 84    
    <e2619>   DW_AT_type        : <0xe15cc>     
    <e261d>   DW_AT_location    : 2 byte block: 91 58   (DW_OP_fbreg: -40)
 <2><e2620>: Abbrev Number: 0
 <1><e2621>: Abbrev Number: 39 (DW_TAG_subprogram)
    <e2622>   DW_AT_external    : 1     
    <e2622>   DW_AT_name        : (indirect string, offset: 0x4c699): thread__put       
    <e2626>   DW_AT_decl_file   : 6     
    <e2627>   DW_AT_decl_line   : 90    
    <e2628>   DW_AT_prototyped  : 1     
    <e2628>   DW_AT_low_pc      : 0x4d03d2      
    <e2630>   DW_AT_high_pc     : 0x6c  
    <e2638>   DW_AT_frame_base  : 1 byte block: 9c      (DW_OP_call_frame_cfa)
    <e263a>   DW_AT_GNU_all_tail_call_sites: 1  
    <e263a>   DW_AT_sibling     : <0xe264d>     
 <2><e263e>: Abbrev Number: 32 (DW_TAG_formal_parameter)
    <e263f>   DW_AT_name        : (indirect string, offset: 0x43dc7): thread    
    <e2643>   DW_AT_decl_file   : 6     
    <e2644>   DW_AT_decl_line   : 90    
    <e2645>   DW_AT_type        : <0xe15cc>     
<SNIP>

Will see what I can do with just:

[root@ssdandy ~]# perf probe ~/bin/perf thread__get Added new event:
probe_perf:thread__get (on thread__get in /root/bin/perf)

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

perf record -e probe_perf:thread__get -aR sleep 1

[root@ssdandy ~]# perf probe ~/bin/perf thread__put Added new event:
probe_perf:thread__put (on thread__put in /root/bin/perf)

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

perf record -e probe_perf:thread__put -aR sleep 1

[root@ssdandy ~]# perf list probe*:*

List of pre-defined events (to be used in -e):

probe_perf:thread__put [Tracepoint event]
probe_perf:thread__get [Tracepoint event]
[root@ssdandy ~]# perf probe -l
probe_perf:thread__get (on thread__get@util/thread.c in /root/bin/perf) probe_perf:thread__put (on thread__put@util/thread.c in /root/bin/perf)
[root@ssdandy ~]#

- Arnaldo

Masami Hiramatsu

2015-02-25 02:53 UTC #1 lore raw

Hi Arnaldo,

Quoted 39 lines · Arnaldo Carvalho de Melo

Hi Masami,
I'm adding thread refcounting in perf, and in this process I am
investigating a problem, so thought about using perf itself to match thread__get with thread__put:
[root@ssdandy ~]# perf probe -x ~/bin/perf -V thread__put Available variables at thread__put
@<thread__put+0>
struct thread* thread
[root@ssdandy ~]# perf probe -x ~/bin/perf -V thread__get Available variables at thread__get
@<thread__get+0>
struct thread* thread
[root@ssdandy ~]#
cool, so I thought it would be just a matter of asking to put the probes and get the value of 'thread', then match things, but:
[root@ssdandy ~]# perf probe -v ~/bin/perf thread__put thread probe-definition(0): thread__put thread
symbol:thread__put file:(null) line:0 offset:0 return:0 lazy:(null) parsing arg: thread into thread
1 arguments
Open Debuginfo file: /root/bin/perf
Try to find probe point from debuginfo.
Probe point found: thread__put+0
Searching 'thread' variable in context.
Converting variable thread into trace event.
thread type is (null).
Found 1 probe_trace_events.
Opening /sys/kernel/debug/tracing/uprobe_events write=1
Added new event:
Writing event: p:probe_perf/thread__put /root/bin/perf:0xd03d2 thread=-32(%sp):u64 Failed to write event: Invalid argument
Error: Failed to add events. Reason: Invalid argument (Code: -22)
[root@ssdandy ~]#

Quoted 1 line

Not possible :-\

Hmm, strange. Could you tell me the version of your kernel? It seems that the kernel newer than 3.14 supports uprobes with memory dereference (e.g. -32(%sp) )feature.
(it was actually introduced by 5baaa59e, and git-describe told
it was v3.13-rc4-22-g5baaa59)

And also, could you try to write the result command to uprobe_event as below?

# echo "p:probe_perf/thread__put /root/bin/perf:0xd03d2 thread=-32(%sp):u64" >> \
 /sys/kernel/debug/tracing/uprobe_events

Quoted 3 lines

please let me know if you need some file, here is the readelf -wi for those two routines:

This should not be the problem of dwarf-analysis. It seems kernel-side (uprobe) problem.

Thank you,

Quoted 76 lines

# readelf -wi ~/bin/perf
<SNIP>
 <1><e25f1>: Abbrev Number: 35 (DW_TAG_subprogram)
    <e25f2>   DW_AT_external    : 1     
    <e25f2>   DW_AT_name        : (indirect string, offset: 0x4c5c3): thread__get       
    <e25f6>   DW_AT_decl_file   : 6     
    <e25f7>   DW_AT_decl_line   : 84    
    <e25f8>   DW_AT_prototyped  : 1     
    <e25f8>   DW_AT_type        : <0xe15cc>     
    <e25fc>   DW_AT_low_pc      : 0x4d038c      
    <e2604>   DW_AT_high_pc     : 0x46  
    <e260c>   DW_AT_frame_base  : 1 byte block: 9c      (DW_OP_call_frame_cfa)
    <e260e>   DW_AT_GNU_all_tail_call_sites: 1  
    <e260e>   DW_AT_sibling     : <0xe2621>     
 <2><e2612>: Abbrev Number: 32 (DW_TAG_formal_parameter)
    <e2613>   DW_AT_name        : (indirect string, offset: 0x43dc7): thread    
    <e2617>   DW_AT_decl_file   : 6     
    <e2618>   DW_AT_decl_line   : 84    
    <e2619>   DW_AT_type        : <0xe15cc>     
    <e261d>   DW_AT_location    : 2 byte block: 91 58   (DW_OP_fbreg: -40)
 <2><e2620>: Abbrev Number: 0
 <1><e2621>: Abbrev Number: 39 (DW_TAG_subprogram)
    <e2622>   DW_AT_external    : 1     
    <e2622>   DW_AT_name        : (indirect string, offset: 0x4c699): thread__put       
    <e2626>   DW_AT_decl_file   : 6     
    <e2627>   DW_AT_decl_line   : 90    
    <e2628>   DW_AT_prototyped  : 1     
    <e2628>   DW_AT_low_pc      : 0x4d03d2      
    <e2630>   DW_AT_high_pc     : 0x6c  
    <e2638>   DW_AT_frame_base  : 1 byte block: 9c      (DW_OP_call_frame_cfa)
    <e263a>   DW_AT_GNU_all_tail_call_sites: 1  
    <e263a>   DW_AT_sibling     : <0xe264d>     
 <2><e263e>: Abbrev Number: 32 (DW_TAG_formal_parameter)
    <e263f>   DW_AT_name        : (indirect string, offset: 0x43dc7): thread    
    <e2643>   DW_AT_decl_file   : 6     
    <e2644>   DW_AT_decl_line   : 90    
    <e2645>   DW_AT_type        : <0xe15cc>     
<SNIP>
Will see what I can do with just:
[root@ssdandy ~]# perf probe ~/bin/perf thread__get Added new event:
probe_perf:thread__get (on thread__get in /root/bin/perf)
You can now use it in all perf tools, such as:
perf record -e probe_perf:thread__get -aR sleep 1
[root@ssdandy ~]# perf probe ~/bin/perf thread__put Added new event:
probe_perf:thread__put (on thread__put in /root/bin/perf)
You can now use it in all perf tools, such as:
perf record -e probe_perf:thread__put -aR sleep 1
[root@ssdandy ~]# perf list probe*:*
List of pre-defined events (to be used in -e):
probe_perf:thread__put [Tracepoint event]
probe_perf:thread__get [Tracepoint event]
[root@ssdandy ~]# perf probe -l
probe_perf:thread__get (on thread__get@util/thread.c in /root/bin/perf) probe_perf:thread__put (on thread__put@util/thread.c in /root/bin/perf)
[root@ssdandy ~]#
- Arnaldo
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Signature · 4 lines

Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: [email protected]

Arnaldo Carvalho de Melo

author maintainer

2015-02-25 13:25 UTC #2 lore raw

Em Wed, Feb 25, 2015 at 11:53:16AM +0900, Masami Hiramatsu escreveu:

Quoted 10 lines

Quoted 9 lines · Arnaldo Carvalho de Melo
Available variables at thread__get
@<thread__get+0>
struct thread* thread
[root@ssdandy ~]#
cool, so I thought it would be just a matter of asking to put the probes and get the value of 'thread', then match things, but:
[root@ssdandy ~]# perf probe -v ~/bin/perf thread__put thread

<SNIP>

Quoted 8 lines

Quoted 6 lines
Writing event: p:probe_perf/thread__put /root/bin/perf:0xd03d2 thread=-32(%sp):u64 Failed to write event: Invalid argument
Error: Failed to add events. Reason: Invalid argument (Code: -22)
[root@ssdandy ~]#
Not possible :-\
Hmm, strange. Could you tell me the version of your kernel?

[root@ssdandy ~]# uname -r
3.10.0-210.el7.x86_64

Quoted 2 lines

It seems that the kernel newer than 3.14 supports uprobes with memory dereference (e.g. -32(%sp) )feature.

Right, that must be the case, will test, but then, would it be possible for the kernel, in such cases, return something line EOPNOTSUP?

I will try to figure out a better error message on the tooling side, something like:

. Realize we're asking for memory dereference in uprobes
. If it fails with EINVAL, check the kernel version and say something
like:

Please upgrade your kernel to at least x.y.z to have access to feature FOO_BAR.

- Arnaldo

Quoted 8 lines

(it was actually introduced by 5baaa59e, and git-describe told
it was v3.13-rc4-22-g5baaa59)
And also, could you try to write the result command to uprobe_event as below?
# echo "p:probe_perf/thread__put /root/bin/perf:0xd03d2 thread=-32(%sp):u64" >> \
 /sys/kernel/debug/tracing/uprobe_events

Well, I'll try that if it fails after I upgrade to 3.14.

Quoted 5 lines

Quoted 2 lines
please let me know if you need some file, here is the readelf -wi for those two routines:
This should not be the problem of dwarf-analysis. It seems kernel-side (uprobe) problem.

Thanks a lot!

- Arnaldo

Masami Hiramatsu

2015-02-26 04:57 UTC #3 lore raw

Quoted 21 lines · Arnaldo Carvalho de Melo

Em Wed, Feb 25, 2015 at 11:53:16AM +0900, Masami Hiramatsu escreveu:
Quoted 10 lines
Quoted 9 lines · Arnaldo Carvalho de Melo
Available variables at thread__get
@<thread__get+0>
struct thread* thread
[root@ssdandy ~]#
cool, so I thought it would be just a matter of asking to put the probes and get the value of 'thread', then match things, but:
[root@ssdandy ~]# perf probe -v ~/bin/perf thread__put thread
<SNIP>
Quoted 8 lines
Quoted 6 lines
Writing event: p:probe_perf/thread__put /root/bin/perf:0xd03d2 thread=-32(%sp):u64 Failed to write event: Invalid argument
Error: Failed to add events. Reason: Invalid argument (Code: -22)
[root@ssdandy ~]#
Not possible :-\
Hmm, strange. Could you tell me the version of your kernel?

Quoted 8 lines

[root@ssdandy ~]# uname -r
3.10.0-210.el7.x86_64
Quoted 2 lines
It seems that the kernel newer than 3.14 supports uprobes with memory dereference (e.g. -32(%sp) )feature.
Right, that must be the case, will test, but then, would it be possible for the kernel, in such cases, return something line EOPNOTSUP?

Yeah, but for now, it is already supported in kernel. Of cause we can try to test feature with adding temporary event from perftools too.

Quoted 9 lines

I will try to figure out a better error message on the tooling side, something like:
. Realize we're asking for memory dereference in uprobes
. If it fails with EINVAL, check the kernel version and say something
like:
Please upgrade your kernel to at least x.y.z to have access to feature FOO_BAR.

OK, it may be worth for users (I'm not sure RHEL can update their kernel to include that enhancement)

Thank you,

Quoted 24 lines

- Arnaldo
Quoted 8 lines
(it was actually introduced by 5baaa59e, and git-describe told
it was v3.13-rc4-22-g5baaa59)
And also, could you try to write the result command to uprobe_event as below?
# echo "p:probe_perf/thread__put /root/bin/perf:0xd03d2 thread=-32(%sp):u64" >> \
 /sys/kernel/debug/tracing/uprobe_events
Well, I'll try that if it fails after I upgrade to 3.14.
Quoted 5 lines
Quoted 2 lines
please let me know if you need some file, here is the readelf -wi for those two routines:
This should not be the problem of dwarf-analysis. It seems kernel-side (uprobe) problem.
Thanks a lot!
- Arnaldo

Signature · 4 lines

Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: [email protected]

Arnaldo Carvalho de Melo

author maintainer

2015-02-26 14:40 UTC #4 lore raw

Em Thu, Feb 26, 2015 at 01:57:42PM +0900, Masami Hiramatsu escreveu:

Quoted 11 lines

Quoted 9 lines · Arnaldo Carvalho de Melo
Em Wed, Feb 25, 2015 at 11:53:16AM +0900, Masami Hiramatsu escreveu:
Quoted 2 lines
(2015/02/25 3:49), Arnaldo Carvalho de Melo wrote:
Hmm, strange. Could you tell me the version of your kernel?
[root@ssdandy ~]# uname -r
3.10.0-210.el7.x86_64
Quoted 2 lines
It seems that the kernel newer than 3.14 supports uprobes with memory dereference (e.g. -32(%sp) )feature.

Quoted 6 lines

Quoted 2 lines
Right, that must be the case, will test, but then, would it be possible for the kernel, in such cases, return something line EOPNOTSUP?
Yeah, but for now, it is already supported in kernel. Of cause we can try to test feature with adding temporary event from perftools too.

Yeah, capability querying is done in several places in tools/perf/ already, like when checking if we have perf_event_attr enabled features, such as sample_id_all, etc.

Sometimes we can fallback to alternative mechanisms, sometimes we just need to provide a less cryptic message.

Quoted 7 lines

Quoted 7 lines
I will try to figure out a better error message on the tooling side, something like:
. Realize we're asking for memory dereference in uprobes
. If it fails with EINVAL, check the kernel version and say something
like:

Quoted 5 lines

Quoted 2 lines
Please upgrade your kernel to at least x.y.z to have access to feature FOO_BAR.
OK, it may be worth for users (I'm not sure RHEL can update their kernel to include that enhancement)

That may be possible, will check with Jiri if we can include that in a future backport.

Talking about these tools in conferences will make more people try the things mentioned, and as we talk about the latest and greatest, we need to try harder to handle error paths in a better way, providing less cryptic messages.

Rebuilding a newer kernel now to retry all this, thanks!

- Arnaldo

Masami Hiramatsu

2015-02-28 02:54 UTC #5 lore raw

PATCH 1/1 perf-probe: Warn if given uprobe event accesses memory on older kernel

Warn if given uprobe event accesses memory on older kernel. Until 3.14, uprobe event only supports accessing registers so this warns to upgrade kernel if uprobe-event returns -EINVAL and an argument of the event accesses memory ($stack, @+offset, and +|-offs() symtax).

With this patch (on 3.10.0-123.13.2.el7.x86_64);
-----

  # ./perf probe -x ./perf warn_uprobe_event_compat stack=-0\(%sp\)
  Added new event:
  Failed to write event: Invalid argument
  Please upgrade your kernel to at least 3.14 to have access to feature -0(%sp)
    Error: Failed to add events.
  -----

Signed-off-by Masami Hiramatsu <[email protected]>

---
 tools/perf/util/probe-event.c |   23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

tools/perf/util/probe-event.c +23 -0

index 7c0e765..1c570c2fa7 100644
@@ -2199,6 +2199,27 @@ static int get_new_event_name(char *buf, size_t len, const char *base,
 	return ret;
 }
 
+/* Warn if the current kernel's uprobe implementation is old */
+static void warn_uprobe_event_compat(struct probe_trace_event *tev)
+{
+	int i;
+	char *buf = synthesize_probe_trace_command(tev);
+
+	/* Old uprobe event doesn't support memory dereference */
+	if (!tev->uprobes || tev->nargs == 0 || !buf)
+		goto out;
+
+	for (i = 0; i < tev->nargs; i++)
+		if (strglobmatch(tev->args[i].value, "[$@+-]*")) {
+			pr_warning("Please upgrade your kernel to at least "
+				   "3.14 to have access to feature %s\n",
+				   tev->args[i].value);
+			break;
+		}
+out:
+	free(buf);
+}
+
 static int __add_probe_trace_events(struct perf_probe_event *pev,
 				     struct probe_trace_event *tevs,
 				     int ntevs, bool allow_suffix)

@@ -2295,6 +2316,8 @@ static int __add_probe_trace_events(struct perf_probe_event *pev,
 		 */
 		allow_suffix = true;
 	}
+	if (ret == -EINVAL && pev->uprobes)
+		warn_uprobe_event_compat(tev);
 
 	/* Note that it is possible to skip all events because of blacklist */
 	if (ret >= 0 && tev->event) {

Masami Hiramatsu

2015-02-28 03:21 UTC #6 lore raw

Re: [PATCH perf/core ] perf-probe: Warn if given uprobe event accesses memory on older kernel

Quoted 6 lines · Masami Hiramatsu

Warn if given uprobe event accesses memory on older kernel. Until 3.14, uprobe event only supports accessing registers so this warns to upgrade kernel if uprobe-event returns -EINVAL and an argument of the event accesses memory ($stack, @+offset, and +|-offs() symtax).

Quoted 9 lines

With this patch (on 3.10.0-123.13.2.el7.x86_64);
-----

  # ./perf probe -x ./perf warn_uprobe_event_compat stack=-0\(%sp\)
  Added new event:
  Failed to write event: Invalid argument
  Please upgrade your kernel to at least 3.14 to have access to feature -0(%sp)
    Error: Failed to add events.
  -----

Oops,

Thanks,

Quoted 55 lines

Signed-off-by Masami Hiramatsu <[email protected]>

---
 tools/perf/util/probe-event.c |   23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

tools/perf/util/probe-event.c +23 -1

index 7c0e765..1c570c2fa7 100644
@@ -2199,6 +2199,27 @@ static int get_new_event_name(char *buf, size_t len, const char *base,
 	return ret;
 }
 
+/* Warn if the current kernel's uprobe implementation is old */
+static void warn_uprobe_event_compat(struct probe_trace_event *tev)
+{
+	int i;
+	char *buf = synthesize_probe_trace_command(tev);
+
+	/* Old uprobe event doesn't support memory dereference */
+	if (!tev->uprobes || tev->nargs == 0 || !buf)
+		goto out;
+
+	for (i = 0; i < tev->nargs; i++)
+		if (strglobmatch(tev->args[i].value, "[$@+-]*")) {
+			pr_warning("Please upgrade your kernel to at least "
+				   "3.14 to have access to feature %s\n",
+				   tev->args[i].value);
+			break;
+		}
+out:
+	free(buf);
+}
+
 static int __add_probe_trace_events(struct perf_probe_event *pev,
 				     struct probe_trace_event *tevs,
 				     int ntevs, bool allow_suffix)

@@ -2295,6 +2316,8 @@ static int __add_probe_trace_events(struct perf_probe_event *pev,
 		 */
 		allow_suffix = true;
 	}
+	if (ret == -EINVAL && pev->uprobes)
+		warn_uprobe_event_compat(tev);
 
 	/* Note that it is possible to skip all events because of blacklist */
 	if (ret >= 0 && tev->event) {
 
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Signature · 4 lines

Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: [email protected]

Arnaldo Carvalho de Melo

author maintainer

2015-02-28 20:46 UTC #7 lore raw

Re: [PATCH perf/core ] perf-probe: Warn if given uprobe event accesses memory on older kernel

Em Sat, Feb 28, 2015 at 12:21:05PM +0900, Masami Hiramatsu escreveu:

Quoted 17 lines

Quoted 6 lines · Masami Hiramatsu
Warn if given uprobe event accesses memory on older kernel. Until 3.14, uprobe event only supports accessing registers so this warns to upgrade kernel if uprobe-event returns -EINVAL and an argument of the event accesses memory ($stack, @+offset, and +|-offs() symtax).
Quoted 9 lines
With this patch (on 3.10.0-123.13.2.el7.x86_64);
-----
  # ./perf probe -x ./perf warn_uprobe_event_compat stack=-0$%sp$
  Added new event:
  Failed to write event: Invalid argument
  Please upgrade your kernel to at least 3.14 to have access to feature -0(%sp)
    Error: Failed to add events.
  -----

Quoted 3 lines

Oops,
Suggested-by Arnaldo Carvalho de Melo <[email protected]>

:-)

Thanks for considering my suggestion and coming up with a patch so quickly!

I'll test it and merge,

- Arnaldo

Quoted 65 lines

Thanks,

Quoted 55 lines

Signed-off-by Masami Hiramatsu <[email protected]>

---
 tools/perf/util/probe-event.c |   23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

tools/perf/util/probe-event.c +23 -1

index 7c0e765..1c570c2fa7 100644
@@ -2199,6 +2199,27 @@ static int get_new_event_name(char *buf, size_t len, const char *base,
 	return ret;
 }
 
+/* Warn if the current kernel's uprobe implementation is old */
+static void warn_uprobe_event_compat(struct probe_trace_event *tev)
+{
+	int i;
+	char *buf = synthesize_probe_trace_command(tev);
+
+	/* Old uprobe event doesn't support memory dereference */
+	if (!tev->uprobes || tev->nargs == 0 || !buf)
+		goto out;
+
+	for (i = 0; i < tev->nargs; i++)
+		if (strglobmatch(tev->args[i].value, "[$@+-]*")) {
+			pr_warning("Please upgrade your kernel to at least "
+				   "3.14 to have access to feature %s\n",
+				   tev->args[i].value);
+			break;
+		}
+out:
+	free(buf);
+}
+
 static int __add_probe_trace_events(struct perf_probe_event *pev,
 				     struct probe_trace_event *tevs,
 				     int ntevs, bool allow_suffix)

@@ -2295,6 +2316,8 @@ static int __add_probe_trace_events(struct perf_probe_event *pev,
 		 */
 		allow_suffix = true;
 	}
+	if (ret == -EINVAL && pev->uprobes)
+		warn_uprobe_event_compat(tev);
 
 	/* Note that it is possible to skip all events because of blacklist */
 	if (ret >= 0 && tev->event) {
 
--

Signature · 4 lines

Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: [email protected]

tip-bot for Masami Hiramatsu

merge bot

2015-03-03 06:26 UTC #8 lore raw

[tip:perf/core] perf probe: Warn if given uprobe event accesses memory on older kernel

In reply to Masami Hiramatsu

perf probe: Warn if given uprobe event accesses memory on older kernel

Commit-ID:  79702f614187f652a814061e8f5875ddcc9e732d
Gitweb:     http://git.kernel.org/tip/79702f614187f652a814061e8f5875ddcc9e732d
Author:     Masami Hiramatsu <[email protected]>
AuthorDate: Sat, 28 Feb 2015 11:53:29 +0900
Committer:  Arnaldo Carvalho de Melo <[email protected]>
CommitDate: Mon, 2 Mar 2015 12:27:43 -0300

perf probe: Warn if given uprobe event accesses memory on older kernel

Warn if given uprobe event accesses memory on older kernel.

Until 3.14, uprobe event only supports accessing registers so this warns to upgrade kernel if uprobe-event returns -EINVAL and an argument of the event accesses memory ($stack, @+offset, and +|-offs() symtax).

With this patch (on 3.10.0-123.13.2.el7.x86_64);
-----

  # ./perf probe -x ./perf warn_uprobe_event_compat stack=-0\(%sp\)
  Added new event:
  Failed to write event: Invalid argument
  Please upgrade your kernel to at least 3.14 to have access to feature -0(%sp)
    Error: Failed to add events.
  -----

Signed-off-by Masami Hiramatsu <[email protected]>

Cc David Ahern <[email protected]>

Cc Jiri Olsa <[email protected]>

Link http://lkml.kernel.org/r/[email protected] open here

Signed-off-by Arnaldo Carvalho de Melo <[email protected]>

---
 tools/perf/util/probe-event.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

tools/perf/util/probe-event.c +23 -0

index 7c0e765..1c570c2 100644
@@ -2199,6 +2199,27 @@ static int get_new_event_name(char *buf, size_t len, const char *base,
 	return ret;
 }
 
+/* Warn if the current kernel's uprobe implementation is old */
+static void warn_uprobe_event_compat(struct probe_trace_event *tev)
+{
+	int i;
+	char *buf = synthesize_probe_trace_command(tev);
+
+	/* Old uprobe event doesn't support memory dereference */
+	if (!tev->uprobes || tev->nargs == 0 || !buf)
+		goto out;
+
+	for (i = 0; i < tev->nargs; i++)
+		if (strglobmatch(tev->args[i].value, "[$@+-]*")) {
+			pr_warning("Please upgrade your kernel to at least "
+				   "3.14 to have access to feature %s\n",
+				   tev->args[i].value);
+			break;
+		}
+out:
+	free(buf);
+}
+
 static int __add_probe_trace_events(struct perf_probe_event *pev,
 				     struct probe_trace_event *tevs,
 				     int ntevs, bool allow_suffix)

@@ -2295,6 +2316,8 @@ static int __add_probe_trace_events(struct perf_probe_event *pev,
 		 */
 		allow_suffix = true;
 	}
+	if (ret == -EINVAL && pev->uprobes)
+		warn_uprobe_event_compat(tev);
 
 	/* Note that it is possible to skip all events because of blacklist */
 	if (ret >= 0 && tev->event) {