[lttng-dev] Possibilities to customize lttng tracepoints in kernel space

[lttng-dev] Possibilities to customize lttng tracepoints in kernel space

[Serica via lttng-dev]

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Hi,


I send this email to consult that whether it is possible to customize lttng tracepoints in kernel space. I have learnt that lttng leverages linux tracepoint to collect audit logs like system calls. Also, I have found that user can define their customized tracepoints in user space by using lttng-ust so that they can trace their user applications.


Is it possible for lttng users to customize the existing tracepoints in kernel space? For example, after the system call sys_clone, or read, called and then collected by lttng, I want to process some data ( e.g., the return value of the syscall ), and place the result in a new field in the audit log ( or using another approach, by emitting a new type of event in the audit log ), and later when parsed by babeltrace, we can see the newly-added field or event in the parsed result.


Looking forward to your reply.


Best wishes,


Serica

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Re: [lttng-dev] Possibilities to customize lttng tracepoints in kernel space

[Mathieu Desnoyers via lttng-dev]

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----- On Dec 16, 2020, at 4:19 AM, lttng-dev <lttng-dev@lists.lttng.org> wrote: 

> Hi,

> I send this email to consult that whether it is possible to customize lttng
> tracepoints in kernel space. I have learnt that lttng leverages linux
> tracepoint to collect audit logs like system calls. Also, I have found that
> user can define their customized tracepoints in user space by using lttng-ust
> so that they can trace their user applications.

> Is it possible for lttng users to customize the existing tracepoints in kernel
> space? For example, after the system call sys_clone, or read, called and then
> collected by lttng, I want to process some data ( e.g., the return value of the
> syscall ), and place the result in a new field in the audit log ( or using
> another approach, by emitting a new type of event in the audit log ), and later
> when parsed by babeltrace, we can see the newly-added field or event in the
> parsed result.

> Looking forward to your reply.

Hi, 

You will want to start by having a look at this section of the LTTng documentation: https://lttng.org/docs/v2.12/#doc-instrumenting-linux-kernel 

You can indeed modify lttng-modules to change the fields gathered by the system call tracing facility (see include/instrumentation/syscalls/README section (3)). 
Those changes will be reflected in the resulting trace data. 

Thanks, 

Mathieu 

> Best wishes,

> Serica

> _______________________________________________
> lttng-dev mailing list
> lttng-dev@lists.lttng.org
> https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev

-- 
Mathieu Desnoyers 
EfficiOS Inc. 
http://www.efficios.com 

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[lttng-dev] =?gb18030?b?u9i4tKO6ICBQb3NzaWJpbGl0aWVzIHRvIGN1c3Rv?= =?gb18030?q?mize_lttng_tracepoints_in_kernel_space?=

[Serica via lttng-dev]

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Hi,


Thanks for your reply. Some other stuff. I found that lttng is working on container awareness in this slides: https://archive.fosdem.org/2019/schedule/event/containers_lttng/attachments/slides/3419/export/events/attachments/containers_lttng/slides/3419/lttng_containers_fosdem19.pdf


On page #13, there is a command:  lttng add-context -k -t procname -t pid -t vpid -t tid -t vtid -t pid_ns, where pid_ns and other namespace identifiers are very useful for tracing containers. However, it seems like that lttng of current version doesn't support adding context pid_ns(Error: Unknown context type pid_ns). Do you know how to enable these features?


Thanks a lot.
Btw, have a nice holiday!


Serica


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Ö÷Ìâ:&nbsp;Re: [lttng-dev] Possibilities to customize lttng tracepoints in kernel space







----- On Dec 16, 2020, at 4:19 AM, lttng-dev <lttng-dev@lists.lttng.org&gt; wrote:

Hi,

I send this email to consult that whether it is possible to customize lttng tracepoints in kernel space. I have learnt that lttng leverages linux tracepoint to collect audit logs like system calls. Also, I have found that user can define their customized tracepoints in user space by using lttng-ust so that they can trace their user applications.

Is it possible for lttng users to customize the existing tracepoints in kernel space? For example, after the system call sys_clone, or read, called and then collected by lttng, I want to process some data ( e.g., the return value of the syscall ), and place the result in a new field in the audit log ( or using another approach, by emitting a new type of event in the audit log ), and later when parsed by babeltrace, we can see the newly-added field or event in the parsed result.

Looking forward to your reply.


Hi,



You will want to start by having a look at this section of the LTTng documentation: https://lttng.org/docs/v2.12/#doc-instrumenting-linux-kernel



You can indeed modify lttng-modules to change the fields gathered by the system call tracing facility (see include/instrumentation/syscalls/README section (3)).
Those changes will be reflected in the resulting trace data.



Thanks,



Mathieu






Best wishes,

Serica

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-- 

Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com

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